压电陶瓷滤波器铜电极新工艺

压电陶瓷滤波器目前在国内几乎都采用银电极,其制作方法大致分为两类:烧银法和真空镀膜法,前者是将Ag_2O用有机溶剂调制成糊状银浆,再将银浆印制在已灼烧成型的陶瓷片上,经烘干、高温灼烧,使氧化银分解为银渗透在瓷片表面上;后者是在高真空下使银蒸气蒸镀在陶瓷表面上形成银层。复盖了银层的陶瓷片,再在高压下进行极     

6061铝合金微弧氧化陶瓷层生长速度的研究

以变形铝合金6061为试验材料,采用MAO240／750微弧氧化设备、TT260测厚仪和JSM6460扫描电子显微镜,研究了电流密度、占空比、样品尺寸和溶液温度等因素对铝合金微弧氧化陶瓷层生长速度的影响。结果表明：陶瓷层厚度随着时间的延长而线性增大,电流密度越大,陶瓷层生长速度越快,在相同时间内样品表面所达到的电压越高,电压的升高提高了陶瓷层被击穿继续发生内部氧化的能力;占空比大小对陶瓷层生长速度几乎无影响,而电压随着占空比的减小发生微小的上升;恒流氧化时,虽然陶瓷层的生长速度不随样品尺寸变化,但是电压随样品尺寸增大而升高;随着溶液温度的升高,溶液的导电能力增强,陶瓷层的生长速度变快。     

反相微乳液法合成纳米钛酸钡球形颗粒

0引言BaTiO3陶瓷是一种具有高介电常数及优良的铁电、压电和绝缘性能的电子陶瓷材料。不仅是重要的电子陶瓷、PTC陶瓷原料[1],而且也是制备多层陶瓷电容器(M LC C)的必要组分[2,3]。随着现代科学技术的发展,人们更注重材料颗粒的大小和形貌,当材料的粒径达到纳米级时,材料的性能将发生很大的变化。另外,这种具有纳米尺度、球形颗粒的电子陶瓷材料,可能还具有一些新的物理作用,具有潜在的应用价值。B aTiO3粉体的制备方法有:固相煅烧法、化学共沉淀法、溶胶-凝胶法、水热法[4￣11]等。固相法反应温度高(一般1000￣1200℃)、反应活性差…     

(NaPO3)6对AZ91D镁合金微弧氧化陶瓷层电化学腐蚀特性的影响

在Na2SiO3-KOH电解液体系中添加一定量的(NaPO3)6, 利用微弧氧化(MAO)技术在AZ91D 镁合金表面制备了原位生长的陶瓷层. 采用动电位极化和电化学阻抗谱(EIS)技术研究了添加(NaPO3)6前后, 制备的陶瓷层在3.5%(w) NaCl溶液中的室温电化学行为. 结果表明, 添加(NaPO3)6后, 陶瓷层的自腐蚀电位显著上升, 自腐蚀电流密度明显减小. 这主要是由于(NaPO3)6增加了反应过程中基体镁合金表面的“氧空位”和溶液中PO3-4的含量, 促使元素Mg在金属/膜层(M/F)界面上快速形成相应氧化物, 从而增加了陶瓷层的厚度和致密性. 根据电化学反应体系和陶瓷层的特殊结构, 建立了合理的等效电路, 并结合EIS 数据, 分析了添加(NaPO3)6提高陶瓷层耐电化学腐蚀性能的机理.     

添加稀土和重金属氧化物玻璃陶瓷的制备和烧结及性能研究

通过分别添加稀土氧化物和重金属氧化物作为烧结助剂 ,采用电子陶瓷工艺制备了具有非化学计量组成的堇青石基玻璃陶瓷。为了评价玻璃粉末的烧结特性 ,对烧结热处理后试样的密度和显气孔率进行了测定。结果表明 ,两种烧结助剂能促进玻璃的烧结致密化和降低 μ 堇青石向α 堇青石转变的温度并影响玻璃陶瓷的介电性能。玻璃陶瓷的完全致密化温度可以低到 90 0℃。该材料具有低的介电常数 (≈ 5 )和低的介质损耗因子 (≤ 0 2 % )以及合适的热膨胀系数 ((2 80～ 3 5 2 )× 10 - 6 ℃ - 1) ,能够在低于 95 0℃与高导电率的金属如金、铜和银 /钯共烧 ,是一种潜在的低温共烧陶瓷基板材料。     

含铋层状结构型钛酸锶铋高温高稳定压电陶瓷

近年来发现含铋层状结构型比常用的PZT系统压电陶瓷的居里温度高,厚度振动膜纯,介电常数低,压电性能稳定等特点,有利于高温、高频、高稳定的压电应用。     

高安全、高比能固态锂硫电池电解质

锂硫电池具有理论能量密度高、成本低廉和环境友好等优点,是最有前途的下一代高比能二次电池系统之一。当前,基于有机电解液的液态锂硫电池存在多硫化锂穿梭效应、电解液易燃以及锂枝晶等问题,致使电池的库仑效率低、循环性能差,且存在严重的安全隐患。采用固态电解质(如凝胶聚合物、固态聚合物、陶瓷、复合电解质等)替代有机电解液是解决上述问题的有效途径。本文总结了近年来固态锂硫电池电解质的研究现状,评述了各类固态电解质的优缺点及改性策略,重点介绍了陶瓷固态电解质的研究进展。最后,对固态锂硫电池的未来发展趋势进行预测与展望。     

陶瓷化耐火硅橡胶的研究进展

综述了近年来国内外有关陶瓷化耐火硅橡胶的研究进展,介绍了云母粉、碳酸钙、高岭土和纤维类等成瓷填料和低熔点玻璃粉、低熔点氧化物、聚磷酸铵等助熔剂对陶瓷化耐火硅橡胶性能的影响,在此基础上指出了今后陶瓷化耐火硅橡胶研究方向。     

用CTMAB作沉淀剂叶蜡石中二氧化硅的重量测定法

我国对叶蜡石的应用已有近两千年的历史,由于叶蜡石具有绝缘性、耐酸性、导热导电率低、熔点和比热高等特性,目前已广泛应用于耐火材料、陶瓷、玻纤、白水泥、造纸和橡塑等许多工业领域。陶瓷工业是叶蜡石的主要应用领域,主要用于生产建筑陶瓷、卫生陶瓷、精细美术陶瓷和特种陶瓷。     

基于环硼氮烷的高陶瓷产率SiBCN先驱体的合成与性能

聚合物先驱体转化法作为制备SiBCN陶瓷及其复合材料的重要途径,具有成型温度低、产物结构和组成可控等优点.设计合成合适的聚合物先驱体是提高陶瓷产率和性能的关键因素之一,本文采用三氯环硼氮烷(TCB)与乙炔基氯化镁进行反应,合成了乙炔基环硼氮烷,进而与二氯硅烷和二氯甲基乙烯基硅烷进行共氨解反应,制备了聚硼硅氮烷先驱体(PBSZ)并进行了高温裂解.采用综合热分析(TG-DSG)对其陶瓷化过程进行了分析,并采用XRD和SEM对陶瓷化产物的结构进行了表征.PBSZ在室温下是液态,易溶于二氯甲烷和氯仿等溶剂,可加工性优良.基于PBSZ先驱体的SiBCN陶瓷产率超过80%;陶瓷化产物在1400℃以下为无定形状态,在1500℃可形成由α-Si3N4,β-Si3N4,h-BN和SiO2晶体结构组成的陶瓷;陶瓷产物表面致密平整且具有优异的热稳定性和氧化性能,表明聚硼硅氮烷(PBSZ)有望成为高陶瓷产率和高性能陶瓷的重要先驱体.     

Micropatterning of Ni particles on a BaTiO3 green sheet using a self-assembled monolayer

We studied surface modification of ceramic BaTiO(3) green sheets including polyvinylbutyral (PVB) as an organic binder and successfully fabricated a patterned self-assembled monolayer (SAM) which has a region of amino groups and a region of silanol groups on the green sheet. The patterned SAM was then immersed in water containing Ni particles that show negative zeta potential in water. Ni particles were attracted to the amino groups of the patterned SAM that show positive zeta potential by attractive electrostatic interaction. Consequently, a micropattern of Ni particles was achieved using a SAM at room temperature in water. This process can be used to fabricate a thin uniform internal Ni electrode for miniaturized high-performance multilayer ceramic capacitors (MLCC).     

Thermal analysis and microstructural characterization of ceramic green tapes prepared by aqueous tape casting

In this study, aqueous lead magnesium niobate (PMN) slurry formulations were developed for tape casting using a poly(acrylic acid) - poly(ethylene) oxide comb polymer as the dispersant, nonionic acrylic latex as the binder phase and hydroxypropyl methylcellulose as the wetting agent. Concentrated suspensions were cast onto a silicone-coated mylar film, and the effect of acrylic latex on deposition was investigated. Thermal analyses were performed to investigate the mass loss of the green tapes as a function of calcination temperature. Differential scanning calorimetric analyses were made under air and nitrogen atmospheres to investigate the binder distribution through the green tapes. Results showed that it is possible to prepare flexible, crack free PMN thick films using a proper slurry composition in the presence of acrylic latex binder, without using any plasticizer. Additionally, decomposing mechanisms of the acrylic based binder were essentially different in the two atmospheres.     

Direct observation of uncoated spectrin with atomic force microscope

Spectrin molecules extracted from human blood ceil membrane have been examined by atomic force microscopy (AFM) without using shadowing or staining procedures. A drop of the solution containing spectrin molecules was deposited on the freshly deaved mica substrate. After about 1 min, the residual solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air in a constant force mode. The obtained AFM images revealed that the spectrin molecules prepared from the above procedures exhibit several kinds of structures as follows: (i) the compact rod-like spectrin heterodimers with a length of around 100 nm; (ii) bent or curved linear tetramers with a length of around 200 nm; (iii) somewhat curved spectrin hexamers, octomers or decamers with lengths of about 300, 400, or 500 nm; and (iv) high oligomers with a length above 1 000 nm.     

Burnout of Organic Components of Glass Ceramic Composite Tapes: Thermoanalytical investigations

Glass ceramic composite tapes are composed of inorganic raw materials (borosilicate glasses and inert fillers) and organic additives (polymer binder, plasticizer, dispergent, residues of solvent from the tape casting process). Burnout of organics in air is a complex process of vaporization, depolymerization and oxidation. Conditions of this process can be simulated by thermal analysis of plasticizer, various binders and binder/plasticizer mixtures with alumina, prepared by impregnation of alumina powder with corresponding solutions and subsequent drying. This allows a quantitative interpretation of the results of burnout of tapes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Diol—Based Sol–Gel as a Novel Binder for Barium Titanate Ceramics

The relative merits of using a diol-based sol–gel precursor as a binder in the fabrication of barium titanate ceramics made by die-pressing a mixed oxide starting powder have been investigated. The characteristics of powder compacts were compared to samples prepared using a conventional PVB organic binder. The green strength of pellets with the PVB binder was higher than for samples containing the gel, but strength after binder burnout from gel samples was double that of pellets made with PVB. The gel led to improvements in densification during sintering, but these were most noticeable at low sintering temperatures and at intermediate stages of densification. After sintering for 2 h at 1150C, the gel-containing samples reached 75% of theoretical density, some 5% more than for the organic polymer binder. Sintering at 1300C for 2 h, gave a sintered density of ~96% of theoretical density using the gel additive, which was only 2% higher than for the conventional PVB binder system. The decomposition characteristics of the gel were investigated by TGA, FTIR and GC-MS techniques.     

Atomic Force Microscopy,Transmission Electron Microscopy,and Photon Correlation Spectroscopy: Three Techniques for Rapid Characterization of Optimized Self-Nanoemulsiying Drug Delivery System of Glibenclamide,Carvedilol, and Lovastatin

This article looks at atomic force microscopy as an important aid to characterize the self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol in conjunction with other sophisticated technique, viz., transmission electron microscopy and photon correlation spectroscopy. Sizes obtained by processing the atomic force microscopy (AFM) image are comparable with those obtained from transmission electron microscope. Although in the present study, the mean particle size obtained from photon correlation spectroscopy does not correlate to the findings of atomic force microscopy and transmission electron microscopy, but the poly-disperse index values correlate well with the findings of AFM and transmission electron microscopy where uniform particle size was observed in aqueous dispersion of self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol.     

Analysis of the unfolding process of green fluorescent protein by molecular dynamics simulation

Molecular dynamics simulation of the enforced stretching of circularly permuted green fluorescent protein (cpGFP) was performed to observe the detailed process of unfolding of beta-sheets in cpGFP and to clarify the structural change arising from the force. The simulation using the generalized Born method with original force field parameters enabled us to observe the unfolding process of the entire region of the protein and to clarify atom motion of the individual domain during the stretching. The force required for the stretching of cpGFP was estimated from the differential of the computed potential energy. A prominent rise in force appeared three times during the stretching. The amplitude and the position of these three peaks were consistent with the observation in atomic force microscopy (AFM) experiments. Further, the movements of atoms involved in each peak were shown to be closely related to the dissociation of hydrogen bonds. Additional simulations for the unfolding process of titin and spectrin also gave satisfactory interpretation of the results of previous AFM experiments. The difference in the enforced stretching process between cpGFP and wild-type GFP was further discussed through the MD simulation.     

Columnar mesophases based on zinc chlorophyll derivatives functionalized with peripheral dendron wedges

A chlorophyll derivative with a central zinc ion, a methoxy functionality at its 3(1)-position, and functionalized with a second-generation dendron (3,4-3,4,5)12G2-CH(2)OH at its 17(2)-position was synthesized starting from natural chlorophyll a (Chl a). This compound exhibits liquid crystalline (LC) behavior and its mesomorphic properties have been characterized by differential scanning calorimetry (DSC), polarisation optical microscopy (POM), powder X-ray diffraction (XRD), and scanning probe microscopy (SPM). A combination of powder XRD, high resolution scanning tunneling microscopy (STM), and atomic force microscopy (AFM) experiments revealed the formation of nano-segregated well-ordered columnar tubular superstructures consisting of about five molecules in the column stratum. These self-assembled columns are further self-organized into a two-dimensional oblique unit cell lattice. Semiconducting behavior of this compound has been studied by pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) method and charge carrier mobility values of ～10(-2) cm(2) V(-1) s(-1) are observed. Such organized columnar superstructures constructed from semisynthetic zinc chlorins are reminiscent of the tubular organization of the bacteriochlorophyll dyes in the light-harvesting chlorosomal antennae of green sulphur bacteria.     

PVB掺杂有机无机复合SiO2增透膜的制备和表征

以聚乙烯醇缩丁醛(PVB)为有机掺杂剂,正硅酸乙酯为前驱体,氨水为催化剂,利用溶胶-凝胶法制备出了一种新型的有机无机复合二氧化硅增透膜。采用红外光谱、X射线衍射、粒度分析、紫外分光光度法、椭偏测定、原子力显微镜、静滴接触角测量等对膜层性质进行了表征。结果表明：PVB分子的引入并没有引起增透膜结构的变化。在相同的实验条件下,未经PVB掺杂的SiO₂增透膜在720 nm处的峰值透过率为99.8％,而PVB掺杂后的SiO₂复合膜在840 nm处的峰值透过率在99.9%以上。掺杂膜层变厚,峰值透过率朝长波方向移动。掺杂前后增透膜对水的接触角从29°增加到71°,膜层的疏水性得到明显提高。     

Effect of graphene quantum dots on photoluminescence property of polyvinyl butyral nanocomposite

Design and development of new photoluminescence system are much in demand for various engineering and technological applications. The present investigation focused on the influence of graphene quantum dots (GQDs) dispersion in the polyvinyl butyral (PVB) matrix. The structural and chemical interaction of GQD‐dispersed PVB composites was confirmed by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), micro‐Raman spectroscopy, ultraviolet and visible (UV‐Vis), and photoluminescence (PL) techniques. Chemical interaction between the functional groups leads to PL quenching at 455 nm. Changes on crystallite size and interplanar spacing hinders on the structural properties of the nanocomposite. Raman spectroscopy reveals the decrease in D/G intensity ratio influenced by GQD loading wt% in the polymer system. The dispersion and occupied network of GQD in the PVB matrix was confirmed by optical polarizing microscopy (OPM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Effect of electrical conductivity of composites as a function of temperature has been verified. Decrease in direct bandgap as a function of GQD loading confirms the promising PL properties of the prepared composite system. Thus GQD‐derived composites may further be developed as a membrane for improved PL property.