焙烧温度对滑动弧等离子体制备纳米TiO2光催化剂的影响

采用滑动弧等离子体制备出不同颗粒形貌和锐钛矿相初始含量(f_A)的纳米TiO₂粉体。采用X射线衍射(XRD)、透射电镜(TEM)和物理吸附仪对焙烧前后的样品进行表征, 考察了焙烧温度对纳米TiO₂的晶相组成、晶体粒径、比表面积(S_BET)和颗粒形貌的影响。通过光催化氧化亚甲基蓝反应评价样品焙烧后的光催化活性。结果表明, 滑动弧等离子体制备的纳米TiO₂的锐钛矿相向金红石相转变温度约为650℃, 锐钛矿相向金红石相的转变速率取决于焙烧温度、颗粒形貌和锐钛矿相初始含量。随焙烧温度升高, 球形颗粒的锐钛矿晶体粒径略微增大, S_BET缓慢减小; 非球形颗粒的锐钛矿晶体粒径快速增大, S_BET迅速减小。随着f_A的增加, 纳米TiO₂粉体的光催化表观反应速率常数(k)呈现三种不同的变化趋势: 当f_A<70%时, k随之缓慢增加; 当70%<f_A<85%时, k随之快速增加; 当f_A>85%时, k转为快速降低。     

板钛矿相对TiO2纳米晶相转变的影响研究

本文以Ti(O BU) 4为前驱体 ,采用溶胶 凝胶工艺制备了TiO2 纳米晶。通过X 射线衍射 (XRD)分析证明了所制备的锐钛矿相TiO2 纳米晶中含有一些板钛矿相 ,发现在较低的热处理温度下 ,TiO2 纳米晶就发生了相转变 ,并且板钛矿 金红石相转变的过程比锐钛矿 金红石相转变过程快 ;同时锐钛矿相的晶胞常数c的变化似乎部分归因于有板钛矿相的存在。差热 热重同步分析 (DTA TGA)表明 ,在 36 0～ 5 0 0°C之间 ,可以观察到板钛矿 锐钛矿相转变的存在。最后对TiO2 纳米晶中含有的板钛矿相对锐钛矿 金红石相转变的作用机制进行了简要的分析。     

硫酸亚钛爆轰制备纳米TiO2粒子

以硫酸亚钛,氨水,硝酸铵和黑索金炸药为主要原料,结合沉淀法和爆轰技术对爆轰合成纳米二氧化钛进行了研究,同时利用X射线粉晶衍射仪(XRD)和高分辨透射电子显微镜(HRTEM)等对爆轰灰及经过在空气中500℃,1h处理后的爆轰灰进行测试分析,结果表明:收集的爆轰灰是以金红石和锐钛矿相的二氧化钛为主粒径为(30±10)nm的球形超微粉,同时含有少量的杂质(Ti7O13和C),经过500℃,1h的热处理除杂后,制备的二氧化钛纳米粉末仍为金红石和锐钛矿相组成的混晶,金红石相和锐钛矿相的相对含量比为9∶1,二氧化钛晶粒有轻微长大现象.     

初始压力对气相爆轰制备纳米SnO2的影响

通过爆轰H2、O2和SnCl4的混合气体来制备纳米SnO2是一种新的纳米SnO2的合成方法。通过XRD、TEM、HRTEM和纳米激光粒度仪对其晶型、形貌和粒径进行了表征,总结了初始压力对产物的影响。结果表明,合成的纳米SnO2为纯净的金红石相,且晶粒不存在缺陷。随着初始压力的提高,SnO2的晶粒粒径减小,但颗粒尺寸却变大,颗粒呈球形,出现团聚,分散性变差。     

TiO2纳米微晶的RF-PCVD法制备及表征

以TiCl4为原料,采用高频等离子化学气相沉积(RF-PCVD)法制备了TiO2纳米微晶,考察了控制粒径大小及晶相转化的关键操作条件.借助XPS、TEM、XRD、BET等技术对颗粒的化学组成、形貌、晶相结构等进行了表征.研究表明:所得TiO2纳米微晶大部分为球形体颗粒,粒径30～50 nm,单分散性良好;颗粒中锐钛相和金红石相两相共存,结晶完整;金红石相含量在26.7%～53.6%之间可调.     

混晶结构纳米TiO2粉的光催化活性

以钛酸四丁酯为钛源制备混晶结构纳米TiO2粉,研究了纳米TiO2的光催化活性与颗粒晶相结构之间的关系．结果表明,当金红石相的质量分数少于18．53％,光催化活性随着金红石相的增多而降低;当金红石相的质量分数为18．53％-28．2％时,随着金红石相的增多,光催化活性逐渐增强,在28．2％附近具有最高的光催化活性,与纯锐钛矿结构纳米TiO2粉的光催化活性相当;金红石相含量继续增加,则光催化活性逐渐降低．适量金红石相的存在有利于锐钛矿相中的电荷分离,使光催化活性提高．     

添加磷酸根对纳米二氧化钛晶相的控制

以TiCl4为前驱体添加磷酸盐通过水热法制备了纳米TiO2。通过X射线衍射仪、差热分析仪、扫描电子显微镜、比表面仪(BET)和光化学反应器等手段对所制备的TiO2的颗粒晶型、失重、形貌、比表面和降解罗丹明B的能力进行了表征。结果表明,随着磷酸根的添加,TiCl4水解生成的TiO2的晶型由纯金红石型向锐钛矿型转换,且所合成的锐钛矿和金红石的混晶样品的光催化活性明显高于单独晶相的光催化活性。     

钛酸盐一维纳米材料向TiO2纳米材料的水热转化研究

采用强碱性水热处理法分别控制第一次水热反应为160℃和200℃,制备出一维纳米管和纳米棒2种形貌的产物,将其作为第二次水热反应的前驱体,考察了第二次水热体系中pH值和温度对TiO2纳米材料的晶相组成及其微观形貌的影响;采用XRD、TEM以及HRTEM对样品进行了分析.结果表明,当以纳米管为前驱体时,除在pH=0的体系中得到了以金红石相为主的单晶纳米棒外,在pH值为2、4和7的条件下均得到了单晶纯锐钛矿相TiO2纳米颗粒.当以纳米棒为前驱体时,在pH=0的体系中得到了金红石相与板钛矿相共存的纳米棒和纳米颗粒混合产物;在pH值为2、4和7的条件下均得到了纯锐钛矿相TiO2纳米棒;当二次水热温度低于180℃时,前驱体没有转化完全,所得产物为前驱体与锐钛矿相TiO2共存的纳米棒;当水热温度为180℃和210℃时,产物为纯锐钛矿相纳米棒.     

煅烧温度对二氧化钛纳米晶性能的影响

研究了不同煅烧温度下,锐钛矿相、混晶和金红石相二氧化钛纳米晶的 粒径、比表面积和吸收光谱的变化。经相同的温度煅烧后,金红石相二氧化钛纳米晶的生长速率和比表面积下降速率均大大高于锐钛矿相,表明高温反应或煅烧难以获得金红石相纳米晶,真空热处理的金红石相二氧化钛纳米晶可以保持较高的比表面积和较小的粒径,但易导致非化学配比、晶格缺陷并降低了粉体的性能。     

纳米二氧化钛粉体晶相控制实验研究

在水解－沉淀法制备纳米TiO2粉体的过程中，使用不同的沉淀剂获得了晶相不同的纳米TiO2粉体，使用混合沉淀剂，通过控制沉淀剂的比例，制备了晶相组成（金红石与锐钛矿比例）不同的纳米TiO2多晶粉体，采用相同的粉体制备工艺，不同的后续处理工艺，探讨了锐钛矿向金红石转变的相变温度，经分析研究后认为，水解－沉淀法制备的纳米粉体中的锐钛矿向金红石红转变的温度为500－800℃，完全转变的温度在800℃以上；纳米TiO2多晶粉体的晶相组成不仅与沉淀剂的种类，混合沉淀剂中沉淀剂的比例和粉体的煅烧温度有关，而且与粉体的后续处理工艺和粉体表面界面相的稳定性有关。     

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.     

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.     

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.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to