Role Of Processing Conditions Research Articles

Microfiltration of concentrated albumin solutions and the role of processing conditions on membrane fouling

Membrane processing is a subject of growing scientific and industrial interest as a valuable technology to replace conventional energy-intensive operations, but is hindered by the progressive decrease of permeate flux caused by membrane fouling. Although physico-chemical factors affecting membrane fouling have been widely investigated, less is known concerning the effects of processing conditions. Here, we focus on microfiltration of aqueous bovine serum albumin (BSA) solutions by using a novel miniaturized modular unit allowing to study both dead-end (DE) and crossflow (CF) filtration. Pure water flux measurements and Computational Fluid Dynamics (CFD) simulations were firstly performed to characterize the flow field inside the module. In presence of BSA, at the same transmembrane pressure (TMP) of 20 mbar and average pore size of 0.45 μm, a remarkable decrease in the fouling progression with time was found for CF with a peristaltic pump as compared to pressure-driven DE filtration. Furthermore, BSA concentration in the permeate was the same as in the feed for peristaltic CF, while negligible for DE. By either increasing transmembrane pressure or lowering membrane pore size, a stronger decay of permeate flux with time was observed. Scanning electron microscopy images of the membrane showed the presence of a thick surface cake layer under peristaltic CF, which became thinner by increasing TMP or reducing membrane pore size. Overall, the better performance of peristaltic CF can be interpreted in terms of reduced BSA residence time in the membrane, membrane deformability and formation of a permeable cake layer at lower TMP and larger membrane pore size. The innovative design of our filtration module and the combination of permeate flux and concentration measurements with CFD results and microscopy observations constitute the most significant aspects of this research work, which provides a multiscale picture of membrane fouling. The insight emerging from results aims to provide qualitative guidelines towards an optimal setting of processing conditions in membrane operations, which is highly needed to improve the membrane innovation pipeline.

Role of Processing Conditions on the Structure-Property Correlation of Hvaf Sprayed Cr3c2-Nicr Coatings for Improved Erosion Resistance

Role of Processing Conditions on the Structure-Property Correlation of Hvaf Sprayed Cr3c2-Nicr Coatings for Improved Erosion Resistance

Thermally conductive h-BN reinforced PEI composites: The role of processing conditions on dispersion states

In this study, h-BN, reinforced PEI composites were studied up to 30 wt% through optimizing process conditions of melt-mixing to tune the thermal conductivity at relatively low-filler ratios while possessing a scalable manufacturing process with thermoplastics operating at high temperatures. The effects of processing parameters on the rheological properties and thermal conductivities of resulting h-BN/PEI composites were determined. DSC and TGA analyses showed that h-BN addition did not lead to a significant change in Tg; however, thermal decomposition temperatures of PEI were shifted. At 30 wt% h-BN loading, a high thermal conductivity as 0.82 W/mK was achieved, which is three times that of neat PEI. The significant enhancement in thermal conductivity was attributed to effective dispersion state of h-BN, creating an enhanced phonon transport mechanism confirmed through rheological analysis. This work provides a thermo-economic solution with relatively low-filler loading ratios in a high temperature and high performance operating polymer. These polymer composites were successfully fabricated in a filament form as candidates for lightweight advanced packaging materials by either injection molding or 3D printing.

Identifying the role of process conditions for synthesis of stable gold nanoparticles and insight detail of reaction mechanism

The meticulous modulations of size and morphology are challenging to produce scale of plants mediated gold nanoparticles (AuNPs). In addition, the specific role of phytochemicals to precede the bio-reduction reaction and capping of the nanoparticles is also a mystery and need to be addressed. In the same line of action, we reported a green, eco-friendly, efficient and one-step method for synthesis of tailored size and shaped AuNPs and were controlled by various process parameters including pH, volume of extract and concentration of gold precursor. Bio-reduction process and formation of AuNPs were identified through various characterization techniques including UV-vis, TEM, DLS, FTIR, XRD and XPS. Shapes of AuNPs were observed predominantly spherical with average projected and hydrodynamic diameters of 9.49 and 168 nm respectively. The role of phytochemicals acting as active reducing and capping agents has been recognized and explained by the establishment of the reaction mechanism.

Chemical Vapour Deposition of Graphene-Synthesis, Characterisation, and Applications: A Review.

Graphene as the 2D material with extraordinary properties has attracted the interest of research communities to master the synthesis of this remarkable material at a large scale without sacrificing the quality. Although Top-Down and Bottom-Up approaches produce graphene of different quality, chemical vapour deposition (CVD) stands as the most promising technique. This review details the leading CVD methods for graphene growth, including hot-wall, cold-wall and plasma-enhanced CVD. The role of process conditions and growth substrates on the nucleation and growth of graphene film are thoroughly discussed. The essential characterisation techniques in the study of CVD-grown graphene are reported, highlighting the characteristics of a sample which can be extracted from those techniques. This review also offers a brief overview of the applications to which CVD-grown graphene is well-suited, drawing particular attention to its potential in the sectors of energy and electronic devices.

Semi‐Batch Photocatalytic Reduction of Nitrates: Role of Process Conditions and Co‐Catalysts

AbstractPhotocatalysis has been used to reduce nitrate ions from waste and drinking water. A semibatch photoreactor was developed for this process and commercial nanostructured TiO2 (P25) and TiO2 in nanosized form prepared by flame spray pyrolysis (FSP) were used as catalysts. Several noble metals were added as co‐catalyst on both titania samples and the chemical physical properties of every sample were studied by XRD, BET and UV‐Vis spectroscopy techniques. The optimum pH to reach the highest conversion of nitrates with lower selectivity toward ammonia was different for P25 and FSP samples, at basic pH and nearly neutral, respectively. The bare and doped FSP samples, with higher surface area, showed higher nitrates conversion with respect to P25‐based samples. The photocatalytic rate of nitrate reduction over undoped TiO2 was higher than that of most noble metal loaded TiO2, except Ag. The highest activity for nitrate conversion has been obtained by adding Ag on P25 and FSP, increasing the conversion up to 3.5 and 1.5 times with respect to the bare semiconductor, respectively.

The Seebeck Coefficient of Sputter Deposited Metallic Thin Films: The Role of Process Conditions

Because of their reduced dimensions and mass, thin film thermocouples are a promising candidate for embedded sensors in composite materials, especially for application in lightweight and smart structures. The sensitivity of the thin film thermocouple depends however on the process conditions during deposition. In this work, the influence of the discharge current and residual gas impurities on the Seebeck coefficient is experimentally investigated for sputter deposited copper and constantan thin films. The influence of the layer thickness on the film Seebeck coefficient is also discussed. Our observations indicate that both a decreasing discharge current or an increasing background pressure results in a growing deviation of the film Seebeck coefficient compared to its bulk value. Variations in discharge current or background pressure are linked as they both induce a variation in the ratio between the impurity flux to metal flux towards the growing film. This latter parameter is considered a quantitative measure for the background residual gas incorporation in the film and is known to act as a grain refiner. The observed results emphasize the importance of the domain size on the Seebeck coefficient of metallic thin films.

One-step solvent-free mechanochemical synthesis of metal iodate fine powders

Metal iodates are strong iodine rich oxidizers which can be used in the formulation of biocidal energetic materials. Generally, metal iodates particles were synthesized by chemical precipitation methods with a large size distribution. In this work, we developed a one-step and solvent-free, high yield method to synthesize metal iodate fine powders by mechanochemistry. Compared to the conventional chemical precipitation method, the size of final products can be reduced by 20–500 times. The method generates particles with a narrower size distribution and high yield, and is sufficiently generic as to enable creation of a variety of metal iodates including AgIO3, Ca(IO3)2, Mn(IO3)2 and Cu(IO3)2. Moreover, the synthesis is conducted in the solid states with little to no solvent. The role of process conditions (temperature, hydration state, and milling time) on reaction products was investigated by TG/DSC and XRD. We believe that crystalline water bound to the metal nitrates precursor lowers the Tammann's temperature sufficient to unbind water so as to promote ion diffusion and thus facilitate reaction in the absence of a solvent. The reaction is promoted by the milling process which attrits the particles to expose fresh unreacted surfaces and reduces particle size.

Effect of SPPS Process Parameters on In-Flight Particle Generation and Splat Formation to Achieve Pure α-Al2O3 Coatings

The present paper describes the role of process conditions in developing phase-pure α-Al2O3 coatings using solution precursor plasma spraying. Different precursor combinations were employed and two ...

Core/shell silicon/polyaniline particles via in-flight plasma-induced polymerization

Although silicon nanoparticles have potential applications in many relevant fields, there is often the need for post-processing steps to tune the property of the nanomaterial and to optimize it for targeted applications. In particular surface modification is generally necessary to both tune dispersibility of the particles in desired solvents to achieve optimal coating conditions, and to interface the particles with other materials to realize functional heterostructures. In this contribution we discuss the realization of core/shell silicon/polymer nanoparticles realized using a plasma-initiated in-flight polymerization process. Silicon particles are produced in a non-thermal plasma reactor using silane as a precursor. After synthesis they are aerodynamically injected into a second plasma reactor into which aniline vapor is introduced. The second plasma initiates the polymerization reactor leading to the formation of a 3–4 nm thick polymer shell surrounding the silicon core. The role of processing conditions on the properties of the polymeric shell is discussed. Preliminary results on the testing of this material as an anode for lithium ion batteries are presented.

Physical properties of extruded snacks enriched with soybean and moringa leaf powder

This study was conducted to investigate the application of extrusion cooking in the production of snacks containing soybean (SB) and Moringa oleifera (MO) leaves as inexpensive sources of micronutrients. The specific objectives were to examine effects of barrel temperature, residence time and moisture content of feed on selected physical properties of extruded snacks (extrudates), namely water absorption index (WAI), water solubility index (WSI) and expansion ratio (ER). The extrudates were obtained by blending different levels of input ingredients of maize flour (MF) (55 to 80%), full fat soybean flour (FFSF) (10 to 30%), and Moringa oleifera leaf powder (MOLP) (5 to 15%). Extrusion process variables in a twin-screw extruder were at three levels for temperature (100, 130 and 160°C), feed moisture content (15, 22.5 and 30%), and residence time (60, 75 and 90 s). The performed study revealed that the level of incorporation of both FFSF and MOLP, and feed moisture content have significant effects on the expansion ratio, water solubility index and water absorption index of the extrudates. It was concluded that the role of processing conditions and blending levels have a significant contribution to the quality characteristics of the soy-moringa expanded snacks.

Role of process conditions on the microstructure, stoichiometry and functional performance of atmospheric plasma sprayed La(Sr)MnO3 coatings

Strontium doped lanthanum manganite (LSM) perovskite coatings were produced via atmospheric plasma spray technique to examine their applicability as electrically conductive coatings to protect chromium-poisoning of cathode side metallic interconnects in solid oxide fuel cells. Various plasma spray process conditions were manipulated including plasma power, total gas flow and content of H2 in the plasma gas in order to understand their effects on coating properties as well as efficacy as a protectant against Cr-poisoning. In-flight temperatures and velocities of spray particles were monitored for the various plasma spray conditions enabling assessment of thermal and kinetic energies of LSM particles. As anticipated, coating density improves with increasing thermal and/or kinetic energies of the LSM particles. However, the LSM particles also experienced significant phase decomposition at higher thermal exposure and longer residence time conditions. Due to preferential loss of oxygen and manganese, La2O3 phase is also formed under certain processing regimes. The resultant mixed-phase coating is ineffective both from electrical transport and as a protective coating for the metallic interconnect. Concomitantly, coatings with limited decomposition show excellent conductivity and protection characteristics demonstrating the need for mechanism driven process optimization for these functional oxide coatings.

The Relation Between Molecular Packing or Morphology and Chemical Structure or Processing Conditions: the Effect on Electronic Properties

In the past few decades, mainly two kind of organic semiconductors, namely small molecules and polymers, have been dealt with. It turns out that the difference between these two categories in terms of charge carrier transport arises from the potentially different morphologies and the molecular packing. There are many studies showing the effect of the chemical structure on the electronic properties. However, in this study, the focus is on the role of processing conditions which is found to be of at least equal importance. To study a range of morphologies and packing in as similar molecules, two systems prepared by “Click”‐type chemistry are chosen, with the major difference between them being the replacement of a flat unit with one that introduces a slight twist to the aromatic skeleton. Through AFM and X‐ray studies, it is shown that the molecule with the potentially flat geometry can exhibit a high degree of π–π stacking, leading to morphologies ranging from polycrystalline to single crystals while the other is always in the amorphous film state. The transport properties are compared using organic field effect transistor (OFETs) in both top and bottom contact configurations.

The Effect of a Rapid Heating Rate, Mechanical Vibration and Surfactant Chemistry on the Structure-Property Relationships of Epoxy/Clay Nanocomposites.

The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy) to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave manufacturing process equipped to generate rapid heating rates and mechanical vibration. The results suggested that the quaternary ammonium surfactant on C30B clay reacted with the epoxy during cure, while the primary ammonium surfactant (I.30E) catalysed the polymerisation reaction. These effects led to important differences in nanocomposite clay morphologies. The use of mechanical vibration at 4 Hz prior to matrix gelation was found to facilitate clay dispersion and to reduce the area fraction of I.30E clay agglomerates in addition to increasing flexural strength by over 40%.

Green synthesis of silver nanoparticles using Beta vulgaris: Role of process conditions on size distribution and surface structure

The present work reports the green synthesis of silver nanoparticles, using Beta vulgaris peel extract with a subsequent investigation on the size distribution and surface structure of nanoparticles formed under various process conditions. The green-chemical reduction mechanism of silver ions to nanoparticles by the active organic functional groups present in the extract was characterized, using the respective spectroscopic techniques. The effects of various process parameters, including induced intraparticle ripening, were attributed to the controlled formation of anisotropic silver nanoparticles within the supporting matrix of the extract. The plasmon absorption and resonance scattering properties were expected to be favourable for small and larger size nanoparticles (below 25 nm and above 75 nm) respectively, which was considered to be an indicative aspect for synthesizing nanoparticles of narrow size distribution. The zeta potential and dynamic light scattering (DLS) results suggest the good stability and mono-dispersed size distribution of the silver nanoparticles. The transmission electron microscope, selective area electron diffraction (SAED) and X-ray diffraction studies infer that the nanoparticles formed were spherical/quasi-spherical in shape, which primarily exhibited a face centred cubic crystal (FCC) structure. The green-chemical reduction of organic phases in the extract (especially amine (NH2) groups) as reflected through shifts observed in the Fourier-transform infra red (FTIR) peaks, reveal the possible interaction of the organic molecules with the silver ions in the effective formation, surface modification and stabilization of the silver nanoparticles.

Role of Phase Morphology on the Damage Initiated Self‐healing Behavior of Ionomer Blends

AbstractThe development of self‐healing materials, based on polymer blends, is an important issue either from a scientific or a technological point of view. The application of such materials can be remarkably extended if healing effects can be maintained even in polymers that are modified in order to tune their physical and mechanical behavior. In this research the self‐healing behavior of blends made of ionomers (sodium and zinc salts of poly(ethyelene‐co‐methacrylic acid)—EMNa and EMZn) with functionalized elastomers (epoxidized natural rubber with different epoxidation levels—ENR50 and ENR25, polyisoprene—PISP) of different compositions is investigated. The role of processing conditions, phase morphology, functionalization level, polymers compatibility over self‐healing response are discussed. Rubber functionality and phase dispersion are recognized as crucial factors affecting the healing efficiency of blends. Results of ballistic tests, DSC thermal analysis, FTIR spectroscopy, optical and electron (SEM and TEM) microscopy observations, rheological and mechanical tests are presented as supporting evidences.

AlN thin films prepared by ArF plasma assisted PLD. Role of process conditions on electronic and chemical–morphological properties

Aluminium nitride thin films were deposited on n-Si substrates by RF plasma activated reactive pulsed laser deposition (PLD). An ArF excimer pulsed laser, 10 Hz and 2.5 J/cm2 energy fluence, has been used to ablate a pure Al target in a reactive atmosphere of N2 plasma (generated by a RF source), at varying processing parameters (substrate temperature, time, and N2 plasma configuration). We studied the dependence and correlation of structural and electronic properties with the experimental conditions. The chemical composition of deposited material has been determined by both Raman and X-ray photoelectron spectroscopy (XPS). Electrical resistivity has been evaluated by the sheet resistance method. Both spectroscopic characterizations (Raman and XPS) show a strong dependence in the formation of AlN on the deposition temperature. At low temperatures, there is little formation of nitride, with a prevalence of aluminium oxide, while at higher temperatures the N uptake increases, with AlN formation. Raman analysis also highlights the formation of nano-structures, for temperatures ≥400∘C. These material characteristics have a fundamental influence on the electronic properties. Indeed, electrical resistivity properties have been found to be strongly dependent on the film structure, nitrogen incorporation, and presence of mixed oxide compounds, closely related to deposition temperature.

The Role of Processing Conditions on the Color and Antioxidant Retention of Jet Tube Fluidized Bed–Dried Blueberries

Jet tube fluidized bed drying was investigated as a means of rapidly generating shelf-stable and high-quality sweetened and nonsweetened blueberries. Sugar-infused and noninfused scarified Rabbiteye blueberries (Vaccinium ashei ‘Brightwell’) were dried at 99, 107, and 116°C. Prior scarification of the blueberry surface aided in decreasing the drying time. Increased lightness (L*) values were most notable at higher drying temperatures for sugar-infused blueberries, suggesting loss of pigments. Total monomeric anthocyanins level, initially 7.65 mg cyanidin-3-O-glucoside equivalents (C3G eq)/g extract, decreased as drying temperature increased and ranged between 4.07 down to 1.51 mg C3G eq/g extract for dried blueberries. The total phenolics content increased with drying for noninfused blueberries, with highest levels of 31.6 mg gallic acid equivalents (GAE)/g extract for samples dried at 107°C. With the exception of sugar-infused berries dried at 107 and 116°C, the dried blueberries maintained or demonstrated slightly increased hydrophilic oxygen radical absorbance capacity (H-ORACFL) values, indicating that their antioxidant capacity was retained upon drying. Blueberries dried at 107°C possessed the greatest preference scores and best retention of blueberry flavor and required a relatively short drying time.

Equivalence between polymer nanocomposites and thin polymer films: Effect of processing conditions and molecular origins of observed behavior

Recently we established a quantitative equivalence in thermomechanical properties between polystyrene-silica nanocomposites and planar freestanding polystyrene thin films. This equivalence was quantified by drawing a direct analogy between film thickness and an appropriate experimental particle spacing. Using these findings, here we unequivocally show that the glass transition process in confined geometries is controlled by the mean volume fraction of polymer that is affected by the presence of surfaces. Since separate signatures of the bulk and the surface layers are never found, we can clearly rule out any simple “two layer” model which postulates the existence of surfaces which are dynamically decoupled from the bulk. Rather, we argue that the modification of properties at the surfaces propagates into the bulk through a spatial gradient: macroscopic experimental techniques average over these gradients and yield a broadened signature relative to the bulk polymer. In a second aspect of this paper we focus on the role of processing conditions on the results obtained. We have developed a new method of processing the nanocomposites which results in a better dispersion of the nanoparticles in the matrix. However, these samples did not show the unique glass transition behavior seen in the first set of nanocomposites discussed above. This indicates that processing conditions can profoundly affect the nature of the particle-polymer interface which controls the macroscopic behavior of these important systems.

The Effect of Orientation on Extrusion Cast Metallocene Polyethylenes and the Role of Processing Conditions in the Die Swell of Metallocene and Conventional Polyethylenes

AbstractCast films were prepared from a range of metallocene polyethylenes (mPEs) of varied co‐monomer types (hexene, octene) using a Killion single‐screw extruder, using different haul off speeds (8–4 m/min) and die gaps (700–250 m̈m). Samples with greater orientation in one direction had increased tensile strength and shrinkage in that direction. DSC analysis showed crystallinity to decrease with decreasing haul of speed. Extrusion of mPEs and conventional linear low density polyethylenes (LLDPEs) by single capillary rheology showed that die swell increased with increasing extrusion rate and decreasing melt temperature. Increased die swell was found for the broader molecular weight distribution (M.W.D.) LLDPEs and in the higher molecular weight resins. Furthermore, long chain branching was found to increase die swell.