Search Documents

By Chao Du, Xiaohui Ning, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

"TiCxOl-x solid solutions were synthesized by sintering a mixture of titanium carbide and titanium monoxide at 1600 °C. The corresponding structures and morphologies of the TiCxOl-x solid solutions were characterized by XRD and SEM. A series of tests has been performed on the electrochemical dissolution behavior of TiCxOl-x solid solutions in NaCl-KCl molten salt. The influences of synthesis time and electrokinetic parameters on the anodic dissolution behavior were also investigated. The results showed that TiCxOl-x solid solutions can dissolve as Tin+ into alkali chloride melt. Titanium ion species dissolved from TiCxOl-x solid solutions changes between Ti2+ and Ti3+ depending on the applied potential. The tail gas on the anode was monitored by a mass spectrometer. It was found the synthesis time significantly affects the components of the anodic gas.IntroductionTitanium and titanium alloys have been desired greatly because of their many uses. The critical factor that restricts the range of uses for Ti is its high cost of extraction. The primary titanium metal, sponge titanium, is still produced industrially worldwide by a process invented by Dr. Kroll in the 1940s[1] •Since the early 1970s, the research focus of the titanium industry has been directed towards developing a continuous process to produce high purity titanium at low cost. [2-10] Of the many alternative methods that have previously been investigated, the electrolytic process has been considered a promising method for titanium metallurgy [4-10]. Recently, several electrolysis and related methods such as the PFC-Cambridge process[11-15], calciothermic reduction[16-18], USTB [19,20] and MER[21] process were extensively investigated.The USTB process is a new approach where the pure titanium can be directly obtained by the electrolysis with an anode of titanium oxycarbide in molten salts[19, 20]. The titanium oxycarbide was produced by carbothermal reduction of titanium dioxide under vacuum at a temperature"

Jan 1, 2011

By Pengfu Tan

A thermodynamic model of KIVCET lead smelting process has been developed. The model has the capability to predict the distribution behaviors of Pb, Zn, Fe, S, O, As, and heat balance in KIVCET direct lead smelting furnace. The compositions of lead bullion, matte, slag and gaseous phases, and heat balance are calculated. The effect of the ratio between oxygen and feed on the chemistry of the smelt and heat balance of the coke checker has been simulated and discussed. The thermodynamic model also helps to understand the tapping issue of the lead bullion. In this paper, some applications of this model in the industry have been presented.

Jan 1, 2006

By T. -M. Guo, M. J. Braun

"This paper presents an experimental and numerical study of melt flow near the solid-liquid interface and its effect on the interface curvature in a horizontal unidirectional solidification system with succinonitrile. Melt flow is introduced by increasing the ampoule channel thickness. Visualization techniques are employed to observe the flow field and the solid-liquid interface curvature. A numerical model is also developed to simulate the heat transfer, melt flow and phase change in the system. Quantitative information on the flow and temperature fields is generated. A good agreement is achieved between the experimental observations and model predictions. The results could be used for the study of the effect of the melt flow on interface morphology during solidification.IntroductionClassic unidirectional solidification experiments of transparent alloys are conducted with thin film samples sandwiched between two glass slides to investigate the development of interface morphology during solidification [1]. Samples with small channel thickness are usually used to suppress any melt flow due to natural convection and solidification in the channel would then be in the diffusive regime so that the solidification theory can be significantly simplified [2, 3]. Effects of melt flow, in particular due to natural convection, on solidification have also been studied extensively in those systems with large geometrical dimensions [4-6]. These studies indicate a strong effect of the melt flow on interface curvature during solidification [5, 6]. Only limited efforts were made to address the effect of the melt flow on interface morphology in horizontal unidirectional solidification, in particular for the cases when the channel thickness is not thin enough to suppress completely the natural convection [7]."

Jan 1, 2004

By G. M. Bond

Reduction of the emissions of greenhouse gases, such as CO,, is currently the subject of extensive research. A novel strategy is put forward here, based on a biomimetic approach providing accelerated deposition into carbonate form for long-term sequestration. It offers the advantages of a process that: does not require concentration of CO, from flue gases; could potentially be used in an on-site scrubber to provide a plant-by-plant solution to reducing CO, emissions; is an environmentally benign procss with an environmentally benign product; and is based on readily available, low-cost reagents (except perhaps the catalyst).

Jan 1, 1999

By Chao Zhang, Kexin Jiao, Yi Qian, Jianliang Zhang

Now low-grade iron ore were widely used. However, one prominent problem is that the content of trace elements is higher than that in high quality iron ore. For the requirement of the content of Mn, Cr, Ni, Cu, and Ti in hot-rolled steel sheet and strip, the upper limits of these elements in sinter will be studied in this paper. Using the activity model of aggregation of electronic phased slag composition, the distribution ratio of each element in converter is analyzed and the content of each element in hot metal is calculated. Furthermore, through the thermodynamics method, the distribution ratio of each element in BF is analyzed and the content of each element in raw material is calculated. The upper limits of Mn, Cr, Ni, Cu, and Ti in sinter can be determined by calculating, the values are as follows: Mn 0.767%; Cr 0.552%; Ni 0.055%; Cu 0.159%; Ti 0.108%.

Jan 1, 2015

By Shilai Yuan, Huimin Lu, Panpan Wang

A big andalusite ore bed was found in Dingxi District, Gansu, China. In this paper, the feasibility of producing solar grade silicon from aluminum-silicon alloys by carbothermal reduction of andalusite ore was studied. First, the carbothermal reduction experiments were conducted in a 100 kVA DC submerged arc furnace with reducing temperature 2000–2200 °C and reducing time 4 h, the hypereutectic aluminum-silicon alloys containing 50–55 mass% aluminum and 35–45 mass% silicon were obtained; then the investigation on solidification of the hypereutectic Al-Si melts under the temperature gradient as an intensified separation silicon way was carried out. According to previous investigation, the optimized technical process for solar grade silicon and eutectic Al-Si alloy from andalusite ore was proposed.

Mar 1, 2017

By Dave Tahija

"Many investigations are being performed with the goal of removing carbon dioxide from the atmosphere and permanently storing it in geologically stable settings. At the same time, carbon dioxide in the form of dissolved carbonate is steadily accumulating in the world's oceans. Both carbon dioxide sequestration and oceanic accumulation are constrained by the aqueous thermodynamics of the carbonate system. These constraints are illustrated using the STABCAL computer model to generate potential-pH and aqueous distribution diagrams of seawater in contact with various pressures of carbon dioxide gas. STABCAL diagrams and titration simulations are also used to model some potentially useful cation-carbonate sequestrationsystems.IntroductionAtmospheric carbon dioxide concentrations have risen dramatically in the past couple of centuries and are rising still, primarily as a result of human activities, especially the burning of fossil fuels. Increased atmospheric carbon dioxide concentrations have been implicated as a main cause of global warming but have other effects as well.Rising levels of atmospheric carbon dioxide result in increased concentrations of dissolved carbonate complexes in water, including the oceans. These dissolved carbonates interact with other dissolved substances, altering overall seawater chemistry, most noticeably causing lowered pH levels.Some of these chemical changes are observed directly, for instance the general drop in oceanic pH, [1], while others can be inferred and predicted using thermodynamic modeling. The chemistry of dissolved carbonate in seawater is not especially intricate, as such chemical systems go, but neither is it simple enough to be worked out on the back of an envelope. Interactions between the several simple carbonate species and all the major dissolved cations in seawater should be considered, as well as the effects of competing anions, especially chloride and sulphate, since they are much more abundant than carbonate in seawater."

Jan 1, 2011

By Ilie Butnariu

Steel manufacture in VOD procedure needs a very attentive correlation and pursuit of the technological stages ,on the background of keeping the influence factors within best performances zones. For a better co-ordination of the main stages specific to this process ,this work presents a detailed study of the optimization possibilities for each stages ,beginning with the furnace charging ,going on with the pre-aftinage and aftinage stages in the electrical furnace and then with the refinement stages in the VOD installation. One has intended the effective emphasis of the main influence factors with global implications on the process and especially on the purity and quality of the stainless steel ,Among the main novelties proposed by this work , we can emphasize the following: - a computer assisted charging method ,with the possibility of using a large scale of wastage, also respecting the density proportions of the components of the charges; - the advanced recuperation of the elements of the charge by reducing the combustion of the valuable elements ; - the optimization of the oxygen blast conditions and of the aftinage stage ,by establishing some calculations concerning critical carbon content , that requires the oxidation to be continued very carefully; - the simulation of the thermic and chemical parameters by modeling the alloying process of the stainless steel in the case of some large amounts of additions.

Jan 1, 1994

By A. M. Ramalho

In the synthesis and sintering processes to obtain superhard materials, such as diamond and cubic boron nitride, deformable ceramic capsule is used as gasket to transmit and support the required high pressures and high temperatures, HPHT. The ceramics materials for these capsules should have special physics and chemical characteristics such as refractoriness, shear strength and compressibility. In this work, Bridgman?s anvil made of hard metal or speed steel was used to characterize some ceramics materials in terms of their maximum compressible thickness. Tests were also performed with different resin polymers used as binding mixture with ceramics powder. Chemical analyses and investigations through scanning electronic microscopic (SEM), X-ray and real tests for the synthesis of diamond were also performed. The results showed that local Brazilian calcite can be successfully used in the manufacture of HPHT gaskets.

Jan 1, 2006

By Carlos Carnurri

A characterization of mechanical properties of fire refined copper has been done in order to link ductility with oxygen content. The results show four different copper mechanical behaviours as temperature increases, where the oxygen con- tent, as Cu20 segregated, has a deleterious effect on ductility. It is concluded that until 500 ppm oxygen content, the fire refined copper could be rolled without remelting for deoxidation. Also a subsequent cold rolling could be done without intermediate annealing.

Jan 1, 1994

By K. Osseo-Asare

The molecular structural and solution chemical characteristics that underlie the surface activity of solvent extraction reagents are highlighted, with particular emphasis on the tendency towards reverse micelle and microemulsion formation. The physicochemical factors that lead to microemulsion-enhanced solvent extraction with chelating extractants are elucidated Membrane-based contactor systems are described which are uniquely suited for enhanced solvent extraction with microemulsions. The possibility of combining solvent extraction with microemulsion-mediated materials synthesis is discussed.

Jan 1, 1996

By Francois Barthelat, Sam Goroshin, David Frost, Alexander Cappozi, Atefeh Nabavi

"In this study, a novel chromium–chromium sulfide cermet was produced by self-propagating high-temperature synthesis (SHS). Conventional techniques for manufacturing metal sulfides are complex, environmentally harmful, and not suitable for producing complex-shape articles. To overcome these disadvantages, a new method for the preparation of the metal-sulfur precursor charge is proposed, which can be described as reactive casting. The first cermet samples produced with the SHS process were found to be very porous, brittle, and have low mechanical strength. The possible sources for the generation of porosity were identified and analyzed and the process for manufacturing the cermet was modified. By improving the manufacturing process, the porosity inside the produced cermets was reduced from 70% to 12%.IntroductionMetal sulfide composites are in high demand in the chemical, metallurgical, and electrical industries because of their valuable characteristics such as hardness, semi-conductivity, electroluminescence, infrared transparency and catalytic properties. Current manufacturing methods for metal sulfides usually involve one of two different principal methods, including a complex multistage wet chemical process involving the precipitation of the corresponding salts from an aqueous solution with hydrogen sulfide, or hot sintering of the respective elemental reactant powders in a resistive furnace in a high-pressure inert or hydrogen-sulfide atmosphere [1, 2]. These conventional methods for synthesizing ceramic metal composites are complex, extremely time and energy consuming, environmentally harmful, and rarely able to manufacture articles with complex shapes. Therefore, in order to overcome these disadvantages, self-propagating high-temperature synthesis (SHS) was considered as an alternative method that offers significant improvements over the traditional cermet manufacturing methods [3]. SHS, which is a relatively new and attractive method for producing a wide range of advanced materials, is based on the self-sustaining feature of the highly exothermic reactions of the reactants. The SHS process results in high product purity, since the high temperatures generatedin the reaction cause any impurities to volatilize [4, 5]. SHS has low energy consumption and doesn’t require an external energy source and complex equipment, and it is self-contained [1, 5]. Since combustion synthesis has low power requirements, it is one of the few methods of materials synthesis that is feasible in outer space. Also, the process has a low cost and is capable of directly synthesizing articles with the desired shape, size and structure [5, 6]. The chemical reactions associated with SHS are typically completed in a few seconds leading to the formation of the condensed product. The high reaction rates and relatively rapid cooling in SHS reactions can avoid undesirable grain growth in products which often occurs with the conventional sintering method [3, 5, 7]. The traditional method for sample preparation in the SHS technique is to compact the reactant mixture powders in a steel die by a press to a typical density of about 80% of the theoretical maximum value, before igniting the mixture [8]. This method requires a large compression force to increase the green density and to minimize any pores in the green compact. To overcome these disadvantages, a new method for the preparation of the precursor charge in metal-sulfur by SHS is proposed which can be described as melt casting of a reactive mixture, or reactive casting in short."

Jan 1, 2012

By Carvalho A. Felipe de

The search for environmentally friendly and cost-effective methods for gold extraction has been undertaken in order to provide alternatives to the use of cyanide leaching in the gold industry. Among such alternative reagents is the combination of chloride and hypochlorite ions due to their oxidation of metallic gold and its complexation. Therefore, the current work aims at investigating gold leaching from an oxidized material by means of a solution comprising calcium hypochlorite and sodium chlorite. The sample used in the current research contained 66.1% Fe2O3, 20.4%SiO2, and 35.7 g/t of Au. In addition, XRD and SEM-EDS analysis revealed iron oxide, quartz and muscovite as the main crystalline phases in the sample. For comparison purposes, cyanidation of the oxidized material resulted in 90% gold extraction in 24 h. The reference conditions for the leaching tests with the chlorite-hypochlorite system were: particle size −37 μm, solid/liquid ratio of 10% (w/v), 10 g/L NaCl, 10 g/L Ca (OCl)2, pH 5–6, 3 h of leaching. The effects of the: (i) Ca(OCl)2 concentration, (ii) NaCl concentration, (iii) pHrange and (iv) the effect of pulp density in the extraction of gold were assessed. In addition, the stability of the hypochlorite solutions (OCl−) was investigated. The ideal concentrations of Ca(OCl)2 and NaCl were determined as 25 g/L and 15 g/L, respectively, whereas the optimal pH range was 4–6. Under these conditions, the final gold extraction reached approximately 84%. By varying the solids content of the pulp (10%, 20% and 30%), it was observed that the lower solids value resulted in greater gold extraction (84%). The degradation of the hypochlorite solution and the possible catalytic effect of the presence of the solid were evidenced. To sumup, in the experiment, high gold extractions were achieved in shorter periods of time (3 h), as compared to the cyanidation of the same sample. On the other hand, itwas necessary to use significant amounts of the reagent due to hypochlorite instability at the pH conditions recommended for high gold extractions.

By Wolfgang Steffes-Tun

Pyrite ore concentrate from the Meggen mine (FRG) , which contains about 0 300 400 ppm thallium, is roasted in a fluid bed furnace at 1000 -1100 C to form sulfur dioxide and ash consisting mainly of hematite. Subsequently, the sulfur dioxide is separated from the ash or dust during several steps while cooling to about 250oC. The pyrite ash fractions show decreasing grain size down to 5 pm, a pH-decrease down to 2,4 and a marked enrichment of arsenic and thallium by a factor of 12. In the final fraction, the hot electroprecipitator dust of the dump (EGR), minute crystals of thallium-containing jarosite can be detected by analytical transmission electorn microscopy (TEM). Under oxidizing, acid conditions, jarosite may be a possible "reservoir mineral" for immobilizing thallium.

Jan 1, 1989

By Hideo Nakae, Hideki Yamaura, Toshiaki Kimura

"In 1968 J. N. Reding et al. suggested processes for fabricating composites. According to their patent, decompression atmosphere, which occurs during the reaction between magnesium and oxygen and/or nitrogen in the closed system, causes the spontaneous infiltration of melt into narrow spaces such as ceramic preforms. However, they did not report the proof of this phenomenon or the industrial manufacturing method. Therefore, this research measured the pressure change among SiC particles surrounding molten aluminum. As a result, the pressure reduction during the Mg reaction was identified. Moreover, the existence of Mg3N2, which improves the wettability between Al alloy melt and SiC particles on the interface, was observed on the surface of particles. Applying these two phenomena, a new process for the manufacturing of cast discontinuously reinforced aluminum composites (DRA) was developed. This new method is expected to produce DRA without additional pressure.IntroductionWith the increasing demands for light-weight materials in the automotive and aerospace industry in recent years, ceramic particulate reinforced aluminum matrix composites called DRA (Discontinuously Reinforced Aluminum Composite) have been receiving significant attention because of its lightness, superior abrasion resistance, high heat conductivity and low thermal expansion [1-3]. Consequently, DRA was considered for electronic parts such as heat-sinks or a base for power semiconductors, and began to be applied for automotive parts including brake drums, discs, cylinder liners, pistons and so on [4- 6]. However, high machining cost is one of the significant barriers to widespread use ofDRA. One solution to this problem is the adoption of cast DRA that can be produce to near-net shape, reducing machining cost."

Jan 1, 2000

By Y. Zhoa

The surface morphology of materials is of fundamental importance to many surface related applications, such as wetting, friction, reflection, drag, and adhesion. Various approaches for micro/nano patterning atop polymer surfaces have been proposed in recent years. However, a cost effective technique is still highly in demand. In this paper, we demonstrate a novel but rather simple and generic approach for surface micro/nano patterning using shape memory polymers (SMPs). Different types of novel patterns are realized and their 3-D surface features are quantitatively analyzed by a PLµ Confocal imaging profiler.

Jan 1, 2010

By Joel K. Witt

San Manuel Oxide operations of BHP Copper, located in Southeastern Arizona, operates a leach-solvent extraction/electrowinning (SXEW) facility that produces high quality cathode copper from low-grade oxide ores. Permanent heap leaching and in-situ leaching methods accomplish the dissolution of copper from the oxide ores. Open pit mining and heap leach construction took place from 1985 to 1995. Run-of-mine oxide ore from the pit was hauled to the heap dumps and leached by the soaking cure and continuous irrigation method. Solution application to the heaps still continues and acid soluble copper recovery has reached 86%. This paper presents and discusses the current operating practices and innovations applied to the leach facilities to maximize copper recovery from the heap leached residue. Factors such as irrigation methods, solution chemistry, sideslope treatment, post curing, lixiviant acid strength, and "rice paddies" irrigation, will be discussed. Heap leach solution control and sampling methodologies will be also presented.

Jan 1, 1999

By Hiroyuki T. Takeshita

Ca-Ni based alloys were investigated on structures, hydrogenation properties and the effect of additive elements on hydrogenation properties. CaNi, samples were decomposed to form a new hydride with a CsCl-type structure on the constituent metal atoms at high temperatures such as 673K in a hydrogen atmosphere. The candidate of the third element which was added to stabilize the original compound was investigated by using the Miedema's semi- empirical model and, as a result, Pd was chosen. The hydrogenation of CaPd was conducted with a Sieverts' type apparatus and the synthesis of Ca-Ni-Pd ternary alloys was performed by high frequency heating.

Jan 1, 2002

By Xuling Chen, Zhiyun Ji, Min Gan, Wenqi Li, Xiaohui Fan, Zhiyuan Yu

"Specularite and vanadium-titanomagnetite are difficult to granulate, and with the increase of their proportions, the permeability of sintering bed is deteriorated together with the combustion velocity of fuel for the shortage of air through the sintering bed, which can lower sintering speed and specific production capacity significantly. The biomass fuel has a higher combustion velocity than coke breeze, therefore the productivity of specularite and vanadium-titanomagnetite ore can be improved remarkably by replacing coke breeze partly with biomass fuel .The results showed that, when the proportion of biomass fuel replacing coke is 40%,the sintering speed and specific production capacity of 35% specularite were improved from 19.06mm/min, 1.33 t/(m2·h)to 21.45mm/min, 1.47 t/(m2·h),and that of 55% vanadium-titanomagnetite were improved from 17.23mm/min, 1.11 t/(m2·h)to 22.80mm/min, 1.44 t/(m2·h). As a conclusion, biomass fuel is effective to strengthen sintering of refractory iron ore.IntroductionThe iron and steel industry of our country has achieved significant development in the recent years. In 2010, the output of steel has reached to 0.627 billion tons. The increasing scale of iron and steel has led to rigorous domestic iron ore environment, and the reserves of hematite and magnetite that have superior sintering characteristics are on the decline with continually exploiting and utilizing [1]. Therefore, the RIO (refractory iron ores) SP (specularite) and VT (vanadium-titanomagnetite) have to be applied vastly. However, the quality of sinters can be deteriorated when utilizing RIO in high proportion due to their poor granulation and metallogenic performances [2, 3]. Generally, the ratio of SP is 3~5%,which should not exceed 10% in our country currently [4]. Though high rate of VT is adopted in PZH steel for a long time, the productivity is obviously low compared with normal sintering [5]."

Jan 1, 2012

By Mohamad Omarei, S. M. Sadrameli

"The aim of this research work was to produce biodiesel (fatty acid methyl esters, FAME) from canola oil using KOH loaded on y-Al203 support as a heterogeneous catalyst. Different parameters such as effects of the molar ratio of methanol to oil, catalyst amount and reaction time on the yield were investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used for characterization of the catalysts. A biodiesel yield of 86.67% was obtained under catalyst preparation and transesterification conditions of calcinations temperature of 773 K, 4 h of reaction time at 338 K, and using 3.5 wt% catalysts and molar ratio of methanol/oil of 15:1. The leaching of potassium species in the spent catalyst was observed.1. IntroductionBiodiesel is an eco-friendly and alternative energy source for diesel engines that can be synthesized by transesterfication of vegetable oil or animal fat with alcohols [1 ]. There are four principal approaches to the synthesis of biodiesel involving the transesterification of the triglycerides of the plant oils and animal fats: base catalysis [2], acid catalysis [3-5], employing supercritical alcohol conditions [6] and enzyme catalysis [7]. The commonly used homogeneous catalysts are NaOH, KOH and their alkoxides. Homogeneous alkali-catalyzed transesterification is much faster than acidcatalyzed transesterfication [8]. However, a large amount of water is required to transfer the catalysts from the organic phase to a water phase after the reaction. Therefore, it is considerably more costly to separate the catalyst from the produced solution [9]. These disadvantages could be removed by use of a heterogeneous catalyst [10]. The use of heterogeneous catalysts eliminates the neutralization step, hence it results much easier to separate from liquid products. Also, they can be designed to give a higher activity and selectivity and to have longer catalyst lifetimes [11]. A large number of different heterogeneous catalysts have been synthesized for biodiesel production. For example, calcined Mg-Al hydrotalcites [12], zeolite and metal catalysts [13], metal oxides such as calcium oxide (CaO) [14], magnesium oxide (MgO) [15], zirconium oxide (Zr02) [16], and supported catalysts [17] have been investigated as heterogeneous catalysts. CaO and MgO are most frequently used heterogeneous catalysts for biodiesel production [18]. In this present work, we aimed at developing an efficient catalyst for transesterification of canola oil. We have prepared KOH/ Al203 by impregnation and applied to determine the optimum conditions for biodiesel production. Three different variables including reaction time , alcohol to oil molar ratio and catalyst loading with may influence the quality of the produced biodiesel were optimized. Moreover, SEM (scan electron microscope), XRD (X-ray diffraction) and XRF were used for characterization of the catalysts."

Jan 1, 2012