Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
94,561
result(s) for
"powders"
Sort by:
Enhanced phase transformation properties of VO.sub.2 powder by Ti doping
Vanadium dioxide (VO.sub.2) exhibits remarkable properties during its metal-insulator transition, making it a compelling material for smart windows applications as a thermochromic material. In this study, Ti-doped VO.sub.2(M) (Ti-VO.sub.2(M)) powders were synthesized using the hydrothermal method by mixing VOC.sub.2O.sub.4·5H.sub.2O/Ti(SO.sub.4).sub.2 at 50 and 60 °C, respectively. To comparatively analyze the crystalline microscopic morphology and phase transition properties of the synthesized Ti-doped VO.sub.2(M) powders, several characterization techniques were employed, including XRD, XPS, SEM/TEM, EDS, and DSC. The experimental results suggests that low mixing temperature is beneficial for the stable and homogeneous growth of VO.sub.2(M) grains when in the absence of Ti doping. On the other hand, high mixing temperatures are beneficial for the stable and homogeneous growth of VO.sub.2(M) grains when Ti(SO.sub.4).sub.2 is introduced, resulting in enhanced phase transition stability of Ti-VO.sub.2(M).
Journal Article
Synthesis of Submicron-Sized TiBsub.2 Powders by Reaction of TiC, Bsub.4C, and Ca in Molten CaClsub.2
Submicron-sized TiB[sub.2] powders (300 nm–1 μm) were prepared by the reaction of TiC, B[sub.4]C, and Ca assisted by molten CaCl[sub.2]. The optimal reaction procedure (1200 °C and 25 wt.% CaCl[sub.2] + 25 wt.% Ca) was obtained by exploring the effects of the boronization reaction temperature and the addition of an amount of CaCl[sub.2]. It was found that the introduction of CaCl[sub.2] not only promoted the reaction but also effectively inhibited the volatilization of excess Ca. Furthermore, SEM images of the products showed that the morphology and particle size of TiB[sub.2] were inherited from the carbothermal reduction product TiC, which was dominated by the “template/growth” mechanism. The process of the boronization reaction was that B atoms migrated from B[sub.4]C and replaced the C atoms in the lattice of TiC.
Journal Article
Synthesis Strategy Toward Minimizing Adventitious Oxygen Contents in the Mechanochemically Made Semiconductor Kesterite Cusub.2ZnSnSsub.4 Nanopowders
A multipronged approach to the refined mechanochemical synthesis of the semiconductor kesterite Cu[sub.2]ZnSnS[sub.4] with minimal quantities of adventitious oxygen as well as to optimizing handling procedures from that angle is described. Three precursor systems are used to provide a pool of freshly made cubic prekesterite nanopowders with no semiconductor properties and the thermally annealed at 500 °C tetragonal kesterite nanopowders of the semiconductor. Based on the previously reported high propensity of such nanopowders to long-term deteriorating oxidation in ambient air, suitable modifications of all crucial synthesis steps are implemented, which are directed toward excluding or limiting the materials’ exposure to air. The nanopowders are comprehensively characterized by powder XRD, FT-IR/Raman/UV-Vis spectroscopies, solid-state [sup.65]Cu/[sup.119]Sn MAS NMR, TGA/DTA-QMS analysis, SEM, BET/BJH specific surface area, and helium density determinations, and, significantly, are directly analyzed for oxygen and hydrogen contents. The important finding is that following the anaerobic procedures and realistically minimizing the materials’ exposure to air in certain manipulation steps results in the preparation of better oxidation-resistant nanopowders with a dramatic relative decrease in their oxygen content than previously reported. The adherence to the strict synthesis conditions that limit contact of the no-oxygen-containing kesterite nanopowders with ambient air is emphasized.
Journal Article
The Influences of Ultrasonic Vibrations on Laser Cladding Ni60/WC-TiOsub.2+Lasub.2Osub.3 Composite Coating
The optimal process parameters of ultrasonic-assisted processing were studied to further improve the molding quality and mechanical properties of Ni60/WC-TiO[sub.2]+La[sub.2]O[sub.3] composite coating. A single-factor experiment was used to explore the influences of ultrasonic vibration frequencies on Ni60/WC-TiO[sub.2]+La[sub.2]O[sub.3] composite coating. The microstructure, elemental composition, phase composition, hardness, and wear resistance of the coating were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), an energy spectrometer, a microhardness meter, a friction and wear tester, and other equipment. Ultrasonic vibrations significantly improved the problems of pores in the coating, and the porosity was reduced from 0.13 to 0.014%. When the vibration frequency was 32 kHz in the experiment, the aspect ratio of the coating was optimized from 2.06 to 2.48, the dilution rate increased from 5.60 to 5.79%, the hardness increased from 960.25 to 988.45 HZ[sub.1.0], and the friction coefficient was reduced from 0.34 to 0.27. The coating performance was significantly improved, and the research results provide a reference for preparing excellent Ni60/WC-TiC+La[sub.2]O[sub.3] composite coating.
Journal Article
Color Tunable Composite Phosphor Ceramics Based on SrAlSiNsub.3:Eusup.2+/Lusub.3Alsub.5Osub.12:Cesup.3+ for High-Power and High-Color-Rendering-Index White LEDs/LDs Lighting
Lu[sub.3]Al[sub.5]O[sub.12]:Ce[sup.3+] phosphor ceramics were fabricated by vacuum sintering. On this basis, a bi-layer composite phosphor was prepared by low-temperature sintering to cover the phosphor ceramics with a layer of SrAlSiN[sub.3]:Eu[sup.2+]-phosphor-in-glass (PiG). The optical, thermal, and colorimetric properties of LuAG:Ce[sup.3+] phosphor ceramics, SrAlSiN[sub.3]:Eu[sup.2+] phosphors and SrAlSiN[sub.3]:Eu[sup.2+]-PiG were studied individually. Combining the bi-layer composite phosphors with the blue LED chip, it is found that the spectrum can be adjusted by varying the doping concentration of SrAlSiN[sub.3]:Eu[sup.2+]-PiG and the thickness of Lu[sub.3]Al[sub.5]O[sub.12]:Ce[sup.3+] phosphor ceramics. The maximal color rendering index value of the white LED is 86, and the R9 is 61. Under the excitation of a laser diode, the maximum phosphor conversion efficacy of the bi-layer composite phosphors is 120 lm/W, the R[sub.a] is 83, and the correlated color temperature is 4534 K. These results show that the bi-layer composite phosphor ceramic is a candidate material to achieve high color rendering index for high brightness lighting.
Journal Article
Low-Temperature Fabrication of Plate-like α-Alsub.2Osub.3 with Less NHsub.4F Additive
Fluorinated compounds are effective mineralization agents for the fabrication of plate-like α-Al[sub.2]O[sub.3]. However, in the preparation of plate-like α-Al[sub.2]O[sub.3], it is still an extremely challenging task to reduce the content of fluoride while ensuring a low synthesis temperature. Herein, oxalic acid and NH[sub.4]F are proposed for the first time as additives in the preparation of plate-like α-Al[sub.2]O[sub.3]. The results showed that plate-like α-Al[sub.2]O[sub.3] can be synthesized at a low temperature of 850 °C with the synergistic effect of oxalic acid and 1 wt.% NH[sub.4]F. Additionally, the synergistic effect of oxalic acid and NH[sub.4]F not only can reduce the conversion temperature of α-Al[sub.2]O[sub.3] but also can change the phase transition sequence.
Journal Article
Preparation and Characterization of Co-CuCoMnOsub.x Solar Selective Absorption Coatings
The Co-CuCoMnO[sub.x] coatings with varying proportions were prepared and investigated to develop a novel metal–ceramic solar selective absorption coating employed at high temperature. The CuCoMnO[sub.x] powders were synthesized using the solid-phase reaction method. Subsequently, Co-CuCoMnO[sub.x] coatings were deposited on the surface of 316L steels utilizing the atmospheric plasma spraying (APS) technique. The results showed that the synthesized CuCoMnO[sub.x] powders were mainly composed of two phases, which were Cu[sub.1.5]Mn[sub.1.5]O[sub.4] and MnCo[sub.2]O[sub.4]. The CuCoMnO[sub.x] powders had a solar absorptance of 0.929 and an infrared emittance of 0.862, which was considered a good solar absorbent. The synthesized Co-CuCoMnO[sub.x] coating had a typical thermal spray layered stacking structure. The chemical phases of the coatings were mainly Co, CoO, and CoCuMnO[sub.x]. Due to the addition of CuCoMnO[sub.x] inhibiting the oxidation of Co during the thermal spraying process, the 95Co-5CuCoMnO[sub.x] (wt%) coating exhibited the optimal quality factor (α/ε) of 2.184, with a solar absorptance α of 0.808 and an infrared emittance ε of 0.370, respectively. Moreover, this specific coating demonstrated a good thermal stability for up to 3 h when exposed to an atmospheric environment at 450 °C. The results indicate its significant potential for high-temperature solar selective absorption coating.
Journal Article