梯度多孔Mg-Ca合金的力学性能研究

主要研究了具有不同孔隙梯度分布的多孔Mg-Ca合金在横向和纵向压缩时孔洞的受力以及变形特征,分析了梯度多孔Mg-Ca合金在弯曲时裂纹扩展机理,并观察了孔隙梯度结构和烧结温度对梯度多孔Mg-Ca合金力学性能的影响。研究结果表明,梯度多孔Mg-Ca合金的力学性能优于均匀多孔材料,随着试样边缘和中心孔隙度差距的增加,试样的抗弯强度、抗压强度和弹性模量均增加,纵向压缩时样品抗压强度和弹性模量的增加优于横向压缩,这主要归因于孔隙的梯度分布导致受力时外加载荷的重新分配。随着烧结温度增加,梯度多孔Mg-Ca合金的力学性能增加,在620℃烧结2h时力学性能达到最佳。     

凝胶注模成形法制备多孔铝及其性能研究

为了开发多孔铝制备新工艺与提高性能,采用凝胶注模法制备了形状较复杂的多孔铝。探讨了固相含量和烧结温度对多孔铝的密度、孔隙率、显微结构及力学性能的影响。结果表明,随固相含量的增加,烧结体密度随之增大,抗压缩性能提高;在不添加烧结助剂的条件下,680℃为最佳烧结温度。制得的多孔铝为开孔结构,孔隙率在34%～53%间可调,平均孔径3.82μm,抗压强度76.8MPa,比表面积0.12m2/g。     

铁尾矿制备SiC/Fe_xSi_y复合材料的工艺及性能研究

在合成SiC/FexSiy复合粉体的基础上,利用高温渗硅反应烧结制备工艺制得了SiC/FexSiy复合材料。研究了合成复合材料的关键工艺参数,确定最佳合成工艺参数为:炭黑配量5%,反应温度1550℃,恒温时间2h,FexSiy含量为5%的复合粉体。复合材料的最大常温抗折强度约为130MPa,且随烧结温度和材料中FexSiy相含量的变化而改变。SiC/FexSiy复合材料的抗折强度先随温度的升高而增加,直至转折温度Tm(900℃),然后随温度的升高而下降。材料的热导率随温度的升高而降低,在20~250℃下降迅速,之后下降幅度减缓。SiC/FexSiy复合材料的线膨胀系数随温度的升高而增加,800℃以后线膨胀系数变化幅度增大。     

表面多孔NiTi-羟基磷灰石/NiTi生物复合材料的制备与性能

利用放电等离子烧结技术制备了表面多孔NiTi-羟基磷灰石(HA)/NiTi生物复合材料,研究了烧结温度对复合材料宏观形貌、微观结构、表面孔隙特征、力学性能及体外生物活性的影响。结果表明:随着烧结温度从800℃提高到950℃,NiTi-HA/NiTi复合材料由复杂的Ti、Ni、Ti_2Ni、Ni_3Ti、HA混合相逐渐转变为单一的NiTi+HA相,内外层界面形成稳定的冶金结合且表面孔隙率与平均孔径呈缓慢减小趋势;同时抗压强度显著提高而弹性模量变化不明显。与传统NiTi、多孔NiTi及多孔NiTi-HA材料相比,950℃温度下制备的NiTi-HA/NiTi复合材料不仅具有良好的界面结合和表面孔隙特征(孔隙率45.6%、平均孔径393μm)、较高的抗压强度(1 301MPa)、较低的弹性模量(10.2GPa)以及优异的超弹性行为(超弹性恢复应变4%)的最佳匹配,而且还具有良好的体外生物活性。     

多孔ZnO/羟基磷灰石生物复合材料的制备与性能

利用放电等离子烧结技术制备多孔ZnO/羟基磷灰石（HA）生物复合材料,研究不同纳米ZnO含量对ZnO/HA复合材料微观结构、孔隙特征、力学性能、矿化和降解性能的影响。结果表明:烧结后ZnO/HA复合材料主要由HA相和ZnO相组成;随着ZnO含量提高,多孔ZnO/HA复合材料孔隙率缓慢增大,抗压强度略有减小,弹性模量变化不大;多孔ZnO/HA复合材料的孔隙率>40%,孔径在50～500 μm之间,抗压强度>148 MPa,弹性模量为6.5 GPa左右,能够满足骨修复材料的要求;模拟人工体液中矿化和降解实验表明,多孔ZnO/HA复合材料浸泡7天后表面开始形成大量类骨磷灰石层,且随着ZnO含量增加,磷灰石形成能力明显增强而降解速率加快。      

温度和甲酸镍含量对制备Zn-Ni合金渗层的影响

为改善渗锌层的防腐性能，通过在渗锌过程添加甲酸镍制备了Zn-Ni合金渗层，分析了不同温度(400℃、450℃、500℃、550℃、600℃)和不同甲酸镍含量(0 g、15 g、44 g、75 g、103 g)对渗层制备过程的影响。采用扫描电镜(SEM,配备有EDS能谱)、X射线衍射仪(XRD)分析了不同试样渗层截面形貌和物相组成；采用电化学极化曲线和阻抗谱(EIS)表征了不同试样在3.5%(质量分数，下同)NaCl溶液中的电化学行为，并通过中性盐雾实验测试了渗层的耐蚀性能；利用显微维氏硬计测试渗层表面至基体不同相层硬度。结果表明：随温度的升高渗层显著增厚，渗层表面硬度降低；随甲酸镍含量的增加渗层明显减薄，渗层中ZnO、Fe₃ZnC_0.5相衍射峰明显增强，渗层中间相层硬度值增大；温度和甲酸镍含量对渗层自腐蚀电位无明显影响，腐蚀电流密度随温度的升高而增大，随甲酸镍含量的增大而明显减小；试样阻抗弧半径和渗层电阻均随甲酸镍含量的增加而增大；甲酸镍含量越高，对盐雾实验白锈的出现抑制越明显，出现红锈的时间显著延长。综上所述，添加甲酸镍显著改善了渗锌层的组...     

凝胶注模成型技术制备氧化石墨烯/HA复合材料的研究

以氧化石墨烯和纳米羟基磷灰石(HA)粉体为原料,采用凝胶注模成型技术制备了氧化石墨烯/HA复合材料。研究了有机单体、浆料固相含量和石墨烯含量对氧化石墨烯/HA浆料粘度的影响,观察了陶瓷浆料的凝胶固化过程并测量了固化后生坯的密度和抗压强度,分析了氧化石墨烯含量对烧结后复合材料抗弯强度和断裂韧性的影响,观察了试样断口的显微组织。研究结果表明,有机单体含量为15%(质量分数,下同),固相含量为45%,氧化石墨烯含量为1.5%时,氧化石墨烯/HA浆料的粘度最佳,为362.9mPa·s,浆料的分散性良好,固化后生坯具有较高的密度和抗压强度。随氧化石墨烯含量的增加,复合材料的抗弯强度和断裂韧度均先增加后降低。当氧化石墨烯含量为1.5%时,1 150℃烧结样品的抗弯强度为81.5MPa,断裂韧性为1.52MPa·m1/2,分别比HA基体提高了151.8%和74.7%,因此添加氧化石墨烯后的HA复合材料的力学性能更佳。     

Ti-C含量对多孔TiC/FeAl复合材料孔型结构和力学性能的影响

以尿素为造孔剂,利用自蔓延高温合成技术制备了多孔TiC/FeAl复合材料,主要考察了Ti-C含量（质量分数为15wt%~35wt%）对多孔TiC/FeAl复合材料孔型结构和压缩性能的影响。当Ti-C含量不高于25wt%时,多孔TiC/FeAl复合材料由毫米孔和孔壁微孔组成规则的复合孔型结构。相互连通的毫米孔产生于尿素颗粒的挥发和液相迁移;微孔尺寸为10~50 μm,产生于Fe-Al-Ti-C粉末的自蔓延过程,孔径随Ti-C含量的增加而增大。通过调整尿素的体积分数,多孔TiC/FeAl复合材料的孔隙率可控制在56.64%~85.35%。当Ti-C含量不高于25wt%时,多孔TiC/FeAl复合材料的抗压强度随Ti-C含量的增加而增大。当Ti-C含量高于25wt%时,多孔TiC/FeAl复合材料壁面微孔形状很不规则,且抗压强度下降。孔隙率约为64.3%时,多孔Fe-Al金属间化合物和TiC/FeAl复合材料（Ti-C含量为25wt%）的抗压强度分别为20.03 MPa和66.68 MPa,对应的应变值分别为4.77%和8.21%。另外,多孔TiC/FeAl复合材料的压缩性能可用Gibson-Ashby模型来解释。     

莫来石含量对钙长石/莫来石复相多孔陶瓷组织结构与性能的影响

以CaCO₃、SiO₂、α-Al₂O₃为原料, 采用泡沫注凝法制备了不同莫来石含量的钙长石/莫来石复相多孔陶瓷, 研究了莫来石含量对复相多孔陶瓷的体积密度、气孔率、抗压强度、热导率及微观组织和结构的影响. 结果表明, 莫来石含量对气孔率有很大的影响, 烧结过程中液相出现引起的收缩是气孔率下降的主要原因; 在气孔率相近的情况下, 莫来石含量较高试样的抗压强度和热导率也较高, 致密的孔壁、长柱状的莫来石晶粒使得复相多孔陶瓷的抗压强度提高. 所制备的钙长石/莫来石复相多孔陶瓷的开口气孔率介于60.8%~75.2%, 抗压强度为12.94~36.95 MPa, 热导率为0.30~1.33 W/(m·K).     

碳纤维增强Cu-Ti3SiC2复合材料的性能与烧结温度的关系

研究了在Cu-Ti3SiC2复合材料中添加2%体积含量碳纤维的致密度、电导率和硬度同烧结温度的关系.实验结果表明,加入碳纤维的Cu-Ti3SiC2复合材料较未加入碳纤维的Cu-Ti3SiC2复合材料的致密度和电导有少许下降,但布氏硬度有大幅度提高.随着烧结温度的上升,碳纤维增强Cu-TiSiC2复合材料的相对密度上升较快,在1 000℃时达到99.21%.电阻率随烧结温度的上升而下降;布氏硬度随着烧结温度的上升而提高,但增幅较缓.     

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.     

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.     

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.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.