炭气凝胶负载Pt基催化剂的制备及其甲醇氧化催化性能

以间苯二酚(R)和甲醛(F)为原料,制备R-F炭气凝胶(RF-CAs).继以后者为载体采用浸渍还原法制备铂基催化剂Pt/CA,并比较其与由相同负载工艺制得的以Vulcan XC-72为载体的铂基催化剂Pt/XC72的催化甲醇氧化反应的性能.结果表明,前者具明显高的甲醇氧化催化活性,显示CAs是一种极具潜在竞争力的燃料电池催化剂载体材料.     

超声频率对碳纳米管结构及其负载PtRu催化剂催化活性的影响

在浓硝酸和浓硫酸混合液中,采用频率分别为25、40、60和80kHz的超声波对碳纳米管(CNTs)进行官能团化处理,运用X射线衍射(XRD)、傅立叶红外(FT-IR)、热重分析(TG)等手段,考察了超声处理对碳纳米管晶相结构、表面基团、含氧基团含量的影响.以不同超声频率处理的碳纳米管作为载体,制备了一系列碳纳米管负载PtRu催化剂,并用X射线衍射技术对催化剂的晶体结构进行了表征.采用循环伏安法(CV)测试了催化剂对甲醇电氧化反应的催化活性.结果表明,采用超声频率为60Hz处理的碳纳米管具有较高的含氧基团含量,用其作为载体制备的PtRu/CNTs60催化剂具有最佳的甲醇电氧化催化活性.     

Co/MR氮掺杂炭气凝胶的制备、结构及氧还原性能

以三聚氰胺、间苯二酚、甲醛为原料,采用溶胶-凝胶法、冷冻干燥等步骤制备出三聚氰胺-间苯二酚-甲醛(MR)干凝胶;并以所制炭气凝胶为载体浸渍硝酸钴,经氮气中高温炭化,得到钴复合氮掺杂的炭气凝胶。考察间苯二酚和三聚氰胺比例、凝胶pH值及炭化条件等对气凝胶结构和催化氧还原活性的影响,采用XRD、XPS、低温氮气吸脱附等方法研究催化剂的结构。随pH值增加,MR气凝胶的介孔分布向小孔移动;当M/R物质的量比为6∶1时,其介孔分布为3.0~4.0 nm。钴复合炭气凝胶多孔结构中存在均匀分布Co金属颗粒和管状炭,Co金属颗粒粒径随炭化温度升高而增加。采用旋转圆盘电极研究催化剂在0.5mol/L H2SO4溶液中的电化学性能,结果表明催化剂具有良好的氧还原活性。     

室温条件下乙腈为溶剂炭气凝胶的制备与机理分析

与传统炭气凝胶制备不同,在室温条件下以乙腈为溶剂,间苯二酚和甲醛为前驱体,盐酸为催化剂,采用溶胶-凝胶、超临界干燥结合高温炭化工艺制备炭气凝胶(密度低至约50 mg.cm-3)。红外光谱、比表面积和孔径分布、扫描电子显微镜(SEM)和X射线衍射等测试表明,所制炭气凝胶是一种类石墨结构的非晶态材料,具有纳米骨架网络结构,比表面积达1 300 m2.g-1。对比不同配比气凝胶的SEM发现,气凝胶的颗粒尺寸为40 nm～70 nm。分析溶胶-凝胶过程中的温度变化和乙腈在凝胶化中作用得知,由于盐酸的催化和反应放热共同作用,实现了室温下间苯二酚和甲醛的加成和缩聚反应,并最终形成凝胶;乙腈在反应中起着一种分散剂的作用。     

石墨烯/炭气凝胶的制备及其结构与性能研究

以间苯二酚(R)和甲醛(F)为炭前驱体原料, 通过溶胶-凝胶法制备石墨烯/炭气凝胶复合材料。采用XRD、Raman、SEM和N₂吸附/脱附等对样品进行结构表征。结果表明: 石墨烯为R和F的聚合提供形核场所, R和F首先在氧化石墨烯(GO)表面聚合, 随着RF含量的增加, 复合炭气凝胶(RF)结构从石墨烯薄片层为骨架的三维网络, 经RF基炭球包裹于石墨烯的网络结构, 最终转变为球形团簇交联的三维网络。石墨烯/炭气凝胶复合材料的比表面积随着RF的增加先增大后减小。当GO与RF质量比为1︰100时, GO/RF-100用作超级电容器电极材料, 在6 mol/L KOH电解液中的比电容达169 F/g, 具有较好的电容特性。     

微波法合成Pt/碳气凝胶催化剂的电催化性能研究

以甲醛和间苯二酚为原料,经聚合凝胶,溶剂置换,常压干燥和高温煅烧制备了碳气凝胶(CA),以其为催化剂的载体,利用间歇式微波法制备了Pt/碳气凝胶催化剂。利用电感耦合等离子光谱仪(ICP)测定了催化剂中Pt的含量,通过透射电镜(TEM)、X射线衍射(XRD)对催化剂的形貌和颗粒粒度进行了表征,结果表明采用碳气凝胶为载体以微波法制备的催化剂粒子分布均匀,电化学测试表明采用碳气凝胶为载体制备的催化剂比以活性炭为载体的催化剂有更大的催化活性。     

Pt/ZrP-Th-CNTs复合催化剂的制备及其对甲醇的电催化氧化

利用硫堇(Th)和碳纳米管(CNTs)对磷酸锆(ZrP)改性,并以改性的ZrP复合材料作为催化剂载体,采用化学还原法制备得到Pt/ZrP-Th-CNTs复合催化剂.SEM研究结果表明,金属铂(Pt)微粒在载体表面具有很高的分散度,且颗粒大小均匀,电极的比表面积也得到较大提高.考察了复合电极在酸性介质中对甲醇的电催化氧化...     

碳纳米管/石墨烯负载PtRu催化剂对甲醇的电催化氧化

以碳纳米管(CNT)和石墨烯(GNS)混合材料作为载体,采用微波还原法将PtRu纳米粒子负载到混合载体表面,制备了PtRu/CNT-GNS纳米催化剂。透射电镜(TEM)结果显示,PtRu纳米粒子均匀地分散在混合载体表面,粒径分布范围较窄,平均粒径约为2.17nm。电化学测试结果表明,与单一碳载体负载的催化剂PtRu/CNT相比,PtRu/CNT-GNS呈现出更高的甲醇氧化活性和更好的抗中毒能力。     

稀释比对常压干燥制备炭气凝胶结构的影响

以间苯二酚和甲醛为原料,氢氧化钠为催化剂,采用溶胶-凝胶法及溶剂置换、常压干燥、炭化等后续工艺,实现了块状炭气凝胶的常压干燥法制备,并考察了稀释比对气凝胶结构性能的影响。采用XRD、BET、SEM及IR等方法对样品进行表征。结果表明:采用氢氧化钠为催化剂制备的炭气凝胶为非晶态,表观密度为1.10g/cm3,比表面积为620m2/g,平均孔径为16.0nm。实验表明,较低的稀释比更有利于制备出表观密度较小、比表面积较高的炭气凝胶。     

甲醇燃料电池纳米催化剂研制成功

厦门大学化学化工学院以XC-72R炭黑为载体,制备出直接甲醇燃料电池阳极PtRu/C纳米催化剂——纳米PtRu/C合金催化剂,其活性与目前商业     

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.