Search Documents

By Hiroshi Tabuchi, Akihiko Takahashi

"High strength aluminum matrix composites were prepared and studied using as reinforcement newly developed nearly mono-dispersed a-alumina single crystal particles each of which has a regular polyhedral shape. The composites were formed by centrifugal casting using aluminum casting alloys (Al-Si and Al-Cu-Mg) as the matrices, followed by heat treatment. The volume fraction of the alumina particles was as high as 60%. The same matrix composites reinforced by conventional crushed fused alumina particles were similarly prepared as the reference. The bending strength and tensile strength of the Al-Cu-Mg matrix composites reinforced by the novel alumina particles of 10 µm in average diameter are as high as 1020 MPa and 560 MPa, respectively, which are higher than those of the conventional alumina composites. Furthermore, the bending strength of the novel alumina composites degraded less than that of the conventional alumina composites after thermal fatigue tests. The number of cracks in the matrix seemed to influence the thermal fatigue property because many cracks were observed in the conventional alumina composites, whereas only a few cracks were observed in the novel alumina composites. This was confirmed by SEM observation of the sample composites before and after the thermal fatigue tests.IntroductionAluminum matrix composites strengthened by dispersed reinforcements are of interest for various applications due to their improved properties, such as high specific strength and stiffness, wear resistance, etc .. A large number of investigations have been made concerning fabrication processes and properties of these composites. With regard to the fabrication processes, powder metallurgy has been well-known as a solid phase process, and recently many liquid phase processes such as a compocasting, a squeeze casting, the Lanxide process, and the Osprey process have been studied and developed.(1)"

Jan 1, 1998

By R. G. Reddy

To better understand the behavior of bacterial-mineral interfacial reactions, a thermodynamic model based on the- studies of bacteria adhesion on mineral surfaces has been evaluated. The bacteria adhesion to the mineral surface would be increased by l ' d1;1creasing the change in Gibbs free energy of adhesion and it would be reduced if the change in Gibbs free energy of adhesion of the system is increased. From the combination -of Young's equation and equation of state, the change in Gibbs free energy of adhesion -for bacterium-mineral system- was calculated. Influence of liquid surface tension, mineral surface tension on the change in Gibbs free energy of adhesion and consequently bacteria behavior on mineral systems- has been discussed.

Jan 1, 1991

By Oscar Jaime Restrepo, Juan Camilo Restrepo, Jorge Ivan Tóbon

Portland cement is obtained by a conventional synthesis process from a mixture of limestone and clay at high temperature (1450 °C). This work reports the possibility to obtain cement silicates via alternative methods like Solution Combustion Synthesis (SCS), which optimize both time and temperature, and the consequences to energy efficiency and mitigation of CO2 emissions. The production of one ton of cement emits between 0.62 and 0.97 tons of CO2 into the atmosphere. In this process the CO2 emissions are between 21 and 59%. The combustion methods are chemical redox processes in which, at high temperature, a self-sustaining and fast wave is generated from using chemical precursors and organic fuels.

Jan 1, 2016

By K. J. Martchek

"This introductory presentation will highlight recent efforts to quantify the positive value of recycling metals such as aluminum, magnesium, lead, zinc, nickel and copper in relation to the three pillars of ""sustainable development"" - environmental protection, economic development and improve social consequences.This presentation will provide an overview of life cycle assessment profiles increasingly being utilized by customers, regulators and environmental advocacy groups to holistically evaluate the environmental performance of materials and products. The environmental profiles of prodi.lcts containing recycled metal will be presented based on rules established by the International Organization for Standardization (ISO).Significant to the life cycle profile of metal products is recent confirmation. that recycling has the potential to reduce materials production energy consumption by 95% for aluminum, 80""/o for magnesium and lead, 75% for zinc, and 70% for copper. Furthermore, . ""metals are eminently and repeatedly recyclable, while maintaining all their properties (1 ). "" Their durability relative to many hydrocarbon based materials enhance .their life cycle performance. However, the persistence of metals when dispersed into our natural environmental makes recovery and recycling particularly important Overall, when considering life cycle effects, recycling is critical to a sustainable future for metal products.Finally, regional and international regulations will be highlighted which will effect the efficient recovery and recycle of metals and their overall contribution to environinental protection, economic development and the enhancement of society."

Jan 1, 2000

By R. Padilla

The reaction of chalcopyrite with gaseous sulfur has been investigated in the range 350-450 °C in order to transform this mineral into a more acid soluble copper sulfide and insoluble iron sulfide. The results of thermodynamic analysis of this system as well as the X-ray diffraction analysis of the reaction products showed that in the temperature range 350 400°C the sulfidation reaction proceeded without formation of intermediate copper-iron sulfides according to: The effects of temperature and time on the conversion of chalcopyrite were studied. Conversion of chalcopyrite reached about 80% very rapidly with increase in temperature up to about 400°C. The recovery of copper from the sulfidized samples was determined by leaching in oxygenated 1.2M H2S04, 2M NaCI solution. Copper recoveries over 90 % were obtained from samples sulfidized for 30 min at temperatures lower than 400°C.

Jan 1, 2001

By Motohiro Horiguchi, Kazuo Ichii, Toshio Oishi

"As a fundamental study to prepare copper-based alloys with rare earths (RE: La, Gd, Nd, Ce and Y) without any inclusions, the solubility of rare earth in liquid copper was experimentally determined. Liquid copper alloys were equilibrated with carbon and rare earth carbide in a graphite crucible in an argon atmosphere at 1523-1873 K.Solubilities of rare earth in liquid copper were determined by approaching the equilibrium values from both the lower and the ·higher concentrations than those expected· in the preliminary experiments. They were expressed as a function of temperature. Carbon in Cu-RE alloy was also analyzed and thermodynamically discussed.IntroductionOver the past several years, the demand for highly conductive and high strength copper-based alloys, such as Cu-Cr, Cu-Zr and Cu-Cr-Zr for use in electronic materials has increased.1 -7 These alloying elements are very reactive and easily oxidized to form oxide inclusions during melting. To avoid the oxide inclusions, it may be effective to utilize the strong reducing power of carbon in conditions under which no carbides form.In this study, to provide fundamental data for producing Cu-RE( rare earth) alloys without any inclusions, the solubility of rare earth in liquid copper in equilibrium with .carbon .was determined and discussed on the basis of the experimental results and the thermodynamic data.ExperimentalSample preparation for equilibrium experimentsOxygen-free copper (99.99%), lanthanum (99.9%), gadolinium (99.9%), neodymium (99.9%), cerium (99.9%) and yttrium (99.9%), and their oxides were used as starting materials.Each rare earth carbide was prepared by mixing rare earth oxide with carbon, which is a little more than the stoichiometric composition, pressing it into a tablet form and sintering at about 2000.K for 20 ks in a vacuum furnace using a graphite crucible. Powder X-ray analysis showed that only the carbon and rare earth carbide (REC2) was present in each sample.Cu-RE mother alloys (5-20 mass % RE) were prepared beforehand by mixing metallic rare earth with oxygen-free copper, and melting in an electric arc furnace."

Jan 1, 2000

By Sheng-li Wu, Guo-liang Zhang, Bo Su

The mineralogical characteristics of iron ores can influence their high temperature sintering performance. In this study, eight iron ore samples from Brazil, Australia, and South Africa were characterized by their chemical composition, mineral types, particle morphology, and gangue dispersity. Meanwhile the influence rules between the mineralogical characteristics and the high temperature characteristics were evaluated and analyzed. The results showed that the effect of SiO2 on assimilation characteristic of iron ores was relatively complex, Al2O3 and LOI of iron ores had negative correlation with assimilation temperature of iron ores, the dense slab-flaky mineral granule restrained to the assimilation characteristics of iron ores; liquid phase of iron ores with high SiO2 content and low Al2O3 content had high fluidity, and the higher dispersity of gangue minerals in iron ores was good to the fluidity of liquid phase.

Jan 1, 2015

By P. R. Taylor

Titanium carbide and titanium diboride powders have been successfully synthesized by direct treatment of ilmenite concentrates in a non-transferred arc thermal plasma reactor. Methane gas was used as the reducing agent and boron oxide was used as the boron source in these processes. Free energy minimization plots were used to predict the behavior of each system under different molar ratios and operating conditions. Products were characterized by XRD, SEM and chemical analytical techniques. The average size of the ceramic product is in the submicron range. Metallic iron apparently is finely deposited on the surface of the titanium carbide or titanium diboride particles. Minor impurities such as silica, manganese and zircon were converted to the carbide form.

Jan 1, 1995

By Mei Yang, Wei Gao, Jian Yang, Qingcai Liu, Wenchang Xi

"TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel technology. In APCVD method, TiC14 and O 2 were used as reaction precursor. TiC14 was gasified by using N2 as carrier gas which was controlled to 500sccm. Its reaction temperature and reaction time were limited to 773K and 30min respectively. The physical properties, SEM and SEM-EDX of the TiO2-cordierite carrier and the properties of SCR catalysts prepared by these carriers have been tested. The tests showed that TiO2 loaded by APCVD method were of graininess shape and even accumulation. The loading rate of TiO2 and the specific area of carrier sample were increased 114% and 21 % respectively comparing with sol-gel technology. In the result of sol-gel method, the maximal difference of Ti content was 66.92%, while the result of APCVD method was 18.89%. It demonstrated that TiO2 was uniformly attached with the cordierite ceramic by using APCVD method, which would ensure more active ingredients well loaded on the Ti02-cordierite carrier. This difference made the denitrification ratio of catalyst prepared by APCVD method was 8.1 % higher than that of catalyst prepared by sol-gel method.IntroductionIn recent years, the emission of NOx, which were caused by coal-fired power plants, has gotten more and more attention. SCR (selective catalytic reduction) is the most effective technology to DeNOx [ll. The core technology of it is the catalyst. The SCR catalyst usually uses Ti02 as the carrier, and V2O 5 as the active component [2, 3] . However, the thermal stability and mechanical properties of TiO2 carrier are unstable, which would influence the performances of the catalyst. The commercial catalyst generally uses WO3 or MoO3 to promote its heat stability at present [4-7] Besides, TiO2 is expensive. Compared with TiO2, the cordierite is of good thermal stability and lower price. So loading Ti02 on cordierite porous ceramic as carrier to produce SCR catalyst is of good prospects [S, 91 • Currently, TiO2 is usually loaded on cordierite by the sol-gel method. But some research has shown that the sol-gel method easily reduced the loading performances of TiO2, such as distribution, combination, etc. APCVD (atmospheric pressure chemical vapor deposition) has many advantages to preparing TiO2 films, such as high bonding strength, fast reaction rate and so on [l0-13l_ In this paper, TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel methods. The properties of the carriers prepared by the two processes have also been compared."

Jan 1, 2011

By Masayuki Kudoh, Tohru Maruyama, Yohichi. Ito

When hypo-peritectic carbon steel is quenched during unidirectional solidification, the region of fine columnar grain is observed. It is classified into two coexisting phases. One is coexisting phases of liquid, delta and gamma in the upper part of the region, and the other is coexisting phases of delta and gamma in the lower part of the region. To form the coexisting part of the three phases means that solidification in this experiment proceeds in non-equilibrium state. The size of the narrow side of one fine columnar grain coincides with the arm spacing of a primary dendrite and this result is the same as the hyper-peritectic carbon steel. However, the boundary of the fine grain in the hypo-peritectic carbon steel is formed in different location from that of the hyper-peritectic carbon steel. The former is formed in the skeleton of the dendrite, while the latter is formed in the interspacing of the dendrite. The region of the fine grain changes suddenly to that of the coarse grain when the delta phase in the coexisting part of two phases disappears completely. Therefore, the delta phase in the hypo-peritectic carbon steel might prevent the growth of gamma grain. In order to recognize it, ferrite formers such as Mo, V and Ni are added in the sample. Then, the longitudinal length of the fine columnar grain extends in the sequence of the no addition, Mo, V and Nb.

Jan 1, 2000

By Katsunori Yamaguchi

Secondary materials, that contain relatively high concentrations of platinum group metals, (PGMs) are treated in copper smelting process. The PGMs lost in the slag is increasing with increasing quantities of scrap treated amount. To determine the portion of the PGMs chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. An experimental study was carried out to determine the distribution of palladium between the FeOx–SiO2 slag and the liquid Cu2S–FeS matte at 1573 K and a fixed partial pressure of SO2 of 0.1 atm. It was found that the distribution ratios are around 10−3 for platinum and palladium. The distribution ratios show a tendency to increase when the grade of matte is increased above 60 mass% Cu. In addition, the solubility of platinum in FeOx–SiO2 slag equilibrated with a pure palladium and the Pd-Cu alloy was determined at 1573 K and the range of oxygen partial pressure from 10−9 to 10−7 atm. The solubility of palladium in the slag tends to increase with increasing oxygen partial pressure and activity of CuO0.5 in the slag.

By Bemd. E. Langner

At Norddeutsche AfFmerie the CollaMat is an important instrument for controlling the activity of glue in copper electrolyte. Thanks to on-line measuring of the glue activity appropriate action can to taken in the event of sudden changes, such as an intemption in the glue supply, as well as long-term trends, such as continuously decreasing glue activity over days or weeks. Laboratory tests on the dependence of glue degradation on temperature have shown that relatively small increases in temperature of only 3OC cause the half change value of the glue degradation to reduce by 25 %. It is a similar picture with the sulphuric acid concentration in electrolyte. An increase in the acid concentration from 160 g/l to 200 g/l can - depending on the temperature - likewise result in a decrease in the half change value of up to 25 %.

Jan 1, 1995

By Yanlong Li, Lifeng Zhang, Ying Ren

In this work, a multiphase mathematical model for the fluid flow in argon-stirred steel ladles was established and validated by experimental measurement of wood's metal. Alloy dispersion in the molten steel was calculated. The melting and mixing of alloy was faster with smaller size of the alloy particles, larger superheat and bigger slip velocity. The current mixing time is approximately 300 s with 30 mm alloy diameter and 91.5 K superheat.

Jan 1, 2014

By Thomas M. Harris

To avoid the escalating cost of disposal of metals-containing wastewater and residues, new wastewater treatments will focus on the recovery of the metals. A combination of ion exchange and electrowinning can produce water suitable for discharge and relatively pure metals. The use of a chelating resin can enhance the selectivity of both the removal process and the elution of metals from the resin. A new, simple method of preparing a variety of chelating resins is being developed. The materials produced by this method exhibit interesting, as well as potentially useful, elution behavior. The performance of one test resin is described.

Jan 1, 1992

By K. Potluri, S. Akella, S. Bhansali

"This paper presents the design and angular strength analysis of microneedles for use as a transdermal interface for drug delivery, fluid analysis and sampling etc. Microneedles of different dimensions were designed and fabricated using various materials viz. Si02, OxideNitride- Oxide (O-N-0). The design, modeling and analysis was done using the Finite Element Analysis (FEA) software ANSYS™ 6.1. Angular strength analysis of the microneedles was done using angular loading in ANSYS™, with the corresponding inaterial property settings. Using the force-displacement settings, forces of magnitudes in the range of 10 mN - 25 mN were applied on the microneedles at loading angles ranging from 30° to 90° was applied on needles. Square and circular shaped microneedles were modeled and the displacements and stresses generated were studied to characterize the angular strength of the microneedles. The buckling and force-displacement analyses show that O-N-O microneedles are more strong and robust as compared to needles of other materials. The analysis shows that while circular microneedles have uniform stress distribution, square microneedles have low stresses concentrated along the edges.INTRODUCTIONIn modem clinical and biomedical applications, drug delivery is done either by oral administration or by hypodermic injection. Hypodermic injection of drugs using needles is often painful. Hence, transdermal drug delivery techniques are increasingly being sought out as an alternative. In transdermal drug delivery the needles puncture the Stratum comeurn - the outermost layer of the human skin. The advantage of transdermal drug delivery (or transdermal measurement) technique, is that it reduces pain and tissue trauma."

Jan 1, 2004

By Minh H. Pham

This paper presents a technique for imaging the extent of solidification of molten metal flowing in a cooled pipe based on the concept of eddy currents. A 3D mathematical model, which relates the geometry of solidification to the scattered field induced in a solenoid external to the pipe, is derived. The model is described by a set of integral equations which are solved numerically using the moments method. An iterative algorithm is developed to reconstruct the solidification distribution image. Experimental measurements have shown that the eddy current technique is sufficiently sensitive for practical purposes.

Jan 1, 2001

By Chonghun Han, Tae-Hwa Choi, Young-Hwan Chu

"A statistical optimization method is proposed to maintain stable operation in a blast furnace with stave coolers. The objective of this study is to find the operating condition which maximizes productivity as well as minimizes the heat load on the stave coolers. In this method, we first analyzed historical data and calculated the heat flux of stave coolers and the burden distribution by mathematical models. In this approach, we determined the variables to optimize and manipulated variables to adjust these response variables. Next, we collected the necessary data for the data variables after preprocessing such as removal of noise and outlier. Finally, we constructed empirical models describing the patterns of response variables in terms of manipulated variables by partial least squares regression method, and then these models were used as objective functions for entire optimization problem. By using appropriate optimization algorithm, we determined the compromised optimum operating condition considering all response variables from the past operating conditions.IntroductionBlast furnace operation which is accompanied by complex physical and chemical phenomena is an essential process for steel industry. In this process, iron ore which is charged into the blast furnace from the top goes downward. It is reduced to iron by CO gas and is melted by the heat of combustion of coke and pulverized coal. The pig iron is tapped at the bottom in liquid phase after removing the slag, which floats on the pig iron.The cooling equipment of the blast furnace wall is changed from the plate type to the stave cooler recently. In order to cool the shell uniformly and eliminate shell spray cooling, Pohang No.2 blast furnace of POSCO (Pohang Iron & Steel Company) was equipped with 11 rows of stave coolers. These staves are only 350mm-thick including the 170 mm-deep refractory on the hot face."

Jan 1, 2001

By Ali P. Gordon, James Williams

Joints gasketed with viscoelastic seals often receive an application of a secondary torque, i.e., retorque, in order to ensure joint tightness and proper sealing. The motivation of this study is to characterize and analytically model the load and deflection re-torque response of a single 25% glass-fiber reinforced polytetrafluorethylene (PTFE) gasket-bolted joint with serrated flange detail. The Burger-type viscoelastic modeling constants of the material are obtained through isolating the gasket from the bolt by performing a gasket creep test via a MTS electromechanical test frame. The re-load creep response is also investigated by re-loading the gasket after a period of initial creep to observe the response. The modeling constants obtained from the creep tests are used with a Burger-type viscoelastic model to predict the re-torque response of a single boltgasket test fixture in order to validate the ability of the model to simulate the re-torque response under various loading conditions and flange detail.

Jan 1, 2015

By Liyuan Chai, Bing Peng, Ji Peng, Di Yu

"Electric arc furnace (EAF) stainless steel dust has been classified as a hazardous waste by various government regulatory agencies as it releases heavy metals to environment. The solidification of EAF dust is to stabilize the hazardous components to the amorphous silica-alumina-based clays. The process of solidification is investigated and the softening temperatures of dust and additive clay mixtures are measured for economical thermal treatment. The results indicate that the mixture of dust and local clay with the ratio of 1:1 has the lowest softening temperature 1100 °C and it could pass the toxicity characteristics leaching procedure (TCLP) test for the environmental regulatory limits after thermally treated at softening temperature for 15 min. Major phases of thermal solidification product clinker are CaAl2Si2O8, (Fe, Cr)2O3, (Fe, Mg)(Cr, Al)2O4 and Al6Si2O13.IntroductionThe yield of stainless steels in China arrived to 10 million tons in 2006 and more than 0.2 million tons of stainless steel dust are produced annually. Approximately 1-2 wt.% of scrap charged to an electric arc furnace (EAF) enters the off-gases and then is converted into the dust and reported to the bag-house. The disposal or landfill of the dust becomes a serious environmental problem in China due to the increased production of stainless steels in recent years. The dust contains elements such as chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), cadmium (Cd) and their solubility in leaching media exceeds the environmental regulatory limits [1]. Even though easily feasible for low-grade MgO, it is not appropriate to stabilize the heavy metals from the heavily contaminated soils after the dust landfill [2]. Several dust treatment technologies have been developed and they can be divided into two types. One is to recover the metals from the dust [3, 4] and another is to stabilize hazardous components present in the dust [5, 6]. Recycling of the dust generated in EAF is a remediation option for cleaner production. Direct recycling of EAF stainless steel dust was developed to recover the metal value from the dust and protect the environment [7], but it was only suitable for the dust with high contents of Ni, Cr and Fe. As for the dust with low valuable metal content, thermal solidification is an appropriate choice for the dust treatment."

Jan 1, 2012

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