燃烧合成Al2O3/YSZ复合陶瓷显微结构、强化与原位增韧

通过在铝热剂中引入ZrO2与Y2O3混合粉末,借助燃烧合成及远离平衡态下的共晶生长,制备出以t-ZrO2纳微米纤维成排镶嵌于其上、长径比为12.0～15.0且具有不同生长取向的Al2O3棒晶为基体的Al2O3/YSZ共晶复合陶瓷.相比于定向凝固Al2O3/YSZ共晶复合陶瓷,因本试验具有的高共晶生长速率,导致Al2O3棒晶上的ZrO2正方相纳微米纤维平均尺寸及相间距均下降至150nm,使棒晶基体上的残余压应力高于定向凝固Al2O3/YSZ共晶复合陶瓷,从而在棒晶内高密度低能异相界面的支持下,复合陶瓷得以强化;同时,也正因高强度棒晶及高密度、大角度晶界的存在,在裂纹扩展中诱发棒晶裂纹桥接、拔出及α-Al2O3片晶摩擦互锁增韧机制,材料又得以明显韧化,其断裂韧度高出定向凝固共晶复合陶瓷172%～240%.     

熔体自生原位增韧Al2O3/20%ZrO2(3Y)复合陶瓷显微结构、裂纹扩展与增韧

通过在铝热剂中添加一定含量的微米ZrO2(3Y)粉末,以铝热燃烧、陶瓷/金属液相分离与熔体自生方式,制备出以t-ZrO2纳微米纤维镶嵌于其上且具有不同结构取向的蓝宝石棒晶为基的Al2O3/20%ZrO2(3Y)复合陶瓷,并结合力学性能测试,研究材料显微结构、裂纹扩展与增韧之间的内在联系.研究得出,陶瓷抗弯强度与断裂韧性分别达到1 086MPa与11.6 MPa·m05;存在于蓝宝石棒晶上大量、细密的低能异相界面(相界面间距为纳微米尺度)及高的残余压应力,使蓝宝石棒晶得以补强;具有高强度、高模量且长径比为6.0～8.0的蓝宝石棒晶及分布于其上的高残余压应力又迫使裂纹沿棒晶边界扩展,诱发裂纹偏转、棒晶桥接与拔出增韧机制,并相继伴随着t-ZrO2相变、α-Al2O3片晶桥接、Cr颗粒延性相塑变及相变诱发微裂纹多重增韧机制的协同作用,保证材料在保持高强度的同时,又具有高韧性与高的缺陷容忍性.     

纳米/微米Al2O3-ZrO2内衬复相陶瓷的自蔓延高温合成

采用SHS重力分离技术制备出内衬Al2O3-ZrO2复相陶瓷.复相陶瓷基体主要由纤维状(Al2O3+ZrO2)共晶体组成,其中共晶体的ZrO2纤维直径达到纳米/微米尺度.经Vickers压痕法测试其断裂韧度为15.96MPa·m1/2,SEM观察和陶瓷材料断裂韧度测试得出裂纹的扩展主要受共晶体中Al2O3-ZrO2纳米/微米相增韧机制控制,迫使裂纹沿共晶体边界或层片共晶体Al2O3-ZrO2相界偏转,从而维持了该复相陶瓷较高的断裂韧度.     

Al2O3/ZrO2(Y2O3)共晶复合陶瓷晶体生长机理

基于国外定向凝固氧化物/氧化物共晶复合陶瓷的晶体生长动力学行为的研究成果,阐述其动力学机制,分析动力学因素对微观结构形态的影响,探讨晶体生长热力学、动力学行为与微观结构形态之间的关系,同时结合以燃烧合成、快速凝固技术制备的新型高强韧Al2O3/ZrO2(Y2O3)共晶复合陶瓷,探讨共晶复合陶瓷在快速凝固条件下的晶体生长动力学行为.结合定向凝固与快速凝固两种晶体生长机制,得知过冷度、凝固界面前沿的温度梯度是影响晶体生长方式的重要因素,且受二者决定的凝固速率(即晶体生长速率)则决定材料的最终微观结构与形态.     

超高重力场燃烧合成TiC-TiB_2的组织变质与断裂行为

采用超高重力场燃烧合成工艺,并从500 g到2 500 g每间隔500 g依次增大超重力场加速度,制备系列TiC-TiB2凝固陶瓷。经XRD、FESEM和EDS分析,发现陶瓷显微组织均由片晶的TiB2基体相、不规则的TiC第二相及少量的Al2O3夹杂与Cr基金属相组成。增大超重力场加速度,反应熔体内部各组份之间的对流(Stokes)加强,可加快Al2O3液滴的上浮与分离,促进TiC-TiB2-Me液相成分均匀化,使陶瓷显微组织得以细化,且当超重力场加速度超过2 000 g时,出现TiB2片晶厚度小于1μm的超细晶组织,同时随陶瓷基体上Al2O3夹杂量降低、TiB2片晶异常长大弱化,陶瓷组织均匀性提高。经FESEM断口形貌与裂纹扩展观察,发现TiB2基体相的裂纹桥接与拔出,并耦合晶间Cr基延性相增韧构成陶瓷的复合增韧机制,且随超重力场加速度增大,陶瓷的致密性与组织均质性得以提升,不仅促进TiB2基体相裂纹桥接与拔出,而且可增大Cr基延性对陶瓷增韧的贡献,使得陶瓷弯曲强度与断裂韧性分别同时达到最大值(975±16)MPa和(16.8±1.2)MPa·m1/2。     

添加Y2O3的ZrO2增韧Al2O3陶瓷抗钢液腐蚀性能的研究

采用工业ZrO2和AlO3为原料,以Y2O3作为稳定剂,通过适当工艺制备出ZrO2增韧Al2O3(ZTA)陶瓷.主要研究了ZrO2和Y2O3稳定剂对ZTA陶瓷烧结性和抗钢液腐蚀性能的影响.实验结果表明:机械混合法引入的Y2O3在改善ZTA陶瓷的烧结性的同时,可以提高材料的抗钢液腐蚀性能;随ZrO2含量的增加,ZTA陶瓷的抗钢液腐蚀性能增强;材料中大量微裂纹的存在可以提高材料的韧性,但抗钢液腐蚀性能有所下降.     

Y2O3与MgO复合掺杂ZrO2材料的电性能研究

利用交流复阻抗分析技术对Y2O3与 MgO复合掺杂ZrO2材料的电性能进行了研究.发现随着Y2O3掺入量的增加,参与跃迁的氧空位增多,并促进烧结体的密度提高,气孔率降低,使得晶粒边界的电阻减少,导致(ZrO2)1-x-y(YO1.5)x(MgO)y陶瓷电导率增大.烧结温度的提高也是增加 (ZrO2 )1-x-y(YO1.5)x(MgO)y陶瓷电导率的重要因素之一.     

绝热温度对超重力场燃烧合成TiC-TiB2组织及性能的影响

通过在(Ti+B4C)体系中引入相应含量的(CrO3+Al)高能铝热剂,采用超重力场燃烧合成,在不同绝热温度下制备出具有不同含量Cr基合金相的TiC-TiB2复合陶瓷。XRD、FESEM和EDS分析表明,TiC-TiB2复合陶瓷主要由TiB2片晶与不规则的TiC晶粒组成,少量的Al2O3夹杂颗粒孤立地分布于陶瓷基体上,而Cr基合金相则分布于TiB2片晶与不规则TiC晶粒周围。增加燃烧合成绝热温度,因增加了陶瓷熔体中的Cr基合金相含量,不仅促进陶瓷致密化,而且促使陶瓷凝固组织细化,使得TiB2片晶诱发的裂纹偏转、裂纹桥接、片晶拔出及Cr基合金相所引起的延性相增韧随之增强,进而使陶瓷断裂韧度与抗弯强度增大。     

阴极气膜微弧放电沉积ZrO2-Y2O3陶瓷涂层

采用阴极气膜微弧放电沉积制备ZrO2-Y2O3陶瓷涂层，利用水溶液中阴极气膜放电产生的等离子体的能量，使在阴极表面形成的沉积物直接烧结为陶瓷涂层。研究了沉积涂层的影响因素和涂层形貌及结构。SEM，EDS和XRD分析结果表明，获得的ZrO2-Y2O3陶瓷涂层表面光滑、与基体结合致密、成分和相结构均匀，是一种由Y2O3部分稳定的ZrO2陶瓷涂层。通过测试阴极气膜放电过程中电流随时间的变化以及电位在两电极间分布，分析了阴极气膜放电沉积陶瓷涂层的机制。     

Al2O3/AlTiC/ZrO2/透辉石陶瓷材料的力学性能及微观结构

将金属Al、Al3Ti和TiC以AlTiC中间合金的形式以及ZrO2颗粒共同引入Al2O3基体材料中,热压制备了Al2O3/TiC/ZrO2/AlN复合材料.在此基础上,添加(体积分数)1%透辉石作为烧结助剂,以实现复合材料的液相烧结并促进其致密化程度.复合材料在烧结过程中有新相AlN生成;同时Al、TiC以及Al3Ti释放的Ti原子发生原子重组生成Al2Ti4C.对热压后材料的硬度、断裂韧度和抗弯强度进行了测试和分析;探讨了透辉石对材料致密化程度及力学性能的影响效果;研究了复合材料断面断裂方式的变化对其力学性能的影响;并对AlTiC中间合金的细化特性进行了分析.     

CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质

X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近。荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2 和Eu3 两种价态离子。316,360,379,394,413,462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3 的f-f激发跃迁和5D0-7FJ(J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2 的5d-4f激发跃迁和发射。     

Vitrification and Crystallization Behavior of CaO-SiO2-MgO-Al2O3-Fe2O3-Cr2O3 System

Metallurgical and Materials Transactions B - The effect of basicity and Cr2O3 content on vitrification of the CaO-MgO-SiO2-Al2O3-Fe2O3-Cr2O3 system during a melt-quenched process and the...     

Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics. This work involved a study of the wetting of SiC ceramics by two oxide systems, Al₂O₃ /Dy₂O₃ and Al₂O₃ /Yb₂O₃, which have so far not been studied for application in the sintering of SiC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. Samples of the mixtures were pressed into cylindrical specimens, which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere. The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX). The DRX analysis showed that Al₂O₃ and RE₂O₃ reacted and formed the Dy₃Al₅O₁₂ (DyAg) and Yb₃Al₅O₁₂ (YbAg) phases. The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.     

Viscosity of CaO-SiO2-Al2O3-MgO-B2O3 slags

The viscosity of CaO-SiO₂-Al₂O₃ slags with 8% MgO and 4% B₂O₃ is investigated over a broad range of composition, by means of a simplex-lattice experiment design. For slag of basicity 6–8 in the upper left region of the local simplex, with 15–25% Al₂O₃, 8% MgO, and 4% B₂O₃, the viscosity is high: 9.4–26.4 P over the range 1500–1530°C. Displacement of the slags of basicity 5–8 to the lower region of the local simplex ensures high fluidity in the given range of Al₂O₃ concentration: the viscosity is 1.5–6.1 P over the range 1500–1530°C.     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

Stability of Fluorine-Free CaO-SiO2-Al2O3-B2O3-Na2O Mold Fluxes

Metallurgical and Materials Transactions B - B2O3 and Na2O are key components of fluorine-free mold fluxes for continuous casting, but both are highly volatile, which affects the flux stability....     

Research on Glass Forming Ability of Er2O3 -Al2O3 -B2O3 -SiO2 System

The glass forming range of Er2O3-Al2O3-B2O3-SiO2 system was explored, and the effect of the content of Al2 O3 and Er2 O3 on glass-forming region was experimentally examined. It is shown that the region of glass formation range expends when the content of Al2O3 is changed from 15% to 20%, while it shrinks when the content of Er2O3 is changed from 20% to 30%. At the same time, the glass forming ability of Er2O3-Al2O3-B2O3-SiO2 system was also discussed using a value of β, which is an indication of crystallization tendency of glasses, calculated from thermo-analysis data. It is found that the glass forming ability of Er2O3-Al2O3-B2O3- SiO2 glasses is poor, while the glasses network may be enhanced when Al2O3 is added to the system, the glass forming ability being heightened. In addition, the crystallization temperatures of the rare earth glasses were determined using differential thermal analysis technique. The Er2O3-Al2O;-B2O3-SiO2 glass samples were heat treated at 1000,1100 and 1260℃ respectively. The results show that it is the Er2O3 phase that separates out from the glasses after crystaline heat treatment, and it is tiered up in glasses, as detected through XRD and SEM. This indicates that the phase separation occurs when the glasses are heated, Er3 being mainly distributed in the boron rich phase, then separated out from glasses, while the silicate rich phase remaining glassy state.     

Solid-phase reactions of Ta2O5 with Ga2O3 and In2O3

Conclusions Using the techniques of DTA and x-ray phase analysis, a study was made of the reactions between Ta₂O₅ and M₂O₃ (M = Ga or In), and the phase compositions of the relevant binary systems were determined. The existence was confirmed of stable compounds of composition MTaO₄ and eutectoidally decomposing phases containing 7.5–12.5 mole % M₂O₃. MTaO₄ are dielectrics, whose room-temperature _v is of the order of 10¹⁰ -cm. The temperature dependence of _v of MTaO₄ was investigated in the range 293–873°K and their energies of activation for conductivity were calculated. The melting points, pyknometric densities, dielectric losses, and relative dielectric permeabilities of MTaO₄ were determined.Translated from Poroshkovaya Metallurgiya, No. 2 (110), pp. 69–73, February, 1972.     

X射线荧光光谱法测定Dy_2O_3及其杂质Eu_2O_3,Gd_2O_3,Tb_4O_7,Ho_2O_3,Er_2O_3和Y_2O_3

当前稀土应用范围越来越广,尤其Dy2O3和金属Dy其出口量不断增大．Dy2O3中所含杂质总量通常在0．1％～5％之间,该范围内的测定方法以XRFR为合适,快速、准确、无破坏．1实验部分1．l原理本法采用粉末直接压片法制样,在各元素分析线峰位上测量X射线强度,根据待测元素的X射线荧光光谱强度与含量的定量关系,选择相应的数学模型,由计算机自动计算出待测成份含量．1．2仪器和试剂荷兰飞利浦PW—1400顺序式X射线荧光光谱仪;康柏486计算机;电动小型油压机;万分之一精度分析天平．DyZO399．999％;EnD3,GdD3,ThAn,HoAn,ErD3…     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。