Mn-Co-Zn-Cu-O系NTCR微观结构和电学特性

采用Mn2.3 CO3.7 ZnxCuyO4(x=0、0.03、0.06;y=0、0.05、0.08、0.1、0.2)体系制备负温度系数热敏电阻(NTCR),并通过EDS、SEM、FTIR研究了样品的微观结构和导电机理.结果表明,Mn-Co-O体系通过掺杂ZnO、CuO可以制备低阻高B型NTCR,当x=0.03,y:0...     

Co掺杂ZnO块材的晶体结构和磁性能研究

采用固相法制备了Zn1-xCoxO（x=0．05-0．25）块材,烧结温度和Co含量对Zn1-xCoxO（x=0．05-0．25）块材的晶体结构和室温磁性能影响强烈,当x≤0．1,烧结温度从800增加到1100℃时,Zn1-xCoxO（x=0．05-0．25）呈现出单相结构,但当x〉0．1,烧结温度为800℃时,样品中出现CoO相;随着烧结温度提高到900℃,样品再次获得纯的单相结构。为了获得高的饱和磁化强度Ms,最佳烧结温度应该根据Co含量进行调整。在最佳烧结温度条件下,当x从0．05提高到0．1时,Ms从0．79增加到了1．06μB/Co,但当x继续提高到0．2和0．25时,Ms分别降低到了0．59和0．41μB/Co。     

掺RuO2对Mn1.4Co1.5Zn0.1陶瓷电性能的影响

以Mn1.4Co1.5Zn0.1为原料,RuO2为掺杂剂,采用固相反应法制备了xwt％RuO2(x=0,3,6,9,12,15)+Mn1.4Co1.5Zn0.1单层片式NTC热敏电阻材料,研究了该材料的微观结构和电性能.结果表明:通过RuO2掺杂可以制备低阻高B型NTC热敏电阻材料,随着RuO2含量的增加,样品B值和电阻率迅速减小,随着烧结温度升高,电阻率先降低后升高,B值缓慢增加.当烧结温度为1130℃、RuO2掺杂量为15wt％时,样品具有较好的NTC特性:B值为3012 K,ρ25为32Ω·cm.     

精矿粉和Mn3O4制备MnZn功率铁氧体工艺研究

为了降低功率铁氧体的制备成本,采用传统氧化物陶瓷工艺,用精铁矿粉代替Fe2O3、用Mn3O4代替MnCO3制备出高性能功率软磁MnZn铁氧体.研究了精铁矿粉和Mn3O4制备MnZn铁氧体的固相反应及预烧温度、烧结温度和掺杂对样品磁性能的影响.实验结果表明:精矿粉经氧化生成的α-Fe2O3立即与Mn3O4反应生成MnZn铁氧体,使固相反应更完全;预烧温度为1100℃,烧结温度为1240～1280 ℃时样品性能最佳;适当的掺杂可降低样品的功耗.样品最佳性能如下:μi=2268;Bs=508 mT;Tc=227℃;Po=34.5 W/kg,综合性能达到日本TDK PC30材料性能水平.     

Mn_3O_4对LiZn铁氧体磁性能、微结构和电阻率的影响

按组成Li0.35Zn0.30Fe2.29MnxO4-δ+0.005mol%Bi2O3和Li0.35Zn0.30Fe2.29O4-δ+0.005mol%Bi2O3+x/3mol%Mn3O4(x=0.02～0.08)在920和950℃制备缺铁LiZn铁氧体,分别在原料和预烧料中添加Mn3O4.结果表明:920℃烧结时,在原料中添加适量Mn3O4可提高样品饱和磁化强度Ms和剩磁Br,降低矫顽力Hc,而在预烧料中添加Mn3O4对Ms和Br影响不大,不完全固相反应导致两种样品Hc很高,但在原料中添加Mn3O4的样品Hc相对较低.950℃烧结时,两组样品Hc均大幅下降,但在原料中添加Mn3O4的样品Hc反而相对较高.两种方式添加Mn3O4均可提高电阻率ρ,x=0.06时ρ出现峰值,且在原料中添加Mn3O4的样品ρ较高.     

精矿粉和Mn3O4制备MnZR功率铁氧体工艺研究

为了降低功率铁氧体的制备成本，采用传统氧化物陶瓷工艺，用精铁矿粉代替Fe2O3、用Mn3O4代替MnCO3制备出高性能功率软磁MnZn铁氧体．研究了精铁矿粉和Mn，04制备MnZn铁氧体的固相反应及预烧温度、烧结温度和掺杂对样品磁性能的影响．实验结果表明：精矿粉经氧化生成的α—Fe2O3立即与Mn3O4反应生成MnZn铁氧体，使固相反应更完全；预烧温度为1100℃，烧结温度为1240～1280℃时样品性能最佳；适当的掺杂可降低样品的功耗．样品最佳性能如下：μi=2268；Bs=508mT；Te=227℃；P0：34．5W／kg，综合性能达到日本TDKPC30材料性能水平．     

掺杂Co3O4对Ce0.8Gd0.2O2-δ固体电解质性能的影响

采用低温燃烧法制备了Ce0.8Gd0.2O2-δ（CGO）及掺杂2.0mol%CoO1.333的CGO（2Co-CGO）,研究了掺杂Co3O4对CGO密度和电导率的影响.实验发现,由于烧结过程中粘性流动烧结的发生,掺杂Co3O4后可在一定的温度范围内使样品致密度提高;经SEM分析,1100℃烧结5h的2Co～CGO晶粒生长完整;与CGO相比较,2Co～CGO在700℃所测电导率略有降低.     

锌掺杂钴铁氧体:硬磁→软磁

采用共沉淀法制备了不同Zn2+掺杂量的Co1-xZnxFe2O4,研究了Zn2+掺杂量对其结构和磁性的影响。X射线衍射测试表明Co1-xZnxFe2O4成相良好,结晶随烧结温度增加而愈加完善。经400℃热处理2h的Co0.7Zn0.3Fe2O4晶粒尺寸由谢乐公式计算为8.57nm。利用振动样品磁强计研究其静态磁性,结果表明,Zn2+掺杂量对Co1-xZnxFe2O4磁性有显著影响,Zn2+含量越高矫顽力越低,同时饱和磁化强度越大,当x=0.3时,矫顽力仅为1352.82A/m,磁化强度为42A.m2/kg,实现了CoFe2O4从硬磁性到软磁性的转变,可作为潜在的高频软磁材料。     

Mn-Co-Ni-Pb-O系NTC热敏电阻制备及电性能的研究

采用XRD、SEM和电性能测试等手段,研究了Mn1.05-xCo0.92Ni0.03PbxO4系列NTC热敏陶瓷的烧结特性和电性能参数与Pb掺入量的关系。结果表明掺Pb可以降低Mn-Co-Ni-O系NTC热敏电阻的烧结温度和室温电阻率。当Pb掺杂量x=0.12时样品的收缩率最大,样品的老化稳定性最好,该陶瓷样品的最佳烧结温度降至900~950℃之间,烧结温度为950℃时样品的ρ25和B值分别为490Ω.cm和3969K,具有较低的ρ25和较高的B值。     

电解锰渣复合Fe-Mn-Cu-Co系红外辐射材料的制备及性能研究

以Fe2O3、Mn O2、Cu O、Co2O3系过渡金属氧化物为基料,分别添加不同比例的电解锰渣配料混匀后,经高温烧结制备复合红外辐射材料。通过XRD、SEM对制备的电解锰渣复合红外辐射材料的物相结构和微观形貌进行表征,探讨了电解锰渣添加比例、烧结温度和保温时间对复合红外辐射材料的常温全波段法向红外发射率的影响。研究结果表明,电解锰渣添加量为10%的样品,经1 150,1 210和1 270℃保温2 h获得的发射率分别为0.874,0.904和0.911;其最佳的制备条件为1 270℃烧结,保温时间3 h,获得的发射率为0.924;随着电解锰渣添加量的增加,样品发射率呈下降趋势,但电解锰渣添加量为30%时,其发射率仍有0.89。尖晶石结构Co Mn2O4、Mn Fe2O4和反尖晶石结构Mn(Cu Mn)O4的生成,良好的结晶形态是复合材料获得高发射率的关键。     

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 ...