| 141. |
- Thörnberg, Jimmy, et al.
(författare)
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Microstructure and materials properties of understoichiometric TiBx thin films grown by HiPIMS
- 2020
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 404
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Tidskriftsartikel (refereegranskat)abstract
- TiBx thin films with a B content of 1.43 <= x <= 2.70 were synthesized using high-power impulse magnetron sputtering (HiPIMS) and direct-current magnetron sputtering (DCMS). HiPIMS allows compositions ranging from understoichiometric to overstoichiometric dense TiBx thin films with a B/Ti ratio between 1.43 and 2.06, while DCMS yields overstoichiometric TiBx films with a B/Ti ratio ranging from 2.20 to 2.70. Excess B in overstoichiometric TiBx thin films from DCMS results in a hardness up to 37.7 +/- 0.8 GPa, attributed to the formation of an amorphous B-rich tissue phase interlacing stoichiometric TiB2 columnar structures. We furthermore show that understoichiometric TiB1.43 thin films synthesized by HiPIMS, where the deficiency of B is found to be accommodated by Ti-rich planar defects, exhibit a superior hardness of 43.9 +/- 0.9 GPa. The apparent fracture toughness and thermal conductivity of understoichiometric TiB1.43 HiPIMS films are 4.2 +/- 0.1 MPa root m and 2.46 +/- 0.22 W/(m.K), respectively, as compared to corresponding values for overstoichiometric TiB2.70 DCMS film samples of 3.1 +/- 0.1 MPa root m and 4.52 +/- 0.45 W/(mK). This work increases the fundamental understanding of understoichiometric TiBx thin films and their materials properties, and shows that understoichiometric films have properties matching or going beyond those with excess B.
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| 142. |
- Thörnberg, Jimmy, et al.
(författare)
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Oxidation resistance and mechanical properties of sputter-deposited Ti0.9Al0.1B2-y thin films
- 2022
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Ingår i: Surface & Coatings Technology. - : Elsevier Science SA. - 0257-8972 .- 1879-3347. ; 442
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Tidskriftsartikel (refereegranskat)abstract
- Direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) were used to deposit understoichiometric Ti(1-x)Al(x)B(2-y )diboride coatings by sputtering from a segmented TiB2-AlB2 target using Ar and Kr as sputtering gas. For films with a fixed Al/(Ti + Al) ratio of x = 0.1 (Ti0.9Al0.1B2-y), the B content was varied with y & ISIN; (0.1, 0.6 and 0.7). For films with a fixed y = 0.7 (Ti1-xAlxB1.3), the Al content was varied with x & ISIN; (0.1, 0.4 and 0.7). Evaluation of the mechanical properties of the Ti1-xAlxB1.3 samples showed a reduction in both hardness and elastic modulus with increasing Al concentration, while the Ti0.9Al0.1B2-y samples showed a hardness increase with decreasing B content. Thus, Ti0.9Al0.1B1.3 films exhibited a superior hardness of 46.2 +/- 1.1 GPa and an elastic modulus of 523 & PLUSMN; 7 GPa, compared to the values for Ti0.9Al0.1B1.4 and Ti0.9Al0.1B1.9, showing a hardness of 44 +/- 1 GPa and 36 +/- 1 GPa, and an elastic modulus of 569 +/- 7 GPa and 493 +/- 6 GPa, respectively. The oxidation behavior of the mechanically most promising Ti0.9Al0.1B2-y sample series was investigated through air-annealing at 600 C for durations from 1 h to 10 h. All films formed a mixed non-conformal Al2O3-TiO2 oxide scale which acts as an inward and outward diffusion barrier, significantly reducing the oxidation rate compared to TiBz films, which form an oxide scale consisting of porous TiO2. The thinnest oxide scale after 10 h was found in the B-deficient samples, Ti0.9Al0.1B1.3 and Ti0.9Al0.1B1.4, at ~200 nm, which is significantly below that for Ti0.9Al0.1B1.9 at 320 nm. The enhanced oxidation resistance of highly understoichiometric films is due to the elimination of the B-rich tissue phase that is present at the grain boundaries for higher B content, where the latter has been shown to enhance the rate of oxidation in borides.
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| 143. |
- Thörnberg, Jimmy, et al.
(författare)
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Synthesis of (V2/3Sc1/3)(2)AlC i-MAX phase and V2-xC MXene scrolls
- 2019
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 11:31, s. 14720-14726
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and characterization of a new laminated i-MAX phase, (V2/3Sc1/3)(2)AlC, with in-plane chemical ordering between the M-elements. We also present evidence for the solid solution (V2-xScx)(2)AlC, where x amp;lt;= 0.05. Chemical etching of the Al and Sc results in a two-dimensional (2D) MXene counterpart: V2-xC from the latter phase. Furthermore, etching with HF yields single-sheet MXene of flat morphology, while LiF + HCl gives MXene scrolls. We also show a 4x reduction in etching time for (V2-xScx)(2)AlC compared to V2AlC, suggesting that traces of Sc changes the phase stability, and make the material more susceptible to etching. The results show a path for improved control of MXene synthesis and morphology, which may be applicable also for other MAX/MXene systems.
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| 144. |
- Wongpanit, N., et al.
(författare)
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Etching behaviors of tunneling magnetoresistive (TMR) materials by ion beam etching system
- 2018
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Ingår i: MATERIALS TODAY-PROCEEDINGS. - : ELSEVIER SCIENCE BV. ; , s. 15186-15191
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Konferensbidrag (refereegranskat)abstract
- In data storage manufacturing, ion etching process is commonly chosen for the preparation of surface patterns, for example, under the read-write head of the hard disk drive (HDD) to form an air bearing surface (ABS). This read-write head consists of a multilayer thin film of different materials to form a tunneling magnetoresistive (TMR) device. In this work, we applied the Monte Carlo-based simulation package to calculate the etching yield of major materials in the HDD heads structure. The plasma characteristic in the industrial-size ion beam etching (IBE) system has been studied by the special plasma diagnostic probes. Effects of input parameters in IBE system such as incident beam angle, ion beam current and gas flow in the system were considered. Plasma characteristic can be obtained from plasma I-V curve characterization. The sputtering yields of materials were found maximum when an incident angle is about 70 degrees to the normal surface. The floating potential of plasma in the system with the ion/electron compensation from PBN is calculated. (C) 2018 Elsevier Ltd. All rights reserved.
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| 145. |
- Xie, Mengyao, et al.
(författare)
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Assessing structural, free-charge carrier, and phonon properties of mixed-phase epitaxial films: The case of InN
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 90:19, s. 195306-
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Tidskriftsartikel (refereegranskat)abstract
- We develop and discuss appropriate methods based on x-ray diffraction and generalized infrared spectroscopic ellipsometry to identify wurtizte and zinc-blende polymorphs, and quantify their volume fractions in mixed-phase epitaxial films taking InN as an example. The spectral signatures occurring in the azimuth polarization (Muller matrix) maps of mixed-phase epitaxial InN films are discussed and explained in view of polymorphism (zinc-blende versus wurtzite), volume fraction of different polymorphs and their crystallographic orientation, and azimuth angle. A comprehensive study of the structural, phonon and free electron properties of zinc-blende InN films containing inclusions of wurtzite InN is also presented. Thorough analysis on the formation of the zinc-blende and wurtzite phases is given and the structural evolution with film thickness is discussed in detail. The phonon properties of the two phases are determined and discussed together with the determination of the bulk free-charge carrier concentration, and electron accumulation at the mixed-phase InN film surfaces.
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| 146. |
- Zhang, Silan, et al.
(författare)
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Synergistic Effect of Multi-Walled Carbon Nanotubes and Ladder-Type Conjugated Polymers on the Performance of N-Type Organic Electrochemical Transistors
- 2022
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 32:1
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Tidskriftsartikel (refereegranskat)abstract
- Organic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p-type (semi-)conducting polymers as the channel material, while n-type OECTs are yet at an early stage of development, with the best performing electron-transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi-walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder-type π-conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n-type OECTs with record-high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high μC* (electron mobility × volumetric capacitance) of about 1 F cm−1 V−1 s−1. This enables the development of complementary inverters with a voltage gain of >16 and a large worst-case noise margin at a supply voltage of <0.6 V, while consuming less than 1 µW of power.
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| 147. |
- Zheng, Wei, et al.
(författare)
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Flexible Free-Standing MoO3/Ti3C2Tz MXene Composite Films with High Gravimetric and Volumetric Capacities
- 2021
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Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Enhancing both the energy storage and power capabilities of electrochemical capacitors remains a challenge. Herein, Ti3C2Tz MXene is mixed with MoO3 nanobelts in various mass ratios and the mixture is used to vacuum filter binder free, open, flexible, and free-standing films. The conductive Ti3C2Tz flakes bridge the nanobelts, facilitating electron transfer; the randomly oriented, and interconnected, MoO3 nanobelts, in turn, prevent the restacking of the Ti3C2Tz nanosheets. Benefitting from these advantages, a MoO3/Ti3C2Tz film with a 8:2 mass ratio exhibits high gravimetric/volumetric capacities with good cyclability, namely, 837 C g−1 and 1836 C cm−3 at 1 A g−1 for an ≈ 10 µm thick film; and 767 C g−1 and 1664 C cm−3 at 1 A g−1 for ≈ 50 µm thick film. To further increase the energy density, hybrid capacitors are fabricated with MoO3/Ti3C2Tz films as the negative electrodes and nitrogen-doped activated carbon as the positive electrodes. This device delivers maximum gravimetric/volumetric energy densities of 31.2 Wh kg−1 and 39.2 Wh L−1, respectively. The cycling stability of 94.2% retention ratio after 10 000 continuous charge/discharge cycles is also noteworthy. The high energy density achieved in this work can pave the way for practical applications of MXene-containing materials in energy storage devices.
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| 148. |
- Zhu, Baiwei, 1990-, et al.
(författare)
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A study of formation and growth of the anodised surface layer on cast Al-Si alloys based on different analytical techniques
- 2016
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 101, s. 254-262
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to investigate the mechanisms of formation and growth of the anodised surface layer on Al-Si castings by applying different analytical techniques such as optical microscopy, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and X-ray computer tomography (X-ray CT) scanning. Three different Al alloys with various Si content (2.43%, 3.53% and 5.45%) were investigated. Si particle morphological modification by Sr addition, as well as directional solidification, was used to vary the microstructural coarseness in a controlled manner to study the influence of these parameters on the growth behaviour of the oxide layer. This study observed residual unanodised Al phases trapped beneath or between Si particles in the oxide layer. It was found, depending on the geometry and morphology of Si particles, that Al can be shielded by Si particles and prevented from oxidising.
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