热压工艺对Ti(C,N)基纳米复合金属陶瓷模具材料力学性能与微观结构的影响

采用真空热压烧结工艺制备了Ti(C,N)基纳米复合金属陶瓷模具材料,并研究了该模具材料的力学性能与微观结构.结果表明,当烧结温度为1450℃,保温时间为10 min时,模具材料的硬度、断裂韧性和抗弯强度分别为14.57 GPa、8.6 MPa·m1/2和1144 MPa;当烧结温度为1450℃,保温时间为30 min时,模具材料的硬度、断裂韧性和抗弯强度分别为16.29 GPa、7.53 MPa·m1/2和1035 MPa.在这两种烧结工艺下制备的模具材料均具有良好的综合力学性能,烧结工艺得到优化,可以满足不同硬度材料的成型需求.在对模具材料的微观结构分析时发现,模具材料的断裂方式是以沿晶断裂为主的穿晶与沿晶断裂的混合断裂模式.     

添加纳米Ti(C7N3)的ZrO2基纳米陶瓷模具材料

本文针对模具对陶瓷材料的要求,从提高陶瓷模具材料的综合力学性能出发,采用纳米复合方法制备出具有较高综合力学性能的纳米陶瓷模具材料.研究了纳米Ti(C7N3)和Y2O3的组分含量对纳米陶瓷模具材料微观结构和力学性能的影响,结果表明添加纳米Ti(C7N3)和Y2O3的氧化锆纳米陶瓷模具材料的力学性能优于纯氧化锆陶瓷材料,纳米颗粒的添加改善了材料的微观结构和力学性能.当纳米Ti(C7N3)和Y2O3的添加量分别为17.15vol;和5 mol;时,材料的综合性能最好,其抗弯强度为814MPa、断裂韧性6.35 MPa· m1/2、维氏硬度11.87 GPa.     

添加TiC和Cr3C2对超细WC-8Co硬质合金微观结构和性能的影响

在WC-8Co硬质合金中添加不同含量的TiC和Cr3C2,用X射线衍射、扫描电镜分析了添加微量的TiC与Cr3C2对WC-8Co硬质合金微观结构的影响,通过硬度和断裂韧性测试,研究了TiC与Cr3C2含量对材料力学性能的影响.实验结果表明:添加适量TiC和Cr3C2能使超细硬质合金中WC晶粒尺寸细小且晶粒分布更为均匀,微观结构得以优化,从而改善硬质合金力学性能.此外,添加微量TiC能起到细化WC晶粒的作用,提高合金硬度,而添加Cr3C2能够显著抑制硬质合金中硬脆C06 W6C相的形成,从而改善合金的断裂韧性.     

Al2O3／（W，Ti）C纳米复合陶瓷材料的显微结构

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.     

热物性参数对Al2O3/(W,Ti)C/CaF2梯度自润滑陶瓷刀具材料残余应力的影响

基于功能梯度材料的设计思想,设计并制造了Al2O3/(W,Ti) C/CaF2梯度自润滑陶瓷刀具材料.利用有限元法计算分析了梯度自润滑陶瓷刀具材料层间热膨胀系数差值、分布指数和弹性模量对其残余应力的影响,并给出了径向应力和Von Mises等效应力的分布图,为梯度自润滑陶瓷刀具的研制开发提供了理论基础.以此为基础,采用真空热压工艺制备了Al2O3/(W,Ti) C/CaF2梯度自润滑陶瓷刀具材料.结果表明:据此制备的梯度自润滑陶瓷刀具材料具有良好的力学性能.     

以Ni/Al为助剂的TiB2-B4C陶瓷刀具制备及其切削钛合金性能研究

以Ni/Al为助剂在1800℃热压烧结制备了Ni/Al含量分别为0vol;(TB)、5vol;(TBNA5)和10vol;(TBNA10)的TiB2-B4C刀具材料,研究了其致密化机理、显微结构、力学性能和切削削钛合金(Ti6Al4V)的性能.结果表明,5vol;Ni/Al助剂的引入将TiB2-B4 C的相对密度从80;提高到96;,所制备的TBNA5刀具的抗弯强度、断裂韧性和维氏硬度分别为711 MPa、4.6 MPa·m1/2和22.7 GPa,Ni/Al助剂的引入显著改善了TiB2-B4 C陶瓷的致密化和抗弯强度,但是进一步增加Ni/Al助剂的含量(10vol;),将降低其抗弯强度和硬度.切削性能研究表明,与硬质合金刀具相比,TiB2-B4 C陶瓷刀具切削Ti6Al4V的初期磨损较快,但由于更好的高温性能,其后期磨损更慢,且磨损速率更加稳定,其主要磨损机理为粘结磨损和微崩刃,其中含5vol;Ni/Al助剂的TiB2-B4 C陶瓷刀具有相对较好的切削性能.     

MF/纳米ZrO_2增韧氧化铝陶瓷复合材料的力学性能

选用莫来石纤维(MF)和纳米ZrO2为增强体制备了MZTA复合增韧氧化铝陶瓷复合材料。通过设计正交试验讨论了MF含量、nano-ZrO2含量、烧结温度、保温时间等因素对材料力学性能的影响,利用扫描电镜、能谱分析仪研究了陶瓷复合材料的微观结构与性能的关系。结果表明:当莫来石纤维和纳米ZrO2的质量分数分别为10%,烧结温度为1550℃,保温时间为30 min,陶瓷复合材料的抗弯强度、断裂韧性分别达到712 MPa、10.05 MPa.m1/2,与纯Al2O3陶瓷相比晶粒细化、力学性能显著提高;纤维的拔出、桥联、裂纹扩展路径偏转、沿晶断裂等消耗了大量的断裂能、缓和了裂纹尖端的应力是材料断裂韧性提高的主要原因。     

烧结温度对96Al2O3陶瓷力学性能及热导率的影响

采用CaO-MgO-SiO2为烧结助剂,采用无压烧结技术,研究了烧结温度对96Al2O3陶瓷热导率及力学性能的影响.采用阿基米德排水法、三点弯曲法、激光脉冲法、扫描电子显微镜(SEM)及X射线衍射(XRD)等分析手段和设备,对烧结后陶瓷样品的密度、力学性能、热导率和微观组织结构进行了分析研究.研究结果表明:1600℃烧结的Al2O3样品的具有较好的导热性和力学性能,其热导率、密度、维氏硬度和抗弯强度分别为24.9W/(m·K),3.82g/cm3,(13.8±0.2)GPa,(362.9±26.9)MPa.     

反应热压烧结制备SiC/ZrB2复相陶瓷及其性能表征

以二硼化锆、硅和活性碳为原材料,在1850℃、20 MPa条件下,采用反应热压烧结工艺制备出了SiC/ZrB2陶瓷基复合材料.研究了添加剂(硅和活性碳)含量对ZrB2陶瓷烧结行为和力学性能的影响.借助X射线衍射和扫描电镜分析了复合材料的物相组成和微观结构.研究结果表明:添加剂可以显著提高复合材料的烧结致密度和力学性能.复合材料的XRD衍射图谱中只有ZrB2和SiC的衍射峰.当添加剂含量为12wt;时,复合材料的弯曲强度和断裂韧性分别达到584MPa和7.25MPa ·m1/2.显微结构分析表明,致密度的提高、晶粒粒径的减小以及断裂模式的转变是复合材料力学性能提高的主要原因.     

Gd2Ti2O7/ZrO2（3Y）陶瓷制备及力学性能研究

用共沉淀法合成Gd2Ti2O7纳米粉体,经真空烧结制备不同ZrO2(3Y)含量的Gd2Ti2O7/ZrO2(3Y)陶瓷。用XRD、SEM和力学性能试验等测试手段研究样品的物相、形貌和力学性能。结果表明:Gd2Ti2O7/ZrO2(3Y)陶瓷的力学性能随ZrO2(3Y)含量增加显著提高,ZrO2(3Y)含量为90vol%时,样品的维氏硬度、抗弯强度和断裂韧性最大值分别达到20.95GPa、199.21MPa和8.17MPa·m1/2。其原因是ZrO2(3Y)固溶导致晶粒尺寸减小,过饱和析出ZrO2(3Y)的颗粒弥散增韧,以及ZrO2(3Y)应力诱导相变增韧作用。     

Elastic properties of GexAsySe100−x−y glasses

The elastic properties of Ge_xAs_ySe_100−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.     

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 Al_xIn_1−xAs and As_xSb_1−xAl thin films grown on the InP (1 0 0) substrate, and the Al_xIn_1−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.     

Vapour epitaxial growth and characterization of InAs1-xPx

The vapour growth of InAs_1-xP_x 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 InAs_1-xP_x 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: E_G(x) eV = 0.425 + 0.722 x + 0.273 x² at 4.2 °K.     

Synthesis and structure of new phases of the Am?1Bi2BmO3m+3 (m = 2) type

Three polycrystalline bismuth-containing layered perovskite-like oxides are synthesized by high-temperature solid-state reactions. One of these compounds was described previously, namely, Bi₃Ti_1.5W_0.5O₉, 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, Na_0.75Bi_2.25Nb_1.5W_0.5O₉ with the unit cell parameters a = 5.463(1) Å, b = 5.490(7) Å, and c = 24.78(0) Å and Ca_0.5Bi_2.5Ti_0.5Nb_1.5O₉ 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.     

Statistical method of image analysis of heterogeneities in Ba1 ? xRxF2 + x crystals

A statistical method for image analysis of smooth heterogeneities (with comparatively large luminance grade) is suggested. The method allows one to determine the average dimensions of image heterogeneities and characterize the anisotropy of their dimensions and heterogeneity of image luminance by constructing the corresponding pointer curves. The algorithms suggested for the image analysis are tested on two types of heterogeneities in Ba_{1 − x} R _x F_{2 + x} crystals grown from melts by the Stockbarger method—the cellular substructure and heterogeneity on a nanometer scale. These heterogeneities are characteristic of the whole family of nonstoichiometric fluorite M _{1 − x} R _xF_{2 + x} phases. The analysis of the typical images proves the high efficiency of the method of extraction of quantitative information on heterogeneities in M _{1 − x} R _xF_{2 + x} crystals on various scales. __________ Translated from Kristallografiya, Vol. 48, No. 2, 2003, pp. 376–384. Original Russian Text Copyright ? 2003 by Marychev, Chuprunov, Herrero, Sobolev.     

Vapor growth of GaxAl1−xSb

The vapor growth of Ga_xAl_1?xSb was experimentally studied using a closed tube transport technique. In the closed tube process with iodine as a transport agent, Ga_xAl_1?xSb was successfully grown on (111) oriented GaSb substrates at a relatively low temperature. The composition of the grown layer depended primarily on that of the source, and had only a small graded region (<0.5 μm) between the substrate and the epitaxial layer. The growth rate was almost constant irrespective of the growth time, whenever the other growth parameters were unchanged.     

Ab initio calculation of vibrational frequencies of GexPxS1−2x glass

The vibrational frequencies of GeS₄, GeP₄, Ge₂S₆, GeP₃, Ge₃P, Ge₂P₂, P₂S₂, P₃S, P₄S₃, α-P₄S₄, β-P₄S₄, α-P₄S₅, β-P₄S₅, P₄S₇, P₄S₉ and P₄S₁₀ are theoretically computed from the first principles. The Raman frequencies of Ge_xP_xS_1−2x glass are obtained for x varying from 0.05 to 0.019. The computed fundamental frequencies of clusters are compared with those experimentally found. In this way, we are able to identify the vibrating clusters in the real glass. The clusters identified in the real glass are found to be Ge₂P₂, P₄S₃, α-P₄S₄, β-P₄S₄, β-P₄S₅, P₄S₇, P₄S₉, β-P₄S₅, Ge₂S₆, Ge₃P.     

Characterization of the optical properties of LPE InxGa1−xAsyP1−y thin layers grown on InP

A series of In_xGa_1?xAs_yP_1?y single-crystal thin layers have been grown on an InP substrate in a vertical liquid phase epitaxy furnace with a rotating slide boat system. The optical properties of these LPE quaternary alloys lattice-matched to InP have been investigated mainly by photoluminescence and electroreflectance measurements. Photoluminescence spectra of In_xGa_1?xAs_y P_1?y epitaxial layers are dominated by a strong luminescence line due to band-edge emission. At low temperatures, around 4.2 K, we have observed complicated luminescence bands with many fine structures. Electroreflectance spectra for the LPE In_xGa_1?xAs_yP_1?y layers are sufficiently broad to fulfil the low-field condition, and the analysis enabled us to determine precisely the band gap energy.