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By Wei Yu, Tiejun Chun, Jian Pan, Deqing Zhu

In this paper, the technology of producing fluxed pellets by using hydrated lime as binder instead of bentonite was carried out. Green balls with 0.8% bentonite and others with 2% hydrated lime were obtained under the same conditions of 1.5% coke, 1.45 basicity and balling at 8.5% moisture for 13 min in disc pelletizer. The properties of two types green balls were as follows: drop numbers of 4.8 to 5.0 times/0.5m, compressive strength of 19.7 to 24.2 N/pellet and thermal shock temperature of 280 to 385?, respectively. Comparing with bentonite as binder, the compressive strength of fired pellets with hydrated lime is elevated by 13.8% and climbs up to 3113 N/pellet under the following conditions: preheating at 1050? for 10 min and firing at 1300? for 15 min. The hydrated lime also improves the metallurgical performance of fired pellets. The reduction index was enhanced from 68.6% to 70.6%, RDI+3.15 increased from 90.1% to 98.8% and reduction swelling index dropped from 22.4% to 7.4%, respectively. Therefore, hydrated lime can not only replace bentonite as binder to enhance the firing behaviors of green balls, but also effectively improve the metallurgical performance of fluxed pellets which can be used as high quality feed for blast furnace.

Jan 1, 2011

By Xiaodi Huang, Matthew Andriese, Zheng Zhang, Jiann-Yang Hwang, Zhiwei Peng

"A simplified finite-difference time-domain (FDTD) algorithm for modeling microwave propagation in magnetic dielectric materials was developed and employed to study the microwave dissipation in magnetite. Heat transfer during microwave heating of magnetite was subsequently investigated by solving heat transfer differential equation using explicit finite-difference (EFD) method. It is observed that temperature of magnetite surface increases rapidly in the first minute due to the rapid strength decays in both electric and magnetic fields within a short distance along the path of microwave dissipation. A temperature peak, initially formed at the surface of the sample slab, migrates inward as heating time extends and microwave power increases.IntroductionAs one of primary materials in iron and steel industry, magnetite exhibits excellent microwave absorption capability, which leads to great energy conservation in microwave assisted steelmaking [1,2]. The fast temperature increase in microwave heating of magnetite can be attributed to both dielectric and magnetic losses [2]. Although much experimental work has confirmed this observation, detailed computational studies for modeling of microwave field dissipation in magnetite at commonly used frequencies, such as 915 MHz, has not been well addressed [1,3].Finite-difference time-domain (FDTD) method is widely used in computational electrodynamics modeling to simulate the dynamics of electromagnetic wave scattering from various media [4,5]. This approach requires modeling algorithm to be formulated with integration of specific characteristics of each medium. An extensive literature survey indicates that current formulations are only suitable for modeling electromagnetic waves propagating in normal dielectric lossy materials [5,6]. Since magnetite is a magnetic dielectric material in which both dielectric and magnetic properties contribute to the heating process under microwave irradiation, a specific algorithm should be developed for the simulation."

Jan 1, 2012

By A. Jakobsson

Studies of the rate of interdissolution in oxide systems in the solid state are of importance in materials processing through the powder-metallurgical route. As there is a need for following the rate of the such reactions continuously, a new method based on high temperature X-ray diffraction was developed. Mechanical mixtures of the oxides were placed in a high-temperature X-ray diffraction unit and the changes in the intensity and position of the peaks with highest intensity for both the components were followed as functions of time. A suitable theoretical model has been developed in order to interpret the experimental data and evaluate the diffusion coefficients. The method was applied in the case of the system MgO-NiO. The results obtained are compared with those obtained by another new method, based on solid-state galvanic cell technique with calcia stabilized zirconia electrolyte, developed in the Department of Theoretical Metallurgy. The advantage of the present techniques to monitor the progress of the reaction continuously make them suitable for computer control of such processes.

Jan 1, 1995

By KAGAN BENZESIK, Onuralp Yücel, Mehmet Bugdaycı, Ahmet Turan

ZrB2 and B4C are one of the most significant advanced ceramics. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, Carbon black, B2O3 were used as starting material to produce ZrB2-B4C powders by SHS. Also Mg powder was used as the reductant. The reaction mixtures (approximately 100 g) were mixed thoroughly 15 minutes in a turbula mixer and charged into Cu crucible and compacted. W (tungsten) wire was placed at the top of copper crucible and the reaction realized by passing current through the wire. After initiation, a highly exothermic reaction became in a self-sustaining mode and propagated throughout the SHS mixture. The samples were characterized by using AAS and X-Ray Diffraction.

Jan 1, 2016

By Milorad Cirkovic, Mile Bugarin, Vlastimir Trujic

"Industrial scale testing was performed in the plant-site of Bor Company. Charging sample was from 4-5 tons for each particular test. All operations in industrial scale investigations were carried out in one furnace. For the aim of successful realization of experiments, and primarily for safety and prevention the risk of toxic contamination the working environment, a plant was designed and constructed for cooling and wet dedusting of gases formed during smelting process, zinc removal and flame refinement of molten metal. For the requirements of industrial investigations a complete plant for cooling and wet dedusting of gases has been constructed for brass scrap processing. In this plant, the original ultra-sonic water spraying devices have been installed. The efficiency of such simplified system for gas treatment has been 98,6%. Introduction Permanent development of techniques and technology causes formation the considerable quantities of secondary raw materials that are much more relevant as the raw material base for many metals. Due to a fact that large quantities of metal, are concentrated in the waste materials, large consideration is given to this topic, and numerous technologies for this waste recycling are developed in the world nowadays. High energz price and permanent increase of metal price on the world market have made that secondary raw material tretament, for the aim of various metals production, becomes more and more relevant in the world. In comparison of metal production using enrichment and metallurgical treatment of primary raw materials, the non-ferrous metals production from secondary raw materials has a range of advantages, as well as: - Low level of capital investments, - High technological recovery of qualitative secondary raw materils, - Considerably low consumption of energetic resources regarding to the treatment of primary raw materials (ore and concentrate), - Reduced consumption of unrecoverable mineral resources, - Reduced enviroment pollution [1,6]."

Jan 1, 2008

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, F. G. Hampel, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides can be incorporated for use as a transmutation fuel. The current study involves characterization of precursor powders and pellets destined for the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of minor actinide mixed oxide (MAMOX) with oxygen to metal ratios (O/M) of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders were characterized using a field emission gun scanning electron microscope (FEG-SEM) to determine particle morphology, size, and size distribution. An electron probe microanalyzer (EPMA) was used to characterize element distributions in the pellets.IntroductionThe fundamental purpose of GNEP is to enable a fuel recycling partnership between member nations. The customer nations utilize the fuel for electricity generation provided by and subsequently recycled by the supplier nation. The supplier nation recycles the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials are strictly controlled through the International Atomic Energy Agency. One of the thrust areas supported by the GNEP program is the development of actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3].MOX fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition into which minor actinides can be incorporated for use as a transmutation fuel [4]. Irradiation performance data on oxide fuels with high concentrations of minor actinides is limited, which has prompted this study. This paper discusses the characterization results of precursor powders and pellets prepared for the Advanced Test Reactor in Idaho to determine the effects of including minor actinides in the fuel, and addresses two fuel test matrices proposed by Hilton et al. [3]. The pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of MA-MOX with O/M of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders, uranium oxide (depleted, DUO2 and highly enriched, HEUO2), neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a FEG-SEM for particle morphology, size, and size distribution. The morphology of the actinide powders was studied in the areas of flowability and porosity in order to predict manufacturability. The MOX pellets were characterized using an EPMA in order to determine impurity levels and locations."

Jan 1, 2008

By Mojtaba Ahmadiantehrani

A previous study showed that up to 80% gold extraction could be obtained with 160 lbs/ton hypochlorite consumption at ambient temperature from a low grade Carlin-type carbonaceous ore. Crushing the ore to a finer size and agglomerating with cement decreases hypochlorite consumption by 60%; while, agglomeration and curing the cement-ore mixture with hypochlorite solution has no significant effect on total gold extraction. The high hypochlorite consumption is due to oxygen depletion as the solution percolates through the column, i.e., oxidation of gangue materials. These side reactions are reduced at sub-ambient temperatures resulting in a substantial further decrease in hypochlorite consumption. The optimum temperature range and additional reduction of hypochlorite consumption by introducing the reagent into the column at different elevations will be discussed.

Jan 1, 1992

By Baozhong Zhao

Experimental results have shown that fluxing with soda ash (Na:zC03) can remove As and Sb from molten copper at the rate of As>Sb, but is relatively ineffective in removing Hi. The rate of impurity removal is controlled by impurity mass transfer in the metal phase. In this paper, a mathematical model was developed to describe the impurity removal phenomena. The model incorporates the effects of molten bath mixing intensity, soda ash feeding rate, oxygen content in the molten copper and soda ash fluxing by surface addition and injection. The model predictions are in good agreement with experimental results and may be used in designing large scale tests.

Jan 1, 1996

By M. Brian Maple

A rich variety of phenomena are produced by superconducting-magnetic interactions in rare earth and actinide compounds. These phenomena, and the materials in. which they have been observed, are described in this talk, with an emphasis on the new high superconducting transition temperature (Tc) copper oxides. The Materials The-materials in which these phenomena occur can' be divided into two classes. In the first group, there are two distinct interpenetrating systems of electrons, a set of localized 4f or 5f electrons and a set of itinerant electrons. The localized f electrons carry magnetic moments and interact with the spins and momenta of the the itinerant electrons, which are involved in the superconductivity, via exchange and electromagnetic interactions; respectively. This category includes materials containing rare earth (R) and actinide elements with partially-filled f electron shells which have been inroduced as substitutional impurities [e.g., La1-xCexA12, Th1-xUx] or form a sublattice in compounds [e.g., RRh4B4, RMo6S8, RMo6Se8, the high Tc. superconductors RBa2Cu3O7-d(d - 0.05)]. Materials of the second type are characterized by a single band of electrons that is responsible for both superconductivity and magnetic order. This group includes heavy electron rare earth and actinide compounds [e.g., CeCu2Si2, UBe13, UPt3, URu2Si2], and the high Tc copper oxide superconductors such as the hole-doped systems Lag- MxCuO4 (M = Ca, Sr, Ba, Na) and RBa2Cu3O7-d(0 =d= 1) and the electron-dope system Ln2-xMxCuO4-y (Ln = Pr, Nd, Sm, Eu; M = Ce, Th; x = 0.15; y - 0.02).

Jan 1, 1992

By Elsa Olivetti, Randolph Kirchain, Gabrielle Gaustad

"As scrap usage increases, it is often necessary to “dilute” the melt with primary aluminum to ensure the finished product meets compositional specifications. Secondary raw materials, particularly postconsumer scraps, often include high levels of unwanted or “tramp” elements, such as iron and silicon in the case of aluminum. Recent literature on this issue cites several causes including inherent contamination during processing as well as ineffective segmentation at end-of-life. To address this accumulation problem, “upgrading” solutions have been developed including: dismantling of end-of-life products, spectrographic or magnetic sorting of shredded scrap, and “filtration” technologies that remove tramp elements in the melt. Although it is clear that upgrading strategies enable increased usage of scrap, it is not clear that they would be economic or efficient. This work presents a set of analytical methods, based on chance constrained optimization, to quantify the potential environmental and economic value of several scrap upgrading technologies.IntroductionAluminum recycling has a number of key environmental and economic benefits. Compared to other materials, aluminum production has one of the largest energy differences between primary and secondary production: 175 MJ/kg for primary compared to 10-20 MJ/kg for secondary[1]. With energy and cost savings in mind, many producers now have targets of increasing their usage of secondary materials[2, 3]. However, the accumulation of impurities in these recycled material streams provides a significant compositional barrier to these goals[4].A growing number of studies and literature would suggest that accumulation of unwanted elements is a growing problem, in all recycled material streams. In the case of aluminum, the list of problematic impurities is quite large, including but not limited to: Si[5, 6], Mg, Ni, Zn, Pb, Cr[7], Fe[5-7], Cu[6, 7], V, and Mn[6]. Metals recycling is a metallurgical process and is therefore governed by the laws of thermodynamics. The removal of unwanted elements in the scrap stream is dictated by the energy considerations of the melt process. Compared to many metals, aluminum has a high degree of difficulty in the removal of tramp elements, due to thermodynamic barriers. Therefore, with no simple thermodynamic solution, producers must identify strategies through-out the production process to mitigate this elemental accumulation."

Jan 1, 2008

By Hojat Naderi

In this research assisted leaching of chalcopyrite using sodium peroxodisulfate was studied. Electrochemical techniques such as Tafel analysis and electrochemical impedance spectroscopy (EIS) were used to investigate the surface reactions of a chalcopyrite electrode in the presence and absence of Na2S2O8. According to the results, addition of sodium peroxodisulfate increases the current exchange of the corrosion process and prevents the formation of a passive layer on the surface of the electrode. EIS tests show the trans-passive dissolution of the passive layer on the chalcopyrite electrode in presence of Na2S2O8. Equivalent electrochemical circuits were modeled for Na2S2O8-free and -containing solutions and the model parameters were compared to determine the effect of S2O8 2− on chalcopyrite dissolution. Copper dissolution from pure chalcopyrite mineral and chalcopyrite concentrate was carried out using 15 g/L sulfuric acid solution with and without Na2S2O8. Simultaneous presence of 10 g/L ferric ion and 40 g/L peroxodisulfate salt results in about 40 and 18% of Cu extraction from chalcopyrite concentrate and pure chalcopyrite mineral, after 96 h, respectively.

By A. M. T. S. Bandara

The solubility of rare earth (RE) salts in aqueous solutions depends on many factors including the type of cations and anions in solution, their concentrations, temperature and the type of solid precipitated. Experiments were conducted using anhydrous La2(SO4)3 and Ce2(SO4)3⋅8H2O as solids and lanthanum(III) perchlorate prepared by dissolving La2O3 in HClO4 solutions as RE-sources. Solutions of H2SO4, H3PO4 and their mixtures in the presence or absence of Na+, Ca2+, Fe(III) or Al(III) as perchlorates served as test solutions. Saturated solutions and precipitated solids were assayed and characterized using standard techniques to show that the La(III) and Ce(III) ions precipitate as hydrated sulphates, phosphates or double salts with sodium, depending upon the solution composition. The change in solubility of RE-salts with solution composition and temperature is the result of the composite effect of changes in solubility products (pKSP) of salts, pKa of acids and other equilibrium constants for ion-association.

By J. Y. Hwang

Microwave heating is an attractive alternative to conventional heating methods because heat is generated directly within the microwave absorbing materials. It has potential to be utilized for selective heating and removal of specified components from a materials mixture. This investigation was undertaken to explore the potential of selective heating and burning of binders for foundry sand reclamation. Selected raw materials and binders used in foundry operations were tested to determine their receptivity to microwave heating. Time needed to reach 600°C and/or the maximum temperature achieved for samples irradiated by microwaves for twenty minutes under 800 W microwave power are reported. The microwave heating characteristics of the selected materials are summarized and discussed. The interactions between microwaves and the raw materials used in a foundry. such as silica sand. chromite sand and bentonite (clay) binder were studied. The results showed that chromite sand coupled well with microwave energy at ambient temperature while silica sand did not. This was expected because the major component of chromite sand. iron chromite (FeCr2O4). is a good microwave absorber. while quartz, which is the major component of silica sand, is a microwave transparent material at ambient temperature. Bentonite absorbs microwaves well because it contains a hydroxyl functional group and water molecules in its structure. It was found that the structure of bentonite was changed through microwave irradiation. Microwave heating characteristics of silica sand mixed with different amounts of bentonite binders were investigated. The presence of bentonite in the mixture improved the microwave heating of silica sand significantly. and bentonite was deactivated by the microwave processing.

Jan 1, 1995

By Yi Tan, Kazuki Morita, Yaqiong Li

Molten Si-Al alloy, with the addition of Sn, was used for metallurgical grade Si purification by a low-temperature solidification method, with the aim of improving the recovery rate of Si. In this ternary melt, bulk Si was grown with a planar front by a directional solidification process under a well-controlled thermal gradient and growth rate conditions, thereby reducing the contamination of solvent metals. Effects of cooling rate, amount of Sn addition, and temperature gradient on the quality of bulk Si were determined. The criterion for constitutional supercooling for single-phase growth from multicomponent melts was employed to evaluate the growth process.

Jan 1, 2015

By S. J. Gerdemann

The U.S. Bureau of Mines is studying the kinetics of wet oxidation of sphalerite concen- trate (ZnS) as a possible process for a gravity-pressurized reactor (GPR). At tempera- tures in excess of 200' C, a sphalerite water slurry will react with 0, to form zinc sul- fate (ZnSO,). However, the pressure required to keep the water from boiling at these temperatures has kept this reaction from becoming a viable continuous process. The GPR can easily obtain the high pressures required for this reaction. The reaction rate is complicated by the solubility of 0, in water and the further oxidation of ZnSO, to insoluble zinc oxysulfate (Zn4(OH),S04.4H20). The effects of pressure, temperature, and particle size on the rate of reaction were investigated. Reaction rate was found to be limited by the amount of oxygen in solution. However, at 250" C and 1500 psia, over 90 pct of the zinc was solubilized in less than an hour. The conditions for maxi- mizing the Zn++ in solution, while minimizing oxysulfate formation, are discussed.

Jan 1, 1993

By Zhenjun Tan, Lei Zhang, Jigang Li, Yifang Zheng, Jilai Xue

"Water electrolysis in 0.4 mol/L NaOH solution for hydrogen generation was carried out with ultrasound introduced through the anode. It was found that the cell voltage reduced by 150-300 mV in the current range of 20 mA to 40 mA with ultrasound frequency at 25.3 kHz. The cell operation became unstable when the cell current was larger than 75 mA with ultrasound. This reduction in cell voltage was due to removal of the gas bubbles on the electrode surface, which can be directly observed in the see-through cell of water electrolysis. Ultrasound with frequency of 33.3 Hz was also tried, but no better effect was obtained. The results suggest that ultrasound assisted water electrolysis can have potential in energy savings for hydrogen production.IntroductionIn electrolytic process, the electrode that the bubbles generated on its surface usually covered a thin gas film, which can be caused an additional voltage about 0.15-0.25V[l,2], especially in aluminum electrolysis. To solve the problem, loading the ultrasound removes the gas bubbles from the electrodes, this subject had been researched in recent years. From 1995 Jilai Xue et al[3,4,5]. applied the ultrasound in aluminum electrolysis in lab. The results from Sheng-De Li et al.[6] reveals that can decrease the cell voltage and have influences about the hydrogen and oxygen's output ratio. Although there are many paper about the applying of ultrasound such as in electrolysis[5,6], deposition[7,8], plating[9,10], oxidation of salts substance on the surface of electrodes[l 1] and so on, the effect of different frequencies ultrasound hadn't been investigated deeply.We focus on the anode voltage by different frequencies ultrasound and the bubble behaviors in this paper. The environment of this experiment is in alkaline solution. Through this exploration it can offer a basis for the applying of ultrasound in electrolysis."

Jan 1, 2011

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 Edgar E. Vidal

The deposition of ceramic materials onto substrates is of special interest in the development of surface related technologies. Research interest has been placed on using thermal plasma as the deposition method, specifically inductively coupled plasmas. Many different modifications to the same basic principle of deposition have been performed through out the materials research community. Such a technique may have many advantages over more conventional techniques, such as high deposition rates, high surface area coverage, clean energy source, no contamination from electrodes and operation near atmospheric pressures. Materials deposited vary from simple oxide systems like TiO2 to more complex structures like ternary oxides and nitrides. This paper reviews recent developments relative to the inductively coupled plasma deposition of thin films.

Jan 1, 2003

By Mingming Zhang

"Three samples received from the EAF shop have been characterized by chemical, X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) methods. The objective of this characterization work is to investigate the occurrence of nickel, copper, zinc, sulfur and phosphorus in these samples and identity their origin and associations with iron minerals in the concentrate samples that are from mines.The samples were identified as Mineral, Pellet, and HRD. The latter is the DR! product. All three samples were received as fine powders. The results indicate that, in the mineral sample, magnetite is the major iron oxide mineral with hematite as a second phase based on the OM and XRD studies. Pyrite [FeS2], chalcopyrite [CuFeS2] and bravoite [(Fe,Ni)S2] are major sulfide minerals. Trace amounts of apatite [Ca5(P04)3(F,Cl,OH)], wardite [Na4CaA112(P04)8(OH)8 6H20], giniite [Fe5(P04)4(OH)3 2H20] and vivianite [Fe3(p04)2 8H20] were identified by SEM and XRD. Microscopic studies also indicated that most of the sulfide grains in the mineral sample are present either as liberated fine particles (about 10 microns) or as inclusions within the magnetite and hematite grains. XRD studies revealed magnetite as the major mineral with subordinate amounts of hematite and pyrite confirming the microscopic findings. Copper, nickel, and zinc are mainly present as chalcopyrite, bravoite, and franklinite [(Zn,Mn,Fe)(Fe,Mn)204] in trace amount in the mineral samples, respectively. Impurities carry over to the Pellet and HRD samples.Chemical analyses of the three iron-bearing samples indicate that sulfur and phosphorus in the Pellet sample exceeded the specification. Since liberated pyrite and chalcopyrite particles were observed both in mineral and pellet samples, magnetic and flotation processing routes for this ore should be effective for sulfide removal but at the cost of iron losses. The high phosphorus content of all three samples indicates that there are phosphates which are difficult to remove by the current concentrating process (magnetic separation and flotation)"

Jan 1, 2012

By Shenghui Guo, Dongbo Li, Lijun Liu, Chengdong He, Jinhui Peng, Libo Zhang

In present study, partially stabilized zirconia (PSZ) was prepared by CaO doped fused zirconia heated by microwave furnace at the temperature of 1450 oC and holding time of 120 min. The XRD results showed that untreated fused zirconia mainly consists of crystalline compounds of cubic ZrO2 phase; while the roasted one mainly is composed of crystalline compounds of cubic ZrO2 phase and monoclinic ZrO2 phase. It is shown through the optimization of structures of two phases that structure of cubic ZrO2 and monoclinic ZrO2 reject each other, revealing its difficulty in forming coinciding interface and linkage of two phases being of Ca atom. Introduction Due to advantages of zirconia, such as high melting point, chemistry inertia, low heat transmission and so on. Zirconia is always taken as megathermal refractory material[1]. However, in the heating and cooling processes of pure zirconium oxide, martensitic transformation will take place associated with greater shear force and volume change, which severely limits the industrial application of pure zirconia in some areas. Such as: Refractory materials, grinding materials and high temperature insulation materials[2]. Through adding a certain amount of MgO, CaO, or Y2O3 stabilizer, etc.[3,4], the zirconia can change into fully stabilized zirconia, which exists in cubic phase. But this high purity fully stabilized zirconia cracks easily because of thermal stress. Therefore, the thermal shock resistance variation is one of the most important quality indicators of zirconia-based materials. According to the heat treatment, the fully stabilized zirconia can be changed into the partially stabilized zirconia (PSZ)[5], which exists in cubic phase and monoclinic phase and has superior mechanical properties, such as anti-heat, low thermal conductivity, large coefficient of thermal expansion and stability, as well as good wear resistance[6].

Jan 1, 2011