Optical and electrical properties of soluble copolymers of pyrrole-thiophene-3-decylthiophene

Three novel soluble copolymers of pyrrole(P)-thiophene(T)-3-decylthiophene (D) at different molar ratio of comonomers 4 : 1 : 5, 1 : 4 : 5 and 1 : 1 : 2 have been synthesized. NMR, FTIR, UV, emission spectroscopy, GPC, DSC, TGA and conductivity measurements were used to characterize these copolymers. The dark electrical conductivity increases from 3–7 × 10^–6 S/m for undoped samples to 10^–1–10^–2 S/m for samples doped with 4% of iodine, and to 10–10² S/m for 16% of iodine in a form of I₃ ^–.     

High thermal expansion KAlSiO4 ceramic

Orthorhombic kalsilite (KAlSiO₄) was prepared by solid-state reaction from K₂CO₃, Al₂O₃, and SiO₂. The axial thermal expansion coefficients of the orthorhombic kalsilite were 1.6×10^–5°C^–1 for the a-axis, 1.6×10^–5°C^–1 for the b-axis, 2.8×10^–5°C^–1 for the c-axis, and 2.0×10^–5°C^–1 for the average from room temperature to 1000°C. A high thermal expansion ceramic consisting of the orthorhombic kalsilite was prepared by sintering. The densification was promoted by adding Li₂CO₃. The KAlSiO₄ ceramic sintered at 1200°C for 2 h with 5 wt% Li₂CO₃ had a bending strength of 65 MPa and linear thermal expansion coefficient of 2.2×10^–5 °C^–1 from room temperature to 600°C.     

Additional frequency errors due to the transmission of electrical oscillations

Conclusions Existing data shows that all the elements of the circuit, whether propagating or transforming oscillations, introduce frequency errors in the transmitted signals. The relative errors due to the frequency divider is 10^–8 to 10^–10 and frequency multipliers 10^–12 to 10^–13[5]. Wire lines introduce an error of 1 · 10^–8 to 1 · 10^–9, depending on their type and the frequency transmitted.Radio transmitted signals acquire additional frequency errors depending on the frequency transmitted and the distance of propagation. Thus low frequency transmissions are accompanied by relative errors of the order of 1 to 5 · 10^–9 and high frequency ones by errors varying from 1 · 10^–8 (if the transmitting and receiving ends are not separated by the rising or setting sun) to 10 · 10^–8 (if the transmitting and receiving ends are separated by the rising or setting sun).The existing accuracy of the standard frequency oscillations and the prospects of its further improvement by using resonance absorption frequencies of various atoms and molecules make it imperative to investigate on a wide scale the circuits and propagation media used in conveying the signals to their users.     

Superplasticity of mullite-zirconia composite

Tension tests of mullite-zirconia composite were conducted at elevated temperature. A superplastic elongation of 122% could be achieved at an initial strain rate of 2.86×10^–5s^–1 at 1550°C. Strain hardening was observed at strain rates from 1.42×10^–4 to 2.86×10^s–5s^–1 at 1550°C. The addition of zirconia grains to the mullite matrix increased the creep rate of the composite.     

Electronic Conduction in the Na2O ·nAl2O3–Y2O3 System

The electronic conductivity of Na₂O · nAl₂O₃–Y₂O₃ materials is found to vary from 10^–5 to 10^–1 S/m between room temperature and 800°C and to increase from 10^–5 to 10^–4 S/m as the frequency increases from 100 Hz to 200 kHz. The temperature variation of conductivity is interpreted in terms of the energy band structure.     

Cyclic surface deformation behaviour of ZrH2-purified iron: Effects of solute carbon,strain amplitude,strain rate and environment

The surface deformation behaviour in ZrH₂-purified interstitial-free iron was studied during fatigue in the push-pull plastic strain control mode under various combinations of plastic strain amplitude (5×10^–4, 5×10^–3), strain rate (5×10^–4, 3× 10^–2s^–1) and environment (ultrahigh vacuum, oxygen). Comparative tests of vacuum-melted commercially pure iron (CPI) containing 170 p.p.m. C were also conducted to investigate the effect of interstitials. At a plastic strain amplitude of 5×10^–4, the environmental effect is clearly exhibited regardless of the strain rate and the presence of interstitials. Fatigue in ultrahigh vacuum produces very fine slip lines not only in interstitial-free iron but also in vacuum-melted CPI. In the presence of oxygen, fatigue produces prominent slip lines, but those developed in CPI are more intense and coarser than those developed in interstitial-free iron. At the higher plastic strain amplitude of 5×10^–3, the gaseous environmental effect on the cyclic surface deformation is insignificant. The surface deformation behaviour is discussed in terms of the environmental effect and the basic mechanisms that govern the cyclic plasticity of iron.     

Uniaxial strain rate effects in pharmaceutical powders during cold compaction

The results of uniaxial compression tests on some pharmaceutical powders subjected to strain rates of between 10^–3 and 10⁵ s^–1 are given. The tests fall into three main categories: low-strain-rate tests (10^–3–10 s^–1) performed on a servohydraulic variable speed-compression machine at constant compression rate; medium-strain-rate tests (10²–10³ s^–1) carried out on a drop hammer; and high strain rate tests (10³–10⁵ s^–1) performed on a high-pressure air projectile launcher compaction apparatus. Axial and radial pressures, as well as displacement-time measurements, are made. Powders tested include: Dipac sugar; sodium chloride; potassium bromide; lactose; paracetamol d.c.; avicel; calcium phosphate; and copper sulphate. The influence of compression rate on the form of the characteristic pressure-density and radial-axial pressure relationships during uniaxial straining is presented. The investigation showed that the general tendency for all powders tested, except for paracetamol d.c., is to exhibit increased compaction pressure with strain rate up to 10⁵ s^–1. Due to morphological and compositional effects, paracetamol d.c. softens with the rate of straining up to about 10² s^–1 and at higher rates it behaves like other powders. Also the mean radial pressure at the die wall (obtained by a pin-type transducer) shows that the friction conditions are variable during the process, and their effect tends to decrease as the speed of compaction increases, resulting in more uniform density compacts. Finally, by observing the decay of both axial and radial pressures with time under constant volume conditions, a reasonably linear behaviour is obtained for all materials tested, particularly the axial relaxation curves, over the period recorded.     

State primary standard for the unit of direct current,the ampere

The new state primary standard for direct current is described, together with its block diagram and accuracy parameters. The accuracy of realization is improved by two orders of magnitude (standard deviation 5–10^–8, residual systematic error 2·10^–7). The range of current realization in the standardis extended to 10^{–16 A}.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 3–4, January, 1995.     

Supplies for standard temperature lamps from rectifiers

Conclusions The current through a standard temperature lamp should not vary during measurements by more than 4·10^–5–7·10^–5 times its value to limiterror in reproducing temperature to 0.1°. The ripple factor should not exceed 10^–3 at 50 Hz, and 10^–2 at 300 Hz and higher frequencies.These requirements are met by a rectifier operating from three-phase mains with frequency doubling and a voltage stabilizer type U1199.The complete power pack is small and it is simpler and less expensive than the storage batteries used at the present time for feeding standard temperature lamps.     

Influence of loading rate on the mechanical properties of steels of different strength levels

The results are presented of mechanical tensile and shear tests of steels of different strength levels with plastic strain rates of 3·10^–3–10⁵ sec^–1. The changes in the characteristics of strength, plasticity, and microstructure are analyzed in relation to the strength level of the steel and loading rate. For steels of different structural classes at high deformation rates (approximately up to 10⁵ sec^–1) a significant increase in the characteristics of strength and plasticity is observed.Institute of Problems of Strength, Academy of Sciences of the Ukrainian SSR, Kiev, Leningrad. Translated from Problemy Prochnosti, No. 10, pp. 42–48, October, 1989.     

Small polaron transport in V2O5–NiO–TeO2 glasses

Semiconducting glasses of the V₂O₅–NiO–TeO₂ system were prepared by the press-quenching method and their d.c. conductivities in the temperature range 300–450 K were measured. The d.c. conductivities at 395 K for the present glasses were determined to be 10^–7 to 10^–1 S m^–1, indicating that the conductivity increased with increasing V₂O₅ concentration. A glass of composition 67.5V₂O₅–2.5NiO–30TeO₂ (mol %) having a conductivity of 2.47×10^–2 S m^–1 at a temperature of 395 K was found to be the most conductive glass among the vanadium-tellurite glasses. From the conductivity–temperature relation, it was found that a small polaron hopping model was applicable at the temperature above _D/2 (_D: the Debye temperature); the electrical conduction at T>_D/2 was due to adiabatic small polaron hopping of electrons between vanadium ions. The polaron bandwidth ranged from 0.06 to 0.21 eV. The hopping carrier mobility varied from 1.1×10^–7 to 5.48×10^–5 cm² V^–1 s^–1 at 400 K. The carrier density is evaluated to be 1.85×10¹⁹–5.50×10¹⁹ cm^–3. The conductivity of the present glasses was primarily determined by hopping carrier mobility. In the low-temperature (below _D/2) regime, however, both Mott's variable-range hopping and Greaves intermediate range hopping models are found to be applicable.     

Quasi-static and dynamic compression behaviour of an FPTM alumina-reinforced aluminium metal matrix composite

An aluminium metal matrix composite reinforced with continuous unidirectional -alumina fibres has been compression tested at quasi-static and dynamic strain rates. In the transverse direction, the composite showed increasing flow stress (at 5% strain) and maximum stress within the studied strain rates, 10^–3–3 × 10³ s^–1. In the longitudinal direction, the maximum stress of the composite increased similarly with increasing strain rates within the range 10^–5–7 × 10² s^–1. It is shown that, if brooming of the sample ends can be suppressed, the failure stress of the composite in longitudinal compression increases significantly. Metallographic observations reveal the typical modes of damage initiation in the composite.     

Low temperature stress relaxation of nanocrystalline nickel

Stress relaxation in nanocrystalline nickel within the temperature range 523–673 K in a uniaxial compression regime is studied in the present investigation. The results obtained for coarser grained nickel are given for comparison. An average strain rate of nanocrystalline nickel within the investigated range of temperatures is 1.75 × 10^–5–3.03 × 10^–5s^–1. The presence of two types of stress relaxation dependencies are shown. The most likely strain mechanism is grain boundary sliding controlled by grain boundary diffusion for temperatures between 623 and 673 K.     

High-temperature thermoelectric properties of the sintered Bi2Sr2Ca1 − xYxCu2Oy (x = 0 – 1)

Electrical conductivity and Seebeck coefficient were measured in a temperature range of 320–1073 K for sintered samples of Bi₂Sr₂Ca_{1 – x} Y _x Cu₂O _y (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). It has been found that the conduction behavior changes from n-type metallic to p-type semiconducting with increasing yttrium concentration. The power factors were in a range of 1.7–3.0 × 10^–5 Wm^–1 K^–2 for the sample with x = 0.8, being maximized by the optimization of the yttrium concentration. The thermal conductivity for the sample with x = 0.8 was 0.73 Wm^–1 K^–1 at 310 K, and decreased with increasing temperature. The values of thermoelectric figure of merit were estimated to be in a range of 3.4–4.8 × 10^–5 K^–1 at temperatures of 320–673 K for the sample with x = 0.8.     

Dielectric spectra of fresh cement paste below freezing point using an insulated electrode

The spectra of complex dielectric constant were measured on a fresh cement paste with a water/cement ratio of 0.4 sandwiched between insulated electrodes in the frequency range 10 kHz–1 MHz and temperature range between 0 °C and — 30 °C. The bulk dielectric constant, 30–20, and conductivity, 6.14×10^–5–0.65×10^–5, in the temperature range –10 to –28 °C were much lower than those at room temperature, owing to the great decrease of ionic mobility caused by freezing the cement paste. The activation energy of 0.31 eV for the ionic conduction in fresh cement paste was obtained from an Arrhenius plot of conductivity at subzero temperature.     

Diffusion of alcohol-rhodamine 6G in polymethyl methacrylate

Rhodamine 6G (Rh6G) is impregnated in polymethyl methacrylate by concentration difference diffusion method. The diffusion behaviour of ethanoic and methanoic Rh6G in polymethyl methacrylate at temperatures between 35 and 70° C were studied. The following results were obtained: (a) Visually observed sharp boundary, characteristic of Case II transport, during diffusion of alcohol penetrates at a rate of 1.7×10^–6 cm sec^–1 with an activation energy of 23 kcal mol^–1 for ethanol-polymethyl methacrylate system and 1.0×10^–5 cm sec^–1, with 23 kcal mol^–1 for methanol-polymethyl methacrylate, respectively, at 60° C. (b) Diffusion of alcoholic Rh6G in polymethyl methacrylate is greatly hindered since internal stresses exist in the swollen region of the glassy polymer. (c) Diffusion of alcoholic Rh6G in swollen polymethyl methacrylate with equilibrium alcohol concentration followed Fickian kinetics. The diffusion coefficient of Rh6G at 60° C is determined as 5.2×10^–8 cm² sec^–1 with an activation energy of 41 kcal mol^–1 for the wet ethanol-polymethyl methacrylate and 6.1×10^–8 cm² sec^–1, with 34 kcal mol^–1 for the wet methanol-polymethyl methacrylate systems, respectively.     

Oxidation-reduction equilibria of vanadium in CaO-SiO2, CaO-Al2O3-SiO2 and CaO-MgO-SiO2 melts

A series of redox studies of vanadium have been carried out in CaO-SiO₂, CaO-MgO-SiO₂ and CaO-Al₂O₃-SiO₂ melts/slags equilibrated over oxygen partial pressures (pO₂) range 10^–2–10^–9 atm at 1600°C. V₂O₅ level was varied from 1–5 mol%. Three different melt basicities and alumina contents were investigated. Magnesia content was varied between 3.5 and 4.9 wt%. A newly developed analytical technique based upon electron paramagnetic resonance (EPR) spectroscopy was successfully applied to these melts. Two redox equilibria corresponding to V³⁺/V⁴⁺ and V⁴⁺/V⁵⁺ pairs followed the O-type redox reaction over the oxygen partial pressure range investigated. Higher oxidation states of vanadium were stabilized with increasing basicity of slags. Two redox pairs coexisted within oxygen pressure region 10^–4–10^–6 atm. However, redox ratios did not indicate clear trends with increasing V₂O₅ content in CaO-SiO₂-V₂O₅ system. In CaO-SiO₂-Al₂O₃-V₂O₅ slags, a slight increase in redox ratios (V³⁺/V⁴⁺) was obvious when alumina quantity was changed from 3.22 to 5.44% at a basicity ratio 1.3, indicating an increase in slag acidity. CaO-MgO-SiO₂-V₂O₅ slags showed a sharp decrease in redox ratios (V⁴⁺/V⁵⁺) between 10^–2–10^–6 atm with addition of 3.5 wt% MgO, due to increasing free oxygen ions in slags.     

Cooling rate measurements on pure iron rapidly solidified by piston quenching

Cooling curves have been monitored during rapid solidification of pure iron, using a rapid response thermocouple embedded in one of the quenching pistons. Cooling rates are found to be typically 10⁶ to 10⁷ K sec^–1 in the vicinity of the solidification point at 1500° C, falling to 2 × 10⁴ to 3 × 10⁵ K sec^–1 at 500° C. Heat-flow analysis shows that cooling conditions during rapid solidification are clearly non-Newtonian, with heat transfer coefficients of 3 × 10⁵ to 6 × 10⁵Wm^–2 K^–1 and Nusselt numbers of 0.5 to 1.0. Cooling rates, heat transfer coefficients and Nusselt numbers are higher for piston quenching than for other rapid solidification processes such as melt spinning. Piston-quenched iron microstructures can be ferritic or martensitic depending on the cooling rate during rapid solidification.     

Deformability enhancement in ultra-fine grained, Ar-contained W compacts by TiC additions up to 1.1%

Nano-sized Ar bubbles give negative influence on the fracture resistance and occurrence of superplasticity in ultra-fine grained (UFG) W–TiC compacts. In order to enhance deformability in UFG, Ar-contained W–TiC compacts, effects of TiC addition on the high-temperature deformation behavior were examined. W–TiC compacts with TiC additions of 0, 0.25, 0.5, 0.8 and 1.1 wt% were fabricated by mechanical alloying in a purified Ar atmosphere and hot isostatic pressing. Tensile tests were conducted at 1673–1973 K (0.45–0.54 T_m, T_m: melting point of W) at initial strain rates from 5 × 10⁻⁵ to 5 × 10⁻³ s⁻¹. It is found that as TiC addition increases, the elongation to fracture significantly increases, e.g., from 3 to 7% for W–0 and 0.25TiC/Ar to above 160% for W–1.1TiC/Ar when tested at 1873 and 1973 K at 5 × 10⁻⁴ s⁻¹. The flow stress takes a peak at 0.25%TiC and decreases to a nearly constant level at 0.5–1.1%TiC. The ranges of the strain rate sensitivity of flow stress, m, and the activation energy for deformation, Q, with TiC additions are 0.17–0.30 and 310–600 kJ/mol, respectively. The observed effects of the TiC additions on the tensile properties are discussed.     

Pulsations in boundary pressure in the flow of a plane turbulent jet onto a surface

Results are presented on an experimental study of root-mean-square values of pulsations in boundary pressure when a plane turbulent jet flows onto a plane surface in the ranges of Reynolds numbers Re_n of 0.7·10⁵–2.1·10⁵, distances x/d of 19–43, and angles of impingement of 0–90°.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 2, pp. 204–208, February, 1977.