纳米塑料研制进展(续)

综述了纳米塑料（包括PE、PP、PVC、PET、PBT、PA）的研制、性能、应用和展望。     

掺镉纳米SnO2的热稳定性,电导及气敏性能

本文研究了ＣｄＯ掺杂对纳米ＳｎＯ２粉料的热稳定性，电导及气敏特性的影响。结果表明，以非晶状态均匀分散在ＳｎＯ２颗粒表面的ＣｄＯ能阻止ＳｎＯ２之间的相互扩散，提高了纳米ＳｎＯ２的热稳定性；固溶于ＳｎＯ２昌粒中的ＣｄＯ量（Ｃｄ／Ｓｎ〈０．０５）很小，但对元件的电导影响显著；纳米级的晶粒尺寸（〈６ｎｍ）及ＣｄＯ的掺杂大大改善了ＳｎＯ２的气敏特性。     

Changes in seebeck coefficient of Pt and Pt 10% Rh after use to 1700°C in High-purity polycrystalline alumina

A technique is presented that enables the effects of temperature on the Seebeck coefficient to be assessed for individual wires. The technique, involving a high-resolution thermoelectric scanning rig and a nonuniform conditioning furnace of known temperature profile, was applied to 0.5-mm-diameter wires of Pt and Pt 10% Rh. Changes were observed in Seebeck coefficient when these wires were used in high-purity twin-bore insulation for up to 200 h at temperatures over the range 500 to 1700°C. Contamination from the insulation was found to be transmitted by a vaporization process, having an activation energy of 3 eV. This caused changes of up to 0.14 V · °C^–1 in Pt and 0.01 V · °C^–1 in Pt 10% Rh. Rhodium transfer to the pure Pt wire changed its Seebeck coefficient by up to 5 V · °C^–1. The consequences of both processes for thermocouple pyrometry are presented.     

我国氧化铝工业现状及发展对策

在分析了国内外氧化铝工业的现状及差距的基础上，提出了发展我国氧化铝工业的六条战略措施及对策。     

Porous structures printed by fused deposition of granules processed from a novel polyamide/alumina-based system

Alumina ceramic porous structures were shaped by the fused deposition of alumina/polyamide 612 composite granules using an FDM 3D printer with a modified extruder to process granulated powder instead of a filament. The composite granules were prepared via thermally induced phase separation (TIPS). Firstly, in order to determine the proportion of polymer/solvent to be used in the TIPS process, different volume fractions of PA612 in dimethyl sulfoxide (DMSO) were studied (0.01 to 0.20), and the granules obtained were characterized by SEM, DSC, and Raman spectroscopy. Secondly, the addition of different ceramic loadings to the PA612/DMSO solution was studied with the aim of determining the amount to be used for preparing the composite granules by TIPS. In particular, the effect of the alumina content on the morphology and size of the obtained composite granules was studied. In addition, rheological properties (oscillatory and rotational tests) of the feed materials were studied. Finally, the printing conditions, including the nozzle temperature and nozzle diameter, and the extrusion process, were optimized in order to obtain porous structures with good quality. Alumina porous structures were successfully printed, debinded, and sintered. Adequate bonding between layers was achieved, and no defects at interfaces were detected.     

煤粉炉粉煤灰提取氧化铝活化技术研究进展

介绍了近年来采用煤粉炉粉煤灰作为原料制备氧化铝的预处理活化工艺技术,指出了粉磨法、硫酸法、氯化钙法、铵盐法、碳酸盐法、氟化盐法、物理-化学联合活化法的优缺点及在工程转化过程中需重点关注的环节。虽然部分工艺技术实现了工业化,但因成本高等因素导致项目关停,建议粉煤灰综合利用研究方向应以工程转化难点问题为导向,理论研究与工程设计相结合,逐步探索出一条经济效益好、安全环保的粉煤灰制备氧化铝工业化路线。     

Net shape formation of sub-micron alumina with reduced flaws by high-speed centrifugal compaction process

A new compacting method for powder materials is presented. High-Speed Centrifugal Compaction Process (HCP) utilizes centrifugal force of about 10,000 g for the compaction. HCP is suitable for net shape compaction of fine sub-micron and nano-powders. HCP possesses a unique compacting mechanism that is different from other colloidal processes including Pressure Casting (PC), and has a number of useful characteristics. HCP has a higher compacting speed than PC, wide applicability for net shape formation, as well as a defect removing function. Because of homogeneous and flawless green microstructure, HCP alumina shows superior sinterability and higher strength and hardness than most of other aluminas. This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials“, held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

Preparation and mechanical properties of Fe_3Al/Al_2O_3 nano-/micro-composite

1　INTRODUCTIONAlumina(Al2 O3)ceramicsareoftenconsideredforstructuralapplications,duetotheirpropertiesofhighhardness ,chemicalandwearresistanceandgoodmechanicalpropertiesatroomandhightemperature .Thewellknownlimitationfortheseceramics ,how ever ,istheverylowtoughness .Recentstudieshaveshownsignificantimprovementsinmechanicalprop erties ,includingtoughness ,byaddingductilesecondphaseparticles ,suchasNi,Al,MoandCu[14 ] .Anincreaseof 80 % 333%inthefracturetoughnesshasbeenreportedforAl2 O3…     

Optical Investigation of the Effects of Substrate Orientation on Oxidation of Single Crystal β-NiAl

The residual stresses in -Al₂O₃ scales formed on high-purity FeCrAl and FeCrAlY during oxidation at 1200°C and subsequent cooling and reheating were studied using photostimulated luminescence spectroscopy. Systematic measurements of the stress in the oxide were made as a function of both alloy thickness and cooling rate and the development of stresses in the oxide scale during thermal cycling was investigated as a function of the temperature. Depending on the ratio of the alloy and oxide-scale thicknesses, substantial stress relaxation was observed to occur during cooling at a rate of 8 K/min. Compressive growth stresses of 1 GPa were determined by comparing the residual-stress measurements at room temperature with those calculated based on thermal-expansion mismatch. No significant differences in the growth stresses, the total residual stresses, or the stress relaxation during thermal cycling were observed between the oxides formed on the Y-doped and undoped FeCrAl samples. Stress relaxation is also shown to lead to the development of tensile stresses in the oxide scale under certain conditions, in particular, those associated with slow cooling followed by rapid heating.     

The application of thermal sprayed coatings for pig iron ingot molds

Molds made of gray cast iron for casting pig iron ingots are subjected to severe temperature fluctuations. The main life- limiting factor for mold damage is the formation of surface cracks arising from thermal fa-tigue. Various flame and plasma sprayed coatings were investigated to extend the life of these molds. Coating materials studied include plasma sprayed ceramic coatings with bond coats as well as flame sprayed oxidation- resistant alloy powders. The results of cyclic furnace tests from room temperature to 1100 °C in air, simulating the thermal cycle in casting, indicated that failure occurred along the interface between the bond coat and the gray iron substrate because of iron oxidation, and not at the interface between the ceramic top coat-ing and the bond coating for a superalloy substrate. The field test results indicated that plasma sprayed alumina coatings with 200 μm top coating thickness are the most promising materials for pig iron casting.