Advanced Materials Research Vols. 264-265

Abstract: The present paper deals with the microstructure and hardness distribution in width and in depth of the surface layer of steel Ch18N10T GOST (AISI 321, EN X6CrNiTi 18-10) after surface melting by continuous wave CO2 laser. Light microscopy, XRD analysis and Vickers hardness testing (HV5 and HV0,05) have been used in our research. Phase analysis shows disturbance of the mono-phase initial austenitic structure in the treated layer. The structure of the melted pool consists of austenite with dendrite morphology and δ-ferrite situated in the dendrites’ cores. The ferrite has been clearly identified by XRD analysis. As a result from fast heating and cooling, ferrite, obtained by diffusionless sliding mechanism, was observed along the austenite grains’ boundaries in the heat affected zone. The presence of small inclusions of supposed Ti carbide, non-identified by XRD analysis, was also observed. The durometric investigations show that the surface hardness in the melted zone is in the range 180-210 HV5 while that of the basic metal is about 270 HV5.

Abstract: In this study, simulation based on a theoretical model was made to investigate the influence of inertial effect and friction force to CNC machine’s accuracy and to explore the functions of related control parameters. By using empirical method, an auto-tuning system that can on-line tune the CNC control parameters based on the detected weight of workpiece was developed. In addition, an on-line weight identifying system was also developed. After integrating the two systems, an intelligent parameter-tuning system which can be directly implanted into CNC controller was developed. Experimental results have shown that the system can effectively improve the accuracy of a machine tool through on-line control parameter tuning.

Abstract: The mechanical and metallurgical properties of the 630 (17-4PH) precipitation hardening stainless steel is greatly influenced by the type of applied heat treatments cycles. In order to achieve the homogenous microstructure in the weld metal and eliminate the HAZ due to producing the weak mechanical strength, and producing similar microstructures and mechanical strength in both weld and base metal, the study was conducted to find an optimum pre and post heat treatments before and after welding. The 2.2mm thick and 48mm tube diameter made of 630 stainless steel were welded under various operational parameters. The samples were subjected to pre weld solution treatment and post weld aging heat treatment. To reveal the microstructures of the welds, the optical and scanning electron microscopy of the welds carried out. The study shows that the direct ageing treatment at 6200C after welding can give rise to the best heat treatment to produce, the uniformity in the grain size, mechanical strength and hardness, between the base metal and the weld metal.

Abstract: Micromachining of advanced ceramics has been growing tremendously especially in the MEMs industry. All the time, researchers and industrial engineers have strived to achieve the lowest production cost at possible highest quality in micromachining operations. In this paper, the micromachining operation by means of chemical etching of ceramics is discussed. Machinable glass-ceramic (MGC) is used as the substrate and the influence of various input factors of the etching process is analyzed. These factors include etching temperature, etching period and, etching solution. The etching rate is then analyzed by calculating the weight loss per minutes. In order to establish the relationship between these factors, central composite design (CCD) and artificial neural network are used. Additionally, a prediction model that can be used with a high level of confidence in the industry is created at the end of the analysis.

Abstract: This paper is the results of oxygen ion implantation on morphological and electrical properties of indium phosphate (InP) semiconductor wafers. The oxygen ions were implanted at 30 keV and various doses in the range between 5×10 15 to 5×10 17 ions/cm2 and at nearly room temperature. The changes in surface roughness and resistivity before and after the implantation is studied using atomic force microscopy (AFM) and four-point probes technique, respectively. The results show that the resistivity is depend on the ion implantation dose. In addition, the RMS roughness of implanted samples dramatically increases by accumulation of oxygen ion dose.

Abstract: Laser beam machining (LBM) is the most exciting thermal energy based non-contact type advanced material machining method to process almost whole range of materials. The laser microturning of ceramics are highly demanded in the present industries because of its wide and potential uses in various engineering fields such as automobile, electronics, aerospace, biomedical applications etc. The present paper addresses the basic experimental study of Nd:YAG laser microturning of advanced engineering cylindrical shaped ceramic material to explore the desired laser output responses i.e. depth of cut and surface roughness by varying laser micro-turning process parameters such as lamp current, pulse frequency and rotational speed of workpiece etc.

Abstract: The growth behavior of carbon nanotubes (CNTs) grown on electron bombarded catalyst layer has been investigated in this paper. A hot cathodic electron beam facility was employed to electron bombarding of catalyst layer before stage of CNTs growth. The growth of carbon nanotubes was performed on the Fe catalyst layer with sio2 substrate in an environment of different mixed gases (H2, NH3 and C2H2) by Thermal Chemical Vapor Deposition (TCVD) system. The pretreated substrates were probed by Atomic Force Microscopy (AFM) and CNTs grown was confirmed by Raman spectroscopy. Moreover, all samples were analyzed by Scanning Electron Microscopy (SEM) before and after growth of CNTs. SEM analyzes clarified that the catalyst grains has been smaller under effect of electron beam bombardment.

Abstract: In this research hydroxyapatite powder was synthesized by wet chemical method using calcium nitrate and diammonium hydrogen phosphate precursors at 2, 20, 50 and 90⁰ C. Phase composition, morphological aspects and particle size have been investigated using X-ray diffraction method (XRD), Fourier transform infra red spectroscopy (FTIR) and scanning electron microscopy (SEM). For the low synthesis temperature, products with low degree of crystallinity were obtained and the phases like calcium deficiency hydroxyapatite (CDHA) and hydroxyapatite were formed. In higher temperature ranges, higher degree of crystallinity was measured. For these samples, crystallite sizes estimated by scherrer formula and measured directly by SEM were found to be less than 100 nm. The synthesis temperature of 90°C has showed better results from crystallinity point of view. Considerable crystallinity of the powders produced in this research is almost comparable to that of conventional heat treatment used for enhancing the crystallinity.

Abstract: Electrochemical micromachining (EMM) appears to be promising as a future micro machining technique since in many areas of applications; it offers several advantages including electronic, biomedical and MEMS/NEMS applications. Present paper will highlight the influence of various EMM process parameters i.e. machining voltage, electrolyte concentration, frequency pulse period and duty factor on machining performance criteria e.g. material removal rate and machining accuracy to meet the micromachining requirements. Some of the experiments had been carried out on copper to investigate the most effective zone, which gives high machining accuracy with appreciable amount of material removal rate. Attempt has also been made to study and compare the surface condition of the machined micro-holes through SEM micrographs. From the analysis of test results and SEM micrographs it can be observed that optimum value of frequency pulse period is about 200 μsec and duty factor is about 20% which will produce accurate micro-holes with highest possible amount of material removal.

Abstract: Titanium dioxide is a cheap, chemically stable and non-toxic material. However its photocatalytic properties are unstable and it is a modest semiconductor and a mediocre insulator. For several applications it would be interesting to make it either more insulating or more conducting. The goal of this work was to modify the photocatalytic properties of nano-crystalline TiO2 powders by wet chemical routes and hydrothermal methods to understand the mechanism leading to these modifications The principal factors that influence the photocatalytic properties are on the one hand the concentration and nature of the chemical and physical conditions in TiO2, and on the other hand the morphology of the powders. The study was split into two parts. The fist part describes the modifications of the material obtained by chemical preparation's parameters. Like: preparation method, pH., additives, surfactants, and temperature. The second part describes the modifications obtained by modifying the photo catalysis reactors. Several analysis techniques have been used to characterize the TiO2 samples. They are essentially divided in four categories. The chemical analyses included electron probe microanalyses. The structure and morphology analyses of powders were carried out with x-ray diffraction. The photo catalytically properties in batch or CRS mode were measured in room temperature. Finally optical transmission provided information on the electronic states and morphology of the samples. The results imply that powders with anatase 40% and rutile 60 % with 15nm crystallite size have the optimum properties.