双组元掺杂钛硅再结晶石墨传导性能的研究

用煅烧石油焦作填料,煤沥青作粘结剂,钛粉和硅粉作添加剂,采用热压工艺制备了一系列双组元掺杂再结晶石墨.考察了不同质量配比的添加剂对再结晶石墨的热导率、电阻率和抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂15wt％钛粉再结晶石墨的传导以及力学性能有较大幅度的提高.在掺杂钛粉15wt％、硅粉<2wt％时,双组元再结晶石墨的常温热导率随着硅粉的掺杂量的增加有所提高.当掺杂钛粉及硅粉分别为15wt％和2wt％时,再结晶石墨RG-TiSi-152的常温热导率可达494W/m·K.但是当掺杂钛粉15wt％、硅粉>2wt％时,随着硅粉的继续增加,再结晶石墨的常温热导率反而降低.而双组元掺杂钛硅再结晶石墨的导电以及力学性能却随着硅粉的掺杂量的增加而降低.XRD分析表明,对于双组元掺杂钛硅再结晶石墨而言,钛元素最终在材料中以碳化钛形式存在,而硅元素则大都以气态形式被逸出,XRD物相图谱中未发现硅及其碳化物的存在.材料RG-TiSi-152的微晶尺寸La以及晶面层间距d₀₀₂分别为864和0.3355nm.     

掺杂钛催化机理及其再结晶石墨导热性能的研究

用煅烧石油焦作填料、煤沥青作粘结剂、钛粉作添加剂,采用热压工艺制备了一系列不同质量配比的掺杂钛再结晶石墨.考察了不同质量配比的添加钛对再结晶石墨的热导率、抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂钛再结晶石墨的热导率、抗弯强度均有较大的提高.室温下,RG-15再结晶石墨的层面方向热导率可达424W/(m·k),抗弯强度可达50.2MPa.微观结构分析表明,少量的掺杂钛,即可使材料达到很高的石墨化度;过多的钛掺杂量不利于材料的热导率以及抗弯强度;原料中掺钛量为15wt％时,再结晶石墨的微晶发育以及排列程度最好,此材料的石墨化度为96.4％,微晶参数La为306nm.XRD物相分析表明,钛元素在再结晶石墨中以碳化钛的形式存在.钛对再结晶石墨制备过程的催化作用可以用液相转化机理来解释.     

石墨化温度及掺硅组分对再结晶石墨传导性能及微观结构的影响

用煅烧石油焦作填料 ,煤沥青作粘结剂 ,分别以硅粉、碳化硅和二氧化硅 3种含硅组分作添加剂 ,采用热压工艺制备了再结晶石墨。考察了石墨化温度以及单组元掺硅组分对再结晶石墨的热导率、电阻率和抗折强度的影响及其微观结构的变化。实验结果表明 ,对于掺硅组分相同的再结晶石墨 ,材料的导电、导热性能随着石墨化温度的升高而增强 ,但其力学性能却随之降低。当掺硅粉的热压再结晶石墨再经 2 80 0℃石墨化处理后 ,材料RG Si 48沿石墨层方向的常温热导率可达 3 3 2W /(m·K) ,电阻率为 4.94μΩ·m。对于相同工艺及硅含量的不同掺硅组分再结晶石墨 ,以掺入硅粉对材料综合性能最理想 ,而掺入二氧化硅对材料的综合性能较差。XRD分析表明 ,不论掺硅组分是硅粉、碳化硅还是二氧化硅 ,硅组分最终在再结晶石墨内均以α SiC形式存在 ,甚至在石墨化温度高达 2 80 0℃时 ,再结晶石墨内仍有α SiC存在。对其微晶参数进一步分析表明 ,随着石墨化温度的升高 ,掺杂硅组分的催化作用进一步加强 ,再结晶石墨的微晶尺寸La 迅速增大 ,石墨微晶的晶面层间距d0 0 2 也迅速降低。材料RG Si 48的微晶尺寸La 以及晶面层间距d0 0 2 分别为2 5 7nm和 0 .3 3 5 77nm。     

ZrB2/C复合材料的性能及微观结构研究

采用热压工艺制备了ZrB2／C复合材料，考察了ZrB2掺杂量对材料抗弯强度、热导率、电阻率的影响以及微观结构的变化．结果表明：随ZrB2含量增加，材料抗弯强度和热导率不断升高，在掺杂量为10％时，抗弯强度达到最大值131MPa，热导率达到161W／m．K的最大值，此后，抗弯强度和热导率随掺杂量增加而降低．然而，材料的电阻率随ZrB。含量的增加不断下降．微观结构分析表明，随着ZrB2掺杂量增加，材料的石墨化度和微晶尺寸增大，晶面层间距减小．材料的微观结构强烈地影响着材料的力学、导电、导热等宏观性能．     

掺钛石墨导电性及其微观结构的研究

研究了不同钛掺杂量的再结晶石墨的电阻率与微观结构。以探讨掺杂组元对材料导电性能的影响。实验结果表明,与相同工艺条件下制得的纯石墨相比,掺钛石墨具有高密、高石墨化程度以及极低的电阻率的特点,微观结构分析表明,钛对材料的石墨化过程中具有催化作用,掺杂石墨材料中钛掺杂量对材料的石墨化程度有很大影响：少量钛掺杂量即可使材料达到高的石墨化程度,过多钛掺杂量不利于其电阻率的降低,分析表明钛元素在材料中是以碳化钛形式存在,但在制备过程中,有少量钛逸失,雁而在材料表面形成孔隙,而这些对材料的性能有不利的影响。     

天然石墨/陶瓷复合材料的制备及其性能

为了拓展天然石墨的应用领域，通过热压工艺，在天然石墨中掺杂B、Si和Zr陶瓷组元，制备了天然石墨／陶瓷复合材料，利用SEM、XRD等分析手段研究了材料微观结构，并探讨了掺杂组元以及天然石墨颗粒大小对材料性能的影响．结果表明：掺杂Zr可有效地提高石墨材料的热导率，B的加入可有效地提高石墨材料的力学性能，而Si的加入可加速Zr对石墨材料的催化石墨化；随着天然石墨粒径的增加，制得石墨材料的热导率也随之增加，其中，以粒径为13μm的天然石墨制得的材料强度和密度为最优。     

莫来石纤维增强SiO2气凝胶复合材料的制备及性能研究

以正硅酸乙酯为硅源,采用溶胶-凝胶及超临界干燥技术制备了掺杂莫来石纤维的SiO2气凝胶复合材料,并对材料的热学性能和力学性能进行了测试,结果表明:SiO2气凝胶复合材料的热导率与其密度、温度和纤维添加量有关;添加莫来石纤维可以明显提高SiO2气凝胶的弹性模量和机械强度,改善材料的力学性能;莫来石纤维添加量控制在3%左右可以使SiO2气凝胶材料保持较低的热导率和较高的机械强度.     

锰掺杂对PMN-PZT陶瓷介电性能的影响

研究了锰掺杂对富锆PMN-PZT（铌镁酸铅一锆钛酸铅）陶瓷材料的相组成、微观结构、介电性能等方面的影响，并对实验结果作出物理机理的解释。实验结果表明：适量的锰掺杂有助于陶瓷晶粒的生长，并能有效地降低PMN-PZT陶瓷材料的介电常数和介电损耗，在锰掺杂量为3．0％（原子分数）时，εr：197、tanδ=0．15％，作为用于红外热释电探测器的陶瓷材料具有良好的介电性能。     

多层石墨/硅树脂导热复合材料的制备与性能

以硅树脂为基体材料,多层石墨为导热填料,采用旋转搅拌球磨法制备了多层石墨/硅树脂导热复合材料,研究了填料对多层石墨/硅树脂复合材料热导率、热膨胀系数(CTE)和热稳定性的影响.结果表明,多层石墨在硅树脂中分散性良好.多层石墨/硅树脂复合材料的热导率随多层石墨填充量的增加而增大,填充质量分数为45％时,热导率达到2.26W· (m· K)-1,超过此值之后热导率开始下降.随着填料的增加,多层石墨/硅树脂复合材料热膨胀系数减小.与纯硅树脂相比,多层石墨/硅树脂复合材料热稳定性高.相同填充量下多层石墨/硅树脂比SiC/硅树脂、AlN/硅树脂的热导率高得多,这说明径厚比大的片状填料更易形成有效接触和导热网链.     

石墨还原一次烧成SrTiO3基电容—压敏复合功能陶瓷材料的研究

采用石墨还原一次烧成工艺制备了ＳｒＴｉＯ３基电容－－压敏复合功能陶瓷材料探讨了施主Ｎｂ，受主Ｍｎ掺量对材料介电性能的影响。结果表明：Ｎｂ２Ｏ５的掺杂量在０．６ｍｏｌ％时可获得高介电常数，低电阻率的材料；Ｍｎ有助于形成晶界势垒，提高材料的压敏非一，Ｍｎ（ＮＯ３）２添加量为０．０５－０．０６ｍｏｌ％可获得电容－压敏综合性能较好的陶瓷材料，通过对比空气中烧成和石墨还原一次烧成新工艺，认为石墨还原烧成工艺     

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 ...     

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     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.