Phase equilibria in the BaS-Ln<Subscript>2</Subscript>S<Subscript>3</Subscript> systems

A survey of available data for the BaS₂-Ln₂S₃ systems shows that the very light lanthanon systems form no intermediate phases but have extensive terminal solid solubilities of BaS in γ-Ln₂S₃ extending to near 50 mol.% BaS. For Ln=Nd and for all heavier lanthanons (smaller ionic radii, r _Ln ³⁺ ), an intermediate phase with stoichiometry of BaLn₂S₄ is formed. BaLn₂S₄ decomposes peritectoidally for Ln=Nd but melts congruently for Ln=Sm and for all heavier lanthanons. A second intermediate phase of stoichiometry, Ba₃Ln₂S₆, forms for Ln=Tb and for all heavier lanthanons (smaller ionic radii). For Ln=Lu, a third phase is formed at BaLu₈S₁₃. In all cases, Ba₃Ln₂S₆ melts peritectically, but BaLu₈S₁₃ melts congruently. The present article discusses: (1) three different techniques for synthesizing the intermediate phases; (2) the systems for Ln=Pr, Tb, and Y; and (3) a computer model for interpolating through the available data for the phase relationships in the nine systems that have been investigated to predict the phase diagrams for the seven systems for which there are limited or no data.     

Preparation and optical properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> powder

Y(NO3)3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-hydrolysis method,and a Y2O3/SiO2 composite powder was obtained by coating.The Y2O3,SiO2,and Y2O3/SiO2 powders were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectrophotometer(FT-IR);the Y2O3 and Y2O3/SiO2 powders were further examined ...     

~ ~ 3＋ Sol-gel synthesis and photoluminescence characterization of La2Ti2O7.EU3＋nanocrystals

Eu³⁺ doped La₂Ti₂O₇ nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid (CA) assisted sol-gel method. Techniques of thermo-gravimetric (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence (PL) performances of the Eu³⁺ doped La₂Ti₂O₇ nanocrystals were evaluated with focus on the effects of calcination temperature and Eu³⁺ doping concentration on the photoluminescence properties.     

Orientation dependence of superelasticity in ferromagnetic single crystals Co<Subscript>49</Subscript>Ni<Subscript>21</Subscript>Ga<Subscript>30</Subscript>

Dependence of the amount of reversible deformation on the orientation of the crystal axis and testing temperature has been studied using [001] and [$ \bar 1 $ \bar 1 24] single crystals of the Co₄₉Ni₂₁Ga₃₀ (at %) alloy upon compression. It has been shown that in the [001] crystals with T ≤ M _s (M _s is the temperature of the onset of the forward martensitic transformation upon cooling) the reversible deformation is equal to 5.5–6.5% and consists of the deformation connected with the shape-memory effect (SME) equal to 4–4.2%, and of “ferroelastic” deformation equal to 1.5–2.2%, which is reversible upon unloading. The total reversible deformation exceeds the lattice deformation ɛ₀ observed upon the B2-L1₀ martensitic transformation, which is equal to 4.5%. At T > A _f (A _f is the finish temperature of the reverse martensitic transformation upon heating), the reversible deformation in [001] crystals is equal to 6.5%. It has been shown electron-microscopically that the reversible deformation equal to 1.5–2.2% in the temperatures range of T = 77−300 K is connected with the development of mechanical twinning in the L1₀ martensite on (110) _L10 planes, which proves to be reversible in the [001] crystals and can be partly irreversible in the [$ \bar 1 $ \bar 1 24] crystals. Upon heating, the (110) _L10 twins of the stabilized L1₀ martensite pass into the ($ \bar 1 $ \bar 1 12) _B2 twins of the B2 phase.     

Upconversion luminescence properties of Er<Superscript>3+</Superscript> doped GeS<Subscript>2</Subscript>-Ga<Subscript>2</Subscript>S<Subscript>3</Subscript>-KCl chalcohalide glasses

Er3+ ions doped chalcohalide glasses with the composition of 56GeS2-24Ga2S3-20KCl were fabricated by a melt-quenching method.Under 800 nm laser excitation,strong green emissions centered at 525 nm and 550 nm and weak red emission centered at 660 nm were observed,which were assigned to 2H11/2→4I15/2,4S3/2→4I15/2,and 4F9/2→4I15/2 transitions,respectively.The intensity reached maximum when the Er3+ ions concentration was 0.1 mol%.The possible upconversion luminescence mechanism was proposed from the discussion...     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Content on Electrical Breakdown Properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Cu Composite

Al₂O₃/Cu composites were prepared by external addition of Al₂O₃, and the effect of Al₂O₃ content on microstructure, density, hardness, electrical conductivity and vacuum electrical breakdown properties was studied. The results show that with increasing Al₂O₃ addition, the density of Al₂O₃/Cu composite significantly decreases, the hardness sharply increases and then slowly decreases, but the electrical conductivity invariably decreases. The vacuum breakdown test shows that with increasing Al₂O₃ addition, the breakdown strength first sharply increases and then decreases when the Al₂O₃ content exceeds 1.2 wt.%; the chopping current always exhibits a decreasing trend and the arc life first increases and then decreases. According to the morphology of arc erosion and analysis, the arc erosion resistance increases and then decreases sharply. In the range of experiments, the optimal arc erosion resistance of Al₂O₃/Cu composite can be obtained with the addition of 1.2 wt.% Al₂O₃.     

Synthesis and characterization of Li<Subscript>1.3</Subscript>Al<Subscript>0.3</Subscript>Ti<Subscript>1.7</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-coated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> by wet chemical route

Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ was prepared by wet chemical route. The phase, surface morphology, and electrochemical properties of the prepared powders were characterized by X-ray diffraction, scanning electron micrograph, and galvanostatic charge-discharge experiments. Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ has similar X-ray diffraction patterns as LiMn₂O₄. The corner and border of Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ particles are not as clear as the uncoated one. The two powders show similar values of lithium-ion diffusion coefficient. When cycled at room temperature and 55°C for 40 times at the charge-discharge rate of 0.2C, Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ shows the capacity retentions of 98.2% and 93.9%, respectively, which are considerably higher than the values of 85.4% and 79.1% for the uncoated one. Both the capacity retention differences between Li_1.3Al_0.3Ti_1.7(PO₄)₃-coated LiMn₂O₄ and LiMn₂O₄ cycling at room temperature and 55°C become larger with the increase of charge-discharge rate. When the charge-discharge rate reaches 2C, the capacity retention of LATP-coated LiMn₂O₄ becomes 8.4% higher than the uncoated LiMn₂O₄ for room temperature cycling, and it becomes 11.1% higher than the latter when cycled at 55°C.     

Hydrogen generation from the H<Subscript>2</Subscript>O/H<Subscript>2</Subscript>O<Subscript>2</Subscript> /MnMoO<Subscript>4</Subscript> system

Hydrogen gas as a clean energy resource was found to be largely bubbled from the H₂O/H₂O₂/MnMoO₄ system. The MnMoO₄ powder was synthesized by a sol-gel method and was characterized with x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectrometry. The efficiency of the hydrogen generation increases with increasing H₂O₂ proportion, amount of MnMoO₄ powder, and intensity of light resource. A mechanism is suggested for hydrogen generation from the H₂O/H₂O₂/MnMoO₄ system.     

Evaluation of in vitro and in vivo tests for surface-modified titanium by H<Subscript>2</Subscript>SO<Subscript>4</Subscript> and H<Subscript>2</Subscript>O<Subscript>2</Subscript> treatment

Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal. Specimens were chemically washed for 2 min in a 1∶1∶1.5 (vol.%) mixture of 48 %HF, 60%HNO₃ and distilled water. The specimens were then chemically treated with a solution containing 97%H₂SO₄ and 30%H₂O₂ at the ratio of 1∶1 (vol.%) at 40°C for 1h, and subsequently heat-treated at 400°C for 1h. All the specimens were immersed in HBSS with pH 7.4 at 36.5°C for 15d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28 d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a solution of H₂SO₄ and H₂O₂. The average roughness was 2.175 μm after chemical surface treatment. The amorphous titania was subsequently transformed into anatase by heat treatment at 400°C for 1h. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 47.1μm in the chemically treated Ti, and 52.2, 168.7 and 101.9μm, respectively, in the untreated commercial pure Ti, aluminum and stainless steel 316L.     

Magnetic anisotropy of the Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>B compound and its hydride Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>BH<Subscript>4</Subscript>

Magnetization curves of single crystals of Nd₂Fe₁₄B and its hydride Nd₂Fe₁₄BH₄ have been measured along their principal crystallographic directions in a temperature range of 4.2–280 K. The magnetic anisotropy constants, which allow one to describe experimental magnetization curves as well as the low-temperature “easy-cone”-type magnetic structure and field-induced first-order magnetic phase transitions, have been determined in terms of a collinear-ferrimagnetic-ordering model. The anisotropy constants were shown to decrease in magnitude upon hydrogenation. In this case, the ratios of the effective fourth-and sixth-order constants to the second-order constant increase, whereas the constants responsible for the basal-plane anisotropy exhibit a more than threefold decrease. At the same time, the spin-reorientation temperature and opening of the magnetization cone at 4.2 K remain virtually unchanged. The results obtained are discussed in terms of the single-ion-anisotropy theory.     

Magnetic properties and crystallization kinetics of Zn<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Precursor of nanocrystalline Zn0.5Ni0.5Fe2O4 was obtained by grinding mixture of ZnSO4·7H2O,NiSO4·6H2O,FeSO4·7H2O,and Na2CO3·10H2O under the condition of surfactant polyethylene glycol(PEG)-400 being present at room temperature,washing the mixture with water to remove soluble inorganic salts and drying it at 373 K.The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K.The precursor and its calcined products were characterized by differential scanning calorimetry(DSC) ,Fourier transform infrared(FT-IR) ,X-ray diffraction(XRD) ,and vibrating sample magnetometer(VSM) .The result showed that Zn0.5Ni0.5Fe2O4 obtained at 1073 K had a saturation magnetization of 74 A·m2·kg-1.Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique,and kinetic parameters were determined by Kissinger equation and Moynihan et al.equation.The value of the activation energy associated with the crystallization process of Zn0.5Ni0.5Fe2O4 is 220.89 kJ·mol-1.The average value of the Avrami exponent,n,is equal to 1.59±0.13,which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.     

Synthetically Controlled,Carbon-Coated Co<Subscript>2</Subscript>SnO<Subscript>4</Subscript>/SnO<Subscript>2</Subscript> Composite Anode for Lithium-ion Batteries

The inherent drawbacks of Co₂SnO₄ in demonstrating the closer-to-theoretical capacity value behavior and the inadmissible volume-expansion-related capacity fade behavior have been surpassed by choosing a tailor-made material composition of Co₂SnO₄/SnO₂, prepared at two different temperatures such as 400°C and 600°C to obtain residual carbon-containing and carbon-free compositions, respectively. Among the products, carbon-coated Co₂SnO₄/SnO₂ composite exhibits better electrochemical performance compared with that of the carbon-free product mainly because of the beneficial effect of carbon in accommodating the volume-expansion-related issues arising from the alloying/de-alloying mechanism. A combination of conversion reaction and alloying/de-alloying mechanism is found to play a vital role in exhibiting closer-to-theoretical capacity values. In other words, an appreciable specific capacity value of 834 mAh g^?1 has been exhibited by Co₂SnO₄/SnO₂ anode containing carbon coating, thus, demonstrating the possibility to improve the electrochemical performance of the title anode through carbon coating, which is realized as a result of the addition of carefully manipulated synthesis conditions.     

Sol-gel preparation and characterization of Li1.3Al0.3Ti1.7（PO4）3 sintered with flux of LiBO2

Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ were prepared by sol-gel method. The structural identification, surface morphology, ionic conductivity, and activation energy of the pellets were studied by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The results show that all the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ have similar X-ray diffraction patterns. The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO₂. Among the Li_1.3Al_0.3Ti_1.7(PO₃)₄ pellets sintered with different mole fractions of LiBO₂, the one sintered with 1 mol% LiBO₂ shows the highest ionic conductivity of 3.95×10⁻⁴ S.cm⁻¹ and the lowest activation energy of 0.2469 eV.     

Diffraction Patterns and Crystal Structure of Si<Subscript>3</Subscript>N<Subscript>4</Subscript> and Ge<Subscript>3</Subscript>N<Subscript>4</Subscript>

A nitride, believed to be SiN,, has been separated from three nitrided silicon steels. Germanium nitride, GeN,, has been prepared from pure germanium. Comparison of the diffraction patterns indicates that the two nitrides are isomorphous; an orthorhombic structure is suggested in place of the rhombohedral structure previously reported for Ge₃N₄.     

Growth Kinetics and Microstructure Evolution of Intermediate Phases in MoSi<Subscript>2</Subscript>-Si<Subscript>3</Subscript>N<Subscript>4</Subscript>-WSi<Subscript>2</Subscript>/Mo Diffusion Couples

The growth kinetics and silicon diffusion coefficients of intermediate silicide phases in MoSi₂-3.5 vol.% Si₃N₄-5.0 vol.% WSi₂/Mo diffusion couple prepared by spark plasma sintering were investigated in temperatures ranging from 1200 to 1500 °C. The intermediate silicide phases were characterized by x-ray diffraction. The microstructures and components of the MoSi₂-Si₃N₄-WSi₂/Mo composites were investigated using scanning electron microscope with energy-dispersive spectroscopy. A special microstructure with MoSi₂ core surrounded by a thin layer of (Mo,W)Si₂ ring was found in the MoSi₂-Si₃N₄-WSi₂ composites. The intermediate layers of Mo₅Si₃ and (Mo,W)₅Si₃ in the MoSi₂-Si₃N₄-WSi₂/Mo diffusion couples were formed at different diffusion stages, which grew parabolically. Activation energy of the growth of intermediate layers in MoSi₂-3.5 vol.% Si₃N₄-5.0 vol.% WSi₂/Mo diffusion couple was calculated to be 316 ± 23 kJ/mol. Besides, the hindering effect of WSi₂ addition on the growth of intermediate layers was illustrated by comparing the silicon diffusion coefficients in MoSi₂-3.5 vol.% Si₃N₄-5.0 vol.% WSi₂/Mo and MoSi₂-3.5 vol.% Si₃N₄/Mo diffusion couples. MoSi₂-3.5 vol.% Si₃N₄-5.0 vol.% WSi₂ coating on Mo substrate exhibited a better high-temperature oxidation resistance in air than that of MoSi₂-3.5 vol.% Si₃N₄ coating.     

Phase Relations in the ZrO<Subscript>2</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> System: Experimental Study and Advanced Thermodynamic Modeling

Phase equilibria in the ZrO₂-Nd₂O₃-Y₂O₃ system at 1523-1873 K have been investigated by x-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive x-ray spectroscopy (SEM/EDX). Temperatures of phase transformations were determined by differential thermal analysis. Temperatures of invariant reactions in the ZrO₂-Nd₂O₃ system F = A + Pyr and H = F + A were determined as 1763 and 2118 K respectively and thermodynamic parameters of phases were re-assessed. Phase transformations in ternary systems were determined at 1732 K for composition ZrO₂-48.46Nd₂O₃-5.38Y₂O₃ (mol%) and at 1744 and 1881 K for composition ZrO₂-79.09Nd₂O₃-2.75Y₂O₃ (mol%). They were interpreted using XRD investigation before and after DTA as Pyr + B → F, Pyr → F and A → B, respectively. The solubility of the Y₂O₃ in pyrochlore phase was found to exceed 10 mol%. The thermodynamic parameters of the ZrO₂-Nd₂O₃-Y₂O₃ system were reassessed taking into account solubility of Y₂O₃ in the Nd₂Zr₂O₇ pyrochlore phase (Pyr). It is assumed that Y³⁺ substitutes Nd³⁺ and Zr⁴⁺ in their preferentially occupied sublattices. Ternary parameter was introduced into fluorite phase (F) for better reproducing of phase equilibria. Mixing parameters were reassessed for phase A (Nd₂O₃ based solution), monoclinic phase B and cubic phase C (Y₂O₃ based solution). The isothermal sections calculated for the ZrO₂-Nd₂O₃-Y₂O₃ system are in the reasonable agreement with experimental results.