| 1. |
- Afroze, Shammya, 1987, et al.
(författare)
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Structure-conductivity relationship of PrBaMnMoO 6-δ through in-situ measurements: A neutron diffraction study
- 2021
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 47:1, s. 541-546
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Tidskriftsartikel (refereegranskat)abstract
- The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm−1 at 700 °C.
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| 2. |
- Aleni, Afshin H., et al.
(författare)
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3D printing of dense and porous TiO2 structures
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 46:10, s. 16725-16732
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Tidskriftsartikel (refereegranskat)abstract
- Direct foam writing allows the fabrication of highly porous and hierarchical ceramic structures with high specific mechanical properties. This manufacturing technique, however, has mainly used stabilized Al2O3 foam inks. In this work, we pressent a novel foam ink based on TiO2. This ink uses polyvinyl alcohol (PVA) as a binder and a small amount of zinc as a frothing agent. We used this ink to produce cylindrical foam samples via direct foam writing. The foams had a porosity of up to 65% and a mean pore size of 180 μm, which is significantly larger than previously reported for direct foam writing with Al2O3. The foams were tested in compression and were found to have an elastic modulus of 0.5 GPa and a compressive strength of 12–18 MPa. These mechanical properties are similar to those of porous ceramics produced by conventional manufacturing routes. Therefore, this work represents a step forward by broadening the direct foam writing process to a wider range of porous ceramics.
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| 3. |
- Alsalmah, Hessa A., et al.
(författare)
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Optical, conductivity, dielectric, and magnetic properties of polymer nanocomposite based on PAM/cs matrix and ZnFe2O4 NPs for use in magneto-electronic and energy storage capacitor devices
- 2024
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 50:7, s. 12167-12174
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a cast synthesis approach was used to create flexible nanocomposite films made of polyacrylamide (PAM), chitosan (Cs), and zinc ferrite nanoparticles (ZnFe2O4 NPs). XRD analysis was used to examine the composite structure. They demonstrated the effective interaction between ZnFe2O4 NPs and PAM/Cs blend. As the concentration of nanomaterial in the host polymer matrix grew, it was observed that the PAM/Cs matrix's direct and indirect energy band gaps decreased while its absorbance of ultraviolet-visible radiations increased. The nanocomposite's AC conductivity was significantly higher than that of the blend, and 2.5 wt percent of the nanocomposite showed the highest electrical conductivity. It was observed that as frequency raised, the epsilon ' and epsilon '' declined though the concentration of nanoparticles enhanced these characteristics. Because of the high dielectric permittivity of ZnFe2O4, the values of epsilon ' and epsilon '' raised as ZnFe2O4 were higher. The outcome of the vibrating sample magnetometer (VSM) demonstrated the ferromagnetic property of the produced nanocomposites. Furthermore, the VSM study shows that as the nanoparticles content increases, the PAM/Cs/ZnFe2O4 nanocomposites' Ms, Hc, and Mr also increase. These PAM/Cs/ZnFe2O4 films were shown by the experimental results to be promising candidates for bandgap-regulated materials, electromagnetic interference shielders, frequency tunable nanodielectric, and flexible dielectric substrates for future microelectronic, optoelectronic technologies, and capacitive energy storage.
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| 4. |
- Berg, Camilla, et al.
(författare)
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Bulk nanobubbles as soft templates in the fabrication of inorganic core-shell particles
- 2023
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:11, s. 16501-16513
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Forskningsöversikt (refereegranskat)abstract
- Hollow microstructured-and nanostructured-materials (also known as core-shell particles) have got great attention as advanced materials due to their fascinating physicochemical properties and favourable application prospects in many fields. In recent years, a variety of synthesis strategies have been explored to fabricate core-shell particles with different morphologies, compositions, microstructures, and thereby versatile functionalities. Among the synthesis strategies, soft-templating with the usage of nanobubbles is a feasible and effective one. Many inorganic core-shell particles have been prepared by using nanobubbles as a template. Nevertheless, studies in this field have not been reviewed comprehensively yet. Herein, the paper firstly reviewed several critical aspects of nanobubbles, such as the formation methods, stability and stabilization strategies of nano-bubbles; Secondly, characteristics of core-shell particles prepared by using nanobubbles soft template were summarized, including formation mechanisms, morphologies, etc.; Lastly, concerns regarding nanobubbles as soft templates were also briefly discussed.
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| 5. |
- Berg, Camilla, et al.
(författare)
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Electron microscopy evaluation of mineralization on peritubular dentin with amorphous calcium magnesium phosphate microspheres
- 2020
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:11, s. 19469-19475
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Tidskriftsartikel (refereegranskat)abstract
- Dentin hypersensitivity can be reduced by the use of a remineralization agent to hinder movement of fluids within the dentin tubules. Penetration of particles into the tubules and a continuous release of Ca2+ and phosphate ions can induce the mineralization of a material mimicking the mineral component of dentin, sealing the tubules. In this work, we have used complementary electron microscopy techniques to investigate the ultrastructure of dentin and crystallization and occlusion effects when using amorphous calcium magnesium phosphate (ACMP) microspheres on extracted human molars. Application of the particles in a gel intended for athome use resulted in intra-tubular mineralization of a carbonate substituted hydroxyapatite (HA). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that crystallization was initiated on the peritubular dentin (PTD) with undirected crystal growth leading to the formation of a porous material. We additionally investigated the effects from using a fluoride toothpaste to potentially improve the remineralization and anti-cariogenic properties of the ACMP microspheres. Energy dispersive x-ray spectroscopy (EDX) using TEM in scanning mode (STEM) showed that fluoride incorporation resulted in an increase in aspect ratio of the crystals, crystal growth directed towards the center of the tubule lumen and densification of the mineralized material. Thus, ACMP microspheres are promising alternatives as occluding agents and the efficacy of the particles could be further improved with the complementary use of a fluoride toothpaste.
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| 6. |
- Chen, Qingguo, et al.
(författare)
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Preparation and properties of Ce0.5Nd0.5PO4 monazite ceramics by pressureless sintering and spark plasma sintering (SPS)
- 2024
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 50:12, s. 20803-20810
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Tidskriftsartikel (refereegranskat)abstract
- LnPO4·nH2O rhabdophane/monazite is an important actinide-bearing material in the back end of the nuclear fuel cycle. In this work, using Nd3+ to simulate trivalent actinides, Ce0.5Nd0.5PO4·0.667H2O rhabdophane was synthesized by the wet-chemistry method in 90 °C and pH = 1 solution. The sintering behavior of associated Ce0.5Nd0.5PO4 monazite ceramics was investigated by pressureless sintering and spark plasma sintering (SPS), along with appraising their chemical stability. The results reveal that Ce3+ is successfully replaced by Nd3+ in the rhabdophane lattice, and rhabdophane can transform to monazite with a temperature over 750 °C. SPS can compact the ceramic sample at a lower temperature compared to pressureless sintering even if the grain size is smaller. Adding a pre-sintering process of 900 °C before SPS and pressureless sintering will further improve the density and Vickers hardness of ceramics. For the chemical stability of Ce0.5Nd0.5PO4 monazite ceramics, Ce is more likely to be leached compared to Nd, and the ceramics prepared by SPS with a pre-sintering process have the lowest normalized leaching rates, associated with the values of 2.03 × 10−5 g·m−2·d−1 and 0.75 × 10−5 g·m−2·d−1 for Ce and Nd, respectively.
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| 7. |
- Dey, J., et al.
(författare)
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Non-collinear magnetic structure of the MAX phase Mn2GaC epitaxial films inferred from zero-field NMR study (CE-5:L05)
- 2023
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 49:14, s. 24235-24238
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Tidskriftsartikel (refereegranskat)abstract
- Zero-field NMR investigations on the 69Ga, 71Ga, and 55Mn nuclei have been performed at 4.2 K on a 100 nm thick epitaxial Mn2GaC(0001) MAX phase film grown on a MgO(111) substrate. This nano-laminated structure consists of ferromagnetic Mn-C-Mn stacks interleaved with monolayers of gallium. A resolved quadrupolar structure of the observed gallium resonances is a fingerprint of a well-defined crystal field confirming high crystal quality. The nuclei of non-magnetic gallium atoms are shown to experience the transferred hyperfine magnetic field of 15.75 T (& PLUSMN;0.05 T), which is due to polarization of their 4s electron shell by the magnetic moments of manganese neighbors, evidencing the presence of an uncompensated ferromagnetic moment within the manganese sublattice. The average magnetic moment of manganese was found to be around 2 & mu;B, strongly contrasting with the reported remnant magnetization of only 0.3 & mu;B. Moreover, the 55Mn NMR spectrum in-dicates the presence of magnetically non-equivalent manganese sites within this structure. The observed features of the 69,71Ga and 55Mn NMR spectra cannot be reconciled with any of the hitherto proposed collinear ar-rangements of manganese moments and suggest their non-collinear arrangement across a gallium layer. Nevertheless a more advanced study is required to elucidate the detailed nature of magnetic structure in this material.
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| 8. |
- Dziewanowska, Julia, et al.
(författare)
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Nanocrystallization as a tool for controlling in vitro dissolution of borophosphate glass
- 2023
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:16, s. 27382-27390
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Tidskriftsartikel (refereegranskat)abstract
- The controlled nanocrystallization of sodium-calcium-borophosphate glass (Na16.6Ca5.1B10.5Al0.8P10.5 O56.5 in at %) was conducted to investigate its influence on in vitro dissolution. Three temperatures (570 degrees C, 590 degrees C, and 610 degrees C) were selected based on thermal analysis and investigation of the morphology, structure, and in vitro dissolution of glass and glass-ceramics was conducted. The results of X-ray diffraction confirmed the presence of calcium phosphates nanocrystallites in glass-ceramics, with their contents increasing proportionally to the crystallization temperature. Infrared spectroscopy showed the presence of phosphate and borate network units, along with phosphates in a crystalline form. It was found that the target glass shows the highest mass loss in comparison to the glass-ceramics. Controlled nanocrystallization slowed down the dissolution of the materials (>10%), but did not adversely affect the deposition of hydroxyapatite layer. The presence of calcium phosphate nanocrystallites favors the process of B3+ release. The nanocrystallization of borophosphate glasses is a perspective tool for controlling the rate of dissolution of bioactive materials and enhancing their ability to de-posit hydroxyapatite on their surface.
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| 9. |
- Enrichi, Francesco, et al.
(författare)
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Ag-sensitized Tb3+/Yb3+ codoped silica-zirconia glasses and glass-ceramics : systematic and detailed investigation of the broadband energy-transfer and downconversion processes
- 2021
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:13, s. 17939-17949
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Tidskriftsartikel (refereegranskat)abstract
- Various studies report that Tb3+/Yb3+ co-doped materials can split one UV or 488 nm (visible) photon in two near infrared (NIR) photons at 980 nm by an energy-transfer process involving one Tb3+ and two Yb3+ ions. Additionally, it was demonstrated that Ag multimers can provide an efficient optical sensitizing effect for rare earth ions (RE3+ ions), resulting in a broadband enhanced excitation, which could have a significant technological impact, overcoming their limited spectral absorptions and small excitation cross sections. However, a systematic and detailed investigation of the down-conversion process enhanced by Ag nanoaggregates is still lacking, which is the focus of this paper. Specifically, a step by step analysis of the energy-transfer quantum-cutting chain in Ag-exchanged Tb3+/Yb3+ co-doped glasses and glass-ceramics is presented. Moreover, the direct Ag-Yb3+ energy-transfer is also considered. Results of structural, compositional, and optical characterizations are given, providing quantitative data for the efficient broadband Ag-sensitization of Tb3+/Yb3+ quantum cutting. A deeper understanding of the physical processes beneath the optical properties of the developed materials will allow a wiser realization of more efficient energy-related devices, such as spectral converters for silicon solar cells and light-emitting devices (LEDs) in the visible and NIR spectral regions.
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| 10. |
- Enrichi, Francesco, et al.
(författare)
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Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics
- 2022
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:24 Part B
-
Tidskriftsartikel (refereegranskat)abstract
- The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.
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| 11. |
- Fu, Le, et al.
(författare)
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New insights into the formation mechanism of zircon in a ZrO2-SiO2 nanocrystalline glass-ceramic : A TEM study
- 2022
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:18, s. 27097-27105
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Tidskriftsartikel (refereegranskat)abstract
- We have previously observed that doping of Ca ions was beneficial to the formation of zircon (ZrSiO4). It is well known that synthetic ZrSiO4 is typically formed via a solid-state reaction between ZrO2 and SiO2, in which the interfaces between the reactant and resultant play an important role. However, the interfaces are lacking detailed microstructural observation. This follow-up study aims at exploring the formation mechanism of ZrSiO4 by inspecting the interfaces at the nano and atomic scales with TEM techniques. Results demonstrated that ZrSiO4 was formed in the Ca-doped sample after sintering at 1200 ?, whereas, no ZrSiO4 was formed in the undoped sample even after sintering at 1230 ?. The Ca-doped sample consisted of a continuous ZrSiO4 matrix with dispersed ZrO2 nanocrystallites. Doping of Ca ions promoted the formation of ZrSiO4 by causing lattice distortion and oxygen vacancies in ZrO2 lattices. Thin amorphous grain boundary complexions were found between ZrO2 nanocrystallites and between ZrO2 and ZrSiO4 crystallites. These amorphous complexions acted as reaction sites and an intermediate metastable state for the solid-state reaction. A detailed formation mechanism of ZrSiO4 at the nanometer scale and atomic scale has been proposed.
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| 12. |
- Ganvir, Ashish, 1991-, et al.
(författare)
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Effect of suspension characteristics on the performance of thermal barrier coatings deposited by suspension plasma spray
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:1, s. 272-283
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the influence of suspension characteristics on microstructure and performance of suspensions plasma sprayed (SPS) thermal barrier coatings (TBCs). Five suspensions were produced using various suspension characteristics, namely, type of solvent and solid load content, and the resultant suspensions were utilized to deposit five different TBCs under identical processing conditions. The produced TBCs were evaluated for their performance i.e. thermal conductivity, thermal cyclic fatigue (TCF) and thermal shock (TS) lifetime. This experimental study revealed that the differences in the microstructure of SPS TBCs produced using varied suspensions resulted in a wide-ranging overall TBC performance. All TBCs exhibited thermal conductivity lower than 1 W/(m. K) except water-ethanol mixed suspension produced TBC. The TS lifetime was also affected to a large extent where 10 wt % solid loaded ethanol and 25 wt % solid loaded water suspensions produced TBCs exhibited the highest and the lowest lifetime, respectively. On the contrary, TCF lifetime was not as significantly affected as thermal conductivity and TS lifetime, and all ethanol suspensions showed marginally better TCF lifetime than water and ethanol-water mixed suspensions deposited TBCs. © 2020
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| 13. |
- Gholizadeh, Armin, et al.
(författare)
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Facile synthesis of nanographene by a high-yield and scalable method
- 2020
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:14, s. 22861-22868
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to synthesize nanographene (NG) through a simple, efficient, and cost-effective method. In this regard, a combination of microwave (MW) and shear mixing with a kitchen blender was used. Atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were used to investigate the structure of synthesized NG. The Results of the characterizations demonstrated that most of the synthesized NG exhibited OD structure and bilayer characteristics. The obtained results introduce a method for synthesizing NG at a large scale through a combination of MW and shear, in a relatively short time, without any need for purification.
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| 14. |
- Govindan, V., et al.
(författare)
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One-pot microwave synthesis of SnSe and Lanthanum doped SnSe nanostructure with direct Z scheme pattern for excellent photodegradation of organic pollutants
- 2022
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:9, s. 12228-12239
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Tidskriftsartikel (refereegranskat)abstract
- A novel nanostructure photocatalytic material was fabricated using Lanthanum doped SnSe by one-pot microwave method is reported to newest. Photocatalytic performance efficiency of pristine SnSe and Lanthanum doped SnSe nanostructures were investigated to degrade organic pollutants from wastewater. The crystal structure, morphology, and optical properties of the nanostructure were investigated using powder X-ray diffraction, field emission scanning electron microscope, UV–Vis, and PL spectral studies. Nano rods/spheres for pure SnSe were altered significantly leading to higher amounts of nanorods due to La doped and increase in concertation leads higher formation of nanorods. Increased in structure and morphology played a vital role in photocatalytic activity. Nanostructure exhibits enhanced physicochemical properties and showed an excellent synergetic effect demonstrating the effect of La (1, 3, and 5%) concentrations in SnSe nanostructure. The optical energy gap has a reducing trend due to the increment of doping concentration. The individual elements oxidation states were justified from X-ray photoelectron spectroscopical studies. Thermal stability and phase changes of the nanostructure before and after doping of La were evaluated through TGA/DTA analysis. From the photocatalytic measurement rare-earth (La) doped samples expressed higher catalytic nature than the pure SnSe. It was observed that the higher atomic element La had a significant role to produce a large number of electron-hole pair recombination and defective structure in the host lattice.
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| 15. |
- Guo, Hua, et al.
(författare)
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Quantitative phase analyses of biomedical pyrophosphate-bearing monetite and brushite cements by solid-state NMR and powder XRD
- 2020
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:8, s. 11000-11012
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive composition analysis of calcium phosphate cements (CPCs) incorporating increasing amounts of bioactive pyrophosphate species (up to 17 wt% P2O7). These cements comprise primarily poorly ordered monetite (CaHPO4) or brushite (CaHPO4 center dot 2H(2)O) and are investigated for enhanced osteoinductive bone/tooth implants. The specimens were characterized by magic-angle spinning (MAS) P-31 and H-1 nuclear magnetic resonance (NMR) spectroscopy along with powder X-ray diffraction (PXRD). P-31 MAS NMR was employed to quantify the major monetite/brushite constituents, the crystalline and amorphous pyrophosphates, as well as various minor orthophosphate by-products. The NMR-derived contents of the crystalline phases accorded well with those from Rietveld analyses of the corresponding PXRD data. The amounts of crystalline and amorphous pyrophosphate depended on the precise cement precursor mixture and preparation conditions, which together with their distinct structural roles may enable the design of cements with a tunable P2O74 - release into aqueous solutions.
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| 16. |
- Horng, Ray-Hua, et al.
(författare)
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Ion implantation effects on the characteristics of 8-Ga2O3 epilayers grown on sapphire by MOCVD
- 2022
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 48:24, s. 36425-36432
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the Si-ions implantation technique with different doses from 1 x 1014 to 1 x 1015 cm-2 and dose energy 30, 40 and 50 keV was used to tune the electrical properties in unintentionally doped (UID) 8-Ga2O3 epilayers grown on the sapphire substrates by metalorganic chemical vapor deposition (MOCVD). A high quality UID 8-Ga2O3 epilayers were fabricated using the optimized growth parameters of MOCVD. The UID and Si-ions implanted 8-Ga2O3 epilayers were examined and results were compared with the help of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Si-ions implantation parameters were also simulated by stopping and range of ions in matter software (SRIM) and actual Si-ions concentration was measured by secondary ions mass spectroscopy. The electrical properties of the implanted 8-Ga2O3 epilayers were measured by transmission length method and Hall measurements. The sheet resistivity for the 8-Ga2O3epilayers with Si-ion dose of 1 x 1014, 6 x 1014 and 1 x 1015 cm-2 were found as 2.047, 0.158 and 0.144 Cd cm, respectively measured by Hall measurements and the electron carrier concentrations for the above doses were 4.39 x 1018, 6.86 x 1018 and 7.98 x 1019 cm-3. From the above results, the ion implantation was demonstrated to effectively reduce the resistivity with the high carrier concentrations.
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| 17. |
- Hossein-Babaei, Faramarz, et al.
(författare)
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Growing continuous zinc oxide layers with reproducible nanostructures on the seeded alumina substrates using spray pyrolysis
- 2020
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:7, s. 8567-8574
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Tidskriftsartikel (refereegranskat)abstract
- The growth of zinc oxide thin films with controlled nanostructures on the heat resistant dielectric substrates is important for the fabrication of gas sensors, transparent electric heating elements, pyroelectric electron emitters, and many other potential electronic and optoelectronic applications. The preferred substrate for many of these applications is alumina, but the production of uniform ZnO layers on alumina is hindered by the large lattice mismatch between ZnO and Al2O3 hexagonal crystal structures. Here, we systematically investigate the growth process of ZnO thin films on alumina substrates using the ultrasonic spray pyrolysis (USP) of zinc chloride solutions in ethanol and, for the first time, demonstrate the deposition of uniform layers on the alumina substrates appropriately seeded using magnetron sputtering prior to USP. On the pristine substrates, random nucleation of the isolated nanocrystallites results in uneven layers, and extending the growth process leads to the hierarchical growth of facetted ZnO nanorods and pyramids with weak physical attachments to the substrate surface. In similar conditions, USP deposition on the seeded substrates reproducibly results in continuous networks of densely packed ZnO crystallites intimately attached to the substrate surface with adjustable thickness and electrical conductance. These results are compared with those obtained for SnO2 in similar conditions. Regardless of its tetragonal crystal structure, SnO2 reproducibly forms even layers on the pristine alumina substrates.
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| 18. |
- Hu, Qi, et al.
(författare)
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Temperature stable dielectric properties of Mg2TiO4-MgTiO3-CaTiO3 ceramics over a wide temperature range
- 2023
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:2, s. 1997-2006
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Tidskriftsartikel (refereegranskat)abstract
- The zero resonant frequency temperature coefficient (zf) of microwave dielectric ceramics (MWDCs) at high and low temperature have attracted great attention in the development of microwave communication equipment. In this work, the Mg2TiO4-MgTiO3-CaTiO3 (MMC) ceramics with meeting the application requirements of 5G communication were prepared by traditional solid-phase sintering after investigating the relationship among phase compositions of xMg2TiO4-(0.931-x)MgTiO3-0.069CaTiO3 and 0.34Mg2TiO4-0.591MgTiO3-yCaTiO3, sin-tering process, and dielectric properties in detail. The results show that the dielectric properties of MMC ceramics are strongly affected by the phase relative contents of MgTiO3, Mg2TiO4 and CaTiO3. For instance, MMC ceramics with approximate zf = 0 is contributed by mutual compensation of Mg2TiO4 and MgTiO3, in which the Mg2TiO4 phase plays an important role in decreasing the zf value; and the increase of CaTiO3 will greatly increase the epsilon r value for MMC ceramics, while has a negative effect in the Q x f value. After three-phase regulation, the 0.32Mg2TiO4-0.611MgTiO3-0.069CaTiO3 microwave dielectric ceramic has a better dielectric temperature sta-bility, associated with dielectric properties of er = 19.7, Q x f = 55,400 GHz (at 8.43 GHz), zf-= 4.5 ppm/degrees C (-40 degrees C-25 degrees C), and zf+ =-5.1 ppm/degrees C (25 degrees C-90 degrees C).
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| 19. |
- Irshad, Muneeb, et al.
(författare)
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Evaluation of densification effects on the properties of 8 mol % yttria stabilized zirconia electrolyte synthesized by cost effective coprecipitation route
- 2021
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 47:2, s. 2857-2863
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Tidskriftsartikel (refereegranskat)abstract
- In the current work, properties of 8YSZ powder synthesized by co-precipitation method and sintered at 1200 degrees C, 1300 degrees C and 1400 degrees C are investigated. XRD analysis shows that all 8YSZ samples exhibit cubic phase and increased crystallite size is observed with increased sintering temperature. The relative density measurements show increased densification due to increased sintering temperature and relative density >96% is obtained for 8YSZ sintered at 1400 degrees C. SEM micrographs also confirm that structure becomes denser with increase in sintering temperature. EDX analysis confirms the elemental composition of 8YSZ and no impurity is observed while thermal analysis reveals weight losses within different temperature ranges. High ionic conductivity and maximum power density of 0.41 Wcm(-2) is obtained for cell having 8YSZ electrolyte sintered at 1400 degrees C owing to its compact, dense and gas tight microstructure.
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| 20. |
- Landström, Anton, et al.
(författare)
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Reduced graphene oxide-ZnO hybrid composites as photocatalysts : The role of nature of the molecular target in catalytic performance
- 2021
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:14, s. 19346-19355
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Tidskriftsartikel (refereegranskat)abstract
- Spurred by controversial literature findings, we enwrapped reduced graphene oxide (rGO) in ZnO hierarchical microstructures (rGO loadings spanning from 0.01 to 2 wt%) using an in situ synthetic procedure. The obtained hybrid composites were carefully characterized, aiming at shining light on the possible role of rGO on the claimed increased performance as photocatalysts. Several characterization tools were exploited to unveil the effect exerted by rGO, including steady state and time resolved photoluminescence, electron microscopies and electrochemical techniques, in order to evaluate the physical, optical and electrical features involved in determining the catalytic degradation of rhodamine B and phenol in water.Several properties of native ZnO structures were found changed upon the rGO enwrapping (including optical absorbance, concentration of native defects in the ZnO matrix and double-layer capacitance), which are all involved in determining the photocatalytic performance of the hybrid composites. The findings discussed in the present work highlight the high complexity of the field of application of graphene-derivatives as supporters of semiconducting metal oxides functionality, which has to be analyzed through a multi-parametric approach.
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| 21. |
- Li, Bo, et al.
(författare)
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Fabrication and characterization of bioactive zirconia-based nanocrystalline glass-ceramics for dental abutment
- 2021
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:19, s. 26877-26890
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Tidskriftsartikel (refereegranskat)abstract
- Zirconia-based ceramics are becoming a popular biomaterial in dental implantology due to their natural silver-white color, excellent mechanical properties, and good biocompatibility. However, zirconia-based ceramics are biologically inert, which limits their ability to integrate with the surrounding human tissues. To solve this problem, the bioactive elements of calcium (Ca) and phosphorus (P) were doped in high-strength ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs) to overcome the biological inertness of ZrO2-based ceramics. XRD results showed that tetragonal zirconia (t-ZrO2) and monoclinic zirconia (m-ZrO2) were the only two crystalline phases after spark plasma sintering. Ca and P dopants acted as destabilizer of t-ZrO2, enhancing its transformability to m-ZrO2 during sintering. The amount of t-ZrO2 exerted significant effects on the average flexural strength of the NCGCs. The NCGC with 45 mol% ZrO2 were composed of 64.5 vol% t-ZrO2 and 35.5 vol% m-ZrO2 after sintering at 1230 degrees C. And, the average flexural strength and Vickers hardness of the NCGC was 615 MPa and 1049 HV, respectively. In comparison, the NCGC with 65 mol% ZrO2 were composed of 12.6 vol% t-ZrO2 and 87.4 vol% m-ZrO2 after sintering at 1150 degrees C. The average flexural strength and Vickers hardness of the NCGC was 293 MPa and 839 HV, respectively. Interestingly, the NCGCs exhibited a plastic deformation behavior during flexural strength test, which was different from traditional brittle ceramics. The ion release results demonstrated that Ca2+ and Si4+ ions kept on releasing from the surface of the material. The formation of hydroxyapatite in the in-vitro apatite formation test indicated that the NCGCs had good biological activity. The doped ZrO2-based NCGCs combined moderate strength and good bioactivity. Hence, the NCGCs show promising potential to be used in sub-gingival regions, such as dental abutments.
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| 22. |
- Lv, Zhong-Peng, et al.
(författare)
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Impact of the cation field strength on physical properties and structures of alkali and alkaline-earth borosilicate glasses
- 2022
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 48:13, s. 18094-18107
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the cation field strength (CFS) of the glass network-modifier cations on the structure and properties of borosilicate glasses (BS) were examined for a large ensemble of mixed-cation (R/2)M(2)O–(R/2)Na2O–B2O3–KSiO2 glasses with M+ ={Li+, Na+, K+, Rb+} and M2+ ={Mg2+, Ca2+, Sr2+, Ba2+} from four series of {K, R} combinations of K = n(SiO2)/n(B2O3) = {2.0, 4.0} and R =[n(M(2)O) + n(Na2O)]/n(B2O3) = {0.75, 2.1}. Combined with results from La3+ bearing glasses enabled the probing of physical-property variations across a wide CFS range, encompassing the glass transition temperature (Tg), density, molar volume and compactness, as well as the hardness (H) and Young's modulus (E). We discuss the inferred composition–structure/CFS–property relationships. Each of Tg, H, and E revealed a non-linear dependence against the CFS and a strong Tg/H correlation, where each property is maximized for the largest alkaline-earth metal cations, i.e., Sr2+ and Ba2+, along with the high-CFS La3+ species. The 11B MAS NMR-derived fractional BO4 populations decreased linearly with the average Mz+/Na+ CFS within both K–0.75 glass branches, whereas the NBO-rich K–2.1 glasses manifested more complex trends. Comparisons with results from RM2O–B2O3–KSiO2 glasses suggested no significant “mixed alkali effect”.
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| 23. |
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| 24. |
- Mohagheghiyan, Kiana, et al.
(författare)
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Gelatin-coated mesoporous forsterite scaffold for bone tissue engineering
- 2024
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 50:8, s. 13526-13535
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to develop a mesoporous forsterite spheres-based scaffold for bone tissue regeneration. To achieve this goal, mesoporous forsterite spheres were fabricated using alginate (gel-forming agent) and activated charcoal (porogen). The impact of carbon concentration (2, 5, 10, and 20 wt %) and sintering temperature (1100 and 1200 °C) on the structural properties of mesoporous forsterite spheres was investigated. Additionally, gelatin coatings were applied to modify these spheres. Forsterite microspheres with a particle size of 2.43 ± 0.22 mm were successfully produced, exhibiting varying pore sizes based on the sintering temperature and carbon content. Notably, mesoporous forsterite spheres synthesized using 5 wt% carbon and sintered at 1200 °C displayed uniform morphology, a minor average diameter (2.4 ± 0.3 mm(, and an average pore size of 2.7 ± 0.9 μm. These optimized forsterite spheres exhibited mesoporous structures with superior surface area (2.93 m2g-1) and pore volume (0.009–0.048 cm3g-1). Furthermore, the gelatin coating, with an average thickness of 160 μm, was effectively applied to the forsterite spheres. The gelatin coating reduced the surface area (1.40 m2g-1), pore volume (0.003 cm3g-1), and average pore diameter to 9.26 nm, maintaining the mesoporous structure. Both mesoporous forsterite spheres successfully induced bone-like apatite formation in vitro during a 21-day immersion in simulated body fluid. Moreover, while both forsterite-based spheres exhibited cytocompatibility with MG63 cells (cell viability >80 %), the gelatin coating significantly enhanced osteogenic differentiation (1.29 times). In conclusion, gelatin-coated mesoporous forsterite spheres exhibit promising potential as bioactive filling scaffolds for bone tissue regeneration.
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| 25. |
- Mu, Wangzhong, et al.
(författare)
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Phase-field study of dissolution behaviors of different oxide particles into oxide melts
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 46:10, s. 14949-14956
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Tidskriftsartikel (refereegranskat)abstract
- This work utilized a quantitative phase-field model (PFM) to investigate dissolution behaviours of different oxide particles in various slag systems. The simulations could evaluate the influences of temperature, slag viscosity and slag composition on the dissolution time/rate of oxide particle. The simulated results are consistent with reported experimental data. A critical temperature and slag viscosity ratio (T/v), at which the MgAl2O4 and Al2O3 particles have the same dissolution rate, was determined as similar to 1190 [K/Pa's]. It is impossible to get a fixed dissolution time/rate order of different oxide particles in general slag compositions due to the complicated variations of interfacial mobility coefficients. The Al2O3 particle is more sensitive to the variation of MgO and Al2O3 components in slag, compared with the MgAl2O3 particle. When the V-ratio (CaO/SiO2) increases up to a certain degree, the influence of MgO component in both MgAl2O3 and Al2O3 particles becomes minor.
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