Kinetic investigation of the carbothermal reduction of an Iranian clay

The kinetics of the carbothermal reduction of clay under argon atmosphere has been investigated by the X-ray diffraction method. The clay-carbon (excess) mixture was formed into 2 cm diameter disks of different thicknesses. Experimental data evidences the significant effect of sample thickness on the reaction rate at 1400 °C. Decreasing thickness promotes mullite dissociation and formation of SiC and alumina powders. Mathematical modeling of the reaction system showed the gas diffusion in the Knudsen regime through the pellet to be the rate controlling step. Diffusivity of CO and reacted core tortuosity factor have been calculated.     

X-ray structure analysis and elastic properties of a fabric reinforced carbon/carbon composite

The effect of heat treatment on microstructure of a plain-weave carbon fabric reinforced carbon-carbon composite with phenolformaldehyde-derived carbon matrix was investigated by X-ray diffraction. The diffraction patterns were analysed by the least-square fitting program Carbonxs. After heat treatment from 1000 to 2800 °C the interplanar distance of (002) planes decreased from 3.488 to 3.420 Å and the lattice parameter in basal plane increased from 2.440 to 2.464 Å, respectively. Simultaneously, the coherent block size in the basal plane directions increased from 18 to 54 Å, which was accompanied by an increase of the fraction of organised carbon atoms from 0.50 to 0.85. The 002 diffraction profile of the composite was much narrower than the sum of peaks of the matrix and fabric alone. This can probably be caused by a better crystallographic ordering (or by a partial graphitisation) of the matrix in the composite. On the other hand, the composite Young’s modulus slightly decreased with the treatment temperature increasing from 2200 to 2800 °C in spite of the established strong improvement of fibre crystallinity and, therefore, fibre modulus. The mechanisms diminishing the modulus of composite (e.g. partial matrix graphitisation at the fibre/matrix interface and decreasing fibre/matrix contact area) probably prevailed over the increasing contribution of the fibre modulus.     

A3钢的工业大气腐蚀

在辽宁省工业城市进行 A3钢大气暴露试验。两年后测出不同地点腐蚀率。依据所记录的各试验点的气象数据和污染数据,讨论了 A3钢的大气腐蚀规律。     

Possible tactics to improve the growth of single-walled carbon nanotubes by chemical vapor deposition

The growth time, growth mode and the method of preparing the supported catalysts play an important role in the growth of single-walled nanotubes (SWNTs). Their effects on the chemical vapor deposition (CVD) growth of SWNTs with MgO-supported catalysts were investigated in this study. It is shown that the growth rate of SWNTs was large during the initial few minutes of growth, however the quality of the tubes was low owing to the formation of many defects. Long term growth may favor the formation of tubes with high quality and high yield, but the introduction of other forms of carbon (impurities) is also unavoidable. There was a balance between the increase in yield and quality and sacrifice of the purity during growth of SWNTs. MgO-supported catalysts prepared by the co-precipitation method were found to be more effective for the synthesis of SWNTs than those prepared by the widely used impregnation method. The size and dispersion state of the catalyst were found to be crucial in enhancing the growth of SWNTs. In addition, growth on the surface of SWNTs over nanosized catalyst films was shown to be more favorable for the synthesis of tube products with higher quality, yield and purity.     

Irradiation Defects in Silicon Crystal

The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.     

Effect of Traveling Magnetic Field on Mould-Filling Length of the A357 Melt during Casting THin Walled Plate

In order to improver the mould filling ability ,the method for production of thin-walled castings in the traveling magnetic field was applied,The relationship between magnetic field density and input voltage as well as distance was investigated,and the mould filling length of A357 melt has been studied,The electromagnetic forces applied on the melt were also analyzed,The result shows that the mould-filling length of the melt increase rapidly with the increase of magnetic flux density,The mould filling lengths in gypsum upper mould and magnetic material upper mould were compared from the standpoint of application,It demonstrated that the steel upper mould is superior to gypsum mould.     

利用单片机80c196kc实现等间隔采样及采样值的回显

本文主要介绍以单片机80c196kc为CPU对模拟信号进行等间隔采样以及实现对采样值回显的问题。详细介绍了测频软件及电路的实现，对等间隔采样软件实现进行了详细论述：详尽讨论了对于MG-12864-2液晶显示器的电路连接与软件控制方法；对MG-12864-2液晶显示器应用的独特之处做了细致的分析。     

Microstructural changes accompanying repair welding in 5xxx aluminium alloys and their effect on the mechanical properties

At the shipyards, the aluminium alloy 5083 is welded with a multi-pass sequence using the metal inert gas technique. If, while checking the weld integrity either after welding or during service, defects are detected in the vicinity of the weldment, repairs are usually employed to extend the service life.

The repair method involves removal of the upper passes, depending on the thickness and re-welding under the same conditions.

Purpose of this paper is to examine the microstructural changes accompanying repair welding, define their effect on properties of primary importance and set, if possible, an upper limit as far as the number of repairs is concerned.     

Microstructural investigation of the breakdown of the protective oxide scale on a 304 steel in the presence of oxygen and water vapour at 600 °C

This article focuses on the detailed microstructural investigation of the oxide scale formed on a 304 steel in the presence of oxygen and water vapour (40%) at 600 °C. The work has been carried out using a combination of microanalytical techniques including FIB, TEM, EDX and electron diffraction. The local breakdown of the initially protective oxide scale and the growth of island/crater oxide morphology are described. Special consideration is given to the influence of the microstructure of the steel and the oxide scale on the breakdown behaviour.     

Ecophysiology of ochratoxigenic Aspergillus ochraceus and Penicillium verrucosum isolates. Predictive models for fungal spoilage prevention - a review

Ochratoxin A (OTA) is a secondary metabolite produced by several species of Aspergillus and Penicillium; among them Aspergillus ochraceus and Penicillium verrucosum are two ochratoxigenic species capable of growing in different climates and thus contamination of food crops with OTA can occur worldwide. OTA can be found in a wide range of foods such as cereals, coffee, cocoa, spices, beer, wine, dried vine fruit, grapes and meat products. OTA is toxic to animals, it presents neurotoxic, immunotoxic and nephrotoxic effects. It has been implicated in a human kidney disorder known as Balkan Endemic Nephropathy. This review focuses on the ecophysiology of ochratoxin-producing Aspergillus ochraceus and Penicillium verrucosum, the effect of environmental factors on their germination, mycelial growth, and OTA production. Knowledge of environmental conditions required for sucessive stages of fungal development represent the first step towards preventing mycotoxin formation. Predictive models for different stages of fungal development are presented, which allow prediction of the time before spoilage as a function of the abiotic factors. Finally, the implications of these studies in management of barley, coffee and grapes are described. This can help to identify the critical control points in their production, storage and distribution processes.