The problem of surface area and particle size determination has been examined. A survey of the methods for measuring the surface areas and average sizes of aggregates of fine particles was made and a method selected for Improvement. An apparatus employing the principles of fine particle measurement established in turbidimetry was constructed. Experimental work with the apparatus was conducted in an attempt to establish a single method of particle size measurement. The results warrant the conclusion that the apparatus will measure average surface diameters of single component materials, constant assaying materials, and mixtures containing one semi-transparent material. A value for the relative surface area of these materials can also be determined. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

A study of the Fermi surface of copper at room temperature has been made by means of a positron annihilation technique. A positron active copper single crystal was placed midway between two “point" scintillation counters operated in time coincidence. The coincidence count rate was measured for various crystal orientations and the count rate interpreted as a measure of the diameter of the Fermi surface. The experiment yields a Fermi surface that is spherical in k-space except for protrusions in the {111} directions which are estimated to subtend an angle of about 20° at k = 0. Within experimental error the results are consistent with those obtained by other methods near 0° K. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A positron annihilation experiment involving collinear point geometry is used to make a direct comparison of the k₁₁₀ and k₁₀₀ Fermi radii in a single crystal of lithium. It is found that is k₁₁₀ greater than k₁₀₀ by 5.6 ± 1.2%, in agreement with theory and a phenomenological interpretation of an earlier long slit experiment. The higher momentum components of the positron wavefunction are calculated by a direct method and found to be negligible. On the other hand, a less straightforward estimate based on a flattened Seitz potential shows that the higher momentum components of the electron wavefunction significantly reduce the experimentally observed anisotropy. Hence, the difference of 5.6% should be regarded as an upper limit on the true distortion of the Fermi surface of lithium. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Les oxo-anions tels que le sélénite et le sélénate (SeO32-/ SeO42-) et les oxo-cations tels que l’uranyle (UO22+) sont des polluants que l’on trouve dans les déchets nucléaires ultimes destinés à être stocké en couches géologiques profondes. L’adsorption des oxo-anions a été étudiée sur une surface d’oxyde modèle : le dioxyde de titane TiO2. Le but étant de comparer les comportements en fonction des différentes faces cristallographiques, les travaux ont été réalisés sur poudres et monocristaux. Une étape préliminaire importante s’est attachée à la caractérisation de l’hydroxylation de la surface des monocristaux. Des travaux d’adsorption en batch ont ensuite été réalisés suivis d’une caractérisation spectroscopique des interfaces eau/oxyde au moyens de diverse méthodologies telles que la spectroscopie de photoélectrons X (XPS), la spectroscopie par diffusion Raman en champ lointain et en champ proche, la spectroscopie de génération de seconde harmonique (SGSH), la microscopie à force atomique (AFM). Les poudres de rutile ont été caractérisées par mesures électrocinétiques et des courbes de cinétique de sorption ainsi que des sauts de sorption en fonction du pH ont été réalisés. L’influence du sel de fond (NaCl, NaClO4) ainsi que l’influence de la lumière sur l’adsorption ont été étudiés. Ceci a permis de mettre en évidence un processus de photoréduction du sélénium(6) en sélénium(4). La seconde partie de ces travaux de thèses sont des études exploratoires basées sur des méthodes spectroscopiques innovantes telles que la spectroscopie de fluorescence en champ proche. Elles concernent le suivi et l’analyse du type d’interactions entre le cation Europium(III), cation modèle pour les actinides et lanthanides trivalents, et de deux matrices disctinctes : un verre aluminate de type verre de stockage de déchets nucléaires et une argile de la famille des kaolins : la dickite. / Oxo-anions such as selenite/selenate (SeO32-/ SeO42-) and oxo-cationss such as uranyl (UO22+) are contaminants found in ultimate nuclear wastes (79Se) which could be stored in deep geological media. Furthermore, selenium mobile species can be found in high amount in some polluted soils. Adsorptions of selenite and selenate were studied on a model oxide surface, namely rutile TiO2. The final goal was to find out possible differences in reactivity among crystallographic faces and try to extrapolate the results to the powder behaviour. The goal of these studies was to use spectroscopic characterizations and batch experiments in order to propose surface complexes. As our interest is focused on the chemistry of the water/oxide interface, surface specific methods are thus required. Techniques used in this work are Angle Resolved X-Ray Photoelectron Spectroscopy, Near-Field Raman Spectroscopy (NFRS), Surface Second Harmonic Generation (SSHG), and Atomic Force Microscopy (AFM). Batch experiments were performed on powders, electrokinetics measurements, sorption edge curves and sorption kinetics curves were also realized. The influence of the salt used for adjusting the ionic strength (NaClO4 and NaCl) and, as titanium dioxide exhibits strong photocatalytic properties, the influence of sunlight were also studied. A photoreduction processus from Se(VI) to Se(IV) was evidenced. The second part of this manuscript presents some exploratory works dealing with innovative spectroscopies like Near-Field Luminescence applied to the study of Eu3+ interaction with an aluminate glass and a model clay : dickite.

A highly sensitive reflection-absorption infrared spectrophotometric technique was used to investigate the adsorption of sodium oleate from aqueous solutions onto magnesium carbonate (magnesite) thin film substrates. Valuable qualitative results were obtained, regarding the nature of the adsorbed species and their molecular orientation. However, this orientation effect strongly influenced the relative intensities of the infrared absorption bands; this prevented precise quantitative determinations. Under moderately acidic conditions, the original surface charge of magnesite was positive and near zero. The anionic collector was chemisorbed, forming only one type of complex, very similar to the bulk magnesium oleate. The hydrocarbon chains were oriented nearly parallel to the substrate, forming a homogeneous partially polymerized epoxide-polyether layer, strongly laterally bound, at the sites of the former C=C double bonds. The C-0 bonds were formed following a partial oxidation of the oleate in solution, by oxygen from the air. This adsorbed film converted the carbonate surface to a strongly hydrophobic condition, which was responsible for the high flotation recoveries obtained. Under basic conditions, the original magnesite surface was negatively charged. This limited the formation of the chemisorbed collector complex to a lower amount; different complexes, probably physically adsorbed, joined in forming a film. However, this was a more heterogenous film, showing different molecular orientations - - from nearly parallel, to closer to the normal to the adsorbent's surface. These aspects caused a net decrease in the degree of hydrophobicity, in comparison to the acidic conditions. The same oxidation and polymerization effects were observed, although to a lower extent. The film was also very stable. These properties of the adsorbed film were consistent with the lower flotation response observed under basic conditions. Therefore, more concentrated collector solutions were needed, to reach the same high recoveries obtained under moderately acidic conditions. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Orientadores: Richard Landers, Abner de Siervo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T07:30:46Z (GMT). No. of bitstreams: 1 Carazzolle_MarceloFalsarella_D.pdf: 4221752 bytes, checksum: 6156780985399992bdd317898895589e (MD5) Previous issue date: 2014 / Resumo: O descobrimento de novos materiais com alta constante dielétrica e compatível com o atual processo de fabricação de dispositivos CMOS (complementary metal-oxide-semiconductor) tem sido uma grande barreira tecnológica que está impedindo as indústrias de semicondutores a manter o contínuo aumento de desempenho desses dispositivos. O principal limitante da atual tecnologia está sendo os efeitos indesejáveis de corrente de fuga através do dielétrico que ocorrem devido à contínua miniaturização dos transistores. Além de esse novo material possuir uma alta constante dielétrica também é fundamental que ele tenha uma estabilidade térmica sobre a superfície de Si ou Ge, uma vez que o processo de fabricação desses CMOS requererem tratamentos térmicos necessários para ativação dos dopantes que chegam a temperaturas da ordem de 900 oC para Si e 400 oC. O HfO2 é um excelente candidato devido a sua alta constante dielétrica mas tem apresentado problemas de estabilidade térmica sobre as superfícies de Si e Ge pois forma uma liga metálica de siliceto de háfnio em contato com o Si ou óxido de germânio em contato com o Ge. Essa tese descreve e discute os resultados de estudos sistemáticos de estabilidade térmica de filmes ultrafinos de HfO2 crescidos sobre as superfícies de Si3N4/Si nas direções cristalográficas (100) e (111) e variando as espessuras do filme de nitreto de silicio, o uso de nitreto de silício foi proposto para formar uma barreira física separando HfO2 do Si. Também foram realizados estudos de estabilidade térmica de filmes ultrafinos de HfO2 crescidos sobre as superfícies de Ge/Si(100) and Ge/Si(111), sendo que nesse caso o Ge foi crescido camada sobre camada usando o Sb como surfactante. As técnicas experimentais de XPS, ARPXS e LEED foram amplamente utilizadas e essenciais para a execução desse trabalho, especialmente em combinação com a fonte de radiação síncrotron do LNLS que permitiu a geração de espectros de alta resolução energética. Com os resultados desses trabalhos foi possível identificar uma espessura mínima do filme de Si3N4 de forma a possibilitar o seu uso como uma camada intermediária mantendo o sistema termicamente estável até 950 oC. As análises dos resultados de Ge também identificaram uma configuração termicamente estável, em especial o sistema HfO2/Ge/Si(111) não apresentou a formação da liga GeO2 durante o tratamento térmico, resultados estes atribuídos ao aumento na energia de formação do GeO2 causado pela diferença de empacotamento na direção (111) em relação a (100) / Abstract: The development of alternative high-k gate dielectrics for future complementary metal-oxide-semiconductor (CMOS) devices is indispensable in achieving both low leakage current and small equivalent oxide thickness. The thermal stability of these dielectrics on Si or Ge is a crucial issue to integrate them into CMOS, because standard device fabrication requires high temperature annealing, i.e. a dopant activation process (> 900 oC for Si and > 400 oC for Ge). HfO2 is one of the best candidates because of its high dielectric constant and high conduction band offset. On the other hand the formation of metallic Hf-silicide or GeO2 during the annealing process for activation is one of the most serious problems for Si-CMOS or Ge-CMOS, respectively. This thesis reports the results of a systematic study on the thermal stability of the HfO2 ultrathin films grown on Si3N4/Si, (100) and (111) surfaces, for different silicon nitride film thickness deposited by low energy nitrogen ion implantation technique. Also the thermal stability of HfO2 ultrathin films grown on Ge/Si(100) and Ge/Si(111) surfaces were studied as a function of annealing temperature. From these studies it was possible (1) to determine the minimum thickness of Si3N4 buffer layer to stabilize the HfO2 film up to 950 oC on top of the silicon surfaces and (2) to avoid the formation of GeO2 interlayer in the HfO2/Ge/Si(111) system probably because the crystallographic orientation of Si surface / Doutorado / Física / Doutor em Ciências

Orientador: Carlos Eduardo Angeli Furlani / Resumo: Visto que a demanda de produção de alimentos é crescente no mundo, surge a necessidade de se utilizar melhor os recursos disponíveis nas áreas de cultivo agrícola. O objetivo do estudo foi avaliar o efeito da interação entre declividades do terreno e exposição à radiação solar no desenvolvimento e produtividade da cultura do milho em cada uma das condições de superfície e, além disso, avaliar o índice de estresse hídrico da cultura. O experimento foi conduzido na safra 2018/2019 no município de Jaboticabal, SP, Brasil, na FCAV/UNESP, em estrutura que simula diferentes condições de exposições e declividades. No primeiro, o delineamento utilizado foi o inteiramente casualizado, em esquema 6x4 com cinco repetições, sendo seis declividades (0,10,20,30,40 e 50%) e quatro exposições (Norte, Sul, Leste e Oeste). Foram avaliados componentes fitotécnicos da cultura: altura e massa de matéria seca de planta, massa de mil grãos, produtividade. No segundo trabalho, foram utilizadas três declividades (0, 30 e 50%) e duas exposições (Norte e Sul). Após verificação da normalidade dos dados, usou-se análise de variância pelo Teste F e, quando necessário, aplicou-se o teste de Tukey (p<0,05) para comparação das médias. A exposição da cultura do milho influenciou no desenvolvimento das variáveis diâmetro do colmo, massa de grãos, número de fileiras por espiga e produtividade. O índice de estresse hídrico varia de acordo com a exposição a que as plantas estão submetidas aos raios solares. / Abstract: Since the demand for food production is growing in the world, there is a need to make better use of the resources available in agricultural cultivation areas. The objective of the study was to evaluate the effect of the interaction between land slopes and exposure to solar radiation on the development and productivity of the corn crop in each of the surface conditions and, in addition, to evaluate the water stress index of the crop. The experiment was conducted in the 2018/2019 harvest in the municipality of Jaboticabal, SP, Brazil, at FCAV / UNESP, in a structure that simulates different conditions of exposures and declivity. In the first, the design used was completely randomized, in a 6x4 scheme with five repetitions, six slopes (0.10,20,30,40 and 50%) and four exposures (North, South, East and West). Crop phytotechnical components were evaluated: height and dry matter of plant, mass of a thousand grains, productivity. In the second study, three slopes (0, 30 and 50%) and two exposures (North and South) were used. After verifying the normality of the data, analysis of variance was used by the F Test and, when necessary, the Tukey test (p <0.05) was applied to compare the means. The exposure of the corn crop influenced the development of the stem diameter, grain mass, number of rows per ear and productivity variables. The water stress index varies according to the exposure to which the plants are exposed to sunlight. / Mestre

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