The early stage oxidation and evaporation of Mg-9%Al-1%Zn alloy

Thermogravimetric technique was used to determine the oxidation and evaporation behaviour of AZ91D magnesium alloys with 5 and 10 ppm of beryllium at temperatures between 200 and 500 °C. Depending on temperature and time, the alloy experienced protective or non-protective oxidation with linear or accelerated oxide growth kinetics. During reaction in an oxidizing atmosphere, the additions of beryllium delayed the transient from the protective to non-protective scale formation. In an inert atmosphere, increased beryllium contents reduced the magnesium evaporation rate.     

Grinding-hardening with liquid nitrogen: Mechanisms and technology

This paper studies an innovative development of a steel grinding–hardening technology using an inert cryogen—liquid nitrogen. It was found that phase transformations took place during grinding with the application of liquid nitrogen and resulted in hardened surface layer in a ground component. The layer had a fine laths martensite structure which gave rise to a remarkably high hardness. It was also shown that the treatment can produce superior surface integrity, with compressive surface residual stresses and without surface oxidation. Due to the inert nature of the liquid nitrogen, the grinding process becomes environmentally conscious.     

铝炭砖的抗氧化性能

实验表明，铝炭砖具有良好的抗氧化性。致密型铝炭砖（A1－C1）的抗氧化性比热压半石墨砖要好，其砖面易在高温（1200℃）下形成保护层。     

Fluorescent Brightener 28 Removal by Ozonation or Advanced Oxidation Processes (O3/H2O2)

The aim of this work is to study the reaction of ozone and combined ozone/hydrogen peroxide mixtures with the fluorescent brightener 28 in dilute aqueous solution using controlled experimental conditions. The kinetics were also evaluated under various experimental conditions. The main ozonation by-products have been identified by High Pressure Anionic Exchange Chromatography (HPAEC) and Gas Chromatography coupled with Mass Spectrometry (GC-MS) techniques and a reaction pathway is proposed. In order to confirm this mechanism, melamine and s-triazine have been treated under the same reaction conditions and their decomposition pathways were studied.     

环己烷液相无催化剂的氧化动力学研究

采用搅拌釜反应器,在确认已排除传质因素对反应速率影响的情况下,研究了环己烷液相无催化剂的氧化反应动力学。应用自由基理论及最优化计算技术,从导出的8个候选动力学模型中,确定了最佳的动力学模型,它能满意地描述环已烷氧化过程。该动力学可为环己烷氧化工业生产操作条件的优化、反应器的选型及工业设计提供依据。     

Oxidative functionalization of carbon nanotubes in atmospheric pressure filamentary dielectric barrier discharge (APDBD)

The surface compositional and any structural changes that occur on carbon nanotubes using air-atmospheric pressure dielectric barrier discharge (APDBD) for functionalization are investigated employing Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and neutron diffraction techniques. Atmospheric pressure plasmas (APP) are suggested to be particularly suitable for functionalization of aligned nanotubes, where wet chemical manipulation could damage or even destroy the highly desirable vertical alignment. In this work a detailed experimental study elucidating the effects of APDBD plasma treatment parameters (e.g. power density, discharge composition, inter-electrode gap and treatment time) on the electronic structure, physical, and chemical behaviour of carbon nanotubes has been conducted. In an atmospheric air we find an optimal oxidative functionalization of CNTs in our DBD system within few seconds (<5 s) at a discharge power of ∼0.5 kW. This investigation may find useful application as functionalization technique for CNT engineered devices and sensors.     

STEAM OXIDATION OF CARBON FORMED BY THERMAL DEGRADATION OF PMMA IN ALUMINA

In the processing of multilayer ceramic multichip modules (MCM's), a ceramic substrate, such as alumina, along with a polymer, such as poly(methyl methacrylate) (PMMA), solvents, plasticizers, flocculants, is thermally degraded before sintering. The thermal degradation of PMMA from the green body of oxide ceramics leaves behind some amount of residual carbon in the ceramic. Carbon concentration above 100 ppm has a deleterious effect on the physical properties such as fkxural strength, density, breakdown voltage and dcnsification behavior of the ceramic. This paper discusses the kinetics of oxidation of carbon formed by the thermal degradation of poly(methyt methacrylate) in alumina. Pellets of 5 urn and I urn size alumina were made at 6000 psig in a single step change. Kinetic runs were made in the temperature range of 673 to 993 K with steam as the oxidant at a flow rate of 9.96E-03 g/cm² sec. The organics (polymethyl methacrylate, methyl ethyl ketone, methanol) concentration was varied from 5 to 20 by weight%. The oxidation products were analyzed using a Varian 3700 gas chromatograph coupled with CDS 111 integrator, and by volumetric analysis. Carbon analysis was carried out at the IBM Fishkill center using a Leco analyzer. Kinetic rates and activation energies are evaluated.     

LOW TEMPERATURE OXIDATION OF LOW RANK COALS

The low temperature oxidation of a Montana subbituminous coal was investigated using round bottom 100 ml flasks in constant temperature baths. The experiments were carried out in normal and oxygen enriched air at 30°C, 45°C and 70°C with particle sizes ranging from 4 mesh to 100 mesh. Periodic analysis of gas samples from the flasks provided the rate data. The reactivity of the as received coal was compared with that of the same coal dried (i) in high pressure steam and (ii) in hot water

A rate equation has been proposed incorporating the effects of oxygen diffusion and surface reaction. For higher oxygen concentration and smaller particle sizes, the zero order surface reaction was found to be controlling. The temperature dependency of the reaction rate was found to be well represented by the Arrhenius equation. The activation energy varied slightly under various conditions between 15 to 20 kca)/g mole

The reactivity of the hot water dried coal was found to be similar to that of the as received coal. Steam dried coal however, was found to be much less reactive.     

Si_3N_4结合SiC窑具材料抗氧化涂层的研究

本文针对Si_3N_4结合SiC窑具材料在900—1100℃易氧化的特点,研制了该材料的抗氧化涂层,并用试验验证了涂层的抗氧化性能。结果表明:抗氧化涂层的抗氧化效果十分显著,具有很好的推广价值。     

用于甲烷选择性氧化反应制甲醇的膜催化技术

研究了将甲烷选择性地一次氧化制取甲醇的膜催化技术。采用ZrO2－Y2O3陶瓷膜，在较温和的反应条件下（常压，460℃左右），可以将甲烷选择性地一次氧化成为甲醇。