Al_2O_3 基陶瓷摩阻材料的摩擦磨损特性

在ＭＧ－２００磨损试验机上，对以Ａｌ２Ｏ３为基体，分别添加固体润滑剂组元石墨和氮化硼制备的２种陶瓷摩阻材料的摩擦磨损特性进行了试验研究．结果表明：在给定的试验条件下，添加石墨或氮化硼都可以改善材料摩擦性能的稳定性；分别在１００℃，２００℃，３００℃和４００℃下定温试验时，这２种摩阻材料都具有较高的摩擦因数和良好的耐磨性，其中含氮化硼之摩阻材料的耐磨性比含石墨之摩阻材料的更好，前者在４００℃时的磨损率仅为后者在同温时的１／２．     

A NEW METHOD TO DETERMINE THE R-CURVE OF CERAMICS-FRACTURE GRATING METHOD

The etching technique of the single-lined zero-thickness specimen grating is applied tothe surface of the SiC fiber toughening Si_3N_4 ceramic composite specimen.The position of the crackand the crack length during the process of crack extension when the load is applied and gradually in-creased can be determined by recording the output voltage value of the Wheatstone bridge in which theceramic specimen with the fracture grating on is located.The crack-growth-resistance(R-curve) of thismaterialis thus obtained.     

载荷对Al2O3增强Y-TZP陶瓷磨损特性的影响

采用往复式摩擦磨损试验机研究了10%(质量分数计)Al2O3增强四方氧化锆多晶Y-TZP陶瓷材料(简称10ADZ)在不同载荷下的磨损行为与机制.结果表明:随着载荷的增加和滑动时间的延长,10ADZ陶瓷的磨损率增大,但并非呈线性增加,磨损率增长幅度不同;在62 N低载荷条件下,10ADZ陶瓷的磨损机制以犁沟和塑性变形为主;在124 N载荷下其主要的磨损形式为塑性变形、微切削和微断裂;而在310 N的高载荷下其主要的磨损机制为断裂磨损.     

陶瓷人工关节的跑合和摩擦性能研究

研究３种生物陶瓷材料（氧化铝，氮化硅和碳化硅）在水中的跑合及其摩擦特性。结果表明：跑合前，氮化硅－氮化硅摩擦副的起始摩擦因数和稳态摩擦因数最高，碳化硅－碳化硅磨擦副的起始摩擦因数和稳态摩擦因数最低，跑合后，氧化铝－氧化铝摩擦副的稳态摩擦因数最高，碳化硅－碳化硅摩擦副的起始摩擦因数和稳态摩擦因数仍然最低。当摩擦副表面均加工到超光洁状态（表面粗糙度Ｒａ为纳米数量级）时，碳化硅－碳化硅摩擦副的摩擦性能最     

Photoluminescence and energy transfer in Tb/Mn co-doped ZnAl2O4 glass ceramics

We report on Tb³⁺ as efficient sensitizer for red photoemission from Mn²⁺-centers in ZnO-B₂O₃-Al₂O₃-Si₂O-Na₂O-SrO glasses and corresponding gahnite glass ceramics. In comparison to singly or co-doped glasses, the glass ceramics exhibit significantly increased emission intensity. Structural considerations, ESR, and dynamic luminescence spectroscopy indicate partial incorporation of Mn²⁺ as well as Tb³⁺ into the crystalline phase, the former on octahedral Zn²⁺-sites. Interionic distance and charge transfer probability between both species depend on crystallization conditions. This enables control of the energy transfer process and, hence, tunability of the color of photoemission by simultaneous emission from Tb³⁺ and Mn²⁺ centers. Concentration quenching in Mn²⁺-singly doped materials was found at a critical dopant concentration of about 1.0 mol%. The energy transfer process was studied in detail by dynamic as well as static luminescence spectroscopy. Spectroscopic results suggest the application of the studied materials as single or dual-mode emitting phosphor for luminescent lighting.     

Conductivity,structure, and thermal properties of chitosan‐based polymer electrolytes with nanofillers

This paper focus on the effect of nanosize (<50 nm BET) inorganic alumina (Al₂O₃) filler on the structural, conductivity, and thermal properties of chitosan‐based polymer electrolytes. Films of chitosan and its complexes were prepared using solution‐casting technique. Different amounts of Al₂O₃ viz., 3, 4.5, 6, 7.5, 9, 12, and 15 wt% were added to the highest room temperature conducting sample in the chitosan–salt system, i.e. sample containing 60 wt% chitosan–40 wt% NH₄SCN. The conductivity value of the sample is 1.29 × 10^?4 S cm^?1. On addition of 6 wt% Al₂O₃ filler the ionic conductivity increased to 5.86 × 10^?4 S cm^?1. The amide and amino peaks in the spectrum of chitosan at 1636 and 1551 cm^?1, respectively, shift to lower wavenumbers on addition of salt. The glass transition temperature T_g for the highest conducting composite is 190°C. The increase in T_g with increase in more than 6 wt% filler content is attributed to the increase in degree of crystallinity as proven from X‐ray diffraction studies. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of Imidacloprid in Tomato Grown in Greenhouse Based on Copper(II) Phthalocyanine Modified Carbon Ceramic Electrode by Differential Pulse Voltammetry

A new sol‐gel derived electrocatalytic carbon ceramic electrode was prepared by incorporating copper(II) phthalocyanine (CuPc) in a carbon ceramic network. This electrode was used as a sensitive electrochemical sensor for determination of the insecticide Imidacloprid (1‐(6‐chloro‐3‐pyridylmethyl)‐N‐nitro‐imidazolidin‐2‐ylideneamine) by differential pulse voltammetry (DPV). The resulting modified electrode exhibits a cathodic peak potential shifted positively and an increasing in cathodic peak current in comparison with unmodified electrode. The redox properties of this modified electrode at various pH values and CuPc percentage were investigated. The catalytic current obtained from differential pulse voltammetry is linearly dependent on Imidacloprid concentration over the two linear ranges of 0.67‐17 μM and 17‐93 μM with correlation coefficient of R² = 0.9999 and R² = 0.990, respectively. The detection limit for Imidacloprid was found to be 0.28 μM according to lower linear range. Possible interferences from several common pesticides were also evaluated. The inherent stability, high sensitivity, low detection limit and low cost for each preparation are advantages of this sensor. Determination of Imidacloprid in commercial formulation and residual Imidacloprid in tomato grown in greenhouse (protected cultivation) was also conducted. The results obtained from commercial formulation were completely consistent with those obtained through the standard high‐performance liquid chromatography (HPLC) method.     

Nitridosilicates and oxonitridosilicates: from ceramic materials to structural and functional diversity

Silicates are one of the most important classes of compounds on this planet, and more than 1000 silicates have been identified in the mineral kingdom. Additionally, several hundreds of artificial silicates have been synthesized. The substitution of oxygen by nitrogen leads to the structurally diverse and manifold class of nitridosilicates. Silicon nitride, one of the most important non-oxidic ceramic materials, is the binary parent compound of nitridosilicates, and it symbolizes the inherent material properties of these refractory compounds. However, prior to the last decades, a broad systematic investigation of nitridosilicates had not been accomplished. In the meantime, these and related compounds have reached a remarkable level of industrial application. This review illustrates recent progress in synthesis and structure-property relationships and also applications of nitridosilicates, oxonitridosilicates, and related SiAlONs.     

陶瓷靶抗射流侵彻的理论模型及数值模拟

以球型空腔膨胀理论为基础,提出了一个计算陶瓷靶板阻力的损伤模型,该模型考虑了损伤因子对陶瓷靶板弹道性能的影响.结合不可压缩流体力学理论,对射流侵彻陶瓷靶板的侵彻速度进行了理论值计算,并与未考虑损伤的侵彻速度进行了比较,该模型的计算结果更接近实验结果.建立了射流侵彻陶瓷靶板的数值计算模型,对铜射流侵彻陶瓷靶的动态破坏过程进行了研究,讨论了药型罩的锥角、壁厚对射流侵彻结果的影响,结果表明:相同锥角的药型罩,壁厚对陶瓷靶板孔径的影响较小;同壁厚的药型罩,随着锥角的增大,侵彻孔径增大.侵彻速度的数值模拟结果与理论结果进行了比较,得到了较好的一致性.     

An energy criterion for the initiation of interface failure ahead of a matrix crack in brittle matrix composites

The mechanism of interfacial failure occurring as a consequence of the stress concentration induced by a matrix crack located in the vicinity of the interface is analysed. For this purpose, an asymptotic analysis is carried out to assess the competition between the propagation of the matrix crack towards the interface and the nucleation of an interfacial debond. An energetic approach provides a necessary condition comparing the ratio of the interfacial toughness over the matrix toughness to a critical value depending on the elastic mismatch between the fibre and the matrix and the ratio of the interfacial nucleation length over the width of the matrix ligament. Presented results show that the interfacial debonding is enhanced if the matrix is softer than the fibre. Further, a modified condition which does not involve the crack increment ratio is established if the matrix crack lies in the stiffest material.