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...     

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.     

Novel AgCl/Ag<Subscript>2</Subscript>CO<Subscript>3</Subscript> heterostructured photocatalysts with enhanced photocatalytic performance

A series of novel AgCl/Ag₂CO₃ heterostructured photocatalysts with different AgCl contents (5 wt%, 10 wt%, 20 wt%, and 30 wt%) were prepared by facile coprecipitation method at room temperature. The resulting products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), respectively. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of methyl orange (MO) under UV light irradiation. With the optimal AgCl content of 20 wt%, the AgCl/Ag₂CO₃ composite exhibits the greatest enhancement in photocatalytic degradation efficiency. Its first-order reaction rate constant (0.67 h^?1) is 5.2 times faster than that of Ag₂CO₃ (0.13 h^?1), and 16.8 times faster than that of AgCl (0.04 h^?1). The formation of AgCl/Ag₂CO₃ heterostructure could effectively suppress the recombination of the photo-generated electron and hole, resulting in an increase in photocatalytic activity.     

Hydrogen storage properties of as-cast and annealed low-Co La<Subscript>1.8</Subscript>Ti<Subscript>0.2</Subscript>MgNi<Subscript>8.9</Subscript>Co<Subscript>0.1</Subscript> alloys

Low-Co La_1.8Ti_0.2MgNi_8.9Co_0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction (XRD), pressure-composition isotherm (PCI), and electrochemical measurements. The results show that all samples contain LaNi₅ and LaMg₂Ni₉ phases. LaCo₅ phase appears at 1,000 °C. The enthalpy change of all hydrides is close to ?30.6 kJ·mol^?1 H₂ of LaNi₅ compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 °C. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 °C, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g^?1 after 140 charge–discharge cycles.     

Experimental thermodynamic study of intermetallic phases in the binary Ag–Te system by an improved EMF method

A thermodynamic study of the solid two-phase regions of the binary Ag–Te system was made by an improved EMF method, using fast ion conductor RbAg₄I₅ as the solid electrolyte. The EMF measurements were made on three galvanic cells: [Ag | RbAg₄I₅ | Ag₅Te₃ + Te], [Ag | RbAg₄I₅ | Ag₅Te₃ + Ag_1.9Te] and [Ag | RbAg₄I₅ | Ag_1.9Te + Ag₂Te].Based on the results obtained, the EMF for each equilibrium phase assembly was expressed as a function of temperature, in the different regions of thermal stability of the substances. By using the observed EMF and temperature relations, the thermodynamic functions of the stoichiometric equilibrium phase assemblages: Ag₅Te₃–Te, Ag₅Te₃–Ag_1.9Te, Ag₅Te₃–Ag₂Te and Ag₂Te–Ag_1.9Te, in the low-temperature range 22–204 °C, as well as phase transformation temperatures, have been determined. Agreement between the results obtained and the literature values were established.     

Effects of La<Subscript>2</Subscript>O<Subscript>3</Subscript> on Mechanical Properties and Corrosion Resistance of H62 Brass

In this article, the effects of lanthanum oxide (La₂O₃) on the microstructure and mechanical properties of H62 brass were investigated by using the universal testing machine, Brinell hardness tester, optical microscope, and scanning electron microscope (SEM). Immersion corrosion and electrochemical measurements were carried out to identify the influence of La₂O₃ on the corrosion behavior of the H62 brass. The phase constitution, microstructure, and phase composition of the H62 brass were analyzed by x-ray diffraction, SEM, and energy-dispersive spectrometer, respectively. The results show that the microstructure of α phase changes from dendrite grains to equiaxed grains, and the content and distribution of β phase are improved significantly. When the La₂O₃ content reaches 0.8 wt.%, the H62 brass obtains favorable comprehensive mechanical properties and the strength and hardness decrease but elongation increases, which is conducive to plastic processing. In addition, under the optimum amount of 0.8 wt.% La₂O₃ content, the corrosion rate of immersion corrosion attains the minimum values: As 12.6 g m^?2 h^?1, it decreases by 24%; as the corrosion potential changes from ?1.1327 V to ?0.328 V, it increases by 70.9%; and as the corrosion current density decreases from ?2.833 mA mm^?2 to ?3.28 mA mm^?2 corrosion, it decreases by 15.78%, when compared with H62 brass.     

Electrolytic Production of Ti<Subscript>5</Subscript>Si<Subscript>3</Subscript>/TiC Composites by Solid Oxide Membrane Technology

This paper investigated the electrolytic production of Ti₅Si₃/TiC composites from TiO₂/SiO₂/C in molten CaCl₂. The solid-oxide oxygen-ion-conducting membrane tube filled with carbon-saturated liquid tin was served as the anode, and the pressed spherical TiO₂/SiO₂/C pellet was used as the cathode. The electrochemical reduction process was carried out at 1273 K and 3.8 V. The characteristics of the obtained cathode products and the reaction mechanism of the electroreduction process were studied by a series of time-dependent electroreduction experiments. It was found that the electroreduction process generally proceeds through the following steps: TiO₂/SiO₂/C → Ti₂O₃, CaTiO₃, Ca₂SiO₄, SiC → Ti₅Si₃, TiC. The morphology observation and the elemental distribution analysis indicate that the reaction routes for Ti₅Si₃ and TiC products are independent during the electroreduction process.     

Microstructure and Thermomechanical Properties of Atmospheric Plasma-Sprayed Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> Coating

In this study, a Yb₂O₃ coating was fabricated by the atmospheric plasma spray technique. The phase composition, microstructure, and thermal stability of the coating were examined. The thermal conductivity and thermal expansion behavior were also investigated. Some of the mechanical properties (elastic modulus, hardness, fracture toughness, and flexural strength) were characterized. The results reveal that the Yb₂O₃ coating is predominantly composed of the cubic Yb₂O₃ phase, and it has a dense lamellar microstructure containing defects. No mass change and exothermic phenomena are observed in the thermogravimetry and differential thermal analysis curves. The high-temperature x-ray diffraction results indicate that no phase transformation occurs from room temperature to 1500 °C, revealing the good phase stability of the Yb₂O₃ coating. The coefficient of thermal expansion of the Yb₂O₃ coating is (7.50-8.67)?×?10^?6 K^?1 in the range of 200-1400 °C. The thermal conductivity is about 1.5 W m^?1 K^?1 at 1200 °C. The Yb₂O₃ coating has excellent mechanical properties and good damage tolerant. The unique combination of these properties implies that the Yb₂O₃ coating might be a promising candidate for T/EBCs applications.     

Fabrication and magnetic properties of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanorods

NiFe₂O₄ nanorods have been successfully synthesized via thermal treatment of the rod-like precursor fabricated by Ni-doped α-FeOOH, which was enwrapped by the complex of citric acid and Ni²⁺. The morphology evolution during the calcination of the precursor nanorods was investigated with transmission electron microscopy (TEM), and the phase and the magnetic properties of samples were analyzed through X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results indicated that the diameter of the NiFe₂O₄ nanorods obtained ranged between 30 and 50 nm, and the length ranged between 2 and 3 μm. As the calcination temperature was up to 600°C, the coercivity, saturation magnetization, and remanent magnetization of the samples were 36.1 kA·m⁻¹, 27.2 A·m²·kg⁻¹, and 5.3 A·m²·kg⁻¹, respectively. The NiFe₂O₄ nanorods prepared have higher shape anisotropy and superior magnetic properties than those with irregular shapes.     

Thermal and structural role of additives in P<Subscript>2</Subscript>O<Subscript>5</Subscript>-ZnO-Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> glass for low expansion sealing materials

A glass based on the P₂O₅-ZnO-Sb₂O₃ ternary system was modified with various additives, such as RO (R=Ca, Ba and Mn), B₂O₃ and V₂O₅, for low temperature and low expansion sealing materials. The glass transition temperature (T_g) and coefficient of thermal expansion (CTE) were monitored and reduced with additive compositions of RO. Additional incorporation of B₂O₃ at the expense of RO also showed a similar result. Significant improvement was observed when the glass was modified with V₂O_5. A glass showing T_g<350 °C along with CTE<65×10⁻⁷/°C was found, suggesting a high potential for low temperature sealing materials especially for display applications. The role of the quaternary element within the glass is discussed, along with the structural effect using Raman spectroscopy.     

Phase Formation of the Yttrium Aluminates in the Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiC System

Phase formation sequence of the yttrium aluminates in the Y₂O₃-Al₂O₃-SiC ternary system as temperature increases were investigated via x-ray diffraction (XRD). Results showed that YAM (monoclinic), YAP (perovskite) and YAG (garnet) were the yttrium aluminates presented in the solid-state reacted samples at a fixed Al₂O₃:SiC ratio of 1:1. Formation of the yttrium aluminates depended on the temperature. The YAM, YAP and YAG started to form below 1150 °C, at 1300 °C, and at 1450 °C, respectively. Accordingly, two behavior phase diagrams of the Y₂O₃-Al₂O₃-SiC ternary system were recognized, one is in the temperature range of 1150-1300 °C and the other is in 1300-1450 °C, respectively. Thereafter, the phase equilibrium was reached in the temperature range of 1450-1700 °C. Effects of SiC on the phase formation processes in the ternary system were discussed.     

The Effects of KCl,NaCl and K<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the High-Temperature Oxidation Onset of Sanicro 28 Steel

The present study investigates the early stages in the oxidation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to an alkali salt (KCl, NaCl or K₂CO₃) for 2 h at 450 and 535 °C. After the exposure, the oxidized samples were analyzed with a combinatory method (CA, XPS and SEM–EDX). It was found that all three salts were corrosive, and the overall oxidation reaction rate was much higher at 535 °C than at 450 °C. There were clear differences in terms of the impact of cations (Na⁺, K⁺) and anions (Cl^?, CO₃ ^2?) on the initial corrosion process at both temperatures. When focusing on the cations, the presence of potassium ions resulted in a higher rate of chromate formation than in the presence of sodium ions. When studying the effect of anions, the oxidation of iron and chromium occurred at higher rates in the presence of both chloride salts than in the presence of the carbonate salt, and chloride salts seemed to possess higher diffusion rate in the gas phase and along the surface than carbonate salts. Moreover, at the higher temperature of 535 °C, the formed chromate reacted further to chromium oxide, and an ongoing oxidation process of iron and chromium was identified with a significantly higher reaction rate than at 450 °C.     

Thermal Spray Deposition,Phase Stability and Mechanical Properties of La<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript>/LaAlO<Subscript>3</Subscript> Coatings

This paper deals with the deposition of La₂Zr₂O₇ (LZO) and LaAlO₃ (LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness (K _IC) of the annealed coating was only 1.04 MPa m^0.5.     

Ascorbic Acid-Assisted Eco-friendly Synthesis of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles as an Anode Material for High-Performance Lithium-Ion Batteries

We have synthesized NiCo₂O₄ nanoparticles (NCO NPs) using an ascorbic acid-assisted co-precipitation method for the first time. When NCO NPs are used as an anode material for lithium-ion batteries, the cell exhibits superior lithium storage properties, such as high capacity (700 mA h g^?1 after 300 cycles at 200 mA g^?1), excellent rate capabilities (applied current density range 100–1200 mA g^?1), and impressive cycling stability (at 1200 mA g^?1 up to 650 cycles). The enhanced electrochemical properties of NCO NPs are due to the nanometer dimensions which not only offers a smooth charge-transport pathway and short diffusion paths of the lithium ions but also adequate spaces for volume expansion during Li storage. Hence, this eco-friendly synthesis approach will provide a new strategy for the synthesis of various nanostructured metal oxide compounds, for energy conversion and storage systems applications.     

Improvement of electrochemical and electrical properties of LiFePO<Subscript>4</Subscript> coated with citric acid

LiFePO₄ was synthesized using hydrothermal method and coated with different amounts of citric acid as carbon source.The samples were characterized by X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscope（TEM）,surface area measurement—Brunauer–Emmett–Teller（BET）,discharge capability,cyclic voltammetry（CV）,and electrochemical impedance spectroscopy（EIS）.The results show that the quality and thickness of the carbon coating on the surface of LiFePO₄ particles are very important.The optimum carbon content（about 30 wt%）can lead to a more uniform carbon distribution.Electrochemical results show that the samples containing 20 wt%,30 wt%,40 wt%,and50 wt% carbon deliver a discharge capacity of 105,167,151,and 112 mAhg^-1,respectively,at the rate of 0.1C.The increase of carbon content leads to the decrease of discharge capacity of LiFePO₄/C,owing to the fact that excess carbon delays the diffusion of Li⁺ through the carbon layers during charge/discharge procedure.The LiFePO₄/C with low carbon content exhibits poor electrochemical performance because of its low electrical conductivity.Therefore,the amount of carbon must be optimized in order to achieve excellent electrochemical performance of LiFePO₄/C for its application in a lithium ion battery.     

Temperature-Dependent Effects of FeS<Subscript>2</Subscript> Thin Film Synthesized by Thermochemical Spraying: An Optical and Physicochemical Investigation

FeS₂ pyrite films are used in a variety of applications including solar cells and, the potential scope for their utilization is increasing as their synthetic methods become more economical while maintaining or enhancing their high light absorption coefficients. The glass substrate temperature dependence on the formation of FeS₂ pyrite films was investigated with respect to their optical and physicochemical properties. During the thermochemical spraying process the temperature was varied in the range of 190-290 °C. FeS₂ nanocrystalline (40-70 nm) films, formed as a result of atmospheric spraying with glass substrate temperatures above 260 °C, were observed by SEM. Opto-electronic studies revealed that the nanocrystalline films had a direct band gap (1.3-1.6 eV) with a high light absorption coefficient (α > 7 × 10⁴ cm^?1 for λ < 1800 nm). Thus, this study offers an alternative to complicated methods for thin-film formation through spaying technology, for the synthesis of high-quality FeS₂ pyrite films with potential application as high light-absorbing solar energy absorbers.     

Microstructure and Thermal Properties of Atmospheric Plasma-Sprayed Yb<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>7</Subscript> Coating

In the present work, Yb₂Si₂O₇ powder was synthesized by solid-state reaction using Yb₂O₃ and SiO₂ powders as starting materials. Atmospheric plasma spray technique was applied to fabricate Yb₂Si₂O₇ coating. The phase composition and microstructure of the coating were characterized. The density, open porosity and Vickers hardness of the coating were investigated. Its thermal stability was evaluated by thermogravimetry and differential thermal analysis (TG-DTA). The thermal diffusivity and thermal conductivity of the coating were measured. The results showed that the as-sprayed coating was mainly composed of crystalline Yb₂Si₂O₇ with amorphous phase. The coating had a dense structure containing defects, such as pores, interfaces and microcracks. The TG-DTA results showed that there was almost no mass change from room temperature to 1200 °C, while a sharp exothermic peak appeared at around 1038 °C in DTA curve, which indicated that the amorphous phase crystallized. The thermal conductivity of the coating decreased with rise in temperature up to 600 °C and then followed by an increase at higher temperatures. The minimum value of the thermal conductivity of the Yb₂Si₂O₇ coating was about 0.68 W/(m K).     

Thermodynamic optimization of the Na<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> pseudo-binary system

The Na₂O-B₂O₃ system is thermodynamically optimized by means of the CALPHAD method. A two-sublattice ionic solution model, (Na⁺¹)_P(O⁻²,BO₃ ⁻³,B₄O₇ ⁻²,B₃O_4.5)_Q, has been used to describe the liquid phase. All the solid phases were treated as stoichiometric compounds. A set of thermodynamic parameters, which can reproduce most experimental data of both phase diagram and thermodynamic properties, was obtained. Comparisons between the calculated results and experimental data are presented.     

Electrochemical properties of spinel compound LiNi_（0.5）Mn_（1.2）Ti_（0.3）O_4 as cathode materials for lithium ion batteries

The electrochemical properties of spinel compound LiNi0.5Mn1.2Ti0.3O4 were investigated in this study.The chemicals LiAc·2H2O,Mn(Ac)2·2H2O,Ni(Ac)2·4H2O,and Ti(OCH3)4 were used to synthesize LiNi0.5Mn1.2Ti0.3O4 by a simple sol-gel method.The discharge capacity of the sample reached 134 mAh/g at a current rate of 0.1C.The first and fifth cycle voltammogram almost overlapped,which showed that the prepared sample LiNi0.5Mn1.2Ti0.3O4 had excellent good cycle performance.There were two oxidation peaks at 4.21 V and 4.86 V,and two reduction peaks at 4.55 V and 3.88 V in the cycle voltammogram,respectively.By electrochemical impedance spectroscopy and its fitted result,the lithium ion diffusion coefficient was measured to be approximately 7.76 × 10?11 cm2/s.     

Corrosion Behavior and Microhardness of Ni-P-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-composite Coatings on Magnesium Alloy

In the present work, nano-composites of Ni-P-SiO₂-Al₂O₃ were coated on AZ91HP magnesium alloy. The surface morphology of the nano-composite coating was studied by field emission scanning electron microscopy (FESEM). The amount of SiO₂ in the coating was determined by energy-dispersive analysis of x-ray (EDX), and the crystalline structure of the coating was examined by x-ray diffractometer (XRD). All the experiments concerning the corrosion behavior of the coating carried out in 3.5 wt.% NaCl solution and evaluated by electrochemical impedance spectroscopy (EIS) and polarization technique. The results showed that an incorporation of SiO₂ and Al₂O₃ in Ni-P coating at the SiO₂ concentration of 10 g/Land 14 g/LAl₂O₃ led to the lowest corrosion rate (i _corr = 1.3 µA/cm²), the most positive E _corr and maximum microhardness (496 VH). Furthermore, Ni-P-SiO₂-Al₂O₃ nano-composite coating possesses less porosity than that in Ni-P coating, resulting in improving corrosion resistance.