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By Makoto Ohlsuka

The ternary Ni2MnGa intermetallic compound is an intelligent material which has both a ferromagnetic property and a shape memory effect (SME). The use of the shape memory alloy films for an actuator of micro-machines is very attractive because of its large recovery force. The purpose of the present study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni-Mn-Ga films. The Ni-Mn-Ga films with a thickness of nearly 5 um were deposited with a radio-frequency magnetron sputtering apparatus using a Ni50Mn25Ga25 or Ni52Mn24Ga24 target. They were heat-treated at various temperatures between 873 and 1273 K for homogenization and ordering and then cooled in a furnace. The composition of the films depended on the sputtering power. The as-deposited films were crystalline and had columnar grains. After the heat treatment the grains widened and the grain boundary became indistinct with the increasing heat treatment temperature. The martensitic transformation temperature of the heat-treated films increased with increasing nickel content. Furthermore the effect of plastic deformation and constraint aging on SME is also investigated. After plastic deformation, the two-way SME was shown through the martensitie transformation and its reversion, The intensity of X-ray diffraction peaks from stress-induced martensitie phase was found. The constraint-aged films also showed the two-way 3ME by thermal cycling.

Jan 1, 2003

A novel process is being developed for metal recovery from waste electrical and electronic equipment involving a leach reactor coupled to an electrochemical reactor. Metals such as Ag, Au, Cu, Pb, Pd, Sn etc. are dissolved from shredded electronic scrap in an acidic aqueous chloride electrolyte by oxidising them with aqueous dissolved chlorine species. In the electrochemical reactor: (i) chlorine is generated at the anode for use as the oxidant in the leach reactor, and, simultaneously, (ii) at the cathode, the dissolved metals are electrodeposited from the leach solution. The extended Butler-Volmer equation was used to provide predictions of the electrode potential dependences of partial current densities and, hence, total current densities, current efficiencies and alloy compositions for acidic aqueous chloride electrolytes containing Ag(I), Au(III), Cu(II), Pb(II), Pd(IV) and Sn(IV) species, together with dissolved chlorine. With judicious choice of kinetic parameters, the predicted total current density ? electrode potential behaviour of such solutions was in good agreement with experimental data for a rotating Pt disc electrode. Reduction of dissolved chlorine at a Pt rotating disc electrode exhibited mass transport controlled behaviour, in agreement with Levich?s equation over the potential range 0.3-0.9 V (SHE). This could form the basis of a linear sensor, possibly using a microelectrode for measurement and control of the dissolved chlorine concentration in the efflux of leach reactors and inlet to electrowinning reactors in the envisaged process.

Jan 1, 2003

By Roberto Javier Santiago

The main properties of Calcium Carbide seem to be the grain size and the CaC2 content. This paper tries to describe the Calcium Carbide used in the South-American steel plants and how and where it is added.

Jan 1, 2006

By Jason Graetz

Aluminum hydride is a covalent, binary hydride that has been known for more than 60 years and is an attractive medium for on-board automotive hydrogen storage, since it contains 10.1 % by wt. hydrogen with a density of 1.48 g/ml. There are at least 7 non-solvated AlH3 phases, namely a, a', a, ?, d, e and ?. The properties of a-AlH3, obtained from the Dow Chemical Co. in 1980, have been previously reported. Here we present a description of the thermodynamic and kinetic properties of freshly prepared a, 0 and y phases of AlH3. In all cases the decomposition kinetics are appreciable below 100" C and all will meet the DOE 2010 gravimetric and volumetric vehicular system targets (6 wt% H2 and 0.045 kg/L). However, further research will be required to develop an efficient and economical process to regenerate AlH3 from the spent A1 powder.

Jan 1, 2006

By E. Almendras de Siegel

Pyrometallurgical processes have the thermodynamic capability of treating complex and dirty ores and concentrates to produce high purity metals and inert slags. Modem pyrometallurgical processes are environmentally sound and competitive with other processes. However, there is still a need for sensors and other practical tools that permit a rapid evaluation of the performance of these processes. In order to contribute to satisfying this fundamental requirement, the authors developed the IDENT.LA software that permits the automatic mineralogical analyses of inorganic materials, including the final and intermediate products of pyrometallurgical processes. The technique allows determining the grain size distribution of mineralized inclusions, the surface relations between metallic phases, and conducting modal analyses of the essential phases that are present in the samples. Three basic automatic operations are performed: creating a representative image of the sample; identifying the metallic and non-metallic phases; and measuring the features of the resulting image. The results are used to evaluate the performance of pyrometallurgical and other processes. In this paper, the authors discuss the application of the technique to a sample of slag from a slag cleaning process that uses a carbonaceous reductant. In this case, process performance impacts not only on the efficient reduction of the slag magnetite and on copper recovery but also on the quality of the process off-gas. The mineralogical analysis of the slag is a valuable tool in assessing process performance and in recommending changes of operating conditions.

Jan 1, 1999

By D. C. Azubike

Wolframite (FeWO4) usually having cassiterite (SnO2) as a major impurity is a primary source of tungsten. Its direct reduction/carburisation with carbon in the temperature range 1000-1400°C, and with hydrogen at 600-900°C followed by carburisation with CO at 900°C are described. Depending on the conditions and reactants employed, Fe, Fe2W, B-Sn,WC, W2C, Fe3W3C and Fe6W6C are the products. Tin was found to inhibit the overall reduction and carburisation reactions significantly. The potential for either efficient separation of iron and tungsten or a one-stage production of an iron-based metal carbide composite is discussed.

Jan 1, 1992

By Yanhui Sun, Yanan Zeng, Kaike Cai

"Hot ductility of Nb-V-containing steel has been studied by theoretical calculation and thermal simulation experiment. Meanwhile, microsegregation and precipitates were analyzed. The results showed that segregation degree of elements S, P, 0 is greater in mushy zone, while, the hot ductility was deteriorated by inclusions of Fe(S,O), (Fe,Mn,Si,Al)(S,O) in the interdendritic region. At the temperature 1100°C, a few NbN particles, 60-70nm, have little effect on mechanical property. In the temperature range 1000°C to 975°C, R.A declined rapidly from 82.36% to 69.61% with the diameters decreasing from 20 to 10nm and quantity of particles increased 23 to 45inds/µm2, respectively. In the temperature range from 900°C to 850°C, R.A reduced unobviously from 34.27 % to 30.01 % with ferric films thickening gradually. The critical stress, 52.38MPa, was equal to tensile strength at 975°C. Intergranular fracture was easy to occur with higher critical stress below 975° C.IntroductionProductivity and product quality of slab are seriously affected by cracks during continuous casting and the influencing factors of cracks are various[l]. From microcosmic angle, resisting deformation ability of initial solidification shell decreases obviously with solute elements segregation which can urge the low melting point ofliquid film to form at grain boundaries[2, 3]. Meanwhile, with temperature decreasing, particles would precipitate as the practical solubility product is greater than equilibrium solubility product. The carbonitrides would lead to stress concentration at austenite grain boundaries. Therefore, the transverse cracks of microalloyed steel would form during the straightening operation in the continuous casting process. The hot ductility of steels in the temperature of mushy zone was characterized by microalloy elements segregation, zero strength temperature (ZST) and zero ductility temperature (ZDT). The nature, shape, and size of precipitates have been investigated by TEM (JEM2100). Hot tensile test with low strain rate was simulated by Gleeble-1500. The objective of present study is to provide reference for zero defect of microalloyed steel during continuous casting process."

Jan 1, 2013

By Qionghua Zhou, Wei Liu

"Nanocrystalline silver bulk material with average grain size of 20.3 nm was prepared by warmvacuum- compaction method. The as-prepared nanocrystalline silver was characterized by X-ray diffraction (XRD), differential scanning calarmeutry analysis (DSC), thermogravimetric analysis (TG), and 6157 type Electrometer test, respectivily. The experimental results show that the average grain size and microstrain of the nanocrystalline silver are 20.3 nm and 0.088%. The melting point and melting enthalpy are 1228.7 Kand 82.34 Jig, which are lower than that of coarse-grained silver by 6 Kand 22.6 Jig, respectively. The electrical resistivity of nanocrystlline silver increases with higher temperature when the range of temperature is between 233K and 293K. The electrical resistivity at 293 K is 1.475xlO -7 Q·m, which is higher than that of coarsegrained silver by a factor of 9.IntroductionN anocrystaline ( nc) materials or nano structured ( ns) materials are three-dimensional (3 D) bulk materials with average grain size typically smaller than 100 nm. Ne materials have been of great interest for their unique properties, such as superior tensile strength [1-2], high microhardness [3- 4], superplasticity [5-6], magnetically quasi-isotropic [7-8] , and so on, making them one of the most promising nano-scale materials with wide applications. Ne materials with average grain size of 5-10 nm were firstly fabricated by Gleiter et al. [9] in 1980s, using inert gas condensation (IGC) method. Unfortunately, the large surface to volume ratio creates a high surface energy component in the total free energy of the system and results in a metastable state in the materials. Therefore, due to the signfica nt disordered grain boundary regions, nanomaterials are thermally unstable and are subjected to a strong driving force for grain growth. The grain growth even occurred at room temperature [10].The conflict or deviation of measured date, e.g. strength, microhardness, thermal stability, partly due to the grain boundary ratio or the distribution of grain size, and partly derived from imperfections such as voids and microcracks while earlier processing techniques are known to result in incomplete dens:fication [11-12]. Therefore, the higher quality samples produced in subsequently years still show such a general trend."

Jan 1, 2011

By S. N. Ojha, Gouthama, R. K. Mandal

"Spray deposition processing of liquid immiscible alloys, based on AI-Pb and Cu-Pb systems have been investigated. Process variables have been optimized to generate uniform dispersion of ultrafine second phase particles in· the matrix of the primary phase. Mechanisms governing the microstructural evolution in this synthesis methodology are discussed. Results of the present investigation are used to demonstrate that rapid solidification of atomized droplets initially provides a high nucleation rate of the second phase during the liquid phase separation. The solid matrix phase nucleates at a later stage and grows with a high velocity enabling trapping of the dispersed phase. Subsequent alteration in the size and size distribution of the second phase is suggested to arise further during deposition of high velocity droplets. Possible reasons for this effect are brought out. Microstructural features of atomized powders and spray-deposits of these alloys are presented to support the present approach of synthesizing composites. IntroductionIn recent years, synthesis of advanced materials with metastable microstructures and ultra fine dispersion of second phase particles has led to the development of novel techniques of materials processing. The other requirement of such a processing methodology is to achieve near-net shape geometries in less number of processing steps. The solidification processing method via spray deposition route qualifies these criteria. This process primarily involves atomization of a melt by high energy gas jets into spray of droplets which are subsequently propelled by the kinetic energy of the gas towards a deposition substrate to build-up a thick high density preform. Although the concept of spray deposition was pioneered by Singer [1] in the early seventies, the fundamentals of the deposition process has been understood only recently [2-4]. Several benefits of spray deposition processing are by now well established [5,6]. Rapid solidification effects are inherent in spray deposition processing due to high heat exchange rate at the droplet-gas interface and also on the deposition surface by force convection. Since considerable heat extraction occurs from the atomized spray prior to droplet consolidation, a relatively low processing temperature is ensured in this process. As a result deleterious coarsening phenomenon can be minimized. In addition, controlled maneuvering of the substrate provides the capability of the process in producing disc, sheet or tube shape preforms of difficult to work materials in a single operation. A significant improvement in properties, resulting from microstructural homogeneity and refinement in grain size induced by spray deposition has been reported for several alloy systems [7,8]."

Jan 1, 1994

By Torn H. Okabe

A fundamental study was conducted with the purpose of establishing an environmentally sound recovery process for recycling of valuable metals, by combining scraps containing such metals. As an example, direct extraction and recovery of neodymium (Nd) in magnet scraps was investigated by utilizing liquid metal as an extraction medium. It was found that liquid magnesium (Mg) is a suitable extraction medium and can extract Nd from iron alloys with high efficiency at around 1100 K. The newly developed extraction apparatus for Nd is a mechanically simple and static device without moving parts, where the Mg extraction medium circulates due to differences in the temperature inside the reaction vessel. This developed device can simultaneously accomplish continuous extraction of metal Nd from scraps, re-extraction of Mg from Mg-Nd alloy and the eventual recovery of pure Mg. As a result, metal Nd with 98 % purity was directly recovered from magnet scraps under certain conditions. It was also shown that the extraction agent Mg could be reused. The results of this investigation show the possibility of establishing a new process for the direct extraction of Nd in pure metal form without oxidization.

Jan 1, 2003

By Torn H. Okabe

A fundamental study was conducted with the purpose of establishing an environmentally sound recovery process for recycling of valuable metals, by combining scraps containing such metals. As an example, direct extraction and recovery of neodymium (Nd) in magnet scraps was investigated by utilizing liquid metal as an extraction medium. It was found that liquid magnesium (Mg) is a suitable extraction medium and can extract Nd from iron alloys with high efficiency at around I 100 K. The newly developed extraction apparatus for Nd is a mechanically simple and static device without moving parts, where the Mg extraction medium circulates due to differences in the temperature inside the reaction vessel. This developed device can simultaneously accomplish continuous extraction of metal Nd from scraps, re-extraction of Mg from Mg-Nd alloy and the eventual recovery of pure Mg. As a result, metal Nd with 98 % purity was directly recovered from magnet scraps under certain conditions. It was also shown that the extraction agent Mg could be reused. The results of this investigation show the possibility of establishing a new process for the direct extraction of Nd in pure metal form without oxidization.

Jan 1, 2003

By Bernhard J. Ralph

In refractory gold ores much of the gold occurs in sub-microscopic form in sulfide minerals, most commonly pyrite and arsenopyrite Bacterial leaching is being developed as a pretreatment for these minerals to aid the liberation of gold and a variety of extracting reagents. This paper reviews the nature of the principal micro-organisms involved, the effects of various physico-chemical factors on the rate and extent of extraction, and likely mechanisms involved.

Jan 1, 1989

By Katsuyasu Sugawara, Takuo Sugawara, Shin-ji Abe, Tadakazu Kagami

"In order to clarify the mechanism and to obtain the fundamental data for heavy metal recovery from an incinerator ash by chlorination, pure chemical reagents, zinc oxide and lead oxide or the fly ash blended with calcium chloride and silicon dioxide were heated up to 1000°C in a nitrogen stream. Thermogravimetric curves of the samples with the chlorinating reagents indicated that solid-liquid reactions accelerated the chlorination and release of metals from the solid phase. The formation of liquid phase of calcium chloride played an important role on effective recovery of zinc and lead at lower temperatures below 800 °C. Although zinc and lead could be decreased in the incinerator ash without chlorinating reagents, addition of chlorinating· reagents enables the removal of metals in high extent· at lower temperature.IntroductionFly ash is discharged about 3,000 tons/day (about 110 million tons/year) from incinerators of municipal solid waste in Japan and mostly fly ash is disposed in landfills. Fly ash includes heavy metals e.g. zinc and lead. Since untreated fly ash caused hazardous leaching problems, Waste Disposal and Public Cleaning Law was revised in 1992, fly ash being designated 'specially controlled' general waste. Fly ash must be disposed by the following suitable, intermediate four methods: [I] Cement- Solidified Method, [2] Immobilized Chemicals Method, [3] Melting Solidified Method, [4] Acid Leaching Method, permitted by the Ministry of Health and Welfare, Japan."

Jan 1, 2000

By Huaming Yang

Infrared materials are a special kind of material widely used in military, biological engineering and chemical industry. However, the problems associated with them such as unstable properties, high cost and a high thermal expansion coefficient seriously restrict the development and the wide application of the traditional infrared materials with the SiC or ZrSiO4 matrix. The ultrafine quartz powder is normally used to prepare the infrared materials by hot-pressing technology. The aim of the paper is to investigate the thermal expansivity, the effect of the SiO2 size and the addition of Al2O3 or Fe2O3 on the infrared emissivity of the quartz matrix of the infrared material (QMIM) in a 8-25um wavelength range. The results indicate that 89% of infrared emissivity and 0.4x 10-5/°C of thermal expansion coefficient of QMIM can be obtained. The affecting mechanism of A1203 and Fe2O3 on the infrared emissivity of QMIM were also discussed.

Jan 1, 2003

By Huaming Yang

Infrared materials are a special kind of material widely used in military, biological engineering and chemical industry. However, the problems associated with them such as unstable properties, high cost and a high thermal expansion coefficient seriously restrict the development and the wide application of the traditional infrared materials with the SiC or ZrSiO4 matrix. The ultrafine quartz powder is normally used to prepare the infrared materials by hot-pressing technology. The aim of the paper is to investigate the thermal expansivity, the effect of the SiO2 size and the addition of AI2O) or Fe2O3 on the infrared emissivity of the quartz matrix of the infrared material (QMIM) in a 8-25um wavelength range. The results indicate that 89% of infrared emissivity and 0.4x 10.5°C of thermal expansion coefficient of QMIM can be obtained. The affeeting mechanism of Al2O) and Fe2O3 on the infrared emissivity of QMIM were also discussed.

Jan 1, 2003

By Adriana A. S. Felix, Julio C. Afonso, Luiz C. Bertolino, Bruna L. Novo, Fernanda A. N. G. Silva, Karla M. A. Simões

Palygorskite (Mg,Al)5Si8O20(OH)2(OH2)4.4H2O, is a lamellar mineral with a fibrous morphology. The micropores and canals in the structure give a high specific surface and sorption capacity of various kinds of species. Guadalupe’s palygorskite (Piauí/Brazil) run of mine (ROM) was prepared (PA) and characterized by XRD and XRF. PA is composed by palygorskite, kaolinite, quartz and goethite and has 15.8, 58.0, 4.2 and 7.6% of SiO2, Al2O3, MgO and Fe2O3, respectively. Wet magnetic separation tests were conducted with PA obtaining the magnetic and non-magnetic fractions (PAM and PANM, respectively). PANM was characterized by XRD and XRF and the results of the XRF indicated that the iron content in the PA decreased 8.0% in the non-magnetic product. A new wet sieving was conducted with PANM to obtain a purer fraction (−20 μm) (PANMP) which was characterized by XRD, XRF, CEC, Zeta potential, SEM, TG/DTG. The result showed that this mineral could be used as adsorbent of heavy metals.

Mar 1, 2017

By V. V. Kutumbarao, M. T. Nimje, G. Balasubramanian

Wastes from the aluminium industry such as red mud from the alumina refinery, fly ash from the captive power plant and spent pot lining from the smelter, have been successfully converted into glass-ceramic products. The process involves addition of a small quantity of glass former along with traces of nucleating agents to aid crystallization, to a specific mixture ofred mud, fly ash and spent pot lining, followed by melting at around 1300°C and vitrification by cooling. The resultant glass is then converted into a glass- ceramic by a suitable heat treatment at around 700 - 750°C. The glass-ceramic products show excellent wear resistance, besides possessing an aesthetic appearance. The major application foreseen for such products is as decorative tiles in the building industry.

Jan 1, 2000

By Katsumi Ogi, Hiroto Uchida, Masamitsu Sato, Atsushi Itsuki

"(BTMSE)Ag(hfac) (BTMSE = trans-bis(trimethylsilyl)ethene) was chosen as a suitable precursor for the XeCl laser (308nm) MOCVD of Ag. Iso-propanol solution of (BTMSE)Ag(hfac) was used as a liquid source for the liquid delivery method, high deposition rate 9nm/min at substrate temperatures of 100°C and 120°C were obtained at the vaporizer temperature of 90°C. This deposition rate is three times faster than by conventional bubbling method and life of the source and reproducibility of the deposition were also improved. Electric resistivities of the laser deposited film shows significantly low resistivity of 10-6Q-cm compared to 1 o-3Q-cm of thermal MOCVD film. These results indicates that the laser MOCVD is one of the effective method for the preparation of the high quality silver film.IntroductionSilver films are a potentially important metallization material in electronic and photonic devises due to their lowest resistivity (1.6µ0-cm) among the metals, high optical reflectance and chemical stability. The MOCVD technique has advantages to sputtering or evaporation in the point of conformal growth and better coverage on sharp steps and narrow gaps[l-2]. For MOCVD application, silver precursors must have sufficient vapor pressure without decomposition at their evaporation temperature. To achieve stable precursor gas supply, liquid delivery of precursor material is promising[3-4] especially for materials that have not enough heat stability and high vapor pressure like silver complexes[S-10]. Several new silver complexes for MOCVD and UV irradiation effect to their MOCVD silver film quality were reported by same authors[5]. In this paper new solvent system for liquid delivery system of silver MOCVD were investigated to suite XeCl(308nm) laser MOCVD application."

Jan 1, 1998

By Wen-long Zhan, Zhe Ning, Jun-hong Zhang, Teng-fei SONG, Zhi-jun He, Qing-hai Pang

In order to investigate the influence of granularity on the gasification property of coke after microwave irradiation, comparison of ordering of carbon structure and internal microstructure of granular coke before and after microwave pretreatment was carried out. It is shown in X-ray diffraction results that the diffraction intensity of the coke sample significantly increased after 40 s irradiation under 264 W microwave power, which indicated the decrease in reactivity of coke.

Mar 1, 2017

By E. A. Chavarriaga, L. J. Jaramillo, O. J. Restrepo

"This paper presents the results of the manufacturing ceramic pigments with spinel structure, using methods of synthesis of low temperature. In this work we obtained spinel structures type by the methods of Self-combustion, Coprecipitation, Microemulsion, Gel citrate and Pechini. These methods become an attractive alternative to traditional method (ceramic method), since we can work at a lower temperature, reducing manufacturing costs, lower fuel consumption, less wear on equipment and other environmental and economic implications. Also it is possible to have control over features such as stoichiometry, morphology of the products, reaction times and structures. The products obtained by these routes will be used in the manufacture of ceramic pigments and characterized using different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrophotometry.IntroductionSpinels are ternary oxides AB204, where A and B are cations occupying tetrahedral and octahedral positions respectively. These oxides exhibit interesting electrical, magnetic and catalytic properties [1-4], depending on its nature, charging and intrinsic distribution of ions [5].The most widely used method to prepare spinels has been through solid state reaction, which consists of mixed oxides at high temperatures [6, 7]. In the last years, there have been a strong tendency to use chemical routes for the synthesis of crystalline ceramic particles at low temperatures [8,9]. Unconventional methods currently employed for the synthesis of complex oxides are Gel citrate method, Pechini, Spontaneous combustion, Microemulsion and Coprecipitation. Pechini method [10, 11], based on polymeric precursors, does not require high temperatures and allows stoichiometric control for greater reproducibility. This method involves the formation of a polymeric resin between a metal quelate and polyhydroxy acid of alcohol by polyestirification.Coprecipitation is important for many environmental problems related to water resources, including acid mine drainage, migration of radionuclides in waste repositories dirty, transport of contaminant metals in the industry, metal concentrations in aqueous systems and the technology of wastewater treatment. The coprecipitation process can vary in each case; the partition in the solid phase can be carried out by surface adsorption, ion exchange, surface precipitation, occlusion and formation of solid solution. The formation of solid solution is the result of structural incorporation of the marker in structural support sites resulting in a minor component in the solid solution with the host phase that has a very low solubility of pure solid [12]. Synthesis by gel citrate method allows the use of a route to obtain ceramic pigments from a very simple experimental system in which the stoichiometric control, the size and shape of the particles and the purity of the phases obtained can be controlled more accurately [13]."

Jan 1, 2012