Heat removal technologies are among the most critical needs for three-dimensional (3D) stacking of high-performance microprocessors. This research reports a 3D integration platform that can support the heat removal requirements for 3D integrated circuits that contain high-performance microprocessors in the 3D stack. This work shows the use of wafer-level batch fabrication to develop advanced electrical and fluidic three-dimensional interconnect networks in a 3D stack. Fabrication results are shown for the integration of microchannels and electrical through-silicon vias (TSVs). A compact physical model is developed to determine the design trade-offs for microchannel heat sink and electrical TSV integration. An experimental thermal measurement test-bed for evaluating a 3D inter-layer liquid cooling platform is developed. Experimental thermal testing results for an air-cooled chip and a liquid-cooled chip are compared. Microchannel heat sink cooling shows a significant junction temperature and heat sink thermal resistance reduction compared to air-cooling. The on-chip integrated microchannel heat sink, which has a thermal resistance of 0.229 °C/W, enables cooling of >100W/cm² of each high-power density chip, while maintaining an average junction temperature of less than 50°C. Cooling liquid is circulated through the 3D stack (two layers) at flow rates of up to 100 ml/min. The ability to assemble chips with integrated electrical and fluidic I/Os and seal fluidic interconnections at each strata interface is demonstrated using three assembly and fluidic sealing techniques. Assembly results show the stacking of up to four chips that contain integrated electrical and fluidic I/O interconnects, with an electrical I/O density of ~1600/cm².

This thesis is geared towards using hydrogel nanoparticles in various biotechnological applications. The polymer that was used in making these nanoparticles was poly(N-isopropylacrylamide), which is a thermoresponsive polymer. These particles were used in making fast responsive polymer films, which can be used in optics. It was observed that the rate of deswelling increased as the concentration of the nanoparticles in the film was increased. These particles were also used in making photoresponsive materials. In this case a photoresponsive dye (malachite green) was conjugated to these nanoparticles and in presence of light of appropriate wavelength the particles undergo a phase transition. A core/shell construct was synthesized where the core was composed of degradable cross-links and the shell of composed of non-degradable cross-links. The degradable cross-linker had vicinal diols, which can be cleaved by sodium periodate. Hence after degrading the core, hollow particles were obtained. Zwitterionic particles were made by incorporating a cationic and anionic comonomer. These microgels go from a positively charged state to zwitterionic to negatively charged state on increasing the pH. One of the important potential applications for these microgels is drug delivery. Microgels were used for targeting cancer cells. Folic acid was used as the targeting ligand. The microgels were conjugated with folic acid and were able to target cells that overexpress folate receptors. In one other application core/shell microgels were made which exhibit pore-size dependent permeation of proteins.

Compact heat exchangers such as porous foam coldplates have great potential as a high heat flux cooling solution for electronics due to their large surface area to volume ratio and tortuous coolant path. The focus of this work was the development of unit cell modeling techniques for predicting the performance of coldplates with porous foam in the coolant path. Multiple computational fluid dynamics (CFD) models which predict porous foam coldplate pressure drop and heat transfer performance were constructed and compared to gain insight into how to best translate the foam microstructure into unit cell model geometry. Unit cell modeling in this study was realized by applying periodic boundary conditions to the coolant entrance and exit faces of a representative unit cell. A parametric study was also undertaken which evaluated dissimilar geometry translation recommendations from the literature. The use of an effective thermal conductivity for a representative orthogonal lattice of rectangular ligaments was compared to a porosity-matching technique of a similar lattice. Model accuracy was evaluated using experimental test data collected from a porous copper foam coldplate using deionized water as coolant. The compact heat exchanger testing facility which was designed and constructed for this investigation was shown to be capable of performing tests with coolant flow rates up to 300 mL/min and heat fluxes up to 290 W/cm2. The greatest technical challenge of the testing facility design proved to be the method of applying the heat flux across a 1 cm2 contact area. Based on the computational modeling results and experimental test data, porous foam modeling recommendations and porous foam coldplate design suggestions were generated.

It is well known that microprocessor performance can be improved by lowering the junction temperature. Two stage cascaded vapor compression refrigeration (VCR) is a mature, inexpensive, and reliable cooling technology that can offer chip temperatures down to ?? C. Recent studies have shown that for a power limited computer chip, there is a non-linear scaling effect that offers a 4.3X performance enhancement at ?? C. The heat transfer performance of a compact evaporator is often the bottleneck in sub-ambient heat removal. For this reason, the design of a deep sub-ambient compact evaporator is critical to the cooling system performance and has not been addressed in the literature. Four compact evaporator designs were investigated as feasible designs - a baseline case with no enhancement structures, micro channels, inline pin fin arrays, and alternating pin fin arrays. A parametric experimental investigation of four compact evaporator designs has been performed aiming at enhancing heat transfer. Each evaporator consists of oxygen free copper and has a footprint of 20 mm x 36 mm, with a total thickness of 3.1 mm. The micro channel evaporator contains 13 channels that are 400 um wide by 1.2 mm deep, and the pin fin evaporators contain approximately 80 pin fins that are 400 um wide by 1.2 mm tall with a pitch of 800 um. Two phase convective boiling of R508b refrigerant was investigated in each evaporator at flow rates of 50 - 70 g/min and saturation temperatures of ??to ??C. Pressure drop and local heat transfer measurements are reported and used to explain the performance of the various evaporator geometries. The results are compared to predictions from popular macro- and micro-channel heat transfer and pressure drop correlations. The challenges of implementing a two stage cascade VCR systems for microprocessor refrigeration are also discussed.

LOW TEMPERATURE SYNTHESIS AND CHARACTERIZATION OF SOME LOW POSITIVE AND NEGATIVE THERMAL EXPANSION MATERIALS Kathleen Madara White 151 pages Directed by Dr. Angus P. Wilkinson Low temperature non-hydrolytic sol-gel synthesis was used to explore the possibility of lowering the crystallization temperatures of some known AIVMV2O7 compounds. Crystallization temperatures for ZrP2O7 and ZrP2O7 were unaffected by the use of non-hydrolytic sol-gel methods; however, successful synthesis of these compounds broadens the range of materials that can be produced using this method and suggests the possibility of synthesizing solid solutions (or composites) including ZrP2O7 or ZrV2O7. This research presents for the first time the direct synthesis of ZrP2O7 from separate zirconium and phosphorus starting materials using mild autoclave methods. Characterization of some AIVMV2O7 compounds, using lab and high resolution synchrotron powder XRD, led to the assignment of a new symmetry for CeP2O7 and to the suggestion that the reported structure for PbP2O7 was inadequate. Studies using in situ high temperature lab and synchrotron powder XRD for PbP2O7 and CeP2O7 provided the opportunity to report their thermal properties for the first time, and to compare their behavior to that of some other AIVMV2O7. High pressure diffraction measurements on CeP2O7 provided data for the estimation of bulk moduli and suggested two possible pressure-induced phase transitions. A broad range of MIIIMVP4O14 compounds were prepared using low temperature hydrolytic sol-gel synthesis. Thermal studies revealed nearly linear trends in CTEs and lattice constants with respect to the sizes of MIIIMV cations. Some lower ionic radii compounds had CTEs comparable to that of ZrP2O7 at low temperature, suggesting a similar superstructure. Three compounds were found to exhibit temperature-induced phase transitions.

Mixed valence manganites with the perovskite structure R1-xAxMnO3 (where R = La, Nd, Pr and A = Ba, Ca, Sr, Pb) have been a popular subject of contemporary research because of their interesting physical properties such as competing magnetic orders, metal-insulator transitions and colossal magnetoresistance. A complex interplay between structure, electronic and magnetic properties results in rich phase diagrams involving various metallic, insulating and magnetic phases. A review of the literature related to rare-earth managnites clearly reveals that the systems with Pb as a divalent dopant are relatively less explored. This may be due to the volatile nature of lead based compounds which are used as precursors for preparing these systems. This has motivated us to take up research on Pb doped rare earth manganites. This thesis is divided into eight chapters. The first introductory chapter gives a brief review of the work on manganites which have already been reported in the literature following which the motivation for carying out the present investigation is given. The second chapter deals with technical details of various instruments used in the present reasearch work. The third chapter is related to growth of single crystals, their preliminary characterization, magnetization and resistivity studies. Single crystals of Pr1-xPbxMnO3 are grown by flux technique for different compositions. Crystals are characterized by energy dispersive x-ray analysis (EDAX) and inductively coupled plasma atomic emission spectroscopy (ICPAES) for compositional analysis. Magnetization and resistivity studies are carried out on Pr1-xPbxMnO3 for three compositions viz. x = 0.2, 0.23 and 0.3. The magnetization vs. temperature plots show that all the three compositions undergo a transition from paramagnetic to ferromagnetic state. The magnetization in the low temperature ferromagnetic region obeys Bloch`s law. The susceptibility in the paramagnetic region is fitted to Curie Weiss law. Deviation of susceptibilty from Curie Weiss law, a feature observed in all the three crystals has been attributed to formation of ferromagnetic clusters at ~ 250 K. The cluster formation has its implications on all other properties in the temperature range from TC to 250 K where TC is the magnetic transition temperature. Resistivity measurements are carried out on the same three compositions. The x = 0.2 and 0.23 compositions undergo a transition from paramagnetic insulating to ferromagnetic insulating phases. The x = 0.3 composition shows a metal – insulator transition at nearly 35 K above TC. Chapter 4 describes the critical behaviour of Pr1-xPbxMnO3 for two compositions, viz. x = 0.23 and 0.3. For critical studies, magnetization vs. field measurements are carried out in the temperature range TC ± 10 K. Using modified Arrott plots and Kouvel-Fisher method the critical exponents and precise value of TC are obtained. The x = 0.23 composition shows results which indicate a conventional second order phase transition shown by a 3D Heisenberg ferromagnet. It also obeys the universal scaling behaviour. However, the x = 0.3 composition shows deviation from this behaviour. Hence to probe further into the nature of magnetic transition of this compound the effective critical exponents are calculated as a function of reduced temperature ε (=(T-TC)/TC). Based on the behaviour of effective exponents the nature of the transition in the x = 0.3 composition is described in detail. The unconventional ordering is attributed to presence of possible magnetic frustration in the system. In chapter 5 the resistivity and magnetoresistance behaviour of the x = 0.23 and 0.3 crystals are discussed. Initially the nature of plots of temperature and field variation of resistivity are described for both the cases. Detailed measurements are carried out at the magnetic transition region. The analysis is carried out in terms of critical scattering behaviour at the transition region. The zero field resistivity is analyzed in terms of theory of Fisher and Langer, while the magnetoresistance is fitted to scaling theory at the critical region developed by Balberg and Helman. It is seen that the x = 0.23 crystal shows a critical behaviour in resistivity for zero field as well as in magnetoresistance close to TC. However, the behaviour of the x = 0.3 composition is more complex. A simpler critical scattering theory alone cannot explain its large negative magnetoresistance. Chapter 6 contains the EPR studies on the x = 0.23 and 0.3 compositions. Analysis is carried out in the paramagnetic region. The EPR signals are fitted to a modified Dysonian equation. The intensity, linewidth, and asymmetry parameter are obtained as a function of temperature from fitting. The parameters are obtained till 210 K for both compositions. The intensity is fitted to a Curie Weiss law. The linewidth shows a “bottleneck” mechanism and is proportional to conductivity. Hence it is fitted to activated behaviour. In addition, a secondary signal develops at low fields from 240 K and is present till 200 K in both the compositions. This is explained by means of phase separation. In chapter 7 the specific heat of the x = 0.23 and 0.3 compositions are discussed. The measurements are carried out from 2 to 300 K in zero field and also in the presence of 3 Tesla magnetic field. The analysis is carried out in two separate sections. The first section deals with the low temperature analysis from 2 to 80 K where apart from the usual lattice, electron and magnetic terms, presence of Schottky anomaly is also discussed. The Schottky peak occurs at a relatively higher temperature of around 40 K. Due to presence of higher order lattice terms the Schottky effect is not easily discernible. It is extracted only from fitting. In the second section, the specific heat associated with ferromagnetic – paramagnetic transition is extracted. The lattice term in the entire temperature range from 10 to 300 K except at the transition region is fitted to Einstein function. The magnetic specific heat is obtained by subtracting the Einstein specific heat from the total specific heat. The change in entropy due to magnetic transition is also calculated for both compositions. In chapter 8 the general conclusions derived from the work presented in this thesis are summarized along with the scope for future work in this system.

<p>The latent-heat-storage capacity in Phase-Change Materials can be used for storing or releasing energy within a small temperature interval. Upon the phase transition taking place in a narrow temperature span, the material takes up or releases more energy compared to sensible heat storage. For an ideal phase-change material, the transition temperature is a single value, but for the most common phase-change materials on the market, used in building applications, the transition temperature is distributed within a temperature range of several degrees.</p><p>Integration of phase-change materials in building applications can be effected in several ways, for example by impregnating phase-change materials into porous building materials like concrete, wallboards, bricks or complements of the building structure. Integrating storages filled with phase-change materials makes other implementations, for instance accumulating tanks or envelopes as presented in this thesis, in an air heat exchanger. An appropriate phasetransition temperature of the supposed application is critical to the functionality of the material. For example, in cooling applications, the transition temperature of the material should be a few degrees lower than the requested comfort temperature in the building, and the opposite for heating applications.</p><p>In order to assess the thermal properties and the durability of the material, a watercalorimetric equipment was developed and employed in an accelerated testing programme. The heat capacity of the material and in particular possible change in the heat capacity over time, after thermal cycling of the material, were measured. In the thermal cycling of the material from solid to liquid phase, the temperature rise and required energy supply were recorded. The testing programme was undertaken according to control procedures and documents. In order to be able to utilize the heat-storage capacity in the best way, it is necessary to gain knowledge about thermal properties of the material, especially the long-term behaviour of the material and the deterioration rates of the thermal properties.</p><p>A semi-full-scale air heat exchanger based on phase-change material was developed and tested under real temperature conditions during the summer of 2004. The test results were used to compare and verify computer simulations made on a similar plant. The air heat exchanger utilises the ambient diurnal temperature swing to charge and discharge the phasechange material. The material tested in the calorimeter and in the air heat exchanger has an estimated phase-change temperature of about 24 °C.</p>

No description available.

Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints have led to the use of Novec fluids and fluroinerts as coolants. Although these fluids are chemically stable and have low dielectric constants, they are plagued by poor thermal properties. These factors necessitate the development of new heat transfer fluids with improved heat transfer properties and applicability. Computer Aided Molecular Design (CAMD) approach was used in this work to systematically design novel heat transfer fluids that exhibit significantly better properties than those of current high performance electronic coolants. The candidate fluids generated by CAMD were constrained by limiting their boiling points, latent heat of vaporization and thermal conductivity. The selected candidates were further screened using a figure of merit (FOM) analysis. Some of the fluids/additives that have been identified after the FOM analysis include C₄H₅F₃O, C₄H₄F₆O, C₆H₁₁F₃, C₄ H₁₂O₂Si, methanol, and ethoxybutane. The heat transfer performance of these new fluids/fluid mixtures was analyzed through pool boiling and flow boiling experiments. All the fluid mixtures tested showed an improvement in the critical heat flux (CHF) when compared to the base fluid (HFE 7200). A pool boiling model was developed using the phase field method available in COMSOL. Although these simulations are computationally expensive, they provide an alternate solution to evaluate several candidate fluids generated using the CAMD approach.

The blending of lignin as a component in a thermoplastic blend poses a challenge in the form of dispersion and compatibility. Polyesters such as poly(lactic acid) and poly(butylene adipate-co-terephthalate) offer the best opportunity of compatibility in melt blending with lignin due to their ability to form hydrogen bonds. The fractionation of lignin into more homogeneous fractions offers better dispersion and more consistent properties, retaining the toughness of the original polymer in addition to bridging stress transfer between PLA and PBAT. Functionalization of lignin was done by lactic acid grafting. The resulting blend of PLA/PBAT/modified fractionated lignin showed improved interaction between lignin and PLA, but reduced compatibility between lignin and PBAT. This thesis provides a deeper understanding on the effect of lignin heterogeneity, its fractions, and the functionalization of lignin on lignin and bioplastic blends to further the use of a largely produced industrial by-product in high value applications. / Natural Sciences and Engineering Research Council (NSERC) – Lignoworks Biomaterials and Chemicals Strategic Research Network, Canadian Foundation for Innovation (CFI), Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)