尿素对以硝酸铝和葡萄糖为原料合成氮化铝粉末反应过程中相变及反应速率的影响

以硝酸铝(Al(NO3)3·9H2O)和葡萄糖(C6H12O6·H2O)为原料,利用碳热还原法制备氮化铝粉末,研究了尿素对前驱物的制备及前驱物氮化反应的影响,研究发现添加尿素合成的前驱物和未添加尿素合成的前驱物在氮化反应过程中相变和反应速率存在较大差异。在没有添加尿素合成的前驱物的氮化反应过程中,出现了γ-Al2O3、α-Al2O3、AlON和AIN相,该前驱物的反应速率慢,完全氮化需要在1600℃下才能完成。对于添加尿素合成的前驱物而言,在其氮化反应过程中仅出现了γ-Al2O3和AIN相,没有α-Al2O3和AlON的生成,AIN直接由γ-Al2O3氮化生成,该前驱物的氮化反应速率快,氮化反应温度低,在1400℃下即可实现完全氮化。分析讨论了两种前驱物的氮化反应速率不同的主要原因,并利用XRD、SEM等分析方法对粉末进行了表征。     

低热固相反应制备纳米铈镍铁氧体粉末

采用Ce(NO3 ) 3 ·6H2 O、NiSO4·6H2 O、FeCl3 ·3H2 O和H2 C2 O4·2H2 O为原料 ,室温固相反应制备出相应的草酸盐前驱物 ,将前驱物在 3 80℃下分解 3h ,得到Ce0 .2 5NiFeO3 的棕黑色粉末 ,用热分析、X射线粉末衍射、透射电镜、扫描电镜对产物的组成、大小、形貌及有关性质进行了表征。结果表明获得了平均粒径为 3 0nm、分布均匀、无团聚的铈镍铁氧体纳米粉末     

水热合成KAl(OH)2CO3粉体的形貌控制

分别采用AlCl3·6H2O,Al(NO3)3·6H2O,Al2(SO4)3·12H2O为前驱体在水热条件下合成了KAl(OH)2CO3粉体.实现了KAl(OH)2CO3粉体的微观形貌从纤维状微米级颗粒到柱状两维纳米级颗粒的控制.XRD、TEM等的分析结果表明,水热体系中的铝盐种类、阴离子浓度以及反应时间等条件对所合成产物的颗粒形貌有显著的影响.其中Al(NO3)3是合成KAl(OH)2CO3的最佳前驱物,当[NO-3-]=1.2mol/L时,在120℃,反应4h条件下合成的粉体颗粒直径小于20nm,长径比约为5,且外形规整,粒度分布均匀,没有团聚.     

LiFePO4的前驱体制备与性能

以Fe2(SO4)3、H3PO4和NH3·H2O为原料,采用控制结晶法制备了多孔的前驱体FePO4·xH2O.通过研究pH值和合成时间对前驱体的物相结构、成分、表面形貌、粒度、比表面积和振实密度的影响,发现在pH=2.1的条件下反应8h制备的前驱体性能最佳.将前驱体、Li2CO3及葡萄糖均匀混合,用碳热还原法合成了LiFePO4/C,结果表明,以pH=2.1时制备的前驱体为原料合成的LiFePO4/C在0.1C时的首次放电比容量为156mAh/g,其振实密度高达1.20g/cm3.     

固相反应制备网状Fe(Co0.5Ni0.5)O5复合氧化物及其电磁学性质研究

在低热固相条件下,采用FeCl2·4H 2O,CoCl2·6H 2O,NiCl2·6H2O与NH4HCO3进行反应,制备出铁钴镍的混合前驱物,在580C下分解该前驱物.分解产物经XRD、SEM、TEM、粒度仪表征和化学分析后,获得了具有特殊网状结构,网骨直径约为25nm,网骨长度和直径比例为5的Fe(Co0.5Ni0.5)O5复合氧化物粉体.对该粉体进行电磁学性质(介电常数ε、磁导率μ和吸波特性γ)测试后发现,其电磁学性质和吸波特性较其它铁氧体粉末改善明显.     

放电等离子烧结制备Ca2Co2O5热电材料及其性能研究

以Co(NO3)2·6H2O、Ca(NO3)2·4H2O为原料,NaOH为沉淀剂,采用化学共沉淀方法制备了前驱物.该前驱物预烧后,利用SPS进行烧结获得纯相Ca2Co2O5块体.分别采用DTA-TG、XRD和SEM对前驱体的热分解过程、Ca2Co2O5的形成过程进行了表征,并对其热导率进行了测试.结果表明在Ph=13.20获得所需化学计量比的前驱物.该前驱物在700～800℃预烧2h后,采用SPS烧结.烧结温度为800℃,压力30MPa,保温时间5min,可以获得纯相Ca2Co2O5块体.断口形貌为层状,晶粒长约1.4μm.热导率随温度的升高而降低.     

高温气-固反应水解制备八面体形四氧化三钻粉末

提出了一种以CoCl2·xH2O为原料,高温气-固反应水解制备四氧化三钴粉末的新方法,实验考察了反应温度、氯化钴结晶水含量及惰性分散介质的添加对产物的影响.采用X射线衍射、扫描电镜、激光粒度分析对样品的物相、形貌、粒度等进行了表征.结果表明：制备的粉末颗粒由{111}晶面所包围,呈八面体形貌,粒度在亚微米至微米级;反应温度越高,产物粒子的粒径越大;以COCl2·2H2O为原料制备的粉末粒径分布范围较窄;惰性分散介质的添加改善了粉末的单分散性.简要分析了形成八面体形貌的原因及各因素对粉末形貌与粒度的影响.     

混合溶剂沉淀法制备纳米NiO及其表征

采用NiCl2·6H2O和Na2C2O4为原料,在混合溶剂乙醇 水溶液中,通过化学沉淀法制备出一种浅绿色前驱物,以前驱物的热分析结果为依据,在400℃分解3h可得产物NiO粉体。经XRD、比表面积测定和TEM分析表明,产物为平均粒径23nm且粒径分布均匀、无团聚的球形纳米NiO粉体。     

Ca2Co2O5化合物的制备及热电性能的研究

以Co(NO3)2·6H2O,Ca(NO3)2·4H2O为原料,Na2CO3为沉淀剂,采用化学共沉淀法和放电等离子烧结(SPS)制备了Ca2Co2O5化合物.采用TG-DTA、XRD和SEM等手段对前驱体的热分解过程,样品的物相以及形貌进行了表征,测试了Ca2Co2O5的热电性能.实验结果表明沉淀前驱物经850℃预烧8 h后,利用SPS 850℃,压力30MPa保温5min,制备了纯相Ca2Co2O5化合物.该化合物的电阻率和热导率均随温度的升高而降低,800℃时,热电性能优值(ZT)为0.12.     

纳米Co_2O_3前躯体的室温固相反应工艺研究

采用室温固相反应合成纳米Co3O4前驱体,用X-射线衍射分析(XRD)和透射电镜(TEM)等手段对前驱体的制备工艺进行了研究,就不同工艺对前驱体形貌、尺寸和产率的影响规律进行了探讨。结果表明,采用CoSO4·7H2O和H2C2O4·2H2O为原料制备的前驱体均为单斜相的CoC2O4·2H2O。在压应力作用下,前驱体的形貌主要为不规则多边形,颗粒尺寸在50～500nm范围内变化。而无压应力作用时,前驱体形貌为不规则形状,颗粒尺寸均匀,约为150～200nm。前驱体的产率与工艺参数有较大关系,对反应物分别研磨或反应物混合研磨、施加压力、升高温度和提高H2C2O4·2H2O的量将有利于提高前驱体的产率。     

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...     

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.     

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.     

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.……     

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.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

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.     

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.     

Instructions & Forms for Authors

Journal of Materials Sciences ＆ Technology is a monthly journal for the rapid dissemination of new, impor- rant results in material and related fields. Submission Electronic files of MS Word and PDF are acceptable. Please visit http：//www.jmst.org and submit online.