As some companies in the paper industry struggle to shift from commodity grades to value added products, technical challenges and opportunities have grown tremendously. These new products require more stringent manufacturing specifications and improved performance relative to those of lignocellulosic fibers currently being produced. Hence, topochemical and mechanical modifications of pulp fibers have moved to the forefront of many corporate strategies. Researchers are beginning to develop new tools to help better understand the fundamental mechanisms of fiber modifications and how to most efficiently apply them. Two novel approaches are presented. First, a new method to observe single fiber crossings is developed. It was found that refining reduces the stepheight in the fiber crossing for both hardwood and softwood kraft pulps by increasing the tendency of the fibers to collapse, deform, and assume a lens like shape. The effect of pulp type, bleaching, drying, wet pressing, and fiber charge were also investigated. Graphs of stepheight versus freespan were linear through the origin suggesting that the freespan (flexibility) of the crossing fiber is largely unimportant to the formation of fiber crossings. Quite surprisingly, the ratio of stepheight to freespan remained relatively constant no matter the treatment. Only bleaching and the addition of surface charge via CMC had any independent impact on freespan. The data do not fit bending or shear mechanisms that have been developed in the literature suggesting that another mechanism may be responsible for the deformation behavior of single fiber crossings. Also, a method employing fluorescence microscopy and fluorescence resonance energy transfer is used to image the areas of a fiber-fiber interface while they were bonded. Analysis of the FRET signal from fiber crossings indicate that wet pressing increased the FRET occurring between the two dyed fiber surfaces. The results are consistent with the increased amount of interdiffusion expected with higher levels of wet pressing. Two novel techniques are used to investigate fundamental aspects of fiber deformation behavior and fiber-fiber bond formation. As these methods are further refined and utilized they will provide new avenues for researchers to explore and expand the property space of fibers and paper sheets.

The structure and properties of chemical vapor deposited zinc sulfide (CVD ZnS) were assessed before and after heat treatments, involving different annealing and hot isostatic pressing (HIPing) profiles. Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder x-ray diffraction, x-ray chemical microanalysis, photoluminescence, ultraviolet through longwave infrared transmission, and mechanical testing. Before heat treatment, CVD ZnS consists of lamellar twinned structures in 10 to 100 nm layers aggregated into domains which compose grains typically 5 to 10 μm in diameter with an overall crystallographic texture on the {100} planes. The scattering behavior of CVD ZnS was investigated and described by a surface scattering model based on internal surface roughness and refractive index variations due to onedimensional stacking disorder. The two to five percent hexagonality measured by x-ray diffraction is believed to form due to oxygen impurities at the twin boundaries which cause nanostructural polytypism and result in differential refractive index and scattering. CVD ZnS variants in low temperature deposited red ZnS and sulfur precursor elemental ZnS are examined as well. Color in CVD ZnS is believed to be due to band edge position, probably due to oxygen content, and not directly related to the hydride absorption at 6 μm. After annealing or hot isostatic pressing above 850 °C for sufficient time, CVD ZnS recrystallizes and becomes strongly textured on the {111} planes. This recrystallization is required to remove stacking disorder, resulting in a structure with less than half a percent hexagonality and low visible scattering. The recrystallization is believed to proceed by diffusing the oxygen at the nano-twin boundaries back into the lattice, thus unpinning the boundaries and allowing them to move and grow into the tabular recrystallized morphology by polytype induced exaggerated grain growth. The presence of active metals like platinum, silver, copper, or nickel during hot isostatic pressing causes a reaction with sulfur and lowers the temperature required for recrystallization. The optical scattering model is consistent in describing standard CVD ZnS, elemental ZnS, and multispectral recrystallized ZnS as having successively lower birefringence at internal surfaces.

Currently, there is a high demand for lightweight aerospace materials, driven by the desire to provide enhanced fuel efficiency by reducing vehicular weight. Aluminum alloys are attractive due to their excellent mechanical properties and high strength to weight ratios. Powder metallurgy (PM), which converts metal powder into a high performance product, presents an alternative to traditional forming techniques, which are often unable to provide adequate dimensional tolerances. The challenge is to determine if aluminum PM alloys and technologies can be successfully employed within aerospace applications. This research focuses on the PM processing technologies (die compaction, cold isostatic pressing (CIP), and spark plasma sintering (SPS)) of two alloys, PM2024 and PM7075. Processing parameters were assessed using attributes such as density, hardness, and tensile properties. Both powders showed comparable densities and tensile properties to their wrought equivalents. Ultimately, the groundwork was laid for future research into these alloys and their processing methods.

The actual industrial development linked to the financial situation over the world lead automotive and other companies to expand their production level to stay competitive. Changing an organization to raise its production or profit is not a one day journey, but requires some steps. Tools exist to develop the production level of manufacturing industry since more or less the fifties, and the continuous improvement is measured by some available and famous indicators around lean manufacturing mainly. Pressing equipment especially like a metal stamping press expressed through the following case study can be improved by respecting some fundamentals. Lean manufacturing aspects as 5 S’s and TPM (Total Productive Maintenance) for example are tools that can be applied to improve the production rate of a stamping press. To even better improve the OEE (Overall Equipment Effectiveness) of the same machine, a tool like SMED (Single Minute Exchange of Dies) reveals to be really powerful when improving the global output rate of the machine. The case study developed inside this present report aims to investigate all the possibilities to improve the OEE of pressing equipment facing theoretical aspects and reality issues. The tools involved are part of the content, but the way to support a company for the organizational change required to the success is another part of the content. Technical solutions are taking part of the outcome, and a strong link to change management is included. Correlation between both technical and managerial aspects is the main line followed to get the final results. An experimental and actual OEE is calculated, and improved following a rating according to the possible improvements. Those results are analyzed to provide a weighted feedback related to the whole research.

Al-Si based alloys are commonly used in the automobile industry due to their superior properties, high strength to weight ratio, corrosion resistance, recyclability, etc. These alloys are fabricated by casting and powder metallurgy techniques in which porosity is a common feature. The presence of pores is accompanied by a decrease in mechanical properties, i.e., a drop in hardness and ductility of the materials. In the present study, an attempt was made to understand the effect of surface porosity on the tribological property. A380M and Al-6wt% Si alloys were used to prepare specimens containing 2.6 to 6.9% porosity via casting and 1 to 6.7% porosity via powder metallurgy techniques, respectively. Dry sliding wear behavior was investigated in the load range 6-20 N against an AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration at a frequency range of 4-20 Hz for cast and 15 Hz for P/M samples.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 66-71). Also available in electronic format on the Internet.

Thesis (Ph. D)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Viola L. Acoff, Krishan K. Chawla, Raymond J. Donahue, Gregg M. Janowski, Harry E. Littleton (ad hoc). Includes bibliographical references (p. 143-138).

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Orientador: Luiz Eduardo de Angelo Sanchez / Banca: Carlos Alberto Fortulan / Banca: Gilberto de Magalhães Bento Gonçalves / Resumo: A usinagem de cerâmicas avançadas geralmente é feita com o objetivo de corrigir as deformações após a etapa de sinterização, conferir precisão dimensional e qualidade superficial. Para cumprir esta tarefa é utilizada, principalmente, a retificação com rebolo de diamante sob baixas taxas de remoção de material. O torneamento com ferramenta de diamante pode ser aplicado para a maioria das cerâmicas, mas esbarram em condições limites de remoção de material, como profundidade de corte nanamétricas, que se ultrapassadas mudam o regime de remoção de dúctil para frágil. Uma alternativa é a usinagem da peça no estado verde, a qual apresenta fácil usinagem com a diminuição da introdução de defeitos prejudiciais à resistência mecânica. Após a sinterização invariavelmente ocorrem distorções devido à distribuição heterogênea de gradientes de densidade que se localizam nas porções mais externas do compactado. Na tentativa de remover estes gradientes, o presente trabalho analisou a influência da remoção de sobrematerial no estado verde na distorção da peça após a sinterização. Corpos-de-prova de alumina, com 99,8% de pureza, foram torneados com sobremateriais de 1,0, 2,0 3,0, 4,0 e 5,0 mm por uma ferramenta de metal duro sob condições constantes de usinagem. Além da distorção, outras variáveis de saída foram analisadas, com desgaste de ferramenta, força de corte (Fc) e rugosidade média aritmética (Ra) do compactado em verde e sinterizado. Os resultados apontam uma redução da distorção da peça sinterizada de até 81,4% com o maior valor de remoção de sobrematerial em verde e a influência do desgaste da ferramenta na rugosidade da peça em verde e na correspondente peça sinterizada / Abstract: Advanced ceramics machining is generally done with the objective of correcting distortions in pieces after sintering. In order to comply with this task grinding with a diamond grinding wheel is mainly used with low material removal rates. Turning can be done diamong tool to most of the ceramics, but is runs into very narrow material removal limit conditions, as nanometric cutting depths, which if exceeded change the removal system from ductile to brittle. An alternative is machining the piece on the green state, which presents easy machining without the introduction of harmful defects to mechanical resitance. However, after sintering there are invariably distortions caused by the heterogeneous distribution of density gradients that are located in the most outlying portions of the compacted. In an attempt to remove these gradients, this study examined the influence of different allowance values removed and the corresponding distortion after sintering. Alumina speciments are used for this procedure, with 99,8% purity, from which allowances of 1.0,2.0,3.0,4.0, 5.0 mm are removed by turning with a cermented carbine tool under constant machining conditions. Besides distortion, other output variables were analyzed, such as tool wear, cutting force and surface roughness of the green ceramics and the sintered. The results presents a reduction of the distortion of the sintered piece of 81,4% with the greater allowance removal values and the influence of tool wear on the green machining surface roughness and on the corresponding sintered piece / Mestre