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By Khandaker M. Anwar Hossain

This paper presents the development of lightweight concrete (LWC) incorporating pumice aggregate and volcanic ash (VA) based ASTM Type I blended cement (PVAC). Fresh and mechanical properties of LWC mixtures such as slump, air content, compressive strength, tensile strength, density and modulus of elasticity are described. The durability characteristics are investigated by drying shrinkage (DS) and water permeability. The investigation suggests the production of LWCs incorporating blended PVAC and VPA having satisfactory strength/durability characteristics for structural applications. The use of PVAC induces the beneficial effect of reducing drying shrinkage and water permeability. Development of such non- expensive and environmentally friendly LWCs with acceptable strength and durability characteristics is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.

Jan 1, 2010

By Qingsheng Liu

A new method of recycling aluminum dross for preparation Al-Si-Ti alloy was studied in this paper. This was carried out in two processes. first the aluminum doss was pretreated by leaching and calcining process, the fine purity and phase of the intermediate oxide powder up to electrolysis demands, then, could be obtained when aluminum dross after washing have been leached for 2h at 100? in 20% hydrochloric acid and calcined for 2h at 1200?, which was treated by cryoite-based molten salt electrolysis. Finally, the Al-Si-Ti alloy was successfully obtained through electrochemical co-deposition in the cathode shows a typical as-cast microstructure. This new recycling method can produce high quality alloy and may bring remarkable economic and social benefits.

Jan 1, 2010

By Igor Zh. Bunin

A model for developing electric discharges between sulfide mineral (pyrite) particles under high-voltage nanosecond pulses in a liquid medium (water) is considered. A possibility of electrical breakdowns of liquid gaps between particles under nanosecond pulses is shown. This probability and the energy released in discharge channels depend strongly on the sulfide conductivity.

Jan 1, 2010

By Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By Elsa Olivetti

Life cycle assessment (LCA) is used increasingly as a tool to provide quantitative metrics of environmental impact and inform early stage materials selection decisions. One common challenge in LCA stems from allocation of burden when multiple adjacent products share some of the same processes. A critical example of this is the partitioning of benefit or burden at product disposition in open-loop recycling scenarios. This work reviews the challenge of allocation and investigates the various methods proposed for allocating end-of-life (EOL) burden. Specifically this work examines whether these methods lead to different results and explores the trends in allocation method bias for or against particular materials classes.

Jan 1, 2010

By A. Krishnan

Keywords: Tantalum extraction, SOM Technology, inert anode, membrane stability The Solid Oxide Oxygen Ion conducting Membrane (SOM) technology offers great potential for environment friendly and energy efficient extraction of high-energy content metals. This work was performed to demonstrate the technical and commercial viability of the technology to produce tantalum metal directly from tantalum oxide and ore concentrates using a solid-oxide, oxygen-ion-conducting membrane (SOM). The process can be used to efficiently produce tantalum metal without expensive pre-processing of raw materials and without harmful by products. The work reported in this paper is: the proof that high purity tantalum metal can be produced, study of the electrochemical behavior of the cell and the method to increase membrane stability.

Jan 1, 2005

By H. Y. Sohn

The considerable progress made in the sulfide smelting technology since the first International Sulfide Symposium of 1983 is discussed. The new developments and innovations have largely been driven by the recognition of environmental concern as well as the need for increased productivity. The smelting technologies for various nonferrous metals are reviewed, with an emphasis on the industry trend towards larger plants and continuous processes. The tremendous advances made in process modeling and computer simulation to describe the complex smelting processes are also reviewed. The goal of these mathematical models is the quantitative description of the processes and the reactors that will provide a means for the control and optimization of smelting operations as well as the optimal design of the operating conditions and the reactors. Environmental issues remain a key consideration in the smelting industry. One of the most remarkable improvements made in the last fifteen years since the 1983 Sulfide Smelting Symposium is the rapid increase in the sulfur capture by nonferrous smelters. This and other related issues are briefly discussed. Finally, the challenges that the smelting industry faces as the new millenium approaches are discussed. The industry continues to face technical challenges to improve productivity and efficiency, while being responsive to ever-increasing public pressure for environmental protection. It also faces external challenges from factors that may cause the reduction of metal uses as a result of substitutions by other materials. Another serious challenge and dire consequence that the primary metals industry is expected to face is the serious diminution of university-educated manpower as well as basic-research output. To remain competitive and healthy, the industry should take up the void left by the complete disappearance, at least in the U.S., and the reduction in other nations, of the governmental support of higher education and basic research in the field of primary metals production.

Jan 1, 1998

By Gabrielle Gaustad

For aluminum, substitution of primary with secondary resources decreases energy consumption; this energy advantage creates a strong economic incentive to recycle. Several authors have raised concerns that the current sinks for secondary materials may soon be saturated, impeding subsequent expansion of recycling. This work combines dynamic material flow analysis with optimal batch planning models to quantify the significance and drivers of these pending limits under several scenarios, and thereby explore potential opportunities to increase recycling. An aluminum recycling system case was developed that includes containers and packaging, automotive, and construction products and scraps. The impacts on aggregate scrap utilization and materials cost are explored in the context of changing alloy demand and lifetime. Insights drawn from this specific case study could be applied to multi-stakeholder, systemic models.

Jan 1, 2010

By Geysen. Daneel

Better slag valorization is part of improving the sustainability of steel, stainless steel and non- ferrous metal production processes. Besides, it can improve the sustainability of other products and production processes as well. A sound and well established slag valorization is beneficial for the overall economics, marketing and appreciation of the metallurgical process and its products. On 6-7 April 2009, the First International Slag Valorisation Symposium was held in Leuven, Belgium. This paper gives a brief summary of the symposium, providing an overview of slag valorization opportunities. The authors believe that high temperature process slags can have interesting applications and that within the next 10 to 20 years slags will need such valorization options in order to compete with other materials and get general support for further production. On the other hand, the authors also expect a higher demand for slags for the production of various materials. High temperature processes should anticipate on the growing opportunities for valorization of slags and increase the resilience of their process by better understanding slag processing, slag quality and material requirements. More interdisciplinary research efforts are required to reach this level of knowledge for the different high temperature processes. Such an interdisciplinary research platform was recently established at KULeuven, Belgium, named SMART-PRO2 (Sustainable Materialization of Residues from Thermal Processes into Products).

Jan 1, 2010

By P. N. Anyalebechi

Keywords: Aluminum alloy 3004, Solidification rate, Homogenization, Second phase particles The effects of the fineness of as-solidified cast microstructure and temperature on the response of aluminum alloy 3004 to homogenization heat treatment (a.k.a. preheat) have been investigated. The study was conducted at 538oC and 595oC on directionally solidified laboratory-size ingots with a range of solidification rate of 0.10oC/s to 29.4oC/s. Optical and electron microscopy, quantitative image analysis, electrical conductivity, and electron probe microanalysis were used to quantify the effects of the homogenization heat treatment on the microstructure of aluminum alloy 3004. In general, increase in fineness of as-cast microstructure and homogenization temperature enhances the a-transformation reaction, dissolution of Mg2Si, elimination of dendritic microsegregation, and dispersoid formation. The homogenization heat treatment reduces the average size of second phase particles in castings solidified at <1oC/s. However, in castings solidified at above 1oC /s, homogenization causes the coarsening of the second phase particles. Mn in solid solution is independent of homogenization heat treatment temperature.

Jan 1, 2005

By Leon H. Bruner

This paper presents a case study describing how a global consumer products company with 138,000 employees that markets over 300 brands in 180 countries is building sustainability into the rhythm of its business. This strategy extends beyond social investment programs by incorporating sustainability into the fabric of product design, manufacturing operations, employee engagement and stakeholder partnerships. During the implementation of this program it has been necessary to be explicit about sustainability and its importance to the business, to broadly define sustainability, to ensure that sustainability is not added work, to eliminate trade-offs between performance, value and sustainability and to implement programs to ensure that sustainability is incorporated into the DNA of the company. Our program continually emphasizes the importance of making no tradeoffs between consumer acceptance of sustainable products and sustainability investments. We also work diligently to overcome the challenges of engaging employees around the world to implement a single coherent sustainability strategy that delivers great results.

Jan 1, 2010

By Zeljka Pokrajcic

Crushing and grinding, or comminution, circuits are the most energy intensive process of a mineral processing plant. Comminution involves the physical size reduction of an orebody to a particle size sufficient for recovery of the mineral values. However, the comminution process remains inherently inefficient. The inefficiency is a result of the operating nature of comminution devices such as grinding mills, where transfer of energy between grinding media and particles in unconstrained and completely random. New comminution circuit design strategies are presented in this paper. The aim of the new strategies is to improve the overall efficiency of the comminution process and reduce the total energy consumption of a comminution circuit. The energy efficient strategies include the: ? rejection of coarse size liberated gangue from the comminution circuit and further downstream size reduction ? use of more efficient grinding and crushing equipment ? the selection of coarser particle product sizes to alleviate the increased energy intensity required to achieve finer product sizes Singularly and when combined, these energy efficient strategies can significantly decrease the overall energy consumption of a comminution circuit. This paper also explores the financial impact of certain energy efficient strategies using an analysis tool called EcoNomics?. It shows that substantial financial gains can be made by including more efficient technologies and methods in comminution circuit design.

Jan 1, 2010

By Joner O. Alves

The disposal of scrap tires has been a serious environmental problem. The treatment of this waste by pyrolysis and combustion has advantages since the landfill space is dwindling and the production of fuel becomes of technological interest. However, that processes needs a rigid control of emissions. This work presents a study of the light hydrocarbon gases (HC) generated during the burn of waste tire chips in a two-stage laminar-flow horizontal furnace. Different temperatures in the primary and secondary stage of the furnace were tested, and the oxygen/nitrogen percentage was also varied during the combustion process. A gas chromatograph was used to identify and quantify the components of the gaseous products of combustion and pyrolysis. The results showed the behavior of the gases during the burn of tires, providing valuable information to the control of hydrocarbon emissions.

Jan 1, 2010

By Zhou Wenbin

In this paper the mechanical properties of high carbon equivalent cast iron for automobile brake discs were analyzed through thermal analysis curves. Experiment results show that the mechanical properties have a strong correlation with thermal analysis curves and an effective way to predict the mechanical properties of high carbon equivalent cast iron was proposed based on the features of thermal analysis curves.

Jan 1, 2010

By María Cristina Ruiz

Enargite rich copper concentrates can not be treated by conventional smelting/converting technology and thus nonconventional methods such as leaching must be used. Since enargite (Cu3AsS4) is a hard to dissolve mineral in acidic solutions, pyrite, a common impurity in copper concentrates, could be used to increase the enargite dissolution rate. On this matter, we present in this work experimental data on the pressure leaching of a mixed enargite-pyrite concentrate in H2SO4-O2. The results show that the dissolution of enargite from the mixed concentrate is considerably faster than the dissolution of pure enargite mineral. The leaching rate increases significantly with temperature. Over 98% of enargite was dissolved in leaching 64 micron size particles at 200 ºC and 100 psi of partial pressure of oxygen in just 30 minutes. A change in the partial pressure of oxygen from 50 to 150 psi showed also a large influence in the leaching rate.

Jan 1, 2010

By Jilai Xue

Industrial wastes containing 30-50 wt.% Al2O3 and 40-60 wt.% SiO2 may serve as an alternative resource for producing Al-Si alloys. Various raw materials such as used refractory materials from metallurgical furnaces, coal fly ash, andalusite residues, and so on were tested in laboratory to produce Al-Si alloys using carbon-thermal reduction process. A mixture of anthracite and petroleum coke was used as reducing agent. One of the most important operations was to prepare the briquettes made of different raw materials with varying contents of Al2O3 and SiO2. The effects of briquette property, A/S ratio (mass ratio of Al2O3 and SiO2), the amount of carbon reducing agent, on the reduction process and the resulting metals were investigated. The results are useful for development of an alternative technology for Al-Si alloy production, which has the potential application in recycling metals from industrial wastes containing Al2O3 and SiO2.

Jan 1, 2010

This paper outlines the complete failure of the U.S. in status and relevance in Rare Earth Oxides (REO). Although rare earth oxides are strategic and critical in their own right, refining these REOs into elements and alloys is even more important for the development of "Green Technologies" and advanced weapons systems. America does not have an active domestic source of rare earth oxides. America does not have any heavy rare earth elemental or alloy capabilities. The magnitude of this failure continues to become more apparent as the manufacture of REO based electronics and magnetic components moves eastward towards China. China has succeeded in outmaneuvering the United States and the world in its quest to control the rare earth oxides, elements and alloys, and the many industries dependent upon REO. What can be done?

Jan 1, 2010

By Elisa Alonso

Manufacturing firms that rely on finite resources have a stake in ensuring sustainable materials use. Higher material prices and uncertain material supply, consequences associated with scarcity, can be damaging to firms. Firms have a number of options to improve material sustainability including dematerialization, material substitution and recycling. However, these options require technological capability, capital investments and supply-chain infrastructure; firms may decide to make such investments only if material prices increase. Once decisions are made, the barriers and delays to implementing changes may harm firms. The impact of not reacting to changes in material supply on firms was examined for the case of different platinum-using industries. It was found that taking action is particularly important for firms when limited material availability leads to volatile market conditions. Industries can benefit especially if they ensure process flexibility and have options for changing their material use patterns.

Jan 1, 2010

By Seetharama C. Deevi, Mohammad R. Hajaligol, Sarojini Deevi

"Carbides and nitrides of iron are being considered as magnetic materials for high-density recording due to their chemical stability and high-saturation magnetization values (> 100 emu/g). Iron carbides and iron nitrides with magnetic properties suitable for magnetic media were synthesized by employing a novel synthesis procedure based on fluidization of powders in reactive atmospheres. Fluidized-bed reactors of laboratory, bench, and pilot scale were employed for the synthesis of iron carbide, FeSC2, by reducing and carburizing U-Fe203 in the temperature range of 300 to 550 ºC. A temperature of 400· ºC and a reaction time of 2 to 3 h are found to be optimal for the synthesis of iron carbide. When the carburization was carried out in a reducing and carburizing atmosphere such as carbon monoxide, nucleation and growth of FeSC2 occurred directly from Fe304 with no intermediate phases such as FeO or Fe. Longer carburization times resulted in the deposition of carbon on the surfaces of FeSC2 particles due to Boudouard reaction, and higher temperatures favored the formation of a mixture of carbides such as FesC2 and Fe3C. Iron nitrides were synthesized by reducing u-Fe203 in the temperature range of 350 to 550 ºC, followed by nitriding in the temperature range of 350 to 550·ºC. The powders were characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analyzer, and a vibrating sample magnetometer.IntroductionRecent demand for high-quality recording of optical, electrical, and audio signals generated interest in magnetic tapes with high-recording densities as compared to the conventional magnetic tapes based on U-Fe203. At present, commercially available magnetic tapes contain maghematite, U-Fe203, as a magnetic material with a saturation magnetization of90 emu/g and a coercive force of 400 Oe. Recording of signals at a higher density per unit volume of magnetic material demands magnetic materials with high-saturation magnetization and a reasonable coercive force. Although metallic iron particles possess a saturation magnetization of 130 to 150 emu/g and a high coercive force of 1000 Oe, the gradual oxidation of iron-to-iron oxides (of lower saturation magnetization) prevents the use of iron particles for high-density recording. In contrast, iron carbides such as FesC2, Fe7C3 and iron nitrides such as Fe4N and Fe3N possess excellent magnetic properties coupled with good electrical conductivities and high hardness. The carbides and nitrides of iron have generated significant interest as magnetic materials for the next generation of magnetic tapes due to their unique magnetic properties and relatively greater oxidation resistance as compared to metallic iron particles [1-4]."

Jan 1, 1994

By P. K. Narasimharaghavan

The major threat to the sustainability of Aluminium Industry is its significant contribution to global warming by way of generation of non eco-friendly gases during its production cycle from Bauxite to the finished product. Though reduction measures are taken in control and effective recovery of values from pot room gases, efforts in use of environment friendly additives in the final products production line is warranted. In this line, the present paper describes our efforts in the use of a new generation refining flux which apart from helping in effective removal of alkali metals, reduction in inclusions and ensure a better metal cleanliness shall also aide in reduction of obnoxious gases generated during the metal refining process prior to casting. The aim of the current work was to reconcile the practical results with the old generation fluxes used. Further improvements to bring in a better metal cleanliness will also be discussed.

Jan 1, 2010