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By M. A. Neri

A lead-free solder alloy Sn-57.5Bi-0.5Ag has been developed by mechanical alloying and foundry processes, and has great potential as a lead-free solder system, to low temperature applications. The mechanical alloying powders show a microstructure different to the microstructure obtained by the foundry process for the same alloy. Its melting point of 142°C is slightly higher than that of eutectic tin- bismuth solder. Examination of the microstructure revealed that eutectic microstructure is refined by the mechanical alloying process Ag additions. The lamellar structure of tin-bismuth gradually disappeared with the process of mechanical alloying, while intermetallic compounds AgaSn phase was formed. The Cu-Sn intermetallic compound layer formed at solder-copper interface is the Cu6Sn5 phase. Keywords: Lead-free solder, Microstructure. Mechanical alloying

Jan 1, 2003

By Dirk Bergmann

During the spray forming process, a continuous molten metal stream is atomized by impinging high speed inert gas jets. In the generated spray cone, the resulting metal droplets are rapidly cooled by the huge temperature difference to the surrounding gas phase and thereby partly solidified during flight. After a certain flight and residence time inside the spray cone, the droplets impinge onto the solid substrate and form the product (deposit) by compaction. Material properties of this preform strongly depend on several process parameters and especially on the thermal and kinetic state of the deposited droplets at the point of impingement. Smaller droplets may cool very fast due to their low mass and impinge onto the product in a completely solidified state as solid metal powder particles. Larger droplets with big mass contain a higher amount of thermal energy and impact during the state of phase change or still as completely liquid. It is obvious, that a certain amount of liquid content in the droplets is needed for forming a homogeneous deposit. Therefore, the thermal history of metal droplets during flight in the spray cone is of great importance for overall process modelling and control. Modelling the effects of the impinging droplet mass on the formation and heat balance of the deposit, the thermal conditions of the droplet stream need to be temporary and spatially averaged at different locations. Averaging may be achieved in different ways, giving alternative results. A first method is averaging over the droplets total enthalpy which consists of the thermal content and the remaining latent heat of fusion within the droplets. A second method may yield the average over the heat content and the solid fraction separately. Results of these two methods depend on the application and the kind of information which one wants to achieve and show some deviations, which will be discussed in terms of consolidation and energy conservation of the deposit.

Jan 1, 1999

By Nils Eivind Kamfjord, Roar Jensen, Ingeborg Solheim

"SINTEF has carried out several pilot scale silicon process experiments in the past, but always with an open off gas system. In order to test the possibilities in running a semi closed furnace operation, a new off gas hood has been designed and tested. The off gas hood is designed to collect all off gases to gain insight into the phase compositions in the off gas and at the same time have the opportunity to monitor and maintain the charging/stoking of the furnace. The furnace hood has regulation and control of the air inlet into the combustion zone in two different heights. The off gas temperature and composition was continuously monitored and analyzed during the experiment. In order to expand the knowledge on NOx- formation in silicon metal production, such information is vital.IntroductionBecause of the negative environmental impact, the attention towards all kinds of NOX emissions increases in Norway. The authorities’ demand towards better surveillance and control of emissions increases as well.Earlier and new industrial measurements in FeSi- and Si-metal furnaces reveal quite high NOX-emission. The measurements also show that the NOX formation (mainly as thermal NOX) is distinct connected to the formation of dust (SiO?SiO2) in the combustion chamber above the furnace surface, when the temperature is high and the access to N2/O2 is good. This means that stoking, charging and temperature straight above the furnace surface is important factors for the NOX formation."

Jan 1, 2012

A new technology for the treatment of copper nickel-containing concentrate after high-grade matte flotation to blister copper with the production of liquid silicate slags in a vertical autogenous unit with upper oxygen blow has been considered. The copper and nickel behavior in the process of sulphide copper concentrate interaction with silicate melt containing oxide copper has been studied. The general mechanisms of such interaction are found.

Jan 1, 2003

By Tarek M. Hatem, Salah M. Bedair, Khaled H. Khafagy

Our understanding for intrinsic stresses and defects evolution in photovoltaic devices has became an essential part of new developments. In particular, Multi-Junction Photovoltaic (MJ-PV) modules depend on multi-layer structures that may suffer high dislocation-densities as a result of high lattice and thermal expansion coefficient mismatch. These defects limit the performance, reliability, and lifetime of PV devices. In the current study, a three-dimensional multiple-slip crystal-plasticity model and specialized finite-element formulations are used to investigate InGaN growth on Si substrates. The formulation is based on accounting for thermal and intrinsic stresses as a result of different processing conditions and microstructures. Furthermore, the formulation was used to investigate a recently developed technique, Embedded Void Approach (EVA), which can be used to address both the high density of defects and the cracking/bowing of InGaN growth on Si. The current work lays the groundwork for more extensive use of silicon in MJ-PV devices.

Mar 1, 2018

By Shoji Taniguchi, Lifeng Zhang, Kaike Cai

"In the present paper, based on the two-phase (Eulerian-Eulerian) model, the 3D fluid flows in gas-stirred systems, i.e., air-stirred water vessel and argon-stirred liquid steel ladle, are simulated. In the Eulerian-Eulerian two-phase model, gas and liquid are considered to be two different continuous fields. The phases are assumed to share space in proportion to their volume fractions. The exchange between the phases is represented by source terms in conversation equations. Turbulence simulated by the k- e model is assumed to be the property of the liquid phase. The following effects of mathematical treatments and operational factors on the fluid flow are discussed, such as interphase drag force, turbulent model, the size of bubble, and gas injection mode.Some interesting results are derived. Except the interphase drag force, the interphase lift force should be taken into accounted in order to exactly simulate the fluid flow in gas-stirred systems. Suitable turbulent model and drag coefficient have effect on the mathematical simulation. Injecting small bubbles can realize a well mixing flow condition. The distance between the two gas-injection nozzles has effect on the fluid flow."

Jan 1, 2000

By L. Escudero-Castejon, S. Sanchez-Segado, A. Jha, Y. Hara, S. Parirenyatwa

In a world where declining ore grades are increasingly common, it has become necessary to process low-grade feedstock. Carbothermic reduction in the presence of alkali (Na2CO3) has been adapted to beneficiate waste that contains titaniferous minerals (TiO2 ca. 12 wt%), in order to recover valuable constituents such as TiO2, Fe and V2O5. The waste from vanadium metal processing has environmental legacy as it leaves nearly 1 wt% V2O5 process waste, which is environmentally problematic due to V5+ ions in contact with water and soil. This investigation focuses on the kinetics and mechanism for alkali reduction of mineral waste bearing 10–12 wt% TiO2, which we studied in the 1073–1323 K range. The thermogravimetric analysis (TGA) technique was used to record weight loss data. Two distinct regimes demonstrated mixed-control kinetics: (1) at low temperatures the activation energy was found to be 199 kJ mol−1, which corresponds to the outward diffusion of O2− ions; and (2) at high temperatures the calculated value was 130 kJ mol−1, which is consistent with the activation energy for the outward diffusion of Fe2+ ions. The metallic iron, sodium titanate and sodium aluminosilicate phases that formed were characterised using X-ray powder diffraction (XPRD) and scanning electron microscopy (SEM) techniques, and their significance for metal recovery is explained.

Mar 1, 2017

By Jin-tao Gao

In order to recover Ti resource from titanium bearing blast furnace slag, a new technology to separate perovskite phase from CaO-TiO2-SiO2-Al2O3-MgO system by supergravity is researched. In the condition of gravity coefficient of 750g, treatment temperature of 1305°C and time of 20min, the significant layers appear in samples which are obtained by means of centrifugal treatment. Along the direction of the supergravity, the volume fraction of perovskite phase increases gradually, and the equivalent diameters of perovskite phase crystals increases with the area approaching to the bottom of the sample. It is indicated that TiO2 is enriched in the bottom of sample as concentrate with a recovery ratio of 74.05% by supergravity treatment.

Jan 1, 2014

By S. Niyomwas, R. G. Reddy

"A mathematical model was developed to describe the plasma gas and particle dynamics and conversion yields. The velocity and temperature fields in the plasma were calculated by solving 1 the Navier-Stokes equations and the thermal energy balance equations. Conservation equations for the system species consider the multi-component diffusion and chemical reactions. Through the application of this model, temperature distribution, flow fields, and production rates were computed. The model was used to study the thermal decomposition of ilmenite in the non-transferred arc plasma reactor. The computed production rates of TiN from ilmenite using nitrogen and methane gas mixtures, are in the range of 5 to 100 x 104 kg/m3/s at 2500 KIntroductionThe widespread interest in thermal plasma processing has stimulated a great deal of research effort into the various aspects of this process, including plasma' spraying, thermal plasma chemical vapor deposition, plasma synthesis of fine powders, thermal plasma decomposition, plasma melting, and plasma extractive metallurgy.In the plasma synthesis of fine powders, the earlier experimental and theoretical studies aimed at predicting the final products1-5. Then it was followed by more recent investigation concerning the profile of plasma gas velocity, plasma temperature and concentration. In this regard, useful plasma processing models have been reported by numerous investigation6 -11 which were increased by both theoretical analysis and measurement.As a result of this work a reasonable plasma-processing model is proposed. It is to be noted that all the thermal analysis that has been made neglected the fluid -flow effects. Also, in the analysis aimed at the quantitative description of the fluid-flow field, the effect of heat transfer was not taken into account."

Jan 1, 2000

By Hüseyin Aydin

TWIP (Twinning-Induced Plasticity) steels have exceptionally good combinations of strength, ductility and damage tolerance which satisfy the recent requirements of automotive industries. Firstly, TWIP has the most beneficial effect on the work-hardening. It is believed that deformation twins increase the work-hardening rate by acting as obstacles against gliding dislocations. Moreover, TWIP steels have low to intermediate stacking fault energy and hence undergo extensive mechanical twinning during deformation, which in turn leads a good combination of both strength and ductility. To explain the mechanical characteristics and the mechanical behavior of the TWIP steels, we have been made some investigations and experiments that show the effects of microalloying elements and deformation mechanisms. In this study, three different compositions of TWIP steels have been produced. The microstructure and mechanical properties are characterized by using optical, electron microscopy and mechanical tests.

Jan 1, 2009

By Masao Miyake, Eiichiro Matsubara, Tetsuji Hirato, Yasuhiro Awakura

"Zn-Cr alloy coating with around 15 wt% Cr has been found to have much higher chemical corrosion-resistance to steel than conventional zinc plating, while· its structure has not been clarified. The Zn-Cr alloy plating is performed at high current densities around 1 A cm-2 and for 10 to 20 sec using acidic aqueous sulfate solutions with some additives in the iron-steel industry. Due to the high current densities, it seems reasonable to consider that the Zn-Cr alloy plating proceeds under an unsteady-state condition and that the resulting coatings have a non-equilibrium phase and have a structure change in the .direction of thickness. In this research, the crystal structure of the Zn-Cr alloy coating electrodeposited at high current densities and change of the structure in the direction of thickness were examined by X-ray diffraction. The coatings containing under 20 and 35-40 wt% Cr had hcp and bee structure, respectively, while the coatings containing 20-35 wt% Cr comprised two phases with the hcp and the bee structure. The structure of the coating varied in the direction of thickness; both the hcp and bcc phases coexisted in the vicinity of the substrate, while the hcp phase became predominant with increasing distance from the substrate.IntroductionRecently it has been reported that Zn-Cr alloy coating containing around 15 wt% Cr has much higher corrosion-resistance to steel than conventional zinc plating.1-3) The corrosion-resistanc·e of Zn-Cr alloy plated steel sheet with a plating amount of 20 g m·2 is, for example, superior to that of Zn plated steel with a plating amount in the range 60 to 90 g m·2 , which is widely used for automotive bodies today.4l The Zn-Cr alloy plating is obtained by electrodeposition at current densities over 0.5 A cm·2 from a sulfate solution containing zinc and trivalent chromium ions and some additives.5•6) The deposition current densities mentioned above are much higher than those for usual electroplating processes, e.g., Zn, Cu and Ni plating, carried out about 0.05 A cm·2 • Therefore, the time required for plating is very short; around 10-20 sec. Due to the high current densities, it seems reasonable to consider that the· Zn-Cr alloy plating proceeds under an unsteady-state condition and that the resulting coatings do not have a phase expected from equilibrium diagrams; no phase diagram of the Zn-Cr system with a full composition range has been available. 7). In other words, the alloy phase plated would be a non-equilibrium phase with unknown structures."

Jan 1, 2000

By F. H. Froes, O. N. Senkov, N. Srisukhumbowornchai

"Mechanical alloying (MA) and thermohydrogen processing (THP) approaches were used to synthesize amorphous or nanocrystalline powders of the titanium-aluminide-based alloys and composites. Fully dense samples with nanocrystalline and bimodal structures were produced from these powders by hot isostatic pressing. The stability of the microstructures during continuous heating at high temperatures was studied. Characterization techniques including X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, and differential thermal analysis were used in this work.IntroductionAs performance demands increase, so do the demands for enhanced mechanical property combinations at reduced overall weight; and reduced weight can most efficiently be realized by the use of low-density metals with high specific strength, such as titanium alloys and titanium-aluminum intermetallics [l]. The TiAl-based alloys are attractive for high temperature applications, however, they exhibit poor ambient temperature ductility and fracture toughness [2-4]. Incremental improvements can be obtained using ingot metallurgy processing [1,2] but more substantial developments require ""far from equilibrium"" (FFE) synthesis [5-8] which allows development of novel constitutional and microstructural effects, leading to enhanced physical and mechanical properties. Improved ductility of titanium aluminide intermetallics can be achieved by disordering, grain refinement and deoxidation of the matrix, while good elevated temperature properties are achieved due to a dispersion of fine, thermodynamically stable, second phase particles.The approaches for producing nanocrystalline and amorphous TiAl-based alloys and composites used in this work included FFE powder metallurgy techniques such as rapid solidification, mechanical alloying and thermohydrogen processing. The rapid solidification (RS) technique allows extension of solubility limits, production of novel phases, and much more refined microstructures (down to nanostructure or even amorphous range) than is possible using the ingot metallurgy technique [9]. Mechanical alloying (MA) is a process in which heavy working of powder particles results in intimate alloying by repeated deformation, fracturing and welding. This process can produce greater departure from FFE than RS, leading to greater refinement effects; and additionally allows production of a dispersion of second phase particles [10]. Thermohydrogen processing involves hydrogen as a temporary alloying element in titanium to facilitate processes, refine microstructure, and improve final mechanical properties [11]; it was used in the present work to improve MA process. The combination of these three processes was expected to control the final microstructure even better than either process used alone."

Jan 1, 1998

By T. Shoji

"The human history is characterized by social development based on mineral and energy resources, and many conflicts to take the resources by power. This is shown by not only world wars but also many local conflicts as well as international supremacy.IntroductionThe world population after B. C. 10000, which is summarized in several papers, is approximated by four straight lines on a semilogarithmic diagram as shown in Figure 1 [l]. The annual rates of increasing are 0.0041, 0.071, 0.53, and 1.85 % from the old and young periods. The boundaries among four periods are approximately B. C. 4600, AD. 1670, and 1930. The start of the second period seems to correspond to the beginning of agriculture and cattle breeding. Precisely speaking, the usage of natural energy resources such as woods and domestic animals already began, but is inferred to have become common after the age. The third and fourth periods are characterized by the common usage of coal and oil, respectivety. Not only energy resources but also mineral resources including gold, copper, iron and others are also important for the human history.Mineral and energy resources have supported the development of the .human civilization, and have caused many conflicts because of this reason. Every day newspapers report conflicts, such as Chechnya, East Timor and Ache. We can easily point out the facts that the conflicts closely relate to mineral and energy resources. Groznyj, Capital of Chechnya, is located on the western margin of Caspian oil field. Many mineral deposits occur in Kavkaz Mountains running south of Chechnya. Subsea oil fields occur in Timor Gap located between East Timor and Australia. Ache is also one of oil fields in Indonesia. It is very difficult to state present conflicts independently of a political view of point. For this reason let us try to historically review the relation between mineral and energy resources and international domination and conflicts [2] based on many papers [3]."

Jan 1, 2000

By Shekhar Bhansali, Shyam Aravamudhan

"This paper reports on the design and simulation results of a silicon bulk-micromachined diaphragm-type piezoresistive pressure sensor capable of operating linearly over a wide dynamic range (0-1000 meters of water). The piezoresistor elements of the sensor are arranged in a wheat stone bridge configuration to achieve a higher output response. Simulation results (output voltage and sensitivity analysis) obtained using coupled MemPZR-MemMech module of the CoventorWare2003 Finite Element tool are presented. The effect of diaphragm size, diaphragm thickness and thickness of the piezos on output sensitivity were analyzed and optimized to get a linear response over the wide dynamic range.IntroductionThe physical and biological processes in the ocean are critically influenced by ocean parameters (pressure, salinity and temperature). Thus there is a need to develop inexpensive and reliable sensors to continuously measure large volumes of sea-space over long time spans. A key component in any such system will be a pressure/depth sensor. This sensor is routinely employed in marine applications such as wave and tide gauges, tsunami detection, platform leveling etc. More significantly, pressure measurement is needed for depth determination. Depth sensors are vital for remote operated vehicles (ROVs), profiling instruments and towed arrays.Several techniques have been routinely used in the past to measure pressure in the marine environment [1-3]. In general, the pressure sensor design is based on a flexible membrane as the spring element for the sensing pressure [4]. The deflection of the membrane, induced by the applied pressure, is converted into an electrical output through a component that is sensitive to diaphragm deflection (capacitive coupling) or associated stresses (piezoresistors, strain gauges). The temperature compensated pressure measurement can be readily converted to depth using"

Jan 1, 2004

By Jie Li, Shu Yang, Zhongliang Tian, Xun Hu, Yanqing Lai

The purity of the electrolyte has an important influence on the content of the impurities in electrodeposited silicon. In this paper, effects of electrolysis temperature, current density and the time on the concentrations of two important impurities: phosphorus and iron in the electrolyte were investigated during the purification of Na3AlF6-10%K2SiF6-AlF3 melt. It was observed that the concentrations of P and Fe in the electrolyte decreased with the electrolysis temperature, current density and the electrolysis time increasing. X-ray fluorescence (XRF) of the electrolyte shows that the concentrations of P and Fe decrease from 4.2ppmw to 1.3ppmw and 204.0ppmw to 42.6ppmw, respectively. The removal rates of P and Fe are 69.08% and 79.12% when the electrolysis was performed for the duration of 3 hours and at a current density of 20mA·cm-2 while the operating temperature was 1225K.

Jan 1, 2015

By R. G. Robins

The effective removal of arsenic(V) from process streams and waste waters by precipitation with excess iron(II1) is sometimes attributed to the formation of basic ferric arsenates. The authors have investigated this system extensively using a variety of techniques and conclude that the solid phase produced is iron(II1) oxyhydroxide (ferrihydrite) with arsenic(V) adsorptively bound to the 2-3 nm particles.

Jan 1, 1992

By Shigeru Ueda, Shin-ya Kitamura, Shohei Koizumi, Xu Gao

Steelmaking slag was confirmed to be a useful fertilizer for paddy growth as it efficiently supplies Ca and Si to soil water. In addition, supplement of Fe from slag fertilizer has been expected to suppress the H2S generation in paddy soil, especially for the degraded paddy soil. However, on the basis of our previous research, the Fe dissolution ability changed with slag brands, and even some brands could dissolve Fe under paddy soil pH, the supplying ability were not high. To improve Fe dissolution, we found that among various kinds of Fe-rich mineralogical phases in slag, the CaO–SiO2–FeO glassy phase showed highest water solubility of Fe. Because the CaO–SiO2–FeO glassy phase was a quenched molten phase, its dissolution behavior may depend on chemical composition, and this is important for controlling slag composition to produce fertilizer which can easily release Fe. Therefore, in this research, the CaO–SiO2–FeO glassy phase of various CaO/SiO2 ratio, Fe2+/T–Fe ratios, and FeO contents were synthesized, and the dissolution behaviors of Fe as well as other cations from these synthetic glassy phases into an aqueous solution at pH of 5 were investigated. The result showed that the dissolution ratio of Fe increased significantly by increasing Fe2+/T–Fe ratio. An increase in FeO content of glassy phase also increased the dissolution of Fe. In addition, the Fe dissolution ratio showed a local maximum with increasing CaO/SiO2 ratio.

Mar 1, 2017

By Jiangwei Shen, Cong Wang, Haibin Zuo

The research on the formation of Silico-Ferrite of Calcium and Aluminium (SFCA) in the process of cooling and solidification is rarely reported. The crystallization process was observed by using scanning electron microscopy (SEM) and optical microscope in this paper. The effect of different cooling system on the microstructure and phase composition of the sinters was investigated to obtain the appropriate cooling rate to improve the metallurgical properties of sinters. The experimental results show that the crystallization of calcium ferrite is getting better when the cooling rate is decreased from water quenching to cooling in the air. There are a large number of hematite phases with interconnected crystal structure in the sample cooled in the air. In the case of the compressive strength, it was determined by the mineral composition and pore structure, higher SFCA and hematite contents in sinter cooling in the air lead to a higher strength. Glass phase in the water quenching sinter was the major reason for the lowest strength. High porosity contributes to a decrease in compressive strength for the sinter cooling in the furnace. Therefore the air cooling was the appropriate cooling rate to achieve high quality sinter under this experimental condition.

Jan 1, 2016

By A. V. Tarasov, V. M. Paretsky

"The knowledge of the true phase composition of the liquid slag is a very important problem, mastering of which grants the possibilities for the scientifically founded choosing of the decoppering method of the autogenous smelting slags. The investigation using different methods of the phase composition of the flash quenched autogenous copper melt's slags has shown, that the most effective method of the slags' decoppering during smelting with the white matte production is the flotation of the recrystallized slags. In this work the authors posed the problem to realize the slags quenching with the rates similar to those, which are used in the modem investigations devoted to the flash quenching of the ironcontaining alloys, with the subsequent study of the quenched samples using the Mossbauer spectroscopy methods in order to establish the connection between the liquid slag's structure and the metals losses with the slag."

Jan 1, 2000

By C. D. Mishra

The recycling potential for any gainful utilisation of the waste products is dictated by their quality, especially the chemical characterisation. The methods commonly used for the analysis of fly ash e.g. wet chemical, AAS, ICP-AES etc are time consuming. The paper describes a rapid XRF-based method for routine analysis of fly ash which involves preparation of local standards, optimisation of sample preparation technique and use of a simple PC-based software to account for interelement effects. The matrix corrected values are found to agree well with the wet chemical data.

Jan 1, 1992