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By E. Dendy Sloan

An overview of hydrate properties is given, with emphasis on unusual deviations from ice, the most common solid water form. Reliable sample preparation and reproduction of in situ hydrates provide the foundation for all hydrate science and engineering. Relations are given to connect the three domains in the title: (1) micro-scopic properties measured with Raman, NMR, and diffraction spectroscopy, (2) meso-scopic properties measured with single crystals, and (3) macro-scopic properties measured with pressures, temperatures, volumes, etc. A principal illustration relates micro-scopic and macro-scopic domains. Experiments provides the basis for improving statistical thermodynamics model for these compounds. To date, this model is one of the most commonly used industrial statistical thermodynamics applications, based upon the classical model of van der Waals and Platteeuw (1959). Microscopic measurements and simulations indicate model assumption improvements, resulting in the next generation of the statistical thermodynamics for improved macroscopic property prediction.

Jan 1, 2002

By Bo Jiang, Lianyun Liu, Hongmin Zhu, Kai Huang

"Watermelon peel is selected as a novel adsorbent to remove Pb(II) from aqueous solution. A simple saponification process is proposed to modify the peel and the adsorbent is characterized by SEM and FTIR. The effects of pH, contact time, initial concentration of Pb(ll), biosorbent dosage and temperature on adsorption of Pb(II) are investigated. Different models are used to fit experimental data. These models indicate that the adsorption process follows the Langmuir model and pseudo-second-order model. The maximum adsorption capacity obtained from Langmuir model is 1.05mol kg-1 for the prepared sorbent. Equilibrium time is attained in 5-10 min for the studied concentrations. The watermelon peel can be used as an effective and low-cost biosorbent for removal of Pb(ll) from aqueous solution.IntroductionRecently, removal of heavy metal ions from industrial effluents by biosorption has become a very attractive topic, since the more serious pollution issues caused by heavy metals emerge frequently, and more strict requirements for its control are called upon by society [1,2]. In this case, most conventional purification technologies are not suitable due to poor cost-effectiveness [3]. For example, chemical precipitation by alkaline reagents usually can not decrease the metal ion concentration below the permissive levels, and also it will produce a large amount of sludge containing toxic metals. Membrane separation techniques can realize deep purification of wastewater easily, although its operating cost is usually high. Thus, considering the high effectiveness, low cost and free-sludge operation, bisorption has become a promising technique in water treatment [4]. The most important thing for this technology is the synthesis of a suitable biosorbent, whose adsorption properties will determine the removal efficiency and economic cost for the whole process. Watermelon is one of the most popular fruits for mankind for its delicious flavor. Usually, the watermelon is consumed mainly for its edible pulp, and its peel is discarded or only used as feed for livestock. Considering the pectin contained in the watermelon peel, just like that in orange wastes in the reported literatures [3], the idea of using it as the raw material to prepare the biosorbents for heavy metal ions removal from the aqueous solution was evaluated in this study."

Jan 1, 2012

By I. G. L. Sinclair

The Selbaie deposit is located in northern Quebec. It is comprised of three distinct, but genetically related, Cu-Zn-Ag ore bodies which also contain economically significant amounts of Au. The deposits are Archean in age and volcanogenic in origin. At Selbaie, ore microscopy has been employed to aid in planning of ore beneficiation methods and to monitor the ongoing performance of the concentrator. Examples of both types of study are described. Early in the life of the mine, excessive amounts of Zn appearing were found to be appearing in the Cu concentrate. Microscopic examination of concentrates showed that this was being caused by the presence of coatings of supergene chalcocite on sphalerite grains. Fine coatings of supergene galena and chalcopyrite were also observed on some sphalerite grains. The presence of Ag and Au in the ores makes an important contribution to the revenue of the mine. The various modes of occurrence and mineralogical relationship of these two metals are described and discussed. Monitoring of the ongoing concentrating process at selbaie is done by qua-litative and quantitative examination of products collected at various points along the circuit. Causes of such problems as excessive loss of metals to the tailings or inefficient recovery of individual metals, can often be identified and possible solutions proposed.

Jan 1, 1989

By A. Perillo

The process, realized in. the Kivcet furnace, can convert continuously lead concentrates, residues and secondary lead bearing materials into a lead bullion free of sulphur and a discardable slag. The lead recovery can be up to 99%. The long experience of about three years at Portovesme demonstrates the capability of the furnace to smelt a very. high range of lead raws without interruption of the operation. The operating costs are very competitive in comparison to the traditional technology. The work place and environment are clean and new tight regulations for the? hygiene control are met. The Kivcet furnace can be considered as consisting of three parts (reaction shaft, waste gas shaft and electro-furnace) connected with a common hearth. The technical basis of the furnace construction is the application of a number of design elements .which have mostly been used before in designs of industrial furnaces, such as open hearth furnace, refining furnace and other furnaces dealing with liquid meta1s. Refractory wear in the reaction shaft with typical pattern from watercooling soon has been stabilized and since maintained. No deformation of the furnace shell and no leakage of metal or s:l:ag through the bottom is? appeared after three years' operations.

Jan 1, 1990

By Alana Pereira Ramos, Walman Benicio de Castro

Amorphization and martensitic transformation (Ms) characteristics of Ti–Ni-Cu alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change the wheel linear velocity from 21 to 63 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate and alloy composition on martensitic transformation behavior is discussed.

Jan 1, 2015

By Jiann-Yang Hwang

A study on microwave assisted chalcocite leaching was carried out with a microwave hydrothermal reactor. The leaching was conducted with thick mineral slurries (50-100 g/l). The leaching media is a mixed solution of CuCL2 and NaCL The investigation included the effect of leaching temperature, quantities of the minerals per unit slurry volume as well as the initial concentration of cupric ions were investigated. The results were discussed and compared with that using conventional leaching method.

Jan 1, 2003

By José D. T. Capocchi

Viscosity of liquid lead, tin, and Pb-Sn alloys has been measured by the rotational viscometer method in the temperature range from 50 K above their respective liquidus temperature to 823 K. The results are accurate to within ±1.0 %. The variation of viscosity with temperature followed the Arrhenius-type equation µ = µo.exp(Q/RT). The composition dependence of the isothermal viscosity and the activation energy for viscous flow have not shown anomalous changes at the eutectic composition of the Pb-Sn system.

Jan 1, 2000

By Yichi Lu, Haydn N. G. Wadley, Douglas T. Queheillalt

"Using a 3-D ray tracing methodology combined with laser ultrasonically measured elastic constant data near the melting point, ultrasonic propagation in cylindrical single crystal bodies containing either a convex or a concave solid-liquid interface have been simulated and used to design new sensing concepts. Ray paths, wavefronts and time-of-flight (TOF) of rays that travel from a source to an arbitrarily positioned receiver have been calculated. Experimentally measured TOF data have been collected using laser generated/detected ultrasound on model systems with independently known interface shapes. Both numerically simulated data and experimental results have shown that the solidification (interfacial) region can be identified from ultrasonic transmission TOF data. Since convex and concave solid-liquid interfaces result in distinctively different TOF data. When TOF data collected in the diametral plane are used in a nonlinear least squares algorithm, the interface curvature has been successfully reconstructed and ultrasonic velocities of both the solid and liquid obtained. The reconstruction errors were found to be less than 5%.IntroductionMany of today's single crystal semiconductors are grown by variants of a vertical Bridgman technique in which a cylindrical ampoule of a molten semiconductor is translated through a thermal gradient, resulting in directional solidification and the growth of a single crystal, Fig. 1.1 It has long been recognized that during crystal growth the velocity and the shape of the solid-liquid interface, together with the local temperature gradient, control the mechanism of solidification (i.e. planar, cellular or dendritic), the likelihood of secondary grain nucleation/ twin formation (i.e. the loss of single crystallinity), solute (dopant) segregation, dislocation generation, etc. They thus determine the crystals' resulting quality.2-4 The solidification rate and the solid-liquid interface shape are also sensitive functions of the internal temperature gradient (both axial and radial) during solidification.5•6 This in turn is governed by the heat flux distribution incident upon the ampoule, the latent heat release at the interface, and heat transport (by a combination of conduction, buoyancy and surface tension driven convection, and radiation) within the ampoule. The solid-liquid interface's instantaneous position, velocity and shape during crystal growth are therefore difficult to predict and uncontrolled during growth, especially for those semiconductor materials with low thermal conductivity (e.g. CdTe).4-6 The development of technologies to non-invasively sense the interface position and shape throughout the vertical Bridgman crystal growth process has therefore become a key step toward developing a better understanding of the growth process, for enabling sensor-based process control, and thus ultimately for improving the yield and quality of difficult to grow semiconductor materials like CdTe."

Jan 1, 1997

By Takashi Araki

In this work, we have elucidated the two-step oxidative reaction mechanism of 2,4,5-trichlorophenol by adsorbing oxygen atom for oxidative decomposition reaction of 2,4,5-trichlorophenol on oxide catalyst surface using ab initio molecular orbital calculation. In the first oxidation, total energies of reaction products have been shown extremely stabilized at all oxidation positions. This reaction occurs due to charge transfer from benzene ring to adsorbing oxygen atom. As a result, 1£ bonding of benzene ring are weakened. However, the benzene ring of 2,4,5-trichlorophenol does not perform cleavage reaction. In the second oxidation, the benzene ring of2,4,5-trichlorophenol can perform cleavage reaction, since the second oxidation obtains larger stabilized energies than the first oxidation.

Jan 1, 2003

By Yasushi Sawada

An experimental investigation was carried out to study the rates of reduction of iron oxides dissolved in liquid Ca0-SO2-A203 slags by Fe-C droplets at temperatures ranging from 1325 OC to 1550 OC. The %FeO in the slag was varied from 5.5 to 18. Flash X-ray images were employed to observe the behavior of Fe-C droplets in the slags during the reactions and for determining the slag-gas-metal interfacial area. Effect of P205 in the slag and sulfur in the droplet was also investigated. The reduction rates were determined by measuring the volume of CO evolved as a function of time and the estimated slag-gas- metal interfacial area. The reduction rates have increased with increasing %FeO in the slag and the slag temperature. The experimentally established relationship between the reduction rates and FeO (wt%) in slag is given by

Jan 1, 1992

By Takashi Araki

In this work, we have elucidated the two-step oxidative reaction mechanism of 2,4,5-trichlorophenol by adsorbing oxygen atom for oxidative decomposition reaction of 2,4,5-trichlorophenol on oxide catalyst surface using ab initio molecular orbital calculation. In the first oxidation, total energies of reaction products have been shown extremely stabilized at all oxidation positions. This reaction occurs due to charge transfer from benzene ring to adsorbing oxygen atom. As a result, ? bonding of benzene ring are weakened. However, the benzene ring of 2,4,5-trichlorophenol does not perform cleavage reaction. In the second oxidation, the benzene ring of 2,4,5-trichlorophenol can perform cleavage reaction, since the second oxidation obtains larger stabilized energies than the first oxidation.

Jan 1, 2003

By Edwin Adoyi Ali, Zainab Shehu Aliyu, Adele Dzikwi Garkida, Muhammad Dauda

Feldspar from Matari, Nigeria was analyzed using SEM, XRD and XRF techniques for microstructural analysis, mineral phase analysis and chemical composition analysis respectively. Qualitative and quantitative XRD analyses revealed the presence of microcline 59.6%, albite 34.7% and quartz 5.71%. The XRF results showed that the feldspar contains 67.32% SiO2, 17.54% Al2O3, 11.33% K2O, 2.75% Na2O, 0.12% CaO, 0.01% MgO, 0.02% MnO2, 0.10% Fe2O3, 0.00% Ti2O, etc and 0.14% LOI. SEM/EDX analysis shows the presence of microcline feldspar as the dominant phase, exhibiting lamellar twinning. The XRD has also revealed that potash has the highest peak, indicating its high concentration. The 0.10% Fe2O3 present is within the permissible level (0.1-0.3%) for glass making and also within the potash feldspar specifications (0.17%). The Matari feldspar is a microcline type, rich in potash, alumina and silica, enabling it meet the standard specifications for alumino-silicate glass.

Jan 1, 2015

By C. O. Bounds

Management of emission control dust from electric? arc furnace (EAF) steelmaking as an RCRA-EPA listed hazardous waste places economic and environmental pressures on the steelmaking industry. Horsehead Resource Development Company, Inc. (HRD) serves the industry by recovering nonferrous metals from the dust in rotary kiln plants in Palmerton, PA and Chicago, IL, and has demonstrated the commercial viability of its patented coal-fired FLAME REACTOR Process. However, because of location and/or regulation, many steelmakers could be more economically served via on-site processing of its dust. Therefore, in 198-7, through a contract with the Gas Research Institute, HRD embarked on a program to develop a gas-fired reactor and test a prototype unit. The development program has successfully proven the environmental, technical and economic performance of the concept. Consistently high zinc, lead and cadmium recovery to an oxide concentrate as well as production of a nonhazardous, delistable slag have routinely been achieved. The gas-fired FLAME REACTOR field experiment results and the economic performance of on-site or smaller regional plants will be highlighted.

Jan 1, 1990

By Xiang Ma, Halvor Dalaker, Kai Tang, Stefan Andersson

Silicon carbide (SiC) is one of the most important non-oxide ceramic materials for many industrial applications and is mainly synthesized by carbothermic reduction of silicon oxide by coke above 2200°C. Replacing natural gas (mostly methane, CH4) for coke in SiC synthesis could considerably reduce energy consumption and CO2-emissions owing to higher carbon activity of CH4 at lower temperature. The generally accepted reaction mechanism is that SiC is synthesized through gaseous intermediate silicon monoxide, SiO. In the present study, the reaction mechanism for the SiO and CH4 gaseous mixture has been examined using atomic scale modelling. Molecular dynamics (MD) using a reactive force field (ReaxFF) has been utilized to examine the initial stages of reactions involving a gas mixture of SiO and CH4 and surfaces of SiC. The MD results revealed some interesting SiC formation mechanisms. The reaction energies of the critical intermediate species were also estimated by density functional theory (DFT) calculations and the implications for the force field parameters used in ReaxFF was discussed.

Jan 1, 2015

Cuspidine (3CaO?2SiO2?CaF2) is one of the most important compounds crystallized in mold flux films during casting in the continuous casting process of steel. The primary crystallization field of cuspidine has been experimentally developed in the CaO-SiOrCaF2-SiF4 system. The cuspidine-NaF binary and cuspidine-CaF2-NaF ternary systems have been also experimentally determined to study effects of addition of NaF on the primary field of cuspidine. In order to discuss its thermodynamic stability the standard Gibbs energy of formation of cuspidine has been determined by an electromotive force method using CaF2 as solid electrolyte and a transpiration method as follows: The chemical potential diagram and constituent activities for the CaO-Si02-CaF2 system have been evaluated based on the obtained thermodynamic data.

Jan 1, 2003

By S. Peng, Vaughan R. Voller

"Free boundary problems are a common occurrence in materials processing operations. An important example is the filling of material into molds. This paper looks at filling problems associated with polymer processing, in particular Resin Transfer Molding (RTM) and Compression Molding. A general, single governing equation is developed which on numerical solution provides predictions for the position of the polymer front in the mold during filling. Both fixed and deforming finite element solutions are developed. Application to polymer filling test problems reveal that the fixed and deforming grid scheme are accurate and compare closely with each other.IntroductionProblems arising from the analysis of material processing operations often involve the tracking of a moving boundary, on which a balance conditions needs to be met, or the locating of a free surface that defines the solution domain. Material processing examples of so called ""free and moving boundary problems"" include; the tracking of solidification/melting fronts[l], the tracking of the metal/gas interface during the filling of a mold[2] and location and shape of a skull (freeze line) in a melting furnace[3].Computational solution of free and moving boundary problems usually fit into one of two classes, viz.1. Fixed grid scheme: In which the spatial domain is covered by a fixed grid (mesh) of node points and the solution uses an auxiliary variable (e.g. a local liquid fraction) to track the moving boundary or locate the free surface.2. Deforming grid scheme: In which the grid in the spatial domain is continuously deformed (or adapted in a steady state problem) such that a specified set of grid points lie on the moving boundary or the free surface.Details on the basic underlying features in these two classes of solution can be found in the excellent monograph by Crank [4]."

Jan 1, 1994

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By Min Chen, Lei Xu

Sintering behavior and performance of high alumina refractory based on the ternary subsystem MgAl2O4-CaAl4O7-CaAl12O19 were investigated using ZrO2 as an additive up to 8 wt.% by solid state reaction sintering. It was found that the added ZrO2 could dissolve in the CA6 grains in the form of a solid solution, which enhanced the isotropic growth of CA6 grains and then improved the sintering. As a result, the densification process was improved and areas with enrichment of ZrO2 showed a more compact structure. With further increase of ZrO2 addition, tetragonal ZrO2 were found to locate in the grain boundaries for exceeding the solid solubility limit, which enhanced the thermal shock resistance, indicating that addition of ZrO2 exhibited a positive effect on sintering behavior and performance of this refractory. In addition, it is considered that the optimal amount of ZrO2 addition was about 4% considering the performance together with the cost.

Jan 1, 2015

By B. Nebreda, I. Vegas, R. Vigil, O. Rodríguez, M. I. Sánchez de Rojas, M. Frías, R. García, J. Urreta

"This paper shows the possibility of reutilize paper sludge waste as supplementary cementing material for the cement manufacture. This industrial waste consists essentially of a mixture of organic matter (30%) and inorganic compound, such as calcite and clay minerals. The raw paper sludge does not present pozzolanic properties, but once calcined at 650ºC during 2 hours, exhibits high pozzolanic activity, similar to silica fume at 28 days, as a consequence of the transformation of kaolinite into metakaolinite. Calcined paper sludge was used as partial Portland cement replacements of 0, 5, 10 and 20%. Enhancement in compressive strength was appreciably obtained for 10 and 20% substitution levels from 7 days on. Furthermore, calcined paper sludge slightly reduces the initial and final setting times of cement paste. Introduction Natural pozzolanic materials have been ordinary used in different aspects of construction, mainly for their influence on the microstructure and durability of blended cement matrixes [1, 2]. Due to the regulations of environmental protection, many researches are focusing on the possibility of obtaining pozzolanic materials from industrial wastes and not from natural materials (ceramic wastes, silica fume (SF), activated clays) [3–5]. One of the most used pozzolanic products is the metakaolin (MK) obtained from the activation of natural clay (kaolinite). The positive effect that MK has on blended cement performances [6,7] and also the influence that curing temperature and matrix nature have on the reaction kinetics and stability of hydrated phases produced during the pozzolanic reaction, according to the studies carried out by Frías et al. [8,9] are well known. However, there is a worldwide trend towards the use of recycled products in cement industry. In this line, some authors have reported an alternative way of obtaining MK from waste paper sludge [10-14]. The raw paper sludge (PS), once calcined under controlled conditions (700-800ºC), produces a MK with pozzolanic properties [15-20]. The present research is part of an experimental study about alternative source for MK from the Spanish paper recycling industry and its use as supplementary cementing material. This contribution pays special attention to the option of reducing activation temperature below 700ºC. This fact has a positive effect in reducing the energy consumption, as well as in reducing environmental impacts associated with decarbonation of calcite. The chemical and mineralogical characteristics of raw paper sludge and derived calcined product are described. In addition, the influence and behavior on blended cement properties (setting times and mechanical properties) are also discussed."

Jan 1, 2008

By Jianguo Yin, Wenqiang Yang, Xiaoli Yuan, Juan An, Wentang Xia

Low grade iron ore with phosphorus (LGIOWP), a raw and wasted industrial solid material was used as an adsorbent to remove Pb(II) from wastewater. The effects of initial pH value, adsorptive time, initial Pb(II) concentration, adsorptive temperature and LGIOWP dosage on the Pb(II) removal efficiency were studied. The results show that the Pb(II) removal efficiencies exceed 99.4% and Pb(II) concentrations are less than 0.30 mg/L under the conditions of pH value 7.0, adsorptive temperature 50 oC, adsorptive time 30 min, initial Pb(II) concentration 100 mg/L, particle size <0.25 mm, adsorbent dosage 5 g/L and stirring speed 260 r/min. After Pb(II) removal reaction, the Pb(II) concentrations of wastewater completely accord with the requirement of national discharge standards of pollutants from lead and zinc industries (GB 25466-2010) (TPb= 0.5 mg/L) in China. Therefore, it can be concluded that LGIOWP is a new low-cost adsorbent which is suitable for the adsorption of Pb(II) from wastewater.

Jan 1, 2015