Effects Of Fabrication Parameters Research Articles

Examining the Water Vapour Transmission of Socks

The present study investigated effects of fabric parameters on the water vapor transmission of socks fabric, which was measured by the cup method. It was found that the water vapor transmission of fabric was negatively proportional to the content of cotton and yarn count, before washing. Meanwhile, washing was found to increase the water vapour transmission.

Investigation of thermal property of spark plasma sintered Ti-Zr-Ta shape memory alloys

There is increasing demand for the performance improvement of novel shape memory alloys (SMAs), such as the Ti-Zr-based systems. The effects of fabrication parameters and material compositions are critical to the thermal properties of the alloys. This study is designed to investigate the effects of ternary Ta additions on the thermal properties of spark plasma sintered (SPSed) novel Ti-Zr based SMAs for high temperature applications. The SPSed Ti-Zr/Ta specimens were characterized for their microstructural and crystallographic features using scanning electron microscopy (SEM) incorporated with Energy Dispersive X-ray Spectroscopy (EDS), and X-ray powder diffractometry (XRD). Thermal property measurements were conducted using the Laser Flash technique to obtain the thermal diffusivity behaviour, while the phase transformation properties were determined by the differential scanning calorimetry (DSC). The presence of both alpha martensite, and beta structures were revealed by the SEM/EDX and XRD respectively. High thermal diffusivity values were obtained, and they show an increasing trend with temperature. The DSC measurement revealed high reversible martensitic transformation (above 200 deg Celcius) for all the alloys, a two-stage phase transformation in the binary alloy, and a single-phase transformation event in the ternary alloys. A downward parabolic gradient of the specific heat and thermal conductivity with respect to temperature was recorded in the alloys, thus revealing an interaction between phonon-mediated and electron-mediated thermal transport processes. Two-stage phase transformations, noticed in the binary alloy indicate the reversible transformation events of alpha-Ti and alpha-Zr phases at different temperatures to-and-fro the austenite phase, whereas, in the ternary phase the single transformation event indicates the presence of only alpha-Ti phase. These results further strengthen the understanding of material atomic compositions effect on the thermal behaviour of the as-sintered alloys. The high thermal diffusivity and high martensitic transformation behaviour of the Ti-Zr/Ta alloys suggest they can be suitable candidates for high temperature applications in the aerospace technologies.

Lanthanum tungstate membranes for H2 extraction and CO2 utilization: Fabrication strategies based on sequential tape casting and plasma-spray physical vapor deposition

In the context of energy conversion efficiency and decreasing greenhouse gas emissions from power generation and energy-intensive industries, membrane technologies for H2 extraction and CO2 capture and utilization become pronouncedly important. Mixed protonic-electronic conducting ceramic membranes are hence attractive for the pre-combustion integrated gasification combined cycle, specifically in the water gas shift and H2 separation process, and also for designing catalytic membrane reactors. This work presents the fabrication, microstructure and functional properties of Lanthanum tungstates (La28−xW4+xO54+δ, LaWO) asymmetric membranes supported on porous ceramic and porous metallic substrates fabricated by means of the sequential tape casting route and plasma spray-physical vapor deposition (PS-PVD). Pure LaWO and W site substituted LaWO were employed as membrane materials due to the promising combination of properties: appreciable mixed protonic-electronic conductivity at intermediate temperatures and reducing atmospheres, good sinterability and noticeable chemical stability under harsh operating conditions. As substrate materials porous LaWO (non-substituted), MgO and Crofer22APU stainless steel were used to support various LaWO membrane layers. The effect of fabrication parameters and material combinations on the assemblies’ microstructure, LaWO phase formation and gas tightness of the functional layers was explored along with the related fabrication challenges for shaping LaWO layers with sufficient quality for further practical application. The two different fabrication strategies used in the present work allow for preparing all-ceramic and ceramic-metallic assemblies with LaWO membrane layers with thicknesses between 25 and 60 μm and H2 flux of ca. 0.4 ml/min cm2 measured at 825 °C in 50 vol% H2 in He dry feed and humid Ar sweep configuration. Such a performance is an exceptional achievement for the LaWO based H2 separation membranes and it is well comparable with the H2 flux reported for other newly developed dual phase cer-cer and cer-met membranes.

Evaluation of Reverse Microemulsion Parameters Over the Catalytic Performance of Promoted Fe–Co Catalysts for the Production of Light Olefins from Syngas Using Box–Behnken Design

In this study, Mn and K promoted Fe–Co nanocatalysts supported on MgO were synthesized via microemulsion technique, and the effect of fabrication parameters (aging time, precursor concentration and annealing temperature) on the performance of the catalyst in Fischer–Tropsch synthesis was assessed. For precise assessment of individual and interaction effects of fabrication factors on light olefins selectivity, the Box–Behnken design was applied. The results demonstrated that the attained quadratic equation appropriately fitted the experimental data. With regards to the fitted model, the effective parameter on light olefins selectivity was determined (annealing temperature). To elucidate in detail the relationship between annealing temperature and catalyst performance, XRD, BET, FESEM, ICP, H2-TPR and CO-TPD characterization techniques were performed. The observations from the used characterizations of catalyst demonstrated that an increase in annealing temperature led to the creation of mixed metal oxide which had difficult reduction conditions and demonstrated more stable CO adsorption. The results demonstrated that the formation of mixed metal-support interaction had a positive synergistic effect on the O/P ratio.

Experimental investigation and mathematical modeling of nano‐composite membrane fabrication process: Focus on the role of solvent type

In this study, the effect of fabrication parameters on the performance of nano-SiO2-embedded membranes fabricated by three prevalent solvents was investigated. Genetic programming was applied for modeling and estimating the best preparation conditions to obtain a proper membrane for oily wastewater microfiltration. Membranes were prepared via a combination of vapor-induced phase separation and nonsolvent-induced phase separation methods. Different types of solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl formamide, and dimethyl sulfoxide were used in cooperating with SiO2 nanoparticles to improve hydrophilicity properties of polyethersulfone. Thermodynamic behavior of solvents and their interaction with polymer and nonsolvent were considered as criteria for forming a suitable membrane with the maximum effectiveness of nanoparticles. The results showed that nanoparticles are more influential along with a solvent that has a weak affinity with a polymer, which subsequently can produce efficient membranes under conditions with a balance between exposure time and relative humidity. The optimum amounts of parameters were estimated by genetic algorithm to introduce a condition for having a membrane with the maximum permeate flux. Membranes fabricated with dimethyl sulfoxide represented the highest pore size and the most hydrophilic surface, which, in turn, led to the desired membrane (permeate flux 300L/m(2)hr and oil rejection 97%).

Effect of Fabrication Parameters and Material Features on Tensile Strength of FDM Built Parts

This paper presents experimental investigations on influence of fabrication parameters and material features viz., layer thickness, build orientation, processing material and processing quality on tensile strength of parts built by fused deposition modelling (FDM). The specimen is designed according to GB/T 1040.2/1BA/1 which maintains the tensile strength test. And the experimental factor levels are setup on account of the fabrication parameters and processing materials of the processing equipment for FDM. Then Taguchi’s parameter design is applied to find optimum factor levels to maximize the tensile strength of FDM built parts. As the experiment plan is designed base on orthogonal test design with mixed levels, tensile strength of each test is obtained and the signal to noise ratio which defined to evaluate the influence and variation is obtain as well. Then main effect plot is drawn and analysis of variance is performed to find optimal level of fabrication parameters to maximize the tensile strength of FDM built parts. Finally, the effect of fabrication parameters and material features on tensile strength of FDM built parts are obtained.

Characterization and modelling of thermal protective performance of fabrics under different levels of radiant-heat exposures

The investigation of thermal protective performance of fabrics is highly relevant in order to procure and further develop the firefighters' protective clothing. Therefore, this paper aims at investigating the thermal protective performance of fabrics used in firefighters' clothing under different levels of radiant-heat exposures. For this, properties of a set of thermal protective single- and multi-layered fabrics were measured, and these fabrics were tested under radiant-heat exposures using the Method B of ISO 6942:2002 standard. During the testing, fabrics were exposed to low (10 kW/m2), medium (40 kW/m2), and high (80 kW/m2) intensity radiant-heat exposures; and the heat transfer level (i.e., time required to increase the skin temperature of a wearer/firefighter by certain degrees) through these fabrics were calculated to measure their thermal protective performance. The effects of fabric parameters, structures, properties, and radiant-heat intensities on the protective performance were characterized, and fabric properties that significantly affected the protective performance were statistically identified at different level of radiant-heat exposures. It has been found that weight, thickness, thermal resistance, and evaporative resistance can positively affect the protective performance. Also, the significant fabric properties affecting the protective performance vary for single- and multi-layered fabrics. By using these significant properties, the protective performance of single- and multi-layered fabrics were also separately predicted by mathematical models, i.e., multiple linear regression models and multiple logarithmic regression models. As per the findings of this study, multiple linear regression models can effectively be used to predict the thermal protective performance of fabrics. This study will lead towards building a better understanding and prediction of thermal protective performance of fabrics under radiant-heat exposures.

Silk fibroin from silk fibrous waste: characterization and electrospinning

In this work, the effect of fabrication parameters on silk fibroin (SF) nonwovens obtained by electrospinning were evaluated. Additionally, the relationship between secondary structures and thermal stability of the protein materials, with morphological characteristics of nonwovens obtained were analyzed. Silk fibroin in formic acid solution at 10% w/w was electrospun at 8 cm varying the ratio voltage/distance and flow rate. The nonwovens morphology was observed by Scanning Electron Microscopy (SEM) and fibers diameter were determined with ImageJ software. The changes in the secondary structure of silk fibroin before and after electrospinning were studied by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) to evaluate the effect of electrospinning process in the molecular structure of SF. Optimum morphology of SF nonwovens were obtained at R = 1 kV/cm and low flow rate, these process parameters were related to higher contents of crystalline structures in the materials. Results showed that SF nonwovens obtained under controlled process parameters hold great potential to be utilized in several applications such as tissue engineering.

Research on surface nano-texturation and wet-chemical passivation of multi-crystalline silicon wafer

Surfaces nano-texturing has triggered off much attention for trapping sunlight to improve the efficiency of solar cells. Silicon nanowire (SiNWs) arrays, with excellent antireflection performance, will hopefully improve photoelectric conversion of solar cells, however, the deteriorated effective carrier lifetime seriously limits efficiency enhancement of solar devices. Until now, the effect of SiNWs structure on effective carrier lifetime remains unexplored. Herein, the effects of fabrication parameters on the morphology structure and effective carrier lifetime of textured mc-Si were studied in detail. We also firstly discover that the relationship of SiNWs arrays length and effective carrier lifetime shows the negative exponential relation. Moreover, the effects of ethanolic iodine (I–E) concentration, immersion time, and surface pre-conditioning (with and without native oxide) on surface passivation of SiNWs arrays were investigated. It is found that more effective surface passivation could be achieved for the SiNWs arrays with shorter length. Meanwhile, the HF dipping pretreatment is conducive for SiNWs passivation, and which is attributed to Si–Hx termination with lower dissociation energy.

Low Velocity Impact Behavior of Basalt Fiber-Reinforced Polymer Composites

In this research, we studied low velocity impact response of homogenous basalt fiber-reinforced polymer (BFRP) composites and then compared the impact key parameters with carbon fiber-reinforced polymer (CFRP) homogenous composites. BFRPs and CFRPs were fabricated by vacuum-assisted resin transfer molding (VARTM) method. Fabricated composites included 60% fiber and 40% epoxy matrix. Basalt and carbon fibers used as reinforcement materials were weaved in 2/2 twill textile tip in the structures of BFRP and CFRP composites. We also utilized the energy profile method to determine penetration and perforation threshold energies. The low velocity impact tests were carried out in 30, 60, 80, 100, 120 and 160 J energy magnitudes, and impact response of BFRPs was investigated by related force-deflection, force-time, deflection-time and absorbed energy-time graphics. The related impact key parameters such as maximum contact force, absorbed energy, deflection and duration time were compared with CFRPs for various impact energy levels. As a result, due to the higher toughness of basalt fibers, a better low velocity impact performance of BFRP than that of CFRP was observed. The effects of fabrication parameters, such as curing process, were studied on the low velocity impact behavior of BFRP. The results of tested new fabricated materials show that the change of fabrication process and curing conditions improves the impact behavior of BFRPs up to 13%.

Osmogen-Mediated One-Step Technique of Fabricating Hollow Microparticles for Encapsulation and Delivery of Bioactive Molecules.

Microparticulate systems composed of biodegradable polymers, such as poly(d,l-lactic-co-glycolic acid) (PLGA), are widely used for controlled release of bioactive molecules. However, the acidic microenvironment within these microparticles, as they degrade, has been reported to perturb the configuration of most encapsulated proteins. In addition, these polymer particles are also reported to suffer from unrealistically slow and incomplete release of proteins. To address these drawbacks, hollow PLGA microparticles are fabricated through a novel one-step oil-in-water emulsion solvent evaporation technique, by capitalizing on the osmotic property of an osmogen. The effects of fabrication para-meters on particle size and morphology, i.e., volume space of hollow cavity and shell thickness, are also studied. These hollow microparticles are subsequently loaded with bovine insulin microcrystals. It is shown that insulin release profiles can be tuned by simply changing the amount of osmogen in the formulation. At the same time, these hollow microparticles are shown to be effective in maintaining the bioactivity of the encapsulated protein.

Fabrication of rigid poly(lactic acid) foams via thermally induced phase separation

Rigid poly(lactic acid) (PLA) foams were prepared by thermally induced phase separation followed by solvent exchange and vacuum drying. A novel tetrahydrofuran (THF)/water solvent system was used for the induction of liquid-liquid phase separation of PLA solution at three different temperatures; 24 °C, 4 °C and −20 °C. PLA gels obtained were mechanically stabilized by replacing THF/water solvent mixture with ethanol nonsolvent. Characterization of rigid PLA foams was obtained by scanning electron microscopy, mercury intrusion porosimetry, x-ray diffractometry, infrared spectroscopy and differential scanning calorimetry analyses. Effects of fabrication parameters on the morphology and pore structure were systematically examined. The parameters investigated included; (i) polymer concentration, (ii) THF/water ratio and (iii) quench temperature. Results showed that degree of porosity and the morphology of the pores, such as the pore size and shape could be controlled by tuning the fabrication parameters. By controlling the degree of phase separation of PLA solution, foams with dual micro and nano structures were obtained.

Preparation and characterization of inner-pressure hollow fiber composite membrane via two-way coating technique for CO2/CH4 separation

High-selectivity inner-pressure hollow fiber composite (HFC) membrane for CO2/CH4 separation was prepared through the Two-way coating (TWC) technique. The blends of poly(vinylamine) (PVAm)/polyvinyl alcohol (PVA) were coated onto porous hollow fiber polysulfone (PSF) ultrafiltration (UF) membrane with an effective membrane area of 0.4 m2. The effects of fabrication parameters on the permselectivity of the resultant HFC membrane were investigated and the optimum preparation conditions were obtained as follows: coating time for 30 min and air blowing time for 30 min after the coating. The prepared HFC membrane showed the typical characteristic of fixed carrier membrane with a high selectivity of CO2 and CH4: the separation factor of CO2/CH4 (40 vol% CO2 at 25 °C and 0.2 MPa) was 36.6 and the CO2 permeability was 56.3 GPU. Field emission scanning electron microscopy (FESEM) images indicated that the HFC membrane prepared by TWC technique had a uniform coating layer along the whole hollow fiber. Membrane permselectivity showed almost no difference between different membrane sections. The HFC membrane showed a good stability during the continuous testing process of 540 h. And the HFC membrane preserved at 30 °C and 40 % humidity exhibited a good durability with a basically unchanged separation factor after 30 days.

Fabrication of graphite film/aluminum composites by vacuum hot pressing: Process optimization and thermal conductivity

Abstract Effective thermal management is becoming increasingly important for high power density electronic devices, which requires materials with high thermal conductivity. A novel graphite film/aluminum composite material with ultrahigh thermal conductivity was fabricated by vacuum hot pressing process to meet this requirement. The effects of fabrication parameters on microstructures and thermal conductivities of these composites were investigated. As a result, the composites with graphite volume fraction of 17.4–69.4% sintered at 655 °C/45 MPa for 100 min exhibit in-plane thermal conductivities of 380–940 W/mK, over 90% of the predictions by rule of mixture. These composites possess higher in-plane thermal conductivities than graphite flake/aluminum composites due to well-controlled graphite orientation and fabrication parameters, which indicates that these composites are promising materials for effective thermal management.

Investigation on Impact Behavior of Rice Husk Impregnated Coir‐Vinyl Ester Composites

SummaryThe use of natural fibers and bio‐particles as reinforcement in polymeric composites is gaining keen interest in the field of cellulose based composite materials, due to its attractive properties such as light weight, low cost and biodegradability etc. Several studies in the past have reported major improvement in the mechanical behaviors of fiber reinforced polymer composites by impregnating bio‐particulate with the matrix system. This investigation is aimed at introducing a hybrid reinforcement based polymer composites which uses rice husk as bio‐particles and green husk coir as fibrous reinforcement. The composite sheets were fabricated as per full factorial design of experimental plan by varying the fabrication parameters namely fiber length, fiber content and particulate content. The effects of fabrication parameters on the impact properties of the composites were analyzed and favorable conditions to yield better impact strength were determined. The X‐ray diffraction and Scanning electron microscopy techniques were used to characterize the bindability of rice husk and coir fibers in the resin system. A major improvement in the impact properties was inferred on impregnating rice husk bio‐particles in coir‐vinyl ester composites.

Structure and antireflection properties of SiNWs arrays form mc-Si wafer through Ag-catalyzed chemical etching

A simple and low cost MACE method was demonstrated for efficiently texturing commercial mc-Si wafer at room temperature. The effects of fabrication parameters (deposition time, HF concentration, H2O2 concentration, and etching time) on the morphology structure, antireflection property of textured mc-Si were carefully studied. The large scale SiNWs arrays with different structure can be obtained under various fabrication conditions. Meanwhile, the results indicate that the fabricate parameters have important effect on the reflectance of textured mc-Si sample in the order of etching time>deposition time>H2O2 concentration>HF concentration. The comprehensive research results indicate that it is more beneficial for the nanowire arrays with tapering structure and the length of 13μm to obtain excellent antireflection property. Under these optimization conditions, the textured mc-Si shows an outstanding anti-reflectance ability of ∼5.6%, which indicates that the Ag-catalysis etched mc-Si shows a huge potential application in high-efficiency polysilicon solar cells.

Effects of Fabric Parameters and Initial Moisture Content on the Smoothness Appearance of Woven Cotton Fabrics in Dryer

The effects of fabric parameters and initial moisture content in dryer on the smoothness appearance of woven cotton fabrics have been determined. In this study, 11 kinds of cotton fabrics were selected to evaluate their smoothness appearance after drum drying. The results indicated that the fabric parameters---surface density, thickness and warp density--- had a certain correlation with the fabric smoothness appearance, which wasn’t significant. The initial moisture content affected smoothness appearance positively. With the increasing of initial moisture content, the grade improved and the difference between the max and the mini is about 0.5grade. This study can provide a reference for the design of the dryer program and make fabric washing process achieve the coordination with drying process to obtain a best fabric appearance.

The Microstructure and Mechanical Properties of Porous Silicon Nitride Ceramics Prepared via Novel Aqueous Gelcasting

A novel aqueous gelcasting technique was employed to prepare porous silicon nitride ceramics using water‐soluble copolymer of isobutylene and maleic anhydride (Isobam) as both dispersant and gelling agent. The effects of fabrication parameters, including sintering additives, the second phase (BN), and pore‐forming agent (corn starch), on the microstructure and mechanical properties were separately investigated. The sample with Yb2O3 as sintering additive, having a porosity of ~48.6%, showed a high flexural strength of 233MPa and a high fracture toughness of 2.72 MPa·m1/2. With addition of 2.5wt% BN, the sample exhibited a high flexural strength of 211 MPa due to the uniform microstructure with β‐Si3N4 grains. A high porosity of ~60% and a flexural strength of 110 MPa were obtained by adding 20wt% starch into the sample.

Fabrication and Biological Properties of Bionic Structure Porous Alumina Ceramics with Spherical/Lamellar Pores

In order to solve the problem that low pore connectivity of the spherical porous ceramic, bionic structure porous alumina ceramics with spherical/lamellar pores were fabricated combining the adding pore-forming agent and two step freeze casting. The effects of fabrication parameters of the samples on morphologies, porosity and pore connectivity are investigated. The mechanical and biological properties of bionic structure porous alumina ceramics are also characterized. Results show that porous alumina ceramics with spherical/lamellar pores are obtained, and the lamellar pores pass through the spherical pores, which prove the pore connectivity reach 86.2 %. The mechanical properties are improved by porosity gradient from the inside (highly porous) to the outside (less porous) of porous alumina. Bionic structure porous alumina ceramics with spherical/lamellar pores have better cell growth and absorbance than those with spherical or lamellar pores only since its high pore connectivity.

Impregnation of porous mullite with Na2SO4 phase change material for thermal energy storage

The porous mullite/Na2SO4 composites with both novel structure and improved heat storage properties were successfully prepared by infiltration of the molten Na2SO4 into the porous mullite matrix, which was fabricated by TBA-based freezing casting method. The effects of fabrication parameters on pore structure of the porous mullite matrix, the infiltration ratio of molten Na2SO4 and heat storage properties of the composites were investigated extensively. The results show that the infiltration ratio of the molten Na2SO4 decreases with decreasing the porosity and increasing the infiltration temperature and the average pore size of the porous mullite matrix. While it increases initially with increases of the infiltration time, and tends to remain constant thereafter. The optimal infiltration temperature and infiltration time are 950°C and 1h, respectively. The unidirectionally aligned open pores in the porous mullite matrix benefit the infiltration process, and the higher infiltration ratio of the molten Na2SO4 and the relatively larger specific heat capacity of the mullite powders both contribute to the higher heat storage density of the composites.