共沉淀法制备CoAl2 O4陶瓷颜料及其呈色机理研究

采用共沉淀法制备CoAl2 O4陶瓷颜料,并通过XRD、SEM和XPS表征陶瓷颜料的组成、形貌和元素价态,研究Co/Al比、溶液pH值和煅烧温度对CoAl2 O4陶瓷颜料呈色的影响,并探讨其呈色机理。结果表明：所得CoAl2 O4陶瓷颜料均具有典型的尖晶石结构,当Co/Al比为0.7∶2、溶液pH值为11、煅烧温度为1200℃时可以获得彩度较高的蓝色CoAl2 O4陶瓷颜料。 CoAl2 O4陶瓷颜料的呈色变化主要与所得产物中Co元素的价态有关,当Co含量过高或者前驱体溶液的pH值较大时,产物中含有Co3 O4( Co4+),进入CoAl2 O4后形成固溶体导致其晶格发生畸变,从而使得陶瓷颜料呈现绿色。     

烧结升温速率对钛酸钡陶瓷压电性能的影响

采用固相反应方法在不同烧结升温速率下制备了BaTiO3陶瓷,并对陶瓷样品的晶体结构、表面形貌、介电、压电和铁电性能进行了测试和分析.结果表明:当烧结升温速率为3 ℃/min和5 ℃/min时陶瓷均为四方钙钛矿晶格结构,随升温速率的增大,四方相程度增强,材料平均晶粒尺寸减小,压电系数和铁电性能随之降低,但介电常数随之增大,当烧结升温速率为5 ℃/min介电常数最大,其值为3144.当烧结升温速率为1 ℃/min时陶瓷为正交钙钛矿晶格结构d33和Pr最大,其值为Pr=10 μC/cm2和d33=193 pC/N.     

Fracture analysis on a layered multiferroic smart structure containing non-periodic interfacial cracks under magnetic/electric and mechanical loadings

The problems of periodic cracks have been widely solved in existing literature of fracture mechanics. Although the assumption of periodicity facilitates the theoretical derivation, practical multiple cracks in most cases are not periodically distributed in materials and structures. The present article performs fracture analysis on a piezoelectric/piezomagnetic/piezoelectric (PE/PM/PE) tri-layered smart structure containing nonperiodic interfacial cracks under magnetic/electric and mechanical loadings. The methods of dislocation simulation, Green's function and Cauchy singular integral equations are employed to solve the problem. Stress intensity factors (SIFs) are numerically calculated, and parametric studies are conducted to demonstrate the variation laws of SIFs versus geometrical parameters. The obtained conclusions may provide references for the optimal design of PE/PM/PE smart structures.     

功能梯度压电材料圆环在位移和反对称电势边值条件下的解析解

采用了在径向极化情况下横观各向同性的线性本构关系,考虑了材料性质沿径向的梯度分布,对功能梯度压电材料圆环在给定的位移和电势边界条件下,导出了问题的一般解．推导了外壁固定、接地,内壁沿垂向有一微小位移、电势为反对称分布问题的解析解,并计算了该问题在位移和电势作用情况下的位移、电势在不同梯度分布时的数值结果．     

COMBINED DAMAGE FRACTURE CRITERIA FOR PIEZOELECTRIC CERAMICS

Mechanical and electrical damages are introduced to study the fracture mechanics of piezoelectric ceramics in this paper. Two kinds of piezoelectric fracture criteria are established using the method of least squares combined with a damage analysis of the well-known piezoelectric fracture experiments of Park and Sun‘s. One is based on a linear combination of the mechanical and electrical damages and the other on their nonlinear combination. When the combined damage D is up to its critical value De, piezoelectric fracture occurs. It is found from the qualitative comparison of the numerical results with the experimental data that the nonlinearly combined damage fracture criterion can give a better prediction of piezoelectric fracture. And it is concluded from the nonlinearly combined damage fracture criterion that a negative electric field impedes fracture whereas the effect of a positive electric field on fracture depends on its magnitude.     

THREE-DIMENSIONAL INTERACTIONS OF A HALF-PLANE CRACK IN A TRANSVERSELY ISOTROPIC PIEZOELECTRIC SPACE WITH RESULTANT SOURCES

I. INTRODUCTIONBecause of the widespread application and intrinsic brittleness of piezoelectric ceramics, significantattention is being paid to the crack problems of piezoelectric ceramics. The last decade has seen a lotof three-dimensional studies of crack in piezoelectric ceramics[1??9]. In addition, the electroelastic fieldin a transversely isotropic piezoelectric space with a half-plane crack subjected to symmetric normalpoint forces, antisymmetric tangential point forces and point ch…     

无机盐/陶瓷基超微结构多孔介质熔化过程传热研究

对一种应用于工业炉的蓄热器、太阳能中央接受塔的储能系统微米级颗粒度下含有无机盐的陶瓷多孔材料的熔化加热过程进行理论研究,在研究中考虑陶瓷基体和无机盐热物性、空隙率和融盐汽化率的影响。计算结果表明,较大的陶瓷骨架孔隙率和相变潜热、较小的导热系数造成温度和固液界面位置的变化变慢,但对气相界面的生成和移动影响不大。     

Microstructure and thermal properties of quasi-equal rare earth substitution Y0.5Gd0.5Ba2Cu3O6.94 superconductor

Sintering effects in YBa₂Cu₃O_z samples with quasi-equal rare earth substitution have been investigated. It has been shown that the Y-123 type compound can be formed when gadolinium is partially substituted (in this case 50% atomic substitution) for yttrium. The superconducting compound was obtained by the optimized ceramic method, including solid-state reaction, melting and sintering, controlled by X-ray diffraction. The microstructure was investigated by SEM and energy dispersive X-ray analyses. An AC susceptibility measurement has shown that T _c =93 K. Temperature-dependece of the thermal conductivity (4.5–300 K) of the polycrystalline Y_0.5Gd_0.5Ba₂Cu₃O_6.94 sample was also measured.      

BiMnO_3改性BNT-BKT压电陶瓷的研究

为了提高BNT基压电陶瓷的电性能,采用传统的陶瓷制备方法,制备了一种Bi基的钙钛矿型无铅压电陶瓷 (1-x)Bi_(0.5)(Na_(0.82)K_(0.18))_(0.5)TiO_3-xBiMnO_3 (简写为BNKT-BMx).研究了Bi基铁电体BiMnO_3对该体系陶瓷微观结构和压电介电性能的影响.结果表明:在所研究的组成范围内陶瓷材料均能够形成纯钙钛矿固溶体,微量BiMnO_3不改变该体系陶瓷的晶体结构,但促进晶粒生长.随着BiMnO_3含量增加,低温介电反常峰消失,高温介电峰出现频率分散性.随BiMnO_3含量增加,压电常数d_(33)和机电耦合系数k_p先增加后降低,在x=0.01时,k_p=0.333,x=0.015时,d_(33)=170 pC/N,为该体系陶瓷压电性能的最优值.     

骨的力–电效应研究方法与进展

骨组织在受到应力作用(正常的生理活动)变形后在骨内产生电位的现象称为骨的力–电效应,它主要包括压电效应和动电效应.研究骨在动态过程中产生的电位幅值和分布特点,不仅是了解电刺激骨生长机理的必要步骤,也是实现骨治疗和重建的生理基础.它一方面是用数学方法来描述外力作用下其电位大小与应力、应变、应变率及加载速率的关系,另一方面是考察生理环境(pH值、离子浓度、温度、湿度等)对电位的影响.首先对力–电理论进行了简单的介绍,重点总结了其研究方法,包括理论模型和分离式霍普金生杆冲击、弯曲变形及缓冲液中的动态测试等实验方法.此外,对骨替代材料和牙本质领域的力–电效应研究也进行了一定的综述.