Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data

Many solid-state kinetic models have been developed in the past century. Some models were based on mechanistic grounds while others lacked theoretical justification and some were theoretically incorrect. Models currently used in solid-state kinetic studies are classified according to their mechanistic basis as nucleation, geometrical contraction, diffusion, and reaction order. This work summarizes commonly employed models and presents their mathematical development.

Solid-State Kinetic Models: Basics and Mathematical Fundamentals

The determination of activation energy from linear heating rate experiments: a comparison of the accuracy of isoconversion methods

Thermal stability and flame retardancy of polyurethanes

Model-free and model-fitting approaches to kinetic analysis of isothermal and nonisothermal data

Full Paper: The thermal degradations of polystyrene (PS), polyethylene (PE), and poly(propylene) (PP) have been studied in both inert nitrogen and air atmospheres by using thermogravimetry and differential scanning calorimetry. The model-free isoconversional method has been employed to calculate activation energies as a function of the extent of degradation. The obtained dependencies are interpreted in terms of degradation mechanisms. Under nitrogen, the thermal degradation of polymers follows a random scission pathway that has an activation energy L200 kJ N mol ‐1 for PS and 240 and 250 kJ N mol ‐1 for PE and PP, respectively. Lower values (L150 kJ N mol ‐1 ) are observed for the initial stages of the thermal degradation of PE and PS; this suggests that degradation is initiated at weak links. In air, the thermoxidative degradation occurs via a pathway that involves decomposition of polymer peroxide and exhibits an activation energy of 125 kJ N mol ‐1 for PS and 80 and 90 kJ N mol ‐1 , for PE and PP respectively.

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Kinetics of the Thermal and Thermo-Oxidative Degradation of Polystyrene, Polyethylene and Poly(propylene)

▪ Abstract The kinetics of solid state reactions generally cannot be assumed to follow simple rate laws that are applicable to gas-phase reactions. Nevertheless, a widely practiced method for extracting Arrhenius parameters from thermal analysis experiments involves force fitting of experimental data to simple reaction-order kinetic models. This method can produce significant errors in predicted rates outside the experimental range of temperatures, and it is of limited utility for drawing mechanistic conclusions about reactions. In this review, we discuss how an alternative “model-free” approach to kinetic analysis, which is based on the isoconversional method, can overcome some of these limitations.

Kinetics in solids

This review covers both the history and present state of the kinetics of thermally stimulated reactions in solids. The traditional methodology of kinetic analysis, which is based on fitting data to reaction models, dates back to the very first isothermal studies. The model fitting approach suffers from an inability to determine the reaction model uniquely,and this does not allow reliable mechanistic conclusions to be drawn even from isothermal data. In non-isothermal kinetics, the use of the traditional methodology results in highly uncertain values of Arrhenius parameters that cannot be compared meaningfully with isothermal values. An alternative model-free methodology is based on the isoconversional method. The use of this model-free approach in both isothermal and non-isothermal kinetics helps to avoid the problems that originate from the ambiguous evaluation of the reaction model. The model-free methodology allows the dependence of the activation energy on the extent of conversion to be determined. Th...

Isothermal and non-isothermal kinetics of thermally stimulated reactions of solids

Thermogravimetric data for the decomposition of ammonium dinitramide (ADN) have been obtained under isothermal and nonisothermal conditions in order to determine the efficacy of different methods for analyzing the kinetics of solid-state reactions. A widely used model-fitting method gives excellent fits to the experimental data but yields highly uncertain values of the Arrhenius parameters when applied to nonisothermal data because temperature and extent of conversion are not independent variables. Therefore, comparison of model fitting results from isothermal and nonisothermal experiments is practically meaningless. Conversely, model-free isoconversional methods of kinetic analysis yield similar dependencies of the activation energy on the extent of conversion for isothermal and nonisothermal experiments. Analysis of synthetic data generated for a complex kinetic model suggests that, in the general case, the identical dependencies are unlikely to result from experiments obtained under isothermal and noni...

Charles A. Wight

Papers

Model-free and model-fitting approaches to kinetic analysis of isothermal and nonisothermal data

Kinetics of the Thermal and Thermo-Oxidative Degradation of Polystyrene, Polyethylene and Poly(propylene)

Kinetics in solids

Isothermal and non-isothermal kinetics of thermally stimulated reactions of solids

Isothermal and Nonisothermal Reaction Kinetics in Solids: In Search of Ways toward Consensus