不锈钢纤维吸波性能研究

以集束拉拔制备的302,304和316L 3个牌号、不同丝径奥氏体不锈钢纤维为对象,采用Agilent8722ES矢量网络分析仪,测量了它们的复数电导率和复数磁导率的微波频响特性曲线.实验结果表明,不锈钢纤维的微波磁导率(μ′,μ″)随纤维直径的减小而增大.2 μm的304不锈钢纤维的复数磁导率μ″在2 GHz处达到2.2.302不锈钢纤维吸波性能明显优于等径的316L和304不锈钢纤维.302不锈钢纤维在2～18 GHz频率范围内符合吸收剂频谱响应特性要求.     

新型金属纤维滤材的除湿性能

以不同丝径的不锈钢纤维为金属纤维过滤器的滤材,通过实验分析滤层厚度对纤维过滤器的除湿性能的影响。结果表明,增加滤层厚度可以有效提高除湿效率,但当8μm纤维滤层超过6层后,滤层除湿效率变化不大;实验结果与经典过滤机理模型计算值的相对误差小于9%,经典过滤机理模型可用来预测新型不锈钢纤维过滤器的除湿效率。     

孔隙度对烧结不锈钢纤维多孔材料剪切性能的影响

将丝径为100μm的不锈钢纤维松装于烧舟中,经1150℃/2h真空烧结和后续加工制备了具有孔隙度范围在70%～95%之间的金属纤维多孔板材.在MTS858材料试验机上检测了多孔板材的准静态剪切性能,重点研究了孔隙度对剪切性能的影响.结果表明,面内剪切应力-应变曲线大致分为3个阶段:应变很低情况下的线性弹性阶段、塑性变形区和应力破坏阶段;随着孔隙度的增加,不锈钢纤维多孔材料的剪切模量、屈服强度减小.     

含金属纤维纱线热导率和电导率研究

通过制备金属纤维纱线与环氧树脂两相复合结构的金属纤维纱线,对金属纤维纱线进行比热容、纤维轴向和径向热导率、电导率测试。结果表明:金属纤维的加入,会提高纱线的热导率及电导率,在金属纤维含量相同的情况下,纺纱方式对金属纤维纱线的热导率及电导率的影响不大。当不锈钢纤维含量为30%时,样品Y8混纺纱的电导率达到3.91×103S/m,轴向、径向等效热导率分别为1.5929、0.4847W/m·℃。     

激光蒸发法制备亚微米磁性纤维的研究EI北大核心

使用CO2激光器,采用蒸发法在惰性气体引导和磁场的诱导下,通过调整各工艺参数,制备出直径为200~500nm的亚微米磁性铁纤维。并通过扫描电镜观察了纤维的形貌和尺寸。实验证明此方法具有纤维的纯度高、粒径分布窄,粒子直径能够有效控制的特点。     

不锈钢纤维多孔材料的能量吸收性能

以不锈钢纤维毡为原料,通过配料及高温烧结得到不锈钢纤维多孔材料。对不同孔结构的不锈钢纤维多孔材料进行压缩性能测试,经计算得到能量吸收值。结果表明,随着烧结结点数量的增加,不锈钢纤维多孔材料的能量吸收能力有所提高;在丝径为8～28μm之间,改变材料的丝径,对改变纤维多孔材料的能量吸收能力影响不大;随着孔隙度的降低,纤维多孔材料的能量吸收性能有明显提高。     

具有微米级内外径CTA中空纤维膜制备与表征

利用干湿法通过改变纺膜条件来调控中空纤维膜尺寸制备具有微米级内外径的三醋酸纤维素(CTA)中空纤维膜.结果表明,中空纤维膜的内外径随铸膜液流量和芯液流量的增加而增加,随收丝速度的增加而减小;内外径随空气段高度的增大而略微减小;其中铸膜液和芯液流量对膜尺寸的影响最为显著.此外,考察了这些因素对膜微观结构及纯水通量性能的影响,结果表明,本研究中这些因素对膜结构的影响较小,所有膜都具有海绵状孔;纯水通量随着铸膜液和芯液流量的增加而显著增加,随空气段高度和收丝速度的增加而稍有增加.     

铁镀层在集束拉拔法生产金属纤维中的应用

为了减少酸洗过程对环境的污染,并很好地解决铁铬铝及镍基合金纤维制备过程中基体与隔离层高温下相互扩散的问题,采用电镀法在316L不锈钢丝表面沉积镀铁层,经过穿管、拉拔、退火、电解等工序,制备出12μm不锈钢纤维,并与铜镀层制备的同规格纤维进行了对比。结果表明:该纤维化学成分符合GB/T 20878-2007规定,未引入杂质元素;纤维表面质量较差,存在明显的析出物及沟槽;纤维断裂强力与延伸率较小,需要通过对电镀丝进行退火处理及改用带水冷装置的线材连续退火炉进行退火等措施加以改进。     

冷连轧对TC16钛合金丝材组织性能的影响

冷轧加工不仅可以实现小规格丝材尺寸的高精度控制,也可以满足对组织和性能有特殊要求的丝材加工。通过对比分析冷连轧和热拉拔两种加工方式制备出的TC16钛合金丝材的性能和组织,研究了冷连轧工艺对TC16钛合金丝材退火态和固溶时效态性能的影响。结果表明,冷连轧获得的TC16钛合金丝材经退火后的抗拉强度比热拉拔加工丝材低,但是塑性较高,更有利于后续TC16钛合金紧固件的冷镦制成形;经过热处理强化后,冷连轧获得的TC16钛合金丝材强化效果明显,抗拉强度提高和塑性降低程度更为显著。相比热拉拔加工,冷连轧可有效破碎纵向长条α相并储存更多的加工畸变能,是获得优良退火态塑性和增强热处理强化作用的主要原因。     

热处理温度对M-Ba铁氧体微米纤维结构和磁性能的影响

以柠檬酸和金属盐为原料,采用有机凝胶先驱体转化法成功制备了直径为500～600nm的钡铁氧体(BaFe12O19)微米纤维。通过XRD、SEM和VSM等技术对所制备的目标纤维进行了表征。结果表明,经750℃焙烧2h后,可获得M-Ba铁氧体纯相。随着焙烧温度的升高,晶粒逐渐长大,经850℃焙烧2h后,纤维主要由比较规则的片状晶粒组成。钡铁氧体纤维的磁性能主要受晶粒尺寸和测试温度的影响。经950℃焙烧2h后,组成纤维的晶粒尺寸约为62nm,室温下测得的饱和磁化强度和矫顽力均取得最大值,分别约为67A.m2/kg和328kA/m。在液氮(77K)条件下,纤维的饱和磁化强度有显著提高,最大值约为87A.m2/kg,这主要是由于纳米晶的表面自旋有序程度提高造成的。     

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.     

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...     

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.     

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.     

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.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.