自蔓延高温合成钡铁氧体的研究

介绍了自蔓延高温合成技术合成BaFe12O19的过程,研究了热处理对产品性能的影响.用VSM对产物的磁性能进行了测量,用XRD对产物的物相进行了分析,用SEM对产物形貌和组织进行了观察.结果表明,采用自蔓延(SHS)高温合成的BaFe12O19具有良好的磁性能.     

磁场诱导自蔓延高温合成钡铁氧体

本文采用外加磁场诱导自蔓延高温合成钡铁氧体,试验用的电磁场强度最高可达1.3T,对无磁场和不同磁场强度下合成的铁氧体的形貌、相组成和磁性能分别进行了表征.研究结果表明:外加磁场对燃烧温度有影响,燃烧温度影响产物转换,燃烧温度较低时,产物为BaFe2O4与BaFe12O19相共存;本试验条件下,磁场强度为0.86T时,合成为M型的钡铁氧体(BaFe12O19),产物结晶完整,有六角片状的钡铁氧体,且性能达到了最佳,矫顽力达到1083(4π)-1·kA·m-1,比剩余磁化强度为16.16 A·m2/kg,比不加磁场条件下分别提高50%和提高32%,说明适当的磁场强度诱导自蔓延高温合成可以改善BaFe12O19的磁性能.     

二次铁电池正极材料铁酸钡的制备及性能初步研究

用高温固相法制备了BaFe2O4。采用扫描电子显微镜(SEM)及X射线衍射仪(XRD)对产物的表面形态和结构进行了表征;以循环伏安、模拟电池恒电流充放电实验研究了BaFe2O4电极的电化学性能。结果表明,以BaFe2O4为正极充电起始物质,与贮氢合金电极组成二次碱性电池,在1.2V附近有一个平稳的放电平台,具有较好的电化学活性。合成时反应物的比例对产物的结构和电化学性能有明显的影响,在900℃,灼烧10h的条件下,以反应物Fe2O3与Ba(OH)2摩尔比为1:1.5时获得的产物性能较好。     

凝胶法制备Ba铁氧体的微观形态及磁性能

用溶胶-凝胶技术制备六角晶系BaFe12O19铁氧体超微粉末,采用热分析技术和XRD技术分析了其形成规律,运用扫描探针显微镜分析其微观形态,并测定了常温磁性能。结果表明：BaFe2O4和BaFe12O19的转变温度分别为414．55℃、755．78℃;800℃处理后得到的BaFe12O19超微粉末呈三种不同的形态,分别为圆形、带孔洞的圆形和圆环形;平均粒径为450nm左右;其厚度小于其直径;1000℃处理后的样品完全是BaFe12O19结构,其ds小于粗晶BaFe12O19铁氧体,而Hc大于粗晶肪BaFe12O19铁氧体。     

BaFe12O19／Al2O3—SiO2—K2O微晶玻璃陶瓷的柠檬酸Sol—Gel合成及其微波性能的研究

采用柠檬酸sol-gel工艺合成了BaFe12O19/Al2O3-SiO2-K2O微晶玻璃陶瓷，并对其介电常数及其磁导率在1MHz～6GHz下的变化规律进行了研究。结果表明，BaFe12O19/Al2O3-SiO2-K2O微晶玻璃陶瓷的合成与体系中Fe/Ba、烧结温度密切相关；其介电常数、磁导率基本都随测试频率的增加而下降；介电损耗值最大可达到0.30，磁损耗值较小。     

BaFe12O19/A12O3-SiO2-K2O微晶玻璃陶瓷的柠檬酸SOl-Gel合成及其微波性能的研究

采用柠檬酸sol-gel工艺合成了BaFe12O19/A12O3-SiO2-K2O微晶玻璃陶瓷,并对其介电常数及其磁导率在1MH2～6GHz下的变化规律进行了研究.结果表明,BaFe12O19/Al2O3-SiO2-K2O微晶玻璃陶瓷的合成与体系中Fe/Ba、烧结温度密切相关;其介电常数、磁导率基本都随测试频率的增加而下降;介电损耗值最大可达到0.30磁损耗值较小.     

M型钡铁氧体制备的工艺优选

M型钡铁氧体(BaFe12O19)具有原料便宜、化学稳定性优异、矫顽力和磁能积较高、单轴磁晶各向异性以及化学稳定性优异等优点,因而被广泛用作微波毫米波段材料、微波吸收材料和高密度垂直磁记录介质等.研究了溶胶-凝胶法和自蔓延法相结合制备M型钡铁氧体(BaFe12O19)粉末过程中,起始溶液的组成、前驱体溶液pH值、烧结温度和表面活性剂等因素对产物性能的影响.用X射线衍射仪(XRD)、扫描电镜(sEM)和振动样品磁强计(VSM)对粉末的结构、形貌以及磁性能进行了表征.结果表明:前躯体溶液pH值为7.0,柠檬酸与金属离子摩尔比为2:1,自蔓延燃烧后的粉体在烧结温度1 180℃煅烧,能够形成单一、均匀的M型钡铁氧体.所制备的M型钡铁氧体的最佳磁性:饱和磁化强度(Ms)64.53 emu/g,剩余磁化强度(Mr)28.21 emu/g,矫顽力(Hc)2.696 kOe.     

BaFe12O19/SiO2微晶玻璃陶瓷的柠檬酸盐Sol-Gel合成及其微波性能的研究

采用柠檬酸sol-gel工艺合成了BaFe12O19/SiO2微晶玻璃陶瓷,并对其介电常数及其磁导率在100MHz-6GHz下的变化规律进行了研究。结果表明,BaFe12O19/SiO2微晶玻璃陶瓷的合成与体系中Fe/Ba,烧结温度密切相关;其介电常数、磁导率基本都随测试频率的增加而下降,介电损耗值最大达到0．40,磁损耗值较小。     

化学计量比和热处理条件对钡铁氧体磁性能的影响

讨论了溶胶-凝胶法制备钡铁氧体材料的过程中,主要工艺参数,即烧结温度、烧结时间、Fe/Ba比率对产物组成及磁性能的影响.研究结果表明,增加烧结时间和烧结温度有利于提高产物的饱和磁化强度(Ms),但对矫顽力(Hci)的影响甚微;Fe/Ba比率的变化主要影响产物组成中主相BaFe12O19和杂质相BaFe2O4的比率,进而影响产物的磁性能.     

M型铁氧体BaNix/2Cox/2ZrxFe12-2xO19纳米粉体的高频电磁特性

采用自蔓延法制备了Ni-Co-Zr离子共掺BaFe12O19的前驱体,并研究了不同掺杂量对样品微结构和磁性能的影响。通过XRD、SEM、VSM和VNA等 对 样 品 进 行 性 能 表 征,发 现BaFe10Ni0.5Co0.5-Zr1.0O19在1100℃保温4h,矫顽力 Hc仅7.4×103A/m,饱 和 磁 化 强 度 Ms为28.6A·m2/kg;BaFe10.4-Ni0.4Co0.4Zr0.8O19在1100℃保温4h后,矫顽力 Hc为4.62×104A/m,饱和磁化强度 Ms却有50.2A·m2/kg。离子掺杂对M型钡铁氧体的复介电常数有一定影响;随着掺杂增加复磁导率μ′先增加后降低,减小了材料的应用频率范围。同时Ni-Co-Zr离子掺杂使得产物颗粒粉体晶粒细化,活性增加。     

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.     

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...     

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.     

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.     

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