Determination of Accurate Temperature and Enthalpy Measurements using Differential Scanning Calorimetry

This thesis shows that the equilibrium transition temperatures of materials can be accurately determined using two developed methodologies designed to be used with differential scanning calorimeters. These methods are the extrapolation to zero heating rate and a stepwise isothermal method. The use of these methods allows for the instrument, which is typically scanning in nature to produce accurate temperature values under near equilibrium conditions. By employing the DSC methodologies for accurate temperature measurements it has been possible to determine a range of temperatures of transition and fusions under near equilibrium conditions for inorganic potassium salts (nitrate, perchlorate, and dinitramide), and rubidium salts (nitrate, and dinitramide) all of which have transitions of pyrotechnic interest. In cases where decomposition occurs at slower heating rates, the modification of the extrapolation to zero heating method to incorporate the use of faster heating rates above 10°C min-1 has enabled accurate temperatures of transition to be determined. In addition, this thesis also explores the use of materials with solid-solid transitions susceptible to thermal history such as potassium nitrate and re-evaluates the suitability for use in DSC calibration. The close proximity in temperature of the LGC Limited DSC standards indium and diphenylacetic acid, has enabled a direct assessment to be made of any resulting from the use of a metal or an organic substance in the calibration of DSC equipment. These measurements clearly established that indium may be used as a calibrant when making accurate equilibrium temperature and enthalpy measurements on organic materials in the same temperature range. Accurate enthalpy measurements have also been made on the above inorganic nitrates and perchlorates and measurements on the transitions of rubidium nitrate have established that equivalent values are given by heat flux and power compensated instruments. Enthalpy measurements on organic DSC calibration standards in the range 42-147 °C using a power compensated instrument demonstrated that there was no significant error in using indium as a single point calibrant for measurements on the fusion of organic materials at lower temperatures

Thermal Studies on Rubidium Dinitramide

The present study has been carried out to investigate conflicting reports in the literature on the nature of the thermal decomposition of the energetic oxidant rubidium dinitramide in the liquid state. The techniques employed included DSC, simultaneous TG-DTA, simultaneous TG-mass spectrometry and thermomicroscopy. The measurements were supplemented by quantitative chemical analysis of the reaction products. The results showed that, following fusion at 106 °C, the overall decomposition proceeded in a single exothermic reaction stage forming a mixture of rubidium nitrate and rubidium nitrite in the molar ratio 1.2 : 1

Infestation of maize by Prostephanus truncatus initiated by maleproduced pheromone

Delta traps baited with maize cobs, which were infested each with one male Prostephanus truncatus (Horn) (Col.: Bostrichidae), were distributed in southern Benin and collected after one, two, three and four weeks. The numbers of P. truncatus caught during the different trapping periods were not significantly different. Sixty‐four percent of the trapped P. truncatus were females. Females attracted during the one‐week trapping period produced a mean of 6.9 progeny during the seven days. The sex ratio of the progeny was 1:1. Trap catches with the infested cobs were on average 13 times lower than catches with 2 mg of the artificial pheromone. Estimation of P. truncatus densities in a maize store at the beginning of the storage period (based on laboratory data) revealed that small initial numbers of P. truncatus, possibly attracted by a single male, sufficed to initiate high infestation rates later in the storage seaso

Determination of the temperature and enthalpy of the solid-solid phase transition of caesium nitrate by differential scanning calorimetry

The equilibrium temperature of the solid–solid phase transition of high purity caesium nitrate has been measured accurately by stepwise heating and by the extrapolation to zero heating rate method. A mean value of 154.3 ± 0.1 °C was obtained using two different heat flux DSC instruments. A value of 3.44 ± 0.04 kJ mol−1 was determined for the enthalpy of transition