The Department of Energy funded a project to determine if the specific heat of thermal energy storage materials could be improved by adding nanoparticles. The standard thermal energy storage materials are molten salts. The chosen molten salt was a sodium nitrate and potassium nitrate eutectic, commercially called Hitec Solar Salt. Two nanoparticle types were chosen, alumina and silica. The nanoparticle composite materials were fabricated by mixing the components in an aqueous solution, mixing that solution for a set amount of time using a sonic mixer, then removing the water from the aqueous solution, leaving the composite molten salt behind as a fine white powder. The thermal properties of the composite and plain material were measured using two techniques: American Society for Testing and Materials (ASTM) 1269E and Modulating Differential Scanning Calorimetry (MDSC). These two techniques measured the specific heat and the heat of fusion of the plain and composite materials. The results of all the ASTM and MDSC measurements suggest that the addition of the nanoparticles using the given manufacturing technique increased the specific heat of the molten salt by approximately 20 percent, with both measurement techniques showing approximately the same level of increase. The silica and the alumina improved the specific heat by nearly the same amount over the base material. The heat of fusion did not seem to be significantly altered compared to the observed heat of fusion value of the unmodified material. It was also observed that the nitrate and silica composite material's specific heat decreased if the material was raised to a temperature above 400C. The specific heat was observed to decrease over time, even when the temperature was well below 400C. It is unknown why this occurred. The nitrate plus alumina composite and the plain nitrate were stable to a temperature of 450C for the test duration.

Organic matter is ubiquitous in the environment and exists in many different forms. Reactions involving organic matter are diverse and many have significant economic and environmental implications. In this research, calorimetric techniques were used to study organic- inorganic reactions in two different systems. The primary objectives were to elucidate potential mechanism(s) by which: (i) natural organic matter (NOM) influences strength development in lime-stabilized soils, and; (ii) plant-derived biochars reacts with cations in aqueous environments. Natural organic matter influenced strength development in lime-stabilized soils through the direct inhibition of the formation of pozzolanic reaction products. The degree of inhibition was dependent mainly on the type of pozzolanic reaction product, and the amount and source of organic matter. The formation of the pozzolanic reaction product, calcium silicate hydrate II (CSH2) was less affected by NOM, than was the formation of CSH1. For a given pozzolanic product, the inhibition increased with NOM content. The effect of organic matter source followed the order fulvic acid> humic acid&gt; lignite. Formation of CSH pozzolanic reaction products decreased by 50-100%, 20-80% and 20-40% in the presence of ?2% fulvic acid, humic acid and lignite, respectively. Cation interactions with plant-derived biochars were complex and depended both on the nature of the cation and biochar surface properties. Reactions involving the alkali cation, K+; occurred via electrostatic ion exchange, on deprotonated functional groups located on the biochar surface and; were exothermic with molar heats of reaction (?Hads) between -3 and -8 kJ mol-1. In contrast, reactions involving the transition metal cation, Cd2+ were endothermic with delta Hads between +10 and +30 kJ mol-1. Reaction mechanism(s) for Cd2+ varied from ion exchange/surface complexation in biochars formed at <350 oC, to an ion exchange/surface complexation/diffusion-controlled mechanism in biochars formed at >/=350 oC. For a given cation, differences in sorption characteristics were attributable to temperature-dependent or plant species dependent variations in the properties of the biochars.

In recent years, the application of thermal analysis to study the combustion and pyrolysis behavior of fossil fuels has gained a wide acceptance because of its significance for industry and economy. In this thesis, the thermal and kinetic analysis of different origin crude oil samples are performed by two well-known thermal analysis techniques: Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG/DTG). The investigation of combustion and pyrolysis behaviors, kinetic analysis of oil samples and the determination of heating rate effect are the main objectives of this study. Six different crude oils from the Southeastern region of Turkey are analyzed throughout the study. All experiments are performed at different heating rates (5, 10 and 15&ordm / C/min) and air is used for combustion and nitrogen for pyrolysis experiments. In combustion experiments, TGA and DSC techniques indicate that the combustion process of crude oils studied is composed of two main reaction regions. These are low-temperature (LTO) and high-temperature oxidation (HTO) regions. In LTO, huge mass loss occurs (from 69 to 87 %) due to high amount of free moisture and volatile hydrocarbons contained in oil samples. Combustion reactions continue up to 900 K. On DSC curves, two exothermic regions of oxidation regimes are detected. Comparing TG/DTG and DSC curves, it can be understood that the mass loss under combustion is accompanied by exothermic peaks because of the oxidative degradation of crude oil components. As in combustion, two distinct reaction regions are revealed under pyrolysis for all samples. The first region indicates distillation and the second one is due to thermal cracking reactions occur at high temperatures and completed up to 840 K. As expected, lighter crude oils have relatively higher amounts of mass loss in distillation region as compared to heavier ones. Besides, residue amount and burn-out temperatures are higher for heavier oils with higher asphaltene content in cracking region. DSC curves for both reactions show endothermic effects. In combustion and pyrolysis experiments, it is noticed that higher heating rates are resulted in higher reaction regions. Distinguishing peaks of samples shift to higher temperatures with an increase in heating rate. Heat of reaction amount under DSC curves is related to asphaltene content and &amp / #730 / API gravity of crude oils. It is deduced that, when &amp / #730 / API gravity of crude oils decreases, the heat value of this reaction increases. The kinetic parameters are evaluated by different kinetic models and mean activation energies (Em) of samples are obtained. At the end, a correlation is established between Em and &amp / #730 / API gravity of oil samples. It is concluded that heavier oils have higher activation energy and Arrhenius constant values for each reaction region. Besides, it is proved that the activation energy is mostly insensitive to the heating rate.

In this thesis there were two main purposes, the first one being to investigate effects of zinc borate (ZB) on the flammability behavior of ABS when used with and without a traditional brominated flame retardant (BFR) / antimony trioxide (AO) system. The second purpose was to investigate contribution of nanoclays (NC) to the flame retardancy performance of the same traditional BFR compound with various combinations of AO and ZB again in ABS matrix. For these purposes, materials were melt compounded by using a laboratory scale twin-screw extruder, while specimens were produced by injection or compression molding. Flame retardancy of the specimens were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) measurements and UL-94 vertical burning tests. Other characterization techniques required in this thesis were / X-ray diffraction analysis, scanning and transmission electron microscopy, thermogravimetric analysis and tensile tests. Studies for the first purpose indicated that almost all flame retardancy parameters were preserved when antimony trioxide were replaced with zinc borate as much as in the ratio of 1:3. Residue analyses revealed that predominant flame retardancy mechanism of traditional system was gas phase action, while zinc borate contributes especially in the condensed phase action by forming thicker and stronger char layer. Investigations for the second purpose basically concluded that use of nanoclays improved all flame retardancy parameters significantly. Residue analyses pointed out that nanoclays especially contribute to the formation of stronger and carbonaceoussilicate char acting as a barrier to heat and flammable gases and retarding volatilization via tortuous pathway. As an additional third purpose in this thesis, usability of three boron compounds (zinc borate ZB, boric acid BA, boron oxide BO) with two traditional flame retardants (organic phosphinate OP and melamine cyanurate MC) in neat PET and recycled PET were also examined leading to some promising results in MLC parameters.

In this thesis, four different crude oil samples and their saturate, aromatic and resin fractions were analyzed by two different thermoanalytical methods, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The experiments were performed at three different heating rates (5, 10 and 15 &deg / C/min) under air atmosphere. Same gas flow rate and same pressure were applied to all samples. The aim is to determine the kinetic analysis and combustion behavior of crude oils and their fractions and also determining the effect of heating rate on all samples. For all samples two main reaction regions were observed in thermogravimetry (TG), differential thermogravimetry (DTG) and DSC curves due to the oxidative degradation of crude oil components. It was deduced that the free moisture, volatile hydrocarbons were evaporated from the crude oils, light hydrocarbons were burned and fuel was formed in the first reaction region. The second reaction region was the main combustion region where the fuel was burned. From the TGA curves, it was detected that the heavier fraction, resins, lost considerable amounts of their initial mass, approximately 35%, while saturates lost only approximately 3% of their initial mass in the second reaction region. DSC curves of the samples were also examined and observed that as the sample got heavier, the heat of the reaction increased. Saturates, lightest part of the crude oil fractions, gave minimum heat of reaction. As the heating rate increased, shift of peak temperatures to high values and higher reaction regions were observed. The kinetic analysis of crude oils and their fractions were also performed using different kinetic methods. Activation energies (E), mean activation energies (Emean) and Arrhenius constants were found for crude oils and fractions. It was deduced that the resins gave the highest activation energy and Arrhenius constant for both reaction regions. Moreover, it was encountered that heating rate has no effect on activation energies.

In this thesis, a new software, THERA-Kinetics was developed for the evaluation of kinetic parameters using non-isothermal data. Different computational methods, available in the software, were applied to a set of experimental and simulated data distributed in the ICTAC (International Confederation for Thermal Analysis and Calorimetry) Kinetics Project. The reliability of the software was verified by comparing the kinetic results, which were in good agreement, with those obtained by the participants of the ICTAC Kinetics Project. It was also within the scope of this study to examine the combustion characteristics and kinetics of three same origin coal samples. A series of thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements were carried out in non-isothermal conditions at heating rates of 5, 10 and 15 K/min. Reaction regions, peak and burn-out temperatures, weight loss percentages and heat of reactions of the samples were determined for each heating rate from TG and DSC curves. A variety of computational methods, available in the software developed, were applied to experimental data for the evaluation of the kinetic parameters of the coal samples. It was observed that there was no general trend in the activation energy values from the point of heating rate.

In this thesis, there were four purposes. The first one was to investigate effects of nanoclays (NC) on the flammability behavior of polystyrene (PS). The second purpose was to investigate contribution of nanoclays to the flame retardancy performance of conventional phosphorus based flame retardant / triphenyl phosphate (TPP) and its synergist melamine cyanurate (MCA). For the third purpose contribution of nanoclays to the flame retardancy performance of another conventional halogenated flame retardant / brominated epoxy polymer (BE) and its synergist antimony trioxide (AO) was investigated. As the fourth purpose, effects of another nanoadditive / carbon nanotubes (CNTs) on the flammability behavior of PS with and without BE-AO flame retardant system was investigated. Materials were prepared via &ldquo / solution mixing&rdquo / method, while test specimens were shaped by compression and injection molding. Flammability behaviors were investigated by Mass Loss Cone Calorimeter (MLC), Limiting Oxygen Index (LOI) and UL-94 Vertical Burning tests. Other characterization techniques required in this thesis were / X-ray diffraction analyses, scanning and transmission electron microscopy, thermogravimetric analyses and tensile tests. It was revealed that use of nanoclays improved flame retardancy of PS significantly, mainly with &ldquo / condensed phase&rdquo / mechanism via formation of strong char barrier layers inhibiting mass and heat transfer. When nanoclays were used together with conventional flame retardant systems TPP-MCA and BE-AO, flame retardancy parameters improved further, this time due to the &ldquo / synergistic action&rdquo / of &ldquo / condensed phase mechanism&rdquo / of nanoclays and &ldquo / gas phase mechanism&rdquo / of the conventional systems. Use of carbon nanotubes also resulted in improvements in the flame retardancy of PS. However, &ldquo / condensed phase mechanism&rdquo / of CNTs were not as effective as the NCs, which might be due to the lower performance of 1D geometry (CNTs) compared to higher efficiency of 2D geometry (NC) in barrier formation. As an additional purpose, effects of mixing methods in the production of PS-Nanoclay composites were also investigated. It was seen that compared to &ldquo / solution mixing&rdquo / use of &ldquo / in-situ polymerization&rdquo / resulted in poorer flame retardancy parameters that might basically be due to residual monomers or oligomers left during polymerization.

Portland cement hydration is an exothermic process. The heat evolved during the hydration process is especially important in mass concrete, and hot and cold weather concreting. Heat of hydration is affected by several factors like chemical composition of cement, fineness of cement and ambient temperature. The major aim of this thesis is to investigate the effect of cement composition and fineness, amount and composition of the fine portion (&lt / 45 &micro / m) of natural pozzolan-incorporated cement on hydration heat. For this purpose, a portland cement and pozzolan-incorporated blended cements containing different amounts of natural pozzolan (trass) were used. The heat of hydration was measured using isothermal calorimetry. The values of heat of hydration for mixtures with different finenesses containing different amounts of added pozzolan were determined. The results obtained were used to find a correlation between the fineness, composition of cement and heat of hydration. According to this study, pozzolan incorporation in small amounts accelerates hydration. A similar effect was obtained for higher pozzolan amounts. Finer cements react faster and result in higher amounts of early heat evolved compared to coarser cements. In addition, it was found that the sum of the heat of hydration values of fine and coarse portion of cements was less than the total heat of hydration of blended cements. Moreover, a satisfactory correlation could not be established between results of isothermal calorimetry, and adiabatic calorimetry, setting time, and strength.

During the last few years the scientific interest in chalcogenides glasses has been provoked on account of their properties and new application possibilities. These materials exhibit electrical and optical properties, which make them useful for several potential applications. Specifically the threshold and memory switching behavior and the infrared transmission of many of these glasses make the materials to be well suitable for use in memory devices and in fiber optics. Multicomponent glasses have been found to be more useful for many of these applications since the properties could be tailored for the specific uses. On account of this there has been great deal of interest in recent years in understanding the composition dependent variations of physical properties in these glasses. Models based on network topology and chemical ordering have been proposed to explain the composition dependence of physical properties. The Chemically Ordered Covalent Network (COCN) model is one of the best efforts put forth in this subject. This model predicts distinctive physical properties of these glasses for compositions at which there is a maximum number of heteropolar bonds. A physical model based on changes in network topology with composition has been proposed recently. This model predicts the rigidity to percolate in the network at the mean coordination number <r> = 2.40. This critical value of <r> at which the rigidity percolates is called the mechanical threshold or the rigidity percolation threshold. One more argument based on medium range interactions, existing in these glassy networks, suggests that the mechanical threshold should occur at <r> = 2.67. A general lack of consensus in the existing experimental reports on the mechanical threshold in some chalcogenides glasses prevents one from identifying the correct threshold value of <r>. A systematic study of the composition dependence of glasses with a large glass-forming region is necessary to resolve this controversy. The correct threshold value of <r> and the reason for the departure from this value in the other cases is the first step towards verifying the applicability of this model to chalcogenide glasses. Glasses belonging to IV — V — VI groups are natural candidates for this study because of their large glass forming region. It also seems possible to isolate the chemical threshold from interfering with the mechanical threshold in some of these glasses. In device applications of any semiconductor the optical and the electrical band gaps need to be varied and this is commonly done by doping. The large density of valence alteration pairs and intrinsic disorder of amorphous semiconductors counter-balances the effects of external additives. As a result, it is hard to electrically dope these materials. Non-equilibrium experimental techniques have been used to some extent, but one of the limitations is that they are confined to the thin film state. The finding that p to n type conduction sign changes can be induced by Bi and Pb in bulk Ge-M (M= S, Se and Te) glasses has therefore created special interest. This thesis deals with Ge-Se glass matrix doped with Te, Bi and Pb. The optical, thermal and electrical properties have been studied. The present thesis work is arranged in several chapters. The basic introduction of chalcogenide glasses is given in chapter one. This includes an introduction to chalcogenide glasses followed by a brief discussion on the important structural models, the possible defects in chalcogenide glasses and the electrical, optical and thermal properties of chalcogenide glasses. The second chapter discusses the experimental techniques used in the present investigations. The basic principles and theory behind the experiments, the experimental setup and the experimental procedure leading to the determination of the physical properties are given here. These include information about Differential Scanning Calorimetry (DSC), Photo acoustic (PA) spectroscopy and Photoluminescence studies. In the third chapter the experimental investigations on Ge-Se-Te glasses are presented. The chapter starts with the preparation and characterization of these glasses. It then gives an account of the earlier studies on Ge-Se-Te glasses that are relevant to the present work. The results of the DSC and PA studies are discussed in the following two sections. In the systems with Gex Se80-x Te20 and Gex Se75.x Te25, glasses with less than 20 at. % of Ge do not show any crystallization peak due to Se rich content. But Te and Ge-rich glasses show strong crystallization tendency. The composition dependence of Tg of this glassy system gives an evidence for the occurrence of the topological threshold or mechanical threshold at <r> = 2.40 and chemical threshold at <r> = 2.67. These can be explained on the basis of COCN model. The optical band gap and thermal diffusivity studies also show anomalous behavior at <r> = 2.40 and <r> = 2.67. The experimental results on Ge-Se-Te glasses are summarized in the last section of this chapter. The investigations on Bi doped Ge-Se and Ge-Se-Te glasses are given in the fourth chapter. The chapter starts with a brief introduction of preparation, characterization and a short review of earlier work. In PA studies the anomalous behavior is observed in thermal diffusivity and thermal diffusion length plot at 8-9 at. % of Bi doping of the Ge-Se and Ge-Se-Te glasses where the conduction changes from p to n type. These results are explained on the basis of percolation model and the formation of Bi2Se3 microcrystalline phase. Finally these results are summarized at the end of the chapter. The fifth chapter is devoted to the investigations on Pb doped Ge-Se glasses. It is arranged in five sections; preparation and characterization, earlier work, Photo acoustic and Photoluminescence studies. In PA studies the composition dependence of thermal diffusivity show anomalous behavior at x =F 9 at % of Pb in Pbx Ge42-x Sesg glasses and y = 21 at. % of Ge in Pb2o Gey Seso-y glasses where the conduction changes from p to n type. After that it reaches the maximum. After the conduction sign changes the conductivity increases with addition of respective Pb and Ge concentration in both series of glasses, which is reflected in thermal diffusivity value also. The results have been explained on the basis of COCN model. From PL studies, the PL intensity is high in un-doped Ge42 Scss glasses. With the addition of Pb into Ge-Se system the PL intensity goes down drastically up to 9 at. % of Pb, beyond 9 at. % the PL intensity is approximately the same up to 15 at. %. In the last section the results are summarized. Chapter six summarizes the essential features of the work reported in the thesis. These conclusions are drawn from the present and the earlier reported studies on Ge-Se-Te glasses, Bi doped Ge-Se and Ge-Se-Te glasses and Pb doped Ge-Se glasses. Finally based on the present experimental results, some future work has been suggested which could throw some light on a better understanding of/? to n transition and defects state of these glasses. It is worth extending the microscopic phase separation studies in these glasses. Highly sensitive experimental techniques are needed in this regard. Also some simulation work like Monte-Carlo simulation and Molecular dynamics simulation needs to be undertaken for understanding the microscopic phase separation and the role of defects in carrier type reversal in these glassy materials. All the references cited in the thesis are collected and listed at the end of the thesis.

<p>In the present work, the thermodynamic activites of ironoxide, denoted as "FeO" in the slag systems Al₂O₃-"FeO", CaO-"FeO", "FeO"-SiO₂, Al₂O₃-"FeO"-SiO₂, CaO-"FeO"-SiO₂and "FeO"-MgO-SiO₂were investigated by employing the gasequilibration technique at steelmaking temperatures. Thestrategy was to expose the molten slag mixtures kept inplatinum crucibles for an oxygen potential, determined by aCO/CO₂-ratio. A part of the iron reduced from the "FeO"in the slag phase was dissolved into the Pt crucible.</p><p>In order to obtain the activites of "FeO", chemical analysisof the quenched slag samples together with thermodynamicinformation of the binary metallic system Fe-Pt is required.Careful experimental work was carried out by employing asolid-state galvanic cell technique as well as calorimetricmeasurements in the temperature ranges of 1073-1273 K and300-1988 K respectively. The outcome of these experiments wasincorporated along with previous studies into a CALPHAD-type ofthermodynamic assessment performed with the Thermo-Calc™software. The proposed equilibrium diagram enabledextrapolation to higher temperatures.</p><p>The experimentally obtained activites of "FeO" in thepresent work, along with earlier investigations were assessedwith the KTH slag model, THERMOSLAG©. New binaryparameters were evolved and incorporated in THERMOSLAG©.The present model calculations are compared with othercommercially available software such as F*A*C*T™andThermo-Calc™. The validity of the modified model wasinvestigated by measurements carried out in case of Al₂O₃-"FeO"-SiO₂, CaO-"FeO"-SiO₂and "FeO"-MgO-SiO₂ternary slags. The potential of the model tocompute the activities in the case of multicomponent slags wasdemonstrated.</p><p>A correlation between the activity of a metallic oxide in aternary slag system and the sulphide capacity of the slag wasinvestigated by using the solubility of sulphur in the binarysystems CaO-SiO₂and Al₂O₃-CaO along with the sulphide capacity of the Al₂O₃-CaO-SiO₂system. The estimated values of the activitieswere found to be in good agreement with the measured values.This correlation also gives the possibility to elucidate theapplicability of Henry's law to the activity of a metallicsulphide and to determine the order in the affinity of a cationto sulphur between two metallic oxides in a slag.</p><p>Model calculations were performed with THERMOSLAG^©, by using plant data from the ladle refiningprocess at OVAKO Steel, Hofors, Sweden. It was found thatoxygen estimations in the metal from the "FeO" analyses ofslags, obtained by conventional sampling and analysis methodwere less reliable. Reliable estimation of the oxygen levelsutilising the sulphur partition between the slag and the metalwere carried out using THERMOSLAG© software.</p><p><b>Keywords:</b>Thermodynamics, Activity, Galvanic cell,Calorimetry, Gas equilibration technique, Iron-platinum alloys,FeO, Slags, Modelling, Ladle</p>