Ce travail de thèse porte sur la synthèse de nouveaux matériaux nanostructurés sous conditions extrêmes de pression et de température (P > 5 GPa et T > 1000 °C). Les matériaux que nous étudions sont basés sur un élément particulier : le bore. Ces matériaux présentent des propriétés uniques. D'une part, les allotropes du bore présentent des duretés élevées et une grande inertie chimique. D'autre part, les alliages du bore (ou borures métalliques) présentent des propriétés variées, de la thermoélectricité (HfB2) à la supraconductivité (MgB2). La synthèse en sels fondus est utilisée afin d'obtenir des systèmes nanostructurés comprenant deux composants : des nanoparticules cristallines d'environ 10 nm de borures métalliques (HfB2 ou CaB6) comprises dans une matrice de bore amorphe.Le traitement sous haute pression et température est le seul permettant de cristalliser la phase amorphe. La conservation de la nanostructure initiale est démontrée. Plusieurs nouveaux matériaux sont ainsi synthétisés : des nanocomposites borure/borate (HfB2/HfB2O5 ou CaB6/CaB2O4) ou borure/bore (HfB2/?-B ou CaB6/?-B), premiers membres de nouvelles familles de nanomatériaux. Un précurseur de bore amorphe nanostructuré synthétisé en sels fondus est ensuite utilisé. Il est cristallisé sous haute pression et haute température. En sus de la première occurrence de bore epsilon nanostructuré, deux nouvelles phases riches en bore sont obtenues, dont la structure est en cours de résolution. En somme, ce travail conduit à une nouvelle méthode de synthèse à la frontière entre la chimie des nanomatériaux et la physique des hautes pressions et températures, à l'origine de nouveaux nanomatériaux et structures. / In this PhD work, we develop a way to prepare new nanostructured materials under extreme pressure and temperature conditions (P > 5 GPa et T > 1000 °C). The studied materials are based on a specific element: boron. Indeed, these materials have unique properties. On the one hand, boron allotropes exhibit high hardness and chemical inertness. On the other hand, metal-boron alloys (metal borides) span a wide range of properties, from thermoelectricity (HfB2) to superconductivity (TiB2). We use the synthesis in molten salts to reach nanostructured systems with two components: crystalline boride nanoparticles (ca. 10 nm) embedded in an amorphous boron matrix. High pressure high temperature treatments on these systems enable crystallisation of the amorphous component into unique phases, thus yielding new nanomaterials: boride/borate (HfB2/HfB2O5 or CaB6/CaB2O4) or boride/boron (HfB2/β-B or CaB6/β-B) nanocomposites, representing the first members of new nanomaterials families. In a final step, a specific nanostructured amorphous boron precursor is synthesised in molten salts. It is crystallised under high pressure and temperature. In addition to the first nanostructured occurrence of the epsilon-boron phase, we report two new boron-rich phases, which structure is under resolution. All in all, a new synthetic route is developed at the frontier of nanomaterials chemistry and high pressure and temperature physics, leading to new nanomaterials and structures.

For the aim of production of poly(ethylene terephthalate), PET based flame retardant composites / boron based flame retardant additives, 3.5 mole hydrated zinc borate and boron phosphate were synthesized. Zinc borate was synthesized with the reaction of boric acid and zinc oxide in both laboratory and pilot scale reactors. Effects of reaction parameters on kinetics of reaction and final product particle size were evaluated. Boron phosphate was synthesized via dry, wet and microwave methods. In addition to the synthesized flame retardant additives, several non-halogenated flame retardant additives, which were commercially available, were also used. Composites were prepared using twin screw extruder and molded by injection molding, followed by characterization in terms of flame retardancy behavior, mechanical and thermal properties, and morphologies. Based on the results of first stage experiments, aiming to determine effective additives, different amounts and combinations of triphenyl phosphate, triphenyl phosphine oxide, zinc borate and microwave produced boron phosphate were chosen and used in PET matrix. Flame retardancy of the composites were determined by conducting horizontal burning rate and limiting oxygen index (LOI) tests. Smoke emissions during fire were also measured. According to the LOI test results, LOI of neat PET was determined as 21%, and with the addition of 5% boron phosphate and 5% triphenyl phosphate together, LOI was increased up to 36%. The smoke density analysis results implied that, boron phosphate was a successful smoke suppressant for PET matrix. In addition to flammability properties, tensile and impact properties of the composites were also improved with flame retardant additives and expecially with the addition of triphenyl phosphate.

Glass materials surround us, impacting our lives on a daily basis, whether geologically deposited by volcanic activity or synthesized in large volume by industry. These amorphous oxide materials are vastly important due to their variety of applications including solid electrolytes, cookware, and storage of high-level nuclear waste. Although they are used for different applications, one common characteristic of these materials is the absence of long-range periodic order. This makes it difficult to use traditional solid-state characterization methods such as x-ray and neutron diffraction to study glass structure. Nuclear magnetic resonance (NMR), is ideally suited to study materials that exhibit short-range non-periodic order as it probes directly at a nucleus of interest and is sensitive to its local structural environment. This ability of solid-state NMR is illustrated by revealing local structural features in various oxide materials presented in this thesis. Within is a compilation of studies looking at basic borates, followed by borovanadates and complex borosilicate glasses. A multinuclear application of using quantum chemical calculations, single and double resonance methods and charge-balance models are discussed to deconvolute the complex structures of these disordered materials. This is followed by a study of a difficult low-gamma nucleus, 73Ge, (once considered “impossible” for solid-state NMR) which is explored for future material studies by looking at 73Ge NMR of crystalline and glassy germanates. 73Ge chemical shifts were related to coordination environments and quadrupolar coupling constants were related to bond length distortions.

Glass materials surround us, impacting our lives on a daily basis, whether geologically deposited by volcanic activity or synthesized in large volume by industry. These amorphous oxide materials are vastly important due to their variety of applications including solid electrolytes, cookware, and storage of high-level nuclear waste. Although they are used for different applications, one common characteristic of these materials is the absence of long-range periodic order. This makes it difficult to use traditional solid-state characterization methods such as x-ray and neutron diffraction to study glass structure. Nuclear magnetic resonance (NMR), is ideally suited to study materials that exhibit short-range non-periodic order as it probes directly at a nucleus of interest and is sensitive to its local structural environment. This ability of solid-state NMR is illustrated by revealing local structural features in various oxide materials presented in this thesis. Within is a compilation of studies looking at basic borates, followed by borovanadates and complex borosilicate glasses. A multinuclear application of using quantum chemical calculations, single and double resonance methods and charge-balance models are discussed to deconvolute the complex structures of these disordered materials. This is followed by a study of a difficult low-gamma nucleus, 73Ge, (once considered “impossible” for solid-state NMR) which is explored for future material studies by looking at 73Ge NMR of crystalline and glassy germanates. 73Ge chemical shifts were related to coordination environments and quadrupolar coupling constants were related to bond length distortions.

i ABSTRACT I investigated aspects of the management of subterranean termites in the field by evaluating the protective values of preservative treated softwoods and evaluating the potential of softwoods conditioned by decay fungi or heat to produce termite monitoring and aggregating devices. As part of the investigation, it was necessary to: · develop assay techniques suitable for research into the natural resistance of timbers, the efficacy of wood preservatives and termite biology and foraging behaviour; and quantify variation in termite responses to untreated softwoods in various situations in the field using these techniques. Field bioassays were conducted with two Australian Coptotermes species to determine protection of pine sapwood afforded by borate compounds (Chapter 2). Coptotermes lacteus (Froggatt) was examined in winter and C. acinaciformis (Froggatt) in winter, spring and summer at two localities in Queensland. Hoop-(Araucaria cunninghamii Ait ex D. Don) and slash-pine (Pinus elliottii Engelm.)-sapwood blocks were placed in plastic containers and attached to termite mounds or infested trees. Termite response was determined by mass losses over five weeks and modelled. Coptotermes lacteus was relatively benign in winter and for 1.0 and 2.5% mass losses of hoop-pine sapwood, borate retentions of 0.20 and 0.06% mass/mass (m/m) boric acid equivalent (BAE), respectively, were derived. With C. acinaciformis, for 1.0 and 5.0% mass losses of hoop-pine sapwood, borate retentions ranged from 0.49 and 0.25% BAE, respectively, in winter to 0.76 and 0.47% BAE, respectively, in late summer. For 1.0 and 5.0% mass losses of slash-pine sapwood in summer, borate retentions of 0.58 and 0.14% BAE, respectively, were derived for C. acinaciformis. These results support conclusions from earlier laboratory studies conducted elsewhere. Prevention of damage by field populations of termites was not achieved. Marked intercolony variation in response to borate compounds was demonstrated, highlighting the usefulness of this rapid technique. The need for long-term field exposure trials to calibrate the lunch-box technique and to facilitate technology transfer to industry, is indicated. For comparison, termite response to white cypress (Callitris glaucophylla Thompson and Johnson), a naturally termite resistant timber, is also reported. A field bioassay was conducted to evaluate responses of C. acinaciformis to untreated southern-yellow-pine (Pinus spp.), hoop-pine and slash-pine blocks (Chapter 3). Sapwood blocks were placed in plastic containers and attached to trees infested with the termites during summer. Containers with a test block of each of the timber species were prepared. These and other containers were exposed to termites for 10 weeks. Termite feeding response (“voracity”) was assessed for all blocks by determining the mass of wood consumed. Termite voracity differed among trees. Variation in termite responses to individual hoop-pine feeder-blocks within a container was appreciable and consistent between containers. Variation in termite responses to the test blocks was appreciable, with hoop pine being significantly more susceptible to termite attack than either slash pine or southern yellow pine. Southern yellow pine is a generic name for five species of pine which are difficult to separate reliably. Therefore, caution should be exercised when using “southern yellow pine” to ensure that samples are at least from the same species of pine and preferably from the same length of timber. The sensitivity of both the bioassay and the statistical tests was demonstrated. Of particular interest was the similar level of termite response to the test timbers in the two sections of the experiment. The usefulness of feeder-blocks to initiate reliable attack rather than to promote sustained attack, is worth further attention. Sapwood stakes of Australian-grown hoop pine, slash pine, radiata pine and North American-grown southern yellow pine were exposed to subterranean termite attack in an in-ground bioassay (Chapter 4). Stakes in bait containers and bare stakes were attacked by C. acinaciformis and Schedorhinotermes intermedius (Brauer). Susceptibility of these timbers was evaluated with regard to potential for termite monitoring and aggregation. Variation between timbers and difference between termite species are described. The relevance of these data to suppressing foraging populations of subterranean termites, in Australia, using insect growth regulators, is discussed. Four field bioassays were conducted using two species of Australian subterranean termites, C acinaciformis and C. lacteus (Chapter 5). Hoop-pine blocks decayed using 14 fungi for four weeks and for 10 weeks were subsequently conditioned using dry heating, freezing or moist heating, and then exposed to termites. Blocks decayed by Gloeophyllum abietinum [Persoon: Fries] Murrill, Trametes lilacino-gilva (Berkeley) Wright & Deschamps, Schizophyllum commune Fries and Rigidoporus undatus (Persoon) Donk and subsequently oven dried, were attacked the most. Oven drying generally enhanced termite feeding responses in these two field bioassays. In a third bioassay, blocks of five softwood timber species conditioned with two high temperature regimes were exposed to C. acinaciformis. Slash pine was attacked the least. Mean mass losses for hoop pine, Caribbean pine (Pinus caribaea Morelet), radiata pine and the interspecific F1 hybrid between Caribbean and slash pine were not significantly different. For C. lacteus, slash and hoop-pine blocks were attacked the least while radiata pine was attacked the most. Additional heating at 105°C increased the susceptibility of most timber species. Relationships between heating duration and the consumption of hoop-pine-sapwood blocks were determined using results from a fourth bioassay. Heating the timber increased feeding responses for both termite species. The selective and rapid response of the termites highlights the usefulness of this field technique for multiple-choice bioassays. The cyclodiene termiticides were withdrawn from use, in Australia, as from 30 June 1995. Implications for the management of subterranean termites in Queensland are discussed. Community perceptions of the use of chemical pesticides and cost do not favour the widespread use of preservative treated timber in buildings. An integrated pest management approach to termite control is the likely direction for the future in Australia. A range of building techniques, regular inspections, and attention to factors that predispose existing buildings to termite attack can reduce the risk of damage from termites, but do not eliminate that risk. There will be an increased need for reliable preventative and remedial treatments involving bait technology. Much more work is needed on termite biology, foraging behaviour and bait toxicants before a baiting system can be confidently commercialised in Australia. Directions for research in Queensland are discussed.

Orientador: Victor Ciro Solano Reynoso / Banca: Cláudio Luiz Carvalho / Banca: Raul Fernando Cuevas Rojas / Resumo: Estudamos o sistema 40P2O5 - 10B2O3 - (50-x)CaO - xTiO2, onde variou-se a composição do TiO2 e CaO, com x=25,20,15,10,05,03 mol%. Neste sistema temos dois formadores de vidros, o P2O5 que pode incorporar na sua rede grande quantidade de Titânio e o B2O3. Dois grupos de amostras foram estudados: um sem polarizar, e outro grupo submetido à polarização eletro térmica a 300oC aplicando 1,5KV e 2,5 KV durante 60 minutos. Foram realizadas medidas de Análise Térmica diferencial e se observa que estes vidros possui transição vítrea entorno de 600ºC, aumentando com maior quantidade de TiO2. A evidência da polarização eletro térmica se observa nos espectros de infravermelho e Uv-Vis, nestas, as bandas de absorção correspondentes sofreram ligeiras mudanças. Para estes vidros são importantes as bandas de absorção na região visível que se estende desde 400nm até 900nm devido à existência de íons Ti3+ e pares Ti3+-T 4+ em estruturas de coordenação tetraedral e octaedral. As medidas da dispersão dos índices de refração utilizando a técnica do ângulo de Brewster mostram variações conforme os comprimentos de onda. Foi avaliado o índice de refração complexo dos espectros de transmitância e refletância. A análise da parte real do índice de refração foi feita através do modelo de um único oscilador de Wemple-Didomenico que está relacionado com a dispersão normal dos vidros. Os parâmetros como energia média e energia de dispersão são baixos quando comparados com outro vidros com TiO2. Os dados da absorção na forma da função dielétrica complexa foram ajustados utilizando funções gaussianas. Os resultados indicam a formação de bandas de absorção de íons Ti3+ com estruturas possivelmente distorcidas e de coordenação tetraedral e octaedral. Temos ainda as bandas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: We studied the system 40 P2O5 - 10 B2O3 - ( 50 - x ) CaO - x TiO2, which has varied the composition of CaO and TiO2, with x = 25, 20, 15, 10, 05, 03 mol%. In this system we have two glass formers, the P2O5 that can incorporate in its network great amount of titanium B2O3. Two groups of samples were studied: one without polarize, and another group submitted to a thermal electric polarization by 300ºC applying 1.5 KV and 2.5 KV for 60 minutes. Measures were made of differential thermal analysis and observed that these glasses have glass transition around 600ºC, increasing with a great amount of TiO2. The evidence of thermal electric polarization is observed in the spectra of infrared and UV-Vis, in the corresponding absorption bands have slightly changes. For these glasses are important the absorption bands in the visible region that extends from 400nm to 900nm due to the existence of ion Ti3+ pairs and Ti3+ - T4+ in co-ordination structures tetraedral and octaedral. The measures of dispersion of the indices of refraction using the technique of Brewster angle showed variations according to wavelengths. We evaluated the complex refractive index of the spectra of transmittance and reflectance. The analysis of the real part of the index of refraction was done by a single oscillator model of Wemple-Didomenico related to the normal dispersion of glass. The parameters such as average energy and energy dispersion are low when compared with other glasses with TiO2. The data of absorption in the form of complex dielectric function were fitted using Gaussian functions. The results indicate the formation of absorption bands of ions Ti3+ with possibly distorted structures and coordination tetraedral and octaedral. We have the bands due to the existence of pairs of ions Ti3+ - Ti4+ and undergo changes as the samples polarized and not polarized. / Mestre

[pt] A determinação de elementos traços em amostras de rocha por espectrometria de massas, combinada com ablação a laser (LA-ICPMS), tem se tornado uma importante ferramenta nas investigações em petrogênese, metalogênese e na prospecção de minérios. Apesar do surgimento de uma nova geração de lasers com menor duração de pulso (fs) e comprimento de onda (<266 nm), a calibração é ainda um ponto crítico, pois em geral, não há padrões disponíveis com matriz semelhante. Uma das interferências não espectrais mais relevantes em LA-ICPMS é o fracionamento químico, o qual acarreta diferenças entre as composições do alvo (padrão ou amostra) e da massa ablacionada, comprometendo a exatidão e a repetitividade dos resultados. Quando a análise integral é o objetivo principal, o assemelhamento de matriz pode ser alcançado por simples fusão das amostras e padrões em misturas de meta e tetraboratos, de modo similar ao que é feito, rotineiramente, na análise por fluorescência de raios-X (XRFA). Este trabalho relata metodologia para a determinação de elementos traços em amostras de basaltos, provenientes de sítios de exploração de petróleo. Os experimentos foram realizados com um sistema de ablação a laser CETAC LSX-100 em combinação com um espectrômetro ELAN 5000 ICPMS. Uma mistura de argônio-nitrogênio (2 % N2, 98 % Ar) foi utilizada como gás carreador, com o intuito de aumentar a massa ablacionada, e consequentemente, melhorar as intensidades de sinal e reduzir os limites de detecção. Conectou-se uma câmara ciclônica antes da tocha do ICP, com o objetivo de uniformizar o tamanho das partículas de aerossol, e deste modo, melhorar a repetitividade da medição e a robustez do plasma. A título de comparação, análises também foram feitas sem o emprego desta câmara. Padrões de calibração foram preparados a partir de dois materiais de referência certificados, o basalto NIST SRM 688 e a obsidiana NIST SRM 278. Os padrões de rochas pulverizadas foram misturados e homogeneizados com fundente de borato de lítio (CLAISSE, puro, 75 % Li2B4O7, 25 % LiBO2) nas proporções mássicas de rocha: fundente de 1:5, 1:11, 1:23, 1:47, respectivamente, obtendose, deste modo, cada padrão em quatro diferentes concentrações. O padrão interno escolhido foi o In, tendo sido este adicionado antes da fusão, resultando em alvos com a concentração de 100 mg kg(-1) neste elemento. Obtiveram-se os brancos, de modo similar, usando o fundente borato de lítio. A validação metodológica foi feita empregando-se o basalto (GSJ, JB-2) e o granito (NIMG, SARM-1), tendo sido a partir destes, preparados vidros com a proporção mássica (amostra: fundente) de 1:5 e contendo o padrão interno. Todas as fusões foram feitas em um forno de fusão automático (CLAISSE Fluxy). Análises por ICPMS e ICP OES foram feitas após dissolução de fragmentos dos alvos em HNO3, para verificação de possíveis perdas de elementos voláteis. Quarenta elementos foram determinados, a maioria das curvas de calibração apresentou coeficiente de determinação (R2) maiores que 0,995. Limites de detecção variaram de 0,013 mg kg(-1) para Tb, até 0,6 mg kg(-1) para Zn. Estes valores foram melhorados para vários elementos pelo uso da câmara ciclônica (V, Zn, Rb, Y, Nb, Ba, Ce, Sm, Tb, Dy, Ho, Tm). Nas análises do basalto (GSJ, JB-2) e do granito (NIMG, SARM-1), a exatidão foi melhor do que 5 % para V, Sr, Y, Ba, Ce, Nd, Yb e Lu; entre 5-10 % para: Sc, Zn, Rb, Tm, e de 10-20 % para: Co, Zr, La e Tb. A repetitividade foi melhor do que 5% para V, Rb, Sr, La, Nd, Ta; entre 5-10 % para: Sc, Co, Zn, Sr, Y, Zr, Ba, Tb, Yb; e de 10-20 % para: Ce, Tm, Lu e Hf. Foi utilizado ainda o método semiquantitativo TotalQuant II o qual, dentro da incerteza esperada para este tipo de calibração (cerca de 10 % a 20 %), forneceu resultados concordantes com calibração externa quantitat / [en] Determination of trace elements in rock samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) has become an important tool for investigations in petrogenesis, metallogenesis and ore prospecting. However, despite the availability of new generation lasers with shorter pulse duration (fs) and wave length (<266 nm), calibration remains still a critical issue when matrixmatched standards are not available. One of the most serious non- spectral interference in LA-ICPMS is chemical fractionation, which causes compositions of standard and sample and their respective ablated masses to be different, thus compromising accuracy and precision of the results. When bulk analysis is the main objective, matrix matching can be achieved by the simple fusion of samples and standards with meta/tetraborates fluxes, similar to what is routinely used in XRFA. This work reports on our experience with this procedure in the analysis of basaltic rocks, aiming at the trace element characterization of host rocks from oil exploration sites in Brazil. The experiments were performed with a CETAC LSX- 100 laser ablation system (Nd:YAG, 266 nm, operated in the Q-switched and scanning mode) coupled to an ELAN 5000 ICPMS. An argon- nitrogen mixture (2 % N2, 98 % Ar) was used as carrier gas to enhance the mass of material ablated, thus increasing signal intensities and reducing detection limits. A cyclonic spray chamber was arranged just before the ICP-torch as a tentative to uniform aerosol particle size for improving measurement repeatability and robustness of the plasma. For comparison, the system was also operated without a spray chamber. Calibration samples were prepared from two standard reference materials: NIST SRM 688 basalt and NIST SRM 278 obsidian. The powdered rock standards were mixed and homogenized with a lithium borate flux (CLAISSE, pure, 75 % Li2B4O7, 25 % LiBO2) using rock-to-flux mass ratios of 1:5, 1:11, 1:23 and 1:47, respectively, thus obtaining each standard in four different analyte concentrations. Indium was used as an internal standard (IS) and was added before fusion to achieve targets with IS concentration of 100 mg kg(-1). Blanks from the lithium borate flux were produced in a similar way. Method validation was performed with GSJ basalt JB-2 and NIMG granite SARM-1, prepared at a constant sampleto- flux mass ratio of 1L:5 and containing also the IS. All fusions were performed in an automated furnace (CLAISSE Fluxy). Solution nebulization ICP-MS/OES after dissolution of smaller target pieces in HNO3 was used to assess for volatilization losses. Forty elements were determined and good linearity of the calibration curves was obtained and for most of them the correlation coefficient (R2) was higher than 0.995. Detection limits ranged from 0.013 mg kg(-1) for Tb to 0.6 mg kg(-1) for Zn, and improved for several elements by using a cyclonic spray chamber (e.g. V, Zn, Rb, Y, Nb, Ba, Ce, Sm, Tb, Dy, Ho, Tm). In the analysis of GSJ basalt JB-2 and NIMG granite SARM-1, accuracy was better than 5 % for: V, Sr, Y, Ba, Ce, Nd, Yb, and Lu; between 5-10 % for: Sc, Zn, Rb, Tm, and 10-20 % for: Co, Zr, La and Tb. Repeatability was better than 5 % for: V, Rb, Sr, La, Nd, Ta, between 5-10% for: Sc, Co, Zn, Y, Zr, Ba, Tb, Yb, and 10-20 % for: Ce, Tm, Lu and Hf. Additionally, the semiquantitative TotalQuant II calibration was applied, which gave, within the expected uncertainty for this calibration method (10 % to 20 %), concordant results when compared to the quantitative external calibration procedure. Preliminary results on the application of these methods for the determination of trace elements in basaltic host rocks from oil exploration sites will be shown.