Structural and surface morphological properties of chemically deposited Mo<Subscript>0.5</Subscript>W<Subscript>0.5</Subscript>S<Subscript>2</Subscript> thin film

Preparation of layered type semiconductor Mo_0.5W_0.5S₂ ⁻ thin films has been successfully done by using chemical bath deposition method. Objective of the studies are related to structural, optical, morphological and electrical properties of the thin films. The preparation method is based on the reaction between tartarate complex of Mo and W with thiourea in an aqueous alkaline medium at 363 K. X-Ray diffraction reveals a polycrystalline film composed of both MoS₂ and WS₂ phases. The optical study shows that the band gap of the film is 1.6 eV. Electrical conductivity is high which is in the order of 10⁻³–10⁻² (Ώ cm)⁻¹.     

Preparation and thermoelectric properties of BP films on SOI and sapphire substrates

The chemical vapor deposited (CVD) BP films on Si(100) (190 nm)/SiO _x (370 nm)/Si(100) (625 μm) (SOI) and sapphire (R-plane) (600 μm) substrates were prepared by the thermal decomposition of the B₂H₆–PH₃–H₂ system in the temperature range of 800–1050 °C for the deposition time of 1.5 h. The BP films were epitaxially grown on the SOI substrate, but a two-step growth method, i.e., a buffer layer at lower temperature and sequent CVD process at 1000 °C for 1.5 h was effective for obtaining a smooth film on the sapphire substrate. The electrical conduction types and electrical properties of these films depended on the growth temperature, gases flow rates and substrates. The thermal conductivity of the film could be replaced by the substrate, so that the calculated thermoelectric figure-of-merit (Z) for the BP films on the SOI substrate was 10⁻⁴–10⁻³/K at 700–1000 K. Those on the sapphire substrate were 10⁻⁶–10⁻⁵/K for the direct growth and 10⁻⁵–10⁻⁴/K for the two-step growth at 700–900 K, indicating that the film on a sapphire by two-step growth would reduce the defect concentrations and promote the electrical conductivity.     

Experimental determination of solid–liquid interfacial energy for succinonitrile solid solution in equilibrium with the succinonitrile–(D) camphor eutectic liquid

The equilibrated grain boundary groove shapes for Succinonitrile (SCN) solid solution in equilibrium with the Succinonitrile (SCN)–D Camphor (DC) eutectic liquid were directly observed. From the observed grain boundary groove shapes, the Gibbs–Thomson coefficient and solid–liquid interface energy for SCN solid solution in equilibrium with the SCN–DC eutectic liquid has been determined to be (5.39 ± 0.27) × 10⁻⁸ K m and (7.88 ± 0.79) × 10⁻³ J m⁻² with present numerical method and Gibbs–Thomson equation, respectively. The grain boundary energy of SCN rich phase of the SCN–DC eutectic system has been determined to be (14.95 ± 1.79) × 10⁻³ J m⁻² from the observed grain boundary groove shapes. Thermal conductivity ratio of the liquid phase to the solid phase for SCN–0.16 mole % DC alloy has also been measured.     

Waveguide-dielectric resonator method for accurate measurement of parameters of materials at high frequencies

The theory is given, with an analysis and various examples, of the practical implementation of a method for measuring the relative permittivity ɛ^*=ɛ′−iɛ″ of materials in the 0.5–26-GHz frequency range. The results and experimental errors are given of measurements of ε′ in the range 2–200 and of tanδ in the range from 5·10⁻⁵ to 2·10⁻². Translated from Izmeritel'naya Tekhnika, No. 6, pp. 62–66, June, 1999.     

Reduction of aluminum oxide in a nonequilibrium hydrogen plasma

A new method is proposed and experimental investigations are carried out aimed at reducing aluminum oxide in a nonequilibrium hydrogen plasma of a combined glow discharge (CGD) at a pressure of 1315.8–13,158 Pa, a discharge current of 5·10⁻²–3 A, and a hydrogen flow rate of 10⁻⁶–10⁻⁴ nm³/sec. A high degree of conversion of the aluminum oxide (60%) with an energy consumption of 20 kW·h/kg of Al₂O₃ is attained. Reduction of metals from oxides and other compounds in a CGD nonequilibrium hydrogen plasma can be used for producing rare-earth and high-purity metals. Translated from Inzhenerno-Fizcheskii Zhurnal, Vol. 73, No. 3, pp. 580–584, May–June, 2000.     

Diffusion of erbium in silicon

Diffusion of erbium in silicon has been investigated by the electric method. The erbium diffusion coefficient in the temperature range 1150–1250 °C increases from 1.4×10⁻¹³ to 6.2×10^{− 13} cm²·s⁻¹. The values obtained for the diffusion coefficient of erbium in silicon are in good agreement with data obtained by the method of tagged atoms. Pis’ma Zh. Tekh. Fiz. 24, 68–71 (January 26, 1998)     

Titanium-doped indium oxide films prepared by d.c. magnetron sputtering using ceramic target

Polycrystalline thin films of Ti-doped indium oxide (indium–titanium-oxide, ITiO) were prepared by d.c. magnetron sputtering and their electrical and optical properties were investigated. Doping of Ti was effective in improvement of the electroconductivity of the indium oxide: the electrical resistivity of 1.7 × 10⁻³ Ω cm of non-doping decreased to minimum value of 1.8 × 10⁻⁴ Ω cm at 2.4 at.% Ti-doping when the films were deposited at 300 °C. The polycrystalline ITiO films of 0.8–1.6 at. % Ti-doping showed the high Hall mobilitiy (82–90 cm² V⁻¹ s⁻¹) and the relatively low carrier density (2.4–3.5 × 10²⁰ cm⁻³) resulting in characteristics of both low resistivity (2.1–3.0 × 10⁻⁴ Ω cm) and high transmittance in the near-infrared region (over 80% at 1550 nm), which cannot be shown in the conventional Sn-doped indium oxide (ITO) films.     

Leaching of<Superscript>60</Superscript>Co and<Superscript>137</Superscript>Cs from spent ion exchange resins in cement-bentonite clay matrix

The leaching rate of⁶⁰Co and¹³⁷Cs from the spent cation exchange resins in cement-bentonite matrix has been studied. The solidification matrix was a standard Portland cement mixed with 290–350 (kg/m³) spent cation exchange resins, with or without 2–5% of bentonite clay. The leaching rates from the cementbentonite matrix for⁶⁰Co : (4,2–7,0) × 10⁻⁵ (cm/d) and¹³⁷Cs : (3,2–6,6) × 10⁻⁴ (cm/d), after 125 days were measured. From the leaching data the apparent diffusivity of cobalt and cesium in cement-bentonite clay matrix with a waste load of 290–350 (kg/m³) spent cation exchange resins, was measured for⁶⁰Co : (1,1−4,0) × 10⁻⁶ (cm²/d) and¹³⁷Cs : (0,5–2,6) x× 10⁻⁴ (cm²/d), after 125 days. The results presented in this paper are part of the results obtained in a 20-year mortar and concrete testing project which will influence the design of radio-active waste management for a future Serbian radioactive waste disposal centre.     

Highly-sensitive pressure sensor based on W-lighguides

A highly sensitive pressure sensor based on two Mach-Zender interferometers is described. The interferometer measuring and reference channels are made of single-mode W-lightguides. The measured sensitivity was shown experimentally to be 65·10⁻² dB·P⁻¹·m⁻¹. Translated from Izmeritel'naya Tekhnia, pp. 43–46, September, 1999.     

Structure and properties of the layered oxide GdBaFeNiO<Subscript>5 + δ</Subscript>

GdBaFeNiO_5+δ has been synthesized, and its crystal structure, thermal expansion, and electrical properties have been studied. It has a tetragonal structure (sp. gr. P4/mmm) with unit-cell parameters a = 0.3910(2) nm, c = 0.7582(6) nm, and V = 115.9(2) × 10⁻³ nm³ (δ = 0.53) and is a p-type semiconductor. The linear thermal expansion coefficient of GdBaFeNiO_5+δ is 1.32 × 10⁻⁵, 1.72 × 10⁻⁵, and 1.37 × 10⁻⁵ K⁻¹ in the temperature ranges 340–655, 655–870, and 870–1080 K, respectively.     

Photodiodes based on InAs/InAs<Subscript>0.88</Subscript>Sb<Subscript>0.12</Subscript>/InAsSbP heterostructures for 2.5–4.9 μm spectral range

Photodiodes with a photosensitive area diameter of 0.3 mm operating at room temperature in a middle-IR (2.5–4.9 μm) wavelength range have been created based on InAs/InAs_0.94Sb_0.06/InAsSbP/InAs_0.88Sb_0.12/InAsSbP/InAs heterostructures grown by liquid phase epitaxy. Distinguishing features of the proposed photodiodes are a high monochromatic responsivity, which reaches a maximum of 0.6–0.8 A/W at λ_max = 4.0–4.6 μm, and a low dark current density of (1.3–7.5) × 10⁻² A/cm² at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 700–800 Ω. The detection ability of photodiodes in the spectral interval of maximum sensitivity reaches (5–8) × 10⁸ cm Hz^1/2 W⁻¹.     

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

Dissolution kinetics of cobalt in liquid 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 and phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c _s = 4.06 × 10² exp (−46300/RT) mass% for the former alloy and c _s = 5.46 × 10² exp (−49200/RT) mass% for the latter, where R is in J mol⁻¹ K⁻¹ and T in K. For tin, the appropriate equation is c _s = 4.08 × 10² exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. For both alloys, the CoSn₃ intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping times up to 1800 s, whereas the CoSn₂ intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder joints is 95–107 MPa, with the relative elongation being 2.0–2.6%.     

Production of high-current electron beams in an explosive-emission diode at gas pressures ∼ 10− 2–10−1 torr

Data on production of electron beams with ∼200 keV electrons and above ∼100 A beam current in a diode with an explosive-emission cathode at background gas pressures ∼10⁻²−10⁻¹ torr are presented. Discharge regimes with high-voltage stage duration up to 500–800 ns at 10⁻² torr and 80 ns at 10⁻¹ torr have been obtained. The duration of the electron beam behind a 50 μm thick titanium foil was equal to 200 and 400 ns, respectively, and was limited by the transmittance of the foil. Pis’ma Zh. Tekh. Fiz. 24, 88–92 (January 26, 1998)     

Effects of dynamic strain aging on mechanical properties of SA508 class 3 reactor pressure vessel steel

An as-received reactor pressure vessel (RPV) steel SA508 class 3 (SA508 Cl.3) has been subjected to uniaxial tension tests in the strain-rate range of 6.67 × 10⁻⁵ s⁻¹ to 1.2 × 10⁻² s⁻¹ and the temperature range of 298 K to 673 K to investigate the effects of temperature and strain rate on its mechanical properties. It was found that the region of dynamic strain aging (DSA) was in the temperature range of 523–623 K at a strain rate of 1.2 × 10⁻³ s⁻¹, 473–573 K at 1.2 × 10⁻⁴ s⁻¹, and 473–573 K at 6.67 × 10⁻⁵ s⁻¹, respectively. Serrated stress–strain behaviors, predominately consisting of type A, B, and C, have been observed in these temperatures and strain-rate ranges. The solutes responsible for DSA have been identified to be carbon and nitrogen, and nitrogen atoms play a more important role. The relative DSA mechanisms for this RPV steel are discussed.     

Synthesis and electrochemical application of carbon nanotubes obtained from hexachloroethane

Carbon nanotubes (CNTs) with the average inner (outer) diameter of 10–20 nm (20–40 nm) and length up to 100s of nanometers were synthesized via Wurtz reaction at 400 °C for 12 h, using C₂Cl₆ and Na as reactants. These CNTs, having more defects because of the sp³ bonding raw material of C₂Cl₆, were used as electrode material to detect dopamine (DA) via cyclic voltammetry. The results show that there exists linear relation between peak currents and DA concentration in the range of 2 × 10⁻⁷∼2.8 × 10⁻⁴ mol L⁻¹.The linear regression equation is expressed as Ip (μA) = 0.089 + 0.134c (μmol L⁻¹). This CNTs-modified electrode showed high sensitivity with detection limit of 1 × 10⁻⁷ mol L⁻¹.     

Quasi-static and dynamic compressive behaviour of poly(methyl methacrylate) and polystyrene at temperatures from 293 K to 363 K

Flow stress, Young’s Modulus, energy and strain of fracture of poly(methyl methacrylate) (PMMA) and polystyrene (PS) were studied under compressive loading at strain rates of 10⁻⁴–10 s⁻¹ and temperatures from 293 K to temperatures ∼20 K below T _g. It was found that the energy of fracture shows an increase in the quasi-static strain rate (10⁻⁴–10⁻³ s⁻¹) region and becomes constant in the low strain rate (10⁻²–10 s⁻¹) region, while the strain of fracture shows a slow decrease with rate over the strain rate range tested. The activation energies and volumes of PMMA and PS at yield stress, 20% and 30% strain were evaluated using Eyring’s theory of viscous flow. ΔG was found to be constant for all strain rates and strains for both PMMA and PS. The activation volume for both materials increased as a function of strain.     

Growth and properties of CuInS2 single crystals

CuInS₂ single crystals 14–16 mm in diameter and up to 40 mm in length were grown by the traveling solvent method. The crystals were found to ben-type, with a conductivity of 0.1–10 S/cm, carrier concentration of 10¹⁶–10¹⁷ cm⁻³, and carrier mobility of 150–220 cm²/(V s). The anisotropic thermal expansion of the crystals was measured.     

Thermal and dielectric properties of the LTCC composites based on the eutectic system BaO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>

The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al₂O₃–SiO₂–B₂O₃ are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the regulation of an Al₂O₃ content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10⁻⁴, 5 × 10⁻⁴), considerable CTE values (11.7 ppm. °C⁻¹, 10.6 ppm. °C⁻¹) and good mechanical properties (128 MPa,133 MPa).     

Diffusion of promethium in silicon

The first investigations have been made on the diffusion of promethium in silicon. In the temperature range from 1100 to 1250 °C the diffusion constant of promethium increases from ∼1×10⁻¹³ cm²/s to ∼1.5×10⁻¹² cm²/s. The temperature dependence of the diffusion coefficient can be described by D = 5 x 10⁻¹ exp[-(3.3 eV/kT]cm²/s. Pis’ma Zh. Tekh. Fiz. 23, 46–50 (January 26, 1997)     

Optimizing the hot-forging process parameters for connecting rods made of PM titanium alloy

In order to optimize the processing parameters of a new low-cost titanium alloy connecting rod made of powder forging, the deformation behavior of an α + β type Ti–1.5Fe–2.25Mo (wt%) alloy produced by elemental powder metallurgy (PM) route was studied using isothermal compression tests. The constitutive equations and a processing map were established to characterize the flow behavior and predict the optimum deformation parameters. The calculated apparent activation energy was 257.73 kJ/mol for deformation in the α + β phase region and 378.01 kJ/mol in the β phase region. Two deformation mechanism domains were found: α + β → β phase transformation and dynamic recrystallization. The results show that the optimum deformation parameters for the present alloy are (700–800 °C, 10^−1.7–1 s⁻¹) and (800–900 °C, 10⁻²–10 s⁻¹). Based on these results, a finite element method (FEM) simulation of the hot-forming of a connecting rod was conducted, and the simulated results have been successfully used in an industrial forging of the connecting rod.