In order to make much stiffer, light weight and high performance material products, polymer nanocomposites play an emerging role in the material innovation. Unlike other thermoplastics, polymer nanocomposites are fabricated by introducing a small amount of solid nano-scale fillers (normally less than 5 wt%) such as nanoclay, carbon nanotubes or nanofibres into a plastic resin to dramatically enhance its stiffness, strength and thermal properties. The difference between nanocomposites and conventional fibre composites is that the added fillers are extremely small, only one-millionth of a millimetre thick, and provide a much larger interface area per unit volume for greatly improving the interfacial bonding effect between nanofillers and the polymer matrix. More importantly, polypropylene (PP)/clay nanocomposites have quite a high potential to form such innovative materials and replace the conventional plastics in many automotive and packaging applications. Nevertheless, the growth of PP/clay nanocomposites faces an obstacle of hydrophobic polymer’s low interactions with hydrophilic clay. Maleic anhydride (MA) grafted PP (MAPP), commonly used as a compatibiliser, has been proven to facilitate a good clay dispersion within the PP matrix through its functionalised MA groups. But despite the great attention from the manufacturers and researchers in recent years,commercial PP/clay nanocomposites with reliable material properties are still limited in availability. The major problem stems from the complex influences of the material selection and processing methods. The present work developed a comprehensive approach from the material formulation and processing, experimental characterisation to the numerical modelling of PP/clay nanocomposites based on the finite element analysis (FEA) of micro/nanostructures. Initially, effects of the material selection including the clay type and content, MAPP content and PP matrix viscosity were investigated for the mechanical property enhancement of PP/clay nanocomposites. These nanocomposites were prepared using twin screw extrusion and injection moulding processes with a well-known Taguchi design of experiments (DoE) method in order to statistically detect the significant factors for influencing their mechanical properties. The preferred material formulations were then determined by Pareto analysis of variance (ANOVA) with the technical and economic considerations. The fundamental material characterisation was also conducted on those formulated nanocomposites using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Overall mechanical properties of neat PP and corresponding nanocomposites were determined by the general tensile, flexural and impact tests. Finally, computational models were established by implementing both the representative volume element (RVE) technique and innovative object-oriented finite element (OOF) analysis to predict the tensile moduli of PP/clay nanocomposites in comparison to the experimental data and available composites theoretical models. / This research work was sponsored by Foundation for Research, Science and Technology (FRST), New Zealand under the grant #UOAX 0406 and financially supported by Tertiary Education Commission (TEC), New Zealand through Bright Future Top Achiever Doctoral Scholarship to Yu Dong.

In order to make much stiffer, light weight and high performance material products, polymer nanocomposites play an emerging role in the material innovation. Unlike other thermoplastics, polymer nanocomposites are fabricated by introducing a small amount of solid nano-scale fillers (normally less than 5 wt%) such as nanoclay, carbon nanotubes or nanofibres into a plastic resin to dramatically enhance its stiffness, strength and thermal properties. The difference between nanocomposites and conventional fibre composites is that the added fillers are extremely small, only one-millionth of a millimetre thick, and provide a much larger interface area per unit volume for greatly improving the interfacial bonding effect between nanofillers and the polymer matrix. More importantly, polypropylene (PP)/clay nanocomposites have quite a high potential to form such innovative materials and replace the conventional plastics in many automotive and packaging applications. Nevertheless, the growth of PP/clay nanocomposites faces an obstacle of hydrophobic polymer’s low interactions with hydrophilic clay. Maleic anhydride (MA) grafted PP (MAPP), commonly used as a compatibiliser, has been proven to facilitate a good clay dispersion within the PP matrix through its functionalised MA groups. But despite the great attention from the manufacturers and researchers in recent years,commercial PP/clay nanocomposites with reliable material properties are still limited in availability. The major problem stems from the complex influences of the material selection and processing methods. The present work developed a comprehensive approach from the material formulation and processing, experimental characterisation to the numerical modelling of PP/clay nanocomposites based on the finite element analysis (FEA) of micro/nanostructures. Initially, effects of the material selection including the clay type and content, MAPP content and PP matrix viscosity were investigated for the mechanical property enhancement of PP/clay nanocomposites. These nanocomposites were prepared using twin screw extrusion and injection moulding processes with a well-known Taguchi design of experiments (DoE) method in order to statistically detect the significant factors for influencing their mechanical properties. The preferred material formulations were then determined by Pareto analysis of variance (ANOVA) with the technical and economic considerations. The fundamental material characterisation was also conducted on those formulated nanocomposites using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Overall mechanical properties of neat PP and corresponding nanocomposites were determined by the general tensile, flexural and impact tests. Finally, computational models were established by implementing both the representative volume element (RVE) technique and innovative object-oriented finite element (OOF) analysis to predict the tensile moduli of PP/clay nanocomposites in comparison to the experimental data and available composites theoretical models. / This research work was sponsored by Foundation for Research, Science and Technology (FRST), New Zealand under the grant #UOAX 0406 and financially supported by Tertiary Education Commission (TEC), New Zealand through Bright Future Top Achiever Doctoral Scholarship to Yu Dong.

In order to make much stiffer, light weight and high performance material products, polymer nanocomposites play an emerging role in the material innovation. Unlike other thermoplastics, polymer nanocomposites are fabricated by introducing a small amount of solid nano-scale fillers (normally less than 5 wt%) such as nanoclay, carbon nanotubes or nanofibres into a plastic resin to dramatically enhance its stiffness, strength and thermal properties. The difference between nanocomposites and conventional fibre composites is that the added fillers are extremely small, only one-millionth of a millimetre thick, and provide a much larger interface area per unit volume for greatly improving the interfacial bonding effect between nanofillers and the polymer matrix. More importantly, polypropylene (PP)/clay nanocomposites have quite a high potential to form such innovative materials and replace the conventional plastics in many automotive and packaging applications. Nevertheless, the growth of PP/clay nanocomposites faces an obstacle of hydrophobic polymer’s low interactions with hydrophilic clay. Maleic anhydride (MA) grafted PP (MAPP), commonly used as a compatibiliser, has been proven to facilitate a good clay dispersion within the PP matrix through its functionalised MA groups. But despite the great attention from the manufacturers and researchers in recent years,commercial PP/clay nanocomposites with reliable material properties are still limited in availability. The major problem stems from the complex influences of the material selection and processing methods. The present work developed a comprehensive approach from the material formulation and processing, experimental characterisation to the numerical modelling of PP/clay nanocomposites based on the finite element analysis (FEA) of micro/nanostructures. Initially, effects of the material selection including the clay type and content, MAPP content and PP matrix viscosity were investigated for the mechanical property enhancement of PP/clay nanocomposites. These nanocomposites were prepared using twin screw extrusion and injection moulding processes with a well-known Taguchi design of experiments (DoE) method in order to statistically detect the significant factors for influencing their mechanical properties. The preferred material formulations were then determined by Pareto analysis of variance (ANOVA) with the technical and economic considerations. The fundamental material characterisation was also conducted on those formulated nanocomposites using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Overall mechanical properties of neat PP and corresponding nanocomposites were determined by the general tensile, flexural and impact tests. Finally, computational models were established by implementing both the representative volume element (RVE) technique and innovative object-oriented finite element (OOF) analysis to predict the tensile moduli of PP/clay nanocomposites in comparison to the experimental data and available composites theoretical models. / This research work was sponsored by Foundation for Research, Science and Technology (FRST), New Zealand under the grant #UOAX 0406 and financially supported by Tertiary Education Commission (TEC), New Zealand through Bright Future Top Achiever Doctoral Scholarship to Yu Dong.

- / -

Les couches minces de LiNbO3 (LN) avec des orientations du single cristallographique en dehors-du-plan et dans-le-plan sont nécessaires pour les dispositifs optiques et acoustiques. La technique PIMOCVD est adapté pour la déposition de couches minces de LN avec des orientations cristallographiques différentes sur des substrats monocristallins. Pour obtenir des couches avec une surface lisse et composé une phase pure de LN avec une concentration contrôlé de Li, les paramètres de déposition ont été ajustés.Un effort particulier a été mis dans la croissance de couches avec une orientation unique dans-le-plan. La qualité cristalline, la qualité de l’épitaxie, Li2O nonstoichiometrique, l’orientation dans-le-plan, le stress résiduel et le twinning ont été étudiés avec la diffraction des rayons X et la spectroscopie Raman. Couches de LN avec composition presque stoichiometrique on été obtenues. Les couches épaisses ont tendance à se fracturer et à former twins pour détendre les grands stress thermique. Les différences dans les mécanismes de relaxation et dans la capacité de supporter des stress dans les couches de X-, Y- et Z-LN sont discutés. Dans le cas des couches Z-LN le stress thermique sont equi-biaxial quand le stress dans les couches X- et Y- sont anisotropies. On a étudié aussi la structure des domaines ferroélectriques et la réponse piézoélectrique des couches. L’énergie de bande et l’indice de réfraction des couches de LN, mesuré pas elipsometrie spectrale, sont très proche de ceux du LN monocristallin. On démontre expérimentalement la présence d’une résonance à 5.5 GHz dans un résonateur à un seul port réalisé dans une couche de Z-LN/saphir de 150 nm d’épaisseur. / LiNbO3 (LN) thin films are attracting interest due to possibility to miniaturize, to integrate and to ameliorate the performance of acoustical and optical devices. These applications require LN films with single crystallographic out-of-plane and in-plane orientations. PIMOCVD technique was used for deposition of high quality of different crystallographic orientations LN thin films, offering a possibility to obtain films with various different cut on single crystalline substrates.In order to obtain films with smooth surface and consisting of pure LN phase with controlled Li concentration, the deposition parameters were tuned.A particular effort was done to obtain films with single in-plane orientation. The crystallinity, epitaxial quality, Li2O nonstoichiometry, in-plane orientation, residual stresses and twinning were studied by means of X-ray diffraction and Raman spectroscopy. The LN films with nearly stoichiometric composition were obtained. The thick films tend to crack and to form the twins in order to relax the high thermal stresses. The differences in relaxation mechanisms and in ability to withstand high stresses of X-, Y- and Z-LN films were discussed. In the case of Z-LN films the thermal stresses are equibiaxial, while the stresses in X- and Y- films are anisotropic. The ferroelectric domain structure and piezoelectric response of grown films were investigated. Energy gap and refractive indexes of LN films, measured by spectroscopic ellipsometry, were similar to those of single crystal. Acoustic resonance at 5.5 GHz in single-port resonators based on as-grown 150 nm thick Z-LN film on sapphire films was demonstrated experimentally.

The objective of this work is to assess the potential of Mn-Fe-Si-P for magnetic heat pump applications. Mn-Fe-Si-P is a first order transition magnetocaloric material made from safe and abundantly available constituents. A significant magnetocaloric effect occurs at the transition temperature of the material. The transition temperature can be tuned by changing the atom ratios to a region near room temperature. Mn-Fe-Si-P in magnetic heat pumps is investigated by determining the material's properties, 1D system modeling and experiments in a magnetic heat pump prototype. We characterize six samples of Mn-Fe-Si-P, based on their heat capacity and magnetization. The reversible component of the adiabatic temperature change is found from the entropy diagram and compared to cyclic adiabatic temperature change measurements. Five of the six samples are selected to be formed into epoxy xed crushed particulate beds, which can be installed into a magnetic heat pump prototype. A system model is constructed to understand the losses of the magnetic heat pump prototype. Several experiments are performed with Gd with rejection temperatures around room temperature. Including dead volume and casing losses improves the modeling outcomes to match the experimental results closer. Experiments with Mn-Fe-Si-P are performed. Five materials are formed into modular beds that can be combined into two layer configurations. Six experimental configurations are tested, one single layer regenerator test with a passive lead second layer, and five experiments using two layers with varying transition temperature spacing between the materials. The best performance of the beds was found at close spacing at suitable rejection temperatures. It was found that at far spacing, the performance of stronger materials would produce a lower temperature span than that of weaker materials at close spacing. The experiments provide results that are used to validate the system modeling approach using the material data obtained of the Mn-Fe-Si-P samples. We integrate material properties into a system model. A framework is proposed to take into account the hysteresis. This framework shows an improvement of the predicted trend for a single layer case. The proximity of simulation and experimental multi-layering results are dependent on the rejection temperature. At the higher end of the rejection temperature the modeling results over-predict the temperature span around the active region. At lower rejection temperatures the simulation under-predicts the experimental temperature span. The inclusion of experimental pressure drop improved the trends found at higher rejection temperatures. A further improvement was found varying the interstitial heat transfer term. Modeling future research should focus on characterizing the thermo-hydraulic closure relationships for crushed particulate epoxy xed beds, and improvements to the heat loss model. Mn-Fe-Si-P is able to produce a temperature span, when a suitable set of Mn-Fe- Si-P materials are selected based on minimal hysteresis, making it a viable material for magnetic heat pump applications. The performance of Mn-Fe-Si-P is further improved by layering materials with a closely spaced transition temperature. Future research should focus on increasing the production of Mn-Fe-Si-P materials with low hysteresis, and improving the regenerator matrix geometry and stability. / Graduate

To support the concept of environmentally friendly materials and sustainable development, the low-carbon cementitious materials have been extensively studied to reduce amount of CO2 emission to the atmosphere. One of the efforts is to promote alternative cementitious binders by utilizing abundant alumina-silicate wastes from the industrial sectors (e.g. fly ash or furnace slag), among which “Geopolymer (GP) cement” has received most attention as it can perform a wide variety of behaviours, in addition to cost reduction and less environmental impacts. The most common geopolymer production, fly ash-based, gained some strength with very slow rate at ambient temperature, while the strength is evidently improved when cured in high (above room) temperature, e.g. over 40°C. The major challenge is to step over the limitation of heat curing process and inconvenience in practice. In this study, the testing schemes of (i) GP manufacturing in various processes, (ii) inclusion of ordinary Portland cement (OPC) in GP mixture, called GeoPC and (iii) GeoPC manufactured with dry-mixing method, have been intensively investigated through mechanical testing (Setting time, Compressive strength and Internal heat measurement) and mechanism analysis (XRD, FTIR, SEM and EDXA) in order to develop the geopolymers, achieving reasonable strength without external sources of heat curing. It is found that the proposed (dry) mixing process could have generated intensive heat liberation which was observed as a comparable factor to heat curing from any other external sources, enhancing the curing regime of the mixture. The additional calcium content in the developed GeoPC system not only resulted in an improvement of an early strength by the extra precipitation of calcium compounds (C,N-A-S-H), but also provided a latent heat from the reaction of its high potential energy compounds (e.g. OPC or alkaline activators). The developments from these approaches could lead to geopolymer production to achieve reasonable strength in ambient curing temperature known as “Self-cured geopolymer cement”, without external heat, and hence provide construction industry viable technologies of applying geopolymers in on-site and off-site construction.

An abstract is a reduced scholarly document crucial for relevant scientific articles and full text documents selection. Therefore abstracts should briefly and clearly represent the full text content. The aim of this research is to construct proper structure, which would be internationally as well as interdisciplinary applied, primarily within the European Union. The structure used in the research was supposed to be evaluated as the most suitable one by the experts. There were 2 material science journals (100 abstracts from each journal) selected. Those samples were analysed in freeware Weft QDA, designed for content analysis of text documents. Sample abstracts were based on the content analysis resulting data. The samples were evaluated by material science experts in the survey. The most common combination of categories in original abstracts were background, methodology and results. The repsonses of surveys pointed out, that the recommended abstract include all necessary information and exclude the redundant ones.

We present a generic, problem-independent algorithm for exploration of the low-energy portion of the energy landscape of discrete systems and apply it to the energy landscape of lattice proteins. Starting from a set of optimal and near-optimal conformations derived from a constraint-based search technique, we are able to selectively investigate the lower part of lattice protein energy landscapes in two and three dimensions. This novel approach allows, in contrast to exhaustive enumeration, for an efficient calculation of optimal and near-optimal structures below a given energy threshold and is only limited by the available amount of memory. A straightforward application of the algorithm is the calculation of barrier trees (representing the energy landscape), which then allows dynamics studies based on landscape theory.

Research efforts towards realizing electrochemically-stable organic semiconductors have been a focus of the organic light-emitting diode (OLED) industry for decades. This is especially true for the discovery of blue-light emitting materials and compounds with optical band gaps greater than 2.8 eV as these materials undergo rapid degradation resulting in poor operational lifetimes. Benzo[1,2-d:4,5-d']bis(oxazole)s and benzo[1,2-d:4,5-d']bis(oxazole)s (BBOs) are useful building blocks that generate highly fluorescent materials with robust thermal and photo-oxidative stabilities and optical band gaps >2.8 eV. Previously, the Jeffries-EL group has synthesized and studied polymeric BBO systems for OLED application, which achieved sky-blue electroluminescence (EL) with external quantum efficiencies (EQEs) of approximately 1.1 %. However, these systems are plagued with broad electroluminescence due to their polydispersity and have yet to achieve power efficiencies >10 lm/W. Small molecule BBO-based emitters (SM-BBOs) are advantageous due to their discrete size, uniform pi-electron delocalization, and high purity. To date, SM-BBOs have realized deep blue EL with good color purity and EQEs approaching 3%. However, the number of possible structural variants are vast, but known examples of these systems are limited, thus more work is required to increase our understanding of these systems to develop SM-BBOs-based OLEDs with higher efficiencies for commercial utility. Herein, several classes of SM-BBOs bearing various aryl substituents are computationally and experimentally studied to understand fundamental optical and electronic properties. This data is used to determine the structure-property relationships between SM-BBO systems and to design functional microelectronic OLEDs. The collected experimental data is used by our computational teams to improve our predictive strategies and refine synthetic efforts. As such, several SM-BBOs were achieved which produced near-UV and deep-blue EL while combinations of these products were used to obtain the first prototype white OLEDs with temperature tunability using SM-BBO emissive materials. / 2022-09-07T00:00:00Z