[No abstract submitted] / Science, Faculty of / Chemistry, Department of / Graduate

[No abstract submitted] / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A fluidless adiabatic calorimeter was constructed and was used to measure the specific heats of manganese-aluminum-carbon and manganese-zinc-carbon alloys from -150° to 150°C. In an adiabatic calorimeter, the temperature of a shield surrounding the calorimeter vessel is kept at approximately the same temperature as that of the vessel, so that the thermal leakage between the two is reduced to a negligible quantity. Thus the ordinary rating period, in which the thermal leakage modulus is calculated, can be eliminated. Since leakage modulus variations are reduced by the adiabatic method, it can be used for large temperature rises, resulting in fast and accurate measurements. The aneroid (fluidless) adiabatic calorimeter eliminates stirring and evaporation errors, and makes possible measurements at extreme temperatures. The calorimeter consisted of a cylindrical silver-plated copper vessel surrounded by an electrically heated adiabatic shield and an evacuated outer case. A platinum resistance thermometer-heater was used to supply heat to the calorimeter vessel and to measure the vessel temperature. The heat input and the thermometer resistance were measured by using a potentiometer in conjunction with standard resistances. The thermometer was calibrated by measuring its resistance at -183, -40, 0, and 100°C. The calorimeter was calibrated from -150 to 150°C. The accuracy of the calorimeter was approximately 0.5%, the main error arising from the method of measuring the temperature of the calorimeter vessel. The specific heat curves of the single phase magnetic alloys Mn₃AIC and Mn₃ZnC were measured. A second order specific heat anomaly was found, as expected, for the ferromagnetic alloy Mn₃AlC at its Curie point, -10°C. Although the anomaly was close to the theoretical shape, dropping to zero over only a 10°C range at the Curie point, its maximum height was less than saturation magnetization measurements would indicate. The alloy Mn₃ZnC showed second order specific heat anomalies at -35°C, and at 65°C. This double specific heat anomaly indicates, in agreement with neutron diffraction results, a complex magnetic behaviour for the alloy. Although the high temperature Curie point anomaly did not have a sharp peak, the low temperature anomaly's shape approached that of the theoretical Weiss curve. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

No description available.

No description available.

No description available.

The specific heat of a material is simply the measure of the amount of energy required to raise the temperature of a unit mass of the material by one degree. The specific heat of a material depends on the structure, pressure, and temperature of the material. Hence, measurement of specific heat can indicate structural changes and transitions in the material.Previous work at the State University of New York at Buffalo, shored anomalies in the specific heats of Glassy Carbon samples which had been exposed to neutron irradiation. Neutron irradiation of the carbon introduced defects in the material and the specific heat was dependent on the time of sample irradiation. The specific heat plotted as a function of temperature showed peaks at temperatures below 2.0°K. This indicates some kind of transition in the material. Also the specific heat values, which were measured up to 4.5°K, were much lower than the specific heat of the original nonirradiated material. Measurements indicated that the two kinds of samples had the same specific heat at room temperature. This kind of change in the specific heat of carbon has not been explained.The purpose of this project was to investigate the specific heats of these samples above 4.50K to determine where and how the anomalies in the specific heat disappeared at higher temperatures. The specific heats were measured by cooling the sample with liquid helium. This enabled the sample to obtain temperatures of 2.5°K and up. The specific heat was measured by electrically heating the thermally isolated sample and measuring the change in its temperature with a germanium resistance thermometer.

Thesis advisor: Michael Graf / Senior thesis on muon spin relaxation study of LiHoXY1-XF4 and semi-adiabatic specific heat experiment on LiTb0.40Y0.60F4 / Thesis (BS) — Boston College, 2010. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Physics Honors Program. / Discipline: Physics.

The objective of this research was to measure the effect of thermal cycling on the nanoparticle distribution and specific heat of a nanocomposite material consisting of a eutectic of lithium carbonate and potassium carbonate and 1% by mass alumina nanoparticles. The material was subjected to thermal cycling in a stainless steel tube using a temperature controlled furnace. After thermal cycling, the stainless steel tube was sectioned into three equal parts – top, middle and bottom. Composite material samples were taken from the central region and near the wall region of each section. The specific heat of this material in the temperature range of 290°C-397°C was measured using the Modulated Differential Scanning Calorimeter (MDSC) method. The concentration of alumina nanoparticles in this material was measured using neutron activation analysis. The average specific heat of the uncycled material was found to be 1.37 J/g°C.The average specific heat of the thermally cycled material was between 1.7-2.1 J/g°C. It was found that the concentration of the nanoparticle varied along the height of the sample tube. The nanoparticles tended to settle towards the bottom of the tube with thermal cycling. There was also migration of nanoparticles towards the wall of the sample tube with thermal cycling. Despite these gross movements of nanoparticles, there was no significant change in the specific heat of the nanocomposite due to thermal cycling.

Inaug.-diss.--Marburg, 1912. / Lebenslauf.