Rheology and microstructure of MDI–PEG reactive prepolymer-modified bitumen

This paper deals with the use of a new bitumen modifier, a reactive prepolymer, based on the reaction of 4,4^′-diphenylmethane diisocyanate (MDI) and a low molecular weight polyethylene glycol (PEG). The rheological and thermal behaviours of modified bitumen containing a low MDI–PEG concentration, as well as its morphology, have been studied. A relatively low amount of MDI–PEG (0.5 to 1.5% wt.) yields a significant improvement in the modified bitumen rheological properties, mainly in the high in-service temperature region. In this range of temperature, the rheological properties are clearly affected by curing time at room temperature. These results indicate that chemical changes, due to the reaction of MDI isocyanate groups with the most polar groups (–OH; –NH) of asphaltenes and resins, are produced. Thus, new chemical structures, non-visible by optical microscopy, slowly develop in MDI–PEG modified bitumen when samples are cured at room temperature.     

Investigation of Furnace Uniformity and its Effect on High-Temperature Fixed-Point Performance

A large-area furnace BB3500YY was designed and built at the VNIIOFI as a furnace for high-temperature metal (carbide)–carbon (M(C)–C) eutectic fixed points and was then investigated at the NMIJ. The dependence of the temperature uniformity of the furnace on various heater and cell holder arrangements was investigated. After making some improvements, the temperature of the central part of the furnace was uniform to within 2K over a length of 40 mm—the length of the fixed-point cell—at a temperature of 2,500°C. With this furnace, the melting plateaux of Re–C and TiC–C were shown to be better than those observed in other furnaces. For instance, a Re–C cell showed melting plateaux with a 0.1K melting range and a duration of about 40 min. Furthermore, to verify the capability of the furnace to fill cells, one Re–C and one TiC–C cell were made using the BB3500YY. The cells were then compared to a Re–C cell made in a Nagano furnace and a TiC–C cell filled in a BB3200pg furnace. The agreement in plateau shapes demonstrates the capability of the BB3500YY furnace to also function as a filling furnace. B. Khlevnoy and K. Anhalt are guest scientists at NMIJ at the time of investigation.     

Temperature and dwell time effect on hardness of Al-base alloys

The hardness of Al–5wt%Zn (alloy A) and Al–5wt%Zn–0.25wt%In (alloy B) was measured at room temperature for samples heat treated in the range 300–453 K and dwell times in the range 30–300 s under 50 gm load. Softening was observed for all the samples and the hardness decreased with increasing temperature and/or dwell time. Hardness drop was larger for alloy (B), which in general showed higher hardness than alloy (A). The stress exponent n increased with increasing temperature and showed high values falling in the power law breakdown region. The parameters deduced from the analysis of X-rays data and micrographs were found to be consistant with the calculated mechanical data.     

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.     

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.     

Strong correlation between the cation ordering and magnetic properties of anodically electrodeposited Mn–Co–O nanocrystals

The rock salt-to-spinel structural transformation that occurs in anodically electrodeposited Mn–Co–O nanocrystals involves a rearrangement of Mn/Co cations from octahedral interstices to tetrahedral interstices. The cation ordering process leads to distinct magnetic properties. Curie temperature (T _C) and blocking temperature (T _B) increase dramatically with annealing temperature (200–400 °C), while the corresponding change in particle size for the oxide nanocrystals is rather small. A strong correlation between the magnetic properties and the cation ordering degree in annealed Mn–Co–O nanocrystals was established. These unique magnetic properties can be attributed to the magnetic moment changes induced by Mn/Co cation ordering from octahedral interstices to tetrahedral interstices in the annealed Mn–Co oxide nanocrystals.     

Effect of preheating on the mechanical properties of tough pitch copper made from copper scraps

When hot rolled tough pitch copper is made from copper scraps, lead is intentionally or unintentionally added to the melt. The major role of this lead seems to be the removal of metallic tin by the formation of PbO–SnO₂. A continuously cast and hot rolled copper rod was preheated at temperatures between 673–1173 K for 1 h prior to cold drawing. The maximum diameter of the PbO–SnO₂, of 1–2 μm, was obtained by preheating at 873 K. This preheating temperature also produced the maximum decrease in the recrystallization temperature and the maximum electrical conductivity of the 89.4% cold drawn wire within the investigated experimental range. This can be attributed to a decrease in the dissolved impurity concentration due to the growth of PbO–SnO₂ particles at that temperature. The decrease in recrystallization temperature enhanced the room temperature multiple upset weldability. When preheated at 1173 K, Zn₂SnO₄ particles were formed, but the recrystallization temperature increased and the electrical conductivity decreased due to the dissolution of PbO–SnO₂. This revised version was published online in November 2006 with corrections to the Cover Date.     

Strength and Plasticity of Metal and Nonmetallic Composites for Cryogenic and Aerospace Purposes

We present results of studying mechanical properties of four groups of metallic and nonmetallic composite materials in a temperature range of 300–4.2 K. Types of glass-reinforced and carbon-reinforced plastics with the best low-temperature strength and elastic characteristics have been specified. A deterioration of the strength characteristics of boron-fiber-reinforced aluminum alloy after temperature cycling in the temperature range 20–443 K has been detected. It has been shown that superconducting composites with ultra-fine filaments, fabricated by hydrostatic extrusion without intermediate annealings, possess optimal combination of mechanical and electrical characteristics. __________ Translated from Problemy Prochnosti, No. 5, pp. 93 – 103, September – October, 2005.     

In situ X-ray study of order–disorder phase transitions in Cu–Al–Be melt spun ribbons

The disorder–order phase transitions in Cu–Al–Be shape memory alloys were studied by in-situ X-ray diffraction. Isothermal measurements in an inert gas chamber were made on ribbons of Cu–Al–Be alloys, obtained by melt spinning. A position sensitive detector was used for a fast record of the X-ray signal on a θ–θ geometry diffractometer. Each ribbon was used as the heating element, avoiding the need of a heating sample holder and obtaining a better measurement of the temperature with a thermocouple attached directly to the ribbon. The order transition was followed at different temperatures after a high temperature annealing (700 °C) in the disordered β-phase region. A first order transition was observed from disordered β (A2) to ordered β ₁ (DO₃), without prior β (B2) ordering. No precipitation was detected during this fast measuring procedure.     

Embrittlement and fracture toughness of highly irradiated austenitic steels for vessel internals of WWER type reactors. Part 1. Relation between irradiation swelling and irradiation embrittlement. Experimental results

For the assessment of the effect of irradiation-induced swelling on mechanical properties of an irradiated austenitic steel, investigations have been performed on 08Kh18N10T steel – base metal and weld – exposed to damaging dozes close in magnitude, within two different temperature ranges: (a) 330–340°C, where there occurs almost no swelling, and (b) 400–450°C, where a significant level of swelling (3–13%) is observed. Based on the investigation results, the temperature dependence of short-term mechanical properties is plotted for the irradiated metal. A comparative study of magnetization of the metal irradiated at various temperatures has been carried out. Fractographic examination of the tested specimens has been performed.     

Study of structural transformations and phases formation upon calcination of Zn–Ni–Al hydrotalcite nanosheets

In this paper, we describe a general process for the synthesis of highly crystalline Zn–Ni–Al hydrotalcite-like materials. The structure and thermal decomposition of the prepared samples are studied by XRD, FT–IR, TG–DSC, SEM, TEM and N₂ adsorption/desorption. The morphology of large-sized, porous and hexagonal platelike Zn–Ni–Al hydrotalcite is affected by calcination temperature. BET specific surface area and pore volume are observed to increase with increase of the calcination temperature up to 700°C followed by a further decrease with increasing temperature.     

Thermovoltaic effect in polycrystalline samarium sulfide

A thermovoltaic effect has been observed for the first time in a polycrystalline sample of samarium sulfide (SmS) with artificially created concentration gradient of excess (overstoichiometric) samarium ions, in which an electric voltage of 12–22.5 mV was generated in a temperature interval of 370–485 K. It is shown that the specific voltage generation in SmS due to the thermovoltaic effect can be observed in a temperature range of 100–1800 K.     

A matrix interpretation of the estimate of the extension of uncertainties when constructing a temperature scale

A matrix method of extending the uncertainties when constructing a temperature scale in the 0–660°C range using the calibration of a platinum resistance thermometer at fixed points and interpolating the temperature scale, using it in accordance with the ITS-90, is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 41–45, July, 2006.     

Kinetics of the eutectoid transformation in the Cu–In system

The present study concerns a detailed investigation of the kinetics of the eutectoid transformation in the Cu–In system based on both the isothermal growth rate of the eutectoid colony (monitored by microstructural change) and enthalpy changes during non-isothermal heating (determined by differential scanning calorimetry) of solution-treated and quenched samples. The maximum growth distance of the eutectoid cells and the equilibrium interlamellar spacing have been determined by optical and scanning electron microscopy in the temperature range 600–825 K. The reaction front velocity was observed to increase with the isothermal ageing temperature in the temperature range studied. A detailed analysis of the isothermal growth kinetics through the models available in the literature has yielded an activation energy of 125–127 kJ mol^-1 for the operating diffusion process, which is comparable with that for discontinuous precipitation in Cu–In or for grain boundary tracer diffusion of ¹¹⁵In in Cu, but significantly lower than that for volume diffusion of In in the β Cu–In alloy. A subsequent differential scanning calorimetric study has indicated a similar activation energy of 133 kJ mol^-1 for the concerned eutectoid transformation. It is thus concluded that the eutectoid transformation in the Cu–In system is a boundary-diffusion-controlled process. This revised version was published online in September 2006 with corrections to the Cover Date.     

Microwave annealing for preparation of crystalline hydroxyapatite thin films

A sol was spun on single crystal silicon substrates at a spin-rate of 3000–5000 rpm followed by a low temperature cure to form a stable sol–gel/silicon structure. Good quality crystalline HA films of thickness ∼300–400 nm were obtained by annealing the sol–gel/Si structure in a conventional cavity applicator microwave system with a magnetron power of 1300 W, frequency of 2.45 GHz, and at a low processing temperature of 425 °C for annealing times ranging from 2–60 min. X-ray Diffraction and FTIR analysis confirmed that the crystalline quality of the thin films were comparable or better than those heat-treated under the same processing conditions (temperature and time) in a Rapid Thermal Annealing (RTA) system. The RBS data suggests a composition corresponding to stoichiometric hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, the major inorganic component of bone. The results showed that the HA film thickness decreases with increasing sol spin-rate. The HA films showed good biocompatibility because little monocyte adhesion occurred and hence no inflammatory response was activated in vitro. The potential of microwave annealing for rapid and low temperature processing of good crystalline quality HA thin films derived from sol–gel is demonstrated.     

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.     

Drying shrinkage of cement paste as measured in an environmental scanning electron microscope and comparison with microstructural models

A recently developed image-intensity-matching technique has been used to analyse images of cement paste which were dried in an environmental scanning electron microscope. Shrinkage that occurs during changes in relative humidity is reported, together with some of the influences of water-to-cement ratio, temperature and age. Results from microstructurally based models are compared with experimental results. The best fit of models to experiment is achieved if calcium silicate hydrate (C–S–H) is divided into two types: high density C–S–H, which does not shrink, and low density C–S–H, which does shrink. Approximate values of unrestrained shrinkage of the low density C–S–H are attained as a function of relative humidity. This revised version was published online in November 2006 with corrections to the Cover Date.     

Correlation for the Carbon Dioxide and Water Mixture Based on The Lemmon–Jacobsen Mixture Model and the Peng–Robinson Equation of State

Models representing the thermodynamic behavior of the CO₂–H₂O mixture have been developed. The single-phase model is based upon the thermodynamic property mixture model proposed by Lemmon and Jacobsen. The model represents the single-phase vapor states over the temperature range of 323–1074 K, up to a pressure of 100 MPa over the entire composition range. The experimental data used to develop these formulations include pressure–density–temperature-composition, second virial coefficients, and excess enthalpy. A nonlinear regression algorithm was used to determine the various adjustable parameters of the model. The model can be used to compute density values of the mixture to within ±0.1%. Due to a lack of single-phase liquid data for the mixture, the Peng–Robinson equation of state (PREOS) was used to predict the vapor–liquid equilibrium (VLE) properties of the mixture. Comparisons of values computed from the Peng–Robinson VLE predictions using standard binary interaction parameters to experimental data are presented to verify the accuracy of this calculation. The VLE calculation is shown to be accurate to within ±3 K in temperature over a temperature range of 323–624 K up to 20 MPa. The accuracy from 20 to 100 MPa is ±3 K up to ±30 K in temperature, being worse for higher pressures. Bubble-point mole fractions can be determined within ±0.05 for CO₂.     

Manufacturing of MC Eutectics and Reproducibility of Pt-C Eutectic Fixed Points using a Thermogauge Furnace

National Institute of Metrology (NIM) (China) and National Physical Laboratory (NPL) (UK) have collaborated to construct metal-carbon eutectic alloy fixed points at NPL. A modified NPL Thermogauge furnace was vertically used to construct fixed points of Pd–C, Pt–C, Ru–C, and Ir–C. Breakage of Pd–C and Ru–C cells was traced to changes in furnace temperature gradients resulting from changing from horizontal to vertical operation. Subsequently, it was found that positioning the cell being filled so that the metal melting always starts from the top and freezing from the bottom to solve this problem. The constructed Pt–C cell was then compared to a Pt–C fixed point previously constructed by NIM. The results indicate that the two cells made independently agreed to be better than 40 mK.     

Observation of a negative characteristic temperature for the threshold current of diode lasers for the 2.8 /gmm spectral range

A decrease in the lasing threshold with increasing temperature has been observed in InAs/InAsSbP laser heterostructures for the 2.7–2.9 μm spectral range at cryogenic temperatures (T=32–85 K). At temperatures below 50 K a negative characteristic temperature, T ₀=−70 K, was obtained for the threshold current. Characteristics of the temperature dependence of the threshold current and the laser output power were investigated. Pis#x2019;ma Zh. Tekh. Fiz. 23, 72–79 (November 26, 1997)