Preparation of neodymium-doped yttrium aluminum garnet powders and fibers

Using nitrate precursors, a novel spray-drying assisted citrate gel process for the preparation of neodymium-doped yttrium alumi- num garnet （YAG） phase was developed. Synthesis of single-phase polycrystalline YAG was achieved at temperatures as low as 800 ℃ using the spray-drying methodology whilst conventional approaches currently available require 1000 ℃. Initially, a solution was prepared by mixing aluminum and yttrium nitrates, citric acid, etilenglycol and neodymium oxide. This solution was dried by pulverization （spray dryer） to obtain aggregated precursor powders of the compound. These aggregates were calcined at 800, 850 and 900 ℃ to determine the phase evolution from amorphous to crystalline by X-ray diffraction （XRD）. The morphology of aggregates was characterized by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Moreover, through XRD it was determined that the crystallization of YAG phase started at about 800 ℃ without any intermediate phases. The powders were composed of spherical aggregates with an average diameter of 1 um. From these powders, ceramic fibers with additions of 2at.% and 5at.% Nd, were extracted from the melt with diameters ranging from 30 um to 50 um.     

Synthesis,spectroscopic characterization,and thermal decomposition kinetics of some lanthanide（Ⅲ） nitrate complexes of 2-（N-o-hydroxyacetophenone） amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Complexes of La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Dy（Ⅲ）, Yb（Ⅲ）, and Lu0ID with 2-（N-o- hydroxyacetophenone）amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene （HAAT） formed by the condensation of o-hydroxyacetophenone and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesized and characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility data, UV-Visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to the metal ion through ONO donor sequence. A coordination number nine was proposed for the complexes. Thermal decomposition studies of the ligand and lanthanum（Ⅲ） complex were carried out and kinetic parameters were calculated using Coats-Redfem equation. The decomposition reactions followed random nucleation mechanism with one nucleus on each particle.     

Calculation of AlN and MnS Precipitation in Non-Oriented Electrical Steel Produced by CSP Process

Combining with the study of analogue experiments and test analysis, the kinetics of precipitation and growth of AlN and MnS in non-oriented electrical steel produced by the CSP process is calculated. The results show that the precipitate phase particles of AlN and MnS in typical non-oriented electrical steel grades produced by the CSP process have grown to some extent in the soaking stage, but the precipitation contents are less than 20% of the total contents of nitride and sulfide. The precipitate phase particles of AlN and MnS have precipitated almost after the hot rolling process. The precipitation contents are more than 80% of the total contents of nitride and sulfide, but it is very late for the precipitate phase particles to grow at the end of the hot rolling process.     

Synthesis,crystal structure,and fluorescence of two dimeric europium（Ⅲ） complexes with 2-（trifluoromethyl）benzoate

Two complexes [Eu2（2-TFMBA）6（2,2′-bipy）2]·2H2O （1） and Eu2（2-TFMBA）6（1,10-phen）2 （2） （2-TFMBA=2-（Trifluoromethyl） benzoate; 2,2′-bipy=2,2′-bipyridine; 1,10-phen= 1,10-phenanthroline） were synthesized by solvent method and determined by X-ray diffraction analysis. Complex 1 crystallizes in monoclinic system with space group P21/c, whereas complex 2 crystallizes in triclinic system with space group Pi. Both are binuclear molecules with an inversion center. In complex 1, two center Eu^3＋ ions are linked together by four 2-TFMBA ligands in bidentate-bridging mode. Each Eu^3＋ ion is eight-coordinated with six O atoms from five 2-TFMBA ligands and two N atoms from one 2,2′-bipy molecule. In complex 2, two center Eu^3＋ ions are linked together by four 2-TFMBA ligands in two modes, namely, bidentate-bridging and tridentate-bridging. Each Eu^3＋ ion is nine-coordinated with seven O atoms from five 2-TFMBA ligands and two N atoms from one 1,10-phen molecule. The two complexes both exhibited strong red fluorescence under ultraviolet light, and the ^5D0→^7Fj （j=0-4） transition emissions of Eu^3＋ ion were observed in their emission spectra.     

Grain refinement of AZ31 magnesium alloy by AI-Ti-C-Y master ahoy

Al-Ti-C-Y master alloy was prepared by combining SHS technique and melting-casting method. The microstructure of master alloy and its grain-refining effect on AZ31 alloy were investigated by means of OM, XRD, SEM and EDS. Experimental results indicated that the prepared master alloy consisted of α-Al, TiAl3, TiC and Al3Y phases, and exhibited good grain-refining performance of AZ31 alloy. Morphology of α-Mg changed from coarse dendritic to free equiaxed and the average grain size of α-Mg matrix reduced from the original 580 to 170 μm after adding 1.0 wt.% master alloy. The grain refining efficiency of Al-Ti-C-Y master alloy on AZ31 alloy was mainly attributed to heterogeneous nucleation of TiC particles and grain growth restriction of Al-Y compound or TiC at grain boundaries.     

Chemical stability of doped BaCeO3-BaZrO3 solid solutions in different atmospheres

BaCe0.45Zr0.45M0.1O3-δ （M=Y, In） and BaCe0.9Y0.1O3-δ were prepared through the conventional solid state reaction route. The chemical stability was investigated in hydrogen, carbon dioxide, and boiling water. Crystalline phase and microsa-ucture of the proton conductor before and after stability test were measured with X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The results showed that all materials were quite stable in H2 atmosphere. In CO2 atmosphere, BaCe0.45Zr0.45M0.1O3-δ（M=Y, In） were relatively stable, while Bafe0.9Y0.1O3-δ decomposed. In boiling water, BaCe0.9Y0.1O3-δ was quickly decomposed into Ba（OH）2 and corresponding oxide. BaCe0.45Zr0.45M0.1O3-δ slightly reacted with boiling water and some amorphous phases were formed. However, BaCe0.45Zr0.45In0.1O3-δ was observed to exhibit better stability than BaCe0.45Zr0.45Y0.1O3-δ in water. The experimental results were interpreted in terms of thermodynamic data and tolerance factor.     

Surface ξ potential and photocatalytic activity of rare earths doped TiO2

The iso-electric point of different rare earths （La, Ce, Y） doped anatase TiO2 was set out, and three organisms with different sur- face electrical properties （methylene blue trihydrate-positive electricity, methyl orange-negative electricity, methyl red-neutral electricity） were selected as photodegradable models. The result showed that the photocatalytic activity of 0.5wt.%Y ions doped anatase TiO2 was better than those of the others. The relationship between Zeta （ξ） potential and the photocatalytic activity of different RE doped anatase TiO2 were also investigated. The Y-doped anatase TiO2 was found with the special two iso-electric points and three ξ potential values.     

A white long-lasting phosphor Y2O2S： Tb^3＋ , Sm^3＋： an improvement of Y2O2S：Tb3＋

As an improvement of reported Y2O2S：Tb^3＋, a white-light long-lasting phosphor： Y2O2S：Tb^3＋, Sm^3＋ was prepared by the solid-state reaction. The photo-luminescence spectra showed that the position and shape of Tb^3＋ and Sm^3＋ emissions under UV excitation were similar in this host, which ensured a stable white emission color （daylight standard of IEC） under different excitations. The decay curves of co-doped samples indicated that the decay times of emissions of the two ions were close. The thermo-luminescence measurement suggested that the traps created by the doped Sm^3＋ ions were helpful to postpone the white afterglow of co-doped samples. Therefore, the function of co-doped Sm^3＋ ions was confirmed as improving the white emission colors of samples and acting as new trap centers.     

Effects of AIMnCa and AIMnFe Alloys on Deoxidization of Low Carbon and Low Silicon Aluminum Killed Steels

To confirm the effects of AlMnCa and AlMnFe alloys on the deoxidization and modification of Al2O3 inclusions, experiments of 4-heat low carbon and low silicon aluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1^# AlMnCa alloy has the best ability of deoxidization and modification of Al2O3 inclusions than 2^# AlMnCa and AlMnFe alloys. Steel A deoxidized by 1^# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37× 10^-6. Most of the inclusions in the steel deoxidized by 1^# AlMnCa alloy are spherical CaO-eontaining compound inclusions, and 89.1% of them are smatter than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3-MnO inclusions, and a few of them are spherical, and only 76.8% of them are smaller than 10 μm. Some in- clusions bigger than 50μm are found in the steel D deoxidized by AlMnFe alloy.     

Optical properties of Eu^2＋-doped strontium borate glasses containing F-and Li^＋ ions

In this experiment, strontium borate glasses were prepared using the conventional quenching method in air atmosphere. Optical absorption, photoluminescence excitation and emission spectra, X-ray excited luminescence （XEL）, and luminescence decay curve of the as-prepared glasses were investigated at room temperature. The as-prepared glasses had two kinds of Eu ions, i.e., Eu^2＋ and Eu^2＋. Compared with the reported results of strontium borate glasses, Eu^2＋ luminescence was enhanced in the studied strontium borate glasses coprepared with F^- and Li^＋ ions. The coexisting of Li^＋ or F^- in the borate glasses could create more negative defect Vsr″ and stabilize Eu^2＋ ions, which might act as donor of electrons; For the F^- doping, the new center of B（O, F）4 （or BO3F） and BO2F2 units could be considered to be the distorted （BO4）, which were needed as a rigid framework to stabilize the divalent rare earth ions.     

Phase structure and magnetocaloric effect of （Tb1-xDyx）Co2 alloys

Phase structure and magnetocaloric effect of （Tb1-xDyx）Co2 alloys with x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were investigated using X-ray diffraction analysis, differential thermal analysis, and magnetization measurement. The samples were single phase with cubic MgCu2- type structure; with the increase of Dy content, Tc decreased from 240 K （TbCo2） to 130 K （DyCo2）, and the maximum magnetic entropy change ｜ △SM,max｜ increased from 3.133 to 8.176 J/kg-K under low magnetic field of 0-2 T. The Arrott plot and the change of ｜△SM,max｜ showed that magnetic phase transition from second order to first order occured with the increase of Dy content between x=-0.6 and 0.8.     

Thermodynamic optimization and calculation of phase diagrams of YbCl3-MCl （M=Na,K, Rb,Cs）

YbCl3-MCl （M = Na, K, Rb, Cs） systems were optimized and calculated using the CALPHAD （CALculation of PHAse Diagram） technique. The modified quasi-chemical model in the pair-approximation for short-range ordering was used to describe the Gibbs energies of liquid phase in the systems. On the basis of the measured phase diagram data and experimental thermodynamic properties, a series of thermodynamic functions were optimized and calculated through an interactive computer-assisted analysis. Furthermore, some reasonable discussions on the thermodynamic parameters for these strong interaction binary systems were carded out. The results showed that the optimized parameters and experimental data are thermodynamically self-consistent.     

Kinetic Model of ε-Cu Particle Dissolution in Welding- Induced HAZ of Copper-Containing Steel

The kinetics of ε-Cu particle dissolution in the matrix of heat affected zone （HAZ） during welding of a copper-containing steel was determined by assembling the welding temperature-time program into a modified Whelan＇s solution. The particle dissolution dependence on the degree of ＂superheating＂ above the equilibrium transformation is demonstrated from the model. In terms of volume fraction of particle dissolution, the HAZ may he classified into three zones, including the undissolving zone, the partially dissolving zone, and the completely dissolving zone, respectively. The numerical solution was in good agreement with the experimental examination finding. The results of model can be used to quantitatively map the ε-Cu dissolution zone dependence on the peak temperature of welding thermal cycles and understand the evolution of this transformation during welding.     

Influence of Chemical Composition on Phase Transformation Temperature and Thermal Hot Work Expansion Coefficient of Die Steel

On the basis of the uniform design method, six kinds of martensitic hot work die steels were designed. The phase transformation temperatures including Ac1 , Ac3 , and Ms were measured by DIL805A quenching dilatometer. The influences of the main elements on phase transformation temperatures were analyzed by quadratic stepwise regression analysis, and three corresponding equations were obtained. These equations, in which the interactions of the elements were considered, showed more effectiveness than the traditional ones. In addition, the thermal expansion coefficients of these steels in annealed state and quenched state were also obtained during the tests. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed; the equations obtained were verified by using several kinds of steels. The predicted values were in accordance with the results of the experiments.     

Study on preparation technique and properties of magnetostrictive epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 composites

The magnetic and magnetostrictive properties of epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 （0.85≤x≤1.00） composites, prepared with different epoxy proportions using cold compression-molding technique, were investigated. It is found that the optimal conditions were with a compaction pressure of 100 MPa and a mass ratio of resin to powder of 5：100. The Tb0.1Pr0.9（Fe0.4Co0.6）1.93 composite rod had a high magnetostriction of 770 ppm at an applied magnetic field of 960 kA/m, whereas the Pr（Fe0.4Co0.6）1.93 composite reached 500 ppm at 400 kA/m. The good magnetostrictive properties of Pr（Fe0.4Co0.6）1.93 composite at low-field （≤400 kA/m） could be explained by its low anisotropy. These results indicated that the epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 rod samples for high Pr content of x=0.9-1.0 were of practical value.     

High Temperature Oxidation Resistance of 9Ni Steel

Oxidation rates and scale/steel interface configuration of 9Ni steels were investigated at 1000--1 250 ℃ in air. The results revealed that Cu addition caused high temperature oxidation resistance to deteriorate. High tempera ture oxidation rates increased and scale/steel interface configuration became complicated due to Cu addition. Scale/ steel interface appeared to be network above certain temperature. Temperature required to form network scale/steel interface dropped more than 100 ℃ for 1.5% Cu-containing steel. （Fe,Ni,Cu）x Oy in inner oxidation layer dissocia ted to Fe-Ni-Cu phase and released active oxygen which can react with base steel easily. So the inner oxidation layer became the second source of oxidizing agent besides atmosphere. Internal stress at austenite grain boundary caused local oxide to fragment. So the scale/steel interface appeared to be network. Liquid Si-rich phase formed at sufficient ly high temperature. Penetration of the liquid Si-rich phase along austenite grain enhanced austenite grain oxidizing.     

Investigations on structure and proton diffusion coefficient of rare earth ion （Y^3＋/Nd^3＋） and aluminum codoped α-Ni（OH）2

Rare earth ion （Nd^3＋/Y^3＋） and Al^3＋ codoped α-Ni（OH）2 powers were synthesized by chemical coprecipitation method. The structttre was analyzed with X-ray diffraction （XRD） and thermal gravity （TG）. Cyclic voltammetry （CV） tests were performed to evaluate the proton diffusion coefficients of the samples. The results indicated that codoping of Y-Al and Nd-Al resulted in more water molecules contained within the crystal lattice and accordingly increased the interlayer spacing. In particular, the Y-Al codoped α-Ni（OH）2 showed a turbostratic structure. The calculated diffusion coefficients of the Y-Al codoped α-Ni（OH）2 and Nd-Al codoped α-Ni（OH）2 were 3.5×10^-10cm^2/s and 2.8× 10^-10 cm^2/s, respectively.     

Preparation and photoluminescence of Tb^3＋ doped SrAl2O4 phosphor by composite combustion method

High-efficient Tb^3＋ activated SrAl2O4 phosphor was synthesized by a combined combustion-solid-state reaction method. The precursor of SrAl2O4：Th^3＋ phosphor was prepared via a combustion process, and then the as-prepared powder was heated in a reductive ambient of activated carbon at 1250 ℃ for 1 h. The results of X-ray diffraction, scanning electron microscopy, and photoluminescence spectra revealed the influence of the dosage of urea and heated process on the crystallinity, morphology, and photoluminescence of the phosphor. Comparing with traditional solid-sate reaction, the crystallinity and emission intensity of the SrAl2O4：Tb^3＋ phosphor were improved by this two-step process.     

Current-voltage characteristics with several threshold currents in insulating low-doped La1-xSrxMnO3 （x=0.10） thin films

The current-induced resistive switching behavior in the micron-scale pillars of low-doped La0.9Sr0.1MnO3 thin films using laser molecular-beam epitaxy was reported. It was demonstrated that the current-voltage curves at 120 K showed hysteresis with several threshold currents corresponding to the switching in resistance to metastable low resistance states, and finally, four closed loops were formed. A mode was proposed, which was based on the low-temperature canted antiferromagnetism ordering for a lightly doped insulating regime.     

Phase formation with NaZn13 structure in metamagnetic La（Fe1-xCox）11.9Si1.1 compounds

The effects of different annealing conditions on the phase formation with NaZn13 structure were investigated in La（Fe1-xCox）11.9Si1.1 （x=0.068） compounds. It was found that the 1：13 phase was not formed directly from the melt upon cooling but via a peritectic reaction between the pro-peritectic γ-Fe and the La-rich phase. Annealing temperature was very important for the formation of 1：13 phase. Ice water was confirmed to be a preferable quenching medium. La（Fe1-xCox）11.9Si1.1 （x=0.068） compounds with almost single 1：13 phase were obtained at 1473 K after 15 d.