球形SiO2颗粒的合成及反应机理

利用Stober方法合成了球形SiO2颗粒.在乙醇和水的混合溶剂中,以正硅酸乙酯(TEOS)为硅源、氨水作催化剂,在40℃水浴下制备SiO2球形颗粒.通过改变反应物TEOS以及催化剂氨水的加入量,制备了不同粒径的球形SiO2颗粒.利用扫描电镜(SEM)可以看出,随着TEOS和氨水加入量的增加,SiO2颗粒的粒径增大,并探讨了其变化机理.     

溶剂热法制备超细钴粉及其机理研究

以CoCl_2·6H_2O为原料、水合肼N2H_4·H_2O为还原剂,引入AgNO_3·6H_2O作为形核剂,采用乙二醇溶剂热法制备了超细钴粉。通过红外光谱分析探讨了零价Co形成的化学机理,对产物颗粒的相结构、微观形貌和磁性能进行了表征,重点考察了形核剂的加入量及溶剂热温度对钴粉微观结构和磁性能的影响。结果表明,当前驱体溶液中n(Ag~+)∶n(Co~(2+))=1∶100、溶剂热温度为160℃时,可以制得粒径在100nm以下的球状Co颗粒,Co粉分散性良好,且呈现出优异的软磁性能。     

Influence of Gadolinium Concentration Upon Size of Core-shell Gd2O3 : Tb3+ Nanoparticles

以二甘醇作为溶剂,GdCl3和TbCl3的混合溶液作为前驱剂,在室温下加入NaOH后制备出掺杂Tb3+的纳米氧化物颗粒Gd2O3,并以氧化物Gd2O3∶Tb3+为核,在APTES和TEOS的混合溶液中使其包覆-层聚硅氧烷层.结果表明,随着Gd3+溶液浓度的增加,Gd2O3∶Tb3+颗粒尺寸以及包覆了聚硅氧烷层的核壳结构的纳米颗粒尺寸也增加.     

生物素化普鲁兰多糖纳米颗粒制备与表征

合成生物素化普鲁兰多糖衍生物(BP),采用纳米沉淀法制备纳米颗粒(BPNs),考察制备条件对纳米颗粒性质影响,为进一步将其作为药物载体的研究提供基础.通过酯化反应将生物素羧基与普鲁兰多糖连接,生成的衍生物BP通过FI-IR和1H-NMR表征,取代度采用电感耦合等离子体光谱仪(ICP)确定;BPNs进行透射电镜、动态光散射仪和ζ电位仪表征与检测,颗粒表面生物素采用Quant*TagTM Biotin Kit生物素测定试剂盒测定.获得取代度21(BP1),46(BP2),81(BP3)3种衍生物,其中BP2和BP3能够制备纳米颗粒(LBPNs,HBPNs).纳米颗粒呈球形,表面光滑规整,平均粒径100～300nm,水中ζ电位在一17mV左右.制备过程中,粒径随BP浓度(10～50mg/ml)增加而增加((136.2±46.8)nm,(190.8±89.6)nm和(254.5±140.0)nm).调整水相组成为水:元水乙醇(v/v)1:1和1:2时粒径分别为(170.7±30.4)nm和(158.8±21.0)nm.HBPNs和LBPNs表面的生物素量为衍生物的(1.9±0.03)%和(2.0±0.04)%.生物素化普鲁兰多糖衍生物通过纳米沉淀法能制备出纳米颗粒,颗粒表面存在有生物素,颗粒性质受制备条件影响.     

反相微乳液制备纳米SiO2颗粒

微乳液法可以控制纳米颗粒的粒度,在AOT作为表面活性剂的微乳液体系中引入助表面活性剂正丁醇和戊醇,对生成的纳米颗粒起到保护作用,能够形成大小均一、分散良好的纳米SiO2颗粒。随着正丁醇含量的增加纳米SiO2球形颗粒的粒径变大,正丁醇加量0.5mL时粒径为18.7nm,正丁醇加量增加到3mL时粒径达109nm。随着时间的增加,微乳液法制备的纳米SiO2粒径基本保持稳定,而且颗粒变得更加均匀。     

液相还原法制备纳米镍粉

为优化纳米镍粉的液相还原法制备工艺,本文以硫酸镍为主盐,水合肼为还原剂,水浴75 ℃条件下,选取产物纯度、产物粒径、反应速率等关键指标开展工艺优化试验,分别研究了NaOH加入量、溶剂种类、有无分散剂,反应物摩尔比,加料顺序五个变量对于镍粉制备的影响.采用XRD和TEM对产物镍粉进行了表征.结果表明,NaOH的加入量影响产物组成,溶剂种类影响产物粒径大小,分散剂对产物的团聚状态有影响,反应物摩尔比以及加料顺序影响体系的反应速率.最终获得如下的优化工艺：NaOH的加入量在0.015~0.02 mol,乙醇和乙二醇做反应溶剂,加入分散剂PVP,反应物摩尔比为4: 1以及采用氢氧化钠与水合肼混合后再向混合溶液中加入硫酸镍溶液的顺序可以获得较为纯净、粒径较小、分散性好的球形纳米镍粉,并且有较快的反应速率.     

柠檬酸钠对球形NaGd(MoO4)2∶Eu3+纳米晶的溶剂热合成与发光性能影响

采用以乙醇为溶剂的溶剂热法,以三氧化二钆(Gd_2O_3)和钼酸钠(Na_2MoO_4)为原料,柠檬酸钠(Na_3Cit)为表面活性剂,在pH=5,180℃条件下合成出铕离子(Eu~(3+))掺杂的球形双金属钼酸盐纳米粉体[NaGd(MoO_4)_2∶Eu~(3+)],并对制备的产物的物相、形貌以及荧光性质进行表征,探讨了表面活性剂量对产物形貌及发光性能的影响。结果表明,在393nm激发条件下,不同形貌的NaGd(MoO_4)_2∶Eu~(3+)纳米晶在612nm处均有很强发射峰,在Na_3Cit∶Gd_2O_3体积配合比为1∶3,Na_3Cit添加量为1mL,Eu~(3+)用量为5%(wt,质量分数)条件下,合成的球形NaGd(MoO_4)_2∶Eu~(3+)纳米晶颗粒均匀,荧光性较好。由此,表面活性剂Na_3Cit的添加量对产物的形貌及发光性能起到重要作用。     

层状磷酸锆和氧化锆粉体对染料敏化太阳电池电解质性能的影响

利用合成的层状结构的α-ZrP和球形ZrO2颗粒添加到液态电解质中,获得了改善的界面电荷传输特性和离子传输性能。二者在约3%(质量分数)时得到最好的效果。对于颗粒加入对电解质性能的影响进行了分析,认为主要是颗粒表面特性和离子浓度增加带来的Grothus增强机制改善了电解质电化学特性。     

二乙醇胺控制水热合成亚微米球形CoAl_2O_4色料

以CoCl2·6H2O和AlCl3为起始原料,以NaOH为沉淀剂,以二乙醇胺为包覆剂,用水热法合成亚微米球形CoAl2O4色料,使用XRD、TEM和色度分析等手段研究了反应物浓度、nCo/nAl和二乙醇胺加入量对合成色料的物相组成、颗粒形貌及大小和呈色的影响,并从晶体生长动力学角度分析了二乙醇胺包覆控制下球形颗粒形成的原因。结果表明:当Co2+浓度为0.05mol/L、nCo/nAl为1∶2、二乙醇胺添加量为12%(V/V)时,可制得亚微米级球形CoAl2O4颗粒,粒径大多为100-230nm。加入的二乙醇胺能在晶粒成核和生长过程中定向吸附于顶点和边棱处产生空间位阻作用,使颗粒发育成球形。     

纳米CoFe_2O_4颗粒制备及性能研究

铁酸钴具有很多优良特性,应用广泛,其制备方法多为微乳液法,本文中用化学共沉淀法制备了纳米CoFe2O4颗粒。将Co2+和Fe3+的混合液加入沉淀剂溶液中,选用NaOH作为沉淀剂,探讨了温度、保温时间以及NaOH的加入方式对颗粒粒径的影响。用激光粒度分析仪、SEM、XRD、VSM测试了颗粒的大小、形貌、分散状况及饱和磁化强度。结果表明:在制备过程中,适当降低反应温度,缩短反应时间,快速加入NaOH可减小颗粒的粒径,且用此法制备出的CoFe2O4粉末饱和磁化强度为46.776A·m2/kg。     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.