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Electrochemical determination of Gibbs free energy of formation of magnesium ferrite

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Journal of University of Science and Technology Beijing 2007年第4期14卷 361-364页

作者： Ling Wang Huizhu Zhou yanruo hong Girish M Kale School of Chemical Engineering and Biotechnology Hebei Polytechnic University Tangshan 063009 China Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China School of Process Environmental and Materials Engineering Department of Mining and Mineral Engineering University of Leeds Leeds LS2 9IT UK

The standard Gibbs free energy of formation of magnesium ferrite was determined by means of two types of solid state electrochemical cells： one using MgZr4（PO4）6 （MZP） as the solid electrolyte and the other using CaF2 as the solid electrolyte. The first cell was operated in the range of 950 to 1100 K. The second cell was operated in the range of 1125 to 1200 K. The reversibility of the cell EMFs was confirmed by microcoulometric titration. The Gibbs energy changes of magnesium ferrite relative to component oxides were calculated based on EMF measurements and are given by following expressions, respectively： AG1 = -3579-15 T （J/mol） and AGⅡ =6258-24.3 T （J/mol）. The results obtained from two different cells are consistent with each other. The results also are in agreement with Rao＇ s and Tretjakov＇s data in the measured temperature range. When the Gibbs free energies of formation of MgO and Fe203 were substituted in the reaction, the Gibbs free energies of formation of MgFe204 was obtained in two temperature ranges and the for mations are shown as follows： AG 1Formation =-1427394＋360.5 T （J/mol） and AGⅡ Formition =-1417557＋351.2 T （J/mol）.

关键词： magnesium ferrite electrochemical cell Gibbs free energy of formation solid electrolyte

Sintering Caβ″/β/α-Al_2O_3 High Temperature Oxygen Sensor

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Journal of Materials Science & Technology 1995年第5期11卷 345-348页

作者： yanruo hong Liansheng LI and Fengge ZHANG(National Laboratory on Solid Electrolytes and Metallurgical Measurements, University of Science and Technology Beijing, Beijing, 100083, China)(To whom correspondence should be addressed) Beijing Univ of Science and Technology Beijing China

An extended-life and ultra-low oxygen sensor has been fabricated by using polycrystalline Caβ″/β/α-Al2O3 as a solid electrolyte. Five reference electrodes CaO+O2, Caβ″/β/α-Al2O3 (powder)+O2,Cr+Cr2O3, Nb+NbO and Mo+MoO2 were tested in order to select a better reference electrode for this sensor. The limit of determining oxygen activity and the extended-life of the sensor were also tested in this study.

关键词： Al2O3 High Temperature Oxygen Sensor Sintering Ca Cr

Progress of Solid Electrolytes and the Electrochemical Sensors

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Journal of Materials Science & Technology 1997年第3期13卷 173-178页

作者： yanruo hong(National Lab. on Solid Electrolytes and Metallurgical Testing Techniques, University of Science and Technology Beijing,Beijing 100083, China) National Lab. on Solid Electrolytes and Metallurgical Testing Techniques University of Science and Technology Beijing Beijing 100083 China

Four types of solid state electrochemical sensors and their general principles are introduced in the paper. The novel type-IV sensors developed in the last few years are emphasized to study hereafter. The ways to design new electrochemical sensors and the directions to develop new solid electrolytes for new electrochemical sensors are also discussed.

关键词： Li Ba Progress of Solid Electrolytes and the Electrochemical Sensors Wang

Synthesis and Properties of Laβ-Al_2O_3

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Journal of Materials Science & Technology 1997年第2期13卷 157-160页

作者： Congjin JIN yanruo hong (State Support Lab. on Solid Electrolytes and Testing Techniques, University of Science & Technology Beijing,Beijing 100083, China) State Support Lab. on Solid Electrolytes and Testing Techniques University of Science and Technology Beijing Beijing 100083 China

Laβ-Al2O3 solid electrolytes were synthesized directly and their conductivities were measured in terms of ac impedance *** magnitude of conductivities is 10-6 to 10-2 S·*** on these data, the dependence of the conductivity of Laβ-Al2O3 upon the temperature and the dopant concentration in the electrolytes was studied, and the activation energy for conduction was calculated, which is 0.89 eV to 1.02 eV from 450℃ to 1000℃. The ion transference numbers were also determined.

关键词： Al2O3 Synthesis and Properties of La

Kinetics of Oxidation for β-Sialon in Diphase β-Sialon/Al_2O_3 Composite

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Journal of Materials Science & Technology 1999年第1期15卷 21-24页

作者： Youfen LI yanruo hong XangChong Zhong and Tingshou LI(National Laboratory on Solid Electrolytes and Metallurgical Testing Techniques, University of Science & TechnologyBeijing, Beijing 100083, China) National Laboratory on Solid Electrolytes and Metallurgical Testing Techniques University of Science and Technology Beijing Beijing 100083 China

Non-isothermal kinetic research has been carried out on oxidation behavior of β-Sialon in diphaseβ-Sialon/Al_2O_3 composite at high temperatures. A kinetic formula is established for non-isothermal oxidation process of β-Sialon. The rate of oxidation process is controlled by chemicalreaction at the initial stage and then by diffusion. The apparent activation energies and appar-ent rate constants at different temperatures are determined by treating TG data of the overallprocess.

关键词： Al Kinetics of Oxidation for Sialon/Al2O3 Composite

Slag-Resistance of MgAlON Spinel

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International Journal of Minerals,Metallurgy and Materials 2000年第2期14卷 96-98页

作者： Chengji Deng yanruo hong Xiangchong Zhong Jialin Sun(State Laboratory on Solid Electrolytes and Metallurgical Testing Techniques, University of Science and Technology Beijing, Bejing100083, China) State Laboratory on Solid Electrolytes and Metallurgical Testing Techniques University of Science and Technology Beijing Beijing 100083 China

The slag-resistance and microstructural changes after the slag tests of MgAlON spinel containing different amount of nitrogenwere studied by means of crucible slag-resistant experiment, SEM and EDS in the work. The results show that the slag-resistance ofMgAlON is dependent on the nitrogen content, and the optimum amount is 2.88%. The strUcture is not changed although the grains havebeen permeated by some silicon, calcium and iron. A glass phase which contained nitrogen formed in the metaInorphic layeL The glasscan driprove the ability of the slag-resistance of MgAlON because of its higher viscosity.

关键词： MgAlON spinel slag resistance, refractory microstructure composite

A Novel Electrochemical Oxygen Sensor for Determination of Ultra-low Oxygen Contents in Molten Metal

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Journal of University of Science and Technology Beijing 2001年第2期8卷 137-140页

作者： Jialin Sun, Congjin Jin, Liansheng Li, yanruo hong (National Laboratory on Solid Electrolytes and Metallurgical Testing Techniques, University of Science and Technology Beijing, Beijing 100083, China) NLOSEMTT University of Science and Technology Beijing 100083 China

A novel electrochemical oxygen sensor has been developed by using La beta -Al2O3 as solid electrolyte and Cr+Cr2O3 as reference electrode. The sensor not only can be used as normal oxygen sensor but also as an ultra-low oxygen sensor. Especially, it is very sensitive to measure ultra-low oxygen in molten metal. For estimating the accuracy of La beta -Al2O3 oxygen sensor, two series of oxygen activities in molten iron at different oxygen contents and different temperature were measured by both La beta -Al2O3 oxygen sensor and ZrO2 oxygen sensor. The theoretical values of oxygen activities in molten iron (3.30%C, in mass fraction) at 1723K and 1745K were also evaluated for comparing the measuring results of two sensors. At last, the error of measurement for La beta -Al2O3 oxygen sensor was discussed too.

关键词： chemical sensor oxygen sensor ultra-low oxygen sensor La beta-Al2O3 solid electrolyte

Thermodynamic Properties of Non-Oxide Composite Refractories

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China's Refractories 2005年第3期14卷 17-24页

作者： hong yanruo WU hongpeng SUN Jialin School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

For initiative application of non-oxides in refractories, it is essential to study thermodynamic properties of non-oxides. The stability and stable order of non-ox- ides under oxidized atmosphere are analyzed firstly and then a new process, “converse reaction sintering”, is proposed. The results of study on oxidation mechanism of silicon and aluminum nitrides indicate that the gaseous suboxides can be produced observably when the oxygen partial pressure is lower than “conversion oxygen partial pressure”. The suboxides can be deposited near the surface of composite to become a compact layer. This causes the material possessing a performance of “self-impedient oxidation”. Metal Si and Al are the better additives for increasing the density and width of compact layer and increasing the ability of anti-oxidation and anti-corrosion. The study on Si3 N4-Al2O3, Si3N4-MgO, Si3 N4-SiC systems is also enumerated as examples in the paper. The experimental results show that the converse reaction sintering is able to make high performance composites and metal Si and Al not only can promote the sintering but also increase the density and width of compact layer.

关键词： Non-oxide Converse reaction sintering,Thermodynamics

Current Efficiency of Low Temperature Aluminum Electrolysis Studied by Neural Network

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International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 107-110页

作者： Huimin Lu Zuxian Qiu Keming Fang Fuming Wang yanruo hong( Metallurgy School, University of Science and Technology Beijing, Beijing 100083, China)( Department of Nonferrous Metallurgy, Northeastern University, Shenyang 110006, China) Metallurgy School University of Science and Technology Beijing Beijing 100083 China Department of Nonferrous Metallurgy Northeastern University Shenyang 110006 China

A prediction model for Current Efficiency (CE) of low temperature aluminum electrolysis (LTAE) with the low molar ratioelectfolyte of Na3AIF6-AIF3 - CaF2-MgF2-LiF -Al2O3 system was investigated based on artificial neural network principles. The nonlinearmapping between CE of LATE and various electrolytic conditions was obtained from a number of experimental data and used to predictCE of LATE. The trsined neural networks possessed high precision and resulted in a good predicting effect. As a result, attificial neuralnetworks as a new cooperating and predicting technology provide a new approach to the further studies on low temperature aluminumelectrolysis.

关键词： low temperatre aluminum electrolysis current efficiency neural network prediction model low molar ratio electrolyte