硅酸锆超细粉体加工技术

为促进硅酸锆超细粉体加工技术进步,本文中介绍了硅酸锆在建筑卫生陶瓷行业的应用,以及硅酸锆乳浊机理、硅酸锆超细粉体加工原料概况,并对硅酸锆超细粉体加工所使用的加工设备及加工工艺进行了比较,对提出了硅酸锆超细粉体加工技术的发展方向,认为硅酸锆超细粉体加工技术应朝着超细研磨、复合改性、干法分级方向发展。     

硅酸锆超细粉体标准样品的研制

为了制备硅酸锆标准样品以规范硅酸锆的生产、检验与流通,采用先进的球磨和搅拌磨工艺,针对对硅酸锆品质有重要影响的3个指标,即氧化锆(铪)含量、特征粒径d50、d98,制备建筑陶瓷用硅酸锆A6、日用陶瓷用硅酸锆A8系列标准样品。结果表明,样品经过均匀性检验、稳定性检验、定值及量值评估阶段,最终通过了国家标准样品委员会的评审。     

硅酸锆粉体的合成研究

硅酸锆具有熔点高、热导率低、膨胀系数小及化学稳定性优异等特点,是高温结构陶瓷、耐火材料和锆基色料的重要候选材料。鉴于天然硅酸锆粉体的固有缺陷,开展化学合成硅酸锆粉体意义重大。总结了硅酸锆粉体制备的主要方法,包括高温固相法、水热法、溶胶-凝胶法、沉淀法和微乳液法等,分析了硅酸锆粉体的合成机理,最后展望了合成硅酸锆粉体的发展趋势。     

ZrB2-SiC超高温陶瓷氧化过程中ZrSiO4相形成机制研究

研究了ZrB2-20vol%SiC超高温陶瓷在空气气氛中的氧化行为,分析了氧化温度、氧分压和氧化时间等对硅酸锆形成和晶体生长过程的影响,提出了ZrB2-SiC超高温陶瓷氧化过程中硅酸锆相的形成机制.热力学计算结果表明,硅酸锆相的形成与高温下SiC的活性氧化有关.实验结果表明,常压氧化过程中,硅酸锆的形成可分为两个阶段,(I)形核,这一过程与SiC的活性氧化有关;(II)晶体生长,随着氧化时间的延长,氧化后形成的富硅玻璃相与氧化锆在硅酸锆晶核处反应,晶粒进一步长大.研究表明,在1500℃氧化90min后,硅酸锆的晶粒尺寸达到100μm左右.     

超细硅酸锆湿法分级应用研究

比较了超细硅酸锆湿法分级的几种方法 ,对超细硅酸锆湿法分级设备使用效果进行对照比较。     

研磨介质对超细硅酸锆粉体质量的影响

分析对比用于生产超细硅酸锆的常用研磨介质,通过测定其研磨损耗及产品的化学成分、白度值,研究研磨介质对超细硅酸锆质量的影响。结果表明:不同的研磨介质对产品质量产生不同影响,但在一定的工艺条件下均能用于超细硅酸锆的生产。     

微波水热法合成硅酸锆纳米粉体的研究

以氧氯化锆和硅酸乙酯为原料、NaF为矿化剂,采用微波水热法(Microwave-hydrothermal,M-H)在160～200℃成功地制备出高纯硅酸锆纳米粉体,并利用X射线衍射(XRD)和扫描电镜(SEM)对所合成的硅酸锆粉体进行了研究,结果表明,微波水热使ZrSiO4的结晶温度降低到160℃,合成时间缩短到30min,大大降低了硅酸锆粉体的合成能耗.硅酸锆的微波水热合成温度为180C时,所合成的硅酸锆粉体颗粒呈圆片状,直径约为400nm,厚度约为直径的1/10,外形规则,粒度分布均匀.通过谢乐公式可以计算出微波水热法合成的ZrSiO4晶体的尺寸约为20nm.煅烧有利于进一步提高粉体的结晶度,但是颗粒形状及大小均未产生显著变化.结合测试分析,对纳米硅酸锆粉体的微波水热合成反应机理进行了初步探讨.     

硅烷偶联剂对制备硅酸锆薄膜及其抗氧化性能的影响

采用乙酸锆和正硅酸乙酯为原料, 硅烷偶联剂3-氨丙基三乙氧基硅(APTES)为表面改性剂, 通过溶胶-凝胶法制备了致密硅酸锆薄膜。系统研究了APTES的添加对硅酸锆薄膜的晶体结构、显微形貌及其抗氧化性能的影响。实验结果表明, 添加硅酸锆摩尔浓度10mol%的APTES可以制备出纯相的致密硅酸锆薄膜, 超过这一浓度则会出现少量的SiO₂杂质, 同时造成硅酸锆溶胶的黏度迅速升高。AFM测试结果表明添加APTES制备的薄膜更致密平滑。1300℃抗氧化测试102 h后, 未镀膜的碳化硅基底增重0.16%, 相比之下, 添加APTES前后的样品的增重分别为0.08% 和0.03%, 说明添加APTES有利于提高ZrSiO₄薄膜的致密度, 进而提高其抗氧化性能。     

磨加硅酸锆晶体对搪瓷材料性能的影响

参考国内外有关技术资料,设计并研制出耐温急变性能和耐酸化学稳定性优良的搪瓷材料,采用扫描电子显微镜对搪瓷表面的显微形貌进行研究,结果表明:搪瓷材料中,磨加一定量的硅酸锆晶体,使搪瓷材料形成非晶态材料和硅酸锆晶体的复合材料,可以有效地提高其耐温急变性能;既要提高搪瓷材料的耐温急变性能,又要保持其优良的耐酸化学稳定性,有一个最佳的硅酸锆晶体磨加引入量范围.     

以炭黑为还原剂制备硅酸锆晶须的研究

以无水四氯化锆为锆源, 正硅酸乙酯(TEOS)为硅源, 氟化锂为矿化剂, 乙醇为溶剂, 炭黑为还原剂, 采用非水解溶胶-凝胶法在700 ℃制备得到硅酸锆晶须, 借助TG-DTA、XRD和TEM等测试手段研究了炭黑加入方式及用量对硅酸锆合成与形貌的影响。结果表明: 炭黑以悬浮液形式加入有助于硅酸锆的一维择优生长; 炭黑用量为6wt%时能获得直径为30~90 nm, 长径比为6~15, 沿[001]方向择优生长的硅酸锆晶须。炭黑与氧反应形成二氧化碳和一氧化碳, 炭黑加入方式及用量能够调控反应体系的氧分压。降低氧分压有利于形成更多的气相SiF₄, 这是促进ZrSiO₄一维定向生长的基础, 但氧分压过低又妨碍ZrSiO₄晶体的合成。因此, 适当氧分压有利于ZrSiO₄晶须的 生长。     

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)。