Pb(Zr0.95Ti0.05)O3粉体的冲击波合成及烧结研究

以ZrO2、Pb304和TiO2为原料（Nb2O5为掺杂剂），采用柱面冲击波装置合成了Pb（Zr0.95 Ti0.05）O2（PZT95／5）粉体，并对粉体活性及其烧结性能进行了研究。XRD及SEM分析表明，利用冲击波的高温高压作用可以合成单一钙钛矿相PZT95／5粉体，并使得粉体发生了晶粒细化与晶格畸变，这有利于增强粉体活性，促进低温活化烧结。该粉体在1100℃的低温下即可烧结成瓷；在1200℃烧结3h，陶瓷体致密度达到最大，约7．79g／cm^3，且晶粒尺寸相近，分布均匀。     

高活性锆钛酸铅压电陶瓷粉体的合成及其烧结性能研究

以Pb3O4、ZrO2和TiO2为原料,采用冲击波加载技术合成锆钛酸铅Pb(Zr0.95Ti0.05)O3粉体,并对粉体活性和烧结特性进行XRD和SEM表征,研究结果表明,利用冲击波的高温高压作用可以合成单一钙钛矿相锆钛酸铅粉体,合成粉体产生了细化并存在一定程度的晶格畸变,有利于增强粉体活性,促进了低温活化烧结,也显著地改善了陶瓷的烧结性能,在常压下1200℃烧结150min得到了密度达到7.83g/cm3的锆钛酸铅95/5陶瓷体,比传统固相法制备的粉体烧结温度降低了100℃左右,且得到的陶瓷体晶粒形状、大小均匀。     

微波烧结Al2O3/SiC纳米复合陶瓷的研究

以分析纯Al(NO3)3.9H2O·NH3.H2O和50 nm的SiC粉体为原料,采用溶胶-凝胶法制备干凝胶,经热处理合成Al2O3/SiC纳米复合粉体。利用微波烧结制备Al2O3/SiC纳米复合陶瓷,并与常规烧结比较,分析了两种烧结方法对制备试样的力学性能影响。结果表明,与常规烧结相比,微波烧结可以提高Al2O3/SiC纳米复合陶瓷的强度和韧性,改善材料的显微结构,促进致密化和晶粒生长。     

改进的两步法制备PZN-PT-BT铁电陶瓷

基于SwartzandShrout的二次合成法,采用改进的两步法,部分原料预合成,一次烧结合成具有完全钙钛矿结构的75Pb(Zn1/3Nb2/3)O310PbTiO315BaTiO3固溶体陶瓷。首先按75∶10∶15一次性称量PbO(并且PbO过量5mol%),然后与ZnNb2O6在660℃预反应1h。粉碎后再加入TiO2和BaCO3,充分混合后,在1060～1140℃保温2h烧结成陶瓷试样。XRD结果表明660℃预合成的中间相中没有钙钛矿相,不同于传统的预合成和烧结,改进的两步法工艺在烧结阶段陶瓷的成瓷和致密化同时进行,完成了中间相向钙钛矿相的完全转变。与二次合成法相比,本方法简化了工艺,降低了预合成温度,拓宽了烧结温度,所获得的陶瓷试样介电性能优良。对陶瓷试样进行相同条件的退火,在1100℃烧结的陶瓷试样,介电常数ε获得95%的增幅;在1140℃烧结的陶瓷试样介电常数ε则获得16%的降幅。     

水热合成锆钛酸铅微晶体的晶粒度分析

采用Ti02，ZrOCl2·8H2O，Pb（NO3）2为原料，KOH为矿化剂，在不同温度、不同KOH浓度、不同反应时间，进行了锆钛酸铅（PZT）微晶体的水热合成实验。结果表明，水热反应温度与KOH浓度大大影响了PZT微晶体的晶粒度和晶体结构，而水热反应时间只影响了PZT微晶体的晶粒度，对晶体结构没有明显影响。在实验条件下水热合成的PZT微晶的晶粒度为10～20nm之间。     

低温烧结Al2O3-硅酸盐玻璃系玻璃陶瓷的制备和性能研究

采用Al2O3-硅酸盐玻璃复合体系制备低温烧结玻璃陶瓷，通过TG-DTA、XRD、SEM等分析方法对样品进行表征，随着玻璃含量的增加玻璃陶瓷的烧结温度逐渐降低，在玻璃含量约为50％（质量分数）时玻璃陶瓷的热导率达到最大值2．70W/m·K，此时的玻璃陶瓷具有低的烧结温度（800℃）、高的相对密度（≥95％）、低的电容率（8～10）、低的介电损耗（1．5％～0．7％），有望成为LED封装用基板材料。     

TiAl纳米合金的机械活化-放电等离子原位烧结

（Ti-50％（原子分数）AD-10％Al2O3粉体经过球磨的机械活化（MA）后，用放电等离子烧结（SPS）工艺，在烧结的同时进行固化。采用机械活化-放电等离子烧结（MA—SPS）的方法原位烧结制备TiAl—Al2O3块体纳米材料。球磨前后，（Ti-50％（原子分数）AD-10％Al2O3粉体的衍射图（XRD）相似。MA后得到晶粒度〈25nm的纳米粉体，其中Al2O3起到机械活化和细化晶粒的作用，促使粉体快速纳米化。纳米粉体在温度低于800℃、烧结时间〈5min的烧结参数下，烧结成TiAl纳米合金。TiAl纳米合金的微观结构表明，合金有γ-TiAl和α2—Ti3Al双相组织。SPS原位烧结后，得到密度为3．73g／cm^3的（γ＋α2）双相组织，组成相的晶粒度〈130nm。     

空心阴极等离子烧结AlN陶瓷

将空心阴极效应运用于AlN陶瓷的烧结,选用自蔓延高温合成的AlN粉体为原料,用Y2O3-CaO-Li2O作为烧结助剂,制备出了致密度高,导热性能好的AlN陶瓷.在添加5.5wt％的Y2O3-CaO-Li2O(Y2O3:Li2O:CaO=44:6:5wt％)作为烧结助剂,在1700℃,保温3h的烧结条件下,获得相对密度为98.89％,热导率为93.8 W/(m·K)AlN烧结体.烧结体的断口SEM照片显示烧结试样的晶粒生长发育完善,晶粒轮廓清晰呈尖锐的多面体形状,晶粒大小均匀,气孔和晶界相少,断裂模式为穿晶断裂.TEM表明:晶界相少,且大部分都缩至三角晶界,AlN颗粒与颗粒接触紧密.     

PZT含量对PZT-PZN-PNN压电陶瓷材料电性能的影响

采用传统固相法制备了xPb（Zr0.52Ti0.48）O3-（1-x）{Pb（Zn1/3Nb2/3）O3-Pb（Ni1/3Nb2/3）O3}（简称PZT-PZN-PNN）四元系压电陶瓷，研究了不同PZT含量对PZT-PZN-PNN陶瓷的相结构、显微结构、压电性能和介电性能的影响。结果表明：材料的压电常数（d33）、机电耦合系数（％）和介电常数（曲随着PZT含量的增加先增大，后减小，当PZT含量为0.83时，其值达到最大值；随着PZT含量的增加，材料的机械品质因数（Qm）逐渐增大，谐振电阻僻（Rf）和介电损耗（tanδ）逐渐减小。当PZT含量为0.83时，四元系PZT-PZN-PNN压电陶瓷在较低的烧结温度（1000℃）下烧结，其主要的电性能参数如下：d33=477pC/N，Kp=0.71，Qm=98，εf=2228，tanδ=0.0070，Tc=325℃，根据双晶片对压电陶瓷材料的性能要求，该纽份可作为纺织机械中选针器用压电双晶片的侯选材料。     

PZT纳米材料低温合成及性能研究

用Pb(NO3)2、ZrOCl28H2O(或Zr(NO3)4·5H2O)与TiO2在160℃反应4 h生成PZT纳米材料.对制备的PZT纳米材料进行了XRD、TEM、SEM、XRF及热分析研究.生成的PZT晶粒为大小均匀的球形颗粒,平均直径为5～10nm,这些纳米颗粒团聚成规则的方形.通过调节反应条件可改变PZT产物的形貌,得到PZT的片或棒.并对水热反应PZT纳米材料晶体生长的机制进行了探讨.对PZT纳米粉体制备的块体材料进行了烧结和介电性能研究.其烧结温度大大降低,在1150℃即可烧结成瓷,样品收缩率为9.3%.烧结后PZT的晶粒形貌与烧结温度有关.其介电性能随频率的稳定性好.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。