Spontaneous magnetostriction of R2Fe13.6Si3.4 (R = U, Lu)

The thermal expansion of U₂Fe_13.6Si_3.4 and Lu₂Fe_13.6Si_3.4 has been measured by X-ray powder diffraction. Both compounds exhibit a large spontaneous magnetostriction. In the ground state, the volume effect 11.2 × 10⁻³ in U₂Fe_13.6Si_3.4 consists of almost equal contributions from the Fe–Fe and U–Fe exchange interactions (6 × 10⁻³ and 5 × 10⁻³, respectively). In Lu₂Fe_13.6Si_3.4, the volume effect is 8.9 × 10⁻³.     

Conductivity of a new pyrophosphate Sn0.9Sc0.1(P2O7)1−δ prepared by an aqueous solution method

New pyrophosphate Sn_0.9Sc_0.1(P₂O₇)_1−δ was prepared by an aqueous solution method. The structure and conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ have been investigated. XRD analysis indicates that Sn_0.9Sc_0.1(P₂O₇)_1−δ exhibits a 3 × 3 × 3 super structure. It was found that Sn_0.9Sc_0.1(P₂O₇)_1−δ prepared by an aqueous method is not conductive. The total conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ in open air is 2.35 × 10⁻⁶ and 2.82 × 10⁻⁹ S/cm at 900 and 400 °C respectively. In wet air, the total conductivity is about two orders of magnitude higher (8.1 × 10⁻⁷ S/cm at 400 °C) than in open air indicating some proton conduction. SnP₂O₇ and Sn_0.92In_0.08(P₂O₇)_1−δ prepared by an acidic method were reported fairly conductive but prepared by similar solution methods are not conductive. Therefore, the conductivity of SnP₂O₇-based materials might be related to the synthetic history. The possible conduction mechanism of SnP₂O₇-based materials has been discussed in detail.     

Thermo-physical and thermal cycling properties of plasma-sprayed BaLa2Ti3O10 coating as potential thermal barrier materials

Increased turbine inlet temperature in advanced turbines has promoted the development of thermal barrier coating (TBC) materials with high-temperature capability. In this paper, BaLa₂Ti₃O₁₀ (BLT) was produced by solid-state reaction of BaCO₃, TiO₂ and La₂O₃ at 1500 °C for 48 h. BLT showed phase stability between room temperature and 1400 °C. BLT revealed a linearly increasing thermal expansion coefficient with increasing temperature up to 1200 °C and the coefficients of thermal expansion (CTEs) are in the range of 1 × 10^− 5–12.5 × 10^− 6 K^− 1, which are comparable to those of 7YSZ. BLT coatings with stoichiometric composition were produced by atmospheric plasma spraying. The coating contained segmentation cracks and had a porosity of around 13%. The microhardness for the BLT coating is 3.9–4.5 GPa. The thermo-physical properties of the sprayed coating were investigated. The thermal conductivity at 1200 °C is about 0.7 W/mK, exhibiting a very promising potential in improving the thermal insulation property of TBC. Thermal cycling result showed that the BLT TBC had a lifetime of more than 1100 cycles of about 200 h at 1100 °C. The failure of the coating occurred by cracking at the thermally grown oxide (TGO) layer due to severe oxidation of bond coat. Based on the above merits, BLT could be considered as a promising material for TBC applications.     

Synthesis and crystal structure of a new calcium borate, CaB6O10

A new calcium borate, CaB₆O₁₀, has been prepared by solid-state reactions at temperature below 750 °C. The single-crystal X-ray structural analysis showed that CaB₆O₁₀ crystallizes in the monoclinic space group P2₁/c with a = 9.799(1) Å, b = 8.705(1) Å, c = 9.067(1) Å, β = 116.65(1)°, Z = 4. It represents a new structure type in which two [B₃O₇]⁵⁻ triborate groups are bridged by one oxygen atom to form a [B₆O₁₃]⁸⁻ group that is further condensed into a 3D network, with the shorthand notation 6: ∞³[2 × (3:2Δ + T)]. The 3D network affords intersecting open channels running parallel to three crystallographically axis directions, where Ca²⁺ cations reside. The IR spectrum further confirms the presence of both BO₃ and BO₄ groups.     

Interfacial interaction of solid nickel with liquid Pb-free Sn–Bi–In–Zn–Sb soldering alloys

The dissolution process of nickel in liquid Pb-free 87.5% Sn–7.5% Bi–3% In–1% Zn–1% Sb and 80% Sn–15% Bi–3% In–1% Zn–1% Sb soldering alloys has been investigated by the rotating disc technique at 250–450 °C. The temperature dependence of the nickel solubility in soldering alloys obeys a relation of the Arrhenius type c_s = 4.94 × 10² exp(−39500/RT)% for the former alloy and c_s = 4.19 × 10² exp(−40200/RT)% for the latter, where R is in J mol⁻¹ K⁻¹ (8.314 J mol⁻¹ K⁻¹) and T is in K. Whereas the solubility values differ considerably, the dissolution rate constants are rather close for these alloys and fall in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. Appropriate diffusion coefficients vary from 0.16 × 10⁻⁹ to 2.02 × 10⁻⁹ m² s⁻¹. With both alloys, the Ni₃Sn₄ intermetallic layer is formed at the interface of nickel and the saturated or undersaturated melt at dipping times of 300–2400 s. The other Ni–Sn intermetallic compounds are found to be missing. A simple mathematical equation is proposed to evaluate the Ni₃Sn₄ layer thickness in the case of undersaturated melts. The tensile strength of the nickel-to-alloy joints is 94–102 MPa, with the relative elongation being 2.0–2.5%.     

Investigation of the microwave dielectric properties of Ca1−xMgxLa4Ti5O17 ceramics for application in coplanar patch antenna

In this paper, the dielectric properties of Ca_1−xMg_xLa₄Ti₅O₁₇ ceramics at microwave frequency have been studied. The diffraction peaks of Ca_(1−x)Mg_xLa₄Ti₅O₁₇ ceramics nearly unchanged with x increasing from 0 to 0.03. Similar X-ray diffraction peaks of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic were observed at different sintering temperatures. A maximum density of 5.3 g/cm³ can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. A maximum dielectric constant (_r) and quality factor (Q × f) of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h are 56.3 and 12,300 GHz (at 6.4 GHz), respectively. A near-zero temperature coefficient of resonant frequency (τ_f) of −9.6 ppm/°C can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. The measurement results for the aperture-coupled coplanar patch antenna at 2.5 GHz are presented. With this technique, a 3.33% bandwidth (return loss <−10 dB) with a center frequency at approximately 2.5 GHz has been successfully achieved.     

Characteristic and synthesis mechanism of MgB2 nanoparticles in solid-state reactive sintering

MgB₂ nanoparticles were synthesized by a one-step reactive sintering method. The sample was heated from room temperature to 994 K, and then directly cooled down at a rate of 40 K/min. The results of X-ray diffraction indicate that MgB₂ superconductors with high quality were successfully prepared, and only a few impurities were detected on it. The sample consisted of two distinguishable structures by the TEM observation: nanoparticles and single crystals, which is a result of nonequilibrium conversion under the direct cooling condition. The nanoparticles with a diameter of about 10–20 nm are considered to be at the onset for the formation of MgB₂ phase. Transition temperature (T_c) and critical current density (J_c) of the compound structures were determined to be 38.5 K and 1.8 × 10⁵ A cm⁻² by means of SQUID measurement, which indicate good superconducting properties. The inter-diffusion and dislocation incorporation mechanisms for the formation and growth of MgB₂ nanoparticles are also proposed, and the further growth will be accelerated due to an adequate holding time at 994 K.     

Preparation and characteristic of spherical Li3V2(PO4)3

Spherical Li₃V₂(PO₄)₃ was synthesized by using N₂H₄ as reducer. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that single-phase, spherical and well-dispersed Li₃V₂(PO₄)₃ has been successfully synthesized in our experimental process. Electrochemical behaviors have been characterized by charge/discharge measurements. The initial discharge capacities of Li₃V₂(PO₄)₃ were 123 mAh g⁻¹ in the voltage range of 3.0–4.3 V and 132 mAh g⁻¹ in the voltage range of 3.0–4.8 V.     

Improved high-Q microwave dielectric resonator using ZnO-doped La(Co1/2Ti1/2)O3 ceramics

The microwave dielectric properties and the microstructures of ZnO-doped La(Co_1/2Ti_1/2)O₃ ceramics prepared by conventional solid-state route have been studied. Doped with ZnO (up to 0.75 wt%) can effectively promote the densification of La(Co_1/2Ti_1/2)O₃ ceramics with low sintering temperature. At 1320 °C, La(Co_1/2Ti_1/2)O₃ ceramics with 0.75 wt% ZnO addition possesses a dielectric constant (_r) of 30.2, a Q × f value of 73,000 GHz (at 8 GHz) and a temperature coefficient of resonant frequency (τ_f) of −35 ppm/°C.     

Crystal structure, thermal expansion and electrical properties of the new Al0.32ErGe2 compound

A new ternary compound Al_0.32ErGe₂ has been synthesized and studied from 298 K to 773 K using X-ray powder diffraction technique. Its structure has been determined at room temperature by Rietveld refinement of X-ray powder diffraction data. The ternary compound Al_0.32ErGe₂ crystallizes in the orthorhombic with the defect CeNiSi₂ structure type (space group Cmcm, a = 0.40701(2) nm, b = 1.60401(9) nm, c = 0.39240(2) nm, Z = 4 and D_calc = 8.326 g/cm³). The average thermal expansion coefficients , and of Al_0.32ErGe₂ are 1.72 × 10⁻⁵ K⁻¹, 1.11 × 10⁻⁵ K⁻¹ and 1.52 × 10⁻⁵ K⁻¹, respectively. The bulk thermal expansion coefficient is 4.35 × 10⁻⁵ K⁻¹. Electrical resistivity of Al_0.32ErGe₂ was measured between 5 K and 300 K.     

Residual stress measurement of an EB-PVD Y2O3-ZrO2 thermal barrier coating by micro-Raman spectroscopy

Residual stress distribution in an EB-PVD 4 mol% Y₂O₃-ZrO₂ thermal barrier coating (TBC) layer coated on a superalloy substrate has been measured by micro-Raman spectroscopy. Piezo-spectroscopic coefficient was independently calibrated on a freestanding TBC layer. The coefficient for uniaxial stress is Π_uni = 5.43 cm^− 1GPa^− 1. The stress measurement through the TBC thickness shows compressive stress distribution from small to an almost large constant value. Such a distribution agrees with theoretical consideration since the small stress correctly reflects the free edge effect and the large constant stress is closely related to TBC bulk stresses.     

Vibrational spectroscopy and periodic DFT studies of LaMg2PdH7: A material with two types of hydride

The need for a safe, reliable and cheap method for hydrogen transportation has prompted an intense effort in the synthesis of novel hydrides. To direct the search for better materials, it is essential to understand the bonding present in these systems. A newly synthesized material is LaMg₂PdH₇ which is best formulated as {La³⁺}{Mg²⁺}₂{[PdH₄]⁴⁻}{H⁻}₃. Thus hydrogen is formally present both as a free hydride ion and also as a covalently bound ligand. The combination of inelastic neutron scattering (INS), infrared and Raman spectroscopies and periodic density functional theory (DFT) has been used to characterise the material. We find that the material is less ionic than Ba₂[PdH₄], which also contains [PdH₄]⁴⁻. The charges carried by both the coordinating and free hydrides are similar which hints at a degree of covalency in the interactions between the interstitial hydrides and the lanthanum and magnesium ions.     

Structure and electrochemical performance of FeF3/V2O5 composite cathode material for lithium-ion battery

Orthorhombic structure FeF₃ was synthesized by a liquid-phase method using FeCl₃, NaOH and HF solution as starting materials, and the FeF₃/V₂O₅ composites were prepared by milling the mixture of as-prepared FeF₃ and the conductive V₂O₅ powder. The properties of FeF₃/V₂O₅ composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge and cyclic voltammetry measurements. Results showed that the FeF₃/V₂O₅ composites can be used as cathode material for lithium-ion battery. Electrochemical measurements in a voltage range of 2.0–4.5 V reveal that the addition of conductive V₂O₅ improves significantly the electrochemical performance of FeF₃, and the FeF₃/V₂O₅ composite prepared by milling for 3 h exhibits high discharge capacity and good cycle performance, and its discharge capacity maintains about 209 mAh g⁻¹ at 0.1 C (23.7 mA g⁻¹) after 30 cycles.     

Raman and infrared study of 100 MeV swift Ag heavy ion irradiation effects in CaSO4·2H2O single crystals

The modifications of calcium sulphate (CaSO₄·2H₂O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100 MeV Ag⁸⁺ ions in the fluence range 1 × 10¹¹ to 5 × 10¹³ ions/cm². It is observed that the intensities of the Raman modes decrease with increase in ion fluence. We determined damage cross-section (σ) for all the Raman active modes and found to be different for different Raman modes. Further, FT-IR studies have been carried out to confirm surface amorphisation for a fluence of 1 × 10¹³ ions/cm². It is observed that the absorption peaks at 1132–1156 cm⁻¹ corresponds to ν₃(SO₄²⁻) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν₃(SO₄²⁻) modes present on the surface of the sample.     

A novel proton conducting Ba0.95K0.05Ce0.6Zr0.2Gd0.16Zn0.04O3−δ for SOFC

A new proton conducting Ba_0.95K_0.05Ce_0.6Zr_0.2Gd_0.16Zn_0.04O_3−δ electrolyte membrane was prepared on NiO-based anode support by suspension spray followed by a co-sintering at 1400 °C for 4 h. Chemical stability test shows that this new proton conductor displays adequate chemical stability against CO₂ at intermediate temperatures. The conductivity of Ba_0.95K_0.05Ce_0.6Zr_0.2Gd_0.16Zn_0.04O_3−δ in humidified H₂ is about 50% higher than that of BaCe_0.6Zr_0.2Gd_0.16Zn_0.04O_3−δ from 500 to 800 °C. With La_0.8Sr_0.2MnO_3−δ cathode, fuel cell with Ba_0.95K_0.05Ce_0.6Zr_0.2Gd_0.16Zn_0.04O_3−δ electrolyte shows 1.02 V of OCV and 354 mW/cm² of maximum power density at 700 °C, respectively. And the cell performance did not degrade after running at least for 10 h.     

Thermodynamic studies on LaFeO3(s)

The enthalpy increments and the standard molar Gibbs energies in the formation of LaFeO₃(s) have been measured using a high-temperature Calvet micro-calorimeter and a solid oxide galvanic cell, respectively. The corresponding expression for enthalpy increments is given as:

H°(T)−H°(298.15 K)(J mol⁻¹)(±1.2%)=−36887.27+103.53 T(K)+25.997×10⁻³T²(K)+11.055×10⁵/T(K).

The heat capacity, the first differential of H°(T)−H°(298.15 K) with respect to temperature, is given as:

C_p,m°(T)(JK⁻¹mol⁻¹)=103.53+51.994×10⁻³T(K)−11.055×10⁵/T²(K).

From the measured e.m.f. of the cell, (−)Pt/(LaFeO₃(s)+La₂O₃(s)+Fe(s))//CSZ//(Ni(s)+NiO(s))/Pt(+), and the relevant Δ_fG_m°(T) values from the literature, the Δ_fG_m°(LaFeO₃, s, T) was calculated, and is given as:

Δ_fG_m°(LaFeO₃, s, T)(kJmol⁻¹)(±0.72)=−1319.2+0.2317T(K).

The calculated Δ_fH_m°(LaFeO₃, s, 298.15 K) and S°(298.15 K) values obtained using the second law method are −1334.7 kJ mol⁻¹ and 128.9 J K⁻¹ mol⁻¹, respectively.     

Determination of the crystallization kinetic parameters of Ge22.5Te77.5 glass using model-free and model-fitting methods

Differential scanning calorimetry (DSC) technique was used to study the kinetics of amorphous to crystalline transformation for Ge_22.5Te_77.5 glass. The kinetic parameters of glassy Ge_22.5Te_77.5 under non-isothermal conditions are analyzed by the model-free and model-fitting approaches from a series of experiments at different constant heating rates (1–50 K/min). A strong heating rate dependence of the activation energy of crystallization was observed. The analysis of the present data shows that the activation energy of crystallization is not constant but varies with the degree of crystallization and hence with temperature. The crystallization mechanisms examined using the local Avrami exponents indicate that one mechanism (two-dimensional growth) is responsible for the crystallization process for heating rates 1–30 K/min and two mechanisms (one- and two-dimensional growth) are working simultaneously during the amorphous–crystalline transformation of the Ge_22.5Te_77.5 glass for a heating rate 50 K/min. The reaction model that may describe crystallization process of the Ge_22.5Te_77.5 glass is Avrami–Erofeev model (g(α) = [−ln(1 − α)]^1/n) with n = 2 for the heating range 1–30 K/min and n = 1.5 at a heating rate 50 K/min for the whole range of conversion crystallization fraction (α = 0.05–0.95). A good agreement between the experimental and the reconstructed (α − T) curves has been achieved. The transformation from amorphous to crystalline phase in glassy Ge_22.5Te_77.5 demonstrates complex multi-step involving several processes.     

Hydro-chemical conversion of galena in FeCl3-KCl solution

The behaviours of complexation and dissolution of PbCl₂ on the surface of galena were investigated to explore the process of hydro-chemical conversion of galena (PbS) in chloride media. By means of solution chemistry calculation, the production and dissolution of the products PbCl₂ were studied. And the passivation of the galena was studied by Tafel curve. The results show that PbCl₄²⁻ is the main form of PbCl₂ presented in the saturated potassium chloride (KCl) solution. The PbCl₂ crystal is easy to precipitate when the total concentration of chloride ion ([Cl⁻]_T) is equal to 0.92 mol/L, and it is inclined to dissolve when [Cl⁻]_T is more than 0.92 mol/L. The chloride complexing reaction rate strongly depends on the Fe³⁺ion concentration when it is less than 6×10⁻⁴mol/L, while passivation occurs on the surface of the electrode when Fe³⁺ concentration is larger than 6×10⁻⁴mol/L. The reaction rate increases obviously when KCl is added, since the activity of Cl⁻ increases; thus accelerates the dissolution of PbCl₂.     

Magnetic and electrical transport properties of nanostructured La0.67Ca0.33MnO3 networks

Contiguously nanostructured networks of La_0.67Ca_0.33MnO₃ (LCMO) are fabricated successfully by pulsed electron deposition (PED) onto the surface of porous anodic alumina oxide (AAO). The Curie temperature (T_C) is about 250 K. The metal–insulator transition temperature (T_p) is about 145 K without the magnetic field. The magnetoresistance can reach 84% near the peak temperature, which suggesting a strong magnetic correlated electronic transportation process. Zero field cooling (ZFC) and field cooling (FC) are split below the paramagnetic–ferromagnetic transition. The ZFC curves exhibit a typical blocking process. The observed spin glass and weak localization phenomena are due to the size effect, and it is found that the resistance dependent temperature curve above metal–insulator transition temperature (T_p) is more suitable to small polaron hopping (SPH) model.     

Polymer-induced generation and characterization of electrophoretic properties of hollow TiOX nanospheres for electronic paper

Hollow TiO_X nanospheres have been successfully prepared using hollow core–double shell latex particles (poly(styrene-co-methyl methacrylate-co-butyl acrylate-co-methacrylic acid) (abbreviated in poly(St-co-MMA-co-BA-co-MAA)) as template, which involves the deposition of inorganic coating on the surface of hollow core–shell latex particles and subsequent removal of the latex by calcinations in air or ammonia gas. Ti(OBu)₄ was used as precursor for the preparation of hollow TiO_X nanospheres. TEM of white hollow core–double shell polymers particles with an aperture of approximately 225 nm displays the perfect characteristic hollow nanospheres structure of primary core–double shell particles. The formation of TiO_X was confirmed by XRD analysis and hollow structure of the particles was revealed by transmission electron microscopy (TEM). When the calcined temperature was at 800 °C, hollow TiO₂ nanospheres were arranged regularly with the diameter range of 130–170 nm. The electrophoretic properties were characterized by JS94J micro-electrophoresis apparatus. The electrophoretic mobility of white TiO₂ and black TiO hollow spheres in tetrachloroethylene were 1.09 × 10⁻⁵ and 3.12 × 10⁻⁵ cm²/V s, and the zeta potentials were 7.10 and 20.24 mV, respectively. The results show that white TiO₂ particles and black TiO hollow nanoparticles are suitable as electrophoretic particles and possess the application potential in the future electrophoretic display.