Thermal expansion of tungsten in the range 1500–3600 K by a transient interferometric technique

The linear thermal expansion of tungsten has been measured in the temperature range 1500–3600 K by means of a transient (subsecond) interferometric technique. The tungsten selected for these measurements was the standard reference material SRM 737 (a standard for thermal expansion measurements at temperatures up to 1800 K). The basic method involved rapidly heating the specimen from room temperature up to and through the temperature range of interest in less than 1 s by passing an electrical current pulse through it and simultaneously measuring the specimen temperature by means of a high-speed photoelectric pyrometer and the shift in the fringe pattern produced by a Michelson-type interferometer. The linear thermal expansion was determined from the cumulative shift corresponding to each measured temperature. The results for tungsten may be expressed by the relation $$\begin{gathered} (l - l_0 )/l_0 = 1.3896 \times 10^{ - 3} - 8.2797 \times 10^{ - 7} T + 4.0557 \times 10^{ - 9} T^2 \hfill \\ - 1.2164 \times 10^{ - 12} T^3 + 1.7034 \times 10^{ - 16} T^4 \hfill \\ \end{gathered} $$ whereT is in K andl ₀ is the specimen length at 20°C. The maximum error in the reported values of thermal expansion is estimated to be about 1% at 2000 K and approximately 2% at 3600 K.     

Transient interferometric technique for measuring thermal expansion at high temperatures: Thermal expansion of tantalum in the range 1500–3200 K

The design and operational characteristics of an interferometric technique for measuring thermal expansion of metals between room temperature and temperatures in the range 1500 K to their melting points are described. The basic method involves rapidly heating the specimen from room temperature to temperatures above 1500 K in less than 1 s by the passage of an electrical current pulse through it, and simultaneously measuring the specimen expansion by the shift in the fringe pattern produced by a Michelson-type polarized beam interferometer and the specimen temperature by means of a high-speed photoelectric pyrometer. Measurements of linear thermal expansion of tantalum in the temperature range 1500–3200 K are also described. The results are expressed by the relation: $$\begin{gathered} (l - l_0 )/l_0 = 5.141{\text{ x 10}}^{ - {\text{4}}} + 1.445{\text{ x 10}}^{ - {\text{6}}} T + 4.160{\text{ x 10}}^{ - {\text{9}}} T^2 \hfill \\ {\text{ }} - 1.309{\text{ x 10}}^{ - {\text{12}}} T^3 + 1.901{\text{ x 10}}^{ - {\text{16}}} T^4 \hfill \\ \end{gathered}$$ where T is in K and l₀ is the specimen length at 20°C. The maximum error in the reported values of thermal expansion is estimated to be about 1% at 2000 K and not more than 2% at 3000 K.     

Heat capacity and electrical resistivity of POCO AXM-5Q1 graphite in the range 1500–3000 K by a pulse-heating technique

Measurements of the heat capacity and electrical resistivity of POCO AXM-5Q1 graphite in the temperature range 1500–3000 K by a subsecond-duration pulse-heating technique are described. The results for heat capacity may be represented by the relation $$C_{{\text{p }}} = 19.438 + 3.6215 \times {\text{10}}^{{\text{ - 3}}} {\text{ }}T - 4.4426 \times {\text{10}}^{{\text{ - 7}}} {\text{ }}T^2$$ where C _p is in J · mol^?1 · K^?1 and T is in K. The results for electrical resistivity vary with the density (d) of the specimen material and, therefore, are represented by the following relations: for d=1.709, $$\rho = 1084.6 - 1.9940 \times {\text{10}}^{{\text{ - 1}}} {\text{ }}T + 1.6760 \times {\text{10}}^{{\text{ - 4 }}} T^{2{\text{ }}} - 2.0310 \times {\text{10}}^{{\text{ - 8 }}} T^3$$ and for d= 1.744, $$\rho = 943.1 - 1.3836 \times {\text{10}}^{{\text{ - 1}}} {\text{ }}T + 1.3776 \times {\text{10}}^{{\text{ - 4 }}} T^{2{\text{ }}} - 2.0310 \times {\text{10}}^{{\text{ - 8 }}} T^3$$ where ρ is in μΩ · cm, T is in K, and d (at 20°C) is in g · cm ^?3. The maximum uncertainties in the measured properties are estimated to be 3% for heat capacity and 1 % for electrical resistivity.     

Thermal diffusivity of gadolinium in the temperature range of 287–1277 K

New experimental data on the thermal diffusivity of gadolinium in the temperature interval from 287 to 1277 K obtained by the laser flash method with an error of 3–4% are presented. Results are compared with the available literature data. Reference tables on the heat transfer coefficients of gadolinium for scientific and practical use are developed. Critical indices for the thermal diffusivity of gadolinium above the Curie point are determined. The limitations of the laser flash method during measurement in the region of phase transformations are briefly discussed.     

Thermophysical measurements on tungsten-3 (wt %) rhenium alloy in the range 1500–3600 K by a pulse heating technique

Simultaneous measurements of the specific heat capacity, c _p, electrical resistivity, ρ, and hemispherical total emittance, ε, of tungsten-3 (wt%) rhenium alloy in the temperature range 1500–3600 K by a subsecond-duration pulse heating technique are described. The results are expressed by the relations $$\begin{gathered} c_{\text{P}} = 0.30332 - 2.8727 \times 10^{ - 4} {\text{ }}T + 1.9783 \times 10^{ - 7} {\text{ }}T^2 \hfill \\ {\text{ }} - 5.6672 \times 10^{ - 11} {\text{ }}T^3 + 6.5628 \times 10^{ - 15} {\text{ }}T^4 , \hfill \\ \rho = - 24.261 + 8.1924 \times 10^{ - 2} {\text{ }}T - 3.7656 \times 10^{ - 5} {\text{ }}T^2 \hfill \\ {\text{ + 1}}{\text{.1850}} \times {\text{10}}^{ - 8} {\text{ }}T^3 - 1.3229 \times 10^{ - 12} {\text{ }}T^4 , \hfill \\ \varepsilon = 0.1945 + 5.881 \times 10^{ - 5} {\text{ }}T, \hfill \\ \end{gathered} $$ where T is in K, c_p is in J·g^?1·K^?1, and ρ is in μΩ·cm. The melting temperature (solidus temperature) was also measured and was determined to be 3645 K. Uncertainties of the measured properties are estimated to be not more than ±3 % for specific heat capacity, ±1 % for electrical resistivity, ± 5 % for hemispherical total emittance, and ±20 K for the melting temperature.     

Specific heat capacity and electrical resistivity of a carbon-carbon composite in the range 1500–3000 K by a pulse heating method

Measurements are described of specific heat capacity and electrical resistivity of a 2-2-3 T-50 carbon-carbon composite in the temperature range 1500–3000 K by a subsecond duration pulse heating technique. The results are represented by the relations 1 $$C\rho = 1.691 + 2.598{\text{x10}}^{{\text{ - 4}}} T - 2.691{\text{x10}}^{{\text{ - 8}}} T^2 $$ 2 $$\rho = 733.0 + 6.594{\text{x10}}^{{\text{ - 2}}} T$$ where c _p is in J · g^?1 · K^?1, ρ is in ΜΩ · cm, and T is in K. Inaccuracy of specific heat capacity and electrical resistivity measurements is estimated to be not more than ±3%.     

Measurement of thermophysical properties by a pulse-heating method: Niobium in the range 1000–2500 K

Data for the heat capacity, electrical resistivity, hemispherical total emittance, and normal spectral emittance (at 898 nm) of niobium are reported for the temperature range 1000–2500 K. Measurements were based on a subsecond pulseheating technique. The results are discussed and compared with the literature values. Reported uncertainties for the properties are 3% for heat capacity, 1% for electrical resistivity, 5% for hemispherical total emittance, and 4% for normal spectral emittance.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Heat capacity and electrical resistivity of nickel in the range 1300–1700 K measured with a pulse heating technique

Measurements of the heat capacity and electrical resistivity of nickel in the temperature range 1300–1700 K by a subsecond duration pulse heating technique are described. The results are expressed by the relations: $$\begin{gathered} C_p = 21.735 + 9.8200 \times 10^{ - 3} T \hfill \\ \rho = 18.908 + 2.3947 \times 10^{ - 2} T \hfill \\ \end{gathered} $$ whereC _p is in J · mol^?1·K^?1,ρ is inμΩ·cm, andT is in K. Estimated maximum uncertainties in the measured properties are 3% for heat capacity and 1% for electrical resistivity.     

Errors in measuring the directivity of a field by the method of a reference field in the range of 25–400 MHZ

Conclusions The cited data on error components in measuring the field-strength lead to the conclusions that the reference field (provided that the distances are measured with an error of ±2%) can be determined with an error of 6%, at frequencies up to 150 MHz, and of ±7% in the range from 150 to 400 MHz. The error in determining the resulting field-strength is smaller for small angles of elevation, since the beam reflected from the ground has a substantial effect on the value of the field.     

Thermal conductivity and electrical resistivity of pure polycrystalline cobalt in the temperature range 2.5–30 K

Thermal conductivity and electrical resistivity of 99.99% pure Co sample were measured in the temperature range 2.5–30 K. The annealing, procedure of the sample (either above or below Curie temperature), followed by cooling it down to room temperature at a slow cooling rate, caused an unexpected increase in its thermal resistivity and residual electrical resistivity, contrary to the results obtained for most pure metals. Co samples either not thermally treated or annealed consist only of a HI phase as proved by X-ray and electron diffraction analyses. The result, led to the conclusion that changes of grain structure and physical defects appearing in the Co at Curie temperature and at 690 K, when phase transitions take place, should be taken into account. The electron-magnon scattering, is significant in electrical conductivity but the electron-physical defect and impurity scattering plays a dominant role in thermal conductivity. The electron-physical defect and impurity scattering is elastic (validity of the Wiedemann Franz law)) as demonstrated by the value of _{th el} = 1.0, obtained in this work.     

Accurate thermal expansivity measurements in the range 1500–2000 K are needed for minerals

It is shown that the future high-temperature thermodynamic computations for minerals now hinge on the extension of the measurement of the volume thermal expansivity, up to 2000 K. At present many measurements of end at about 1200–1500 K, but the extrapolations to 2000 K are fraught with large errors. A few years ago, the missing thermodynamic parameter at high temperatures was the bulk modulus (or its reciprocal compressibility). Now that measurements of the bulk modulus are being accurately measured at 1800 K, attention is focused on improving measurements of at higher temperatures.Presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A.     

Thermal expansion of beryllium oxide in the temperature interval 20–1550°C

The results of studies of thermal expansion of the sintered beryllium oxide in the temperature interval 20–1550°C are presented. Measurements were performed by a dilatometric method on a DIL-402C set-up manufactured by NETZSCH (Germany), with the accuracy of (1.5–2) × 10^?7 K^?1. Approximation dependences of coefficients of linear thermal expansion on temperature have been obtained and reference tables calculated. The data obtained are compared with data from the available literature.     

Comparison of the cytotoxicity of molybdenum as powder and as alloying element in a niobium–molybdenum alloy

Commercially pure metal niobium (c.p. Nb) as well as niobium–molybdenum (Nb–Mo) alloys were produced following several powder metallurgical routes. In brief, niobium and molybdenum powders were blended and milled in order to form Nb–Mo alloys. The alloy powders and the c.p. Nb were then either pressed and sintered, or cold isostatically pressed followed by hot isostatically pressing. In order to assess the cytotoxicity of the c.p. Nb and c.p. Mo powders, a 72 h minimal essential medium-extraction test was performed according to ISO/EN 10993–5. The cytotoxicity of the c.p. Nb metal and the Nb–Mo alloys was tested in a 72 h direct contact test. Compared to a negative control (UHMWPE), c.p. Nb was non-toxic, but c.p. Mo was moderately toxic. None of the powder metallurgically produced materials were toxic. Neither differences in molybdenum concentration, nor in porosity of the samples, due to different production routes, had any influence on the toxicity of the materials. Rat bone marrow cultures showed that only on c.p. Nb was a mineralized extracellular matrix formed, while on the more porous Nb–Mo alloys, cell growth was observed, but no mineralization. In conclusion, c.p. Mo powder is moderately toxic, however, as an alloying element it is non-toxic. Material porosity seems to influence differentiation of bone tissue in vitro. © 1998 Kluwer Academic Publishers     

Heat capacity of rare-earth stannates in the range 350–1000 K

R₂Sn₂O₇ (R = Pr–Lu) rare-earth stannates with the pyrochlore structure have been synthesized by solid-state reactions, by firing stoichiometric mixtures of SnO₂ and R₂O₃ in air at 1473 K. The high-temperature heat capacity of the rare-earth stannates has been determined by differential scanning calorimetry in the temperature range 350 to 1000 K, and the Raman spectra of polycrystalline Tb₂Sn₂O₇ and Dy₂Sn₂O₇ samples have been measured.     

Investigation of the heat conductivity of niobium in the temperature range 0.05–23 K

We report thermal conductivity measurements on a single-crystal niobium specimen of resistivity ratio 33,000 over the temperature range 0.05–23 K in the superconducting state and above 9.1 K in the normal state. The axis of the niobium rod was [110] oriented. The surface roughness was varied by sandblasting of the sample. The values of the thermal conductivity in the range from the lowest temperatures up to the maximal value covered a range of six orders of magnitude (=2×10^–5 W cm^–1 K^–1 at 50 mK to =22 W cm^–1 K^–1 at 9 K). Above 2 K the results for the untreated and the sandblasted sample are in accord, whereas below 2 K the influence of the sample surface is discernible. The various conduction and scattering mechanisms are discussed.     

Thermal properties of aqueous solutions of polyvinylpyrrolidone in the temperature range 20–80°C

The thermal properties (thermal diffusivity a, thermal conductivity , and volumetric heat capacity C _p) of aqueous solutions of polyvinylpyrrolidone (PVP) were measured in the temperature range 20–80°C. The measurements were carried out using the hot-wire (strip) technique. Three different average molecular weights of PVP were used [M = 10,000 (PVP-10), M = 24,500 (PVP-24.5), and M = 40,000 (PVP-40)], i.e., the average degrees of polymerization are 90, 220, and 360, respectively. The results show that the values of the thermal properties depend on the temperature and the concentration of PVP in the medium. The mechanism of heat transfer was discussed. The role of convection and radiation were taken into consideration.     

Influence of strain rate on the temperature rise of specimens in static tests of a titanium alloy in the 293–4.2 K range

The influence of two strain rates, 1.10^–1 and 2.10^–2 sec^–1, on the temperature rise of specimens of -titanium alloys in static tests in the 290- 4.2 K range is investigated. It is established that at room temperature conditions (290 K) the temperature rise of the specimens is nonuniform over the length and is 14 K, in liquid nitrogen (77 K) it is more than 0.5 K, and in liquid helium (4.2 K) the temperature depends upon the strain rate and reaches 46 K. It is shown that the temperature rise of the specimens in liquid helium in strain at a rate of 2.10^–2 sec^–1 reduces the tensile strength but does not influence the yield strength of the material.Translated from Problemy Prochnosti, No. 12, pp. 70–78, December, 1992.     

Thermodynamic properties of TeO2-ZnO glasses in the range 0–650 K

The heat capacity C _p ⁰ of (TeO₂)_n(ZnO)_{1 ? n} (n = 0.65, 0.70, 0.80) tellurite glasses has been determined by precision adiabatic (6–350 K) and dynamic scanning (320–650 K) calorimetry. The thermodynamic characteristics of their devitrification and glassy state have been determined. The experimental data have been used to calculate the standard thermodynamic functions of samples in the glassy and “supercooled liquid” states (0–650 K): heat capacity C _p ⁰ (T), enthalpy H ⁰(T) ? H ⁰(0), entropy S ⁰(T) ? S ⁰(0), and Gibbs function G ⁰(T) ? H ⁰(0). Multifractal processing of the low-temperature heat capacity data has been used to assess the character of structural heterodynamicity of the tellurite glasses. The heat capacity of the glasses has been analyzed in comparison with that of their constituent oxides. The composition dependences of the glass transition temperature, crystallization onset temperature, and thermodynamic functions at 298.15 and 600 K have been obtained.     

Stability of industrial grade platinum resistance thermometers in the range 13–273 K

This Paper examines the stability of five two-lead industrial grade 100 Ω platinum resistance thermometers used in the temperature range 13–273 K. The static stability was tested by storing the thermometers for three months, and the dynamic stability was tested by cycling the thermometers over five and 50 cycles from room temperature to liquid helium temperature. It has been found that the dynamic instability of four thermometers after 5 thermal cycles is < 0.3 K at 273 K and < 0.15 K at 13 K. Only one thermometer shows dynamic instability of < 0.05 K at both temperatures. The static instability of all five thermometers is much lower than their dynamic instability and may, therefore, be neglected.