Laser-flash Calorimetry Research Articles

Thermophysical properties of Inconel alloy 740 modified with titanium and aluminium

Superalloys, which are known for their high temperature resistance, are widely used in aerospace applications, gas turbines, turbine blades for jet engines and automotive applications. The Inconel alloy 740 is a nickel-based, age-hardened superalloy, with good heat resistance and thermal stability. The thermophysical properties of the Inconel alloy 740 of varied material compositions were assessed by measurement of the thermal diffusivity, specific heat capacity, thermal conductivity, and coefficient of thermal expansion (CTE). Inconel alloy 740 was modified with titanium and aluminium. A typical IN740 alloy, ‘IN1’, had Ti (2.8 wt.%) and Al (1.4 wt.%) added, ‘IN2’ was modified using Ti (3.6 wt.%) and ‘IN3’ was modified with Al (1.8 wt.%). The thermal diffusivity and the specific heat capacity were measured using laser flash and differential scanning calorimetry, respectively. The thermal conductivity was calculated according to the results of the thermal diffusivity and specific heat capacity in the temperature range from room temperature to 800°C. The CTE was evaluated by push-rod dilatometer method. In this study, we present the thermophysical properties of the Inconel alloy 740, of which the base material was modified with titanium and aluminium.

A New Method for the Determination of the Specific Heat Capacity Using Laser-Flash Calorimetry Down to 77K

A new method for evaluation of the specific heat capacity in the temperature regime between 77K and 330K using laser-flash calorimetry is presented. Usually, laser-flash calorimetry is accomplished by performing an additional laser-flash measurement on a reference specimen with a known specific heat capacity and by comparing the maximum rear-side temperatures rises. In this study, the calibration is achieved by comparison of the rear-side temperature rise to specific-heat-capacity data determined by other methods in an adjacent temperature regime. Subsequently, the thus yielded proportional factor is used for the evaluation of the specific heat capacity from laser-flash measurements at temperatures where no specific-heat-capacity data are available. The reliability of this method is shown by performing measurements on a material with known specific heat capacity, aluminum oxide. Furthermore, the specific heat capacity and thermal conductivity of borosilicate crown glass (BK7) was determined experimentally.

Thermophysical Properties of Ceramic Substrates with Modified Surfaces

Laser induced changes of thermophysical properties using a laser supported modification process have been studied. Metal–ceramic composites have been produced by a laser dispersing process. Two types of substrates have been included, namely, pure Al2O3 and Al2O3 reinforced with 10 mass% ZrO2. As a modifying material during the laser process, hard metal powders like TiN and WC have been applied in order to produce a metal–ceramic composite with a metal concentration between 30 and 50%. Standard measurement techniques such as the laser-flash method and differential scanning calorimetry (DSC) have been used to measure the thermal diffusivity and the heat capacity of the ceramics before and after the laser processing. These properties have been evaluated within a temperature range from room temperature to 1400°C. The experimental results show that the effective thermal conductivity will be enhanced within the laser modified region. The increase of this heat transport property due to particle dispersion into the ceramic matrix depends on the thermal conductivity of the second-phase material.

Infrared optical properties of semitransparent pyrolytic boron nitride (pBN)

Because of the semitransparency of pBN in the infrared spectral region, the heat flux within this material does not only depend on its solid thermal conductivity, but also on its radiative properties. In order to characterise the heat transfer in pBN samples, the thermal and infrared optical properties were determined. From the measured spectral reflectance and transmittance of the samples, the radiative heat-transfer coefficient was derived. In addition, the thermal conductivity was determined via laser-flash and differential scanning calorimetry measurements. It was found that for temperatures above 600 K the radiative transport influenced the total heat-transfer coefficient significantly.

A Laser Flash Apparatus for Thermal Diffusivity and Specific Heat Capacity Measurements

We have developed a laser flash apparatus for simultaneous measurements of thermal diffusivity and specific heat capacity of solid materials by introducing recent technical progress: uniform heating by a homogenized laser beam using an optical fiber with a mode mixer, measuring transient temperature of a specimen with a calibrated radiation thermometer, analyzing a transient temperature curve with a curve fitting method, to achieve differential laser flash calorimetry. Thermal diffusivity, specific heat capacity and thermal conductivity of glassy carbon and molybdenum were measured in the temperature range from 300 to 1100 K.

The heat capacity of tantalum from 80 to 1000 K

The heat capacity of metallic tantalum has been measured in the temperature range 80–1000 K by laser-flash calorimetry. The results are compared with available low- and high-temperature heat capacities, and the thermodynamic values are given.

Heat capacities of uranium-zirconium alloys from 300 to 1100 K

The heat capacities of four metallic uranium zirconium alloys (Zr at%: 14, 35, 72 and 91) were determined by laser-flash calorimetry from 300 to 1100 K. The heat capacities of uranium-rich alloys showed the normal temperature dependence up to 890 K, while those of zirconium-rich showed a small hump at the temperature region from 650 to 870 K. Above 870 K, heat-capacity anomalies were observed for each alloy sample at respective temperatures corresponding to the phase transitions expected in the uranium-zirconium phase diagram. The heat capacities of U(α)Zr(β) solid solution up to 1100 K were also determined.

Heat capacity of aluminum from 80 to 880 K

Abstract The heat capacity of 99.999% pure metallic aluminum has been measured by laser-flash calorimetry in the temperature range 80–880 K. The results are compared with available low- and high-temperature heat capacities, as well as with those of recent independent critical evaluations.

Thermal conductivity of mineral measured by laser flash calorimetry

Thermal conductivity of mineral measured by laser flash calorimetry

Laser-flash calorimetry V. Effect of oxygen contamination on the heat capacity of vanadium from 80 to 850 K

The heat capacity of vanadium with 0.33 mass per cent of O and with 1.11 mass per cent of O in solid solution has been measured by laser-flash calorimetry through the temperature region 80 to 850 K. Comparison of the results with earlier values for vanadium at and above ambient temperature and for vanadium and for a terminal solution alloy at very low temperatures shows that below about 450 K oxygen in solution depresses the heat capacity of vanadium by amounts which increase with increasing oxygen content. Above about 450 K, the heat capacities of vanadium and of the terminal solution alloys are comparable. This heat-capacity behavior results in differences between the entropies of vanadium and of terminal solution alloys which increase up to about 450 K and then remain relatively constant. These entropy differences are sufficiently large that, when multiplied by temperature to determine a Gibbs-energy contribution, the product is such as to indicate that very minor amounts of oxygen in vanadium may appreciably modify its alloying behavior.

Heat capacity of gold from 80 to 1000 K

The heat capacity of gold has been measured by laserflash calorimetry in the temperature range 80–1000 K. The results are compared with available low- and high-temperature heat capacities, and revised thermodynamic values of gold are given.

Techniques and Materials for Laser Flash Calorimetry

Techniques and Materials for Laser Flash Calorimetry

Thermodynamic properties by levitation calorimetry ? V. High-temperature heat content of liquid gallium

The heat content (enthalpy) of liquid gallium relative to the supercooled liquid state at 298.15 K has been measured by levitation calorimetry over the temperature range 1412–1630 K. Thermal energy increments were determined using an aluminum block calorimeter of conventional design. The sharp decrease of C p with increasing temperature observed just above the melting point does not persist up to the high temperatures of the present work. When combined with recent laser-flash calorimetry results from the literature, the present work indicates that C p is 26.46 ± 0.71 J · g-atom−1 · K−1 over the temperature range 587–1630 K.

Laser-flash calorimetry IV. Heat capacity of gallium from 80 to 600 K in two solid phases and liquid phase

The heat capacity of gallium has been measured by laser-flash calorimetry at temperatures ranging from 80 to 302 K for Ga-I (α-Ga), 210 to 254 K for β-Ga, and 250 to 600 K for liquid gallium. The results are as follows: C p (Ga-I, 298.15 K) = 26.33 J·K −1·mol −1; C p ( β-Ga, 250 K) = 27.67 J·K −1·mol −1; C p (Ga, 1,302.93 K) = 28.24 J·K −1·mol −1. The peculiarity of gallium has been discussed in terms of anharmonic heat capacity of solid phases and of the configurational entropy of the liquid phase.

Laser-flash calorimetry III. Heat capacity of vanadium from 80 to 1000 K

The heat capacity of vanadium has been measured by laser-flash calorimetry in the temperature region from 80 to 1000 K. The results are compared with available low- and high-temperature heat capacities, and revised thermodynamic values of vanadium are given. No heat-capacity anomaly has been found in the pure vanadium sample over the temperature range investigated, while a small heat-capacity discontinuity, less than 1.2 J · K −1 · mol −1, has been observed at 220 to 230 K on the same sample but electropolished before measurement. This anomaly disappeared after annealing at 1000 K in vacuo for 1 h and is attributable to the introduction of a small amount of hydrogen during electropolishing.

Heat capacity of metallic uranium and thorium from 80 to 1000 k

The heat capacities of metallic uranium and thorium from 80 to 1000 K have been determined by laser-flash calorimetry. The results on uranium agree very well with those in the literature over the temperature range investigated. The results on thorium are several percent lower than the heat-capacity values hitherto reported, while the enthalpy data at high temperatures in the literature are in good agreement with the present results. Shomate's analysis showed that the present results are the most consistent through the temperature range from 80 to 1000 K. On this, a revised table of thermodynamic functions of thorium from 80 to 1000 K is presented. The excess heat capacity on thorium has been found to be not appreciable up to 1000 K, in contrast with the large excess heat capacity above 300 K for uranium.

Laser-flash calorimetry II. Heat capacity of platinum from 80 to 1000 K and its revised thermodynamic functions

The heat capacity of platinum has been measured from 80 to 1000 K by laser-flash calorimetry. The results are compared with available heat capacities and relative enthalpies. Shomate analysis is used to derive a consistent set of values and it is shown that a slight amendment is needed from 150 to 500 K in the standard heat capacities hitherto used. Revised thermodynamic values for platinum from 0 to 1000 K are recommended on the basis of the present results.

Calorimetric study on the electronic structure in UP-US system

The heat capacity of UP 1− x S x ( x = 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0) has been measured from 80 to 670 K by laser-flash calorimetry. All samples exhibit an anomaly corresponding to the magnetic transition. The magnetic transition temperatures determined are in good agreement with literature values. UP 0.4S 0.6 shows an additional small peak at 86 K below T c . It has been derived that the US-rich ferromagnetically ordered state should be divided into two phases in terms of the direction of the moments. Above 250 K, the heat capacities of all samples increase monotonically with temperature and are well represented in the form of C p = 6 R + AT − BT −2. The conduction band structure has been derived from the high-temperature linear term and has been compared with that in literature. It has been suggested that the magnetically ordering behavior such as the direction of the moments would be closely correlated with the band structure.

Heat capacity measurements of nuclear materials by laser flash method

An improved method of laser flash calorimetry for the precise measurements of haat capacity of nuclear materials is presented. The main points of the improvements are (1) the use of an ‘absorption disk’ and (2) the use of a digital micro-voltmeter and line printer systems for the measurement of sample temperature. Experimental results obtained on a standard sample of alumina at temperatures from 80 to 700 K by this method have a precision of ± 0.5%, which proves the feasibility of this improved method for both low- and high-temperature heat capacity determination of nuclear materials. The results of heat capacity determination by this method on graphites and UP are also presented. Une amélioration de la méthode calorimétrique par flash de laser est présentée en vue de mesurer de manière précise la capacité calorifique des matériaux nucléaires. Les principaux points d'amélioration sont les suivants: (1) l'emploi d'un ‘disque d'absorption’ et (2) l'emploi d'un microvoltmètre digital et un système d'imprimante pour la mesure de la température des échantillons. Les résultat expérimentaux obtenus sur un échantillon étalon d'alumine entre 80 et 700 K par cette méthode atteignent une précision de ± 0,5%, ce qui démontre les possibilités de cette méthode améliorée pour effectuer des déterminations de la capacité calorifique des matériaux nucléaires à la fois aux températures faibles et élevées. Les résultats de détermination de la capacité calorifique par cette méthode sont présentés dans le cas des graphites et de UP. Eine verbesserte Methode de Laserblitz-Kalorimetrie zur genauen Messung der Wärmekapazität von Kernbrennstoffen wird mitgeteilt. Die Verbesserungen betreffen hauptsächlich die Verwendung einer Absorptionsscheibe sowie eines digitalen Mikrovoltmeters und eines Druckersystems zur Bestimmung der Probentemperatur. Experimentelle Ergebnisse an einer Standardprobe aus Al 2 O 3 führen nach dieser Methode zwischen 80 und 700 K zu einer Genauigkeit von ± 0,5%, aus der folgt, dass diese verbesserte Methode zur Bestimmung der Wärmekapazität von Kernbrennstoffen bei niedrigen und hohen Temperaturen geeignet ist. Die Ergebnisse der nach dieser Methode gewonnen Wärmekapazität von Graphit und UP werden angegeben.