Reproduction of the volt unit over an extended range of voltages

A scale converter designed at the D. I. Mendeleev Institute of Metrology is described, which, together with the equipment of the State volt unit, makes it possible to reproduce the size of the emf unit, the volt, over an extended range of voltages (up to 10 V) with errors σ_A=7.2·10^-9 and σ_B=5.6·10^-9. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 41–42, April, 1998.     

Hydrodynamics and heat transfer in cooling systems with intersecting channels. 3. Effect of the angle of flow and the number of stages

Results of further investigation of some variants of wafer structures are given. The effect of the angle of flow on the hydraulic resistance and heat transfer at Re numbers of 1·10²–2·10⁴ is revealed. The temperature field of a two-stage system is analyzed. It is shown that a size reduction of the structure and an increase in the number of stages make it possible to obtain the maximum possible coefficient of reduced heat transfer (2.5–2.8)·10⁵ W/(m²·K). Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 214–223, March–April, 2000.     

Thickness dependent electrical properties of CdO thin films prepared by spray pyrolysis method

A large number of thin films of cadmium oxide have been prepared on glass substrates by spray pyrolysis method. The prepared films have uniform thickness varying from 200–600 nm and good adherence to the glass substrate. A systematic study has been made on the influence of thickness on resistivity, sheet resistance, carrier concentration and mobility of the films. The resistivity, sheet resistance, carrier concentration and mobility values varied from 1·56–5·72×10⁻³ Ω-cm, 128–189 Ω/□, 1·6–3·9×10²¹ cm⁻³ and 0·3–3 cm²/Vs, respectively for varying film thicknesses. A systematic increase in mobility with grain size clearly indicates the reduction of overall scattering of charge carriers at the grain boundaries. The large concentration of charge carriers and low mobility values have been attributed to the presence of Cd as an impurity in CdO microcrystallites. Using the optical transmission data, the band gap was estimated and found to vary from 2·20–2·42 eV. These films have transmittance around 77% and average reflectance is below 2·6% in the spectral range 350–850 nm. The films aren-type and polycrystalline in nature. SEM micrographs of the CdO films were taken and the films exhibit clear grains and grain boundary formation at a substrate temperature as low as 523 K.     

Size dependent optical characteristics of chemically deposited nanostructured ZnS thin films

ZnS thin films of different thicknesses were prepared by chemical bath deposition using thiourea and zinc acetate as S²⁻ and Zn²⁺ source. The effect of film thickness on the optical and structural properties was studied. The optical absorption studies in the wavelength range 250–750 nm show that band gap energy of ZnS increases from 3·68–4·10 eV as thickness varied from 332–76 nm. The structural estimation shows variation in grain size from 6·9–17·8 nm with thickness. The thermoemf measurement indicates that films prepared by this method are of n-type.     

Dielectric and pyroelectric properties of a composite of ferroelectric ceramic and polyurethane

Flexible piezo- and pyroelectric composite was made in the thin film form by spin coating. Lead Zirconate Titanate (PZT) ceramic powder was dispersed in a castor oil-based polyurethane (PU) matrix, providing a composite with 0–3 connectivity. The dielectric data, measured over a wide range of frequency (10^–5 Hz to 10⁵ Hz), shows a loss peak around 100 Hz related with impurities in the polymer matrix. There is also an evidence of a peak in the range 10^–4 Hz, possibly originating from the glass transition temperature T_g of the polymer. The pyroelectric coefficient at 343 K is 7.0×10^–5 C·m^–2·K^–1 which is higher than that of β-PVDF (1×10^–5 C·m^–2·K^–1). Electronic Publication     

Structure and Features of the Motion of a Cathode Spot on a Continuous Titanium Cathode

High-speed video filming by the VS-FAST-NG CCD-array-based video camera from the firm of Videoskan with speeds of 1000 and 5000 frames per second and exposure time of 1·10⁻³ and 2·10⁻⁴ sec, respectively, is conducted. It is established that the arc burns from two or three cathode spots for (1–1.2)·10⁻³ sec. The mean and local speeds of the group of cathode spots are determined. If there is no external magnetic field present, the mean speed is equal to 5–6 m/sec. If there is a magnetic field B = 0.005 T present, the mean speed is equal to 15–16 m/sec. __________ Translated from Izmeritel'naya Tekhnika, No. 10, pp. 42–44, October, 2005.     

Li-storage and cycling properties of spinel,CdFe<Subscript>2</Subscript>O<Subscript>4</Subscript>, as an anode for lithium ion batteries

Cadmium ferrite, CdFe₂O₄, is synthesized by urea combustion method followed by calcination at 900°C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) techniques. The Li-storage and cycling behaviour are examined by galvanostatic cycling, cyclic voltammetry (CV) and impedance spectroscopy in the voltage range, 0·005–3·0 V vs Li at room temperature. CdFe₂O₄ shows a first cycle reversible capacity of 870 (± 10) mAhg⁻¹ at 0·07C-rate, but the capacity degrades at 4 mAhg⁻¹ per cycle and retains only 680 (± 10) mAhg⁻¹ after 50 cycles. Heat-treated electrode of CdFe₂O₄ (300°C; 12 h, Ar) shows a significantly improved cycling performance under the above cycling conditions and a stable capacity of 810 (± 10) mAhg⁻¹ corresponding to 8·7 moles of Li per mole of CdFe₂O₄ (vs theoretical, 9·0 moles of Li) is maintained up to 60 cycles, with a coulombic efficiency, 96–98%. Rate capability of heat-treated CdFe₂O₄ is also good: reversible capacities of 650 (± 10) and 450 (± 10) mAhg⁻¹ at 0·5 C and 1·4 C (1 C = 840 mAg⁻¹) are observed, respectively. The reasons for the improved cycling performance are discussed. From the CV data in 2–15 cycles, the average discharge potential is measured to be ∼0·9 V, whereas the charge potential is ∼2·1 V. Based on the galvanostatic and CV data, ex situ-XRD, -TEM and -SAED studies, a reaction mechanism is proposed. The impedance parameters as a function of voltage during the 1st cycle have been evaluated and interpreted. Dedicated to Prof. C N R Rao on his 75th birthday, and his contributions to science for the past 56 years     

Structural characterization of lead sulfide thin films by means of X-ray line profile analysis

X-ray diffraction patterns of chemically deposited lead sulphide thin films have been recorded and X-ray line profile analysis studies have been carried out. The lattice parameter, crystallite size, average internal stress and microstrain in the film are calculated and correlated with molarities of the solutions. Both size and strain are found to contribute towards the broadening of X-ray diffraction line. The values of the crystallite size are found to be within the range from 22–33 nm and the values of strain to be within the range from 1·0 × 10⁻³–2·5 × 10⁻³.     

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.     

Optical and electrical properties of SnO2 films prepared by chemical vapour deposition

Transparent and conducting SnO₂ films are prepared at 500°C on quartz substrates by chemical vapour deposition technique, involving oxidation of SnCl₂. The effect of oxygen gas flow rate on the properties of SnO₂ films is reported. Oxygen with a flow rate from 0·8–1·35 lmin⁻¹ was used as both carrier and oxidizing gas. Electrical and optical properties are studied for 150 nm thick films. The films obtained have a resistivity between 1·72 × 10⁻³ and 4·95 × 10⁻³ ohm cm and the average transmission in the visible region ranges 86–90%. The performance of these films was checked and the maximum figure of merit value of 2·03 × 10⁻³ ohm⁻¹ was obtained with the films deposited at the flow rate of 1·16 lmin⁻¹.     

Size quantization effects in optical and electrical properties of II–VI semiconductor films in nanocrystalline form

The electrical properties of CdTe and optical properties of ZnS in nanocrystalline thin film form are studied with a view to have a clearer understanding of the optical processes and the carrier transport mechanisms in nanocrystalline II–VI semiconductors, in general. Nanocrystalline ZnS and CdTe films were deposited by magnetron sputtering of respective targets in argon plasma. The optical absorption data of nanocrystalline ZnS films (thickness 10–40 nm) could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites. The conductivity of CdTe (grain size within 4–4·7 nm) showed (T ₀/T) ^p dependence withp ∼ 0·5 indicating the presence of a Coulomb gap near the Fermi level. The width of the Coulomb gap varied within 0·02–0·04 eV depending on the deposition condition. The existing theoretical models were used for estimating hopping energy (0·02–0·04 eV) and hopping distance (2·8–5·1 nm) in nano CdTe films.     

Photoelectric method of measuring the rotation period of a turbine drive shaft

The rotation period has been measured for a turbine shaft in a thermal power station by an optoelectronic method. The electronic unit is screened from electromagnetic interference at line frequency, and the fiber-optic lines provide a measurement error of 5·10⁻⁴%. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 28–29, December, 1996.     

Sorption-atomic-absorption determination of platinum,palladium, and rhodium in dead autocatalysts

The conditions for determination and group concentration of platinum metals (PMs) in the presence of matrix components using new S,N-containing complex-forming sorbents in solutions obtained after decomposition of decontaminated autocatalysts are proposed. The technique of atomic-absorption determination of PMs from a solution (n × 10⁻⁴−n × 10⁻²; s _r = 0.15–0.07) and a solid phase (n × 10⁻⁵−n × 10⁻⁴; s _r = 0.20–0.12) is developed.     

Combustion synthesis and structural characterization of Li–Ti mixed nanoferrites

Polycrystalline samples of the mixed nanoferrites, Li_{0·5 + 0·5x} Ti _x Fe_{2·5 − 1·5x} O₄ (0·02 ≤ x ≤ 0·1), were prepared by combustion method at lower temperatures compared to the conventional high temperature sintering for the first time at low temperatures, using PEG which acts as a new fuel and oxidant. XRD patterns reveal a single-phase cubic spinel structure. The as synthesized Li–Ti ferrites are in nanocrystalline phase. The crystallite size was found to be in the range 16–27 nm. SEM images reveal rod-like morphology in all the samples with a discontinuous grain growth. The B–H loops have been traced using VSM technique, for all the compositions, at room temperature and the hysteresis parameters are calculated. Saturation magnetization decreases with increase in Ti content due to the fact that the Ti^4 + ion, which is a non-magnetic ion, replaces a magnetic Fe^3 + ion. The hysteresis loops show clear saturation at an applied field of ±10 kOe and the loops are highly symmetric in nature. The cation distribution is known indirectly by using saturation magnetization values.     

Distillation Separation of Hydrofluoric Acid and Nitric Acid from Acid Waste Using the Salt Effect on Vapor–Liquid Equilibrium

This study presents the distillation separation of hydrofluoric acid with use of the salt effect on the vapor–liquid equilibrium for acid aqueous solutions and acid mixtures. The vapor–liquid equilibrium of hydrofluoric acid + salt systems (fluorite, potassium nitrate, cesium nitrate) was measured using an apparatus made of perfluoro alkylvinylether. Cesium nitrate showed a salting-out effect on the vapor–liquid equilibrium of the hydrofluoric acid–water system. Fluorite and potassium nitrate showed a salting-in effect on the hydrofluoric acid–water system. Separation of hydrofluoric acid from an acid mixture containing nitric acid and hydrofluoric acid was tested by the simple distillation treatment using the salt effect of cesium nitrate (45 mass%). An acid mixture of nitric acid (5.0 mol · dm⁻³) and hydrofluoric acid (5.0 mol · dm⁻³) was prepared as a sample solution for distillation tests. The concentration of nitric acid in the first distillate decreased from 5.0 mol · dm⁻³ to 1.13 mol · dm⁻³, and the concentration of hydrofluoric acid increased to 5.41 mol · dm⁻³. This first distillate was further distilled without the addition of salt. The concentrations of hydrofluoric acid and nitric acid in the second distillate were 7.21 mol · dm⁻³ and 0.46 mol · dm⁻³, respectively. It was thus found that the salt effect on vapor–liquid equilibrium of acid mixtures was effective for the recycling of acids from acid mixture wastes.     

Synthesis and properties of dental zirconia–leucite composites

The dental zirconia–leucite composites were synthesized by high temperature solid-state method using potash feldspar, potassium carbonate and zirconia as raw materials. The mechanical properties and the coefficient of thermal expansion (CTE) of the prepared zirconia–leucite composites were tested. The results show that the bending strength, the fracture toughness and the metal–ceramic bonding strength of the prepared samples are about 110 MPa, 3·5 MPa/m^1/2 and 45 MPa, respectively. The CTE was about 13·73×10^–6 °C^–1 and close to that of Ni–Cr dental alloy (14·0×10^–6 °C^–1). The results indicate that the introduction of zirconia is beneficial to the improvement in the mechanical properties and CTE adjustment of porcelain material. The clinical application of the zirconia–leucite composites with good metal–ceramic bonding strength in the dental restoration could be envisioned.     

Dosimetric properties of tungsten-containing complexes of carboxymethyl cellulose

A study is made of the change in the optical properties of polymer compositions based on W-containing complexes of highly substituted carboxymethyl cellulose under the action of ionizing radiation (α-particles,⁶⁰Co γ-rays). It is shown that film layers based on the complexes mentioned can be used as radiochromic materials for α-radiation dosimetry in the dose range of 4·10²–5.1·10⁵ Gy. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 443–446, March–April, 2000.     

Characterization of La1 −x Sr1 +x Cu5 −x Fe x O12 + δ (0 ≤x ≤ 1·0) by dc electrical conductivity,magnetic susceptibility and EPR measurements(0 ≤x ≤ 1·0) by dc electrical conductivity,magnetic susceptibility and EPR measurements

The DC electrical resistivity results of La_{4 −x} Sr_{1 +x} Cu_{5 −x} Fe _x O_{12 + δ} (0 ≤x ≤ 1·0) showed that for S1 (x = 0) and S2 (x = 0·25) the temperature coefficient of resistivity (TCR), dρ/dT, is positive and slightly increases with increasing temperature in the range 20–270 K. This shows the metallic nature of S1 and S2. For the samples S3(x = 0·5) and S4 (x = 0·75), TCR slightly increases in the range 20–270 K, with change in sign from negative to positive at ∼ 80 K and ∼ 130 K, respectively. These results show the metal-insulator type transition in S3 and S4. For the sample S5 (x = 1·0), the TCR is negative and gradually increases in the range 20–270 K, which shows its semiconductor-like behaviour. The activation energy for S5 is found to be 0·21 × 10⁻² eV. Furthermore, the DC resistivity results of S1–S5 in the range 350–660 K are in conformity with the low temperature results. The very weak temperature dependence of magnetic susceptibility results of S1–S3 show Pauli-paramagnetic behaviour in the range 77K–400 K, while S4 and S5 exhibit Pauli-paramagnetic behaviour in the range 77–850 K. Long-range antiferromagnetic interaction is observed in S5 (x = 1·0) belowT _c ∼ 100 K. The room temperature EPR lineshapes gradually improve from metallic S1 (x = 0) to semiconductor-like S5(x = 1·0). Negativeg-shift is observed in the samples S2–S5 with increasing trend ing _iso-values of 1·880 in S2 to 1·961 in S5. However, theg _iso-value for S1 could not be observed due to very poor lineshape.     

A laser-based automatic interference refractometer for control of the gradient of the index of refraction of plane-parallel glass elements

A laser-based fiber-optic interference refractometer for use in automatic control of the gradient of the index of refraction of large plane-parallel glass optical elements with resolution on the order of 8·10^–7 cm^–1 and absolute error at most 2·10^–5 cm^–1 is proposed.     

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.