| 1. |
- A. B. Marçal, L., et al.
(författare)
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Spatially resolved structural and chemical properties of the white layer in machined Inconel 718 super alloy
- 2024
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Ingår i: Materials and Design. - 0264-1275. ; 239
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Tidskriftsartikel (refereegranskat)abstract
- Inconel 718 is one type of nickel-based alloy used for a large range of applications, including gas turbines and aeroengines components. Although mechanical and thermodynamic properties of this material have been deeply studied in the past years, a method able to investigate local properties of the thin white layer formed on the alloy surface after machining remains challenging. Here, a 90 nm X-ray beam is used to probe the local strain, crystal orientation, and chemical composition of grains in the white layer. Data reveals mosaicity induced by the tool during machining. The high spatial resolution, combined with crystal lattice sensitivity, shows that the average grain size is around 30 nm throughout the white layer, while the strain is anisotropic nearest to the surface. Results provide new insights on the basic properties of the white layer in super alloys, revealing important information about the impact of finish machining which might help to explain fatigue and cracking formation on these materials during their usage phase.
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| 2. |
- Balpande, A. R., et al.
(författare)
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Excellent specific strength-ductility synergy in novel complex concentrated alloy after suction casting
- 2024
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Ingår i: Materials and Design. - 1873-4197 .- 0264-1275. ; 242
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight alloys are known to improve the fuel efficiency of the structural components due to high strength-to-weight ratio, however, they lack formability at room temperature. This major limitation of poor formability is most of the time overcome by post-fabrication processing and treatments thereby increasing their cost exponentially. We present a novel Ti50V16Zr16Nb10Al5Mo3 (all in at. %) complex concentrated alloy (Ti-CCA) designed based on the combination of valence electron concentration theory and the high entropy approach. The optimal selection of constituent elements has led to a density of 5.63 gm/cc for Ti-CCA after suction casting (SC). SC Ti-CCA displayed exceptional room temperature strength (UTS ∼ 1.25 GPa) and ductility (ε ∼ 35 %) with a yield strength (YS) of ∼ 1.1 GPa (Specific YS = 191 MPa/gm/cc) without any post-processing treatments. The exceptional YS in Ti-CCA is attributed to hetero grain size microstructure, whereas enormous strength-ductility synergy is due to the concurrent occurrence of slip and deformation band formation in the early stages of deformation followed by prolonged necking event due to delayed void nucleation and growth. The proposed philosophy of Ti-CCA design overcomes the conventional notion of strength-ductility trade-off in such alloy systems by retaining their inherent characteristics.
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| 3. |
- Bhattacharjee, Rahul, et al.
(författare)
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Synergy of nanocarriers with CRISPR-Cas9 in an emerging technology platform for biomedical appliances : Current insights and perspectives
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- Genetic editing technologies have emerged as a potential therapeutic tool in various biomedical fields owing to their applications against cancer, neurological diseases, diabetes, autoimmune disorder, muscu-lar dystrophy, bacterial infections (AMR), and cardiovascular diseases. CRISPR is one such valuable genetic editing tool with extensive therapeutic appliances but with a major challenge in terms of deliv-ery. Herein, we have strived to exploit a synergy of nanocarriers and CRISPR against the aforementioned diseases for their medical applications and explicated their clinical significance including the enhanced delivery via endosomal escape and environmental factors such as light, pH, and stimuli. In addition to highlighting the delivery strategies of nano-carriers for CRISPR and their characterization, we have expounded on the reliant factor of the CRISPR-Cas Complex.
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| 4. |
- Blixt, Kevin, et al.
(författare)
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Grain boundary and particle interaction: Enveloping and pass-through mechanisms studied by 3D phase field crystal simulations
- 2022
-
Ingår i: Materials & Design. - : Elsevier BV. - 0261-3069 .- 0264-1275. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- Grain boundary interaction with second-phase particles having different degrees of coherency is investigated using the phase field crystal (PFC) method. Both the enveloping and pass-through mechanisms are studied with regards to grain boundary pressure, passage time and interface evolution. It is found that coherent particles exert a stronger retardation effect on grain boundaries compared to incoherent particles, with regards to both pressure and time, but also that this benefit is limited to a small range of misfit values. The simulations also show that the mobility is not a constant during particle passage, as commonly assumed, which means that grain boundary pressure cannot easily be extracted from the grain boundary velocity. Furthermore, the complex evolution of the pass-through mechanism and the transient behavior for intermediate coherencies is also investigated. The highest drag force is found to occur at the switching point between enveloping and pass-through. As part of the study, the advantages of using PFC for this type of analyses are also highlighted.
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| 5. |
- Brandau, Benedikt, et al.
(författare)
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Absorbance study of powder conditions for laser additive manufacturing
- 2022
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 216
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Tidskriftsartikel (refereegranskat)abstract
- Absorbance is often used for simulations or validation of process parameters for powder-based laser materials processing. In this work, the absorbance of 39 metal powders for additive manufacturing is determined at 20 laser wavelengths. Different grain sizes and aging states for: steels, aluminum alloys, titanium alloys, Nitinol, high entropy alloy, chromium, copper, brass and iron ore were analyzed. For this purpose, the absorbance spectrum of the powders was determined via a dual-beam spectrometer in the range of λ = 330 - 1560 nm. At the laser wavelengths of λ = 450 nm, 633 nm and 650 nm, the absorbance averaged over all materials was found to increase by a factor of 2.4 up to 3.3 compared to the usual wavelength of λ = 1070 nm, with minimal variations in absorbance between materials. In the investigation of the aged or used powders, a loss of absorbance was detectable. Almost no changes from the point of view of processing aged and new AlSi10Mg powders, is expected for laser sources with λ = 450 nm. The resulting measurements provide a good basis for process parameters for a variety of laser wavelengths and materials, as well as a data set for improved absorbance simulations.
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| 6. |
- Buck, Dietrich, et al.
(författare)
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Moisture- and mould-resistance : modelling of edge-sealed cross-laminated timber using multi-modal assessment leveraged by X-ray computed tomography
- 2023
-
Ingår i: Materials and Design. - 0264-1275. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. X-ray computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.
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| 7. |
- Buck, Dietrich, 1990-, et al.
(författare)
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Moisture- and mould-resistance: multi-modal modelling leveraging X-ray tomography in edge-sealed cross-laminated timber
- 2023
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. Multi-modal assessment leveraged by computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.
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| 8. |
- Cabo Rios, Alberto, 1990, et al.
(författare)
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Ex-situ characterization and simulation of density fluctuations evolution during sintering of binder jetted 316L
- 2024
-
Ingår i: Materials and Design. - 1873-4197 .- 0264-1275. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Efficient density evolution during sintering of the as-printed component is vital to reach full densification and required properties of binder jet (BJT) components. However, due to the high porosity and brittle nature of the green compact, analysis of the microstructure development during sintering is very difficult, resulting in lack of understanding of the densification process. Density development from green state (57 ± 1.6 %) up to full density (99 ± 0.3 %) was characterized by high-resolution synchrotron X-Ray computed tomography (SXCT) on BJT 316L samples from ex-situ interrupted sintering tests. Periodicity of density fluctuations along the building direction was revealed for the first time and was related to the layer thickness of ∼ 42 µm during printing that decreased down to ∼ 33 µm during sintering. Sintering simulations, utilizing a continuum sintering model developed for BJT, allowed to replicate the density evolution during sintering with a mean error of 2 % and its fluctuation evolution from green (1.66 %) to sintered (0.56 %) state. Additionally, simulation of extreme particle size segregation (1 µm to 130 µm) suggested that non-optimized printing could lead to undesirable density fluctuation amplitude rapid increase (∼10 %) during sintering. This might trigger the nucleation of defects (e.g., layer delamination, cracking, or excessive residual porosity) during the sintering process.
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| 9. |
- Čapek, J., et al.
(författare)
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Influence of laser powder bed fusion scanning pattern on residual stress and microstructure of alloy 718
- 2022
-
Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 221
-
Tidskriftsartikel (refereegranskat)abstract
- A comprehensive investigation is undertaken on the effect of laser scanning pattern on the microstructure of cylindrical samples made of Alloy 718 processed by Laser Powder Bed Fusion. It is observed that the common alternate direction scanning of the laser results in a more homogeneous microstructure than the less common concentric line scans where significant microstructural heterogeneities are seen between the edges and the center of the sample. The investigation focuses on the precipitation, crystallographic texture, grain size, grain morphology and residual stresses utilizing synchrotron X-ray diffraction, neutron diffraction and electron microscopy. The heterogeneous microstructure of the sample processed with the concentric laser pattern influences the chemical composition of the matrix, which alters the reference “strain free” interplanar spacing used for evaluating the residual strain. The investigation underlines the significance of the processing parameters on the homogeneity of the microstructure and the effect of the chemical variations on the determination of residual stresses in materials such as Alloy 718, where strong local chemical variations occur because of different types and extent of precipitation. © 2022
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| 10. |
- Chen, Feng, 1987-, et al.
(författare)
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A state-of-the-art review of intrinsic and enhanced electrical properties of asphalt materials: theories, analyses and applications
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 195, s. 109067-
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Tidskriftsartikel (refereegranskat)abstract
- In pavement engineering, a variety of promising application technologies are found relying on a thorough understanding of the intrinsic (mainly dielectric) electrical properties of asphalt binder and concrete materials. Meanwhile, the electrical properties of asphalt materials can be further enhanced by introducing conductive additives into and it has been brought to light that, the electrically conductive asphalt is becoming an emerging subject of interest that caters to the concept of a multifunctional pavement future. In context of these, this paper presents a holistic overview of the intrinsic and enhanced electrical properties of asphalt materials, including the theoretical analyses, as well as the corresponding applications in the practice. From such a state-of-the-art review, it is worth noting that: i) an improved understanding of asphalt material has been achieved by an in-depth examination of its electrical properties; ii) the increased significance of the research domain as a whole and, the key importance of multidisciplinary collaborations for future successes, have been indicated.
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| 11. |
- Choi, Young Won, et al.
(författare)
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Predicting the stacking fault energy of austenitic Fe-Mn-Al (Si) alloys
- 2020
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 187
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum and silicon are common alloying elements for tuning the stacking fault energy (SFE) of high Mn steels. Today the theoretical investigations on the Fe-Mn-Al/Si systems using Density Functional Theory (DFT) are very scarce. In the present study, we employ a state-of-the-art longitudinal spin fluctuations (LSFs) model in combination with DFT for describing the magnetic effects in Fe-Mn based alloys at finite temperature. We find that the traditional DFT-floating spin results fail to explain the experimental trends. However, the DFT-LSFs approach properly captures the Al-induced increase and Si-induced decrease of the SFE of the base alloy in line with the room-temperature observations. This finding highlights the importance of LSFs in describing the Al/Si effects on the SEE of Fe-Mn based alloys. We point out that the effects of the non-magnetic Al and Si additions on the SEE are in fact determined by the magnetic state of the host matrix. In addition, we estimate the role of carbon addition in the alloying effects of Al and Si. The present results provide a convenient pathway to access the important mechanical parameters for designing advanced high-strength alloys.
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| 12. |
- Croné, Philip, et al.
(författare)
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Continuum plasticity modelling of work hardening for precipitation-hardened martensitic steel guided by atom probe tomography
- 2022
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 215
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical flow stress model, based on isotropic strain gradient plasticity theory, for precipitation hardened materials, is proposed and evaluated against tensile data on a 15 wt% Cr - 5 wt% Ni (15-5) PH stainless steel. The 15-5 PH material was aged at 500 °C for 1 h, 2 h, 5 h and 50 h to obtain a wide range of precipitate sizes. Detailed characterisation of precipitates was obtained using atom probe tomography (APT). A second material, a 15-5 stainless steel without added Cu was heat treated to obtain a similar matrix microstructure as in the 15-5 PH, but without Cu precipitates. Tensile testing revealed that the heat treated 15-5 PH material covered the full range from under- to overaged conditions. The analytical model, which accounts for stress reducing effects of plastic relaxation around particles, manages to capture the experimental data in a very satisfying manner using only a total of three tunable parameters. It is believed that the proposed model can offer an alternative to the much more commonly used work hardening models based on the internal variable approach.
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| 13. |
- Cui, Luqing, et al.
(författare)
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Revealing Relationships between Microstructure and Hardening Nature of Additively Manufactured 316L Stainless Steel
- 2021
-
Ingår i: Materials & Design. - : Elsevier. - 0261-3069 .- 0264-1275. ; 198
-
Tidskriftsartikel (refereegranskat)abstract
- Relationships between microstructures and hardening nature of laser powder bed fused (L-PBF) 316 L stainless steel have been studied. Using integrated experimental efforts and calculations, the evolution of microstructure entities such as dislocation density, organization, cellular structure and recrystallization behaviors were characterized as a function of heat treatments. Furthermore, the evolution of dislocation-type, namely the geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs), and their impacts on the hardness variation during annealing treatments for L-PBF alloy were experimentally investigated. The GND and SSD densities were statistically measured utilizing the Hough-based EBSD method and Taylor's hardening model. With the progress of recovery, the GNDs migrate from cellular walls to more energetically-favourable regions, resulting in the higher concentration of GNDs along subgrain boundaries. The SSD density decreases faster than the GND density during heat treatments, because the SSD density is more sensitive to the release of thermal distortions formed in printing. In all annealing conditions, the dislocations contribute to more than 50% of the hardness, and over 85.8% of the total dislocations are GNDs, while changes of other strengthening mechanism contributions are negligible, which draws a conclusion that the hardness of the present L-PBF alloy is governed predominantly by GNDs.
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| 14. |
- Da Silva, Adrien, et al.
(författare)
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Additive Manufacturing by laser-assisted drop deposition from a metal wire
- 2021
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- The subject of Additive Manufacturing includes numerous techniques, some of which have reached very high levels of development and are now used industrially. Other techniques such as Micro Droplet Deposition Manufacture are under development and present different manufacturing possibilities, but are employed only for low melting temperature metals. In this paper, the possibility of using a laser-based drop deposition technique for stainless-steel wire is investigated. This technique is expected to be a more flexible alternative to Laser Metal Wire Deposition. Laser Droplet Generation experiments were carried out in an attempt to accurately detach steel drops towards a desired position. High-speed imaging was used to observe drop generation and measure the direction of detachment of the drops. Two drop detachment techniques were investigated and the physical phenomena leading to the drop detachment are explained, wherein the drop weight, the surface tension and the recoil pressure play a major role. Optimised parameters for accurate single drop detachment were identified and then used to build multi-drop tracks. Tracks with an even geometry were produced, where the microstructure was influenced by the numerous drop depositions. The tracks showed a considerably higher hardness than the base wire, exhibiting a relatively homogeneous macro-hardness with a localised softening effect at the interfaces between drops.
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| 15. |
- Da Silva, Adrien, et al.
(författare)
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Influence of aluminium powder aging on Directed Energy deposition
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 218
-
Tidskriftsartikel (refereegranskat)abstract
- The use of aluminium alloys for Additive Manufacturing is of high interest for advanced geometries and lightweight applications. In Directed Energy Deposition, a powder stock is processed with a laser beam, which offers a high process flexibility. However, aging of the powder feedstock during storage or after recycling remains fundamentally challenging for aluminium alloys because of their sensitivity to oxida-tion and porosity. In order to investigate these effects, AlSi10Mg powder batches were aged in different conditions and processed by Directed Energy Deposition. The results showed that powder aging does not significantly change the particle size or morphology, but it introduces more oxygen and hydrogen in the powder. The oxidation of the particles reduces the laser beam absorbance of the powder and increases wetting of the melt pool, which affects the track geometry. A 3.5 to 4.2 times higher porosity was observed in the material deposited from aged powder, which are most likely hydrogen pores causedby the increased hydrogen content in the aged powder. The tensile properties of the parts built with aged powder showed 19.0% lower yield strength, 14.2% lower ultimate strength and 99.2% higher elongation, which are most likely the results of the coarser microstructure and increased porosity.
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| 16. |
- Dippo, Olivia F., et al.
(författare)
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Color and pseudogap tunability in multicomponent carbonitrides
- 2022
-
Ingår i: Materials & design. - : Elsevier Science Ltd. - 0264-1275 .- 1873-4197. ; 217
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Tidskriftsartikel (refereegranskat)abstract
- The design and tailoring of material color for both aesthetic and functionality is an ongoing topic of materials science and engineering research. In this work, a method is developed to tune and predict color and pseudogap energy of any compositional variation of B1-rocksalt structured Group 4 and 5 transition metal carbonitride. Optical properties of bulk multicomponent transition metal carbonitrides were characterized using reflectivity spectra. Optical pseudogap energies were extrapolated using the Tauc method, and color appearance was quantified in the Commission Internationale de lEclairage (CIE) Lightness*Chroma*hue (L*C*h) color space. Variations of color parameters chroma and hue were analyzed in terms of pseudogap energies and electronic band structures. Compositional variations were utilized to predictably tune aspects of the electronic structure, including the specificity of electronic transitions and the energy at which they occur, to tailor the materials color appearance and facilitate the formation of new carbonitride colors.
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| 17. |
- Dongale, T. D., et al.
(författare)
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Bifunctional nanoparticulated nickel ferrite thin films : Resistive memory and aqueous battery applications
- 2021
-
Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 201
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, excellent non-volatile memory and aqueous battery properties of solution-processable nickel ferrite (NFO) nanomaterial were demonstrated. In the case of non-volatile memory property, the device operates on ±2 V resistive switching voltage and shows double valued charge-magnetic flux characteristics. Excellent endurance (103) and retention (104 s) non-volatile memory properties with a good memory window (103) were observed for NFO memristive device. The conduction and resistive switching mechanisms based on experimental data are provided. Furthermore, the present work investigates the electrochemical performance of the NFO thin film electrode in the different electrolytes (viz. Na2SO4, Li2SO4, and Na2SO4: Li2SO4). It was revealed that the NFO thin film shows improved electrochemical performance in Na2SO4 electrolyte with a high specific capacity of 18.56 mAh/g at 1 mA/cm2 current density. The electrochemical impedance spectroscopic results reveal that the NFO thin film electrode shows low series and charge transfer resistance values for Na2SO4 electrolyte than other electrolytes. The diffusion coefficient of different ions (DNa+, DLi+ and DNa+:Li+) were found to be 9.975 × 10−10 cm2 s−1, 3.292 × 10−11 cm2 s−1, 2 × 10−10 cm2 s−1, respectively. A high diffusion coefficient was found for Na+ ions, indicating rapid Na+ transport with NFO thin-film electrodes © 2021 The Authors
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| 18. |
- Dorri, Samira, et al.
(författare)
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Effects of stoichiometry and individual layer thickness ratio on the quality of epitaxial CrBx/TiBy superlattice thin films
- 2023
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Studies of single crystal artificial superlattices (SLs) of transition-metal (TM) diborides, which is instru- mental to understand hardening mechanisms at nanoscale, is lacking. Here, CrBx/TiBy (0001) diboride SLs [x,y E 1.7-3.3] are grown epitaxially on Al2O3(0001) substrates by direct-current magnetron sputter epitaxy. Growth conditions for obtaining well-defined SLs with good interface quality are found at 4 mTorr Ar pressure and 600 degrees C. 1 -mu m-thick SL films deposited with modulation periods A between 1 and 10 nm, and A=6 nm SLs with TiBy-to-A layer thickness ratios F ranging from 0.2 to 0.8 are studied. SLs with A=6 nm and F in the range of 0.2-0.4, with a near stoichiometric B/TM ratio, exhibit the high- est structural quality. The effects of F and stoichiometries (B/TM ratio) on the distribution of B in the SL structures are discussed. By increasing the relative thickness of TiBy, the crystalline quality of SLs starts to deteriorate due to B segregation in over-stoichiometric TiBy, resulting in narrow epitaxial SL columnar growth with structurally-distorted B-rich boundaries. Moreover, increasing the relative thickness of under-stoichiometric CrBx enhances the SL quality and hinders formation of B-rich boundaries. The SLs are found to exhibit hardness values in the range of 29-34 GPa.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 19. |
- Ekström, Erik, et al.
(författare)
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Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica
- 2023
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 229
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Tidskriftsartikel (refereegranskat)abstract
- Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three in-plane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductivity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control.
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| 20. |
- Elbashir, Sana, 1984-, et al.
(författare)
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Thermodynamic modelling assisted three-stage solid state synthesis of high purity β-Ca3(PO4)2
- 2024
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- A three-stage solid state synthesis assisted by thermodynamic modelling was developed to prepare highly pure (>99 %) beta tricalcium phosphate (β-TCP) powder. The optimal synthesis temperature was experimentally determined to be 1000 °C in good agreement with the theoretical calculations. The synthesis design described here has substantially improved the product quality and eliminated the presence of secondary phosphate phases compared to one- and two-stage methods investigated in this work. A comprehensive characterization of the material's structural, vibrational, and morphological characteristics was conducted. Rietveld refinement of the X-ray diffraction data confirmed the high purity of the samples. The crystal structure of the prepared β-TCP was determined and the refined unit cell parameters agreed well with the reference values. From infrared and Raman spectral analyses, the characteristics of β-TCP were observed and discussed in details. Furthermore, the morphology and elemental composition of the products were examined and found to be homogenous and impurity free. The reproducibility of the material was scrutinized and showed no significant data variations. Using our three-stage synthesis method, it is possible to produce β-TCP powder of high purity with consistent repeatability.
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| 21. |
- Ericsson, A., et al.
(författare)
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Transient nucleation in selective laser melting of Zr-based bulk metallic glass
- 2020
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- The crystallization rate during selective laser melting (SLM) of bulk metallic glasses (BMG) is a critical factor in maintaining the material's amorphous structure. To increase the understanding of the interplay between the SLM process and the crystallization behavior of BMGs, a numerical model based on the classical nucleation theory has been developed that accounts for the rapid temperature changes associated with SLM. The model is applied to SLM of a Zr-based BMG and it is shown that the transient effects, accounted for by the model, reduce the nucleation rate by up to 15 orders of magnitude below the steady-state nucleation rate on cooling, resulting in less nuclei during the build process. The capability of the proposed modelling approach is demonstrated by comparing the resulting crystalline volume fraction to experimental findings. The agreement between model predictions and the experimental results clearly suggests that transient nucleation effects must be accounted for when considering the crystallization rate during SLM processing of BMGs.
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| 22. |
- Feng, Shuo, et al.
(författare)
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Predicting laser powder bed fusion defects through in-process monitoring data and machine learning
- 2022
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- Industry application of additive manufacturing demands strict in-process quality control procedures and high product quality. Feedback loop control is a reasonable solution and a necessary tool. This paper demonstrated our preliminary work on the laser powder-bed fusion feedback loop: predict local porosity through in-process monitoring images and machine learning. 3D models were rebuilt from in-situ optical tomography monitoring images and post-build X-ray CT images. They were registered to the original CAD. Dataset for machine learning was assembled from those registered 3D models. The trained machine learning model can precisely predict local porosity caused by lack of fusion and keyhole with multi-layer monitoring images. It also indicates the optimal processing window. It is impossible to be sure about the occurrence of defects in a layer based only on the abnormality of a single layer, and vice versa. Defects in a layer can be caused by improper parameters or anomalies in current layer or subsequent layers; defects in one layer can also be eliminated by proper parameters in the following layers. The work laid the basis for the next step feedback loop control of pore defect.
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| 23. |
- Fiegl, Tobias, et al.
(författare)
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Effect of AlSi10Mg0.4 long-term reused powder in PBF-LB/M on the mechanical properties
- 2021
-
Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Laser-based powder bed fusion (PBF-LB/M) is a well-established additive manufacturing (AM) process capable of producing high quality parts with excellent mechanical properties. Industrial applications of additively manufactured parts require the usage of fresh powder which makes the process expensive, especially in case of AM machines with enlarged build envelopes. Processing long-term reused powder fits to economic yields with the drawback of increased porosity and incorporated oxides. In this study, a detailed analysis of components made of virgin and long-term reused AlSi10Mg0.4 powder is provided. The experiments reveal that process parameters qualified for the virgin powder are not working offhand for the reused powder, as an increase of porosity from less than 1 % up to 3 % and a decline of tensile strength as well as yield strength of about 15 % are observed. The results indicate that powder degradation, which is based on the formation of hydroxides and oxides, has a significant impact on as-built microstructure as well as mechanical properties of additively manufactured parts. The amount of hydrogen and oxygen is measured for different powder conditions and the powder ageing process of AlSi10Mg0.4 is discussed in detail.
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| 24. |
- Fritze, Stefan, et al.
(författare)
-
Influence of Carbon on Microstructure and Mechanical Properties of Magnetron Sputtered TaW Coatings
- 2020
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 196
-
Tidskriftsartikel (refereegranskat)abstract
- (Ta,W) and (Ta,W):C films with-5 at.% C were deposited by non-reactive magnetron sputtering. They crystallised in a bcc structure with a columnar microstructure. The solid solubility of C in (Ta,W) alloys is very low, which suggests that the (Ta,W):C films are supersaturated with respect to carbon. This was confirmed by diffraction and atom probe tomography (APT) showing that carbon is in the as-deposited (Ta,W):C films homogeneously distributed in the structure without carbide formation or carbon segregation. Annealing at 900 degrees C for 2 h showed no significant column coarsening but an increased defect density at the column boundaries in the (Ta,W):C films. The films were still supersaturated with respect to carbon but APT showed a partial segregation of carbon presumably to defect-rich column boundaries after annealing. The (Ta,W) films exhibited a hardness of-12-13 GPa. Alloying with carbon increased the hardness to-17 GPa. The hardness increased to-19 GPa for the annealed (Ta,W):C films. This annealing-induced hardness increase was explained by C segregation to the more defect-rich column boundaries, which restricts dislocation movements. (Ta,W):C coatings may be a potential alternative to ceramic coatings, worth exploring further by small scale mechanical testing to investigate if these materials are ductile.
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| 25. |
- Fritze, Stefan, et al.
(författare)
-
Magnetron sputtering of carbon supersaturated tungsten films-A chemical approach to increase strength
- 2021
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 208
-
Tidskriftsartikel (refereegranskat)abstract
- Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to-4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from-133 nm for W to-20 nm for the film containing-4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is-13 GPa hard, while the W:C films achieve a peak hardness of-24 GPa. The W:C films are-11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from-3.8 to-8.3 GPa and no brittle fracture was observed.
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| 26. |
- Gangaprasad Rao, Smita, et al.
(författare)
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Thin film growth and mechanical properties of CrFeCoNi/TiNbZrTa multilayers
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- Multilayers of high entropy alloys (HEA) are picking up interest due to the possibility of altering material properties by tuning crystallinity, thickness, and interfaces of the layers. This study investigates the growth mechanism and mechanical properties of CrFeCoNi/TiNbZrTa multilayers grown by magnetron sputtering. Multilayers of bilayer thickness (Λ) from 5 nm to 50 nm were grown on Si(1 0 0) substrates. Images taken by transmission electron microscopy and energy-dispersive X-ray spectroscopy mapping revealed that the layers were well defined with no occurrence of elemental mixing. Multilayers with Λ < 20 nm exhibited an amorphous structure. As Λ increased, the CrFeCoNi layer displayed a higher crystallinity in comparison to the amorphous TiNbZrTa layer. The mechanical properties were influenced by the crystallinity of the layers and stresses in the film. The film with Λ = 20 nm had the highest hardness of approximately 12.5 GPa owing grain refinement of the CrFeCoNi layer. An increase of Λ ≥ 30 nm resulted in a drop in the hardness due to the increase in crystal domains of the CrFeCoNi layer. Micropillar compression induced shear in the material rather than fracture, along with elemental intermixing in the core of the deformed region of the compressed micropillar.
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| 27. |
- Gao, Ying, et al.
(författare)
-
Scalable hierarchical wood/ZnO nanohybrids for efficient mechanical energy conversion
- 2023
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 226
-
Tidskriftsartikel (refereegranskat)abstract
- Owing to the hierarchical structure, easy multi-functionalization and favorable mechanical properties, wood could harvest electricity from mechanical energy through piezoelectric behavior. In this work, a scalable method to synthesize wood/ZnO composite with multilayered ZnO morphologies is reported for efficient mechanical energy conversion. The synthesis includes charged wood template fabrication, precursor infiltration, and ZnO hydrothermal growth, resulting in controlled ZnO morphologies and distributions while maintaining the hierarchical structure of the wood. Stereo-digital image correlation (stereo-DIC) investigated the relationship between deformation and piezoelectric performance, which revealed the homogeneous distribution of multilayered ZnO enhance piezoelectric performance. The output voltage of wood/ZnO was 1.5 V under periodic mechanical compression (8–10 N) for 300 cycles, while the output current was 2.91 nA. The scalable synthesis strategy and piezoelectric performance are significant for the design of advanced wood nanocomposites for sustainable and efficient energy conversion systems.
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| 28. |
- Glechner, T., et al.
(författare)
-
Influence of the non-metal species on the oxidation kinetics of Hf, HfN, HfC, and HfB2 coatings
- 2021
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 211
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of the non-metal species on the oxidation resistance of transition metal ceramic based thin films is still unclear. For this purpose, we thoroughly investigated the oxide scale formation of a metal (Hf), carbide (HFC0.96), nitride (HfB1.5), and boride (HfB2.3) coating grown by physical vapor deposition. The non-metal species decisively affect the onset temperature of oxidation, ranging between 550 degrees C for HfC0.96 to 840 degrees C for HfN1.5. HfB2.3 and HfN1.5 obtain the slowest oxide scale kinetic following a parabolic law with k(p) values of 4.97.10(-10) and 5.66.10(-11) kg(2) m(-4) s(-1) at 840 degrees C, respectively. A characteristic feature for the oxide scale on Hf coatings, is a columnar morphology and a substantial oxygen inward diffusion. HfC0.96 reveals an ineffective oxycarbide based scale, whereas HfN(1.5 )features a scale with globular HfO2 grains. HfB(2.3 )exhibits a layered scale with a porous boron rich region on top, followed by a highly dense and crystalline HfO2 beneath. Furthermore, HfB(2.3 )presents a hardness of 47.7 +/- 2.7 GPa next to an exceptional low inward diffusion of oxygen during oxidation. This study showcases the strong influence of the non-metallic bonding partner despite the same metallic basis, as well as the huge potential for HfB2 based coatings also for oxidative environments.
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| 29. |
- Goel, Sneha, 1993-, et al.
(författare)
-
Residual stress determination by neutron diffraction in powder bed fusion-built Alloy 718: Influence of process parameters and post-treatment
- 2020
-
Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 195
-
Tidskriftsartikel (refereegranskat)abstract
- Alloy 718 is a nickel-based superalloy that is widely used as a structural material for high-temperature applications. One concern that arises when Alloy 718 is manufactured using powder bed fusion (PBF) is that residual stresses appear due to the high thermal gradients. These residual stresses can be detrimental as they can degrade mechanical properties and distort components. In this work, residual stresses in PBF built Alloy 718, using both electron and laser energy sources, were measured by neutron diffraction. The effects of process parameters and thermal post-treatments were studied. The results show that thermal post-treatments effectively reduce the residual stresses present in the material. Moreover, the material built with laser based PBF showed a higher residual stress compared to the material built with electron-beam based PBF. The scanning strategy with the lower amount of residual stresses in case of laser based PBF was the chessboard strategy compared to the bi-directional raster strategy. In addition, the influence of measured and calculated lattice spacing (d0) on the evaluated residual stresses was investigated.
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| 30. |
- Gopalan, Hariprasad, et al.
(författare)
-
On the interplay between microstructure, residual stress and fracture toughness of (Hf-Nb-Ta-Zr)C multi-metal carbide hard coatings
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- The development of sputtered coatings with improved hardness-toughness property combination is widely sought after. Multi-element ceramic carbide (Hf-Nb-Ta-Zr)C coatings with excess carbon, synthesized by DC co-sputtering is presented in this study as a promising candidate to achieve this objective. The specific roles of microstructure and residual stress are decoupled in order to understand their influence on the mechanical properties. Extensive mechanical characterization through in situ testing of focused ion beam fabricated microcantilevers and nanoindentation based approaches are adopted to quantitatively separate the effect of residual stresses on the fracture toughness of the (Hf-Nb-Ta-Zr)C coatings. Residual stress free, microcantilever testing in notched and unnotched conditions, in combination with microstructural characterization unambiguously reveals the intrinsic mechanical behavior of coatings, which solely depend on the microstructure. On the other hand, nanoindentation based testing techniques probe the influence of residual stress and microstructure on the measured mechanical properties. The segregation and thickening of carbon-rich clusters, especially to the grain boundaries with increasing deposition temperatures is speculated to lead to substantial degradation in all mechanical properties measured. An easier fracture path through grain boundaries leads to a reduction in fracture resistance, which is possibly related to carbon enrichment.
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| 31. |
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| 32. |
- Hassila, C.J., et al.
(författare)
-
Potential of nitrogen atomized alloy 625 in the powder bed fusion laser beam process
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 221, s. 110928-110928
-
Tidskriftsartikel (refereegranskat)abstract
- Powder based metal additive manufacturing processes like Powder Bed Fusion – Laser Beam utilize gasatomized metal powders as feedstock material. Typically, for nickel-based alloys such as Alloy 625, argongas is used during the atomization process. Considering the larger environmental impact of argon gascompared to nitrogen gas, and the increasing use of gas atomized metal powders, the environmentalimpact of powder based additive manufacturing techniques could be mitigated if gas atomization ofalloys such as Alloy 625 using nitrogen was possible. This work investigates the feasibility of tailoringan alloy to allow atomization using nitrogen gas while remaining within the Alloy 625 specification.This is achieved by limiting the nitrogen pick-up during the atomization process, primarily by reducingthe titanium content. The metallurgical implications of this tailored alloy and the subsequent atomizationusing nitrogen, as well as the attained microstructure from the Powder Bed Fusion – Laser Beam processis investigated and compared to a more common 625 alloy composition which was atomized usingargon. Furthermore, the microstructural development of the alloys after heat treatments are evaluated.Lastly corrosive properties, as well as tensile and impact properties are evaluated both in the as-builtand hot isostatic pressed condition.
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| 33. |
- Hosseini, Vahid, 1987-, et al.
(författare)
-
Fe and Cr phase separation in super and hyper duplex stainless steel plates and welds after very short aging times
- 2021
-
Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 210
-
Tidskriftsartikel (refereegranskat)abstract
- Fe and Cr phase separation in ferrite, causing 475°C-embrittlement, was studied after very short aging times in super duplex stainless steel (SDSS) and hyper duplex stainless steel (HDSS) plates and welds. Atom probe tomography showed that hot-rolled SDSS, experiencing significant metal working, had faster kinetics of phase separations compared to the SDSS and HDSS welds after 5 min aging at 475 °C. The surface of the 33-mm SDSS plate had faster Fe and Cr phase separation and larger toughness drop. A higher density of dislocations next to the austenite phase boundary in ferrite, detected by electron channeling contrast, can promote the phase separation at the surface of the plate with lower austenite spacing. The toughness dropped in HDSS welds after aging, but SDSS welds maintained their toughness. An inverse simulation method considering an initial sinusoidal nanometric Cr and Fe fluctuation showed that Ni increases the interdiffusion of Cr in the system, resulting a higher degree of phase separation in SDSS welds than the HDSS weld. Within the composition range of the studied SDSS and HDSS materials, the processing influences the Fe and Cr phase separation more than the variation in composition during short aging or typical fabrication times.
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| 34. |
- Ioannidou, Chrysoula, et al.
(författare)
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In-situ synchrotron X-ray analysis of metal Additive Manufacturing : Current state, opportunities and challenges
- 2022
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 219, s. 110790-
-
Tidskriftsartikel (refereegranskat)abstract
- Additive Manufacturing (AM) is becoming an important technology for manufacturing of metallic materials. Laser-Powder Bed Fusion (L-PBF), Electron beam-Powder Bed Fusion (E-PBF) and Directed Energy Deposition (DED) have attracted significant interest from both the scientific community and the industry since these technologies offer great manufacturing opportunities for niche applications and complex geometries. Understanding the physics behind the complex and dynamic phenomena occurring during these processes is essential for overcoming the barriers that constrain the metal AM development. Insitu synchrotron X-ray characterization is suitable for investigating the microstructure evolution during processing and provides new profound insights. Here, we provide an overview of the research on metal PBF and DED using in-situ synchrotron X-ray imaging, diffraction and small-angle scattering, highlighting the state of the art, the instrumentation, the challenges and the gaps in knowledge that need to be filled. We aim at presenting a scientific roadmap for in-situ synchrotron analysis of metal PBF and DED where future challenges in instrumentation such as the development of experimental stations, sample environments and detectors as well as the need for further application oriented research are included.
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| 35. |
- Jadhav, Suraj Dinkar, et al.
(författare)
-
Laser powder bed fusion additive manufacturing of highly conductive parts made of optically absorptive carburized CuCr1 powder
- 2021
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 198
-
Tidskriftsartikel (refereegranskat)abstract
- Fabrication of fully dense and highly conductive copper alloy parts via laser-based additive manufacturing (L-AM) is challenging due to the high optical reflectivity of copper at λ = 1060 – 1080 nm and high thermal conductivity. To overcome this, the use of optically absorptive surface-modified copper powders is being evaluated in the laser powder bed fusion (LPBF) process. Although the surface-modified powders exhibit high optical absorption at room temperature, not all of them allow the fabrication of fully dense parts at a laser power below 500 W. Accordingly, this article proposes the use of optically absorptive carburized CuCr1 powder for the consistent fabrication of copper parts. Moreover, a densification mechanism of parts is discussed to explain the distinct LPBF processing behavior of different surface-modified powders, such as carburized CuCr1 and carbon mixed CuCr1 powders, albeit having similar room temperature optical absorption. This investigation clearly outlines the advantage of a firmly bonded modified layer present on the surface of the carburized CuCr1 powder over a loosely attached carbon nanoparticle layer present in the carbon-mixed CuCr1 powder. Apart from the successful fabrication of CuCr1 parts, fabricated parts are subjected to two different post-heat treatments, and it is shown that the final properties can be customized by applying tailored post-heat treatments.
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| 36. |
- Jaladurgam, Nitesh Raj, 1993, et al.
(författare)
-
Macro- and micro-mechanical behaviour of a γ′ strengthened Ni-based superalloy at cryogenic temperatures
- 2021
-
Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- In-situ neutron diffraction was performed during tensile deformation of Ni-base superalloy, Haynes 282, at 20, 100 and 300 K. Two distinct uni-modal microstructures with fine (20 nm) and coarse (200 nm) \(\gamma^\prime\) particles were investigated. On the macro-scale yield strength increased and ductility decreased with decreasing temperature, although most significant decrease in ductility occurred between 100 and 20 K. The work hardening differed between the two microstructures, but was independent of temperature for each microstructure. On the micro-scale intergranular elastic interactions mainly lead to a transfer of the load to grains with the $\left<200\right>$ parallel to the tensile axis. No further load re-distribution between matrix and particles occurred in the microstructure with fine \(\gamma^\prime\), where shearing of precipitates lead to co-deformation at all temperatures. In the coarse \(\gamma^\prime\) microstructure, the load was transferred intragranularly from matrix to particles, in addition to the intergranular load transfer. The particles initially behaved elastically while the matrix deformed plastically, but at higher stresses a change in load partitioning indicated that also the \(\gamma^\prime\) phase underwent plastic deformation as a result of the elastic stress build-up from the load partitioning. The tendency for, and effect of, plastic deformation of \(\gamma^\prime\) increased with decreasing temperature.
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| 37. |
- Jandaghi, Mohammadreza, et al.
(författare)
-
Exploring the efficiency of powder reusing as a sustainable approach for powder bed additive manufacturing of 316L stainless steel
- 2024
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 244
-
Tidskriftsartikel (refereegranskat)abstract
- The efficiency and sustainability of Laser Powder Bed Fusion (L-PBF) greatly depends on the ability to recycle the used powder since a large portion of the feedstock remains unsolidified surrounding the printed part. To assess the impact of reusing iterations on the properties of the feedstock and printed part, we employed thermodynamic simulation to study oxidation in the building chamber. We then compared the 5 times reused powder of austenitic steel 316L (SS316L) and the printed part with its virgin counterpart. Our findings revealed that minor residual oxygen in the building atmosphere reacts with the molten pool and hot spatters, leading to the formation of Rhodonite (MnSiO3) 3 ) inclusions. As sieving cannot remove oxides smaller than steel particles, the repetition of feeding the used powder into the printing process directly increases the fraction of oxides in the printed parts. The increase in inoculated oxygen by reusing, coupled with the dissolution of oxides into the molten pool, facilitates the formation of Spinel (MnCr2O4) 2 O 4 ) and Tridymite (SiO2) 2 ) oxides, as well as clustered inclusions. While small oxides anchor cellular structures, stress concentration on the coarse fragile inclusions leads to sudden rupture and weaker tensile strength of the printed part with reused SS316L powder.
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| 38. |
- Jarfors, Anders E.W. 1963-, et al.
(författare)
-
On the nature of the anisotropy of Maraging steel (1.2709) in additive manufacturing through powder bed laser-based fusion processing
- 2021
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 204
-
Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing is growing rapidly as a manufacturing method. Additive manufacturing is a rapid solidification process and may, as such, generate new microstructures with an improvement of mechanical properties compared to conventional manufacturing. The repeatability and deeper understanding of properties repeatability for both mechanical and thermophysical properties are not well-established. In the current study, a complete analysis of the nature of the anisotropy is experimentally analysed to provide input for better understanding of the printing process and the resulting properties as reliability and predictability are important factors to build trust in a new manufacturing process.
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| 39. |
- Jungstedt, Erik, et al.
(författare)
-
Fracture toughness of wood and transparent wood biocomposites in the toughest LT-direction
- 2023
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 231
-
Tidskriftsartikel (refereegranskat)abstract
- Fracture toughness and mechanisms of crack growth are characterized for transparent wood polymer biocomposites and compared to native wood, with the crack normal to the fiber direction (LT fracture plane). Side-grooved specimen geometries generated pure mode I crack growth, whereas previous investigations commonly report 90° crack path deflection. Crack growth micromechanisms were analyzed by experimental fracture tests and in-situ microscopy observations. Large damage zones around the crack tip with fiber bundle bridging and pull-out were observed in the crack wake, justifying more advanced cohesive zone modeling suitable for composite materials design. The polymer matrix resulted in much higher fracture energy of the biocomposites compared to native wood due to increased local cohesive strength. This strength increased from the polymer contribution and more homogeneous stress distribution in the wood fibers.
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| 40. |
- Kaplan, Maciej, 1991-, et al.
(författare)
-
Combinatorial design of amorphous TaNiSiC thin films with enhanced hardness, thermal stability, and corrosion resistance
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 220
-
Tidskriftsartikel (refereegranskat)abstract
- Amorphous TaNiSiC and TaNiC films (with varying Ta/Ni and Si/C ratios) were deposited using combinatorial magnetron sputtering. The TaNiSiC films remained X-ray amorphous after four hour-long annealings up to 700 °C, while TaNiC alloys with high Ni and C contents crystallized. These differences were attributed to a strong driving force for separation of Ni and C in TaNiC, whereas the addition of Si, due to its solubility in the other elements, reduced the elemental segregation in TaNiSiC. The as-deposited TaNiSiC films exhibited hardnesses of 9–12 GPa. Annealing led to an increase in hardness by 2–4 GPa, due to decreases in average atomic distance, as evidenced by X-ray diffraction measurements. Potentiodynamic polarizations from –0.7 to +1.5 V vs. Ag/AgCl (3 M NaCl) in 10 mM sodium borate showed lower current densities by up to 2 orders of magnitude with increasing Ta content (28–52 at.%). Changes in Si/C content (7–13 at.% Si) had no effect. However, optical microscopy showed that TaNiSiC films with high Si/low C contents (13/10 at.%) suffered much less localized etching compared to TaNiC films. Thus, Si had a significant role in increasing the mechanical strength, corrosion resistance, and thermal stability of the TaNiSiC films.
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| 41. |
- Kisielewicz, Agnieszka, et al.
(författare)
-
In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718
- 2020
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.
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| 42. |
- Koutna, Nikola, et al.
(författare)
-
Phase stability and mechanical property trends for MAB phases by high-throughput ab initio calculations
- 2024
-
Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 241
-
Tidskriftsartikel (refereegranskat)abstract
- MAB phases (MABs) are atomically-thin laminates of ceramic/metallic-like layers, having made a breakthrough in the development of 2D materials. Though offering a vast chemical and phase space, relatively few MABs have been synthesised. To guide experiments, we perform high-throughput ab initio screening of MABs that combine group 4-7 transition metals (M); Al, Si, Ga, Ge, or In (A); and boron (B) focusing on their phase stability trends and mechanical properties. Considering the 1:1:1, 2:1:1, 2:1:2, 3:1:2, 3:1:3, and 3:1:4 M:A:B ratios and 10 phase prototypes, synthesisability of a single-phase compound for each elemental combination is estimated through formation energy spectra of competing dynamically stable MABs. Based on the volumetric proximity of energetically-close phases, we identify systems in which volume-changing deformations may facilitate transformation toughening. Subsequently, chemistry- and phase-structure-related trends in the elastic stiffness and ductility are predicted using elastic-constants-based descriptors. The analysis of directional Cauchy pressures and Young's moduli allows comparing mechanical response parallel and normal to M-B/A layers. The suggested promising MABs include Nb 3 AlB 4 , Cr 2 SiB 2 , Mn 2 SiB 2 or the already synthesised MoAlB.
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| 43. |
- Kretschmer, Andreas, et al.
(författare)
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High-entropy alloy inspired development of compositionally complex superhard (Hf,Ta,Ti,V,Zr)-B-N coatings
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 218
-
Tidskriftsartikel (refereegranskat)abstract
- Phase stability and mechanical properties of multimetal-boronnitride (Hf,Ta,Ti,V,Zr)-B-N is investigated by ab initio computations and experimental methods. (Hf,Ta,Ti,V,Zr)-B-N shows a strong energetic preference for the fcc NaCl-type structure over other structures up to a B:N ratio of 3.5. Reactively deposited (Hf,Ta,Ti,V,Zr)-B-N coatings show formation of X-ray amorphous BN, accompanied by a drastic hardness decrease with increasing B content. But non-reactively sputtered (Hf,Ta,Ti,V,Zr)-B-N coatings exhibit a single-phase fcc solid solution, up to the maximum B:N ratio of 1.12 studied, in good agreement with calculations. All non-reactively sputtered multimetal-boronnitride coatings contain a high Zr metal-fraction and approximate to 8at% C, stemming from impurities in the target. The single-phase coatings reach superhardness up to 46.3 GPa. Even after vacuum annealing to 1200 degrees C, the hardness of the coating with a B:N ratio of 1.03 is still 43.7 GPa, while that of ZrN0.72C0.28 decreased from 36.3 to 30.2 GPa. Our results demonstrate the importance of the deposition technique to deposit single-phased coatings with exceptional hardness and thermal stability. (C) 2022 The Authors. Published by Elsevier Ltd.
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| 44. |
- Lamelas, Victor, et al.
(författare)
-
Modelling the formation of detrimental phases in cemented carbides
- 2023
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 228, s. 111823-
-
Tidskriftsartikel (refereegranskat)abstract
- Integrated Computational Materials Engineering (ICME) has proved to be an efficient tool for understand-ing the process-structure-property relationships and helping us to design materials. For instance, in cemented carbides manufacturing, one of the most critical parameters is the C-window. It is defined as the C content range for which phases detrimental to the mechanical properties are avoided. This pro-cessing window has been traditionally defined using applied thermodynamics methods. However, the deviation between equilibrium calculations and real manufacturing conditions requires big additional empirical efforts to precisely define the C-window. In this work, an ICME-based approach is proposed to redefine the processability limits of cemented carbides taking the cooling rate and the material's initial powder size into consideration. The method relies on the interactive coupling of several adapted models and tools, to not only set the processability boundaries, but also to study the complex mechanisms inter-play happening along microstructural evolution. A better understanding of these underlaying mecha-nisms leads to new inputs that can be used in the design of cemented carbides. In this regard, it is observed that faster cooling rates or coarser WC grades could be effectively used to prevent nucleation of the detrimental phases enlarging the C-window towards lower C contents.
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| 45. |
- Leijon, Freddy, et al.
(författare)
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A novel rapid alloy development method towards powder bed additive manufacturing, demonstrated for binary Al-Ti, -Zr and -Nb alloys
- 2021
-
Ingår i: Materials & design. - : Elsevier Science Ltd. - 0264-1275 .- 1873-4197. ; 211
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Tidskriftsartikel (refereegranskat)abstract
- Powder bed fusion (PBF) methods offer the best material properties among metal additive manufacturing (AM) processes. Yet, alloy development for PBF is only at its infancy and has a great untapped potential. This originates from the high solidification rate within the melt pool and to exploit the full potential of materials produced by PBF methods, a diligent work lies ahead. This paper presents a high-throughput method to rapidly screen large compositional alloy intervals experimentally for their PBF feasibility, which can drastically reduce the time needed for alloy development and provide valuable data for modelling. Our method consists of two steps; co-sputtering and electron beam re-melting. First step produces an alloy gradient film on a sheet substrate. The film is then re-molted to produce a PBF mimicked microstructure. The method is successfully demonstrated on binary systems; Al-Ti,-Zr and-Nb and produced gradients in compositional ranges of 3-50 wt%Ti, 1-15 wt%Zr and 2-15 wt%Nb over a length of 200 mm. From the produced materials, the alloying efficiency could be investigated and determined regarding hardness and grain refinement. Zr shows the highest strength contribution per at% and the best grain refinement at low levels. However, at higher levels grain refinement efficiency decreases for Zr. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
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| 46. |
- Leijon, Freddy, et al.
(författare)
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Investigation of Ti-1_x(Zr,Ta,V,W)(x)B-2 and A(l3)Ti(1_x)(Zr,V)(x) grain refiners in additively manufactured Al-2 wt%Cu alloys by a high throughput method
- 2022
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Ingår i: Materials & design. - : Elsevier Science Ltd. - 0264-1275 .- 1873-4197. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- Grain refinement plays a central role in powder bed fusion (PBF) additive manufacturing by preventing hot cracking and thus enabling the development of high-strength alloys. However, the mechanism behind grain refinement is not fully understood for conventional casting, nor for PBF. In this work, a high throughput method have been used to produce Al-2 wt%Cu alloys with additions of Ti1-xM(Zr,Ta,V,W)(x)B-2, Al3Ti1-xM(Zr,V)(x) or AlB2 grain refiners for 0.1 < x < 0.9. It was found that grain size varied with x, M and the sum of Ti + M. Ti1-xMxB2 grain refiners offered no advantage over Al3Ti1-xMx. Overall, Ti and Zr provide the best grain refinement, both as Ti1-xMxB2 and Al3Ti1-xMx. However, Ti1-xZrxB2 had a grain refinement minimum around x = 0.65-0.70. The behavior was similar with Ta, but to a lesser extent. V and W had detrimental effects on grain refinement. Despite the fact that no AlB2 particles were observed, additions of B provided excellent grain refinement and was more efficient than Ti below 0.5at%. Ti1-xMxB2 lattice parameters varied with x and followed Vegards law, however, a clear relationship between grain size and epitaxial strain/lattice match could not be established. Similarly, the growth restricting factor alone was not a predictor of grain size.
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| 47. |
- Lewin, Susanne, et al.
(författare)
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Additively manufactured mesh-type titanium structures for cranial implants : E-PBF vs. L-PBF
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- A patient-specific titanium-reinforced calcium phosphate (CaP–Ti) cranial implant has recently shown promising clinical results. Currently, its mesh-type titanium structure is additively manufactured using laser beam powder bed fusion (L-PBF). Nevertheless, an electron-beam (E-PBF) process could potentially be more time efficient. This study aimed to compare the geometrical accuracy and mechanical response of thin titanium structures manufactured by L-PBF (HIPed) and E-PBF (as-printed). Tensile test (ø = 1.2 mm) and implant specimens were manufactured. Measurements by μCT revealed a deviation in cross-sectional area as compared to the designed geometry: 13–35% for E-PBF and below 2% for L-PBF. A superior mechanical strength was obtained for the L-PBF specimens, both in the tensile test and the implant compression tests. The global peak load in the implant test was 457 ± 9 N and 846 ± 40 N for E-PBF and L-PBF, respectively. Numerical simulations demonstrated that geometrical deviation was the main factor in implant performance and enabled quantification of this effect: 34–39% reduction in initial peak force based on geometry, and only 11–16% reduction based on the material input. In summary, the study reveals an uncertainty in accuracy when structures of sizes relevant to mesh-type cranial implants are printed by the E-PBF method.
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| 48. |
- Li, Xiaojie, et al.
(författare)
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The influence of temperature on the elastic properties of body-centered cubic reduced activation steels
- 2021
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- A first-principles based modeling approach to the effect of temperature on the isothermal single-crystal and polycrystalline elastic parameters of Fe-rich solid solutions is reported. The approach integrates alloy theory for chemical and magnetic disorders with accessible experimental data for the equilibrium volume and ferromagnetic phase transition, and is adopted to predict the temperature-dependent elastic parameters of the body-centered cubic phase of three reduced activation steels, CLAM/CLF-1, F82H, EUROFER97, considered as high-temperature material in power reactors. The predictions are assessed based on available experimental data for a reduced activation steel and both experimental and theoretical data for pure Fe. Alloying effects on the elastic constants relative to pure Fe are found to differ in the magnetically ordered and disordered phases. Contributions due to loss of long-range magnetic order, volume expansion, and entropy are important in determining the temperature dependence of the elastic parameters in all investigated materials. A previously reported, peculiar magneto-volume phenomenon on the equation of state in pure Fe is gradually removed by alloying and magnetic disordering, which requires particular attention when describing the thermo-chemical effects derived from the equation of state in Fe-rich solid solutions.
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| 49. |
- Ling, Senlin, et al.
(författare)
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Predicting the mechanical properties of semi-flexible pavement material with micromechanical modeling
- 2024
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 239
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Tidskriftsartikel (refereegranskat)abstract
- Semi-flexible pavement (SFP) material is a composite comprising cement, coarse aggregates and asphalt mortar, which has complex mechanical properties. Traditional experimental methods struggle to accurately quantify the effect of each phase and their interfaces on the SFP's mechanical properties. Micromechanical modelling based on finite element method offers a promising solution. In this study, a new micromechanical model for SFP is proposed, idealizing the material by representative volume elements. SFP mesostructure is represented as a simplified five element composite consisting of cement, asphalt mortar, aggregate, pore and cement-asphalt mortar interface. Periodic boundary conditions are used to simulate an infinite repetitive structure within a finite computational domain. The resulting model allows evaluating the stiffness and damage resistance of SFP in a computationally efficient manner. This model is utilized to explore the mechanical properties of SFPs and the results are compared with the experimental findings. The results show that the model captures the uniaxial compressive strength and stiffness for all materials examined. The model is further used to evaluate the effect of properties of individual elements of SFP on its stiffness and strength. The feasibility of using the proposed modelling approach to optimize the material design of SFP is discussed.
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| 50. |
- Liu, Dachuan, et al.
(författare)
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Amorphous iron-calcium phosphate-mediated biomineralized scaffolds for vascularized bone regeneration
- 2023
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- Construction of organic–inorganic composites similar to natural bone in terms of structure and composition has attracted extensive attention. However, the clinical applications of these composites are limited due to the insufficient osteogenic and mechanical properties. In nature, the presence of amorphous iron-calcium phosphate (Fe-ACP) strengthens the mechanical properties of some biominerals, and our previous study has revealed its synthetic route and in vitro osteogenic properties. However, the potential role of Fe-ACP on biomineralization and constructing biomimetic scaffolds for bone regeneration has not been studied. Herein, a biomimetic scaffold with good osteogenic property was fabricated based on the mineralization of Fe-ACP, with the assistance of ice-templated freeze-casting. The in vitro study showed that the mineralized scaffolds possessed favorable biocompatibility and osteogenic property. Moreover, the scaffolds promoted cell chemotaxis and angiogenic property by upregulating the hypoxia inducible factor-1α (HIF-1α). In vivo experiment demonstrated potent early osteogenesis along with angiogenesis and ultimately promoted bone regeneration. Overall, the mineralized scaffold mediated by Fe-ACP precursors provide a unique platform to enhance bone tissue repair.
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