Defect and Diffusion Forum Vols. 326-328

Abstract: The transformation of the solidification microstructure and the phase changes in AISI M2 grade high-speed steel modified with powder addition of TiB₂ have been studied focusing on the effect of austenitising temperatures. In order to investigate kinetics of both the microstructure and phase transformations in eutectic carbides, primarily M₂C carbide decomposition, upon heat treatments with respect to diffusion processes, different techniques of electron scanning microscopy, X-ray diffraction analysis and energy dispersive X-ray spectrometry have been used.

Abstract: In this study, low density polyethylene (LDPE) matrix composites were manufactured with the ratios of 20%, 30% and 40%wt hazelnut and peanut reinforcements as the natural fibers. Composite plates were manufactured by using a single screw extruder. Various tests and measurements are performed to obtain mechanical properties such as density, tensile strength (TS), Youngs modulus (YM), failure strain (FS), impact strength (IS) etc. as well as the effect of maleic anhydride grafted resin as an additive with different ratios was investigated and the optimum composite content was obtained. This preliminary work showed that hazelnut and peanut fillers could be utilized with proper additives in order to produce the composite materials with good physical and mechanical properties.

Abstract: In this work special attention is paid on the direct visualization of the diffusion process of oil droplets in supercritical carbon dioxide as well as a better characterization of the process by quantitative evaluation of the diffusion coefficients obtained with a shearing interferometer. Experiments are also to be carried out under microgravity in to improve the experiment condition where the influence of gravity-driven convection that usually dominates the transport process is minimized.

Abstract: Manufacturing processes involve the input of high quality energy and/or dissipation of low quality energy to manipulate a material; similarly the input of high quality material usually leads to the generation of low quality materials. A useful output involves the operation of conventional processes including a wide variety of functions such as lubrication, air compression, cooling, heating, pumping, etc., which have, on the one hand, high energy and material consumption and, on the other hand, losses due to an inherent departure from reversible processes. This paper presents an energy-flow methodology to determine the ratio between the additional energy required per useful energy unit for the manufacturing processes. As an application of the method proposed in this work, an assembly and welding production line is shown as a case study. This process is a common technique used in the manufacturing industry and its energy consumption depends on several parameters e.g. heat and electrical input. As a result of this study, the energy consumption of the production line has been reduced by approximately 30% from the 645.94 Wh of total energy consumption, where the consumption of real useful energy is 4% of this total.

Abstract: An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by three-component reaction of malononitrile, aldehydes and N-unsubstituted amidines, under aqueous conditions, using CuO nanoparticles as catalyst is reported. The protocol offers advantages in terms of higher yields, short reaction times, and mild reaction conditions, with reusability of the catalyst.

Abstract: The thermo-reactive diffusion (TRD) process is used for diffusing an element to the metallic steel substrate. TRD is carried out by using either salt bath or fluidized bed methods. In this research, the molten salt bath method is used. Ferro chromium was dissolved in the molten borax as the source of chromium in the salt. Samples of cylindrical shape of plain carbon steel with 10 mm diameter and 20 mm height were treated at 1000°C for 14 hours in different baths including either low carbon ferro chromium (LCFC) or high carbon ferro chromium (HCFC) powder. The purpose of this research is to investigate the effect of the salt bath composition on the diffusion of chromium and formation of chromium compound layer on plain carbon steel by using the salt bath method. The coating thickness layers were measured by SEM. The different phases formed on the samples, due to different amounts of carbon in treating salt bath, were determined by X-ray diffraction. It was found that in molten borax salt with high carbon content (high carbon ferro chromium) very few amount of chromium diffused into the plain carbon steel. The thickness of the diffused chromium layer in low and high carbon content ferro chromium in molten borax, is around 32±8 µm and 6.8±1.2 µm, respectively. A number of tests were conducted to address this effect.

Abstract: Synthesized samples were crystallized at 10 - 1000 K/sec (ν_cooling) to study the effect of sulfides structure on the electrochemical oxidation rates. The methods of X-ray, optical and electronic microscopy are used to analyze the phase composition, and the methods of voltamperometry and chronoamperometry are used to study the laws of electrochemical oxidation. Slow cooling of the samples with sulfide phase (Cu_1,96S, Ni₃S₂) leads to crystallization of the metal (Ni, Cu). High cooling rate leads to crystallization of non-equilibrium phases, increasing of proportion of the sulfide phase and decreasing of metallic component up to complete disappearance. It is shown that electrochemical oxidation of copper and nickel sulfides proceeds stepwise: Me₂S Me_2-XS Me_1+XS MeS Me²⁺ + S. Experiments have revealed the rates of electrochemical oxidation of granular sulfides that exceed the rates established for the slowly cooled samples. The rates of the electrochemical oxidation of Ni₃S₂ at potential of 1500 mV are 8.810^-8 g/sec·mm² (at v_cooling = 10 К/sec) and 1.310^-7 g/sec·mm² (at ν_cooling = 1000 К/sec). The rates of the electrochemical oxidation of Cu₂S at potential of 1000 mV are 2.810^-8 g/sec·mm² (at ν_cooling = 10 К/sec) and 4.310^-8 g/sec·mm² (at ν_cooling = 1000 К/sec). It is found that the forming of a passivation layer effects the rate of the electrochemical oxidation of copper sulfide and nickel sulfide. Non-equilibrium phase composition and refinement provide greater reactivity of sulfides in the conditions of anodic polarization. The oxidation and passivation of metallic phase along with sulfide phases proceed from the surface of Me₂S Me alloys. As for the samples crystallized at 1000 K/sec only anodic oxidation of sulfides occurs due to a lack of metallic phase. The compositions of passivation films and potentials providing the extraction of sulfur in the elemental state from the sulfides crystallized at high rates were determined.

Abstract: The present work attempts to expose a method to increase the lines capacity. The problem to treat concerns the existing minimum number of halts ''Stops'' to reposition in order to obtain the optimum transport capacity. This applied method to a narrow way in the process of normalization allows to add to the gain capacity induces by normalization a surplus of flow. The repositioning of the halts is a correction at lower cost having for objective to differ in time the heavy investments to modernize and standardize completely a narrow-gauge line. Throughout the text the term halt ''stop'' means any establishment or equipment ensuring the cantonment on one line.

Abstract: Undoped WO₃ and WO₃ nanoparticles doped with 0.251.0 wt.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) [. Tungsten (VI) ethoxide 5% w/v in ethanol 99.8% and platinum (II) acetylacetonate were used as W and Pt precursors respectively dissolved in ethanol. The undoped WO₃ and Pt-doped WO₃ nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The BET surface area (SSA_BET) of the nanoparticles was measured by nitrogen adsorption. From BET measurement, SSA_BET increased and d_BET decreased with increasing Pt concentration from 0 to 1.0 wt.%. The morphology and accurate size of the primary particles were further investigated by high-resolution transmission electron microscopy (HRTEM). The crystallite size of undoped WO₃ spherical was found to be ranging from 520 nm and the crystallite sizes of 0.251.0 wt.% Pt-doped WO₃ spherical particles were found to be in the range of 520 nm.

Abstract: Submerged arc welding (SAW) is a high quality, high deposition rate welding process commonly used to join plates of higher thickness in load bearing components. This process of arc welding provides a purer and cleaner high volume weldment that has relatively a higher material deposition rate compared to the traditional welding methods. A common issue in the application of SAW process raises a concern about the uncertainties involved with the heat affected zone (HAZ) in and around the weldment. The most intriguing issue is about HAZ softening that imparts some uncertainties in the welded quality. It increases the probability of fatigue failures at the weakest zones caused by the heating and cooling cycle of the weld zone. An attempt has been made in this paper to assess the heat affected zone of submerged arc welding of structural steel plates through the analysis of the grain structure by means of digital image processing techniques.