A importância dos circuitos de moagem nos setores de mineração, pelotização e cimenteiro - seja por determinar o desempenho de processos subsequentes, seja por sua significativa parcela nos custos operacionais - encorajou o desenvolvimento de extensivos estudos na área. Dois campos continuam, contudo, pouco explorados: a moagem a seco e a moagem fina de concentrados (ou remoagem). Por outro lado, os circuitos de cominuição têm ganhado gradativamente mais importância ao longo dos anos para o mercado de minério de ferro, devido ao aprofundamento das cavas em operação e, por consequência, ao tratamento de minérios mais compactos e com menores teores de ferro. Por si só, essas novas características geraram a necessidade de moer produtos cada vez mais finos e de etapas adicionais de concentração e pelotização. Nesse ínterim, a moagem fina ganhou extrema importância. Este trabalho se concentrou no desenvolvimento de um método de ensaio de laboratório para a previsão do consumo específico de energia na etapa de remoagem a seco, adequado à aplicação em minérios de ferro itabiríticos. Foram investigadas diversas variáveis que podem interferir nos resultados de laboratório e definidas as melhores condições para os ensaios. Em seguida, os resultados dos ensaios foram confrontados com dados de uma operação de remoagem a seco industrial. O método proposto apresentou boa aproximação com os resultados industriais em relação à geração de finos (porcentagem passante em 45 ?m). Em relação à geração de área superficial - parâmetro importante para a pelotização -, os desvios foram maiores devido à sua correlação com a composição mineralógica para as misturas investigadas. Contudo, a relação entre a geração de área superficial com as diferentes mineralogias para o minério de ferro, especialmente o de Carajás, demanda maiores investigações. A relação linear proposta por Rittinger entre a geração de superfície e o consumo específico de energia na moagem também pode ser comprovada para a moagem a seco. / Studies on grinding area are vast due to its importance for mining, pelletizing and cement industry: grinding operations define both the throughput of following processes and operational costs. However, there are two grinding processes that lack deeper understanding: dry and fine grinding (re-grinding). On the other hand, as rich iron ore deposits get depleted and the necessity of treating more complex ores increases, the necessity of re-grinding concentrates prior further steps of concentration grows. Therefore, fine grinding of iron ores is progressively gaining importance. This study focused on the development of a bench scale test to predict the specific energy consumption of dry re-grinding circuits for iron ore. The variables that can affect grinding tests results were evaluated and the best conditions were defined. In sequence, the results of a series of lab tests were compared with data from an industrial circuit. The proposed test presented good correlation with industrial results regarding the generation of fines (percentage passing 0.045 mm). Regarding new surface generation - parameter of great importance for ore pelletizing - the differences between lab and industrial results were bigger, due the correlation of this parameter with the mineralogical composition of the samples investigated. However, the correlation between surface generation and mineralogical composition for iron ores, especially ores form Carajás complex, demands deeper investigations. Moreover, the linear relationship between energy consumption and surface area generation, as proposed by Rittinger was also observed for dry grinding.

Yes / The thermodynamic stability of caffeine (CA) cocrystals with dicarboxylic acids (DAs) as coformers was investigated in the presence of a range of structurally related dicarboxylic acids (SRDs). Two experimental conditions (slurry and dry-grinding) were studied for mixing the cocrystal and the SRD additive. The additives oxalic, malonic and glutaric acid led to the replacement of the acid coformer for certain cocrystals. Interestingly, a change in stoichiometry was observed for the CA:maleic acid system. A stability order among the cocrystals was established depending on their tendency to replace the coformer. To understand the factors controlling the relative stabilities, lattice energies were calculated using dispersion corrected Density Functional Theory (DFT). Gibbs free energy changes were calculated from experimental solubilities. The observed stability order corroborated well with lattice energy and Gibbs free energy computations.

Orientador: Eduardo Carlos Bianchi / Banca: Manoel Cleber de Sampaio Alves / Banca: Reginaldo Teixeira Coelho / O programa de Pós Graduação em Ciência e Tecnologia de Materiais PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Os materiais compósitos estão se tornando essenciais e amplamente utilizados na indústria moderna, principalmente nas indústrias aeronáuticas e aeroespacial. Essa notável demanda por este tipo de material, proveniente da junção entre dois ou mais materiais distintos, pode ser explicada pelo resultado alcançado com essa combinação: propriedades específicas e otimizadas para cada aplicação. Devido à anisotropia do material, há a tendência de aparecimento de tensões residuais ou distorções estruturais, após o seu processamento. Para o devido controle destas distorções, é imperativo o processo de usinagem denominado retificação. Nesse processo de usinagem, há a necessidade da utilização de grande quantidade de fluido de corte (refrigeração convencional). Referente a preocupações ambientais, surgem métodos que visam reduzir a utilização abundante de fluidos de corte, como: a refrigeração otimizada, a técnica de mínima quantidade de lubrificação (MQL) e a retificação a seco. O presente trabalho analisou os métodos de lubri-refrigeração citados, na retificação plana de compósitos plásticos reforçados com fibras de carbono (PRFC'S), como alternativas à retificação convencional, buscando mitigar o uso de fluidos de corte no meio industrial. Essa análise através da coleta de dados sobre a eficiência do processo e a qualidade superficial das peças, através das seguintes variáveis de saída: o comportamento de força tangencial de corte, rugosidade, energia específica, relação G (volume de material removido/volume de rebolo desgastado) e microscopia eletrônica de varredura (MEV). Com os resultados obtidos, verificou-se que a técnica de MQL gerou valores mais baixos de força tangencial de corte e energia específica de retificação. Já os métodos convencional e otimizado proporcionaram um menor desgaste da ferramenta de corte, bem como um melhor acabamento superficial / Abstract: Composite materials are becoming essential and largely used in modern industry, mainly is aeronautics and aerospace industries. This notable demand for these materials, generated from the combination of two or more distinct materials, can be explained by some results obtained: unique and optimized properties specific for each application. One of the main reasons for its large use it is their structural composition, which comes from the fusion of two different materials, resulting into excellent structural properties. Due to the material anisotropy, there is a trend of appering residual stresses and structural distortions, after its processing. For the adequade control of these distortions, it is necessary a machining process called grinding. When grinding these materials, there is a need of a great quantity of cutting fluids (conventional lubrication). In relation to the environmental concerns, new methodologies arise, which intend to reduce this large quantity of cutting fluid, like optimized cooling, the minimum quantity lubrification (MQL) technique and dry grinding. The present work analyzed the aforementioned lubri-cooling methods, on surface grinding of carbon fiber reinforced plastic composities (CFRP's), as alternatives to conventional cooling, in order to mitigate the deleterious effects of cutting fluids. This analysis was conducted through data gathering concerning the process efficiency and the the workpiece surface quality, using the following output variables: bahavior of the tangential force, surface roughness, specific grinding energy, G relation and scanning electron microscopy (SEM). With the results obtained, it can be verified that the MQL technique generated the lowest values of tangential cutting force and griding specific energy. The optimized and conventional methods provided the lowest wear of the grinding wheel, as well as the better surface finishing / Mestre

Made available in DSpace on 2014-06-11T19:30:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-10Bitstream added on 2014-06-13T18:47:32Z : No. of bitstreams: 1 varasquim_fmfa_me_bauru.pdf: 3736893 bytes, checksum: d77b1a71d89e0f0dfcd0ffcd80e0ad43 (MD5) / Os materiais compósitos estão se tornando essenciais e amplamente utilizados na indústria moderna, principalmente nas indústrias aeronáuticas e aeroespacial. Essa notável demanda por este tipo de material, proveniente da junção entre dois ou mais materiais distintos, pode ser explicada pelo resultado alcançado com essa combinação: propriedades específicas e otimizadas para cada aplicação. Devido à anisotropia do material, há a tendência de aparecimento de tensões residuais ou distorções estruturais, após o seu processamento. Para o devido controle destas distorções, é imperativo o processo de usinagem denominado retificação. Nesse processo de usinagem, há a necessidade da utilização de grande quantidade de fluido de corte (refrigeração convencional). Referente a preocupações ambientais, surgem métodos que visam reduzir a utilização abundante de fluidos de corte, como: a refrigeração otimizada, a técnica de mínima quantidade de lubrificação (MQL) e a retificação a seco. O presente trabalho analisou os métodos de lubri-refrigeração citados, na retificação plana de compósitos plásticos reforçados com fibras de carbono (PRFC'S), como alternativas à retificação convencional, buscando mitigar o uso de fluidos de corte no meio industrial. Essa análise através da coleta de dados sobre a eficiência do processo e a qualidade superficial das peças, através das seguintes variáveis de saída: o comportamento de força tangencial de corte, rugosidade, energia específica, relação G (volume de material removido/volume de rebolo desgastado) e microscopia eletrônica de varredura (MEV). Com os resultados obtidos, verificou-se que a técnica de MQL gerou valores mais baixos de força tangencial de corte e energia específica de retificação. Já os métodos convencional e otimizado proporcionaram um menor desgaste da ferramenta de corte, bem como um melhor acabamento superficial / Composite materials are becoming essential and largely used in modern industry, mainly is aeronautics and aerospace industries. This notable demand for these materials, generated from the combination of two or more distinct materials, can be explained by some results obtained: unique and optimized properties specific for each application. One of the main reasons for its large use it is their structural composition, which comes from the fusion of two different materials, resulting into excellent structural properties. Due to the material anisotropy, there is a trend of appering residual stresses and structural distortions, after its processing. For the adequade control of these distortions, it is necessary a machining process called grinding. When grinding these materials, there is a need of a great quantity of cutting fluids (conventional lubrication). In relation to the environmental concerns, new methodologies arise, which intend to reduce this large quantity of cutting fluid, like optimized cooling, the minimum quantity lubrification (MQL) technique and dry grinding. The present work analyzed the aforementioned lubri-cooling methods, on surface grinding of carbon fiber reinforced plastic composities (CFRP's), as alternatives to conventional cooling, in order to mitigate the deleterious effects of cutting fluids. This analysis was conducted through data gathering concerning the process efficiency and the the workpiece surface quality, using the following output variables: bahavior of the tangential force, surface roughness, specific grinding energy, G relation and scanning electron microscopy (SEM). With the results obtained, it can be verified that the MQL technique generated the lowest values of tangential cutting force and griding specific energy. The optimized and conventional methods provided the lowest wear of the grinding wheel, as well as the better surface finishing

The cutting links on chainsaws needs to be sharpened regularly to retain its sharpness. The most effective way is to use a machine wheel grinder. However, due to high friction there is a high risk of tempering the steel and damaging the sustainability to wear, resulting in a dull cutting edge. In order to develop a grinding method that produces a good result every time, a series of parameters were tested in order to determine which combination of these generated the best grinding results. With all parameters established the results shows that the attributes of each grinding wheel are the main parameter controlling the grinding result. This project investigates the attributes of different grinding wheels and their impact on grinding results. By comparing the energy each grinding wheel uses to perform the same amount of work, each grinding wheels suitability is rated based on its performance.   The calculations and the results from the analyses and tests show which of the grinding wheels performed the work with the lowest amount of increased energy.

Abstract Cellulose micro- and nanofibrils are elongated, flexible nano-scale particles produced from natural fibres with intensive mechanical treatments, usually in the form of dilute aqueous suspensions. Due to the recalcitrant structure of the fibres, mechanical, chemical and enzymatic pre-treatments are often used to loosen the fibre wall structure so as to facilitate the mechanical liberation of micro- and nanofibrils and reduce the high amount of mechanical energy needed. However, it is still unclear how different chemistries affect the disintegration phenomena and how mechanical action starts to unravel the fibre structure, and thus how micro- and nanofibrillation could best benefit from the pre-treatments. In addition, the high water content used in the process increases the production and transportation costs of the material, so that the solids content should be increased. Reducing the water content before or after production would be challenging, however, due to changes in fibre properties during drying (hornification) and the tendency for the resulting nanofibrils to agglomerate. Also, the effect of high solids content and temperature on the reduction of fibres to nano- and microfibrils is still not well understood. The aims of this work were to follow the changes in fibre morphology after mechanical, chemical and thermal modification and address their effects on the disintegration phenomena of the fibres to microfibrils. Mechanical compression-shearing, two selective oxidations and thermal drying in combination with TEMPO oxidation were used to modify the fibre structure before mechanical disintegration in a high-shear homogenizer or ball mill. The results showed that sufficient swelling of the fibre cell walls was a prerequisite for successful microfibrillation. Swelling can be promoted by loosening the hydrogen bonding network with compression and shearing forces or by increasing the charge density. Different charge thresholds were observed for microfibrillation depending on the chemistry used. Extremely hornified fibres were also successfully microfibrillated with the aid of TEMPO oxidation. Different fibre disintegration mechanisms were seen depending on the modification type and disintegration conditions. In addition, micro- and nanofibrils and nanocrystals were successfully produced under high solids (≥ 50%) conditions. / Tiivistelmä Luonnonkuiduista saatavat selluloosamikro- ja -nanofibrillit ovat pitkiä ja joustavia nanokokoluokan partikkeleita, joita valmistetaan yleensä intensiivisillä mekaanisilla käsittelyillä vesiliuoksissa. Kuitujen lujan rakenteen vuoksi valmistuksessa käytetään usein mekaanisia, kemiallisia ja entsymaattisia esikäsittelyjä heikentämään kuituseinämän tiivistä rakennetta, mikä helpottaa mikro- ja nanofibrillien irtoamista kuituseinämästä, sekä alentaa valmistuksen mekaanisen energian tarvetta. On kuitenkin edelleen epäselvää, miten erilaiset kemialliset käsittelyt vaikuttavat kuitujen hajoamiseen, miten kuiturakenne alkaa purkautua mekaanisessa käsittelyssä ja miten esikäsittelyillä voitaisiin parhaiten edistää mikro- ja nanofibrilloitumista. Valmistuksessa käytettävä korkea vesipitoisuus lisää mikro- ja nanofibrillien valmistus- ja kuljetuskustannuksia. Vesipitoisuuden alentaminen valmistuksessa tai sen jälkeen on kuitenkin haastavaa, sillä kuituominaisuudet muuttuvat kuivatuksessa ja valmiit nanofibrillit kimppuuntuvat helposti. Korkean kuiva-ainepitoisuuden ja lämpötilan vaikutusta kuidun hajoamiseen mikro- ja nanofibrilleiksi ei myöskään ymmärretä vielä täysin. Työn tarkoituksena oli tutkia sellukuitujen rakenteen muutoksia mekaanisen, kemiallisen ja lämpömuokkauksen seurauksena, sekä tutkia niiden vaikutusta kuidun purkautumiseen mikrofibrilleiksi. Kuiturakennetta muokattiin puristus-hiertomenetelmällä, kahdella selektiivisellä hapetusmenetelmällä, sekä lämpökuivauksen ja nk. TEMPO-hapetuksen yhdistelmällä ennen kuitujen mekaanista hajottamista joko leikkaavassa homogenisaattorissa tai kuulamyllyssä. Tulosten perusteella riittävä kuituseinämän turvottaminen oli edellytys onnistuneelle mikrofibrilloinnille. Turpoamista saatiin edistettyä hajottamalla kuiduissa olevia vetysidosverkostoja puristus- ja leikkausvoimilla tai kasvattamalla anionisen varauksen määrää kuiduissa. Varauksen kynnysarvo mikrofibrilloitumiselle riippui käytetystä hapetusmenetelmästä. Myös kuivatuksessa erittäin sarveistuneet kuidut saatiin mikrofibrilloitua TEMPO-hapetuksen avulla. Tulosten perusteella kuiduilla on erilaisia hajoamismekanismeja, jotka riippuvat käytetystä muokkauksesta, sen intensiivisyydestä, sekä hajottamisolosuhteista. Työssä onnistuttiin myös valmistamaan mikro- ja nanofibrillejä, sekä nanokiteitä tavanomaista huomattavasti korkeammassa (≥50 %) kuiva-ainepitoisuudessa.

The application of chemical additives, known as grinding aids (GA), dates back to 1930 in the cement industry. As opposed to the cement industry, where the use of GAs is on the final processing step, it could be one of the first process steps in ore beneficiation. A few investigations addressed the GA applications in ore dressing; therefore, further studies are required to better understand the GA effects on the product properties and downstream separation processes. This thesis undertakes a comparative study on the dry grinding of magnetite and the resulting product characteristics with and without GAs. The main aim is to reduce energy consumption and to address some of the challenges associated with dry processing.  The effects of GAs on the dry batch ball milling of magnetite were examined to analyze the energy consumption (Ec), particle size distribution, flow properties, bulk properties, surface morphology, particle fineness, and surface chemistry of products. Their effects on the ground product were systematically explored by sieve analysis, powder rheology, BET surface measurements, optical microscopy analysis, and zeta potential measurements. Compared with the absence of GAs, the dry grinding efficiency of magnetite increased after using GAs; however, an optimal dosage exists based on the GA type. Among GAs which considered in this investigation (Zalta™ GR20-587 (Commercial GA) and Zalta™ VM1122 (Commercial viscosity aid) as well as sodium hydroxide), Zalta™ VM1122, a polysaccharide-based additive, was the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t. The PSD became narrower and finer (P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. In general, the results reveal that at sufficient GA dosages, they reduce the average particle size, increase the specific surface area, and narrow the particle size distribution. However, an excessive amount of GAs could be detrimental to the grinding performance.  Further studies on powder rheology indicated that the used GAs resulted in improved material flowability compared to grinding without additives (in the examined dosage range). The rheology measurements by the FT4 Powder Rheometer showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding. There was a strong correlation between the grinding parameters and flow parameters (r > 0.93). These results confirmed the effect of GA on ground particles' flowability. Zalta™ VM1122 showed the best performance with 38.8% reduction of basic flow energy, 20.4 % reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. The present investigation showed that the predominant mechanism of GAs is based on the alteration of rheological properties. Further investigation on the surface properties showed that using GAs could increase the surface roughness, which is beneficial for downstream processes such as froth flotation. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects from the optical microscope images. Furthermore, Zalta™ VM1122 (non-ionic) resulted in similar zeta potentials and pH values for the product compared to experiments without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes. / Kolarctic CBC (KO1030 SEESIMA)