Effects Of Different Processing Conditions Research Articles

Anisotropy in the Mechanical Properties of Thermally Spot-Bonded Nonwovens: Experimental Observations

Anisotropy is evaluated for in-plane mechanical properties, such as tensile modulus, maximum stress in tension, elongation at maximum stress, shear modulus, and bending rigidity, of three designed sets of spot-bonded nonwoven fabrics. Image analysis is used to quantify the fiber orientation distribution and identify failure mechanisms. The non-woven fabrics in this study have been produced specifically to explore the effects of different processing conditions (temperature, pressure, and bond area) on mechanical performance. The results show that, within a typical window of processing conditions, bond area and bonding temperature have a significant influence on all the mechanical properties. The data also suggest that failure of thermally bonded nonwoven structures is likely to be governed by critical stress-based criteria. An important inference from this work is the recognition that the mechanical properties of thermally spot-bonded nonwoven structures can be described quantitatively through a simple composite model. The results also suggest that the azimuthal properties of the bonded and nonbonded regions, and thus the nonwoven, are likely to be amenable to continuum models of materials with ortho-tropic symmetry.

Estratégias para modelagem de dados multivariados na presença de correlação

Dados multivariados ocorrem com freqüência em investigações empíricas. Em estudos de Engenharia, por exemplo, dados multivariados são coletados ao estudar-se o efeito de diferentes condições de processamento sobre características de itens manufaturados. Tais conjuntos de dados podem apresentar variáveis altamente correlacionadas. Neste artigo, investiga-se o efeito da estrutura de correlação de variáveis dependentes em sua modelagem, a partir de regressão linear. Quatro técnicas de regressão são apresentadas e comparadas: regressão de mínimos quadrados ordinários, regressão de mínimos quadrados generalizados, regressão por equações aparentemente não relacionadas e regressão multivariada. Como modelos de regressão são, via de regra, utilizados com fins preditivos, as técnicas de modelagem acima são comparadas com base em sua variância de predição. As diferentes técnicas de regressão são ilustradas em um estudo de caso.

Study of chemical vapor deposition reaction between tungsten hexafluoride and silicon difluoride

A low-pressure chemical vapor system which deposits tungsten based thin films on a substrate, using a horizontal hot-wall reactor has been studied. WF 6 and SiF 2 were used as precursors to deposit materials containing tungsten, at temperatures between 100 and 800 °C. Results demonstrate that a deposition temperature below 400 °C led to polycrystalline tungsten and silicon oxide. Tungsten films deposited at higher temperature (300–400 °C) were normally present in the α structure while for those tungsten films deposited at lower temperature (<300 °C), XRD patterns indicated mixed α and β phases. As the reaction temperature was increased to ≥500 °C, polycrystalline tungsten silicide and polycrystalline silicon were deposited on the surface of the substrate. This study investigates the effect of different processing conditions for forming W and WSi 2 and the role of SiF 2 in their formation.

Manufacture of a carbon-fabric-reinforced polyetherimide (CF/PEI) composite material

Relationships between impregnation mechanisms, consolidation quality and the resulting mechanical properties of carbon-fibre-fabric reinforced polyetherimide (CF/ PEI) thermoplastic composites have been investigated. A compression-moulding procedure was applied to simulate the effects of different processing conditions (i.e. pressure, holding time and processing temperature) on the quality of finished samples. Microscopic studies of cross-sections, density measurements and flexural mechanical properties were used to examine the quality of impregnation and consolidation. A qualitative model to describe the impregnation and consolidation processes of this material was developed. It predicts the variations of void content during consolidation, as well as the holding time, moulding temperature and pressure required to reach full consolidation. Good agreement between theoretical predictions and experimental data indicates the success of the approach. Finally, aileron ribs for a civil aircraft were successfully manufactured from the CF/PEI material according to the suggested optimum processing conditions.

A new approach to describe oil absorption in fried foods: a simulation study

The mechanism of oil absorption of tortilla chips during cooling was analyzed using capillary pressure theory. The experimental and theoretical results obtained with this mechanistic model agreed well. Computer simulations were made to determine the effect of different process conditions on the final product oil content. The results show higher oil content for tortilla chips with higher initial moisture content, smaller radius, lower cooling air temperature, and higher interfacial tension.

Evaluation of Starch Modifications from Thermo-Mechanical Processes by NMR

Low resolution NMR technique was used to measure the effects of different process conditions on the transverse relaxation signal of different industrial products, sauces, cake batters and corn flakes. In sauces, the increase of the global relaxation time was related to cooking time and temperature. The cooking effect of batters was associated to a significant increase of the liquid-like starch protons and a transfer of sugared water in the starch partially gelatinized. The transverse relaxation behaviour of corn was very sensitive to the flaking process: a proton population tended to disappear with the increase of the flaking intensity.

Tungsten Silicide Films Based on Dichlorosilane Chemistry for sub 0.5 Micron Applications

AbstractCVD WSix, films have found widespread use as ultra thin gate, wordline and bitline interconnects due to the lower resistance that polycide offers. For submicron technologies, WSix films based on the monosilane chemistry shows limitations due to the incorporation of high concentrations of Fluorine ions and poor step coverage. Recent work has shown that, WSix films based on the dichlorosilane (DCS) chemistry minimizes these problems. One of the major issues in DCS WSix films is the in-depth compositional non uniformity, especially those deposited on poly-Si substrates. The formation of a W-rich region at the WSix/poly-Si interface can cause localized stresses which can result in cracking and adhesion problems. In this paper, we report the composition and structure of DCS WSix, films deposited on undoped, doped and in situ doped poly-Si and oxide substrates. We have investigated the effect of different processing conditions on Si/W uniformity and the formation of W-rich and Si-rich interfaces, and the role of the nucleation step in modulating the Si/W ratio at the WSix/poly-Si interface. The impact of a Si-rich region at the WSix/poly-Si interface on silicide film properties has also been explored. RBS measurements were used to determine the composition profile through the depth of the film and Si/W uniformity in terms of Si-rich and W-rich interfaces. SIMS measurements were used to determine the impurity content in the silicide film and at the film/substrate interface.

Nucleation on SiO2 during the Selective Chemical Vapor Deposition of Tungsten by the Hydrogen Reduction of Tungsten Hexafluoride

A horizontal hot‐wall chemical vapor deposition (CVD) quartz reactor with rectangular cross section was used to study the effect of different process conditions on the nucleation of tungsten on during selective WCVD by the reduction of . The experimental procedure included placing a metallic surface at the center of the reactor, and small samples of at different positions both upstream and downstream with respect to the metallic surface. Digitized scanning electron microscopy micrographs were used to determine the particle size distributions of nuclei on the surfaces. We found that the amount of nucleation on decreases when smaller metallic surfaces are present and for lower temperatures and shorter process times. Although nucleation was always greatest on samples closest to the metal sample, the effect of flow rate depended on the position of the . A statistical nearest neighbor analysis indicated a clustering of W nuclei on the . A simplified mathematical model was developed to predict concentration profiles of a gaseous intermediate generated at the metal surface during the thermal decomposition of the source gas. This intermediate has been proposed as being the reactive species that causes nucleation on surface. Qualitative agreement between experimental and theoretical results reinforce the proposed role of the intermediate with this species being characterized by a short lifetime.

Microstructural development during solidification of stainless steel alloys

The microstructures that develop during the solidification of stainless steel alloys are related to the solidification conditions and the specific alloy composition. The solidification conditions are determined by the processing method,i.e., casting, welding, or rapid solidification, and by parametric variations within each of these techniques. One variable that has been used to characterize the effects of different processing conditions is the cooling rate. This factor and the chemical composition of the alloy both influence (1) the primary mode of solidification, (2) solute redistribution and second-phase formation during solidification, and (3) the nucleation and growth behavior of the ferrite-to-austenite phase transformation during cooling. Consequently, the residual ferrite content and the microstructural morphology depend on the cooling rate and are governed by the solidification process. This paper investigates the influence of cooling rate on the microstructure of stainless steel alloys and describes the conditions that lead to the many microstructural morphologies that develop during solidification. Experiments were performed on a series of seven high-purity Fe-Ni-Cr alloys that spanned the line of twofold saturation along the 59 wt pct Fe isopleth of the ternary alloy system. High-speed electron-beam surface-glazing was used to melt and resolidify these alloys at scan speeds up to 5 m/s. The resulting cooling rates were shown to vary from 7°C/s to 7.5×106°C/s, and the resolidified melts were analyzed by optical metallographic methods. Five primary modes of solidification and 12 microstructural morphologies were characterized in the resolidified alloys, and these features appear to be a complete “set” of the possible microstructures for 300-series stainless steel alloys. The results of this study were used to create electron-beam scan speedvs composition diagrams, which can be used to predict the primary mode of solidification and the microstructural morphology for different processing conditions. Furthermore, changes in the primary solidification mode were observed in alloys that lie on the chromium-rich side of the line of twofold saturation when they are cooled at high rates. These changes were explained by the presence of metastable austenite, which grows epitaxially and can dominate the solidification microstructure throughout the resolidified zone at high cooling rates.

ChemInform Abstract: Process Dependence of the Si‐SiO2 Interface Trap Density for Thin Oxides.

AbstractThe effects of different processing conditions (oxidation temp., time, atmosphere, annealing atmosphere, temp., time) on the interface trap density of thin (∼ 100‐400 Å) thermal oxides have been investigated using the quasi‐static capacitance‐voltage technique.

A newly developed warm extrusion technique for compacting amorphous alloy powders

Improvement in warm extrusion processing have been made to prepare bulk amorphous alloys from amorphous alloy powders. Flake-form amorphous alloys of Fe 78B 13Si 9 and Co 69Fe 4Ni 1Mo 2B 12Si 12 were used. When a billet of powder, packed into a cylindrical container, was extruded, a completely homogeneous bulk amorphous alloy was not obtained. However, when a core of suitable material and diameter was placed along the central axis of the container, a homogeneous bulk amorphous alloy was obtained by extruding the billet under certain specific conditions. The compacts obtained, moreover, had a density equal to 99.9% that of ribbon, and the magnetic properties were the best so far reported for bulk amorphous alloys. In this paper, the effects of different process conditions on compactibility are also discussed.

The distribution of lead in lead-stabilized rigid PVC pipes, as studied by scanning electron microscopy

Samples with flat, smooth surfaces were removed from rigid PVC pipes using a diamond saw, then studied in a scanning electron microscope fitted with a Robinson detector and an environmental cell, which gives an image of the back-scattered electron intensity. In such images, lead-containing particles appeared as bright spots against a dark background. This is due to the fact that the intensity of the back-scattered electrons increases with atomic number. It is shown that this method can be used to study the effect of different processing conditions on the distribution of the stabilizer in lead-stabilized rigid PVC.

Effect of Different Processing Conditions on Amino Acid Digestibility of Feather Meal Determined by Chicken Assay

An investigation was made of the effect of different processing conditions on feather meal (FM) by amino acid digestibility (AAD) determinations. Three processing times (30, 50, and 70 min) and three methods of treatments (without additions, .4% added NaOH, and .4% added proteolytic enzyme) were involved. The AAD of the test FM was measured by quantitative excreta collection over a period of 36 hr. All the test chicks were precision fed with 12 g of FM (dry matter), given in 2 doses with a 3-hr interval between feeds. Correction was made for metabolic plus endogenous excretions by using an N-free diet to distinguish apparent from true digestibility of amino acids (AA).The apparent and true digestibility of all individual AA were influenced by the processing conditions. There was a (linear-negative) time effect on the digestibility of all AA of the FM, with the exception of leucine. Significant differences in digestibility coefficients due to the method of treatment were found for cystine, tyrosine, phenylalanine, serine, and alanine. These AA values were lower in the chemically-treated FM. Comparison between the three methods of FM treatment revealed higher values for the enzymatically-treated samples and lower values for the chemically-treated ones, compared with samples treated without additions.Digestibility values for individual AA varied substantially. The values ranged in apparent digestibility values from 22.5% for lysine to 82.4% for isoleucinie and, in true digestibility values, from 36.3% for aspartic acid to 86.5% for isoleucine. The limiting essential AA, lysine, histidine, and methionine, in increasing order, were particularly low in digestibility. The unnatural AA lanthionine, present in all test FM, was not totally recovered in excreta and was found to be inversely proportional to its AAD.The results lead to the general conclusion that FM amino acids are affected in their biological digestibility by different processing conditions, time being the most significant one. Thus, FM protein should be used in poultry diets on the basis of the digested AA because of the large variations in digestibility between the individual AA.

Measurement of the rate at which pigments disperse during mixing

Experience has shown that the evaluation of size, and the numerical distribution of sizes in a population of pigment particles dispersed in a solid, transparent polymer can only be achieved using an optical microscope. This is an extremely long and tedious process, which is made more so by the need to examine a large proportion of the sample in order to reduce sampling errors. Over the past four years a Quantimet has been used to reduce the importance of these difficulties. With the manual version of this instrument another problem assumed importance: data logging and data handling. We have improved our technique for evaluating the results obtained by installing automatic output. Data are obtained on paper tape, and can be checked, sorted and processed by conventional computer techniques. A single number can be computed, which describes the “dispersibility” of a pigment, i.e. the rate at which it disperses under a single, constant rate of shear. The use of this parameter will not only enable dispersion to be improved, but will allow the effects of different processing conditions to be anticipated for both single pigments and mixtures (by means of comparisons between pigments). It will also offer an improved means of selecting both plant and pigment (s) to suit the final product.