Friction on ice is important for many different fields such as winter sports and vehicle traction. In vehicle handling, maximising the friction coefficient between tyres and the ice surface is key to safety. The friction coefficient between tyre rubber and ice has been observed to be as high as unity at low temperatures and as little as 0.05 close to the ice melting temperature. The observed low friction is due to thin water films generated through frictional heating. Little is known about the formation and behaviour of this fluid film and its thickness has been difficult to measure. Previous attempts included techniques such as capacitance, conductivity and fluorescence spectroscopy, however results have been inconsistent. The primary aim of this study was to develop a measurement technique for this lubricating layer, establishing its thickness and the conditions under which its presence results in low friction. This was done by designing a micro-scale linear tribometer (microtribometer) to measure the friction coefficient (μ) on ice under a microscope. Clear ice, and ice with fluorescent particles of various sizes were created. The two ice types were then joined and tested on. During a friction test on the microtribometer, the particles displaced in the direction of sliding due to melt water presence. Images of the ice surface were taken before and after a friction measurement was made, and the amount of particle movement was assessed. The size and displacement of particles were correlated to the range of melt water thickness for a given sliding condition. This study is the first direct measurement method for the melt water layer on ice. Frictional heating is generated through the physical contact of rubber and ice asperities. By conducting friction measurements with rubbers of varying shear modulus (G*) and surface roughness (Ra) on both the microtribometer and on our large–scale tribometer, FRIMA, analysis of the contact can be made over a range of length scales. Further insight into the interfacial effects was provided by surface roughness measurements of both ice and rubber before and ice after microtribometer tests and in FRIMA. Finally, the use of differential interference contrast in reflected light microscopy with ice friction measurements provided visual evidence of the melt water presence. It was found that the melt water thickness based on particle displacement was between 0.1 to 2μm, for a velocity of 4.3 ⇥ 10−4 ms−1 and 0.5MPa nominal load, between –6°C to 0°C. A decreasing film thickness was found with decreasing temperature and the friction coefficient increased with decreasing temperature. At higher temperatures, the differences between the rubbers on both FRIMA and the microtribometer were found to be negligible because of the lubricating layer. Increasing the rubber surface roughness was found to increase at high and decrease friction significantly at low temperatures. These phenomena can be explained by the decreasing amount of solid-solid contact. A simple analytical approach to interpret the results suggests that the rubber compresses significantly and the surface roughness is smoothened upon contact with ice. Furthermore, simple hydrodynamic shear calculations show that pure liquid shear is insufficient to account for the measured low μ values close to melting temperatures. The combined effect of the increasing melt water presence reducing the real contact area and the significant deformation of the rubber asperities failing to compensate for this reduced contact area can account for the results. It is anticipated that these results provide direction for finding ways to improve solid-solid contact between rubber and ice, as there is some viscoelastic dissipation even at conditions close to the melting temperature. Some topics for example are: improving the thermal conductivity of tyre compounds or further investigating the surface roughness of rubber and ice separately and with the thin liquid film in between.

This master thesis is covering the modeling of the melting process in a tank filled with AdBlue. Due to AdBlue freezing at temperatures below -11 degree there is a need to add heat to be able to secure dosing in all situations. A rig for simulating freezing conditions is created with the possibility to store AdBlue in temperatures down to -40 degree. Temperatures are measured in and around the tank containing AdBlue and in the equipment used for adding heat. Two models are created from physical relations to estimate the mass of AdBlue melted, a static temperature model and a dynamic temperature model. The static model shows good results when calibrated at this specific setup and is very easy to use. The dynamic temperature model is more advanced but describes the real physical system better without external calibration.

Snow melt is an important component of Western US water resources, accounting for about 50-80% of the annual runoff. Prediction of runoff from snowmelt in heterogeneous watersheds requires the quantification of physical processes accounting for the effects of forest canopy on snow accumulation, melt and sublimation. The forest canopy intercepts snowfall that resulting in smaller snow accumulations in forest area than in open area. The forest canopy also modifies the energy exchange between snow surface and the atmosphere, and alters the sublimation and melting of sub-canopy snow relative to open area. This dissertation has examined ways to improve snowmelt modeling capability to better account for canopy effects and has presented enhancements to an energy balance model that include i) an improved representation of the transmission of radiation through the canopy, ii) an improved representation of the atmospheric transport of heat and water vapor between the snow on the ground, in the canopy and the atmosphere above, and iii) an improved representation of the processes of canopy snow interception and unloading. These enhancements were evaluated against 4 years of field data (2006-2010) collected at the TW Daniels Experimental Forest (TWDEF) located 30 miles N-E of Logan. Observations included continuous automated climate and snow depth measurements supported by periodic field measurements of snow water equivalent and temperature in four different vegetation classes (grass, shrubs, coniferous forest, deciduous forest). The enhanced canopy components were included into the Utah Energy Balance Snowmelt model and provide improved capability to predict the surface water input and runoff from snowmelt in heterogeneous watersheds using a parsimonious approach that can be used with practically available information.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

The crystallization kinetics and the melting behavior of a random copolyester with equal amounts of ethylene- and trimethylene- terephthalate units were studied by using a modulated differential scanning calorimeter in both conventional mode (DSC) and modulated mode (TMDSC). Polarizing light microscope (PLM) was used to study the spherulite growth rates and spherulite patterns. Isothermal crystallization was performed at temperatures (TC) between 115 and 142¢J. The Avrami exponents, n1, were found to increase from 3.00 to 3.22 with an increasing TC. At the highest TC, it should be a sporadic nucleation with spherical growth, i.e. n1 = 4. The value of n1 less than 4 and the slow rate of crystallization indicate that both primary and secondary crystallization occurs in parallel rather than in series. Triple- and double- melting peaks were observed for the melting behavior of DSC at 10¢J/min and of TMDSC at 2¢J/min. The results of WAXD, DSC and TMDSC indicate the coexistence of two melting mechanisms, i.e., dual morphologies and the recrystallization process. The Hoffman-Weeks plot gave an equilibrium melting temperature of 176.6¢J from the reversing curves of TMDSC. In this study, the regime II¡÷III transition temperature can be estimated from the inverse of the half-time of crystallization as overall growth rate and the growth rate. Meanwhile, a clear change in morphology from negative regular to banded spherulites was also observed around 132¢J by using PLM. The heat of fusion of polymer is customarily evaluated through the melting point depression measurements with the thermodynamic melting points. Application of the Flory equation to the PET/PTT random copolyesters diluted with di-n-butyl phthalate gave the values of the heat of fusion to be 4.48, 3.43 and 3.07 kcal/mole, respectively, for the random copolyesters containing 28, 38 and 50 mole % of ethylene terephthalate unit. The corresponded values of the interaction energy of mixing at infinite dilution were 3.90, 2.85 and 2.75 cal/cc.

Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters (PETSAs) with various compositions were used to investigate the structure-property relationship. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The chemical compositions and the sequence distribution of co-monomers in the copolyesters were determined by NMR spectroscope. The distributions of ES unit and TS unit were found to be random. Their thermal properties were characterized using differential scanning calorimeter (DSC). The thermal stability of polyesters was analyzed by thermogravimeter (TGA) and polarized light microscope (PLM) under nitrogen. The results of TGA show that all of the samples have similar thermal stability (Tstart : 246¡Ó3 ¢XC), but the thermal degradation temperature of PES and PETSA(95/05) are 213 and 200 ¢XC, respectively, estimated from the isothermal growth rates after pre-melting at various temperatures. The degradation temperature analyzed by PLM is more sensitive than that obtained from TGA. The incorporation of 5 mol% of TS units into PES significantly reduces the thermal stability of PES. In addition, wide-angle X-ray diffractograms (WAXD) were obtained for polyesters which were crystallized isothermally at a temperature 5~10 ¢XC below their melting temperatures. The results of WAXD and DSC indicate that the incorporation of TS units into PES significantly inhibit the crystallization behavior of PES. In the second part of this study, PES and PETSA(95/05) were studied in detail. The crystallization kinetics and the melting behavior were investigated by using DSC in both conventional mode and modulated mode (TMDSC). The reversing, total, and non-reversing heat flow curves were analyzed. The Hoffman-Weeks plots gave an equilibrium melting temperature of 112.7 and 108.3 ¢XC for PES and PETSA(95/05), XI respectively. Only one crystal form was found from WAXD for specimens crystallized isothermally at various temperatures. Based on the WAXD patterns, DSC and TMDSC thermograms, multiple endothermic melting peaks can be explained by two mechanisms, melting-recrystallization-remelting and dual morphologies. PLM was used to study the growth rates and morphology of the spherulites. The growth rates measured in isothermal conditions were very well comparable with those measured by the non- isothermal procedure. In addition, the temperature range of growth rates detected by the non- isothermal procedure is wider than that by the isothermal method, which is time consuming. The regime II®III transition of PES was estimated at ~ 71 ¢XC which is very close to the literature values, and that of PETSA(95/05) was found at ~ 65 ¢XC.

Simultaneous differential scanning calorimetry (DSC), small-angle (SAXS) and wide-angle X-ray scattering (WAXS) measurements were adopted for more precise determination of the equilibrium melting temperatures (Tm*) of a and b phases in bulk-crystallized syndiotactic polystyrene. On the basis of Kratky-Porod approximation, a new method for determining crystalline lamellar thickness from SAXS profiles obtained at high temperatures where there are only limited number of discrete crystalline lamellae dispersed in the melt matrix was developed. This method is shown to be reliable as it gave comparable results obtained from the conventional 1D correlation function method for SAXS profiles obtained at lower temperatures where lamellae are closely stacked. Results of the subsequent Gibbs-Thomson analysis indicated that the trigonal a phase is the entropically favored high temperature phase with Tm* = 355 oC whereas the b phase is enthalpically favored at lower temperatures, with Tm* = 314 oC. Compared to previous held contention in the temperature-dependent phase stability of these two phases, the current phase stability assignment is more consistent with both the density and the symmetry of the corresponding crystal structures. It also explains various observations reported previously on the competition between the two polymorphs during crystallization and during melting.

The subject is to study two-dimension phase transition. The nano-magnetic particles dispersed in magnetic fluid can aggregate to form magnetic columns under external perpendicular magnetic field. At some appropriate condition, these magnetic columns are able to form two-dimension lattices. It is a novel mesoscopic system for studying two-dimensional melting transition. By controlling external magnetic field, we explore phenomena of phase transition and defect dynamics. This article can be divided to three parts. In the first part, we study the phase transition with two-dimension lattice forming with magnetic fluid, then we classify the crystal, hexatic and liquid phases in the melting process with translational correlation function and bond-orientational correlation function. In the second part, we analyze the defect dynamics within the lattice with Burgers Vector. In the third part of this article, the external DC magnetic field is replaced with the AC magnetic field, we find that the two-dimension lattices are also formed in low frequency region. The relationship between the two-dimension lattice forming and the AC frequency are studied.

Crystallization kinetics and melting behavior of PEEK were studied by differential scanning calriometry (DSC) and modulated differential scanning calriometry (MDSC). The isothermal crystallization was performed in DSC between 290 and 320¢XC. The Avrami constants (n1, n2) and the level off time were determined from the Avrami analysis. The n1 values varied from 1.50 to 2.98, and the n2 values were between 0.52 and 1.37. The minimum induction time required for the occurrence of double melting peaks was obtained by increasing the isothermal crystallization time in a interval per minute. It was found that the minimum time was always longer than the level off time, which cannot be used as the delimitation for the occurrence of single or double melting peaks. To study the melting behavior and the mechanisms of double melting peaks, the samples after melting at 400¢XC for 15 min were crystallized isothermally between 200 and 320¢XC for 10 or 60 min, and then they were heated to 380¢XC at 10 or 2 ¢XC/min, respectively. From the MDSC results of crystallization temperatures between 280 and 310¢XC, it is found that two different morphologies and melting-recrystallization phenomenon coexisted. As the isothermal crystallization temperature increased from 280 to 310¢XC, the contribution of melting-recrystallization to the upper melting peak gradually decreased. In the case of 320¢XC, the mechanisms of double melting peaks were dominated by two different morphologies only. Quasi-isotropic composites in the stacking sequence of [0/¡Ó45/90]2s were fabricated by a modified diaphragm forming apparatus. Three different processing conditions were used to prepare AS4/PEEK composites with the same crystallinity but different transcrystallinity. The morphology before and after the long-term tensile-tensile tests was observed by means of scanning electron microscope. The transcrystallinity has no significant effect on the short-term tensile test. This was due to the fibers in the 0¢X plies of [0/¡Ó45/90]2S laminates dominated the failure at high stress for the short-term tensile test. However, as the transcrystallinity increased, the failure cycles for the long-term tensile test became longer. This expressed that the delay of damage initiation in the 90¢X and ¡Ó45¢X plies of [0/¡Ó45/90]2s led to a longer failure cycles in the long-term tensile tests.