Effects Of Different Processing Conditions Research Articles

Intrinsic kinetics of one-step dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst

The reaction kinetics of the dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst was investigated using an isothermal integral reactor at 220–260°C temperature, 3–7 MPa pressure, and 1,000–2,500 mL/g·h space velocity. The H2/CO ratio of the synthetic gas was chosen between 3 : 1 and 6 : 1. The bi-functional catalyst was prepared by physically mixing commercial CuO/ZnO/Al2O3 and γ-alumina, which act as methanol synthesis catalyst and dehydration catalyst, respectively. The three reactions, including methanol synthesis from CO and CO2 as well as methanol dehydration, were chosen as independent reactions. The Langmuir-Hinshelwood kinetic models for dimethyl ether synthesis were adopted. Kinetics parameters were obtained using the Levenberg-Marquardt mathematical method. The model was reliable according to statistical and residual error analyses. The effects of different process conditions on the reactor performance were also investigated.

The effect of processing conditions on the microstructure and impact behavior of melt infiltrated Al/SiCp composites

In the current research, pressureless melt infiltration (PMI) was applied to study the effect of different processing conditions on the final properties of Al/SiC composites, fabricated through the infiltration of aluminum melt into SiC particulates porous preforms. Charpy impact test was used to explore the impact behavior of the Al/SiC composites, obtained from variable processing conditions. Conducting the process at a higher infiltration temperature (1350 °C) increased the final relative density of composites up to the value of 0.97 of theoretical density (TD). The application of a post sintering procedure in nitrogen atmosphere after the completion of infiltration resulted in a slight increase (∼1) in the final density of composites compared to the only infiltrated ones. Instead, the final density of argon sintered composites has undergone a 0.41% reduction. This can be originated from the occurrence of chemical reactions in the N 2 atmosphere resulting in the formation of consequent phases, contrary to the argon neutral gas. Results concerning with the impact resistance demonstrated a remarkable superiority for the impact energy of the composites subjected to the combined infiltration and sintering (MIS) procedure compared to the infiltrated ones. While such an observation was found to be identical through sintering in both atmospheres, the appearance of brittle phases formed through sintering procedure in nitrogen gave rise to higher impact energy for the argon sintered composites.

Image Analysis of Microstructural Changes in Almond Cotyledon as a Result of Processing

Release of oil from nuts due to damaged cellular structures can degrade the quality of products incorporating nuts. The aim of this study was to investigate the effects of different processing conditions on microstructure of almond tissue and to quantify these changes using image processing. Spinning disk confocal fluorescence microscopy was used for imaging changes in microstructure of almonds as a function of different thermal processing of almonds. Multiple staining of Nile Red and Calcofluor White was applied to differentiate cell wall structures and oil bodies within individual almond cells without chemical fixation. An algorithm for image processing, included image preprocessing, segmentation, and determination of morphological features of segmented objects, was developed. Oil-roasting processes (140 °C and 150 °C) were found to have a significant impact on microstructure of almonds when compared to the hot air-roasting and blanching processes. Oil-roasted almond at 150 °C had a greater cellular damage due to cell wall and membrane rupture. These changes in microstructure of almonds would make them slightly more susceptible to release oil during storage. The image analysis presented allows quantitative evaluation for the effect of different processing on almond microstructure.

Uniform shell patterning using rubber‐assisted hot embossing process. I. Experimental

AbstractIn rubber‐assisted hot embossing, a softened thin thermoplastic film is pressurized between a hard mold surface and a rubber pad. The rubber pad, as a soft counter‐tool, deforms conformably to the hard mold surface, allowing feature transfer from the hard surface and formation of shell‐type structures on the polymer film. This two‐article sequence was aimed to understand the basic mechanisms affecting the pattern uniformity and replication in rubber‐assisted hot embossing. In Part I, a series of rubber‐assisted embossing experiments involving parametric studies of the effects of different processing conditions, as well as material selections, on the pattern thickness uniformity and replicated pattern height were conducted. The difference in film thickness uniformity in different experiments was explained using the mechanical and rheological behavior of the polymer film and the rubber counter‐tool under different processing conditions. Based on the experimental results, strategies for determining a feasible process window for achieving uniform shell patterning by rubber‐assisted embossing were proposed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Optimization of inline coagulation in integrated membrane systems: A study of FeCl3

This research investigated the effect of different process conditions (pH, G, Gt and coagulant dose) on inline coagulation pre-treatment of ultrafiltration (UF) with FeCl3. Delft canal water was coagulated with FeCl3 and filtered through a 0.1 µm PVDF filter in an Amicon unstirred cell. Filtration was performed in dead-end mode at a constant pressure of 0.1 MPa and at 20°C. Membrane fouling was quantified by calculating the modified fouling index (MFI) of the coagulated solutions. For coagulation with FeCl3, results showed that at higher coagulant dose (>10 mg Fe3+/L), the effect of flocculation time on MFI becomes negligible such that MFI is almost constant for 15 mg Fe3+/L for flocculation times ranging from 0 to 60 min. It was also observed that a relatively high dose (5 mg Fe3+/l) and long flocculation time (60 min) can compensate for the adverse effect of low pH on MFI. While proper flocculation can be designed and achieved prior to membrane filtration, Gt and retention times within the pipes and mem...

Two-step Ni silicide process and influence of protective N2 gas

A two-step process of Ni silicide formed on bulk silicon, and the effects of different process conditions, including two-step RTA temperature and time, selective etching, and process protective nitrogen gas on the properties of the Ni silicide film have been studied. In particular, the experiments show that the quality of NiSi film is very sensitive to the process conditions of the first RTA. The experiments also show that the quality of the film is very sensitive to the flow of protective nitrogen gas. The corresponding mechanisms are discussed.

The Catalytic Hydrogenation of Aromatic Nitro Ketone in a Microreactor: Reactor Performance and Kinetic Studies

Catalytic hydrogenation of nitro aromatics is an important class of reactions in the pharmaceutical and fine chemical industries. These reactions are extremely fast and highly exothermic in nature; hence, mass and heat transfer limitations play an important role when these reactions are conducted in conventional batch reactors. The use of a micro-channel reactor for such reactions provides improved mass transfer rates which may ensure that the reaction operates close to intrinsic kinetics. In the present study, the hydrogenation of a model aromatic nitro ketone was conducted in a packed-bed microreactor. The effects of different processing conditions were studied using 5%Pd/Alumina catalyst, viz.: hydrogen pressure, substrate concentration, temperature, and residence time on the conversion of substrate, Space Time Yield (STY), and selectivity of product. Internal and external mass and heat transfer limitations in the microreactor were examined. The kinetic study was undertaken in a differential reactor mode, keeping the conversion of the reactant at less than 10%. The overall reaction was treated as comprising two separate reactions: first, the reduction of the nitro compound to hydroxylamine and then, the reduction of the hydroxylamine to amine. Two rate equations for the two consecutive reactions assuming the Langmuir-Hinshelwood mechanism provided the best fit to the experimental data. These two rate equations predicted the experimental rates satisfactorily and the differences were within 10% error. Experiments were also carried out in an integral reactor, and the reactor performance data were found to be in agreement with the predictions of the theoretical models.

Fabrication of porous poly(L-lactide) (PLLA) scaffolds for tissue engineering using liquid–liquid phase separation and freeze extraction

PLLA scaffolds were successfully fabricated using liquid-liquid phase separation with freeze extraction techniques. The effects of different processing conditions, such as method of cooling (direct quenching and pre-quenching), freezing temperature (-80 degrees C and -196 degrees C) and polymer concentration (3, 5 and 7 wt%) were investigated in relations to the scaffold morphology. SEM micrographs of scaffolds showed interconnected porous network with pore size ranging from 20 to 60 microm. The scaffolds had porosity values ranging from 80 to 90%. Changes to the interconnected network, porosity and pore size were observed when the method of cooling and polymer concentration was changed. Direct quenching to -80 degrees C gave a more porous interconnected microstructure with uniform pore size compared to samples prepared using pre-quenching method. Larger pores were observed for samples quenched at -80 degrees C compared to -196 degrees C. Scaffolds prepared using direct quenching to -196 degrees C had higher elastic modulus and compressive stress compared to those quenched to -80 degrees C. The compressive elastic modulus ranged from 4 to 7 MPa and compressive stress at 10% strain was from 0.13 to 0.18 MPa.

Effects of Thixoforming Defects on the Stress-Strain Curves of Aluminum Structural Parts for Automobile

The effects of thixoforming defects on the stress-strain curves of aluminum structural part were quantitatively investigated. The A357-MHD billet was thixoformed to manufacture a shock tower part of a small electric vehicle. All tensile specimens were machined from only a shock tower product to minimize the effects of different processing conditions. Tensile tests were performed under the almost same conditions. The fraction of solid and liquid phase, the sizes and area fractions of defects in the specimens were measured and analyzed by an image analyzing program using OM and SEM micrograph. The fracture strain values of the stress-strain curves were greatly affected by amount of defects. However, the analyses with defects existed in the area of gauge length did not show a clear explanation about the relation with the fracture strain values. The measurements of defects in the fractured surface represented more plausible results about the correlation of forming defects and fracture strains.

Phase evolution and Sn-substitution in LiMn2O4 thin films prepared by pulsed laser deposition

LiMn2O4 thin films prepared on a Pt/Ti/SiO2/Si(100) substrate by pulsed laser deposition were studied with focusing on the effects of different processing conditions and Sn substitution on phase evolvement and surface microstructure. Major experimental parameters include substrate temperature up to 770 °C and working oxygen pressure of 50–250 mTorr. LiMn2O4 thin films became highly crystallized with increased grain sizes as the substrate temperature increased. Second phases such as LiMnO2 and Li2Mn2O4 were found at the temperature of 300 and 770 °C, respectively. As an optimum condition, films grown at 450 °C showed a homogeneous spinel phase with well-defined crystallinity and smooth surface. A high pressure of oxygen tended to promote crystallization and grain growth. Working pressure did not affect significantly the phase formation of the thin films except that unexpected LiMn3O4 phase formed at the lowest oxygen pressure of 50 mTorr. Tin-substituted thin films showed lower Mn–O stretching vibrations, which suggests that more Li-ions can be inserted into vacant octahedral sites of the spinel structure.

Comparative study of physical and sensory properties of pre-treated potato slices during vacuum and atmospheric frying

The objective of this research was to study the effect of different processing conditions on physical and sensory properties of potato chips. Potato slices of Desirée and Panda varieties (diameter: 30 mm; thickness: 3 mm) were pre-treated in the following ways: (i) control or unblanched slices without pre-drying; (ii) blanched slices in hot water at 85 °C for 3.5 min and air-dried at 60 °C until a final moisture content of ∼0.6 kg water/kg dry solid; (iii) control slices soaked in a 3.5 kg/m 3 sodium metabisulphite solution at 20 °C for 3 min and pH adjusted to 3. Pre-treated slices were fried at 120 and 140 °C under vacuum conditions (5.37 kPa, absolute pressure) and under atmospheric pressure until they reached a final moisture content of ∼1.8 kg water/100 kg (wet basis). An experimental design (3 × 2 3) was used to analyze the effect of pre-treatment, potato variety, type of frying and frying temperature over the following responses: oil content, instrumental color and texture and sensory evaluation. Vacuum frying increased significantly ( p < 0.05) oil content and decreased instrumental color and textural parameters. Sensory attributes, flavor quality and overall quality, were significantly improved using vacuum frying. The higher frying temperature (140 °C) increased Δ E, maximum breaking force, hardness and crispness and decreased L * and b * values. On the other hand, Panda potato variety improved the color of the product. A great improvement on color parameters was obtained using sulphited potato slices instead of the other pre-treatments. Although, the better flavor was obtained for control potato chips, no significant differences were found for overall quality between control and sulphited potato chips. Significant correlations ( p < 0.01) between sensory and instrumental responses were found.

Influence of Processing Conditions on Acrylamide Content in Black Ripe Olives

The presence of acrylamide was investigated in different presentations of commercial black ripe olives, a well-known sterilized alkali-treated product. The analysis was performed by gas chromatography-mass spectrometry (GC-MS) after bromination of acrylamide, using (13C3)acrylamide as internal standard. In-house validation data for commercial ripe olives showed good precision and accuracy of the method, with repeatability below 3% and recoveries between 94 and 105%. Acrylamide was detected in all samples, but its concentration varied significantly from 176 to 1578 microg/kg of pulp. The effects of different processing conditions (two preservation methods and three darkening methods), cultivar (Hojiblanca or Manzanilla), and presentation form (pitted or sliced olives) on acrylamide content were evaluated in experiments performed in an olive-processing plant. All canned samples were sterilized at 121 degrees C for 30 min. Statistical analysis of the data indicated that the effects of darkening method and olive cultivar were the most pronounced. Acrylamide contents did not significantly differ after 6 months of storage. The small amounts of free amino acids and reducing sugars found in olives before sterilization did not significantly correlate with the acrylamide formed.

Catalytic hydrogenation of o-nitroanisole in a microreactor: Reactor performance and kinetic studies

Hydrogenation of o-nitroanisole to o-anisidine was conducted in a packed-bed microreactor as a model hydrogenation reaction of importance to the pharmaceutical and fine chemicals industries with the aim of investigating the reactor performance and kinetics of the reaction. The effects of different processing conditions viz. hydrogen pressure, o-nitroanisole concentration, temperature, and residence time on the conversion of o-nitroanisole, space-time yield (STY), and selectivity of o-anisidine were studied using 2% Pd/zeolite catalyst. The kinetic study was undertaken in a differential reactor mode keeping the conversion of o-nitroanisole at less than 10%. During the kinetic study, it was observed that the intermediate 2-methoxynitrosobenzene was present in the reactor at low catalyst loading and low conversions because of short residence time in the reactor. Therefore, for the kinetics study, the overall reaction was treated as comprising two separate reactions: first the reduction of o-nitroanisole to 2-methoxynitrosobenzene and then, the reduction of 2-methoxynitrosobenzene to o-anisidine. Internal and external mass and heat transfer limitations in the microreactor were examined. Different rate laws using different mechanisms from the literature were considered to fit the experimental data. Two rate equations for the two consecutive reactions assuming Langmuir–Hinshelwood mechanism provided the best fit to the experimental data. These two rate equations predicted the experimental rates within 10% error. Experiments were also carried out in an integral reactor, and the reactor performance data were found to be in agreement with the predictions of the theoretical models.

Carbon Nanospheres for Biomedical Applications

ABSTRACTCarbon nanostructures, e.g., nanotubes, fullerenes, carbon blacks, etc., are being extensively explored for numerous biomedical applications. The most of such studies, however, deal with carbon nanotubes, and comparatively less is known on the biomedical potential of other nanosize carbon particles. In the present work, carbon and metal/carbon core/shell spherical nanoparticles have been prepared using the decomposition of monosaccharide-based compositions under hydrothermal conditions with or without the presence of metal seed particles. The effects of different process conditions on the particle size, structure, and composition have been examined using TEM, XRD, UV-Vis, FTIR and Raman spectroscopies. The nearly perfect spherical particles with the dimensions in the range of 20 – 100 nm have been obtained depending on the process parameters such as precursor concentration, presence of seed particles and polymeric additives, process temperature and time. The particles prepared with 5 – 20 nm gold seeds clearly showed the core/shell structure with the thickness of carbon shell in the range of 10 – 50 nm. The FTIR experiments have indicated a strong effect of the processing conditions on the chemical activity of nanoparticle surfaces in the attachment of the additional surface functional groups and organic molecules. It has been found that the both hydrothermally prepared carbon and metal/carbon core/shell nanoparticles possess very good dispersibility and stability in the both water and simulated body fluids in the most of experiments. The particles have been successfully functionalized with several molecules such as polyethyleneglucol and biotin. Selected samples of well-dispersed carbon nanospheres with different concentrations have been tested for their interaction with several cultured cell lines including epidermal keratinocytes, fibroblasts, and dog macrophages.

Influence of processing of full fat soya beans included in diets for piglets. I. Performance

The programme reported examined the effect of different processing conditions for full fat soya beans (FFSB) during micronization (two steam inlets, being full or low steam—(FS or LS) × two temperatures, being high cook and low cook (HC and LC); Trial 1) and extrusion (four exit temperatures of 70, 90, 110 and 170 °C; Trial 2) on performance in post-weaned piglets over the live weight range 10–27 kg fed diets containing 300 g processed FFSB/kg. Trypsin inhibitor activity (TIA, mg pure trypsin inhibited/g of sample) ranged from 16.0, 5.2, 4.1 and 2.0 for LSLC, LSHC, FSLC and FSHC, respectively (Trial 1) and from 24.1, 16.8, 6.4 and 2.9 with increasing extrusion temperature (Trial 2). In Trial 1, piglets offered the FS FFSB diets had significantly higher daily live weight gain (DLWG, 652 versus 487 g/day, P < 0.001), consumed significantly more feed (feed intake, FI, 791 versus 679 g DM/day, P < 0.001) and had a significantly better feed conversion ratio (FCR, 1.211 versus 1.404, P < 0.001). There were no effects of temperature or steam × temperature interactions. Performance characteristics were highly correlated with reduced intake of TIA (dietary intake of TIA × feed intake; P < 0.001 for DLWG and P = 0.002 for FI and FCR). In Trial 2, there was a significant linear improvement in DLWG ( P = 0.004, but not quadratic) a significant change in FI ( P = 0.026 quadratic, but not linear) and a significant linear improvement in FCR ( P < 0.001, but not quadratic) with increasing extrusion temperature. DLWG and FCR were negatively correlated to increasing daily TIA intakes ( P < 0.05). Both trials allowed an assessment of the response to TIA intake; performance was optimum at low daily intakes of TIA (between 0.5 and 1.5 g/day) irrespective of processing method. Decisions on optimum processing conditions should be based on TIA levels in FFSB, the rate of inclusion and subsequent feed intake (giving, collectively, daily TIA intake) and not simply on named processes.

Comparison of low-frequency noise in III–V and Si∕SiGe HBTs

The low-frequency noise characteristics of double self-aligned InP/InGaAs and two types of Si/SiGe heterojunction bipolar transistors (HBTs) were investigated. Spectral analysis shows no striking differences; the spectra are composed of a 1/f component and the white noise is always reached at low biases. A general trend for all the transistors was the presence of Lorentzian component(s) for the smallest devices. The voltage coherence function was always unity for SiGe transistors; and for the first time, it was found to be close to zero for InP devices. Concerning the 1/f noise level, both types of transistors have approximately a quadratic dependence on base current bias and an inverse dependence on the emitter area. Thus, a comparison of the 1/f noise level has been made using the K/sub b/ parameter, and values around 10/sup -9/ /spl mu/m/sup 2/ for SiGe HBTs and around 10/sup -8/ /spl mu/m/sup 2/ for InP HBTs were found. These results are of the same order of magnitude as the best published ones. The low-frequency noise results suggest that excess noise sources are mainly located at the intrinsic emitter-base junction for the two types of SiGe devices, and, for the InP HBTs, a correlated noise source is located at the emitter periphery. To compare different devices and technologies, f/sub c//f/sub T/ was studied as a function of collector current density and for some HBT technologies f/sub c//f/sub T//spl prop/J/sub c/ (f/sub c/ is corner frequency at which the white noise and 1/f noise are equal and f/sub T/ is the unity current gain frequency). The effects of different processing conditions, designs and temperature were also investigated and discussed.

The characterisation of magnetic pigment dispersions using pulsed magnetic fields

In this work, we describe the application of pulsed field magnetometry techniques for the characterisation of magnetic pigment dispersions. Magnetic pigment dispersions are important technological materials as in one form they are the material which are used to coat base film in order to make magnetic recording tape. It is these materials that have been evaluated. In this work, we describe the use of two pulsed field magnetometers, one being a low-field instrument with a maximum field of 750 Oe and the other a high-field instrument with a maximum field of 4.1 kOe. Using inductive sensing, the magnetisation is monitored in real time as the pulse is applied. We find that using these techniques we can successfully monitor the progress of the dispersion process, the effects of different resin systems and the effect of different processing conditions. We find that our results are consistent with rheological and other measurements.

USE OF DSC TO STUDY THE FLOW PROPERTIES OF HYDROCRACKED BASE STOCKS AND LUBRICATING OILS

ABSTRACT The differential scanning calorimetry (DSC) technique was found useful in assessing the effect of different processing conditions on the wax content and the wax-type of hydrocracked base stocks. The DSC thermograms showed a wide crystallization peak, in the range from −40 to −20°C, indicating the presence of paraffinic wax molecules. The second, narrow crystallization peak at about −75°C, indicated the presence of lower melting isoparaffinic or branched-type wax molecules. The DSC technique was used to study the onset wax crystallization temperature and the wax formation in hydrocracked base stocks containing different chemistry pour point depressants. The fumarate-vinylacetate (FVA) pour point depressant was not as effective as polymethacrylate (PMA) type chemistry. A decrease in depressed pour points of hydrocracked base stocks was found to follow a decrease in the onset wax crystallization temperature. In engine oil formulations containing hydrocracked base stocks, a decrease in depressed pour point was also found to follow a decrease in the onset wax crystallization temperature. For pour point depressants used in lubricating oils, the mechanism of decreasing the onset wax crystallization was found to be more important than the mechanism of suppressing the wax formation.

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.