The VNIIFTRI magnetic temperature scale in the 0.3–3 K range

A thermodynamic temperature scale in the range 0.3–3 K is established by a magnetic method. The results of investigations enable the range of the State Standard of temperature to be extended from 0.8 K to 0.3 K with a simultaneous increase in its accuracy by a factor of 2–3. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 47–53, August, 2007.     

Increasing the authenticity of the VNIIFTRI magnetic temperature scale in the range above 0.37 K by comparison with the international PLTS-2000 scale

The VNIIFTRI magnetic temperature scale is compared with the provisional low-temperature scale (PLTS-2000), based on the melting pressure of He-3, in the 0.37–0.56 K range. The magnetic temperature scale is reproduced from the readings of a rhodium-iron alloy resistance thermometer. The disagreement between the scales does not exceed 0.23 mK.     

Investigation of the temperature dependence of the effective wavelength of a standard photoelectric pyrometer

A method of determining the temperature dependence of the effective wavelength of a photoelectric pyrometer, intended for standard operation in realizing a temperature scale by optical methods, is described and results are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 52–55, September, 2007.     

Apparatus for realizing the ITS-90 in the temperature range from the triple point of argon to the melting point of gallium

Systems for realizing the fixed points of the ITS-90 for calibrating column and capsule standard platinum thermometers, namely, the triple points of argon and mercury and the melting point of gallium, are constructed and investigated. The errors of the values of the metrological characteristics of the systems obtained enable one, using platinum resistance thermometers, to reproduce and transfer the temperature scale in the 83.8–302.9 K range. The extended uncertainty in reproducing the temperatures of the fixed points does not exceed 0.4 mK. This paper has been prepared from the contributions presented at the 3rd All-Russia Conference “Temperature 2007”; see the selection of papers in Measurement Techniques, Nos. 8 and 9, 2007. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 26–31, November, 2007.     

Upscaling the synthesis of biodegradable multiblock copolymers capable of a shape-memory effect

Thermoplastic, phase-segregated multiblock copolymers (MBC) with shape–memory capability consisting of poly(ε-caprolactone) (PCL) switching segments and poly(p-dioxanone) (PDO) or poly(ω-pentadecalactone) (PPD) hard segments were prepared on a scale of several kilograms following a newly developed upscaling procedure. Dihydroxytelechelic poly(ether)esters were coupled by an aliphatic diisocyanate gaining products of sufficiently high molecular weights. The obtained biodegradable MBC exhibited good elastic properties and a shape–memory effect (SME) with a switching temperature (T _sw) around body temperature. The yield of the synthesis could be improved and reaction time reduced, while mechanical and shape–memory properties were not affected. These multifunctional materials, which are now available in a larger scale have a high application potential as smart implant materials especially for minimally invasive surgery.     

Investigation of microhardness and thermo-electrical properties in the Sn–Cu hypereutectic alloy

Sn–3 wt% Cu hypereutectic alloy was directionally solidified upward with different growth rates (2.24–133.33 μm/s) at a constant temperature gradient (4.24 K/mm) and with different temperature gradients (4.24–8.09 K/mm) at a constant growth rate (7.64 μm/s) in the Bridgman-type growth apparatus. The measurements of microhardness of directionally solidified samples were obtained by using a microhardness test device. The dependence of microhardness HV on the growth rate (V) and temperature gradient (G) were analyzed. According to these results, it has been found that with the increasing the values of V and G the value of HV increases. Variations of electrical resistivity (ρ) and electrical conductivity (σ) for casting samples with the temperature in the range of 300–500 K were also measured by using a standard dc four-point probe technique. The variation of Lorenz coefficient with the temperature for Sn–3 wt% Cu hypereutectic alloy was determined by using the measured values of electrical and thermal conductivities. The enthalpy of fusion for same alloy was determined by means of differential scanning calorimeter from heating trace during the transformation from eutectic liquid to eutectic solid.     

The effect of covariance on uncertainty when constructing the ITS-90 temperature scale

The effect of covariance between the resistances of a calibrated standard platinum resistance thermometer at the fixed points on the uncertainty when constructing the ITS-90 temperature scale in the 0–660°C range is considered. The proposed method of calculating the uncertainty complies with the international recommendations. This paper was presented at the 3rd All-Russia Conference “Temperature-2007” (see the selection in Measurement Techniques, Nos. 8, 9, 11, 2007). __________ Translated from Izmeritel’naya Tekhnika, No. 4, pp. 44–49, April, 2008.     

Prediction of the temperature dependence of fracture toughness of 12Cr–2Ni–Mo refractory steel

We study the influence of temperature and the size of the specimens on the characteristics of static crack resistance of 12Cr–2Ni–Mo refractory steel. It is shown that, in the temperature range 20–450°C, the increase in the thickness of specimens leads to an insignificant increase in fracture toughness obtained along a 5% secant line according to the standards of evaluation of the characteristics of crack resistance. The evaluation of the characteristics of crack resistance of 12Cr–2Ni–Mo steel with regard for the scale effect according to an earlier developed numerical-experimental model reveals the existence of satisfactory agreement with the experimental data in the entire investigated temperature range. Translated from Problemy Prochnosti, No. 4, pp. 78–88, July–August, 2009.     

Equipment for the Spectral Characterization of High-Temperature Particles

The spectral radiant characteristics of plume particles of a solid rocket engine are important in the design of the engine specific impulse, ablative material, and plume flame hiding. These parameters are measured from tests of the engine. Some equipment has been established to realize particle heating, uniform particle distribution, and measurements based on an FTIR spectral instrument. The equipment is based on SiC heating and is divided into a warm-up chamber and a measurement chamber to improve the particle temperature stability. A special design of uniform particle distribution combined with an acoustic levitation device is used to determine the particle falling speed. The spectral characteristics and the transmission rate of the particles have been measured by using the system including a standard blackbody, an assembled optical system, and an FTIR spectrometer. The measurements of particle concentration and temperature are given in detail. The instrument specifications are as follows: temperature range – 60–1500 °C; spectral range – 0.60–25 μm; and particle dimension range – 10–500 μm. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.     

Effect of the La<Subscript>2</Subscript>O<Subscript>3</Subscript> sol–gel coating on the alumina scale adherence on a model Fe–20Cr–5Al alloy at 1100 °C

The effect of lanthanum sol–gel coatings was studied in order to improve the alumina scale adherence during the model Fe–20Cr–5Al alloy oxidation, at 1100 °C, in air. Various sol–gel coating procedures were applied. Argon annealing of the lanthanum sol–gel coating was tested at temperatures ranging between 600 and 1000 °C. The coating crystallographic nature was characterized by X-ray diffraction (XRD) depending on the annealing temperature. The oxidation process has been examined at 1100 °C by in situ XRD on blank Fe–20Cr–5Al, sol–gel coated and argon-annealed specimens. This study shows that the coating argon annealing at 1000 °C leads to the preferential formation of LaAlO₃ instead of La₂O₃. This coating procedure leads to an alumina scale formation showing the best adherence under thermal cycling conditions at 1100 °C.     

The Influence of the Interaction Potential on the Diffusion of Neutral Particles in Oxyfluoride Glasses

A systematic study of the effects of the interaction potential upon the diffusion coefficients of neutral particles (P0s) and ions in the 60GeO₂–40PbF₂ glass has been performed using molecular dynamics simulations. The P0–P0 and P0–ions pair potentials were described by a Lennard–Jones potential with two parameters: the well depth (ε) and the size (σ). These parameters were varied in the ranges: (σ) = 0.1-1.0 eV and σ=1.0−4.0 ?. The diffusion coefficients were calculated for several combinations at several temperatures (300–1200 K). The estimated glass transition temperature (T _g) presented a slight dependence upon the potential parameters, but it is near the crystallization temperature of a glass of similar composition. Whereas, the diffusion coefficients of the P0s presented a strong dependence with the potential parameters, where increasing ε and σ causes a decrease of their diffusion coefficients. These results suggest that the atoms should be responsible for forming any surface film, since neutral particles larger than atom, such as, nanoparticles, should have negligible diffusion.     

About temperature dependence of the rheological properties of human blood at low shear rates

Measurements of the human blood flow curve as a function of temperature are reported. The blood was sampled from healthy donors. The measurements were made at the shear rates from 0.2 to 5.0 sec⁻¹ in the temperature range 30–45°C. The blood flow curve was investigated by the nonstationary measurement method using a specially designed viscosimeter. An experimental study of the human blood flow curve at low shear rates allowed investigation of the temperature dependence of the Casson’s model parameters describing it. It is shown that these parameters have a complicated temperature dependence that exhibits a specific feature at 42°C. Academic Scientific Complex “A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 3, pp. 386–389, May–June, 1996.     

Investigation of the thermal and structural properties of single-molecule magnet/polymer nanocomposite films

The inclusion of manganese-based single-molecule magnets (SMMs) into solvent cast films of poly(methyl methacrylate) (PMMA) or polycarbonate (PC) was found to influence the thermal stability of these polymers. Examination of the thermal decomposition profiles of PMMA films by thermo-gravimetric analysis (TGA) established that increasing weight % of SMM results in both enhancement of the rate of decomposition initiated at “head-to-head” linkages along with suppression of the rate of decomposition initiated at vinylidene chain ends. In the case of PC films, the temperature at which the primary thermal decomposition occurs decreases with increasing weight % of SMM. The extent of these decomposition trends is correlated to the degree of SMM dispersal, as studied by transmission electron microscopy (TEM). Favourable interactions between the ligands coordinated to the SMMs and the polymer or solvent used in film preparation dictated the degree of SMM dispersal, with the ligand–polymer interactions being dominant on the nano-length scale (1–100 nm) and ligand–solvent interactions being dominant on the micro-length scale (>100 nm).     

Oxidation behavior and electrochemical corrosion performance of Ti<Subscript>3</Subscript>Al alloy with TiAl coating

Magnetron-sputter deposition was used to produce a Ti–48Al–8Cr–2Ag (at. %) coating on a Ti–24Al– 17Nb–0.5Mo (at. %) alloy substrate. Oxidation behavior was studied in air at 900–1000°C. The results indicated that the oxidation rate of sputtered Ti–48Al–8Cr–2Ag nanocrystalline coating was lower than that of the Ti₃Al alloy at 900°C. The former formed a scale of merely Al₂O₃, and the latter formed a scale of TiO₂. However, the Ti–48Al–8Cr–2Ag nanocrystalline coating showed a little bit higher oxidation rate than Ti₃Al alloy at 1000°C because the outer TiO₂ scale formed and columnar boundaries of the coating gave a larger actual oxidation area than the original alloy. The electrochemical corrosion behavior was investigated in a 3.5% NaCl solution at room temperature. The coating showed excellent electrochemical corrosion resistance in 3.5% NaCl solution because it exhibited stable passive polarization behavior without any overpassivation phenomena.     

Monitoring of the characteristics of Josephson microcircuits used in standards of the volt

The results of investigations of microcircuits based on Nb−AlO_x−Nb Josephson tunnel junctions, used in modern standards of the volt, are presented. The measured static characteristics of the microcircuits, their temperature dependences in the 4.2–1.7 K temperature range, the frequency response in the 54–80 GHz frequency band, and the attenuation in a microstrip line are used to optimize the construction of microcircuits and their manufacturing technology at PTB (Physikalisch-Technische Bundesanstalt, Germany). It is shown that microcircuits of a new construction, made using a modified PTB technology, have better characteristics and can be used as the unit of voltage at the level of both 1 V and 10 V. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 43–48, November, 1997.     

Optimizing the Implementation of High-Temperature Fixed Points through the Use of Thermal Modeling

High-temperature fixed points (HTFP) have the potential to make a step-change improvement in high-temperature metrology, significantly reducing the uncertainty of scale realization of the current ITS-90 and improving dissemination of high-temperature scales to industry. However, in a practical implementation, the performance of HTFP could be limited, by, for example, injudicious use of insulation in the vicinity of the fixed point, furnace gradients, or incomplete filling. This article investigates some of these aspects for a selection of HTFP. Steady-state modeling of the influence of insulation on the radiance temperature was performed for Co–C (1,324°C), Pd–C (1,492°C), Pt–C (1,738°C), Ru–C (1,953°C), and Re–C (2,474°C) fixed points. This included studying mitigation scenarios through the insertion of different types and designs of insulation. The optimum design was identified to minimize the temperature drop in a particular furnace. It was found that, for the furnace and fixed-point combination modeled, the actual effect of the insulation was almost insignificant. Transient modeling was performed for a Re–C fixed point, to track the evolution of the radiance temperature through the melting transition. The starting point of the model was the beginning of the melt. The evolution of radiance temperature with time in “perfectly” filled cells was modeled with a range of linear temperature gradients across the eutectic cell. The gradient had a significant effect on the duration of the transition and on the structure of the melt itself. Despite the model’s simplicity, it qualitatively demonstrated that the melt transition temperature, as identified by the point of inflection, could be significantly affected by the presence of furnace gradients.     

Experience of Construction and Study of Pt–C Eutectic in VNIIM and Cooperation with LNE-INM

A new high-temperature furnace was developed in VNIIM and manufactured by the Omsk plant “Etalon.” This furnace is intended for the realization of various fixed points of pure metals and high-temperature metal–carbon eutectics up to a temperature of 3000°C. The construction of the furnace allows measurements to be carried out either with or without the protective window, in a protective atmosphere of argon. The furnace will be described in this article. Cooperation with LNE-INM was initiated with the aim of sharing experience in metal–carbon eutectic cell construction and comparing two Pt–C cells (one cell was made by each partner) as a means of comparing scale realizations around 1740°C. The filling technique used in each laboratory will be described. The average melting temperature of the VNIIM Pt–C eutectic cell, characterized and studied at VNIIM, was 1738.4°C with a standard uncertainty of about 0.13 K. The repeatability of the melting temperature with various measurements was estimated to be within the limits of (0.02–0.2) K. The cell supplied by LNE-INM is the one that was constructed and studied in the framework of the HIMERT European project and described elsewhere. The difference in the melting temperatures of the fixed points (VNIIM—LNE-INM) is about 0.4 K with a standard uncertainty not exceeding 0.18 K. The cells constructed and characterized by each partner were exchanged and measured by the other partner. The results of the study of the melting and freezing of the Pt–C cells carried out by VNIIM and LNE-INM will be presented. The reasons for the difference in the melting temperatures of the two cells are analyzed, and the steps preceding the comparison of the scale realizations of the two laboratories are presented.     

Synthesis of non-equilibrium phases in immiscible metals mechanically mixed by high pressure torsion

The structural changes in mechanically mixed metals of immiscible combinations of elements caused by bulk mechanical alloying (MA) through the use of high pressure torsion (HPT) were investigated in Ag–Ni and Nb–Zr systems. There was no alloying between Ag and Ni on atomic scale even after 100 rotations of HPT. On the other hand, the β-Zr phase started to appear after HPT 2 rotations in the Nb–Zr system, even though β-Zr is a high temperature phase. Further, Nb and Zr were completely mixed to form a bcc structured single phase after HPT 100 rotations. The sequence of alloying in the Nb–Zr system during HPT was discussed. These results clearly suggest that non-equilibrium phases can form in the Nb–Zr system by bulk MA by the use of HPT.     

Injectable thermosensitive hydrogel based on chitosan and quaternized chitosan and the biomedical properties

A novel injectable thermosensitive hydrogel (CS–HTCC/α β-GP) was successfully designed and prepared using chitosan (CS), quaternized chitosan (HTCC) and α,β-glycerophosphate (α,β-GP) without any additional chemical stimulus. The gelation point of CS–HTCC/α β-GP can be set at a temperature close to normal body temperature or other temperature above 25°C. The transition process can be controlled by adjusting the weight ratio of CS to HTCC, or different final concentration of α,β-GP. The optimum formulation is (CS + HTCC) (2% w/v), CS/HTCC (5/1 w/w) and α,β-GP 8.33% or 9.09% (w/v), where the sol–gel transition time was 3 min at 37°C. The drug released over 3 h from the CS–HTCC/α,β-GP thermosensitive hydrogel in artificial saliva pH 6.8. In addition, CS–HTCC/α,β-GP thermosensitive hydrogel exhibited stronger antibacterial activity towards two periodontal pathogens (Porphyromonas gingivalis, P.g and Prevotella intermedia, P.i). CS–HTCC/α, β-GP thermosensitive hydrogel was a considerable candidate as a local drug delivery system for periodontal treatment.     

Software/hardware system for automatic monitoring of rectification

Creation of software is considered for visual monitoring of changes in temperature profile with the aim of studying the efficiency of rectification. The dynamics of the temperature profile over the height of a rectification column are displayed on a monitor screen on a real time scale. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 63–65, October, 2007.