ASPECTOS GEOLÓGICOS, PETROGRÁFICOS E QUÍMICOS DE INTERESSE PARA O APROVEITAMENTO ECONÔMICO DOS QUARTZITOS FOLIADOS DE SÃO THOMÉ DAS LETRAS – MINAS GERAIS

A região de São Thomé das Letras constitui o maior centro brasileiro de lavra de quartzitos foliados, com produção atual estimada em 250.000 t/ano. O baixo índice de recuperação decorrente das atividades de lavra destes quartzitos, estimada como inferiores a 20% do total extraído, estariam gerando cerca de 1.250.000 t/ano de rejeitos, o que tem se traduzido em grandes pilhas de bota-fora com evidentes desdobramentos ambientais indesejáveis. Objetivando a adequação ambiental da lavra, a Fundação Estadual do Meio Ambiente de Minas Gerais - FEAM iniciou, a partir do ano de 1993, trabalhos de fiscalização e orientação da atividade extrativa de quartzitos no Município de São Thomé das Letras. A partir de 1996, esses trabalhos foram ampliados através do Projeto Minas Ambiente - Mineração de Pedra São Tomé que, sob a coordenação da FEAM, promoveu estudos para disposição controlada e aproveitamento econômico de resíduos, revegetação das pilhas de bota-fora e técnicas menos impactantes de desmonte na lavra. Neste contexto, os estudos geológicos, petrográficos e químicos ora realizados visam contribuir com aspectos de interesse para as atividades extrativas e de aproveitamento industrial dos rejeitos da lavra e do beneficiamento dos quartzitos foliados São Tomé. Trabalhos desenvolvidos no âmbito do Projeto Minas Ambiente e, mais recentemente, pela Universidade Vale do Rio Verde de Três Corações demonstraram a viabilidade técnica de utilização dos quartzitos para elaboração de tijolos prensados e autoclavados. Algumas variedades de quartzitos também estão sendo aproveitadas na produção de vidrados e esmaltes cerâmicos, inclusive com vantagens técnicas e econômicas bastante competitivas sobre matérias-primas oriundas de sedimentos aluvionares. Outros usos para os quartzitos moídos, como carga mineral, material filtrante e argamassas em geral, estão em fase de estudos pelos mineradores e deverão ser brevemente viabilizados, o que permite vislumbrar, pelo menos a médio prazo, um expressivo incremento dos usos industriais para os quartzitos São Tomé. Palavras-chave: rocha ornamental; rocha de revestimento; quartzito laminado; recuperação de rejeito; quartzito São Tomé.

Proposta para melhoria da qualidade dos produtos cerâmicos e de criação de um polo cerâmico artesanal na cidade de Indiana - SP

This work presents a proposal to create a Polo Ceramic Craft in the town of Indiana - SP, through the potter’s organization in a cooperative that will coordinate activities to add value to ceramic pieces. To achieve this, two things are essential: improving the ceramic body and improve the properties of the ceramic material. For the first action it’s necessary to create a Central Mass Production of Ceramics, to provide raw materials and homogeneous composition that results in differentiated ceramic after burning process (sintering). To this end, we propose the incorporation of additives (which act as fluxes) to the clay material. These additives can be mineral such as feldspar and nefelinas or leavings, such as glass powder obtained from disposable containers. For the second action is necessary to acquire an oven, electric or gas, it reaches higher temperatures (around 1200 ° C). The presence of the additive and burning at higher temperatures will enable better production of sintered ceramic material with less porosity and water absorption and higher mechanical strength, and pieces vitrified and glazed, allowing them to assign a higher value. For the production of these materials (thinner walls) requires a smaller volume of clayey raw materials. Besides benefiting the ceramic pieces, the proposed changes reduce the environmental impact caused by burning wood, since it will be replaced by natural gas (or electricity), and even will reduce the disposal of glass containers in the environment by recycling and incorporating this material in the clay. From a social standpoint, the cooperative is crucial to the viability of the proposed project, to coordinate activities and commercial production, which will result in better wages and profits for companies and consequently for the city and its population

Vitrocerâmicas para blindagens balísticas

The use of ceramic materials in ballistic armor is considerable. Such materials can be very harder and lighter than metallic materials commonly used and it presents advantages to replace metallic materials when necessary toughness can be achieved. However, as SiC and Al2O3 ceramic, traditionally used for shielding, still have high manufacturing cost or low density do not have enough to shield applications such as aircraft. An alternative is the glass-ceramics, ceramics obtained by controlled crystallization of glasses, whose properties can be adjusted by choosing the chemical composition of glass, heat treatment of crystallization and special treatments such as ion exchange on the surface, resulting in increased mechanical strength . The objective of this project is to study the kinetics of crystallization of a glass composition based on cordierite (2MgO.2Al2O3.5SiO2), low density and high hardness, for the manufacture of glass-ceramics for ballistic tests. Shown in this report are results of heat treatment of crystallization and characterization by thermal analysis (DSC) glass obtained previously, indicating uneven distribution of crystals, and drying, weighing, mixing of raw materials and a new fusion of glass, the same composition

Strategies to improve the mechanical properties of starch-based materials: plasticization and natural fibers reinforcement

Biodegradable polymers are starting to be introduced as raw materials in the food-packaging market. Nevertheless, their price is very high. Starch, a fully biodegradable and bioderived polymer is a very interesting alternative due to its very low price. However, the use of starch as the polymer matrix for the production of rigid food packaging, such as trays, is limited due to its poor mechanical properties, high hidrophilicity and high density. This work presents two strategies to overcome the poor mechanical properties of starch. First, the plasticization of starch with several amounts of glycerol to produce thermoplastic starch (TPS) and second, the production of biocomposites by reinforcing TPS with promising fibers, such as barley straw and grape waste. The mechanical properties obtained are compared with the values predicted by models used in the field of composites; law of mixtures, Kerner-Nielsen and Halpin-Tsai. To evaluate if the materials developed are suitable for the production of food-packaging trays, the TPS-based materials with better mechanical properties were compared with commercial grades of oil-based polymers, polypropylene (PP) and polyethylene-terphthalate (PET), and a biodegradable polymer, polylactic acid (PLA).

Relationship between elastic and mechanical properties of dental ceramics and their index of brittleness

The purpose of the study was to verify the effects of a number of materials' parameters (crystalline content; Young's modulus, E; biaxial flexure strength, sigma(i); Vickers hardness, VH; fracture toughness, K-Ic; fracture surface energy, gamma(f); and index of brittleness, B) on the brittleness of dental ceramics. Five commercial dental ceramics with different contents of glass phase and crystalline particles were studied: a vitreous porcelain (VM7/V), a porcelain with 16 vol% leucite particles (d.Sign/D), a glass-ceramic with 29 vol% leucite particles (Empress/E1), a glass-ceramic with 58 vol% lithium-disilicate needle-like particles (Empress 2/E2), and a glass-infiltrated alumina composite with 65 vol% crystals (In-Ceram Alumina/IC). Discs were constructed according to manufacturers' instructions, ground and polished to final dimensions (12 mm x 1.1 mm). Elastic constants were determined by ultrasonic pulse-echo method. sigma(i) was determined by piston-on-3-balls method in inert condition. VH was determined using 19.6 N load and K-Ic was determined by indentation strength method. gamma(f) was calculated from the Griffith-Irwin relation and B by the ratio of HV to K-Ic. IC and E2 showed higher values of sigma(i), E, K-Ic and gamma(f), and lower values of B compared to leucite-based glass-ceramic and porcelains. Positive correlations were observed for sigma(i) versus K-Ic, and K-Ic versus E-1/2, however, E did not show relationship with HV and B. The increase of crystalline phase content is beneficial to decrease the brittleness of dental ceramics by means of both an increase in fracture surface energy and a lowering in index of brittleness. (C) 2012 Elsevier Ltd and Techna Group Sri. All rights reserved.

Biomimetic Materials for Biomedical Applications

Objects with complex shape and functions have always attracted attention and interest. The morphological diversity and complexity of naturally occurring forms and patterns have been a motivation for humans to copy and adopt ideas from Nature to achieve functional, aesthetic and social value. Biomimetics is addressed to the design and development of new synthetic materials using strategies adopted by living organisms to produce biological materials. In particular, biomineralized tissues are often sophisticate composite materials, in which the components and the interfaces between them have been defined and optimized, and that present unusual and optimal chemical-physical, morphological and mechanical properties. Moreover, biominerals are generally produced by easily traceable raw materials, in aqueous media and at room pressure and temperature, that is through cheap process and materials. Thus, it is not surprising that the idea to mimic those strategies proper of Nature has been employed in several areas of applied sciences, such as for the preparation of liquid crystals, ceramic thin films computer switches and many other advanced materials. On this basis, this PhD thesis is focused on the investigation of the interaction of biologically active ions and molecules with calcium phosphates with the aim to develop new materials for the substitution and repair of skeletal tissue, according to the following lines: I. Modified calcium phosphates. A relevant part of this PhD thesis has been addressed to study the interaction of Strontium with calcium phosphates. It was demonstrated that strontium ion can substitute for calcium into hydroxyapatite, causing appreciable structural and morphological modifications. The detailed structural analysis carried out on the nanocrystals at different strontium content provided new insight into its interaction with the structure of hydroxyapatite. At variance with the behaviour of Sr towards HA, it was found that this ion inhibits the synthesis of octacalcium phosphate. However, it can substitute for calcium in this structure up to 15 atom %, in agreement with the increase of the cell parameters observed on increasing ion concentration. A similar behaviour was found for Magnesium ion, whereas Manganese inhibits the synthesis of octacalcium phosphate and it promotes the precipitation of dicalcium phosphate dehydrate. It was also found that Strontium affects the kinetics of the reaction of hydrolysis of α-TCP. It inhibits the conversion from α-TCP to hydroxyapatite. However, the resulting apatitic phase contains significant amounts of Sr2+ suggesting that the addition of Sr2+ to the composition of α-TCP bone cements could be successfully exploited for its local delivery in bone defects. The hydrolysis of α-TCP has been investigated also in the presence of increasing amounts of gelatin: the results indicated that this biopolymer accelerates the hydrolysis reaction and promotes the conversion of α-TCP into OCP, suggesting that its addition in the composition of calcium phosphate cements can be employed to modulate the OCP/HA ratio, and as a consequence the solubility, of the set cement. II. Deposition of modified calcium phosphates on metallic substrates. Coating with a thin film of calcium phosphates is frequently applied on the surface of metallic implants in order to combine the high mechanical strength of the metal with the excellent bioactivity of the calcium phosphates surface layers. During this PhD thesis, thank to the collaboration with prof. I.N. Mihailescu, head of the Laser-Surface-Plasma Interactions Laboratory (National Institute for Lasers, Plasma and Radiation Physics – Laser Department, Bucharest) Pulsed Laser Deposition has been successfully applied to deposit thin films of Sr substituted HA on Titanium substrates. The synthesized coatings displayed a uniform Sr distribution, a granular surface and a good degree of crystallinity which slightly decreased on increasing Sr content. The results of in vitro tests carried out on osteoblast-like and osteoclast cells suggested that the presence of Sr in HA thin films can enhance the positive effect of HA coatings on osteointegration and bone regeneration, and prevent undesirable bone resorption. The possibility to introduce an active molecule in the implant site was explored using Matrix Assisted Pulsed Laser Evaporation to deposit hydroxyapatite nanocrystals at different content of alendronate, a bisphosphonate widely employed in the treatments of pathological diseases associated to bone loss. The coatings displayed a good degree of crystallinity, and the results of in vitro tests indicated that alendronate promotes proliferation and differentiation of osteoblasts even when incorporated into hydroxyapatite. III. Synthesis of drug carriers with a delayed release modulated by a calcium phosphate coating. A core-shell system for modulated drug delivery and release has been developed through optimization of the experimental conditions to cover gelatin microspheres with a uniform layer of calcium phosphate. The kinetics of the release from uncoated and coated microspheres was investigated using aspirin as a model drug. It was shown that the presence of the calcium phosphate shell delays the release of aspirin and allows to modulate its action.

Cytotoxicity evaluation of polymer-derived ceramics for pacemaker electrode applications.

Ceramics are known to be chemically stable, and the possibility to electrically dope polymer-derived ceramics makes it a material of interest for implantable electrode applications. We investigated cytotoxic characteristics of four polymer-derived ceramic candidates with either electrically conductive or insulating properties. Cytotoxicity was assessed by culturing C2C12 myoblast cells under two conditions: by exposing them to material extracts and by putting them directly in contact with material samples. Cell spreading was optically evaluated by comparing microscope observations immediately after the materials insertion and after 24 h culturing. Cell viability (MTT) and mortality (LDH) were quantified after 24-h incubation in contact with the materials. Comparison was made with biocompatible positive references (alumina, platinum, biocompatible stainless steel 1.4435), negative references (latex, stainless steel 1.4301) and controls (no material present in the culture wells). We found that the cytotoxic properties of tested ceramics are comparable to established reference materials. These ceramics, which are reported to be very stable, can be microstructured and electrically doped to a wide range of conductivity and are thus excellent candidates for implantable electrode applications including pacemakers.

Tecnología cerámica : estudios experimentales sobre la cerámica del sitio arqueológico San Ignacio (Noroeste de Mendoza)

El propósito de este trabajo es explorar la disponibilidad de materias primas que pudieron ser utilizadas en el proceso de manufactura de la cerámica gris del sitio arqueológico San Ignacio, en el Valle de Potrerillos, ubicado al Norte de la provincia de Mendoza (640 dC). Se pretende, además, reproducir las técnicas de producción y cocción cerámica, a fin de obtener un producto de características análogas a las de la colección estudiada. La metodología utilizada presentó las siguientes etapas: recolección de materiales arcillosos; caracterización de las propiedades físicas en estado crudo; análisis químicos; desarrollo experimental de cocción y ensayos post-cocción de los mismos. Los productos obtenidos muestran una buena estructura y sinterización, aunque no se logró una atmósfera completamente reductora con este tipo de combustible.

Repercusión medioambiental del uso de la cerámica estructural en España. Energía embebida y huella de carbono

La producción y el transporte a obra de los productos cerámicos de carácter estructural suponen un importante consumo energético, que conlleva la emisión de gases de efecto invernadero a la atmósfera. El objetivo de la presente Tesis es demostrar la existencia de importantes diferencias en el valor del impacto ambiental asociado a los productos de cerámica estructural fabricados en España, y que estas diferencias podrían quedar cuantificadas y reflejadas mediante un análisis de Huella de Carbono y de la Energía Embebida. Se parte de la inexistencia en España, de base de datos contrastada y consensuada, que establezca las cargas medioambientales en función del tipo de producto cerámico a utilizar. Se realiza en la primera parte del estudio una revisión del estado actual de la Huella de Carbono y la Energía Embebida en el campo de los materiales de construcción, y más concretamente en el sector de la cerámica estructural, que sirve para acotar los límites del estudio y justificar el objeto de la Tesis. La investigación se acota a las etapas de producción y transporte a obra de los productos (estudio cuna a puerta con opciones), al considerar que son éstas, a priori, las que tienen una mayor incidencia en el comportamiento ambiental del producto. Siguiendo los pasos definidos en la normativa aplicable (definición del mapa de procesos – límites y alcance – inventario – cálculo y evaluación), se establece un método específico de identificación y cuantificación de las variables que determinan la Huella de Carbono y Energía Embebida de los productos cerámicos, en función de la tipología de producto. La información necesaria (inventario) se obtiene principalmente con recogida de datos “in situ” de fábricas de productos cerámicos, lo que garantiza que la información tratada en este estudio es de primer nivel. La información se complementa/contrasta con fuentes bibliográficas. Se determinan 6 variables con influencia global en el impacto ambiental, 44 variables principales y 39 secundarias, estableciendo las fórmulas de cálculo a partir de dichas variables. Los resultados de cálculo y evaluación determinan que, para unas mismas condiciones de fabricación, las diferencias entre productos cerámicos llegan hasta un 27% para la Huella de Carbono y un 35% para Energía Embebida. La relevancia que alcanza el impacto asociado al transporte del producto a obra puede llegar hasta un 40% del total. El método de cálculo y las fórmulas desarrolladas se integran en una hoja de cálculo, para el cálculo de Huella de Carbono y Energía Embebida de los productos cerámicos, que permite, a su vez, conocer la repercusión medioambiental que tiene la introducción de modificaciones o innovaciones en el proceso de producción o transporte a obra. Así mismo, el trabajo desarrollado ha servido para poner en relieve una serie de problemas y falta de información en el campo de la cerámica estructural y el medioambiente que pueden ser objeto de futuras líneas de investigación, tanto para el sector de la edificación como para la comunidad científica, pudiendo implementar la metodología desarrollada en otras investigaciones. Se considera que la investigación realizada y sus resultados suponen una aportación importante para conocer y reducir el impacto ambiental de los edificios, desde la perspectiva del ciclo de vida y considerando que el impacto ambiental de un edificio comienza desde el momento en que se extraen las materias primas para la fabricación de los materiales con los que se construyen los edificios. ABSTRACT The production and transport of structural ceramic products involves an important energy consumption, which leads to the emission of greenhouse gases into the atmosphere. The objective of the research is to demonstrate the existence of significant differences in the value of the environmental impact of structural ceramic products manufactured in Spain, and these differences could be quantified by the Carbon Footprint and Embodied Energy. It starts from the absence in Spain, of contrasted and agreed databases that establish the environmental loads depending on the type of ceramic product. In the first part of the study reviews the current state of the Carbon Footprint and Embedded Energy in the field of building materials, and more specifically in the field of structural ceramics, which serves to limit the scope of the study and justify the purpose of this Thesis. The Research is bounded to production and transportation stages of (cradle to gate with options), considering they are the stages that have a greater impact on the environmental performance of the product. Following the steps defined in applicable rules (definition of process map - boundaries and scope – inventory analysis- calculation and impact assessment), it sets a specific method for the identification and quantification of the variables that determine the Carbon Footprint and Embedded Energy of structural ceramic products, depending on the type of product. The information (inventory) is given mainly with a data collection in ceramic factories (and in a consultation with the manufactures of the products), ensuring that the information handled in this Thesis is a first rate data. It is established 6 variables with a global influence in the environmental impact, 44 primary and 39 secondary variables, establishing calculation formula from these variables. The results of calculation and assessment determined that, for same manufacturing conditions, the differences between ceramic products reach 27% for Carbon Footprint and 35% for Embodied Energy. The relevance that reaches the impact of transport can reach 40% of the total. The method of calculation and formulas developed are integrated into a simple calculation tool, excel base, to calculate the Carbon Footprint and Embodied Energy of structural ceramic products, which allows, know the environmental impact of changes or innovations in the production process or transport to work. The work also has served to find a problems and gaps in the field of structural ceramics and the environment that may well be the subject of future research, both for the building sector to the scientific community, implementing the methodology developed in other research. It is considered that the research and its results represent an important contribution to understand and reduce the environmental impact of buildings from the perspective of the life cycle, considering that the environmental impact of a building starts from the time that the raw materials are extracted for the manufacture of building materials.

Induced polarization : a study of its causes and magnitudes in geologic materials, final report /

"Final report for U.S. Atomic Energy Commission, Division of Raw Materials Contract AT-(05-1)-718."

Controlled materials plan, consumer allotment accounting manual. February 26, 1943.

At head of title: War production board.

Materials shortages : hearings before the Permanent Subcommittee on Investigations of the Committee on Government Operations, United States Senate, Ninety-third Congress, second session, pursuant to section 4, Senate resolution 269, 93d Congress.

Hearings held Sept. 11-Dec. 17, 1974.

Synthesis, characterization, and electrical conduction of 10 mol% Dy2O3 doped CeO2 ceramics

Well-densified 10 mol% Dy2O3-doped CeO2 (20DDC) ceramics with average grain sizes of similar to 0.12-1.5 mu m were fabricated by pressureless sintering at 950-1550 degrees C using a reactive powder thermally decomposed from a carbonate precursor, which was synthesized via a carbonate coprecipitation method employing nitrates as the starting salts and ammonium carbonate as the precipitant. Electrical conductivity of the ceramics, measured by the dc three-point impedance method, shows a V-shape curve against the average grain size. The sample with the smallest grain size of 0.12 mu m exhibits a high conductivity of similar to 10(-1.74) S/cm at the measurement temperature of 700 degrees C, which is about the same conduction level of the micro-grained 10 mol% Sm2O3- or Gd2O3-doped CeO2, two leading electrolyte materials. (c) 2004 Elsevier Ltd. All rights reserved.

ICP-MS Trace Element Analysis of Song Dynasty Porcelains from Ding, Jiexiu and Guantai kilns, North China

Bodies of Ding kiln white porcelains and their imitations from Guantai and Jiexiu kilns of the Chinese Song dynasty (960-1279 AD) were analysed for 40 trace elements by inductively coupled plasma mass spectrometry (ICP-MS). Numerous trace element compositions and ratios allow these visually similar products to be distinguished, and a Ding-style shard of uncertain origin is identified as a likely genuine Ding product. In Jiexiu kiln, Ding-style products have trace element features distinctive from blackwares of an inferior quality intended for the lower end market. Based on geochemical behaviour of these trace elements, we propose that geochemically distinctive raw materials were used for Ding-style products of a higher quality, which possibly also underwent purification by levigation prior to use. Capable of analysing over 40 elements with a typical long term precision of < 2%, this high precision ICP-MS method proves to be very powerful for grouping and characterising archaeological ceramics. Combined with geochemical interpretation, it can provide insights into the raw materials and techniques used by ancient potters. (C) 2004 Elsevier Ltd. All rights reserved.

Some aspects of the microbiological properties of polymers and composite materials

The interaction of microorganisms with glass-reinforced polyester resins(GRP), both under laboratory and simulated operating conditions, has been examined following reports of severl! fungal biodeterioration. Although GRP was not previously associated with substantial microbial growth, small amounts of microbial activity would pose problems for products associated with comestible materials. The microbiology of the raw materials was investigated, two ingredients were supportive to microbial populations whilst five materials were biostatic or inhibitory in their action. Production laminate was not susceptible to microbial deterioration or inhibitory to microbes. Incorporation of zinc stearate, one of the supportive ingredients, at 300% manufacturing level or drastic undercuring produced laminate capable of supporting microbial growth but only after a non-biotic stage of degradation. Study of the long-term population dynamics of cisterns of GRP and competitive materials under conditions simulating in-service conditions, monitoring microbial numbers within the experimental vessels and comparing with the populations of the supply water, suggests that the performance of GRP cisterns is slightly superior to conventional competitive materials. An investigation of the biological performance of GRP cisterns in an isolated area of known microbiological hazard was conducted. Severe biodeterioration had been experienced with Preform GRP articles moulded using different production techniques, but substitution of current GRP articles resulted in no recurrence of the problem. All attempts to establish the fungal isolate responsible for the phenomena in cisterns under controlled conditions failed. Scanning Electron Microscopy of GRP surfaces showed that although differences exist between current and Preform laminates, these could not satisfactorily explain the differences in service behaviour. These results and the results of the British Plastics Federation Expert Working Group interlaboratory study are discussed in relation to the original report of gross fungal biodeterioration and, to the design of future testing programmes for the products of industrial concerns.