用简单工艺制备零电阻温度为92K的超导体

自1911年 Onnes 发现汞的超导电性后的75年中,虽经大量研究工作,超导材料的临界温度仅达23.2K(Nb_3Ge)。1987年2月以来,陆续报道关于 Y-Ba-Cu-O 系超导材料研制的初步结果,这类超导体在液氮温区呈现零电阻。本文介绍一种 Y-Ba-Cu-O 系陶瓷超导体的研究结果,其化学组成与上述文献所述不同,且烧结与热处理工艺甚简单。     

热压烧结对Co—Mn—Ni—O热敏材料均匀性的影响

热压烧结能够提高热敏材料的致密度，减少气孔率，且抑制了晶粒的生长。从考察热敏电阻的一致性出发，给出了热压块体材料的电阻率及Ｂ值分布，并讨论了热压材料分散性增大的原因。     

Y-Ba-Cu-O厚膜超导材料

本文报导了采用丝网印刷法制备 Y-Ba-Cu-O 系厚膜超导材料的工艺以及热处理对厚膜超导体微结构、超导电性的影响。在 ZrO_2基片上烧出的厚膜,其临界温度 T_(c(p-o))>77K。     

热压Beta-Al_2O_3的显微结构与离子电导性的关系

研究了不同组成的 Beta-Al_2O_3在热压过程中的显微结构的变化及其对材料的离子电导性的影响。实验发现,同一组成的热压 Beta-Al_2O_3材料,其电导性除与材料的相组成有关外,还与材料的显微结构,致密度及其电导的测试方向有很大关系。气孔数量超过一定值时,对 Beta-Al_2O_3的离子电导率有很大影响。另外,用理想的多晶离子导体的测量等效电路及电导测量结果解释了 Beta-Al_2O_3的复平面交流阻抗谱形状与温度和显微结构的关系。     

Y-Ba-Cu-O超导涂层的研制

用等离子喷涂工艺制备了 Y-Ba-Cu-O 高临界温度超导涂层,涂层的初始转变温度为101K、零电阻温度为86K。电阻率与磁化率的测量结果表明这种超导涂层具有与烧结超导块体相类似的性能,X 光衍射谱显示出涂层主要由 YBa_2Cu_3O_(?)单相化合物组成。     

新型高温超导复合材料的制备及其电磁、摩擦学性能研究

采用热压技术制备出YBCO/CU高温超导复合材料,复合材料中超导相的结构未受破坏,并且由于Cu的存在改善了材料的机械性能,因此相对于常规材料,该复合材料具有特殊的低温电磁学性能,并在低温下表现出与超导状态密切相关的摩擦学性能。     

CaO—MgO—Al2O3—SiO2—F系可切削微晶玻璃的晶化机理研究

在CaO-MgO-Al2O3-SiO2-F系可切削微晶玻璃体系中，本研究分析了K2O和ZrO2c对玻璃析晶和显微结构的影响，探讨了晶化机理。K^ 促使云母相的生成和球晶的形成，晶化过程中，云母和顽辉石互为外延生长，使球晶中条状晶解离为片状晶。ZrO2与F^-一起促使玻璃晶化后形成棒状云母晶粒，并具有晶粒长径比大、相互交换的显微结构。     

Sol—Gel法制备YBa2Cu3O7—δ—Agx复合超导材料的显微结构与性能

研究采用Ｓｏｌ－Ｇｅｌ法制备ＹＢ２Ｃ３Ｏ７－δ－Ａｇｘ复合超导材料的显微结构与性能的关系，Ａｇ的加入能使ＹＢａ２Ｃｕ３Ｏ７－δ相晶粒细化，结晶度提高，致密度增加，晶界无序区域变窄，这些都有利于材料性能的提高，但过多的加入Ａｇ则导致材料性能下降。对Ａｇ的作用机理作了初步探讨。     

ZrO2（YSZ）衬底和YBa2Cu3O7—δ超导膜的相互作用

研究了不同晶向的 ZrO_2(YSZ)与 YBa_2Cu_3O_(?)超导膜的相互作用。结果表明:衬底 ZrO_2的晶向对YBa_2Cu_3O_(7-δ)晶粒取向有明显影响,在<100>ZrO_2上制备的超导膜,超导晶粒 c 轴平行于衬底表面,出现择优取向;在 Y-Ba-Cu-O/ZrO_2上铜晶粒的析出是由于超导膜与 ZrO_2界面反应引起的;用俄歇能谱(AES)和背散射技术(RBS)都观察到了 Ba、Cu 原子向衬底的内扩散;同时,实验证实了在 ZrO_2衬底上热蒸发(?)薄层 Ag 对衬底反应有强压制作用,并在 YBa_2Cu_3O_(7-δ)/Ag/ZrO_2样品中观察到了超导晶粒 c 轴在垂直于衬底方向出现择优取向。     

原位生长石墨烯增强铜基材料的制备及其热性能研究

以廉价的蔗糖为碳源,在片状铜粉表面原位生长了石墨烯,并采用热压烧结制备不同石墨烯含量的铜基材料。通过XRD、SEM和激光导热分析了蔗糖含量对铜基材料的相、微观形貌以及热导率的影响。结果表明,在H₂/Ar气氛下,800℃处理15 min即可在片状铜粉上原位生长出石墨烯,且分散均匀,与Cu基体结合良好,有利于增强其热性能。当石墨烯含量为0.73%(体积分数)时,铜基材料的热导率达到339W/(m·K),较纯铜提高了19.3%;此外,在50～300℃温度范围内,其热膨胀系数也明显低于纯Cu样品。     

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.     

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.……     

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.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from