Optimum Fabrication Conditions Research Articles

EFFECTS OF MEMBRANE FABRICATION CONDITIONS TOWARDS THE PERFORMANCE OF NANOPARTICLES-INCORPORATED MEMBRANES

The development of nanoparticles-incorporated membranes is one of the recent techniques in improving membrane qualities in terms of fouling propensity. In this study, Zinc oxide (ZnO) has been selected as the nanoparticles to be embedded in membranes due to its excellent antifouling and antimicrobial properties. Several parameters such as polymer percentage and bath temperature were studied during the membrane fabrication process via phase inversion technique. The effects of each parameter towards the membrane structure and performance were significant in producing good membranes. When the polymer percentage increased from 16wt% to 20wt%, the permeability decreased from 6.9 to 3.9 L.m-2.hr-1.bar-1 and humic acid rejection increased from 78% to 95%. On the other hand, the coagulation temperature increment will lead to increment of permeability from 2 to 4 L.m-2.hr-1.bar-1 but gave rejection from 93% to 96% at 15oC to 25oC, and 86% at temperature of 35oC.In conclusion, the optimum condition for nanoparticles-incorporated membranes fabrication was shown at 20% of PSF at 25oC.

Probing the Cost-Effective Sodium Doped Strontium Silicate (Sr1-xNaxSiO3-0.5x) as Solid Electrolytes for IT-SOFC

The urgency for clean and secure energy has stimulated a global resurgence in searching foradvanced electrical energy conversion systems. Solid oxide fuel cells (SOFC) have been considered as one of the most promising electro-chemical energy conversion technologies due to their high efficiency, low emission, and excellent fuel flexibility. The most widely used electrolyte materials are fluorite structured yttria stabilized zirconia (YSZ). However, use of YSZ is limited because of the limiting magnitude of the electrical conductivity and its high operating temperature over 800 °C. Recently, the sodium doped strontium silicate (Sr1-xNaxSiO3-0.5x) is gathering attentions as a fast ion conductor [1]. And Wei et al. confirmed a good SOFC performance using this electrolyte material at 500 and 600 °C [2]. In this study, we investigated this promising material to get the optimal fabrication conditions with composition and to minimize degradation problems and also enhance the stability on this material. From this study, we found out the optimal fabrication conditions (sintering at 900 °C for 10 h) for 40 % sodium doped strontium silicate electrolyte which was known as the best ionic conductor. Thermal behaviour of the compositions has also been investigated for the applicability as solid electrolyte. Moreover, for the higher doping concentration (>40 %); a decrease in the electrical conductivity is observed. This decrease in the conductivity may be due to the formation of impurity phases of sodium silicate. Keywords: SOFC; Electrical conductivity; solid electrolyte; strontium silicate.

Optimization, synthesis, and characterization of coaxial electrospun sodium carboxymethyl cellulose-graft-methyl acrylate/poly(ethylene oxide) nanofibers for potential drug-delivery applications

In this study, nanofiber drug carriers were fabricated via coaxial electrospinning, using a new, degradable core–shell nanofiber drug carrier fabricated via coaxial electrospinning. Fabrication of the shell was carried out by graft polymerization of sodium carboxymethyl cellulose (NaCMC) with methyl acrylate (TCMC) and poly(ethylene oxide) (PEO). Tetracycline hydrochloride (TCH) was used as a drug model incorporated within the nanofibers as the core, and their performance as a drug carrier scaffold was evaluated. The loading of TCH within PEO nanofibers and the loading of TCH within the TCMC nanofibers were characterized via different techniques. The structure morphology of the obtained nanofibers was viewed under scanning electron microscope (SEM). The changes in the polymer structure before and after grafting and confirmation of incorporation of the drug in the fibers were characterized by Fourier transform infrared spectroscopy (FT-IR). Response surface methodology (RSM) was applied to predict the optimum conditions for fabrication of the nanofibers. The cell viability of the optimized samples was assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The TCH loaded into the optimized core–shell sample of TCMC 3% (w/v)/PEO 1% (w/v) had a smooth and beadless morphology with a diameter of 86.12nm, slow and sustained drug release, and excellent bactericidal activity against a wide range of bacteria. This shows promise for use as an antibacterial material in such applications as tissue engineering and pharmaceutical science.

Chromium removal using adsorptive membranes composed of electrospun plasma-treated functionalized polyethylene terephthalate (PET) with chitosan

Removal of hexavalent chromium from water resources via an adsorptive membrane was studied. The nanofibrous membrane was prepared by electrospinning of PET bottle wastes. The obtained nanofibrous PET was treated by cold plasma and functionalized by chitosan. Adsorptive properties of the prepared membrane were studied for removal of Cr (VI) from contaminated water. Effects of some important functionalization parameters, i.e. time and power of plasma applied and concentration of chitosan on the adsorption affinity of the functionalized membrane were investigated and optimum fabrication conditions were determined statistically by Taguchi method. The effect of water pH on adsorption capacity and reusability of the prepared membrane was evaluated. The adsorption experimental data obtained revealed that the membrane prepared by application of 900W plasma treatment for the duration of 5min and 1% w/v chitosan concentration had maximum Cr(VI) removal capacity (5.54mg/50mg membrane) at pH of 4. The obtained results showed that functionalized chitosan membrane with plasma treatment had higher adsorption capacity compared to functionalized chitosan membrane without plasma treatment and neat nanofibrous PET. Desorption and reusability experiments showed that the adsorption effectiveness of the prepared membranes could be maintained at 93.7% of fresh membrane after five cycles.

Electrospinning of thermoplastic carboxymethyl cellulose/poly(ethylene oxide) nanofibers for use in drug-release systems

Polymeric delivery systems using electrospun nanofibers have been developed for many applications, notably for drug delivery and tissue engineering in the healthcare industry. In this study, a nanofiber drug carrier was fabricated via two different electrospinning processes, blend and coaxial, using a new degradable thermoplastic carboxymethyl cellulose (TCMC) and poly(ethylene oxide) (PEO). The TCMC was synthesized by graft copolymerization with methyl acrylate. Tetracycline hydrochloride served as a drug model incorporated within these nanofibers and their performance as a drug-carrier scaffold was evaluated. The structure morphology of the obtained nanofibers was viewed under scanning electron microscope, and the changes of the structural of polymer before and after graft and confirmation of incorporation of the drug on the fibers was characterized by Fourier transform infrared spectroscopy. Response surface methodology was applied to predict the optimum condition for fabrication of the nanofibers. The drug-delivery profile showed that drug release from the optimized core–shell sample TCMC 3% (w/v)/PEO 1% (w/v) was much slower than for the blend nanofibers and was sustained for 72h with only 26.06% burst release within the first 30min. The drug-loaded TCMC 3% (w/v)/PEO 1% (w/v) core–shell sample nanofibers showed excellent bactericidal activity against a wide range of bacteria, indicating their potential as antibacterial materials in various applications such as tissue engineering and pharmaceutical science.

Fabrication of graphene from graphite by a thermal assisted vacuum arc discharge system

In this study, graphene was fabricated on copper foils using a high temperature furnace embedded in a vacuum arc discharge method. Combining the advantages of chemical vapor deposition and vacuum arc discharge, single-layer graphene can be fabricated at 600 °C base temperature from the mini furnace embedded with a fast heating via the photon radiation from the vacuum arc to 1100 °C on the substrates' surface. The optimal fabrication condition was determined through a series of experiments on ambient pressure, processing time, arc currents, and the cooling process. Observations by scanning electron microscopy, Raman spectroscopy, and optical microscopy showed that the main products were single-layer graphene, which has a uniform thickness across the entire substrate. The results demonstrated that the combination of a vacuum arc with a thermal method that uses graphite as a carbon source provides a low-cost and straight forward method to synthesize graphene films for graphene-based applications.

Fabrication of cell-benign inverse opal hydrogels for three-dimensional cell culture

Inverse opal hydrogels (IOHs) for cell culture were fabricated and optimized using calcium-crosslinked alginate microbeads as sacrificial template and gelatin as a matrix. In contrast to traditional three-dimensional (3D) scaffolds, the gelatin IOHs allowed the utilization of both the macropore surface and inner matrix for cell co-culture. In order to remove templates efficiently for the construction of 3D interconnected macropores and to maintain high cell viability during the template removal process using EDTA solution, various factors in fabrication, including alginate viscosity, alginate concentration, alginate microbeads size, crosslinking calcium concentration, and gelatin network density were investigated. Low viscosity alginate, lower crosslinking calcium ion concentration, and lower concentration of alginate and gelatin were found to obtain high viability of cells encapsulated in the gelatin matrix after removal of the alginate template by EDTA treatment by allowing rapid dissociation and diffusion of alginate polymers. Based on the optimized fabrication conditions, gelatin IOHs showed good potential as a cell co-culture system, applicable to tissue engineering and cancer research.

High Efficiency Inverted Planar Perovskite Solar Cells with Solution-Processed NiOx Hole Contact.

NiOx is a promising hole-transporting material for perovskite solar cells due to its high hole mobility, good stability, and easy processability. In this work, we employed a simple solution-processed NiOx film as the hole-transporting layer in perovskite solar cells. When the thickness of the perovskite layer increased from 270 to 380 nm, the light absorption and photogenerated carrier density were enhanced and the transporting distance of electron and hole would also increase at the same time, resulting in a large charge transfer resistance and a long hole-extracted process in the device, characterized by the UV-vis, photoluminescence, and electrochemical impedance spectroscopy spectra. Combining both of these factors, an optimal thickness of 334.2 nm was prepared with the perovskite precursor concentration of 1.35 M. Moreover, the optimal device fabrication conditions were further achieved by optimizing the thickness of NiOx hole-transporting layer and PCBM electron selective layer. As a result, the best power conversion efficiency of 15.71% was obtained with a Jsc of 20.51 mA·cm-2, a Voc of 988 mV, and a FF of 77.51% with almost no hysteresis. A stable efficiency of 15.10% was caught at the maximum power point. This work provides a promising route to achieve higher efficiency perovskite solar cells based on NiO or other inorganic hole-transporting materials.

Optimization of fabrication condition by evaluating melting and solidification phenomenon of pure copper

Optimization of fabrication condition by evaluating melting and solidification phenomenon of pure copper

Modeling of organic solar cell using response surface methodology

Polymer solar cells have drawn much attention during the past few decades due to their low manufacturing cost and incompatibility for flexible substrates. In solution-processed organic solar cells, the optimal thickness, annealing temperature, and morphology are key components to achieving high efficiency. In this work, response surface methodology (RSM) is used to find optimal fabrication conditions for polymer solar cells. In order to optimize cell efficiency, the central composite design (CCD) with three independent variables polymer concentration, polymer-fullerene ratio, and active layer spinning speed was used. Optimal device performance was achieved using 10.25mg/ml polymer concentration, 0.42 polymer-fullerene ratio, and 1624rpm of active layer spinning speed. The predicted response (the efficiency) at the optimum stationary point was found to be 5.23% for the Poly(diketopyrrolopyrrole-terthiophene) (PDPP3T)/PC60BM solar cells. Moreover, 97% of the variation in the device performance was explained by the best model. Finally, the experimental results are consistent with the CCD prediction, which proves that this is a promising and appropriate model for optimum device performance and fabrication conditions.

Prevention of mold invasion by eco-friendly lignin/polycaprolactone nanofiber membranes for amelioration of public hygiene

Herein, we fabricated highly porous and stretchable electrospun nanofiber membranes using eco-friendly lignin and polycaprolactone polymers, which efficiently prevent mold colonization and invasion in pine sapwood. Membranes of different thicknesses were tested against four species of mold. Membrane thicknesses of above 38 μm were found to completely prevent mold invasion during the 2- and 4-week cultivation periods. The membranes were characterized using various qualitative and quantitative analytical methods, including tensile tests. The optimized fabrication conditions were established to protect wood from mold growth and to accommodate the periodic expansion and contraction of wood without degradation. The mechanically strong and elastic nanofiber membranes enable an assessment of the membrane’s suitability and feasibility as an alternative to the existing wallpapers or paints.

Modified poly(vinyl alcohol)/chitosan blended membranes for isopropanol dehydration via pervaporation: Synthesis optimization and modeling by response surface methodology

ABSTRACTBox–Behnken (BB) design of response surface methodology (RSM) was effectively applied to optimize fabrication conditions of modified poly(vinyl alcohol) (PVA) and chitosan (CS) blended pervaporation (PV) membranes. The PVA/CS membranes were crosslinked either by chemical reaction with glutaraldehyde (GA) or by heat‐treating at different temperatures. The main objectives were to determine the optimal levels of fabricating parameters and also to investigate interactions among the variables. CS content in the blended membranes, concentration of crosslinking agent and heat‐treating temperature were the fabrication parameters, the main effects and interaction effects of which on membrane structure and PV performance toward isopropanol (IPA)/water dehydration were investigated, and for which regression models were established. The modified PVA/CS blended membranes were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) as well as X‐ray diffraction (XRD). It was found that the CS content is the most significant factor influencing flux and separation factor among the three studied variables and the experimental results are in excellent accordance with predicted values from the developed RSM regression models. The RSM results indicated that under preparation conditions of 80 wt % CS in the blended membrane, 0.58 wt % GA concentration, and 77 °C heat‐treating temperature, the maximum separation factor of 5222.8 and the normalized flux of 9.407 kg µm/m2h can be acquired with feed content of 85 wt % IPA at 25 °C, showing that the prepared membrane is highly efficient for PV dehydration of IPA. The models were satisfactorily validated against experimental data. Furthermore, the optimum membrane presents excellent separation performance at different feed compositions and temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44587.

Immune-affinity monolithic array with chemiluminescent detection for mycotoxins in barley.

Mycotoxins are produced by fungi as secondary metabolites. They often multi-contaminate food and feed commodities posing a health risk to humans and animals. Fast and easy multiplex screening could be thought as a useful tool for detection of multi-contaminated food and feed commodities. A highly sensitive immune-affinity monolithic arrays for detecting the mycotoxins zearalenone, deoxynivalenol, T-2 toxin, HT-2 toxin, aflatoxins, ochratoxin A, and fumonisin B1 were fabricated using UV induced co-polymerisation. The mycotoxin antibodies firstly reacted with functional monomer to form antibody/functional monomer bio-conjugates. Subsequently, the antibody/functional monomer bio-conjugates co-polymerised with cross-linker to form mycotoxins immune-affinity arrays. With optimal fabrication conditions, all mycotoxin immune-affinity monolithic arrays exhibited a linear response spanning three orders of magnitude. And the immune-affinity monolithic array has a low detection limit and has a good uniformity (intra-assay CV, and inter-assay CV both <8%). The fabricated mycotoxin immune-affinity monolithic arrays were proved as a sensitive, stable and economical tool in real food samples detection. Moreover, the mycotoxin immune-affinity monolithic arrays would be able to minimise manipulation steps: add samples and enzyme labelled mycotoxins, and detect CL signals. © 2016 Society of Chemical Industry.

Fabrication and characterization of HDPE resins as adhesives in plywood

Demand has been growing for plywood utilizing novel formaldehyde-free wood adhesives which are more durable and require environmental protection and sustainable development during the service life. In this study, a series of HDPE film as novel adhesives in plywood due to many advantages are fabricated using hot-press process followed by cold-press process. The effects of moisture content, HDPE dosage, hot-press temperature and pressure at different levels on physical–mechanical properties were evaluated by tensile shear strength, compression ratio, water absorption and thickness swelling. The results indicated that HDPE film can independently be used as adhesive in plywood, meeting the requirement for type II grade plywood of GB/T 9846.3 (Plywood-part 3: General specification for plywood for general use. Chinese National Committee for standardization, 2004) and opening up a new way for formaldehyde-free adhesives in plywood used as interior grade. Moreover, analysis of variance showed that the most important effect factor on tensile shear strength and water absorption is HDPE layer; on compression ratio and thickness swelling it is moisture content of veneer. To study the optimal hot-press condition, optimization of preparation process for plywood was carried out by response surface methodology analysis (RSMA), and then analysis by Design-Expert software. The simulation results of tensile shear strength were validated by experimental findings, indicating that RSMA can be used as an effective method to predict optimal fabrication condition.

Effect of Saponification Condition on the Morphology and Diameter of the Electrospun Poly(vinyl acetate) Nanofibers for the Fabrication of Poly(vinyl alcohol) Nanofiber Mats.

Novel poly(vinyl alcohol) (PVA) nanofiber mats were prepared for the first time through heterogeneous saponification of electrospun poly(vinyl acetate) (PVAc) nanofibers. The effect of varying the saponification conditions, including temperature, time, and concentration of the alkaline solution, on the morphology of the saponified PVA fibers were evaluated by field-emission scanning electron microscopy. At 25 °C, the saponified PVA fibers exhibited a broad diameter distribution. The average fiber diameter, however, was found to decrease with increasing saponification temperature. When the saponification time was increased from 6 to 30 h, the average fiber diameter decreased gradually from 1540 to 1060 nm. In addition, the fiber diameter and morphology were also affected by the concentration of the alkaline saponification solution. The most optimal conditions for fabrication of thin, uniform, and smooth PVA nanofibers corresponded to an alkaline solution containing 10 g each of NaOH, Na2SO4, and methanol per 100 g of water, a temperature of 25 °C, and a saponification time of 24 h.

Optimization of growth parameters for absorber material SnS thin films grown by SILAR method using response surface methodology

In this paper, SnS films were deposited on glass substrates by successive ionic layer adsorption and reaction method under different deposition conditions. Quality of semiconductor thin films depends on their deposition parameters. The deposition process was optimized by the application of five-level-three-factor central composite design. Response surface methodology was used to optimize deposition parameters including temperature of precursor solutions (27–43 °C), dipping time (3–37 s) and dipping cycles (23–57 cycles) for deposition of the SnS thin films. The effect of the deposition parameters on the film growth has been studied using the experimental design methodology. The optimum fabrication conditions were found to be 40 °C (temperature), 23.4 s (dipping time) and 50 cycles (dipping cycles), respectively. Under optimum terms, the Eg value of SnS nanostructures calculated as 1.73 eV. The optimized value showed a good fit to the predicted value (1.67 eV). In addition, the structural, optical and morphological properties of thin films were investigated.

Synthesis of the light/pH responsive polymer for immobilization of α-amylase

In this study, light/pH responsive methoxy poly (ethylene glycol)-(5-propargylether-2-nitrobenzyl bromoisobutyrate)-poly methylacrylic acid-b-polystyrene (mPEG-ONB-PMAA-b-PS) polymers were synthesized, and successfully utilized to fabricate micelles and immobilize α-amylase. The critical micelle concentrations (CMC) of the polymers were measured with Pyrene Fluorescent Probe Technique. The morphology and diameter of micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In addition, the effects of pH, temperature and light-responsive on the catalytic activity were investigated. The optimized fabrication conditions of α-amylase-loaded micelles which α-amylase gave the higher activity were as follows: Immobilization time, 60min; Immobilization temperature, 50°C; enzyme concentration, 10UmL−1; PBS buffer, pH=5.4. α-Amylase immobilized in these micelles was much more stable than that free α-amylase.

Mechanically enhanced PES electrospun nanofiber membranes (ENMs) for microfiltration: The effects of ENM properties on membrane performance

The application of electrospun nanofiber membranes (ENMs) as microfilters for the process of water purification requires the substrate to possess suitable strength, permeability, and a smooth surface. Therefore, the fiber homogeneity, inter-fiber adhesion, and surface roughness of the ENMs must be carefully controlled. Concurrently, an understanding of the ENMs' rejection mechanism for contaminants is necessary for the effective application of ENMs. In this study, we demonstrate the fabrication of polyethersulfone (PES) ENMs, which are useful for water purification as water treatment membranes. An optimum fabrication condition that can significantly improve the mechanical property and surface roughness of the PES membrane is also illustrated. This technique induces the solvent remaining on the fiber's surface after the electrospinning process, and the mechanical properties and surface roughness of the membrane are improved by the solvent-induced fusion of the fiber. The fabricated PES ENMs also show higher clean water productivity. Additionally, we show that a particulate contaminant in water is mainly rejected on the ENM surface by using a water filtration test. Based on our conclusions, we suggest the appropriate ENM regeneration method and confirm that the fabricated ENMs show excellent regeneration ability.

Tailoring cathode structure of catalyst coated membranes for performance enhancement in direct methanol fuel cells

In this study, we demonstrate how the formulation of colloidal catalyst ink and fabrication conditions affect the cathode microstructure of catalyst coated membranes (CCMs) prepared via decal technique. The CCMs based on conventional and high concentration cathode inks are compared in a direct methanol fuel cell (DMFC). It is found that the cathode catalyst layer made with a high concentration ink possesses superior porosity, leading to an improved DMFC performance. The temperature of roll-press used for preparing CCM is varied ranging from 170 to 210 °C in order to determine the optimal fabrication conditions for high concentration ink-based cathode. The CCM hot-pressed at 200 °C (advanced CCM) retains a significantly higher pore volume and outperforms the conventional CCM by delivering an excellent DMFC performance with a maximum power density of 155 mW cm−2, which is 20% higher than that of the conventional CCM.

Effect of heat pre-treatment conditions on the electrochemical properties of mangrove wood-derived hard carbon as an effective anode material for lithium-ion batteries

Anodic hard carbon for lithium-ion batteries with high discharge capacity was successfully developed using mangrove green tree as a cheap raw material. To obtain commercial-level first-cycle Coulombic efficiency, the effects of heat pre-treatment in the low temperature range of 450–600°C at various pressures, to produce optimized char precursor before carbonization, were closely investigated, focusing on synthetic yield, structural and physical properties, first-cycle Coulombic efficiency, and discharge capacity of the resulting hard carbon. The hard carbon with heat pre-treatment involving optimum fabrication conditions of 500°C in inner gas at 0.7MPa for 39days exhibited higher synthetic yield of 30.0wt% and better first-cycle Coulombic efficiency of 81% and discharge capacity of 424mAh/g than that prepared through direct one-step carbonization, due to low H/C and Odiff/C ratios and a pore structure promoting lithium-ion insertion/desertion.