乳液法制备单分散纳米二氧化锰

以亚硫酸氢钠(NaHSO3)和高锰酸钾(KMnO4)为原料,通过W/O乳状液模板技术制备了单分散纳米MnO2.用SEM和FT-IR手段对样品的形貌和成分进行了表征,并与均相反应制得的样品进行了比较.结果发现用本方法制得的纳米MnO2微粒单分散好,球形更规整,粒径大.FT-IR谱图也同时反映了粒径不同的两种样品所出现的量子尺寸效应.结合实验事实和样品特性,初步探讨了单分散纳米MnO2的形成机理.     

核孔膜乳化法制备单分散壳聚糖微球

选择壳聚糖溶液为分散相,液体石蜡为连续相,首次采用核孔膜乳化方法制备壳聚糖微球.乳滴经戊二醛交联固化后所得微球球形度和单分散性良好(分散系数＜20%).主要研究了核孔膜孔径大小、油水相体积比、表面活性剂种类及用量、温度和固化时间对微球制备的影响.结果表明,膜乳化法是制备单分散微球的良好方法.     

PS微球的制备及三维胶晶模板的组装和应用

研究了PS微球合成中单体、引发剂和乳化剂浓度以及聚合温度对粒径及分布的影响。采用高速离心沉淀法、恒温加热蒸发诱导法和自然沉降法对单分散PS微球进行了组装,得PS胶体晶体模板,并以其为模板制备了锂离子筛前驱体Li4Mn5O12。用纳米粒度及ZETA电位分析仪、扫描电子显微镜(SEM)、饱和交换容量等表征了材料的粒径及分布、形貌、结构和离子交换性能。结果表明:通过控制反应条件可以在一定范围内制得粒径均一、单分散性好、表面规整光滑的PS微球;PS胶体晶体模板三维有序,排列规整;酸改性后的离子筛前驱体对Li+饱和交换容量为7.49mol/g锂离子筛。     

Pickering乳液聚合制备中空聚苯乙烯复合微球

通过改进Stber法制得纳米SiO2,并经硅烷偶联剂改性使其表面具有较佳两亲性,以该两亲性纳米粉体为油/水界面稳定剂构建O/W型Pickering乳液,引发油相中的苯乙烯单体聚合,在不同苯乙烯与成孔溶剂正辛烷的比例下制得了SiO2/聚苯乙烯复合微球;经傅里叶红外变换光谱(FTIR)、凝胶渗透色谱-多角度激光光散射仪(GPC-MALLS)、热失重分析仪(TGA)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)检测,证实复合微球具有中空的结构特点,并依此讨论了中空微球的形成机理。     

偶氮二异丁基盐酸脒引发甲基丙烯酸甲酯微球的无皂乳液聚合

采用偶氮二异丁基盐酸脒(AMPMDHC)为引发剂,用无皂乳液聚合方法制备单分散性PMMA微球,合成粒径为500nm的单分散PMMA微球的聚合条件是:MMA/H2O=20:100(m1),温度为70℃,AMPMDHC用量为0.06g,反应时间为1.5h.实验结果表明:(1)引发剂用量越多,PMMA微球粒径越小,但对微球粒径分布影响较小;(2)反应温度升高,微球粒径增大,单分散性降低;(3)微球的粒径随着水的用量增大而降低,当MMA/H2O小于1/6时,微球粒径趋于180nm.     

用SPG膜乳化法合成单分散性高分子微粒子

以丙烯酸酯类为聚合性单体(分散相)，以含有表面活性剂的去离子水为连续相(分散介质)，通过SPG膜乳化装置，先制成膜乳化波，经悬浮聚合削成了大粒径的单分散性聚合物微粒子．实验选择了孔径为1．35μm、5．25μm、9．5μm三种规格的SPG膜，制得的球型微粒子的平均粒径分别为11．43μm、28．59μm和45．92μ，单分散性均≤11．93％．对合成过程中影响微粒子性能的主要因素也进行了分析和探讨．     

单分散Eu~(3+)-PS荧光微球的制备及性能

采用分散聚合法研究了单分散纳米聚苯乙烯(PS)微球和宽稀土含量荧光PS微球的合成。在沸水排氧条件下,分别研究了单分散纳米PS微球、稀土配合物(Eu(MAA)3phen)与苯乙烯(St)共聚微球的合成和反应体系稳定性控制,成功制备出了粒径范围在120~260 nm的单分散PS微球及Eu~(3+)-PS共聚物荧光微球,拓宽了分散聚合制备PS微球的粒径范围。采用红外光谱、同步热分析、扫描电镜和透射电镜对产物的结构进行了表征,紫外光谱和荧光光谱对产物的光学性能进行了测试。结果表明产物的单分散性良好,具有Eu~(3+)离子的特征荧光发射。     

溶胶-凝胶模板法制备有序大孔TiO_2微球

以无皂乳液聚合方法自制的单分散聚苯乙烯(PS)微球乳液为原料,利用PS自组装制备了有序胶体晶体模板("蛋白石"),采用溶胶-凝胶模板法制备了有序大孔TiO2微球("反蛋白石"),其孔呈六边形,孔径分布均一,约为200nm。运用扫描电镜(SEM)、X射线衍射(XRD)对其形貌特征及晶型进行了表征,结果表明,采用表面含有羧基的单分散聚苯乙烯微球及高的硅油黏度制得的模板有序度高;通过控制煅烧温度可以改变有序大孔TiO2微球的晶型,当煅烧温度为500℃时,其晶型为锐钛型,当煅烧温度为700℃时,其晶型则为金红石型。     

聚羟基丁酸酯-羟基戊酸酯共聚物/明胶微粒的构造形态与性能

以生物可降解材料聚羟基丁酸酯-羟基戊酸酯共聚物(PHBV)与天然明胶(Gel)为基材,以安定(DZP)原药为模药,分别采用O/W、W/O/ W、O/W/O,单乳化与双乳化溶剂蒸发法技术,制得3种不同结构形态微粒(微球与微囊), 微粒平均粒径为30～40 μm;探讨几种制备参数对微粒内、外部形态结构的影响;用扫描电镜观察了3种类型微粒内部与外部不同结构形态;测试了3种类型微粒释药性能,分析了微粒结构形态对其控释性能的影响.     

二次催化溶胶-凝胶法制备多孔硅胶微球

以四乙氧基硅烷(TEOS)为原料, N,N-二甲基甲酰氨(DMF)为模板, 采用二次催化的溶胶-凝胶法制得微米级多孔性硅胶微球. 考察了一次催化水解缩聚过程中水量、乙醇量, 二次催化反应过程中电解质浓度、搅拌速度对微球粒径的影响, 并采用扫描电子显微镜(SEM)、激光粒度分布仪、比表面及孔径分析仪、显微镜-图像颗粒分析系统进行表征. 结果表明, 制得硅胶微球球形规则且无团聚现象, 平均粒径(D50)为8.9μm, 粒径呈典型高斯分布, 比表面积546.67m²/g, 孔体积0.7142m³/g, 孔径主要分布在2~8nm之间, 分布范围窄; 硅胶微球粒径大小随一次催化过程中水量、乙醇量及二次催化过程中电解质浓度增加而增大, 随乳状液形成过程中搅拌速度加快而减小.     

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.     

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 ...