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941.
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945.
强烈塑性变形可以用于制备超细晶金属材料,超细晶金属材料一个典型的特性是具有高应变率和/或低温超塑性。介绍利用强烈塑性变形研制超塑铝、镁合金的研究近况,并对强烈塑性变形超塑材料的研究进行展望。 相似文献
946.
SiCp/ZL109复合材料摩擦磨损性能研究 总被引:1,自引:0,他引:1
以探讨SiCp增强颗粒对SiCp/Al复合材料摩擦磨损机理的影响为目的,采用搅拌铸造法制备SiCp/ZL109复合材料并进行摩擦磨损性能测试。通过SEM微观形貌观察及能谱分析等手段研究材料摩擦性能及机制,结果表明:添加SiCp增强颗粒能够有效地改善基体材料硬度和耐磨性,提高基体材料的摩擦因数;复合材料的磨损机制为粘着磨损、氧化磨损和磨料磨损的混合型磨损;SiCp在材料的磨损过程中起双重作用,在破碎前保护基体,减少基材粘着磨损;破碎后产生硬质点,对基体造成磨料磨损。 相似文献
947.
Santanu Mondal Andriy Durygin Vadym Drozd Jose Belisario Zhe Cheng 《Journal of the American Ceramic Society》2020,103(9):4876-4893
In this research, near fully dense single phase bulk multicomponent transition metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ has been successfully synthesized from mixed commercial powders of NbN, TaN and TiN via reaction flash sintering technique. This was performed with an applied pressure of ~ 35 MPa at 25°C under a constant DC electric field (~24-32 V/cm). The flash event, which is the abrupt increase in current (up to ~ 25.2 A/mm2) and temperature, occurred without preheating. The threshold power dissipation on the sample right before the flash is ~ 0.7 W/mm3. The formation of single phase (Nb1/3Ta1/3Ti1/3)N1−δ random solid solution and its compositional uniformity were confirmed by XRD and EDS, respectively. The effects of ball milling duration and limiting current density on phase formation were studied. Simulation based on Joule heating provides an estimate of the ultimate sample temperature of ~ 1850°C. Vickers hardness of the obtained (Nb1/3Ta1/3Ti1/3)N1−δ is 17.6 ± 0.6 GPa, which is comparable to similarly flash sintered ingredient binary nitrides of TaN and NbN. TGA in air shows that the oxidation resistance of (Nb1/3Ta1/3Ti1/3)N1−δ is better than that of TaN and NbN but inferior to TiN. The study demonstrates that reaction flash sintering can be a highly efficient technique for synthesizing bulk multicomponent ceramics for both material fundamental investigations and application development. 相似文献
948.
Weide Wang Dongxu Yao Hanqin Liang Yongfeng Xia Kaihui Zuo Jinwei Yin Yu-Ping Zeng 《Journal of the American Ceramic Society》2020,103(10):5567-5572
A two-step sintering process was conducted to produce β-Si3N4 ceramics with high thermal conductivity. During the first step, native SiO2 was eliminated, and Y2O3 was in situ generated by a metal hydride reduction process, resulting in a high Y2O3/SiO2 ratio. The substitution YH2 for Y2O3 endow Si3N4 ceramics with an increase of 29% in thermal conductivity from 95.3 to 123 W m−1 K−1 after sintered at 1900°C for 12 hours despite an inferior sinterability. This was primarily attributed to the purified enlarged grains, devitrified grain boundary phase, and reduced lattice oxygen content in the YH2-MgO-doped material. 相似文献
949.
Shengqiang Liu Shiyou Zhang Ning Mao Zhen Song Quanlin Liu 《Journal of the American Ceramic Society》2020,103(12):6793-6800
Broadband near-infrared (NIR) phosphors have received increasing attention for fabricating phosphor-converted light-emitting diodes (pc-LEDs) as NIR light source. Most of the reported broadband NIR phosphors originate from Cr3+ in weak crystal field environments. Herein, we report a luminescent material, MgAlSiN3:Mn2+ with CaAlSiN3-type structure, demonstrating that broadband deep-red-to-NIR emission can be achieved via doping Mn2+ into crystallographic sites with strong crystal field in inorganic solids. This phosphor is synthesized via easy-handle solid-state reaction, and the optimized sample, (Mg0.93Mn0.07) AlSiN3 shows an emission band with peak at ~754 nm, FWHM of 150 nm, and internal quantum efficiency of 70.1%. The photoluminescence intensity can further be enhanced by co-doping Eu2+ as sensitizer. This work provides a new strategy for discovering new broadband NIR phosphors using Mn2+ in strong crystal field as luminescence center. 相似文献
950.
Boron nitride-reinforced polysilazane-derived ceramic composites via direct-ink writing 总被引:1,自引:0,他引:1
James W. Kemp Nadim S. Hmeidat Brett G. Compton 《Journal of the American Ceramic Society》2020,103(8):4043-4050
In this study we investigate the use of hexagonal boron nitride (hBN) as a rheology modifier in polysilazane resin to enable direct-ink writing (DIW) of polysilazane-derived boron nitride-reinforced ceramic composites. hBN is shown to effectively modify the flow properties of the resin by imparting strong shear thinning and yield stress behavior, and to reduce the mass loss and shrinkage associated with the polymer-to-ceramic conversion process, when compared with unfilled polysilazane resin. DIW inks are formulated with 40 vol.% hBN and used print flexural specimens and complex structures with high resolution. Mechanical properties of the resulting polymer-derived ceramic composites were evaluated by 3-pt. flexure and Vickers microhardness. The printed composites exhibit flexural strength of 56.4 MPa and microhardness of 111.4 HV2. 相似文献