共查询到20条相似文献,搜索用时 9 毫秒
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D. E. Andreev V. N. Sanin V. I. Yukhvid A. E. Sytschev 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(2):136-143
Explored was the feasibility of fabricating consolidated elemental blocks (CEBs) Ti-36Al and Ti-29Al-18Nb (wt %) via reactive
sintering for their use as consumable electrodes in vacuum arc melting (VAM). For obtaining strong blocks in the Ti-Al system,
thermal treatment of green mixture must be performed at a temperature not less that 700°C, which is then followed by sintering
at 1100°C. In Nb-containing mixtures, the exothermic effect is less pronounced, so that thermal treatment must be carried
out at 1300°C. The presence of free Al is a prerequisite for reactive sintering. It has been established experimentally that
the Al content of green mixture must be above 10 wt %.
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S. D. Gilev 《Combustion, Explosion, and Shock Waves》2005,41(5):599-609
The electrical conductivity of a series of metal powders under shock compression is measured by an electrocontact technique.
Initially, the metal particles are covered by an oxide film, and the powder is non-conducting. Under shock compression, the
powder acquires macroscopic conductivity. The electrical conductivity of the shock-compressed powder depends substantially
on the metal, porosity, particle size, and shock-wave pressure. The macroscopic electrical conductivity behind the shock-wave
front is uniform within the experimental error. The dependences for fine and coarse aluminum powders on the shock-wave pressure
are found. It is demonstrated that these dependences are nonmonotonic. For high shock-wave pressures, the electrical conductivity
of the substance decreases. This behavior is assumed to be related to strong temperature heating of the substance under shock
compression. Estimates of temperature show that shock compression can induce melting and partial vaporization of the metal.
The same is evidenced by the behavior of electrical conductivity whose value for fine particles is close to the electrical
conductivity of the melt. The electrical conductivity of the coarse powder is heterogeneous because of the strong thermal
nonequilibrium of the particle during shock compression. An analysis of results for different metals shows that the basic
parameter responsible for electrical conductivity of the shock-compressed powder is the dimensionless density.
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Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 128–139, September–October, 2005. 相似文献
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Jihong She Jian-Feng Yang Daniel Doni Jayaseelan Naoki Kondo Tatsuki Ohji Shuzo Kanzaki Yoshiaki Inagaki 《Journal of the American Ceramic Society》2003,86(4):738-40
The thermal shock behavior of isotropic and anisotropic porous Si3 N4 was evaluated using the water-quenching technique. The critical temperature difference for crack initiation was found to be strongly dependent on the ratio of fracture strength to elastic modulus. Because of a very high strain-to-failure, anisotropic porous Si3 N4 showed no macroscopic cracks and was able to retain its strength even at a quenching-temperature difference of ∼1400°C. 相似文献
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Guanxi Liu Zaoyu Shen Guanghong Huang Limin He Rende Mu Wenjun Zhao 《Journal of the American Ceramic Society》2022,105(6):4521-4531
Shot peening might be a potential technology to optimize the interface microstructure, plays a critical role on failure behaviors, of thermal barrier coatings (TBCs). It remains a significant challenge to understand the influence of shot peening on microstructure, oxidation resistance, and thermal shock life. In this work, the Y2O3-stabilized ZrO2 TBCs have been deposited by EB-PVD. The phase, microstructure, thermal performance, and failure mechanism of TBCs have been systemically investigated after shot peening. The shot peening process can improve the planeness of interface and reduce the formation of the cauliflower-liked microstructure in TBCs. After shot peening, the TBC coatings exhibit relatively good isothermal oxidation resistance and high thermal shock life due to the optimization of TGO growth and the thermal stability. The phase transformation, TGO growth, and cracks extension might give rise to the failure of TBCs. This work might guide the investigation of the improvement of interface microstructure and failure behaviors. 相似文献
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以AOD炉用后镁钙砖为原料,配以电熔镁砂合成再生镁钙砖.对其抗热震性能进行测试,并测试了热震前后样品的常温抗折强度,然后对比热震前后样品的微观形貌,从而对再生镁钙砖的抗热震性能进行综合评判.结果表明:MgO质量分数为75%的再生镁钙砖热震后外部形貌较热震前无明显变化,热震20次后,其常温抗折强度为35.80 MPa,依旧保持较好的常温力学性能,但是随着热震次数的增加,样品的常温抗折强度逐渐减小,抗折强度损失率逐渐增大,抗热震性系数逐渐减小,且均呈线性变化,主要是因为样品内部由于热应力产生裂纹,并且裂纹逐渐延展扩大所致. 相似文献
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《硅酸盐学报》2012,40(9)
为了研制一种新型连铸结晶器材料,采用高效能超音速等离子喷涂技术在纯铜基体上制备了 Cr2O3陶瓷涂层。使用 X 射线衍射、扫描电子显微镜、图形软件、彩色 3D 激光显微镜和显微硬度计对涂层进行了表征及分析,分别在 450 ℃和 600 ℃对涂层进行了热震试验。结果表明,涂层继承了起始粉末的物相,但是 Cr2O3的结晶度有所差异;陶瓷涂层表面为良好熔化区和部分熔融颗粒组成的双态组织,涂层断口形貌为典型的片层状组织,涂层截面可见均匀分布的富铬带。涂层孔隙率为 1.2%,表面粗糙度为 4.763 μm,Vickers 显微硬度为 1 628 MPa。试样在 450 ℃和 600 ℃分别经历了均值为 127.4 和 58.6 次热震循环后,其半球顶端出现大面积剥落,但圆柱主体部分完好,表明 Cr2O3陶瓷涂层具备良好的抗热疲劳性能,超音速等离子喷涂适合于结晶器铜板表面涂层的制备。 相似文献
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研究了铝酸钙水泥(CAC)+二氧化硅微粉(MS)结合、水硬性氧化铝(HA)+二氧化硅微粉(MS)结合、二氧化硅溶胶结合的3种结合方式对氮化处理后碳化硅浇注料抗热震性和显微结构的影响。结果显示:3种结合方式制备的试样经600、800和1 100℃水冷1次热震后的残余抗折强度和强度保持率都随着温度的升高而降低,但在1 100℃热震后,3种结合方式的试样的残余抗折强度相当,二氧化硅溶胶结合的浇注料具有较好的抗热震性。分析表明,本试验的3种结合体系中,无水泥结合方式的试样中原位生成的SiAlON具有更大的长径比,特别是纤维状的SiAlON,对高温下结构的保持和抗热震性的提高更为有利。 相似文献
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采用氩气保护、真空熔炼的方法制备了Mg-xLi-3Al-2Zn-0.7Re(x=8~14,wt%)镁锂合金。研究了合金的显微组织及力学性能,结果表明:当锂的含量为12(wt)%时,合金在室温时具有较好的强度和变形能力,具有最佳的综合力学性能。 相似文献
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探究了Mn3O4的微观结构对高温固相法制备类单晶锰酸锂(LiMn2O4)的影响。结果表明,前驱体对LiMn2O4的结构和形貌有决定性的影响。粒度小、比表面积大的类球形Mn3O4更易制得类单晶锰酸锂,其颗粒团聚致密、表面光滑,且晶胞参数小、能量密度大、Li+浓度高。类单晶锰酸锂的综合电化学性能和热稳定性远高于非类单晶材料,在0.2 C倍率下首次放电比容量和库仑效率分别高达112.50 mA·h/g、96.5%,8 C倍率下放电比容量仍有102.11 mA·h/g,200次循环后容量保持率为90.1%。类单晶锰酸锂优异的性能归因于其具有稳定的晶体结构和外露表面、较高的Li+浓度,在电化学反应中结构稳定、锂离子迁移速率快、电极极化和电荷转移阻抗小。 相似文献
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窑具材料显微结构与热震稳定性相关性研究 总被引:6,自引:1,他引:5
本文分析了影响窑具材料热震稳定性的重要参数,找出显微结构与这些因素的内在联系,表明通过调整显微结构可获得良好的材料性能。 相似文献
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以烧结镁砂和单斜氧化锆粉为原料,进行了Mg O-Zr O2复合材料的制备。通过XRD和SEM-EDS分析及显气孔率、体积密度、常温抗折强度、线膨胀系数和1100℃~室温水冷热震稳定性的测试,探讨了Zr O2的用量对Mg O-Zr O2复合材料的烧结和热震稳定性的影响。结果表明:随着Zr O2用量的增加,复合材料试样的致密度和常温抗折强度呈现出先增大后减小的趋势,复合材料试样的热膨胀系数逐步减小,复合材料试样的热震稳定性呈现出先变好后变差的趋势;当Zr O2用量为30%时,Mg O-Zr O2复合材料试样的烧结性能和热震稳定性最好。 相似文献
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Michael R. Wixom 《Journal of the American Ceramic Society》1990,73(7):1973-1978
Two synthetic routes have been developed to produce high-molecular-weight organic precursors containing a high weight fraction of nitrogen. One of the precursors is a pyrolysis residue of melamine-formaldehyde resin. The second precursor is the byproduct of an unusual low-temperature combustion reaction of tetrazole and its sodium salt. These precursors have been shock compressed under typical conditions for diamond and wurtzite boron nitride synthesis in an attempt to recover a new ultrahard carbon nitride. The recovered material has been analyzed by X-ray diffraction, FTIR, and Raman microprobe analysis. Diamond is present in the recovered material. This diamond is extraordinarily well ordered relative to diamond shock synthesized from carbonaceous starting materials. 相似文献
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R-Curve Behavior and Thermal Shock Resistance of Ceramics 总被引:3,自引:0,他引:3
Michael V. Swain 《Journal of the American Ceramic Society》1990,73(3):621-628
The influence of R -curve behavior of ceramics on the strength degradation associated with thermal shock is explored. Of particular significance for this interdependence is the observed nonlinear stress-strain behavior of materials that exhibit minimal strength degradation under severe thermal shock conditions. These two features, R -curve behavior and nonlinear behavior, are incorporated into a fracture mechanics analysis to provide a framework with which to understand severe thermal shock of ceramics. This analysis enables the estimation of the crack growth due to thermal shocking and also the anticipated strength degradation. The influence of specimen size is also addressed, and it is shown that greater strength degradation is anticipated with increasing specimen size. Experimental results for an alumina-zirconia composite material are presented to support the simple analysis. 相似文献