pH值调节剂对MnZn铁氧体纳米晶形成及磁性能影响

用硝酸盐-柠檬酸溶胶凝胶自燃法获得锰锌铁氧体（MZF）纳米晶。采用TG-DTA,XRD、VSM等方法对不同种类pH调节剂和不同pH值处理的凝胶热分解过程及产物的性能进行了表征结果表明：溶胶pH值和溶胶pH值调节剂对锰锌铁氧体纳米晶的形成有很大的关系。氨水调节凝胶的自燃点温度会随着溶胶的pH值从3．4增加到10而从196℃变到207℃。用乙二胺调节pH值,可以控制锰锌铁氧体纳米晶颗粒在19nm和57nm间变化。乙二胺调节pH值的系统热分解反应速度比氨水调节的系统反应速度慢,其反应生成粉体的饱和磁化强度为60emu／g,而氨水调节的系统生成粉体的饱和磁化强度为70emu／g。乙二胺调节系统生成粉体的矫顽力在pH值大于7后会有所增大。     

Fe74Al4Ga2P12B4Si4块体非晶合金的纳米晶化及软磁性能研究

采用铜模铸造法制备了厚2mm的Fe74Al4Ga2P12B4Si4块体非晶合金.利用X射线衍射(XRD)、差热分析(DSC)和振动样品磁强计(VSM)研究了其晶化行为和软磁性能.结果表明,非晶合金的玻璃转变温度Tg为457.35℃,晶化开始温度Tx为497.65℃.合金的过冷液相区宽度△Tx达到40.30℃,表明合金具有较大的玻璃形成能力.F74Al4Ga2P12B4Si4合金的晶化是二级晶化过程.经520℃等温退火后析出α-Fe相,其晶粒尺寸为15.9nm;而经550℃等温退火后析出α-Fe相及微量的A10.3Si0.7Fe3和Fe3B相,其中α-Fe相的晶粒尺寸为17.4nm.非晶合金的饱和磁化强度为108.816emu/g、矫顽力Hc为574.97Oe;经520℃等温退火后,纳米晶合金的饱和磁化强度为106.875emu/g、矫顽力Hc为94.16Oe.退火实验结果表明,纳米晶化对材料的饱和磁化强度没有显著影响,但会显著降低材料的矫顽力.     

高岭石型硫铁矿烧渣合成磁性4A沸石及其表征

以含有偏高岭石及磁铁矿的高岭石型硫铁矿烧渣为主要原料,采用水热法合成了磁性4A沸石。结合XRD及比表面积分析测试,通过正交实验探讨了晶化温度、晶化时间、碱度、晶种用量对合成磁性4A沸石的影响,确定了合成磁性4A沸石最适宜条件。XRD和FTIR光谱分析表明最佳条件下的合成产物为4A沸石;在扫描电镜观察下,4A沸石多为完整的立方体晶型,磁铁矿微粒主要赋存于4A沸石之间;比表面积为24.49m2/g,铯离子饱和交换吸附量为106.63mg/g;饱和磁化强度Ms为2.94emu/g,剩余磁化强度Mr为0.56emu/g,矫顽力Hci为178.00Oe。     

纳米晶复合SrM永磁铁氧体的制备和交换耦合作用

采用sol-gel方法制备M型六角锶铁氧体。利用X光衍射、透射电子显微镜和VSM对纳米晶样品进行了研究。当热处理温度小于 80 0℃ ,样品存在复相。在同样条件下 ,压成薄片的样品存在硬磁与软磁SrFe12 O19/γ Fe2 O3 的纳米复合相的磁性交换耦合作用。温度为 80 0℃的薄片样品 ,比饱和磁化强度σS 为 75 .6emu/g ,内禀矫顽力Hcj 为6 0 15Oe ,最大磁能积 (BH) Max 为 1.87MGOe ,而粉末样品相应的分别为 75 .9emu/ g ,6 40 0Oe和 1.5 2MGOe。当热处理温度大于 85 0℃时 ,只有单一M相     

核壳型碳铁纳米粉体的制备及磁性能研究

采用直流碳弧法制备碳包铁纳米粒子,用透射电子显微镜(TEM)、X射线衍射仪(XRD)对产物的形貌和尺寸、物相结构组成进行分析,并在真空和氮气气氛下在200～800℃对制备的碳包铁纳米粒子进行热处理,用振动样品磁强计测量处理前后的碳包铁纳米粒子的剩磁强度、矫顽力和饱和磁化强度.结果表明,碳包铁纳米粒子的磁滞回线显示出较好的超顺磁特性;剩磁强度、矫顽力和饱和磁化强度随着粉体中铁含量的增加而增大.对碳包铁纳米粒子进行热处理,其磁性能随温度的升高首先改善,温度进一步升高又逐步劣化.在450℃退火,粉体磁性能最佳.     

尖晶石型MnFe（2-x）GdxO4纳米晶的

以Fe2（SO4）3、MnSO4和Gd2O3,为原料,NaOH溶液为沉淀剂,通过水热法制备了尖晶石型MnFe（2-x）GdO4系列纳米晶,利用XRD、SEM和VSM分别对MnFe（2-x）Gd3O4纳米晶的微结构、形貌和磁性能进行表征,结果表明,所制备的MnFe（2-x）GdxO4均为立方尖晶石结构,晶粒为球形或类球形,粒径约100nm,具有良好的均匀性,掺入Gd3＋后MnFe（2-x）GdxO4纳米晶的饱和磁化强度（crs）总体呈现减小趋势,只有当掺杂量x=0．02时制备的MnFe（2-x）GdxO4纳米晶的比饱和磁化强度（δs）增大,δs为67．2emu／g。     

NiFe2O4纳米粒子的水热合成及表征

以Ni(NO3)2·6H2O和Fe(NO3)3·9H2O为主要原料,在聚乙二醇(PEG)存在下,采用水热法制备了磁性NiFe2O4纳米粒子,用X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁场计(VSM)等分析方法对样品进行了表征.结果表明:水热法合成的NiFe2O4纳米粒子为尖晶石结构,粒度分布均匀,为方形形貌,粒子直径范围在50～60nm;比饱和磁化强度为25.83emu/g,剩磁为6.167emu/g,矫顽力达85.87Oe.     

水热法制备八面体Fe3O4亚微米晶及其影响因素

利用水热法在80～90℃制备了八面体Fe3O4,并对样品进行了X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和磁学性能表征.制备的八面体亚微米晶形貌规整,物相纯净,结晶性好,颗粒尺寸为200～320nm,饱和磁化强度Ms=85.2emu/g,矫顽力Hc=114.20e.探索了NaOH和KNO3溶液的滴加速率、pH值、反应温度和时间及聚乙二醇(PEG)等因素对产物纯度、形貌及颗粒尺寸的影响.     

静电纺丝法制备磁铅石型Ba0.5Sr0.5Fe12O19纳米纤维及其磁性研究

采用静电纺丝结合溶胶-凝胶技术于800℃煅烧制备了铁氧体Ba0.5Sr0.5Fe12O19纳米纤维,利用XRD、SEM、EDS、TEM分别对样品的物相、形貌、结构等进行了表征.结果表明,所得产物为六方磁铅石型Ba0.5Sr0.5Fe12-O19多晶纤维,纤维直径为100～500nm,Scherrer公式计算晶粒尺寸为40nm.采用振动样品磁强计(VSM)表征样品的磁性能,饱和磁化强度、剩余磁化强度和矫顽力分别为66.659emu/g、35.093emu/g和5097.2Oe,与用传统溶胶-凝胶法在相同温度下煅烧制得的粉体样品相比,磁性能明显提高.     

CoFe2O4-SiO2电纺纳米纤维的对喷制备技术与磁性研究

将溶胶-凝胶法和新型双喷丝头静电纺丝技术相结合,制备了CoFe2O4-SiO2电纺纳米纤维材料。利用热分析法(TG-DTA)、X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和振动样品磁强计(VSM)等测试手段,表征了所研制纳米纤维的晶型结构、纤维形貌以及磁学性能。研究结果表明,样品中CoFe2O4为单畴结构,纤维直径在100nm左右,非晶态SiO2的存在有效抑制了CoFe2O4晶粒的生长;煅烧温度对纤维形貌和晶型结构有较大影响,随着煅烧温度的升高,饱和磁化强度(Ms)和剩余磁化强度(Mr)均增大,但矫顽力(Hc)和剩磁比(Mr/Ms)呈波动变化。     

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.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.