Development of a 3-D, multi-nuclear continuous wave NMR imaging system

The development of a 3-D, multi-nuclear continuous wave NMR imaging (CW-NMRI) system is described and its imaging capability is demonstrated on a range of materials exhibiting extremely short T(2) relaxation values. A variety of radiofrequency resonators were constructed and incorporated into a new gradient and field offset coil assembly, while the overall system design was modified to minimise microphonic noise which was present in an earlier prototype system. The chemically combined (27)Al in a high temperature refractory cement was imaged, and the CW-NMRI system was found to be sensitive to small differences in (27)Al content in these samples. The penetration of (23)Na in salt water into samples of ordinary Portland cement (OPC) was investigated, with enhanced uptake observed for samples with larger pore size distributions. The solid (13)C component in a carbonated cement sample was also imaged, as were the (7)Li nuclei in a sample of powdered Li(2)CO(3). A spatial resolution of 1mm was measured in an image of a rigid polymeric material exhibiting a principal T( *)(2) value of 16.3 micros. Finally, a high-resolution 3-D image of this rigid polymer is presented.     

Predictive thermodynamics for condensed phases

Thermodynamic information is central to assessment of the stability and reactivity of materials. However, because of both the demanding nature of experimental thermodynamics and the virtually unlimited number of conceivable compounds, experimental data is often unavailable or, for hypothetical materials, necessarily impossible to obtain. We describe simple procedures for thermodynamic prediction for condensed phases, both ionic and organic covalent, principally via formula unit volumes (or density); our volume-based approach (VBT) provides a new thermodynamic tool for such assessment. These methods, being independent of detailed knowledge of crystal structures, are applicable to liquids and amorphous materials as well as to crystalline solids. Examples of their use are provided.     

Optimal catalyst concentration profile for bifunctional catalysts

The optimal catalyst profile for a consecutive reaction scheme (where the first reaction is promoted by a catalyst of one type, and the second by a catalyst of a different type) is determined by use of the Pontryagin maximum principle. Solutions are obtained for nonlinear reaction rate expressions. The optimal concentration profile can be obtained by relatively simple numerical computation and does not necessitate the solving of a two-point boundary-value problem.Professor C. Crowe, McMaster University, suggested several inprovements to the original draft of this paper. This paper is published with the approval of the Director of the National Institute for Metallurgy.     

Applying thermodynamics to digestion/gasification processes: the Attainable Region approach

The research shows theoretical calculations on the thermodynamics of digestion/gasification processes where glucose is used as a surrogate for biomass. The change in Enthalpy (?H) and Gibbs Free Energy (?G) is used to obtain the Attainable Region (AR) that shows the overall thermodynamic limits for digestion/gasification from 1 mol of glucose. Gibbs Free Energy and Enthalpy (G–H) plots were calculated for the temperature range 25–1500 °C. The results show the effect of temperature on the AR for the processes when water is in both liquid and gas states using 25 °C, 1 bar as the reference state. The AR results show that the production of CO, H₂, CH₄ and CO₂ are feasible at all temperatures studied. The minimum Gibbs Free Energy becomes more negative from ?418.68 kJ mol^?1 at 25 °C to ?3024.34 kJ mol^?1 at 1500 °C while the process shifts from exothermic (?141.90 kJ mol^?1) to endothermic (1161.80 kJ mol^?1) for the respective temperatures. Methane and carbon dioxide are favoured products (minimum Gibbs Free Energy) for temperatures up to about 600 °C, and this therefore includes Anaerobic Digestion. The process is exothermic below 500 °C, and thus Anaerobic Digestion requires heat removal. As the temperature continues to increase, hydrogen production becomes more favourable than methane production. The production of gas is endothermic above 500 °C, and it needs a supply of heat that could be done, either by combustion or by electricity (plasma gasification). The calculations show that glucose conversion at temperatures around 700 °C favours the production of carbon dioxide and hydrogen at minimum G. Generally, the results show that the gas from high-temperature gasification (>~800 °C) typically carries the energy mainly in syngas components CO and H₂, whereas at low-temperature gasification (<500 °C) the energy is carried in CH₄. The overall analysis for the temperature range (25–1500 °C) also suggests a close relationship between biogas production/digestion and gasification as biogas production can be referred to as a form of low-temperature gasification.     

Enthalpy of formation of ye’elimite and ternesite

Journal of Thermal Analysis and Calorimetry - Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components...     

An analytically solvable model of confined electrons in a magnetic field and its relation to Landau diamagnetism

Here we present analytic results for the Slater sum and the magnetic moment for arbitrary magnetic field strengths for an assembly of harmonically confined, but initially free, electrons. The relevance of the results to the generalized Landau diamagnetism of such confined electrons is emphasized.