Aqueous Tape Casting Process with Styrene-acrylic Latex Binder

A commercial styrene-acrylic latex binder has been investigated as a good binder for aqueous Al2O3 suspensions tape-casting process. This paper focuses on the forming film mechanism of latex binder, the rheological behaviors of the suspensions, physical properties of green tapes and drying process of aqueous slurries with latex binder system. The drying process of the alumina suspensions is shown to follow a two-stage mechanism ( the first stage : evaporation controlled process ; and the second stage : diffusion controlled process ). During the drying stage of the suspensions, the compressive force presses the latex particles arid makes them be distorted, which results in cross-linking structure in co.acted latex particles of the solidified tapes. A smooth-surface and high-strength green tape was fabricated by aqueous tape casting with latex binder system. The results from the SEM images of the crossing section microstrueture of green tapes show that the latex is a very suitable binder for aqueous tape casting.     

流延成型法制备三氧化二铝陶瓷膜基体 (Ⅰ)浆体的制备和流延成型

采用水基浆体流延成型法制备陶瓷膜基体。讨论了分散剂、乳胶液粘结剂、塑化剂对三氧化二铝浆体流动性、韧性和机械强度的影响。实验结果表明 :不加乳液粘结剂 ,分散剂质量分数 0 1 %时 ,浆体的流动性较好 ;采用醋丙和苯丙乳液作粘结剂 ,分散剂质量分数 0 3 %时 ,浆体的流动性好 ,粘度较低 ,适合流延成型 ;用醋叔乳液作粘结剂 ,分散剂质量分数 0 7%时 ,浆体的流动性最好 ,但浆体粘度较高 ;用苯丙乳液粘结剂和邻苯二甲酸二丁酯塑化剂并用 (塑化剂质量分数 1 % ) ,得到的生坯具有较好的塑性、韧性和机械强度。     

流延工艺对生瓷带结构和微波特性的影响

基于低温共烧陶瓷技术流延工艺的特点,通过研究粘合剂、分散剂和增塑剂等在浆料体系中的力学效应对生瓷带中陶瓷成分颗粒的几何排列及所产生的孔隙排斥等力学特性的影响,以及优化热处理温度对生瓷带的质量损失、延展率和拉伸强度的关系,深入分析了流延过程的关键技术及工艺参数对生瓷带结构和微波特性的影响。研究后提出:通过调整流延浆化浆料中粘合剂、分散剂和增塑剂配比,采用梯度缓变的热处理烘干温度曲线和消除生瓷带累积应力等方法,可明显改善流延工艺过程,最终获得质量稳定、可靠性高和功能满足于微波应用要求的生瓷带。     

流延成型法制备三氧化二铝陶瓷膜基体(Ⅱ)——陶瓷膜基体的性能及结构表征

以苯丙乳胶液为粘接剂,水为分散介质,采用流延成型法制备了氧化铝陶瓷膜生坯体。通过对生坯体烧结后气孔率及断裂强度的测定,讨论了烧结温度及粘接剂含量对气孔率和断裂强度的影响。结果表明,随烧结温度的升高,基体的断裂强度增加,而气孔率有降低的趋势。在同一烧结温度下,随着粘结剂含量的增加,基体的气孔率增加,在添加了增稠剂羟乙基纤维素(HEC)后,气孔率进一步增加,但增加量不大,并且导致浆体粘度增加,不易流延成型。通过对不同烧结温度的基体的扫描电镜观察发现,氧化铝粒子分布比较均匀,随着温度的升高,晶粒明显长大,致密性提高,气孔率下降。     

含有定向排列颗粒的氮化硅陶瓷各向异性研究

通过添加α—Si3N4晶须,利用流延成型和热压烧结技术制备舍有定向排列颗粒、各向异性的Si3N4陶瓷。研究α-Si3N4相在流延膜及烧结块体中的分布状态,并通过XRD、SEM和力学性能对流延膜和烧结块体的各向异性进行表征。结果表明,1550℃下烧结制备的块体T（与流延方向平行的平面）、N（与流延方向垂直的平面）、P（侧面）三个面的I（210）／I（102）值与等轴状α-Si3N4粉体的相应值比较,其中T面的值较大,N面和P面的值较小;在T面的显微结构中存在平行于流延方向排列的大颗粒;试样不同面的力学性能（断裂韧性和抗弯强度）中,T面最好,P面次之,N面最差;I（210）／I（102）值、显微结构、力学性能测试结果表明所制备的氮化硅陶瓷存在各向异性。     

Phase composition, transition and structure stability of functionally graded cemented carbide with dual phase structure

The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co3W3C （M6C type）. The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M6C→M12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.     

Influence of colloidal nanosilica on hydration kinetics and properties of CaO/CaSO4-activated slag binderOA

To solve the energy consumption and CO₂ emission during cement production, the new binders must be developed as an alternative to cement. CaO/CaSO₄-activated slag binder is an eco-friendly and safe cementitious material; however, its low strength during initial stages limits its applications. In this study,colloidal nanosilica(CNS) was employed as an additive to improve the strength of CaO/CaSO₄-activated slag binder, and the effects of CNS on the workability, hy...     

Effects of water phase concentration on the emulsion polymerization of polyaniline

Ｄｕｒｉｎｇｒｅｃｅｎｔｙｅａｒｓｐｏｌｙａｎｉｌｉｎｅ(ＰＡＮ)ｈａｓｂｅｃｏｍｅｏｎｅｏｆｔｈｅｍｏｓｔｐｒｏｍｉｓｉｎｇｃｏｎｄｕｃｔｉｖｅｐｏｌｙ ｍｅｒｓｆｏｒｐｒａｃｔｉｃａｌａｐｐｌｉｃａｔｉｏｎｄｕｅｔｏｉｔｓｈｉｇｈｅｎｖｉ ｒｏｎｍｅｎｔａｌｓｔａｂｉｌｉｔｙａｎｄｈｉｇｈｃｏｎｄｕｃｔｉｖｉｔｙ[1 3] .ＰＡＮｃａｎｂｅｓｙｎｔｈｅｓｉｚｅｄｂｙｃｈｅｍｉｃａｌｏｘｉｄａｔｉｏｎａｎｄｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｐｏｌｙｍｅｒｉｚａｔｉｏｎ[4 6 ] .Ｈｏｗｅｖｅｒ,ｔｈｅｃｏｎｊｕ…     

Influences of polypropylene fiber and SBR polymer latex on abrasion resistance of cement mortar

Influences of polypropylene (PP) fiber and styrene-butadiene rubber (SBR) polymer latex on the strength performance, abrasion resistance of cement mortar were studied. The experimental results show that the flexural strength, brittleness index (σ_F/σ_C) and abrasion resistance can be improved significantly by the addition of PP fiber and SBR polymer latex. The relationship between the flexural strength and abrasion resistance was analyzed, showing a good linear relationship between them. The reinforced mechanism of PP fiber and SBR polymer latex on cement mortar was analyzed by some microscopic tests. The test results show that the addition of SBR polymer latex has no significant influence on the cement hydration after 7 d curing. Adding SBR polymer latex into cement mortar can form a polymer transition layer in the interfaces of PP fiber and cement hydrates, which improves the bonding properties between the PP fiber and cement mortar matrix effectively.     

Modified-starch consolidation of alumina ceramics

The alumina ceramics with the homogeneous microstructure and the higher density were fabricated via the modified-starch consolidation process by 1.0 wt% of a modified starch as a consolidator/ binder. The swelling behavior of the modified oxidized tapioca starch was analyzed by optical microscope, and two other corn starches （common corn starch and high amylose corn starch） were also analyzed for comparison. The modified starch used as a binder for the consolidation swelled at about 55 ℃, began to gelatinize at 65 ℃ and then was completely gelatinized at 75 ℃. But the corn starches could not be completely gelatinized even at 80 ℃ for 1 h. The high-strength green bodies （10.6 MPa） with the complex shapes were produced. The green bodies were sintered without any binder burnout procedure at 1 700 ℃ and a relative density of 95.3% was obtained for the sintered bodies, which is similar to that of the sintered sample formed by conventional slip casting. In addition, the effect of temperature on the apparent viscosity of the starch/alumina slurry in the process was investigated, and the corresponding mechanism for the starch consolidation was discussed.     

Understanding of the influence of process parameters on the heat transfer behavior at the metal/die interface in high pressure die casting process

The current paper focuses on the influence of the process parameters on the peak values of the inter-facial heat transfer coefficient (IHTC) at metal/die interface during high pressure die casting (HPDC) process. A "step shape" casting and AM50 alloy were used during the experiment. The IHTC was de-termined by solving the inverse thermal problem based on the measured temperature inside the die. Results show that the initial die surface temperature (IDST, TDI) has a dominant influence while the casting pressure and fast shot velocity have a secondary influence on the IHTC peak values. By curve fitting, it was found that the IHTC peak value (hmax) changes as a function of the IDST in a manner of hmax =eαTγDI. Such relationship between the IHTC peak value and the IDST can also be found when the casting alloy is ADC12, indicating that this phenomenon is a common characteristic in the HPDC process.     

Template effect on structure and morphology of Ni(OH)2 powders prepared by hydro-chemical method

The template effect controlling the structure and morphology of ultrafine particles was described. Ni(OH)₂ powders were prepared by NH₃ coordination-precipitation method. The effects of SO ₄ ²⁻ , NO ₃ ⁻ , Cl⁻, NH₃, pH value on Ni(OH)₂ structure and morphology were investigated experimentally, explained with the theoretical model that the growth units were the polyhedral structure of coordination anions. The results showed that the structure and morphology of Ni(OH)₂ were effectively controlled by the growth units, the dimensions and the linking patterns of the growth units vary with the changes of physical and chemical conditions in the aqueous solution. Foundation item: The National Natural Science Foundation of China(No.59774018) Biography of the first author: LIU Zhi-hong, professor, born in 1963, majoring in hydrometallurgical technology and control of structure and morphology of powders.     

Synthesis process and growth mechanism of γ′-Fe4N nanoparticles by phase-transformation

Multiphase Fe/N nanoparticles were synthesized by means of chemical vapor reaction, the influence of the preparing parameters on the properties of particles was studied carefully during the first nitriding process. The optimum process was determined. Single phase γ′-Fe₄N was prepared by twice-nitriding. Multiphase iron-nitride really transforms γ′-Fe₄N nanoparticle of single-phase and uniform. Moreover, the mechanism of nanoparticle nucleation and growth, including phase-transformation, was revealed. In addition, the mircograph, particle size, physical phases, schemical constituents and magnetic properties before and after phase-transformation were characterized initially.     

Relationship between attachment probability and surface energy in adhesion process of gold particles to oil-carbon agglomerates

1　INTRODUCTIONInflotationfield ,someattentionshavebeenpaidtomodelingtheprocessofflotationinordertoobtainadeepunderstandingofhowamineralparticleisat tachedtoabubble .Schulze[1] analyzedtheelementaryprocessesofflotationintermsofphysico chemistry .Anfrunsetal[2 ] studiedthebubble particleattachmentexperimentallyinthecaseofpotentialflow .Solarietal[3] investigatedtheeffectofbubblesizesonadhesionprobability .Polatetal[4 ] estimatedthetruedistribu tionofflotationrateconstantsforafirst orderkin…     

Mechanism and kinetic model of <Emphasis Type="Italic">in-situ</Emphasis> TiB<Subscript>2</Subscript>/7055Al nanocomposites synthesized under high intensity ultrasonic field

In-situ TiB2/7055Al nanocomposites are fabricated by in situ melt chemical reaction from 7055Al-K2TiF6-KBF4 system under high intensity ultrasonic field,and the mechanism and kinetic model of in-situ melt chemical reaction are investigated.X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicate that the sizes of in-situ TiB2 nanoparticles are in the range of 80-120 nm.The results of ice-water quenched samples show that the whole process contains four stages,and the overall in-situ reaction time is 10 minutes.The in situ synthesis process is controlled mainly by chemical reaction in earlier stage (former 3 minutes),and by the particulate diffusing in later stage.The mechanism of key reaction between Al3Ti and AlB2 under high intensity ultrasonic in the 7055Al-K2TiF6-KBF4 system is the reaction-diffusion-crack-rediffusion.Furthermore,the reactive kinetic models in 7055Al-K2TiF6-KBF4 system are established.     

The structural evolutions of ZL109 alloy and 7050 alloy in the semisolid squeeze casting process

The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was remelted to make the grains more uniform and smooth. In the process of semisolid forming, the primary α and the eutectic inside the ZL109 alloy were separated partly and the grains in the 7050 alloy was conglutinated together. After heat treatment, the eutectic α grains of ZL109 traveled to primary α and shaped the white fishing net like organization; the eutectic Si grains assembled into the black massive particles. As to 7050, after heat treatment, α particles recrystallized and thin grains pattern was obtained.     

第三级存储器中的磁带选择算法

提出最多请求个数优先和最小请求优先磁带选择算法,用于优化磁带装载次序．为了进一步降低磁带交换代价,在如上两个算法中引入权重因子,得到加权磁带选择算法使得在线磁带卸载之前服务更多请求．实验表明,最多请求个数优先和最小请求优先磁带选择算法以及相应的加权算法均优于经典的RoundRobin方法,尤其加权最多请求个数优先磁带选择算法效率最高．     

砂型铸造的环境特征及铸造粘结剂的发展趋势

研究分析了目前广泛采用的几种典型砂型铸造方法（湿型粘土砂、呋喃自硬树脂砂、碱酚醛自硬树脂砂、CO2硬化水玻璃砂、酯硬化水玻璃砂）的环境特征,主要从产生的气体挥发物和旧砂回用性两方面分析它们的区别,从铸造粘结剂的角度讨论实现清洁生产、绿色铸造存在的问题,概述铸造粘结剂的发展趋势与方向。笔者认为,相当长时间内砂型铸造仍然是我国铸造生产的主要方式,少污染的无机粘结剂大量采用、低成本无排放的旧砂再生回用技术开发利用、铸造有害气体少量化及其无害化排放,应是我国铸造材料与技术进步的发展方向。     

聚氯乙烯胶粘带基材膜的制备

聚氯乙烯胶粘带是以通用塑料聚氯乙烯膜为基材,以压敏胶为胶料的一种新型胶粘带.本文将对其基材制造技术进行探讨.     

Abrasive Wear Map of Polymer Tapes in Sand Dust Environment

To make clear the wear conditions of ATM （Automatic Teller Machine） tribosystem when servicing in Chinese sand dust environment, abrasive wear of two kinds of polymer tapes specified for ATM, PI （Polyimide） and PEN （Polyethylene-2, 6-naphthalenedicarboxylate）, was investigated in simulated sand dust environment with ATM tape-scraper tribosystem under various conditions of loads and sliding distances. The surface profiles of worn tape were measured with a surface profiler in order to calculating the wear cross-section areas and the wear volumes. The specific wear rates of polymer tapes were calculated under load conditions of 0.6, 1 and 1.5 N, and wear mechanisms were in- vestigated with optical topography photos. As main results, the specific wear rates show stage variations in the wear process and the wear resistance of polymer tape shows good relationship with the mechanical deformation factors. In consideration of the service life, four wear models are generalized according to the magnitude of specific wear rates, which include no wear, mild wear, normal wear and severe wear model and the corresponding wear mechanisms for the four wear models are discussed with typical worn topographies. Based on the wear models and corresponding wear mechanisms, the abrasive wear maps of two polymer tapes servicing in sand dust environments are concluded for its industrial applications.