Al—Al2O3粉末成形体烧结性的研究

分析研究了金属Ａｌ在１０００℃左右温度下的存在状态以及Ａｌ２Ｏ３上浸润性问题，讨论了Ａｌ－Ａｌ２Ｏ３两相末成形的烧结性能及助烧剂，烧结气氛对材料烧结性能的影响。结果表明，由于金属Ａｌ的活泼性以及生成的Ａｌ２Ｏ３膜的稳定性和金属Ａｌ对Ａ２Ｏ３表面浸润性差等原因决定了Ａｌ－Ａｌ２Ｏ３粉未成形体在１０００℃时的烧结性能极差。     

烧结气氛对Al／Al2O3陶瓷基复合材料组成与性能的影响

介绍了一种新型的Ａｌ／Ａｌ２Ｏ３陶瓷基复合材料，讨论了该材料的烧结机理，研究了烧结气氛对该材料性能的影响。结果表明，助烧的合理选择是实现Ａｌ／Ａｌ２Ｏ３陶瓷基复合材料在１０００℃烧结的关键，助烧剂的粘－塑性流动是材料的主要烧结机理。氢气气氛改变了助烧剂的有效成分，降低了该材料的烧结性能，从而不利于物理性能和力学性能的提高。在Ａｌ／Ａｌ２Ｏ３陶瓷基复合材料的制造过程中，选择空气气氛是合适的。     

Al／Al2O3陶瓷基复合材料的断口分析

应用ＳＥＭ及断口金相技术对Ａｌ／Ａｌ２Ｏ３陶瓷基复合的材料的断口形貌进行研究。结果表明：１０００℃时，助烧剂的粘－塑性流动机制及粘结作用是实现Ａｌ／Ａｌ２Ｏ３瓷基合材料烧结及性能提高的主要原因。Ａｌ／Ａｌ２Ｏ３陶瓷基复合材料呈现韧脆断口形貌特征。     

Al2O3的粉末特征对β-Al2O3烧结性能的影响

研究了Ａｌ２Ｏ３原料在不同热处理条件下的相组成和颗粒形貌以及Ａｌ２Ｏ３粉末特征对Ｎａ－β″－Ａｌ２Ｏ３烧结性能的影响，实验表明，只有α－Ａｌ２Ｏ３才能烧结成致密的β″－Ａｌ２ｏ３陶瓷。     

低温烧结氧化铝基陶瓷材料的研究

介绍了一种经１５００℃烧结研制的Ａｌ２Ｏ３基陶瓷材料。采用ＥＤＳ、ＸＲＤ、ＳＥＭ等手段分析了助烧剂的成分及Ａｌ２Ｏ３基陶瓷的相结构，讨论了Ａｌ２Ｏ３基陶瓷结机理和部分性能。     

TiO2／Al烧结反应生成的Al2O3／TixAly复合材料研究

采用挤压铸造法，先制备ＴｉＯ２／Ａｌ坯块，经随后高温烧结反应，可生成Ａｌ２Ｏ３／ＴｉｘＡｌｙ复合材料。ＤＴＡ分析表明ＴｉＯ２粉末与纯Ａｌ之间的反应具有放热特征。Ｘ射线衍射分析与透射电镜观察发现反应产物主要为α－Ａｌ２Ｏ３与ＴｉｘＡｌｙ。反应过程中ＴｉＯ２粉末首先被熔融态Ａｌ还原成α－Ａｌ２Ｏ３与Ｔｉ，而后Ｔｉ与Ａｌ通过扩散反应形成多种ＴｉｘＡｌｙ金属间化合物。     

共沉淀法制备Al_2O_3-YAG复相陶瓷及其显微结构研究

用共沉淀法制备了Ａｌ２Ｏ３－ＹＡＧ复合粉体,ＹＡＧ的结晶温度在１０００℃左右．共沉淀法 制备的Ａｌ２Ｏ３－ＹＡＧ复合粉体经１５５０℃热压烧结,获得致密烧结体,ＹＡＧ的加入量对烧结温度 的影响不大． Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６０４ＭＰａ,断裂韧性为５．０ＭＰａｍ１／２; Ａｌ２Ｏ３－２５ｖｏｌ％ＹＡＧ复合材料的抗弯强度为６１１ＭＰａ,断裂韧性为４５ＭＰａｍ１／２．所有这些数据 都高于单相Ａｌ２Ｏ３陶瓷的力学性能,说明ＹＡＧ的加入有利于Ａ１２Ｏ３陶瓷力学性能的提高． 通过显微结构观察发现：大的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶界上,小的ＹＡＧ颗粒位于Ａｌ２Ｏ３晶粒 内．在 Ａｌ２Ｏ３－５ｖｏｌ％ＹＡＧ复合材料中,许多小的白色区域存在于 Ａｌ２Ｏ３晶粒内,这可能和较低 的Ｙ２Ｏ３含量有关．     

固相法制备低温烧结B_2O_3-P_2O_5-SiO_2系低介陶瓷材料

采用传统的电子陶瓷生产工艺,制备出一种Ｂ２Ｏ３－Ｐ２Ｏ５－ＳｉＯ２系瓷料．该体系材料加入少量助烧剂可在９００℃,空气气氛中烧结,获得低介电常数陶瓷．得到烧结体的介电常数ε≤５、介电损耗ｔａｎδ≤３×１０－３（１ＭＨｚ）;有望用于超高频叠层片式电感领域．     

Al2O3—TiC—Co新型复合材料的力学性能及断裂行为

对于钴包覆陶瓷粉末热压烧结的Ａｌ２Ｏ３－ＴｉＣ－Ｃｏ新型复合材料力学性能和断裂行为进行了研究。结果表明，Ｃｏ在基体中以金属相存在，分布于晶界的金属钴的存在能有效地改善Ａｌ２Ｏ３－ＴｉＣ材料的力学性能，影响其断裂行为。     

高频多层片式电感器介质材料的研究

研究了低温烧结Ｂ_２Ｏ_３－Ｐ_２Ｏ_５－ＭｇＯ－Ａｌ_２Ｏ_３－ＳｉＯ_２体系的微晶玻璃,及其析晶温度和析晶相特性,实验结果表明：该材料具有低的介电常数和电介质损耗,这种介质能在低于１０００℃的温度下与Ａｕ,Ａｇ／Ｐｂ,Ｃｕ等电极共烧,是一种较理想的高频多层片式电感器介质材料．     

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 ...