原位合成TiB2-TiC0.8-SiC复相陶瓷的微观组织与性能研究

利用热压烧结方法原位合成了TiB2-TiC0.8-SiC复相陶瓷。通过光学显微镜(OM)、X射线衍射分析仪(XRD)和扫描电子显微镜(SEM)对材料物相组成和微观结构进行表征。研究了热压条件下烧结温度对材料物相组成、结构及力学性能的影响。结果表明:烧结温度在1700-1950℃范围内,随着温度的升高,材料的致密度、抗弯强度和断裂韧性都有显著改善。烧结温度为1900℃可得到完全致密的原位合成TiB2-TiC0.8-SiC复相陶瓷,材料的晶粒发育比较完善,条状TiB2和块状TiC0.8晶粒清晰可见。复合材料的维氏硬度、断裂韧性和弯曲强度分别达到23.6 GPa,(7.0±1.0)MPa.m1/2和470.9 MPa。当温度达到1950℃时,由于增强相TiB2晶粒长大,材料的强度降低。TiB2、TiC0.8与SiC颗粒协同,通过裂纹偏转、晶粒拔出、晶粒细化等机制对复合材料起到颗粒增强增韧的作用。     

SiC-C纤维的研制

用聚碳硅烷(PCS)与煤沥青(P)共混,制得了PCS-P共混物。该共混物经熔融纺丝、不熔化处理、高温烧结成形,制得SiC-C纤维,其电阻率随沥青含量增加而减少,强度和模量随沥青含量增加而降低。该共混物是一种既有较高强度又能控制电阻率的新型混杂纤维,可用于结构吸波材料。     

金属间化合物MoSi2及其复合材料的研究和应用

金属间化合物MoSi2具有熔点高、断裂强度对温度不敏感、导电导热性能好、抗氧化等一系列的优良性质，因此作为电热元件和高温结构材料，在航空航天等高技术领域得到了广泛的应用。但是，其低温断裂韧性和高温强度较低，一般可采用不连续的颗粒、连续的晶须或纤维，也可采用固溶体合金化或第二相复合技术来提高其低温断裂韧性和高温强度。MoSi2及其复合材料因其优异性能，也可用来制备层状复合材料和梯度功能材料，还可用来制备各种耐高温保护涂层。     

Ni(NO_3)_2催化酚醛树脂的炭化结构特性及其力学性能（英文）

在酚醛树脂中添加Ni(NO_3)_2,逐步固化、高温炭化后,用X射线衍射、扫描电镜和透射电镜观察表征树脂高温炭化显微结构,并测试树脂炭的抗折强度、弹性模量和断裂能来分析其力学性能。显微结构观察表明:添加质量分数5%的Ni(NO_3)_2会在酚醛树脂炭化结构中生成体积分数约2%的纳米炭纤维,纳米炭纤维交错排布;由于酚醛树脂热解产生的含碳小分子气体成分复杂,在树脂玻璃炭出现了炭纳米纤维与碳纳米管接替生长的现象。力学性能测试结果表明:树脂玻璃炭中原位生成的纳米炭纤维与树脂炭基体有一定的结合强度,能提高树脂玻璃炭的抗折强度、弹性模量;可显著提高树脂炭的断裂能,增强其抗拉强度和断裂韧性。     

Y-TZP/Al2O3复相陶瓷的液相烧结及显微结构

通过在Y-TZP／Al2O3复相陶瓷材料中加入一定的添加剂，可以使其在较低的温度下进行液相烧结，使材料的烧结温度大幅度降低．由于液相的存在，氧化锆晶粒较细，而氧化铝晶粒可以借助液相发育成长柱状，这种形状的晶粒有利于陶瓷材料的力学性能，复相材料仍然保持较高的强度和断裂韧性．     

以钙云母为主相的可切削微晶玻璃的显微结构和性能

研究根据提高云母层结合强度的构想,研制以钙云母为主相可切削微晶玻璃,以钙云母和氧化锆为主相的微晶玻璃,具有棒状,长径比大,相互交错的晶粒,强度184MPa,断裂韧性2.17MPa.m^1/2,比目前临床用VITA提高了一倍,切削性能优良,材料的断裂和加工断口主要是云母层间的解理断裂和准解理断裂,故切削面光滑,易于保证加工的精度。同时说明提高云母层间结合强度是此类材料增强的本质所在。     

低温烧结细晶Y-TZP

通过在Ｙ－ＴＺＰ中加入适量的硅酸盐玻璃添加剂,使其烧结温度明显降低,并且制备出具有细晶粒、高强度的四方相氧化锆增韧陶瓷材料．分析了添加剂含量及烧结温度与材料致密度、显微结构及力学性能的关系,发现在Ｙ－ＴＺＰ材料中加入１ｗｔ％的添加剂,可以使材料在１４００℃下烧结,氧化锆晶粒尺寸约为１００～２００ｎｍ;其抗折强度可达９５０ＭＰａ．     

TC11合金片状组织的热处理改进

αβ钛合金在β区加热以后,就获得片状组织,亦称针状α组织或魏氏组织。这类组织的特点是原始β晶粒粗大,而且具有一个有一定厚度的连续的晶界α。它的断裂韧性、高温持久和蠕变强度较等轴组织的高,但其室温拉伸塑性和高周疲劳强度则比等轴组织的低得多,往往影响常规使用。     

全海深浮力材料的研究与制备

选用缩水甘油醚型环氧树脂、芳香族多胺固化剂和空心玻璃微珠等原材料制备了低密度、高强度的全海深浮力材料,研究了低密度空心玻璃微珠K1的加入量对浮力材料的密度、单轴压缩强度、耐静水压强度和吸水率等性能的影响。结果表明,在空心玻璃微珠总体积分数为66.7%的全海深浮力材料中,加入适量空心玻璃微珠K1取代空心玻璃微珠HM42,能够降低全海深浮力材料的密度,浮力材料的单轴压缩强度不低于132 MPa,耐静水压强度不低于150 MPa,吸水率不高于0.2%。制备的全海深浮力材料有望满足全海深设备的安全使用。      

圆锥压头递增载荷对材料的划痕行为

用Rockwell C金刚石压头对16种材料(2种玻璃、2种聚合物、4种陶瓷、4种金属和4种金属玻璃)进行微米划痕测试。结果表明,这些材料都存在与弹性恢复相关的最大划痕保持率(残余深度与压入深度之比),可作为表观摩擦系数变化曲线的分段过渡点。划痕的表观摩擦系数由黏着摩擦系数和犁沟摩擦系数组成,使用三维力学接触模型可较为准确地表征除金属玻璃外的摩擦系数。材料的初始摩擦系数与泊松比有一定的关系。聚合物(PC和PMMA)因堆积和下沉效应出现独有的双划痕沟槽现象。16种材料的划痕硬度与压痕硬度的比值为0.33~2.5,划痕硬度与体积模量呈线性关系。使用线弹性断裂力学(LEFM)模型和微观能量尺寸效应(MESEL)模型计算了材料的断裂韧性。结果表明,LEFM模型、Akono's MESEL和Hubler's MESEL模型都能较为准确地表征断裂韧性较低材料(玻璃、陶瓷和高分子)的断裂韧性,而对断裂韧性较大的金属材料其表征结果偏差较大。用Liu's MESEL模型可表征断裂韧性较大材料(金属材料和部分金属玻璃)的断裂韧性。材料的断裂韧性,与泊松比呈分段线性相关。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.