MgO-Al2O3-SiO2-P2O5微晶玻璃的晶化过程

采用差热分析(DTA)、X射线衍射分析(X-ray)、扫描电镜(SEM)等测试技术,研究了不同添加量的P2O5在MgO-Al2O3-SiO2系堇青石微晶玻璃晶化过程中的作用.结果表明在一定添加量内,引入P2O5起到的非均匀形核作用促进a-堇青石的析出,而当添加量继续增加时,由于磷镁石的形成消耗掉玻璃组成的MgO,反而起到了阻碍效应.     

Na2O含量对BaO-SrO-Nb2O5-B2O3-SiO2系玻璃陶瓷微结构和性能的影响

采用熔融法制备NaO-BaO-SrO-Nb2Os-B2O3-SiO2玻璃陶瓷.借助DSC、XRD、SEM和电学性能测试研究不同含量的Na2O对其相组成、显微结构、介电性能、体积电阻率及击穿强度的影响.结果表明随着Na2O含量(摩尔分数)的增加,玻璃转变温度(Tg)和第一析晶放热峰(Tg1)温度逐渐降低,而第二析晶放热峰温度(Tg2)呈先降低后升高再降低的变化.经(800℃,3h)+(900℃,3h)热处理后,未添加Na2O的样品析出单相四方钨青铜结构的Ba0.5Sr0.5Nb2O6,而添加5%Na2O(摩尔分数)的样品变为单相Ba0.25Sr0.75Nb2O6.当Na2O为10%时,样品的主晶相仍为Ba0.25Sr0.75Nb2O6,但析出NaSr1.2Ba0.8Nb5O15和Na2Ba2Si2O7相;继续增加Na2O量到15%时,样品的晶相种类不变而衍射峰强度有所增强.样品的介电常数随Na2O含量的增加呈“N”字形变化,样品的体积电阻率和击穿强度随Na2O含量的增加而降低,未添加Na2O试样的击穿强度最大为1500kWcm,其储能密度达3J/cm3.     

Dissolution behaviors of Ta2O5, Nb2O5 and their mixture in KOH and H2O system

The dissolution behaviors of Ta2O5,Nb2O5 and their mixture in KOH and H2O system were investigated.A L9(34) orthogonal design was used to study the effects of reaction temperature,mass ratio of KOH to Ta2O5,and reaction time on the dissolution rate of tantalum.It was found that the effect of reaction temperature on the dissolution rate of tantalum was much greater than that of the other factors.The results of factorial experiments showed that Ta2O5 was mainly transformed into insoluble potassium tantalate at low temperature(350 ℃) and transformed into soluble potassium tantalate at high temperature(450 ℃).The insoluble potassium tantalate was analyzed by XRD,which was proved to be KTaO3.Differently,almost all Nb2O5 was transformed into soluble potassium niobate at 350-450℃.As for the mixture of Ta2O5 and Nb2O5,the dissolution rate of tantalum increased and the dissolution rate of niobium decreased as an interaction existed between niobium and tantalum.And increasing the mole ratio of Nb2O5 to Ta2O5 in the mixture was beneficial to the dissolution of both Ta2O5 and Nb2O5.In addition,the mechanism of the interaction between niobium and tantalum was also investigated through phase and chemical analysis.     

Three-Dimensional rendering and phase analysis of the CaO-Al2O3-SiO2 system

A program for rendering ternary phase equilibria in 3-point perspective was developed using Microsoft Visual Basic. Algorithms for rendering and phase analysis are described. With the software, liquidus, subliquidus, and solidus surfaces can be generated, and the three-dimensional object can be rotated to any angle for viewing. The operator can select a composition on the top-view 2-dimensional projection, and surfaces pertinent to an isoplethal study will be displayed. A phase analysis plot is simultaneously displayed wherein relative proportions and compositions of phases are enumerated for any chosen temperature. Phase analysis calculations were based on methods of analytical geometry using best-fit polynomials for liquidus surfaces and their contact boundaries. Phase analysis involved separation into one of five possible modes of phase evolution during cooling.     

球形Ta2O5/Nb2O5制备方法的研究

研究了用氨沉淀氟钽（或铌）酸溶液制备球形Ta2O5／Na2O5工艺。通过实验探讨了沉淀条件、溶液浓度、沉淀时间、焙烧温度等工艺参数的最佳组合。结果表明，用氨沉淀氟钽（或铌）酸溶液制备球形的Ta2O5／Nb2O5，必须首先得到不规则的Ta（OH）5/Nb（OH）5。要得到不规则Ta（OH）5/Nb（OH）5，反应时搅拌强度要大，搅拌速率应控制在800～1200r／min，反应结束后继续搅拌10～20min，终点pH值控制为8．5；氟钽（或铌）酸溶液浓度为60～80g，L沉淀10min，浓度为120～140g，L沉淀15min，之后可得到不规则Ta（OH）5/Nb（OH）5。再在800～850℃，焙烧6h可得到球形Ta2O5／Nb2O5。     

ZnO-Al2O3-B2O3-SiO2系微晶玻璃的研究

研究了能与可伐合金匹配封接的ZnO-Al2O3-B2O3-SiO2系微晶玻璃,其膨胀系数为5.2×10-6/℃,采用该微晶玻璃的封接器件绝缘电阻可达1×1013Q·cm.通过对该微晶玻璃的差热曲线分析,确定了其热处理制度;用X射线衍射仪和扫描电镜研究了该系统的主晶相,其主晶相为ZnAl2 O4、ZnB2O4和少量的NaSiAl2O4晶体.通过控制碱金属离子进入晶格,可明显提高微晶玻璃的绝缘电阻.     

Phase equilibria in the system La2O3-BaO-P2O5: The partial system LaPO4-Ba2P2O7-Ba(PO3)2

The LaPO₄-Ba₂P₂O₇-Ba(PO₃)₂ portion of the oxide La₂O₃-BaO-P₂O₅ system has been investigated. Important parts of this investigation were the determination of equilibria in the LaPO₄-Ba(PO₃)₂ subsystem and the addition of liquidus data to the partially known LaPO₄-Ba(PO₃)₂-Ba₂P₂O₇ subsystem. These data were combined with known data from the LaPO₄-Ba₂P₂O₇ subsystem and with measurements of the equilibria within the LaPO₄-Ba₃P₄O₁₃ isopleth to determine the nature of the phase equilibria in the quasi-ternary LaPO₄-Ba₂P₂O₇-Ba(PO₃)₂ system.     

Crystallization and properties of some CaO-Al2O3-SiO2 system glass-ceramics with Y2O3 addition

The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 （CAS） system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered and the crystallization was accelerated with Y2O3 addition, and only wollastonite as a main crystalline phase was precipitated. The volume fraction of crystalline phase and density were increased with Y2O3 addition. The results suggest that the CAS glass-ceramics would get the lowest sintering temperature and optimal microstructure with the addition of Y2O3 by 3.25 %. The bending strength has a maximum due to the oriented and interlocked wollastonite crystal, which causes crack divert or blunts to limit the further development of the flaw size and increases the surface energy of fracture.     

Reinvestigation of the Phase Equilibria in the La2O3-P2O5 System

The phase equilibria between the solid phases in the La₂O₃-P₂O₅ system were reinvestigated with solid state reaction method. The existence of La₃PO₇, La₇P₃O₁₈, LaPO₄, and LaP₃O₉ was confirmed. La₇P₃O₁₈ can form only at ~1200 °C or higher possibly due to kinetic reasons, but it is stable at lower temperatures. On the other hand, three intermediate compounds proposed to exist, La₅PO₁₀, La₄(P₂O₇)₃, and La₂P₄O₁₃ were not obtained in this study. Based on the literature, La₄(P₂O₇)₃ and La₂P₄O₁₃ are considered to be metastable phases, although thermodynamic evidence is still required.     

Phase relations in the system Sr-Cr-O and thermodynamic properties of SrCrO4 and Sr3Cr2O8

The phase relations involving various oxides in the system Sr-Cr-O at 1250 K have been determined by equilibrating samples representing 17 compositions inside the ternary and subsequent phase identification in quenched samples. Optical and scanning electron microscopes were used in conjunction with X-ray diffraction (XRD) to identify phases; the composition of each phase was verified using energy dispersive analysis of X-rays (EDX). Four stable ternary oxides, SrCrO₄, Sr₃Cr₂O₈, Sr₂CrO₄, and SrCr₂O₄, were identified. All the compounds except Sr₃Cr₂O₈ were found stoichiometric within the accuracy of EDX. X-ray absorption near-edge structure (XANES) analysis showed that the average valence of Cr in Sr₃Cr₂O₈ is +5.2, suggesting the presence of mixed valence states in this compound. Only one of the ternary oxides, SrCr₂O₄, was found to coexist with Cr metal. The compounds SrCrO₄ and Sr₃Cr₂O₈ were stable in pure oxygen. The standard Gibbs energy of formation of SrCrO₄ was determined as a function of temperature in the range from 950 to 1280 K using a solidstate cell incorporating single-crystal SrF₂ as the electrolyte. The oxygen potential corresponding to the three-phase equilibria involving SrCrO₄, Sr₃Cr₂O₈, and Cr₂O₃ was measured from 1080 to 1380 K using a cell with yttria-stabilized zirconia as the solid electrolyte and pure oxygen gas at a pressure of 0.1 MPa as the reference electrode. The standard Gibbs energy of formation of Sr₃Cr₂O₈ was derived from the oxygen potential. The results can be represented by the following equations:

Fe_2O_3含量对CaO-Al_2O_3-SiO_2系微晶玻璃显微组织与力学性能的影响(英文)

采用差热分析(DTA)、X射线衍射(XRD)、扫描电镜(SEM)、电子顺磁共振(ESR)和Mssbauer谱等技术研究Fe2O3含量对CaO-Al2O3-SiO2系微晶玻璃显微组织与力学性能的影响。结果表明:Fe2O3的加入不改变CaO-Al2O3-SiO2系微晶玻璃析出的主晶相类型,但使体系的析晶峰温度降低,析晶活化能增加和析出晶体的粒度减小。ESR测试结果表明,Fe2O3的加入会因轴向扭曲造成分相,从而促进析晶;同时,Fe2O3的加入能更好地调整CaO-Al2O3-SiO2系微晶玻璃网络内部结构,使Fe3+进入比四面体对称性更高的八面体配位,有利于抗弯强度的增大。Mssbauer测试结果表明,Fe3+和Fe2+在CaO-Al2O3-SiO2系微晶玻璃存在不同的配位,且微晶玻璃的抗弯强度随Fe3+六配位数的增多而增大;同时,Fe2+和Fe3+相互作用的增强也有利于微晶玻璃抗弯强度的增大。在核化温度为700°C、核化时间为2 h、晶化温度为910°C和晶化时间为3 h的热处理条件下,样品的显微硬度达到HV 896.9,抗弯强度达到217 MPa。     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Phase relationships in the systems RE2O3-Al2O3-SiO2 (RE = rare earth element, Y, and Sc)

A literature survey and recent results on phase relationships in the quasi-ternary systems RE₂O₃-Al₂O₃-SiO₂ are given. The investigated systems exhibit extended ternary solid solutions, RE_9.33+2x(Si_{1_x}Al_xO₄)₆O₂ (withx up to ~0.33) and/or RE₄Al_{2(1_X)}Si_2xO_9+x (withx up to ~0.3), which are based on the quasi-binary phases RE_9.33(SiO₄)₆O₂ and RE₄A1₂O₉, respectively. The former is encountered only in systems with laige RE³⁺ ions (e.g., La³⁺), whereas the latter is found in systems with small RE³⁺ ions (e.g., Yb³⁺); in systems with medium-sized KE³⁺ ions (e.g., Gd³⁺) both types exist Quasi-ternary compounds are known only in the La, Ce, and Sc systems. Severe discrepancies in reported ternary eutectic temperatures led to a need for their accurate redeteimination.     

去除Ta2O5/Nb2O5中杂质S的工艺研究

从理论和实际应用方面,研究了去除Ta2O5/Nb2O5中杂质S的方法.通过对制取高纯Ta2O5和Nb2O5的中间产品高纯Ta（OH）5/Nb（OH）3进行过氧化处理,改变Ta,Nb,S等元素在物料中的存在方式,增大了含S杂质的溶解性,降低了物料对含S离子的吸附能力及硫酸盐的分解温度,通过洗涤、焙烧达到有效去除产品中杂质元素S的目的.该方法可在不影响Ta2O5/Nb2O5产品质量的情况下,使杂质S降低到0.0001%以下.     

MgO-Al2O3-SiO2微晶玻璃介电特性

以2MgO-2Al2O3-5SiO2微晶玻璃为基础成分,引入TiO2和ZnO,探讨了TiO2,ZnO及不同的热处理条件对微晶玻璃相组成、介电性能的影响.结果表明Ti4+以单体TiO2形式存在,并未取代Si4+位置,形成固溶体,随TiO2含量的增加,致密化温度升高,谐振频率温度系数τf从负变正,介电常数εr增大,Qf值减小;ZnO在堇青石微晶玻璃中,Zn2+取代Mg2+位置,形成Mg1 91Zn0 09(Al4Si5 04O18)固溶体,降低体系的自由能,促进烧结;随烧结温度升高及保温时间的延长,相组成由MgAl2Si3O10,MgAl2Si4O12转化Mg1 91Zn0.09(Al4Si5 04O18)固溶体,εr减小,Qf增大.TiO2添加量为5ω/%的MgO-Al2O3-SiO2-ZnO-H3BO3玻璃,在900℃烧结2 h,可获得较佳的介电性能εr=5.53,Qf=14 000 GHz,τf=-7×10-6/℃,是一种理想的多层片式微波器件及模块用材料.     

Phase relations in the Nb-Pd-Hf-Al system

In support of computational design of coherent aluminide strengthened Nb alloys, the phase equilibria in a series of six Nb-Pd-Hf-Al alloys were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD). All alloys were heat treated at 1200°C for 200 h, while three alloys were also heat treated at 1500°C for 200 h. Three-phase equilibria and two-phase equilibria were observed in two alloys at both temperatures. Two more alloys also exhibited three-phase equilibria at 1200 °C, while one alloy exhibited two-phase equilibria at 1200 °C. A final alloy revealed four-phase equilibria at both temperatures, confirming the presence of a unique tie-tetrahedron in the Nb-Pd-Hf-Al system. Based on the characterization of phases by SEM and XRD, the Nb-Pd-Hf-Al partial phase diagram at 1200 °C has been constructed. Such phase diagrams provide the basis for designing precipitation-strengthened Nb-based superalloys.     

CVD Al2O3-SiO2系氧化物及其机理分析

研究了AlCl3-SiCl4-H2-CO2气相系统不同温度化学气相沉积Al2O3-SiO2系氧化物相组成及显微结构，分析了化学气相沉积过程机理。结果表明，CVD过程不能实现Al-Si化合物的均匀混合，不同温度沉积产物为不同变体Al2O3结合非晶SiO2或其固溶体复合氧化物，1050℃以下，随沉积温度提高，沉积物颗粒尺寸减小，1050℃可沉积出晶化较为完全的莫来石结合α—Al2O3，t—Al2O3和非晶SiO2致密涂层。     

添加P2O5及F对CaO-MgO-Al2O3-SiO2系微晶玻璃形成及析晶的影响

为了研究P2O5及氟化物对CaO-MgO-Al2O3-SiO2系微晶玻璃形成及析晶的影响，采用高温熔融法制备了不同P2O5及氟化物含量的玻璃试样。结果表明：玻璃的形成范围大致为（P205％＋F％）≤10％。在氟化物的添加量较低时，试样仅发生表面析晶，析出晶体为硅灰石（CaSi03）和少量的钙长石（CaAl2Si2O8）。随着氟化物含量是增加，试样在表面和内部都析出晶体，最终形成“整体”析晶的状态。P2O5的加入抑制了表面析晶，但促进了玻璃的分相和整体析晶。同时添加P2O5及氟化物将促进晶体的整体析出和晶体的生长，P2O5加入量的提高有利于氟磷灰石（Ca5（PO4）3F）的析出，而氟化物含量的提高增加了钙长石的析出。     

Pb2Nb2O7-NaNbO3-SiO2纳米复合材料的制备及其介电性能

通过辊压成型及随后的可控结晶过程,制备Pb2Nb2O7-NaNbO3-SiO2系纳米复合材料。X射线衍射分析结果表明：温度为750-000℃时,Pb2Nb2O7,NaNbO3和PbNb2O6晶相可在玻璃基体中析出：Pb2Nb2O7相在750℃结晶析出,850℃消失;NaNbO3为850℃时的主晶相：而PbNb2O6相的晶化温度为850℃;由可控结晶技术制备的玻璃陶瓷介电性能受热处理过程中所形成的相组成影响很大;试样在850℃退火3h,具有最高的介电常数（〉600）。微观结构分析结果表明,残余玻璃相填充在纳米晶粒的晶界处。电镜分析进一步发现,850℃退火3h的试样中不均匀地分布着纳米NaNbO3和PbNb2O6颗粒,这是材料具有高介电常数的主要原因。     

乙醇钽化学气相沉积制备Ta2O5薄膜研究进展

Ta2O5薄膜层具有较高的介电常数、折射率以及和ULSI加工过程中的相容性，因而将在硅芯片栅层材料、动态随机存储器、减反膜、气敏传感器、太阳能光伏电池面板介电层等方面得到应用。对以Ta（OC2H5）5为原料，通过常规金属有机化合物气相沉积、光致化学气相沉积、等离子增强化学气相沉积、原子层化学气相沉积和脉冲化学气相沉积法制备Ta2O5薄膜进行了评述，并对这些方法存在的问题进行了分析。