Experimental and thermodynamic investigations on MnO-SiO_2-Al_2O_3-MnS system

MnO-SiO₂-Al₂O₃-MnS oxysulfide system has been investigated by experimental phase diagram and activity measurement coupled with thermodynamic modeling.Phase equilibria of the MnO-MnS,MnO-SiO₂-MnS, MnO-Al₂O₃-MnS and MnO-SiO₂-Al₂O₃-MnS systems under low oxygen partial pressure have been experimentally investigated for the temperature range of 1 185 to 1 500℃using equilibration and quenching techniques. Equilibrium phases were analyzed by scanning electron microscope,electron probe X-ray microanalysis（EPMA）, and differential thermal analysis（DTA ）.Phase diagrams were successfully constructed for the systems investigated.Two ternary compounds in the MnO-SiO₂-MnS system were found.Activities of MnO and MnS in MnO-SiO₂-Al₂O₃-MnS liquid oxysulfide solution from very low sulfur concentration to high sulfur concentration at solid MnS saturation were investigated employing gas/liquid/Pt - Mn alloy under controlled atmosphere at 1 500℃.As X（SiO₂）/（X（MnO） + X（SiO₂）） increases in liquid oxysulfide solution,activity coefficient of MnO decreases while that of MnS increases.As X(AlO_1.5) increases,the activity coefficient of MnS increases while no remarkable change was observed for the activity coefficient of MnO.Quantitative analysis of the thermodynamic properties of the oxysulfide solution as well as phase diagram of the system was also earned out by employing the Modified Quasichemical Model in the quadruplet approximation.In view of inclusion utilization for free - cutting steel,it might have an advantage to decrease the Al₂O₃ content and increase the MnO/SiO₂ ratio.     

First-principles study of electronic structure and optical properties of Er:Lu_2O_3

In the present computational study,we found that Er:Lu₂O₃materials have promise for application in laser applications.The crystal structure and the electronic and optical properties of Er:Lu₂O₃materials were studied using first-principle calculations under the framework of density functional theory.Based on the experimental and calculated results,the structure of Lu₂O₃was established.The calculated results show that doping by Er³⁺can effectively improve its absorption coefficient in the ultraviolet region and improve the static dielectric constant of Lu₂O₃.As the doping concentration of Er³⁺increases,the energy of the valence band electrons excited to the conduction band decreases,and the transition is more likely to occur.The absorption coefficient,reflectance,and electron energy loss spectroscopy are bathochromic shifted.The Lu_2-xEr_xO₃(02O₃.     

Phase separation and crystallization of La_2O_3 doped ZnO-B_2O_3-SiO_2 glass

In order to investigate the effect of the La_2O_3 on the phase separation and crystallization of ZnO-B_2O_3-SiO_2 glass, after the occurence of the phase separation and crystallization of glasses by heat treatment, the microstructure morphology and distribution of elements in different sample areas were characterized by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS); the non-isothermal crystallization kinetics of the glass samples was studied by using a differential scanning calorimeter(DSC) and the precipitated crystals of crystallized glass were determined by the X-ray diffraction(XRD). The results suggest that the phase separation and crystallization of 60ZnO-30 B_2O_3-10SiO_2 glass occur at glass surface, and the incorporation of small amount(4 mol%) of La_2O_3 significantly inhibits the glass phase separation and consequently improves the thermal stability of glass.Doping of La_2O_3 accelerates the glass crystallization at the elevated temperature(660 ℃), making the depth of crystal layer thicker and diffraction intensity in XRD patterns stronger. However, due to the precipitation of several crystals that occur simultaneously when La_2O_3 doping amount is 4 mol%, crystallization of the 60ZnO-30B_2O_3-10SiO_2 glass is obviously depressed, the crystallization activation energy Ec and the relative crystallinity X_c of the glass reach the maximum and the minimum values, respectively.Although transition from one-dimensional growth of crystals to two-dimensional growth of crystals results from La_2O_3 addition, the one-dimensional growth of crystals remains dominant in crystallization process. This work can provide some useful information for preparing glass ceramics with nano-crystals precipitated in the glass surface.     

CaO－Al_2O_3－SiO_2渣系氮的溶解热力学

根据炉渣结构的共存理论，推导了ＣａＯ－Ａｌ_２Ｏ_３－ＳｉＯ_２熔渣的作用浓度计算模型。模型计算得出的各组元的作用浓度值与文献报道的活度值非常一致。在此基础上，进一步采用回归分析法找出了ＣａＯ－Ａｌ_２Ｏ_３－ＳｉＯ２渣系中溶解的氮含量以及与此渣系相平衡的钢中氮含量及氮的分配比随渣中各组元作用浓度之间变化的定量关系，理论计算结果与实验值非常符合。     

CaF_2-CaO-MgO-Al_2O_3-SiO_2电渣渣系高温力学性能的研究

本文针对结晶器与铸锭作相对移动的电渣重熔过程中对渣系的高温强度及塑性的要求,对10种CaF_2-CaO-MgO-Al_2O_3-SiO_2渣组成进行了渣的高温强度及塑性的测定,建立了渣组成—渣的岩相结构—渣高温强度及塑性间的对应关系,并选择出较合适的成分范围为CaF_2 35～60％,CaO 10～25％,Al_2O_3 10～20％,SiO_25～15％,MgO≈5％。对其中一个成分的渣进行了电渣热穿孔熔铸中空锭生产实验,并取得了良好的表面质量。     

Diffusion Coefficient of Calcium Ion in CaO-Al_2O_3-SiO_2 Melts

 The Nernst-Einstein equation is used to calculate the diffusion coefficient of calcium ion in the CaO-Al2O3-SiO2 system based on the data of the density and electrical conductivity. It is assumed that all the aluminium ions form tetrahedral structure and merge with chain or ring in the case of molar concentration of CaO higher than Al2O3. And in this case, calcium ion is assumed to be the conclusive charge carrier. A formula between the diffusion coefficient and concentration of calcium ion as well as temperature is deduced, which gives an increasing function relation between the diffusion coefficient and the concentration of calcium ions.     

MgO含量对CaO-Al_2O_3-SiO_2-MgO精炼渣脱硫能力的影响

利用Factsage软件和KTH模型计算并分析了不同MgO含量时四元渣系CaO-Al2O3-SiO2-MgO的硫容量以及钢液(1 600 ℃)溶解铝质量分数为0.03 %时渣钢间硫平衡分配比的影响.得出控制炉渣成分为w(MgO)<8 %,w(CaO)=54 %～59 %,w(Al2O3)=25 %～30 %,w(SiO2)=6 %～10 %时,渣钢间硫平衡分配比能达到500以上,能满足快速冶炼超低硫钢的要求.     

Characterization and photoluminescence of Lu_2O_3-Eu~（3＋） nano-phosphor prepared by modified solution combustion method

Nanoscale Lu2O3:Eu3+ phosphor was prepared by a modified solution combustion method using urea and acrylamide monomer.The particle sizes and photoluminescent properties of nano-phosphor were closely related to the molar ratio of urea-to-RE nitrates and acrylamide monomer-to-RE nitrates.The as-prepared samples with the sizes of 9.6-11.6 nm were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrometer.Lu2O3:Eu3+ nano-phosphor that depicted high photoluminescence in the size around 10 nm was reported.Compared with the sample prepared by solid state reaction,the photoluminescence of sample was increased sufficiently to be 45.1%.The emission spectra of the samples presented the typical emission from 5D0 level to 7FJ(J=0,1,2,3,4) level of the Eu3+ ion.     

Effect of the Fourth Element on Bonding of Silicon Nitride Ceramics with Y_2O_3-Al_2O_3-SiO_2 Glass Solders

Ｂｏｎｄｉｎｇｏｆｓｉｌｉｃｏｎｎｉｔｒｉｄｅｃｅｒａｍｉｃｓｗｉｔｈｏｘｉｄｅｇｌａｓｓｓｏｌｄｅｒｈａｓｂｅｅｎａｃｈｉｅｖｅｄｖｅｒｙｇｒｅａｔｓｕｃｃｅｓｓ[1～ 11] .Ｏｗｉｎｇｔｏｔｈｅｌｏｗｅｒｓｏｆｔｅｎｉｎｇｔｅｍｐｅｒａｔｕｒｅｏｆｒｅｓｉｄｕａｌｇｌａｓｓｉｎｊｏｉｎｔ ,ｔｈｅｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｅｎｇｔｈｏｆｊｏｉｎｔｈａｓｂｅｅｎｄｅｔｅｒｉｏ ｒａｔｅｄ .Ｉｎｏｒｄｅｒｔｏｉｍｐｒｏｖｅｔｈｅｊｏｉｎｔｓｔｒｅｎｇｔｈａｔｅｌｅｖａｔｅｄｔｅｍｐｅｒａｔｕ…     

Warm-white persistent luminescence of Lu_3Al_2Ga_3O_(12):Pr~(3+) phosphor

A warm-white emitting persistent luminescence phosphor Lu_3Al_2Ga_3O_(12):Pr~(3+) was synthesized by solid state method at 1600 °C in air. The refined crystal structure of Lu_3Al_2Ga_3O_(12) host was solved by X-ray diffraction(XRD). The photoluminescence spectra, decay curve and thermoluminescence were investigated. It was revealed that the persistent luminescence originated from the f-f transitions of Pr~(3+) emitters at Lu~(3+) sites in LuO_8 polyhedrons, and it showed white color due to the ~3P_0→~3H_4, ~3P_1→~3H_5, ~3P_0→~3H_5, ~3P_0→~3H_6, ~3P_0→~3F_2, ~3P_0→~3F_3 and ~3P_0→~3F_4 transitions of Pr~(3+) emitters in a wide range. The persistent luminescence of Pr~(3+) in this host could be promoted by f-d transition(278 nm) but f-f transitions, due to the different thermal activation energy. The persistent luminescence of the optimal sample could be actually recorded for 3 h by the definition of 0.32 mcd/m~2 and was visible for more than 7 h by dark-adapted vision in darkness. The initial depth of the dominant shallow traps was calculated to be about 0.56 eV, which is suitable for persistent luminescence. The different roles of the shallow and deep traps on the persistent decay process were investigated. Accordingly, the persistent luminescence processes and mechanism of the as-synthesized Lu_3Al_2Ga_3O_(12):Pr~(3+) phosphors were proposed.     

Synthesis and photoluminescent properties of Eu~(3+)/Dy~(3+) doped SrO-Al_2O_3-SiO_2 glass-ceramics

Eu~(3+)/Dy~(3+) single-doped and co-doped 6SrO-3Al_2O_3-91SiO_2 and 12SrO-6Al_2O_3-82SiO_2 glass and glass-ceramics were synthesized successfully by a sol-gel method. The prepared samples were characterized by the X-ray diffraction, high-resolution transmission electron microscopy, photoluminescent spectra and X-ray photoelectron spectroscopy. The effect of annealing temperature, doped ions and matrix component on the structure and the photoluminescent characteristics was systematically studied. The higher temperature was helpful to form nanocrystals and the amount of SrO and Al_2O_3 could better disperse the rare earth ions in matrix at suitable temperature, and both of them could improve the luminescent intensity. Meanwhile, the doped ions could change the luminescent color by single, codoped and energy transfer. The Sr_2SiO_4 nanocrystals were observed in silicates glasses and became larger with the increase of the annealing temperature and the luminous efficiency of rare-earth(RE) ions could be enhanced when the samples changed from glass state to glass-ceramic state. The results indicated that the photoluminescent properties could be changed through controlling the doped ions, annealing temperature and matrix component.     

Experimental study and thermodynamic assessment of the Ni-Mo-Ta ternary system

Phase equilibrium data of the Ni-Mo-Ta system at 1473, 1373, and 1173 K were determined by means of diffusion triple and electron probe microanalysis (EPMA) techniques in this article. From the present experimental results and literature data, the Ni-Mo-Ta system was thermodynamically assessed using the CALPHAD method. A set of consistent thermodynamic parameters of each phase was obtained. A number of calculated isothermal sections are presented and compared with experimental data. They are in reasonable agreement. The present calculation was successfully used to analyze the solidification behavior of two alloys. Two subsystems, Ni-Mo and Mo-Ta, were assessed prior to the assessment of the ternary system.     

Effect of Iron Oxides on Activity of Calcium Aluminate Clinker in CaO-Al_2O_3-SiO_2 System

The sintering characteristics at 1350℃ and leaching property at 80℃ of calcium aluminate clinkers in the CaO-Al2O3-SiO2 （C-A-S） system with different additions of FeO and Fe2O3 were investigated. FeO inhibits the conversion of β-Ca2SiO4 to γ-Ca2SiO4 and makes the clinker not pulverizable. FeO and Fe2O3 inhibit the formation of CaAl2O4, but promote the formation of Ca12Al14O33. The interplanar spacing at （2 1 1） crystal face of Ca12 Al14O33 in the clinker increases with the increase of FeO addition, which indicates that FeO forms solid solutions in Ca12Al14O33. The clinkers with Fe2O3 addition form a new phase Ca2Fe2O5, and the amount of Ca2Fe2o5 increases with the in crease of Fe2O3 addition. Both FeO and Fe2O3 do not affect the Al2O3 leaching rate of calcium aluminate clinker in sodium carbonate solution, but they increase the molar ratio of caustic Na2O to Al2O3 in the leached liquor.     

A thermodynamic study of Ru-Sn binary alloys

An electrochemical technique incorporating stabilized-zirconia as the solid electrolyte and a Mo+MoO₂ mixture as the reference electrode has been applied for the determination of the activities of Sn in {Ru-Sn} alloys. At 1573 K and X _Sn>0.60, the activities of Sn were very close to the ideal behavior. Nevertheless, the heat of mixing showed relatively large negative values.     

Effects of annealing temperature and neodymium concentration on structural and photoluminescence properties of Nd~(3+)-doped Y_2O_3-SiO_2 powders

We report the structural and photoluminescence(PL) properties of Nd~(3+)-doped Y_2 O_3-SiO_2 powders(Y_2 O_3-SiO_2:Nd~(3+)) as functions of annealing temperature and Nd~(3+) ion doping concentration.Y_2 O_3-SiO_2:Nd~(3+)powders were prepared using the high-energy ball-milling(HEBM) method,and their structural and PL properties were investigated using X-ray diffraction(XRD),Fourier transform infrared(FTIR) spectroscopy,and PL spectroscopy.The XRD results reveal a cubic phase without impurities,and the peak broadening decreases with an increase in annealing temperature due to the increase in the crystallite size.The PL emission intensity increases with an increase in annealing temperature.The highest PL emission intensity is observed for the 300-min milled mixture annealed at 1000℃ for 1 h with a Nd~(3+) concentration of 1 mol%.The PL peaks excited by 800 nm radiation were detected,centered at 1080 nm(~4 F_(3/2)→~4 I_(11/2)) and 1350 nm(~4 F_(3/2)→~4 I_(13/2)).     

Experimental study of phase equilibria and thermodynamic optimization of the Fe-Zn-O system

The Fe-Zn-O phase diagram in air was studied over the temperature range from 900 °C to 1500 °C. The compositions of the phases in quenched samples were obtained by electron probe X-ray microanalysis (EPMA). This experimental technique is not affected by zinc losses resulting from vaporization of zinc at high temperatures. The model for the spinel solid solution was developed within the framework of the compound-energy formalism (CEF). The choice of parameters of the CEF and the sequence of their optimization can have a major influence on the predictions in multicomponent phases. These choices can only be made rationally by reference to the specific model being represented in the CEF. This is discussed for the case of the two-sublattice spinel model. In the limiting case, the proposed model reduces to the model by O’Neill and Navrotsky for spinels. When the CEF is used in combination with the equation of Hillert and Jarl to describe the magnetic contribution to thermodynamic functions of a solution, it is necessary to assign certain values of magnetic properties to all pseudocomponents and to magnetic interaction parameters to obtain the most reasonable approximation of the magnetic properties of a solution. It was shown how this can be done based on very limited experimental data. The same equations can be used when the Murnaghan or the Birch-Murnaghan equation is combined with the CEF to describe the pressure dependence of thermodynamic functions. The polynomial model was used to describe the properties of wustite and zincite, and the modified quasichemical model was used for the liquid slag. All thermodynamic and phase-equilibria data on the Fe-O and Fe-Zn-O systems were critically evaluated, and parameters of the models were optimized to give a self-consistent set of thermodynamic functions of the phases in these systems. All experimental data are reproduced within experimental error limits. These include the thermodynamic properties of phases (such as specific heat, heat content, entropy, enthalpy, and Gibbs energy); the cation distribution between octahedral and tetrahedral sites in spinel; the oxygen partial pressure over single-phase, two-phase, and three-phase regions; the phase boundaries (liquidus, solidus, and subsolidus); and the tie-lines.     

Gd_2O_3-Yb_2O_3-Y_2O_3-ZrO_2热障涂层材料及涂层性能研究

使用化学共沉淀法合成了纳米Gd2O3-Yb2O3-Y2O3-ZrO（2GYYZO）粉末,并最终制备了超细晶团聚的多元稀土氧化物掺杂的GYYZO热喷涂粉末,系统的研究了材料及涂层的基本性能,重点研究了材料及涂层的高温稳定性,材料和涂层的高温相稳定性相对传统纳米8YSZ材料明显提高,对高温热处理过程中涂层孔隙收缩、晶粒长大...     

Experimental Study and Thermodynamic Optimization of the FeO-V_2O_3 System

Optimization of the phase diagram of FeO-V2O3 system is a part of an on-going research project to develop a self-consistent multi-component thermodynamic database for vanadium slag from hot metal.Due to the lack of experimental data for optimization,a novel experimental investigation has been carried out by thermal analysis(DSC)with a series of slags on different V2O3 contents(i.e.3mass%-12mass%).All available thermodynamic and phase diagram data for the binary systems have been simultaneously optimized with CALPHAD(Calculation of Phase Diagrams)methods to give one set of model equations for the Gibbs free energy of the liquid slag as functions of composition and temperature.The modified quasi-chemical model was used to describe the binary slag system.It was demonstrated that the calculated phase diagram with the optimized parameters was in good agreement with the experimental data.