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By Wenbo Luo, Kang Liu, Jilai Xue

"Coal fly-ash(CFA) from thermal power plants is rich in Al2O3, which has great potential as an alternative resource for alumina production. In this work, Alz03 contained in the coal fly-ash was extracted using an acid sintering-leaching process. This process was enhanced by aid of power ultrasound during the leaching. The recovery rate of Al2O3 was increased with ultrasound, compared with the similar process without ultrasound under the identical operation conditions. Leaching temperature can be lowered by about 10-l5°C and the processing time reduced by about 50%. The process kinetics were investigated in details for a better understanding of the fundamentals on the effects of power ultrasound. The obtained results demonstrate the potential application in reducing processing energy and increasing production rate.Introduction Coal fly ash is a typical solid waste generated from coal combustion in thermal power station. Vast amount of CF A accumulation lead to serious environmental problems such as air and water pollution, cropland occupation, radioactive contamination, etc. However, CFA is rich in Al2O3 and SiO2 content, so that it has a potential use as recourses for alumina and silica production [1]. Aluminum industry, especially in China, has made a rapid expansion in recent years accompanying with a large amount of bauxite consumption, resulting a urgent demand to develop secondary alumina resources like CF A to maintain a sustainable development of aluminum industry that faces grim challenge [2].Acid leaching is an efficient technology to use in alumina extraction from CF A. Since the particle of CF A is not naturally existed mineral but was formed in molten state at high temperature, the internal Al-O-Si bonds are so strong to separate alumina from the ash particle. Because of this reason, the direct acid leaching [3-6] operated at ambient temperature has low extraction efficiency, approximate 30% to 40%, which is attributed to self inhibition effect from CaS04 generated by reaction between CaO and H2S04 [7-8]. High pressure leaching can efficiently decompose mullite to release A12O 3 content in the fly ash particles, but this requires autoclave material having strong acid corrosion resistance, high temperature (100°C-300°C) and pressure (1.0MPa-2.SMPa) resistance while its operating security is low and its acid consumption is large [9]. Concentrated acid boil process is conducted at near acid boiling point (200 °C - 300 °C) in 4 mouth flask wrapped by electric heating jacket with high mass ratio of acid and ash to achieve high Al203 recovery rate from CFA. Its disadvantages are similar to the high pressure leaching technology except no-pressure, and also the operating solution at nearly boiling point acid may easily spill and splash with additional acid loss and potential safety hazard [10]."

Jan 1, 2014

By C. Kathryn Sole

The close proximity of cobalt and nickel on the Periodic Table and their frequent occurrence together in nature means that their separation in primary hydrometallurgical flowsheets is not only often necessary, but requires the use of innovative chemistry to achieve high selectivity. Today, increasingly stringent demands for the high-purity cobalt and nickel salts required for battery applications in consumer electronics, electric vehicles, and solar applications are again challenging the state of the art. The evolution of cobalt–nickel separations is traced from the basic precipitation technologies employed in 1960s, through commissioning of the first cobalt solvent-extraction plant in South Africa in 1974, to the commercialisation of organophosphinic-acid extractants (which provided a step-change improvement in selectivity) and their eventual widespread use in the 1980s and ’90s. This was followed later by their sulphur analogue, which enabled different possibilities for laterite processing in the new millennium. Separations in chloride media, which take advantage of the different speciation chemistries, and nickel extraction by oximes in ammoniacal systems are also discussed. More recently, chelating and solvent-impregnated resins have added further dimensions to the possibilities for flowsheet design and enabled higher purity products to be attained from both primary and secondary sources. Selected case studies and flowsheets are described.

By Jingwei Lou, Bing Li, Suzhen Li, Miao Shen, Jianguo Yu

"As a main impurity in primary lithium metal, magnesium is difficult to remove because of the very close relative volatility of the two metals. Electrochemical refining provides a possibility to completely remove Mg in the LiCl-KCl melt prior to Li reduction. MgCl2 reduction processes in LiCl-KCl- MgCl2 melt were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), chronoamperometry and chronopotentiometry. Then potentiostatic electrolysis was carried out and Mg (II) ion was reduced onto a liquid lead cathode from the LiCl-KCl-MgCl2 melt at the Mg deposition potential. The results show that Mg ( II ) is reduced in one step with two-electron transfer. The reduction potential of Mg ( II ) was well defined. The reduction of Mg( II) results in Li ( I ) underpotential deposition at 0.2V more negative potential than that of Mg( II) reduction. Therefore, in order to prevent Li ( I ) from codeposition with Mg, accurately controlling Mg ( II) reduction potential during the potentiostatic electrolysis was necessary. Ninety three to 99 % removal rate of MgCl2 was achieved after 8-12 h electrolysis when liquid lead was used as cathode.IntroductionMetallic Li has been widely used in batteries, light weight alloys and in fusion reactors because of its excellent properties. Currently, the only way in industry to produce metallic Li is by electrowinning from molten LiCl-KCl at about 450 °C [l-5]. LiCl-KCl is the only electrolyte used, because they presents a lower eutectic temperature and KCl shows a slightly higher theoretical decomposition voltage than LiCl, as shown in Table l .The produced metallic Li generally contains 1-2 wt% impurities including Na, K, Al, Ca, Mg, Si, etc. [6l, which are derived from the corresponding metal chloride compounds or metal oxide compounds existing in the LiCl and/or KCl raw materials. These impurities have to be removed by subsequent vacuum distillation at high temperatures to meet the requirements for metal Li purity in the final products. Separation of Mg from Li by vacuum distillation is difficult because their relative volatilities are very close, as shown in Table 2."

Jan 1, 2011

By Robert E. Moore

Synthetic spinel is proving to be a highly effective refractory for specific applications, but its cost limits applications. Formation of spinel from a raw material such as diaspore or bauxite could provide a simple and less costly starting material. In the study reported here, finely ground (-325 mesh) diaspore from Missouri and bauxite from Guyana and China are combined with hard burned MgO (-325 mesh) in appropriate proportions to yield spinel and spinel with secondary phases. A classical sintering and dilatometer study was completed, followed by a microstructure study to determine completeness of the reactions and morphologies of the reaction products.

Jan 1, 1993

By A. Dadgar

The adsorption kinetics of AuBr4 on Dowex ® -21K ion-exchange resin were studied and found to be independent of the initial gold, bromine, and base metals concentrations. A commercially-available undivided hypochlorite generating cell was used to generate bromine from simulated mixed halide (Br-/CI-) solutions. Electrolyses were performed with solutions containing very low Br' ion concentrations. The current efficiencies were 80-90%, and Br- ion utilization was maximized. A detailed economic assessment was made considering the capital and the operating costs for a 1000 mtpd gold ore processing plant. The toxicity and discharge levels of bromide, bromine, and cyanide were compared from a detailed analysis of the published literature data. Comparing bromine vapor with hydrogen cyanide gas for a given length of exposure, the lethal concentration of bromine is about 3 times less than hydrogen cyanide. The toxicity of sodium bromide is similar to that of sodium chloride. Acute poisoning to bromides and chlorides is rare because of their low toxicities. The allowed discharge levels of Br-, Br2, and CN- in fresh water are 250, 0.1, and 0.005 mg dm-3, respectively.

Jan 1, 1992

By Dong Hoon Han

The sulfation rates of magnesium oxide and calcium oxide (molar ratio 7:3) contained in calcined CMA ( calcium magnesium acetate) by SO2 were measured. The experiments were carried out in the temperature range 700 to 1100 °C and under the SO2 concentrations of 0.3 to I mol % (5 % 02). In the low-temperature range below 830 °C the reaction produced CaSO4.3MgSO4 and unreacted MgO, but no MgSO4 phase. The formation of CaSO4.3MgSO4 phase has a significant implication in that it allows the utilization of MgO for SO2 removal whereas the sulfation of MgO from conventional sources is so slow that it is of no practical interest. Thus, the calcined CMA can remove SO2 at lower temperatures than conventional SO2 absorbents and at a greater capacity. Above 950 °C only CaO reacts with SO2, but at a much greater rate than the calcined Ca(OH)2, which is one of the most reactive SO2 absorbents.

Jan 1, 1998

By Ahmad-Bitar¸ Riyad N., Shadia J. Ikhmayies

"CdSi-xTex thin films with O<x<0.3 were prepared on glass substrates by the annealing of CdS:In thin films produced by the spray pyrolysis technique. The annealing was performed in nitrogen atmosphere at 400 --,C in the presence of Te vapor. The compositions of the films were determined by energy dispersive X-ray detection (EDAX) measurements. Scanning electron microscopy (SEM) was used to investigate the morphology of the films. The transmittance of the films was measured at room temperature in the wavelength range 400-1100 nm and used to produce the absorbance of the films. The first derivative of the absorbance was used to estimate the optical bandgap energy Eg by using the minima in the first derivative. The relation between the bandgap energy and the fraction x was found to fit with a parabola and bandgaps in the range 2.196: =Eg: =2.480 e V were obtained. Urbach tailing in the bandgap was also investigated.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The fabrication process of these cells involves the deposition of a p-type CdTe absorber layer on top of an n-type CdS one which acts as a window. The efficiency of the solar cell is affected by the method of preparation of both layers [1, 2].Interdiffusion processes taking place at the CdS/CdTe interface have largely been realized to significantly affect the device performance [3] by changing the bandgap of both CdTe and CdS which modifies the spectral response of the solar cell [ 4]. The formation of a mixed crystal or a graded layer causes a reduction in the lattice mismatch at the CdS/CdTe junction [5] which is about 9% [ 6] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [7, 8]. A complete understanding of the properties of the intermixed layers CdSxTe1-x that usually constitutes the interfacial region in the CdS/CdTe solar cell is essential. According to our knowledge, a lot of research was devoted to the investigation of the diffusion of S into CdTe [3-5, 9]; but little on the direct investigation of the diffusion of Te into CdS [6]."

Jan 1, 2011

By R. J. Kuczynski

The U.S. Bureau of Mines operated a 2,000-9 (4.4-lb) batch process development unit for recovering platinum-group metals (PGM) from automobile catalysts. Virgin monolith, used pellet and used monolith catalyst samples were tested. Leaching twice with 1-pct sodium cyanide (NaCN) solution at 160&apos; C for 1 h in a pressure vessel dissolved over 95 pct of the PGM from virgin catalysts and over 90 pct from used pellet catalysts. Over 85 pct of the PGM was dissolved from used monolith catalysts when a third leaching step was added. PGM concentrates as metallic powder containing over 99.8 pct of the dissolved PGM and analyzing greater than 70 pct PGM were recovered by heating the pregnant leach solutions from virgin catalysts to 250&apos; C and used catalyst to 275" C for 1 h. The solution after heating contained primarily sodium carbonate from cyanide decomposition and less than 0.2 ppm total cyanide.

Jan 1, 1993

By Hong Li, Chenxiao Li, Wenwen Mao, Hua Lu

Directly charging limestone into slag in BOF is a newly emerging technique which broke through the traditional BOF slagging principle. It is necessary to study the decomposition behavior of limestone in converter slag during BOF steelmaking. FeOx, SiO2, MnOx and pre-melting slags were mixed with limestone according to different quality proportion to simulate the environment of limestone in converter slag. TG-DTA results indicated that slag with individual component, including FeOx, SiO2 and MnOx, all had obvious effects on reducing the decomposition temperature of limestone. Pre-melting slags with multiple components had further reducing effects than individual component. XRD results showed converter slag component would react with decomposition product of CaCO3 and generate solid solution or oxide, reducing the activity of CaO and the decomposition temperature of CaCO3.

Mar 1, 2017

By Nagahiro Saito, Takashi Nishimura, Takamichi Ichikawa, Akio Fuwa

"Yttria-stabilized zircohia (YSZ) has high potential to be used as solid-oxide fuel cell (SOFC) electrolyte. However, the high efficiency of SOFC has not been yet achieved due to the high internal resistance of bulk electrolyte. The resistance becomes lower with the decrease in the electrolyte thickness. Thus, the decrease in electrolyte thickness leads to lower internal resistance. . The aim of this study is as follows: (a) to prepare the thin films of YSZ by inductively-coupled RF plasma-enhanced metal organic chemical vapor deposition (PEMOCVD) process using Zr(t-OC4H9)4,Y(DPMh and oxygeil, and (b) to reveal the relationship between the structural characterizations and the process parameters.1. IntroductionYttia-stabilized zirconia (YSZ) has, been widely used as not only heat-resistant materials but also the components in automotive oxygen sensors, electrolytes of solid-oxide fuel cell (SOFC)(1)(2) and the buffer layers for the high-temperature superconductor because of its low thermal conductivity, good mechanical properties and high ionic conductivity. However, it is said that the internal resistance of the bulk electrolyte is too high to be appropriate as a solid electrolyte for high-efficient SOFC. The authors believe that the thin YSZ electrolyte can give a high performance to characteristics SOFC, since the internal resistance becomes lower with the decrease of electrolyte thickness. Thus the process technology to prepare YSZ thin films is desirable and must be established.In recent years, the YSZ thin films have been reported by chemical vapor deposition (CVD), thermal CVD using metal chlorides (MC) of ZrCl4 and YC(3)(4), thermal CVD using metal organic compounds (MO)(5)(10) Zr(t-OC4H9)4 and Y(C11H19O2)(11) and plasma-enhanced (PE) CVD using MO. Here, these methods are called MCCVD, MOCVD and PEMOCVD. MCCVD has two disadvantages; a large quantity of chlorinated impurities in deposited films and high processing temperature (> 1273K). This high processing temperature leads to damage of substrates in particular, so the application of this technology is limited. On the other hands, the processing temperature by MOCVD becomes and is lower. Unfortunately, the accurate vapor pressures of these metal organic compounds have not been, known so: that it is difficult to control the composition and the film thickness by MOCVD method well. Moreover, the large amount of carbonic compounds in the films prepared by MOCVD method is produced. However, plasma-effect has been reported to decrease large amount of the carbonic impurities by PEMOCVD. However, PEMOCVD has many reaction parameters in plasma processing; the geometry of experimental apparatus, radio frequency, electronic power input and so on. Thus, the general understanding about the relationship among reaction parameters, the composition and crystal structure of thin deposit film by this method has not yet been established."

Jan 1, 2000

By Carl A. Kuehn

At Carlin, Nevada, non-indigenous hydrocarbons were introduced as a bitumen phase which was mobilized due to burial under the Roberts Mountains allochthon. similarly, some indigenous organic matter was locally mobilized. Fluid inclusion and paragenetic data of veinlets formed during this hydrocarbon stage, combined with quantitative modelling or organic maturation, indicate that host rocks had evolved past dry gas conditions of around 1550 and l.l+0.2 Kb in the presence of CH4-saturated, highly saline brine by no later than early to middle Cretaceous time. All hydrocarbons present would have been rendered immobile under these catagenic conditions. Crosscutting relationships at several scales suggest that hydrocarbon mobility may have ceased prior to the intrusion of a series of dikes in the mine which have subsequently been altered and mineralized. Apart from subsequent oxidation, the current distribution and high maturity of carbon-rich zones were established prior to gold introduction. No Evidence has been found supporting proposed hydrocarbon "remobilization" during or after gold mineralization and alteration. The high density of the CH4-bearing fluid requires formation at high pressures (near 1 Kb) and precludes their formation as a result of the "cracking-off" of CH4 from organic matter during a thermal event associated with a shallow hydrothermal system. The density and composition of the fluid inclusions restricted to the early hydrocarbon-stages of the Carlin paragenesis are not unique to the sediment-hosted gold deposit environment of north-central Nevada. Similar inclusions are found in authigenic quartz crystals from Paleozoic carbonaceous shales in central Pennsylvania which have experienced normal metagenesis of indigenous organic matter due to deep burial.

Jan 1, 1987

By Toshiyuki Hashida, Victor M. Lopez-Hirata

"Small-punch tests and determination of fracture toughness JIC were conducted at 4 and 77 K on new cryogenic JN1, JJ1 and JK2 austenitic stainless steels, after isothermal aging. Equivalent fracture strain ?qf determined by measuring the reduction of thickness in the small-punch test specimen. A linear dependence of JIC on ?qf was found in these new materials. Regression analysis of experimental data produced the following linear relation JIC = 1304.1 ?qf + 8.09 [kJm-2]. An analysis of present work relation was pursued on the basis of material properties and evaluation method of he. Results showed that the slope value has a strong dependence on material yield strength and JIC evaluation method. This linear relation is useful for the evaluation of fracture toughness JIC, measuring the equivalent fracture strain ?qf by means of small-punch test. Thus it can be useful for assessing the degradation of fracture toughness in small areas such as, the heat-affected zone in welded components.IntroductionCryogenic structural materials for superconducting magnets of fusion nuclear reactor are required to possess a good combination of strength and toughness. The mechanical properties are required beyond the capability of conventional austenitic stainless steels [1]. New cryogenic JN1, JJ1 and JK2 austenitic stainless steels were developed by the Japan Atomic Energy Research Institute (JAERI) [1]. The structure of superconducting magnets is constructed by welding of 200 = thick plates of these steels, which are solution treated at high temperatures and then water-quenched to avoid intergranular precipitation. However, the welding process involves heating and cooling [2], which cause microstructural changes in both base metal and weld. In this heterogeneous microstructure, it is important to estimate the fracture toughness of these materials at cryogenic temperatures. Therefore, it is necessary to evaluate the effect of aging process on the fracture toughness behavior of these new steels. To determine the cryogenic fracture toughness, the elastic-plastic JIC value has been co=only used [2]; however, the specimen size is much larger than heat-affected zones in welded components. Small-punch (SP) testing method, employing miniature specimens, has permitted to evaluate the fracture toughness behavior at different temperatures in different nuclear reactor materials [3,4]. Mao et al. [5,6] and Misawa et al. [7] found a linear relation between JIC value and equivalent fracture strain ?qf, determined by SP method in non-ferrous alloys and ferritic steels at room temperature and austenitic stainless steels at 4 and 77 K, respectively. So that, this kind of correlation would be very useful to assess the fracture toughness JICe values by means of SP test in small zones of welded components."

Jan 1, 2012

By Xiaobing Yang, Animesh Jha, Greg Doughty

"Successful use of inert anodes should reduce the CO2 footprint in aluminum production. The search for a “holy grail” inert anode for metal electro-winning from constituent oxides using molten salt bath as an electrolytic medium is continuing. In this article we demonstrate the engineering approaches for the fabrication of intermetallic anodes, based on a quaternary Al-Ti-Cu-M (M:Ni, Fe) system for primary aluminium production. In particular, we examine the microstructural and electrochemical properties of alloys, based on the quaternary compositions. We explain the aspects of phase stability under anodic potential, which leads to the loss of anodic materials in the temperature range of 850-1050oC. The results are analysed in the context of oxidation reaction and formation of oxide layers which readily dissolve in the cryolite melt and prevent passivation. The paper also describes the conditions under which the reduction of aluminium at the graphite cathode occurs which also strongly depends on the molten salt chemistry for the nucleation of molten aluminium at the cathode.1. IntroductionOxygen-evolving inert anodes are an alternative to the conventional consumable carbon anodes for the production of primary aluminium. In this paper the materials selection criteria chosen for the engineering of anode is based on the understanding of the thermodynamic stabilities of aluminide intermetallic phases, some of which are formed and remained stable in fluoride melts. For example, the formation Al3Ti dispersed in aluminium metal via molten-fluoride flux reaction is well known in the context of aluminium casting and grain refining [1-3]. It is for this reason in our research we concentrated on the engineering of stable intermetallic phase mixture in the Al-Ti-Cu ternary system, shown in Figure 1 [4]. In this figure two compositions in the Al3-0.5zTi1-0.5zCuz family are shown with the substitution of 7 atomic % and 11 atomic % copper. However initial investigations showed that these two compositions were unsuitable due to the formation of low-temperature liquid (~540oC) and intermetallic phase, Al2Cu along the Al-Cu binary edge during solidification. The Al2Cu phase segregated along the boundaries of Al3Ti and Al5Ti2Cu, and dissolved away when electrolysis was carried out using these anodes above 800oC. The presence of consequential porosity in the anode material increased the corrosion of the alloy through local heating due to high current density at 0.8 A cm-2. The early tests were carried out with cryolite melts, shown in Figure 2, having 3 weight percent of Al2O3 in the bath at 850oC."

Jan 1, 2010

By Seref Sonmez, Onuralp Yücel, Kagan Benzeşik

The aim of this study is processing of domestic molybdenum concentrate to produce technical grade molybdenum trioxide may be the starting material for the production of various molybdenum products. In order to determine the optimum parameters for the total oxidizing roasting process of molybdenite concentrate to produce MoO3 and purify the MoO3 product by removing the copper content; first, MoS2 was roasted by controlling reaction temperature and duration in a chamber type furnace. The highest Mo concentration rate was obtained as 56.6 wt% of Mo at 650 °C for the roasting duration of 45 min. Secondly, roasted product was leached with H2SO4 to remove copper. Leaching conditions were optimized by investigating the effects of different H2SO4 concentrations and S/L ratios. The minimum copper content was obtained as 0.13 wt% at leach residue. The raw materials and the products were characterized by using AAS (atomic absorption spectrometry) and XRD (X-Ray Diffraction) techniques.

Mar 1, 2017

By G. Glinski, K. A. Pericleous

"Recent advances in new computational modelling techniques such as Lattice-Boltzmann and Dissipative Particle methods offer the prospect of simulating complex fluids such as colloidal and dense suspensions in industrial processes. They are referred to as mesoscopic methods since they lie between molecular dynamics at a microscopic atomistic scale «lO-9m) and traditional macroscopic CFD methods (> 1O-2m). The models behave like a 'coarse-grained' gas consisting of fictitious interacting particles, which are much larger than the real molecules of the actual fluid they represent. Inter-particle forces are set so that the collisions collectively mimic the phenomenological transport properties and flow of the underlying fluid at a macroscopic scale.Much of the developmental work to date has focused on laying theoretical foundations based on thermodynamic and kinetic theory. Successful applications include predictions of macroscopic transport properties of complex fluids and flows in porous media and filters. With the constant increase in computational power, these mesoscopic methods are now sufficiently developed to determine their suitability to simulate complex fluid flows in real industrial processes. This work describes the application of meso scopic methods to the stencil printing of solder pastes in the assembly of electronic components. The aim of this work is to assess the ability of these methods to study the transport mechanisms of individual solder particles suspended in the flux solvent as they enter and fill the micro-apertures of a stencil. This paper demonstrates the coupling of such mesoscopic methods to continuum CFD methods to predict the flow of dense suspensions (i.e. solder paste) in industrial processes."

Jan 1, 2001

By Zhucheng Huang, Zhikai Liang, Ronghai ZHONG, Lingyun Yi

In this work, research of reduction process was studied by means of rotary kiln (u1.5 m /C215 m) process anatomy in order to provide fine guidance to large-scale operation. It was shown that the average reduction degree of 89.96% and metallization ratio of 85.15% were obtained at the highest temperature of 977°C and total residence time of 90 min. The generation amount of metallic iron in section of temperature higher than 900°C and lower than 900°C was 34.15 and 56.38%, respectively. The section of lower temperature of 830–900 °C played an important role in formation of metallic iron, making it possible for mini-pellet to reduce quickly at lower temperature. Two main tasks were completed for mini-pellets in rotary kiln: the reduction of iron oxides in the range of 15.0–4.5 m as well as migration and bene ficiation of metallic iron, facilitating the subsequent separation of iron and gangue minerals.

Mar 1, 2018

By J. Rajesh Kumar

The extraction equilibrium study of tetravalent platinum was carried out using tri-octyl/decyl amine (Alamine 336) and bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302) in kerosene from hydrochloric acid media to investigate their extraction capacity, since they have different donor atoms, ?N? and ?S?. Their distribution equlibria were studied as a function of acid, extractant, diluents and temperature. The title metal shows the inverse behavior at higher acid concentrations. Extraction of tetravalent platinum increases with increase of extractant concentration. The plot of log D vs. log [Extractant], mol.L-1 is linear with slopes 1±0.3, indicating the association of one mole of extractant with the extracted metal species. Stripping of metal from the loaded organic (LO) with mineral acids and bases such as hydrochloric, sulphuric, nitric acids and ammonia, hydrogen peroxide, sodium hydroxide, thio- urea were studied. Regeneration and recycling capacity of Alamine 336/Cyanex 302 and extraction behavior of associated elements was also studied.

Jan 1, 2009

By Jian Li, S. Penttilä, P. Liu, W. Zheng, C. Bibby

"The materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. The current Canadian pressure-tube supercritical water (SCW) concept design requires core outlet temperature of 650 °C at 25 MPa with peak cladding temperature reaching as high as 850 °C. Aside from oilier challenges, there is currently very limited data on candidate stainless steels' corrosion resistance under this operating condition. Austenite stainless steels that include 316L, 304H, AL6XN and 3 l0S that cover a wide range of Cr contents are promising candidates for either direct in core applications or as base coating materials. However, their corrosion resistance has not been tested systematically under this stringent condition. In this study, these types of stainless steels are tested, and their corrosion resistances are compared.IntroductionThe Canadian pressure-tube supercritical water (SCW) concept will operate at a core outlet temperature of 650 °C at a pressure of 25 MPa, with potential peak cladding temperature reaching as high as 850 °C. High-temperature corrosion resistance is one of the key design requirements for fuel cladding components. As summarized by Allen [1 ], most testing to date has been carried out at temperatures below 730 °C. To date, SCW corrosion data above 600 °C is very limited. Even at relatively low temperature exposure to SCW (e.g. 500 °C), F/M steels develop a thick oxide layer rapidly, while some austenitic stainless steels develop thinner surface oxide. Ni based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of intermetallic precipitates [2-5]. Dissolution of major alloying components from all of these alloys could also pose significant problems for downstream piping [6]. Kaneda et al. [7] suggested some modified stainless steels provide better SCW general corrosion resistance, with no sign of SCC under the slow-strain rate test.Cho [8] suggested that as the Cr content increase, general corrosion resistance improved at 510 °C and 25 MPa. However, similar to Cho's work, most of the SCW corrosion resistance assessments were based on weight change measurement. This can be unreliable due to potential exfoliation of thick oxide film. Besides, there have been no systematic SCW corrosion resistance tests for candidate stainless steels under higher temperatures. SCW corrosion rate increase dramatically for alloys tested at 600 °C [1]. It is also important to understand the role of major alloying elements under this stringent operating condition, not only for fuel cladding components' materials selection, but also for coating materials development."

Jan 1, 2013

By Y. Huang, P. B. Prangnell

"An Al-0.1Mg alloy was firstly deformed at room temperature by ECAE to a true strain of 10, where a steady state deformation was established and further processing had little effect on grain refinement. The ECAE samples, with an average grain size of ~0.55µm, were then compressed in a channel die at 77K- 473K to various reductions. Microstructures were characterized by electron backscatter imaging and EBSD in a FEGSEM. Grain refinement to the ECAE submicron structure occurred during deformation at cryogenic temperatures of 77 – 213K, whereas coarsening took place during deformation at elevated temperatures. A steady state deformation was observed at all temperatures where a constant grain structure was developed and maintained upon further straining due to dynamic recovery. The mechanisms of dynamic recovery during steady state deformation at cryogenic temperatures are discussed.IntroductionSevere deformation processing (SDP) has been successfully used to produce submicron grain structures, and in some cases nano-scale crystallite sizes, in a wide range of alloys. However, the rate of grain refinement becomes increasingly inefficient at high strains as a steady state grain structure is approached [1-3]. Steady-state grain sizes have also been reported in other ultra-high strain deformation processes, like cryogenic ball-milling [4]. There is thus a minimum grain size achievable in a material by a given SPD process under constant deformation conditions.It is well documented that a steady state subgrain size is observed in warm deformation of metals due to dynamic recovery (e.g. [5]). In severely deformed alloys a constant grain size at ultra-high strains has similarly been attributed to dynamic recovery [1-3]. Mechanisms have been proposed, for rapid deformation induced grain growth including stress driven boundary migration and breakaway from solute pinning [2]. However, as pointed out by Humphreys et al. [2] the restoration processes are currently poorly understood, particularly at low temperatures, where the boundary migration rates required to maintain a constant grain size are orders of magnitude higher than can be satisfactory explained from diffusion controlled migration. Similar to the subgrain size, the steady state grain size obtained during SDP is generally related to the temperature compensated strain rate [2, 6]. Thermally activated restoration processes are thus expected to be suppressed by lowering the deformation temperature and a smaller steady state grain size can be achieved."

Jan 1, 2012

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016