无团聚ZrO2-HfO2-Y2O3复合纳米粉体的制备

以分析纯ZrOCl2·8H2O、HfOCl2·8H2O和Y(NO3)3·6H2O为原料,采用反向滴定共沉淀-共沸蒸馏法成功地制备出无团聚的ZrO2-HfO2-Y2O3复合纳米粉体.借助XRD、TEM、BET等手段分析了制备工艺对粉体粒径和团聚状态的影响.研究表明,分散剂PEG的加入量及前驱体湿凝胶的处理方式对最终制备的ZrO2-HfO2-Y2O3复合粉体的晶粒度影响不大,但显著影响粉体的分散状态.分散剂加入量为1%(质量分数)并对湿凝胶共沸蒸馏处理条件下最终获得的粉体的分散性最好.前驱体沉淀经500℃焙烧1h后,生成了具有高氧离子电导率的立方晶型ZrO2基ZrO2-HfO2-Y2O3固溶体,粉体的平均粒径约为15nm.     

前驱物对水热合成钛酸铋纳米粉体的影响

研究了前驱物的浓度、预处理方式和配比对水热法制备钛酸铋粉体结构和形貌的影响。以Bi(NO3)3.5H2O和TiCl4为原料,KOH为矿化剂,在240~260℃水热反应4h,制备出Bi4Ti3O12纳米粉体,借助XRD、TEM、SEM和FTIR分别对粉体的晶相、微观形貌和组成进行表征。结果表明,当前驱物浓度为0.10~0.15mol/L,Ti/Bi摩尔比值为0.75时,可获得单一物相组成的Bi4Ti3O12粉体;用去离子水反复洗涤胶体沉淀前驱物,可防止Cl-1带来的不利影响;实验所得Bi4Ti3O12晶粒是方形片状的,宽度尺寸在30nm左右,长度大于100nm。     

掺杂TiO2粉体共沉淀包膜过程中的热力学研究

为了精确控制共沉淀包膜法制备掺杂TiO2粉体的反应条件,本文通过对Men+(Ni2+、La3+、Fe3+、Al3+)在NaHCO3-NH3.H2O体系中离子沉淀反应平衡的热力学分析,得到了Men+-CO32--NH3.H2O体系中不同总氨浓度cN和总碳浓度cC时各金属离子总浓度与pH值的关系图,并由此确定了金属离子完全沉淀的最佳pH值.热力学分析表明,以NaHCO3-NH3.H2O作为沉淀剂,采用共沉淀包膜法制备掺杂TiO2粉体时,当cN=0.010 mol/L和cC=1.000 mol/L时,反应的适宜沉淀pH为9.0左右.     

掺杂型SnO2薄膜对乙醇的气敏特性

以SnCl4·5H2O、Ce(NO3)3·6H2O、CuCl2·2H2O、La(NO3)3·6H2O为原料,柠檬酸为络合剂,采用sol-gel法,浸渍提拉技术制备了纯SnO2及其掺杂薄膜.利用XRD分析方法进行了物相结构分析,研究了掺杂比对各掺杂SnO2薄膜元件气敏特性的影响.发现掺杂比相同时,掺杂Ce3+的SnO2样...     

水热法合成Bi25FeO40纳米粉体的研究

本文以Fe(NO3)39H2O和Bi(NO3)35H2O为起始物料,NaOH为沉淀剂和矿化剂,利用水热合成技术制备了Bi25FeO40纳米粉体.利用XRD、SEM和TEM等分析测试手段对所制得Bi25FeO40粉体的物相组成和晶粒形貌等性质进行了研究,并详细讨论了水热反应温度、反应时间和矿化剂浓度等对晶体生长和粉体制备的影响.结果表明,采用这种低温水热技术制备出的产品为纯的Bi25FeO40陶瓷粉体,在微观结构上呈现出三角锥和立方体结构,最佳工艺条件为[Fe]=[Bi]=0.2mol/L,矿化剂[NaOH]=0.5mol/L,在180℃水热反应24h.     

化学沉淀法制备纳米氧化铝过程中的防团聚研究

分别以无水乙醇、去离子水为溶剂,以NH3·H2O、NH4HCO3为沉淀剂,采用化学沉淀法制备了纳米Al2O3粉体.利用TEM、XRD、FT-IR和激光粒度仪研究了溶剂、沉淀剂、浓度、前驱体等因素对纳米Al2O3粉体制备过程中的团聚程度的影响.结果表明:当NH4HCO3和Al(NO3)3水溶液浓度分别为3.0mol/L和0.3mol/L时,借助超声分散和微波干燥,得到的纳米Al2O3粉体粒度均匀、分散良好,1100℃煅烧所得粉体平均粒径为20nm.     

Ca2Co2O5化合物的制备及热电性能的研究

以Co(NO3)2·6H2O,Ca(NO3)2·4H2O为原料,Na2CO3为沉淀剂,采用化学共沉淀法和放电等离子烧结(SPS)制备了Ca2Co2O5化合物.采用TG-DTA、XRD和SEM等手段对前驱体的热分解过程,样品的物相以及形貌进行了表征,测试了Ca2Co2O5的热电性能.实验结果表明沉淀前驱物经850℃预烧8 h后,利用SPS 850℃,压力30MPa保温5min,制备了纯相Ca2Co2O5化合物.该化合物的电阻率和热导率均随温度的升高而降低,800℃时,热电性能优值(ZT)为0.12.     

陈化时间对Nd:YAG纳米粉体制备及性能的影响

以NH4Al(SO4)2·12H2O,Y(NO3)3·5H2O,Nd(NO3)3·5H2O为原料,碳酸氢铵为沉淀剂,研究了共沉淀法制备Nd:YAG纳米粉体过程中陈化时间对粉体性能的影响.采用pH计,FT-IR,XRD和TEM测试手段对其进行表征.陈化过程中PH值先减小后增大,XRD曲线显示共沉淀法中不同陈化时间都能得到纯相粉体,而24h所得粉体最好,粉体TEM图谱表明陈化24h所得到的粉体粒径更小,分散性较其他粉体更好.结果表明:共沉淀法制备Nd:YAG纳米粉体过程中陈化时间不影响纯相粉体的制得,但对粉体粒径大小及分布和团聚程度有直接的影响.陈化24h的粉体颗粒最小并且均匀,团聚很少.     

氧化钆掺杂纳米氧化铈薄膜的制备与烧结性能研究

以Ce(NO3)3·6H2O和Gd2O3为前驱体,六亚甲基四胺为沉淀剂,通过均相沉淀反应直接合成能长时间稳定悬浮的氧化钆掺杂纳米氧化铈(Ce0.8Gd0.2O1.9,GDC)母液.对合成的前驱粉体进行了XRD、BET、动态光散射等研究,XRD结果表明粉体具有氧化铈的立方萤石结构特征峰,BET结果表明粉体比表面积为68.3m2/g,当量粒径为约12nm,非等温烧结实验结果表明粉体具有良好的烧结活性.用浸渍-提拉法(dip-coating)在多孔NiO-YSZ阳极基底上制备GDC电解质薄膜,并利用场发射扫描电镜对薄膜的烧结行为进行了研究,薄膜在1300℃等温烧结后实现完全致密化.通过薄膜制备过程中制浆与成膜两个步骤的有机结合,探讨一条制备高性能GDC电解质薄膜的新途径.     

前驱溶液的碱浓度对BiVO4粉体的微波水热法制备及光催化性能的影响

以Bi(NO3)3·5H2O和NH4VO3为原料,采用微波水热法在200℃不同前驱液碱浓度下制备了BiVO4粉体。利用XRD、FE-SEM、BET、UV-Vis等手段研究了前驱液碱浓度对BiVO4晶型、结构及形貌的影响,并对不同前驱液碱浓度下合成粉体的光催化性能进行了研究。溶于纯水获得的粉体是单斜相和四方相1～3μm八面体结构的BiVO4混晶。溶于HNO3和NaOH溶液时制得粉体为纯单斜相3μm大小球状BiVO4,NaOH增加到4mol/L时为2μm大小鱼排骨状BiVO4的混晶。光催化结果表明,紫外光下光催化活性顺序为:BiVO4(纯水)>BiVO4(4mol/L NaOH)>BiVO4(2mol/L NaOH),可见光下光催化活性顺序为:BiVO4(4mol/L NaOH)>BiVO4(纯水)>BiVO4(2mol/L NaOH)。     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.