共查询到20条相似文献,搜索用时 328 毫秒
1.
2.
以不同粒径和含量的cBN在六面顶压机中高温高压制备了Si3N4/cBN复合材料.观察了样品的微观形貌、β-Si3N4含量,测试了抗弯强度和密度.结果发现,cBN颗粒形貌和分布状态对β-Si3N4颗粒生长有很大影响,cBN含量在一定范围内,随着cBN粒径的减小,试样的密度和抗弯强度增大.cBN含量达到70;时,由于出现大量“搭桥”结构,影响断面上的正应力和剪力,结果使材料抗弯强度减小.同时“搭桥”结构不利于试样的致密.实验结果对新型刀具材料Si3N4/cBN有指导意义. 相似文献
3.
以CeO2作为烧结助剂,采用高温(1700℃)、高压(5 GPa)烧结,制备出β-Sialon-cBN陶瓷基复合材料,观察了样品的断面微观形貌,并测试了样品的气孔率、密度,抗弯强度和硬度.研究了不同百分含量的CeO2对β-Sialon-cBN复合材料的显微结构和相关力学性能的影响.结果表明:随着烧结助剂CeO2的加入,促进了β-Sialon与cBN之间的界面结合,β-Sialon长径比提高.结果增强了β-Sialon-cBN复合材料的致密性,使复合材料的抗弯强度和硬度增大. 相似文献
4.
采用Co包覆Al2O3/TiC微米级、纳米级粉料进行了不同Co含量、不同烧结温度的热压烧结实验.综合分析和对比了两种不同粒径包覆粉体的烧结结果,结果发现纳米级的粉体烧结效果优于微米级粉体的烧结效果.综合力学性能最佳的纳米级复相陶瓷材料的硬度为HRA92.7,抗弯强度σf为782 Mpa,断裂韧性KIC为7.81 Mpa·M1/2.利用SEM观察采取综合力学性能最佳的ATC纳米复合材料制备工艺制备的Al2O3、Al2O3/TiC和ATC的断口,可以看出Al2O3、Al2O3/TiC主要以沿晶断裂为主,而ATC为沿晶与穿晶混合断口,并从ATC断口,发现形成了晶内型结构,观察到了裂纹曲折的扩展路径以及裂纹的分叉、偏转、桥联这些有助于材料强度和韧性提高的现象. 相似文献
5.
首先采用机械合金化的方法制备出TiAl金属间化合物,用化学沉淀法制备出HA粉体,然后将二者球磨混合,经过真空热压烧结工艺制得TiAl/HA复合材料.力学性能检测结果表明,TiAl/HA复合材料的硬度比纯HA生物陶瓷要低,并且随TiAl质量分数的增加呈现降低趋势;复合材料的抗弯强度随着TiAl金属间化合物含量的增加呈上升趋势,含量为15;以下,其强度低于纯羟基磷灰石,含量处于15;到30;之间,其强度高于纯羟基磷灰石;断裂韧性高于纯HA生物陶瓷,最高可比纯羟基磷灰石提高78.7;,并且随着TiAl质量分数的增加呈上升趋势.X射线衍射结果表明复合材料中只含有TiAl金属间化合物和HA两种成分;断口扫描电镜照片显示,纯羟基磷灰石材料比较致密,而复合材料中存在一定量的气孔,其部分断裂区域显示出穿晶断裂的形态. 相似文献
6.
以Li3N为触媒,采用静态高压法合成了大颗粒立方氮化硼单晶.以扫描电镜(SEM)观察了快冷后的的立方氮化硼(cBN)合成块的断口形貌,并利用X射线衍仪(XRD)对cBN晶体附近的物质分层进行了表征.扫描结果显示,cBN处于熔融状物质的包裹之中,并在cBN的裸表面发现了生长台阶及近似熔入台阶中的颗粒状物质;XRD分层表征结果表明,cBN晶体表面分层界面中检测出含有中间相Li3BN2和cBN小颗粒.由此推断,高温高压下Li3N可以与hBN发生共熔反应并转变为中间相Li3BN2;根据分层表征结果可推测,在适量中间相Li3BN2存在的区域cBN小颗粒更易于聚集并通过不断消耗扩散到大颗粒cBN晶体表面的cBN小颗粒的方式不断长大. 相似文献
7.
8.
Al2O3/(W,Ti)C纳米复合陶瓷材料的显微结构 总被引:1,自引:0,他引:1
使用纳米、亚微米级的α-Al2O3粉体和微米级的(W,Ti)C粉体为原料,采用热压烧结工艺制备了Al2O3/(W,Ti)C纳米复合陶瓷材料.对热压后材料的硬度、断裂韧性和抗弯强度进行了测试和分析,利用透射电镜、扫描电镜及X衍射仪对Al2O3/(W,Ti)C纳米复合陶瓷材料的微观组织和结构进行了研究.结果表明,增强相(W,Ti)C与基体Al2O3互相穿插、包裹,界面结合良好,形成了典型的骨架结构;球磨后的(W,Ti)C颗粒粒度分布广泛,热压烧结后与基体材料形成了内晶/晶间型结构;断裂模式的改变、内部残余应力场、位错机制、裂纹分叉和偏转等促进了材料强度和韧性的提高. 相似文献
9.
通过机械激活法制备了Al2TiO5/Al2O3(nAl2TiO5: nAl2O3=1: 4)的陶瓷复合材料.利用X射线衍射(XRD)、扫描电镜(SEM)以及能谱(EDS)分析了不同的温度制度下Al2TiO5/Al2O3陶瓷复合材料的晶粒生长特性.X射线衍射谱图(XRD)显示烧结样品的主晶相为α-Al2O3和Al2TiO5.SEM和EDS分析显示,较低温度下烧结(1350 ℃)时Al2TiO5晶粒为等轴状.当温度升高到1450 ℃时,Al2TiO5开始异向长大,形成棒状晶粒.随着温度的升高(1500 ℃),棒状Al2TiO5的长径比继续增加.而Al2O3则始终为片状和等轴晶粒,且异向生长的Al2TiO5晶粒填充于Al2O3三角晶界处.研究表明,烧结温度的升高会促进晶体异向生长并增加其体积分数.Al2TiO5会阻碍Al2O3基体颗粒进一步生长,所以当Al2TiO5颗粒平均尺寸随着烧结温度增加而增大,Al2O3基体晶粒生长几乎停滞. 相似文献
10.
11.
Calculation of phase diagrams in AlxIn1−xAs/InP,AsxSb1−xAl/InP and AlxIn1−xSb/InSb nano-film systems
The models for calculation of phase diagrams of semiconductor thin films with different substrates were proposed by considering the contributions of strain energy, the self-energy of misfit dislocations and surface energy to Gibbs free energy. The phase diagrams of the AlxIn1−xAs and AsxSb1−xAl thin films grown on the InP (1 0 0) substrate, and the AlxIn1−xSb thin films grown on the InSb (1 0 0) substrate at various thicknesses were calculated. The calculated results indicate that when the thickness of film is less than 1 μm, the strain-induced zinc-blende phase appears, the region of this phase extends with decreasing of the layer thickness, and there is small effect of surface energies of liquid and solid phases on the phase diagrams. 相似文献
12.
The elastic properties of GexAsySe100−x−y (0x30; 10y40) glasses have been studied. The results were analyzed in terms of the dependence on the theoretical mean coordination number (mean number of covalent bonds per atom) m (m=2+(2x+y)×0.01). Three ranges of m (2.1m2.51, 2.51<m2.78, 2.78<m3) were revealed, where different dependencies of elastic moduli (Young’s modulus, shear modulus) and Poisson’s ratio of glasses on m were observed. 相似文献
13.
14.
15.
NdAl3(BO3)4 single crystals were grown by the flux method and the TSSG technique using a K2O/3MoO3/B2O3/0.5Nd2O3/KF flux system. Light-violet clear crystals could be obtained. The effects of fluoride on the growth of NAB crystals were investigated. As the content of KF was gradually increased, the growth form of NAB was changed from the equant to the columnar and the primary crystalline region of NAB was shrinked. At the ratio of KF/K2O = 0.75, NAB crystals could not be grown. 相似文献
16.
G. A. Geguzina A. T. Shuvaev E. T. Shuvaeva L. A. Shilkina V. G. Vlasenko 《Crystallography Reports》2005,50(1):52-57
Three polycrystalline bismuth-containing layered perovskite-like oxides are synthesized by high-temperature solid-state reactions.
One of these compounds was described previously, namely, Bi3Ti1.5W0.5O9, for which the unit cell parameters a = 5.372(5) Å, b = 5.404(4) Å, and c = 24.95(2) Å are determined in this study. The other two compounds, namely, Na0.75Bi2.25Nb1.5W0.5O9 with the unit cell parameters a = 5.463(1) Å, b = 5.490(7) Å, and c = 24.78(0) Å and Ca0.5Bi2.5Ti0.5Nb1.5O9 with the unit cell parameters a = b = 3.843(2) Å and c = 24.97(6) Å, are synthesized for the first time. The compositions of these compounds are based on the composition of the
well-known compound Bi3TiNbO9 with a high Curie temperature (T
C = 1223 K), in which bismuth, niobium, and titanium atoms are partially or completely replaced by other atoms. The experimental
and calculated interplanar distances determined from the X-ray diffraction patterns of the studied compounds are presented.
__________
Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 59–64.
Original Russian Text Copyright ? 2005 by Geguzina, Shuvaev, Shuvaeva, Shilkina, Vlasenko. 相似文献
17.
18.
Suk Choi Hee Jin KimJae-Hyun Ryou Russell D. Dupuis 《Journal of Crystal Growth》2009,311(12):3252-3256
We propose a new growth scheme of digitally alloyed modulated precursor flow epitaxial growth (DA-MPEG) using metalorganic and hydride precursors for the growth of AlxGa1−xN layers with high-Al content at relatively low temperatures. The growth of high-quality, high-Al content AlxGa1−xN layers (xAl>50%) that are composed of AlN and AlyGa1−yN monolayers on AlN/sapphire template/substrates by DA-MPEG was demonstrated. The overall composition of the ternary AlxGa1−xN material by DA-MPEG can be controlled continuously by adjusting the Column III mole fraction of the atomic AlyGa1−yN sub-layer. X-ray diffraction and optical transmittance results show that the AlGaN materials have good crystalline quality. The surface morphology of DA-MPEG AlGaN samples measured by atomic force microscopy are comparable to high-temperature-grown AlGaN and are free from surface features such as nano-pits. 相似文献
19.
The vapour growth of InAs1-xPx layers has been carried out by the hydride process. The phosphorus rich part of the system (0.7 ? x ? 1) was especially investigated. Heteroepitaxial deposits of InAs1-xPx and InP have been performed on substrates such as InAs, GaAs and GaP. A systematic study of the influence of the substrate orientation on the quality of the layer has been carried out by growth on hemispherical substrates. Preferential planes have been pointed out: (100) and (111) A for InAs, (111) for GaAs and GaP. The band gap variation as a function of the composition has been determined by photoluminescence at 4.2 °K and X-ray diffraction measurements. It fits the equation: EG(x) eV = 0.425 + 0.722 x + 0.273 x2 at 4.2 °K. 相似文献
20.
Hideki Matsuda Wataru Ishikawa Yoshitaka Ochiai Masatoshi Hayakawa Kazuhiko Hayashi Koichi Aso 《Journal of Non》1984,68(1):53-62
The crystallization behaviours of Co100?1(x+y)NbxBy amorphous alloys were investigated by means of differential thermal analysis and a conventional X-ray diffractometer. The crystallization sequences are discussed in terms of the equilibrium phase diagram of the ternary alloy system.Assuming crystallization occurs as a result of nucleation and growth, the stabilizing effect of eutectic phase separation on the crystallization is shown by introducing the effective free energy of the critical nucleus. 相似文献