Growth, thermal and spectroscopic characteristics of LiNd(WO4)2 crystal

Crystal growth, thermal and optical characteristics of LiNd(WO₄)₂ crystal have been investigated. The LiNd(WO₄)₂ crystal up to Ø15 × 32 mm³ has been grown by Czochralski technique. The hardness is about 5.0 Mohs’ scale. The specific heat at 50 °C is 0.42 J g⁻¹ K⁻¹. The thermal expansion coefficient for c- and a- axes is 1.107 × 10⁻⁵ and 2.104 × 10⁻⁵ K⁻¹, respectively. The absorption and fluorescence spectra and the fluorescence decay curve of LiNd(WO₄)₂ crystal were measured at room temperature. Some spectroscopic parameters such as the intensity parameters, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and emission cross sections were estimated.     

Growth and optical characterizations of (Ba0.32Sr0.68)5Nb4O15 crystal

(Ba_0.32Sr_0.68)₅Nb₄O₁₅ crystal with sizes of Ø 17 × 35 mm was grown successfully by Czochralski technique method. The thermal anisotropy was discussed. The principal coefficients of thermal expansion along (100), (010), (001) directions were precisely measured to be 1.308 × 10^− 5, 1.288 × 10^− 5, 1.478 × 10^− 5 K^− 1, respectively. Its optical transparency range has been measured and found to span from 323 to 5500 nm. The bands present in the IR spectra were identified and assigned to the corresponding vibration modes of NbO₆ anions.     

Kapitza resistance and thermal conductivity of Kapton in superfluid helium

We have determined simultaneously the Kapitza resistance, R_K, and the thermal conductivity, κ, of Kapton HN sheets at superfluid helium temperature in the range of 1.4–2.0 K. Five sheets of Kapton with varying thickness from 14 to 130 μm, have been tested. Steady-state measurement of the temperature difference across each sheet as a function of heat flux is achieved. For small temperature difference (10–30 mK) and heat flux density smaller than 30 W m⁻², the total thermal resistance of the sheet is determined as a function of sheet thickness and bath temperature. Our method determines with good accuracy the Kapitza resistance, R_K=(10540±444)T⁻³×10⁻⁶ K m² W⁻¹, and the thermal conductivity, κ=[(2.28±0.54)+(2.40±0.32)×T]×10⁻³ W m⁻¹ K⁻¹. Result obtained for the thermal conductivity is in good agreement with data found in literature and the Kapitza resistance’s evolution with temperature follows the theoretical cubic law.     

Three-dimensional measurement of ice crystals in frozen dilute solution

A Micro-Slicer Image Processing System (MSIPS) has been applied to observe the ice crystal structures formed in frozen dilute solutions. Several characteristic parameters were also proposed to investigate the three-dimensional (3-D) morphology and distribution of ice crystals, based on their reconstructed images obtained by multi-slicing a frozen sample with the thickness of 5 μm. The values of characteristic parameters were determined for the sample images with the dimension of 530×700×1000 μm. The 3-D morphology of ice crystals was found to be a bundle of continuous or dendrite columns at any freezing condition. The equivalent diameter of ice crystals were in the range of 73–169 μm, and decreased exponentially with increasing freezing rate at the copper cooling plate temperature of −20 to −80 °C. At the T_cp −40 °C, the volumes of ice crystals were in the range of 4.6×10⁴ μm³ to 3.3×10⁷ μm³, and 36 ice columns were counted in the 3-D image.     

Electrical and optical properties of 12CaO·7Al2O3 electride doped indium tin oxide thin film deposited by RF magnetron co-sputtering

12CaO·7Al₂O₃ electride (C12A7:e⁻) doped indium tin oxide (ITO) (ITO:C12A7:e⁻) thin films were fabricated on a glass substrate by an RF magnetron co-sputtering system with increasing number of C12A7:e⁻ chips (from 1 to 7) and at various oxygen partial pressure ratios. The optical transmittance of the ITO:C12A7:e⁻ thin film was higher than 70% in the visible wavelength region. In the electrical properties of the thin film, a decrease of the carrier concentration from 2.6 × 10²⁰ cm^− 3 to 2.1 × 10¹⁸ cm^− 3 and increase of the resistivity from 1.4 × 10^− 3 Ω cm to 4.1 × 10^− 1 Ω cm were observed with increasing number of C12A7:e⁻ chips and oxygen partial pressure ratios. It was also observed that the Hall mobility was decreased from 17.27 cm²·V^− 1·s^− 1 to 5.13 cm²·V^− 1·s^− 1. The work function of the ITO thin film was reduced by doping it with C12A7:e⁻.     

Cu diffusion kinetics in (Cu, Ni)3Sn intermetallic compound nanolayers investigated by an Energy-Dispersive-X-ray-based permeation test

The Energy-Dispersive-X-ray-based permeation and oxidation test has been further developed by an improved theoretical analysis, in which chemical potential gradients rather than concentration gradients are employed. The developed test is able to characterize diffusion kinetics in diffusion barriers at the nanometer scale. The Cu flux coefficient in (Cu, Ni)₃Sn intermetallic compound nanolayers was determined from the test to be 8.48 × 10^− 15 mol·(m·s·J/mol)^–1 exp(− 52.3 kJ·mol^− 1/RT) in a temperature range of 250 °C–400 °C.     

Solid–liquid interfacial energy of camphene

The Gibbs–Thomson coefficient and the solid–liquid interfacial energy for camphene have been measured to be (8.58±0.96)×10⁻⁸ K m and (4.43±0.49)×10⁻³ J m⁻², respectively, by a direct method. The grain boundary energy of camphene has also been calculated to be (8.36±0.92)×10⁻³ J m⁻² from the observed grain boundary groove shapes.     

Biosensor enhanced by glucose oxidase biomimetic membrane containing the platinum and silica nanoparticles

In this paper, glucose biosensor is fabricated with immobilization of glucose oxidase (GOx) in platinum and silica sol. The glucose biosensor combined with Pt and SiO₂ nanoparticles could make full use of the properties of nanoparticles. A set of experimental results indicates that the current response for the enzyme electrode containing platinum and silica nanoparticles increases from 0.32 µA cm^− 2 to 33 µA cm^− 2 in the solution of 10 mM β-D-glucose. The linear range is 3 × 10^− 5 to 3.8 × 10^− 3 M with a detection limit of 2 × 10^− 5 M at 3σ. The effects of the various volume ratios of Pt and SiO₂ sols with respect to the current response and the stability of the enzyme electrodes are studied.     

Plastic deformation behavior in dual-phase Ni–31Al intermetallics at elevated temperature

Plastic deformation behavior of dual-phase Ni–31Al intermetallics at elevated temperature was examined. It was found that the alloy exhibited good plasticity under an initial strain rate of 1.25 × 10⁻⁴ s⁻¹ to 8 × 10⁻³ s⁻¹ in a temperature range of 950–1075 °C. A maximum elongation of 281.3% was obtained under an initial strain rate of 5 × 10⁻⁴ s⁻¹ at 1000 °C. The strain rate sensitivity, m value was correlated with temperature and initial strain rate, being in the range of 0.241–0.346. During plastic deformation, both the two phases Ni₃Al and NiAl in dual-phase Ni–31Al could co-deform without any void formation or debonding, the initial coarse microstructure became much finer after plastic deformation. Dislocation played an important role during the plastic deformation in dual-phase Ni–31Al alloy, the deformation mechanism in dual-phase Ni–31Al could be explained by continuous dynamic recovery and recrystallization.     

Mechanical properties of 3D fiber reinforced C/SiC composites

High toughness and reliable three dimensional textile carbon fiber reinforced silicon carbide composites were fabricated by chemical vapor infiltration. Mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.0–2.1 g cm⁻³ after the three dimensional carbon preform was infiltrated for 30 h. The values of flexural strength were 441 MPa at room temperature, 450 MPa at 1300°C, and 447 MPa at 1600°C. At elevated temperatures (1300 and 1600°C), the failure behavior of the composites became some brittle because of the strong interfacial bonding caused by the mis-match of thermal expansion coefficients between fiber and matrix. The shear strength was 30.5 MPa. The fracture toughness and work of fracture were as high as 20.3 MPa m^1/2 and 12.0 kJ·m⁻², respectively. The composites exhibited excellent uniformity of strength and the Weibull modulus, m, was 23.3. The value of dynamic fracture toughness was 62 kJ·m⁻² measured by Charpy impact tests.     

A thermally actuated heat pump

A new kind of heat pump is described derived from the Vuilleumier process which has been known since 1918 but not applied until 1960 for small refrigerators down to 80 K. It consists of two oscillating displacers connected 90° out of phase and in parallel with thermal regenerators. It is pressurized by helium or hydrogen gas to 30–60 bars (3−6 × 10⁶ N m⁻²) and runs at 750 to 1500 rpm. The calculated heating power for a model of 1000 cm³ swept volume, taking heat in at 500°C and allowing for losses, will be 4 to 6 kW and a COP between 1.6 and 2.     

Deposition of low-resistivity gallium-doped zinc oxide films by low-temperature radio-frequency magnetron sputtering

The transparent and conductive gallium-doped zinc oxide (GZO) film was deposited on 1737F Corning glass using the radio-frequency (RF) magnetron sputtering system with a GZO ceramic target. (The Ga₂O₃ contents are approximately 5 wt. %). In this study, the effect of the sputtering pressure on the structural, optical and electrical properties of GZO films upon the glass or polyester film (PET) substrate was investigated and discussed in detail. The GZO film was grown under a steady RF power of 400 W and a lower substrate temperature from room temperature up to 200 °C. The crystal structure and orientation of GZO thin films were examined by X-ray diffraction. All of the GZO films under various sputtering pressures had strong c-axis (002)-preferred orientation. Optical transparency was high (> 80%) over a wide spectral range from 380 nm to 900 nm. According to the experimental data, the resistivity of a single-layered GZO film was optimized at  8.3 × 10^− 4 Ω cm and significantly influenced by the sputtering pressure. In further research, the sandwich structure of the GZO film/Au metal/GZO film was demonstrated to improve the electrical properties of the single-layered GZO film. The resistivity of the sandwich-structured GZO film was around 2.8 × 10^− 4 Ω cm.     

Structural, electrochemical and optical comparisons of tungsten oxide coatings derived from tungsten powder-based sols

Tungsten trioxide (WO₃) electrochromic coatings have been formed on indium tin oxide-coated glass substrates by aqueous routes. Coating sols are obtained by dissolving tungsten powder in acetylated (APTA) or plain peroxotungstic acid (PTA) solutions. The structural evolution and electrochromic performance of the coatings as a function of calcination temperature (250 °C and 400 °C) have been reported. Differential scanning calorimetry and X-ray diffraction have shown that amorphous WO₃ films are formed after calcination at 250 °C for both processing routes; however, the coatings that calcined at 400 °C were crystalline in both cases. The calcination temperature-dependent crystallinity of the coatings results in differences in optical properties of the coatings. Higher coloration efficiencies can be achieved with amorphous coatings than could be seen in the crystalline coatings. The transmittance values (at 800 nm) in the colored state are 35% and 56% for 250 °C and 400 °C-calcined coatings, respectively. The electrochemical properties are more significantly influenced by the method of sol preparation. The ion storage capacities designating the electrochemical properties are found in the range of 1.62–2.74 × 10^− 3 (mC cm^− 2) for APTA coatings; and 0.35–1.62 × 10^− 3 (mC cm^− 2) for PTA coatings. As a result, a correlation between the microstructure and the electrochromic performance has been established.     

Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

Transient flow behaviour in a near alpha titanium alloy Timetal 834 in the dynamic strain aging regime

The transient flow behaviour in Timetal 834 titanium alloy was studied in the temperature range between 400 °C and 475 °C by means of stress relaxation and reloading during tensile testing at a strain rate of 6.67 × 10⁻⁴ s⁻¹. The increment in flow stress during reloading (Δσ_f) and the decrement in flow stress during stress relaxation (Δσ_r) were measured at different strains at each temperature. The observation of maximum value of Δσ_f and Δσ_r, normalized with respect to the Young's modulus at the corresponding temperature, confirmed that the maximum dynamic strain aging (DSA) effect in this alloy occurs at 450 °C.     

Effect of strain rate on the tensile behavior of a single crystal nickel-base superalloy

The effect of various strain rates on the tensile behavior of a single crystal nickel-base superalloy was studied. Single crystals with 0 0 1 crystal orientation were tested at 800 and 1000 °C under three kinds of strain rate of 10⁻³, 10⁻⁴ and 6 × 10⁻⁵ s⁻¹. The yield strength increased with the increase of strain rate, while the configuration of the stress–strain curves was independent of strain rate. Additionally, fracture surface was related to strain rate at two temperatures. At 800 °C the amount of cleavage surface was different at three strain rates, which resulted from the difference of activated slip systems. The elongation increased with the decrease of strain rate, which was influenced by the heterogeneous ductile deformation. At 1000 °C the difference of fracture surface was attributed to the microvoid at higher strain rate, while the γ/γ′ interfaces also played an important role at lower strain rate; elongation rate was independent of strain rate.     

Study on anisotropy of growth rate of ice crystal in supercooled water

The purpose of this research was to investigate the ice growth of a single crystal in three dimensions. Three-dimensional pattern of ice crystal growth in supercooled water was observed using Mach–Zehnder spectro-interferometer. Temperature was varied from −0.3 to −1.6 °C. It was found that the ice crystal began to grow as a single crystal at the tip of the capillary tube and propagated freely in supercooled water. Time variation of the shape of dendrite on a–c plane was obtained. It was found that half parabola fits the shape very closely, and the coefficient of squared term, a, of a quadratic function was calculated. The coefficient, a varied in time but at quasi steady state it was found to be depending mostly upon the degree of supercooling. Furthermore, the growth velocity in c-axis at the flat surface was calculated from the thickness measured. It was found that the velocity in c-axis is independent of the degree of supercooling but depends upon time, in other words, the thickness in c-axis.     

Structural and Thermal Properties of Cu1 – xAgxInS2Chalcopyrite Solid Solutions

The anisotropic thermal expansion of Cu_{1 – x} Ag _x InS₂chalcopyrite solid solutions was studied by x-ray diffraction from 80 to 650 K. Over the entire temperature range studied, the thermal expansion of the solid solutions was found to be anisotropic: thec-axis thermal expansion is considerably smaller than thea-axis thermal expansion. The solid solutions with 0.55 <x< 1.0 exhibit negative c-axis thermal expansion. The composition dependences of the thermal expansion coefficients and anisotropy parameters are nonlinear. The anisotropy parameters rise monotonically with increasing x. The correlation between the thermal expansion anisotropy and tetragonal distortion = 2 – c/ais considered. Directions of zero thermal expansion are identified.     

Dynamic strain aging effect on the fatigue resistance of type 316L stainless steel

Mechanism of dynamic strain aging (DSA) and its effect on the high-temperature low-cycle fatigue resistance in type 316L stainless steel were investigated by carrying out low-cycle fatigue tests in a wide temperature range from 20 to 650 °C with strain rates of 3.2×10⁻⁵–1×10⁻²/s. The regime of DSA was evaluated using the anomalous features of material behavior associated with DSA. The activation energies for each type of serration were about 0.57–0.74 times those for lattice diffusion indicating that a mechanism other than lattice diffusion is involved. It is reasonably concluded that the pipe diffusion of solute atoms along the dislocation core is responsible for DSA. Dynamic strain aging reduced the fatigue resistance by ways of multiple crack initiation, which comes from the DSA-induced inhomogeneity of deformation, and rapid crack propagation due to the DSA-induced hardening.     

Growth and properties of Ca0.28Ba0.72Nb2O6 single crystals

Calcium barium niobate Ca_0.28Ba_0.72Nb₂O₆ (CBN-28) crystals were successfully grown by the Czochralski method. X-ray powder diffraction experiments indicated that CBN single crystals are tetragonal with a = 12.432(±0.002) Å and c = 3.957(±0.001) Å, which have almost the same structure as the Sr_0.50Ba_0.50Nb₂O₆ (SBN-50) crystal. The thermal expansion coefficient perpendicular to Z-direction had been measured to be 1.25 × 10⁻⁵ K⁻¹ between 293.15 and 572.15 K, and along Z-axis was negative between 298.15 and 543.15 K. The specific heat of the crystal had been measured by the differential scanning calorimetric experiments. The transmittance spectra from 200 to 3200 nm were also measured. The measured temperature dependence of dielectric constants showed that the Curie temperature of the CBN-28 crystals is 260 °C, which is about 200 °C higher than that of the (SBN) crystal.