Dynamic tensile and shear storage moduli of PEG/silica-polymorph composites

The effect of silica polymorphs on the thermomechanical properties of 0, 5, 10, and 20 wt % silica particles-reinforced-based poly(ethylene glycol) (PEG) composites have been studied as a function of temperature using dynamic mechanical analysis (DMA). The silica polymorphs exhibited quartz (Q), cristobalite (C), and amorphous (A) phases, which were obtained by processing natural silica sand. The DMA thermomechanical properties were determined in tensile (E) and shear (G) modes. The maximum storage moduli (E′ and G′) were achieved by samples with 20 wt % silica for all type of fillers. These values increased approximately 12 times for PEG/Q, 10 times for PEG/A, and 11 times for PEG/C composites compared to the pure PEG. Furthermore, the Poisson's ratio values of the composites were filler phase dependent, that is, 0.39–0.47 for PEG/Q, 0.15–0.18 for PEG/A, and somewhat anomalous for PEG/C composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47372.     

Synthesis of polymer/MWCNT nanocomposite catalyst supporting materials for high-temperature PEM fuel cells

In this study, the polymer/MWCNT nanocomposites were synthesized from the pristine MWCNT and polymer binders using functionalization with solution processing methods. The synthesized polymer/MWCNT nanocomposites exhibited high specific surface areas than the pristine MWCNT. The MWCNT/Nafion nanocomposite attributed to the maximum peak current at 5.795 × 10^?5 (A) while the peak current of MWCNT/PBI was obtained at 3.662 × 10^?5 (A). Moreover, polymer/MWCNT based electrocatalysts performed better electrochemical activity because of polymers binders can assist electrochemical interaction using the high surface areas of the catalyst supporting material. Also, the MEAs fabricated using the hot pressing method, while the acid doped PBI membrane sandwiched between the electrodes. The fabricated MEAs were successfully demonstrated in a single cell and found capable of measuring a maximum power density of 112.10 mW/cm² under 150 °C temperature. In conclusion, the synthesized catalyst-supporting materials enhanced the electrochemical activity and catalyst stability which fulfilling the main objective of this study.     

Electrochemically Exfoliated High‐Quality 2H‐MoS2 for Multiflake Thin Film Flexible Biosensors

2D molybdenum disulfide (MoS₂) gives a new inspiration for the field of nanoelectronics, photovoltaics, and sensorics. However, the most common processing technology, e.g., liquid‐phase based scalable exfoliation used for device fabrication, leads to the number of shortcomings that impede their large area production and integration. Major challenges are associated with the small size and low concentration of MoS₂ flakes, as well as insufficient control over their physical properties, e.g., internal heterogeneity of the metallic and semiconducting phases. Here it is demonstrated that large semiconducting MoS₂ sheets (with dimensions up to 50 µm) can be obtained by a facile cathodic exfoliation approach in nonaqueous electrolyte. The synthetic process avoids surface oxidation thus preserving the MoS₂ sheets with intact crystalline structure. It is further demonstrated at the proof‐of‐concept level, a solution‐processed large area (60 × 60 µm) flexible Ebola biosensor, based on a MoS₂ thin film (6 µm thickness) fabricated via restacking of the multiple flakes on the polyimide substrate. The experimental results reveal a low detection limit (in femtomolar–picomolar range) of the fabricated sensor devices. The presented exfoliation method opens up new opportunities for fabrication of large arrays of multifunctional biomedical devices based on novel 2D materials.     

Coating of stainless steel and titanium bipolar plates for anticorrosion in PEMFC: A review

Anticorrosion coating for stainless steel (SS) and titanium bipolar plates were evaluated to improve the corrosion resistance and electrical conductivity in PEMFC. The PEMFC offers clean and environmentally friendly usage in electrical power systems. The bipolar plates contribute 60%–80% of the total components of PEMFC stack with electrical conductivity >100 S cm^?1. Therefore, high conductivity and corrosion resistance are observed for long-term operations in PEMFC. Recent works has developed the cost-effective and feasible alternative materials to replace graphite bipolar plates. Metallic materials, such as SS and titanium, possess good electrical conductivity but poor corrosion resistance. Coating of SS and titanium bipolar plates can improve the corrosion resistance of metallic bipolar plates. Excellent performance of bipolar plates was recorded by using NbC coating for stainless steel materials. The ICR value using plasma surface alloying method was 8.47 mΩ cm² with a low current density (I_corr) between 0.051 and 0.058 μA cm^?2. The criteria for both current densities (<1 μA cm^?2) and electrical conductivity (<10 mΩ cm²) met the DOE's 2020 technical targets. In addition, conventional air brush method can be used for fabricating multilayer coatings onto substrates because it is self-cleaning, low cost and offers high volume and large area production. Vapor deposition method, a highly advanced coating technology using PVD, suitable for coating bipolar plates because it is environmentally friendly and can be used in high temperatures, producing materials with good impact strength and excellent abrasion resistance. PEMFC cost is still too high for large scale commercialization, which is the cost of raw material and processing to allow fabrication of thinner plates contributes substantially to the total PEMFC cost. Some future works on fuel cell anticorrosion research with reasonable coating method is suggested to reduce the cost in order to facilitate the move toward commercialization especially for SS and titanium bipolar plates.     

Three-month nutritional supplementation in Indonesian infants and toddlers benefits memory function 8 y later

Does short-term supplementary feeding during infancy and childhood have long-lasting effects? In 1986, 334 children aged 6-60 mo living on rural tea plantations in West Java, Indonesia, participated in a 3-mo randomized trial to test the effects of a dietary supplement providing approximately 1672 kJ (400 kcal) energy/d, with about the same nutrient density as local foods. We returned to the same communities in 1994 and enrolled 231 (125 supplemented, 106 control) of the original subjects in a follow-up study of the long-term effects of supplementation. We assessed these subjects by using several measures: anthropometry, iron status, information processing, Peabody Picture Vocabulary Test, word fluency, and an arithmetic test. The supplemented group showed no differences from those in the control group. However, when the analysis was limited to subjects who had received the supplement before the age of 18 mo (n = 73), the supplemented children performed better than control children on the Sternberg test of working memory (decision time intercept: probe absent, P = 0.002; probe present, P = 0.053). After considering possible confounders, we concluded that the supplementation during infancy was responsible for the difference. This finding shows that supplementation can have long-lasting effects on a specific domain if the child receives it at the appropriate stage of development.     

Optimum tip gap and orientation of multi-piezofan for heat transfer enhancement of finned heat sink in microelectronic cooling

Piezoelectric fans can be manipulated to generate airflow for cooling microelectronic devices. Their outstanding features include noise-free operation, low power consumption and suitability for confined spaces. This paper presents experimental optimization of tip gap and orientation angle of three piezoelectric fans (multi-piezofan) to maximize the heat removal performance of finned heat sink for microelectronic cooling. Design of experiments (DOE) approach is used for the optimization, and a three dimensional simulation using FLUENT 6.3.2 is carried out to better understand the flow induced by the multi-piezofan and the resulting heat transfer from the heat sink surface. For the optimization, the Central Composite Design (CCD) of response surface methodology (RSM) is exploited from the Design Expert software. In the numerical model, the flow induced by the piezofan is treated as incompressible and turbulent; the turbulence is taken care by the shear stress transport (SST) k–ω model. The experimental results are found to be in good agreement with the predictions. Out of 13 experimental trials determined by CCD, the optimum tip gap and fan orientation are found to be δ = 0.17 and 90° respectively. At this condition, an enhancement in convective heat transfer coefficient exceeding 88% is achieved, compared to natural convection.     

Highly Conductive,Stretchable, and Cell‐Adhesive Hydrogel by Nanoclay Doping

Electrically conductive materials that mimic physical and biological properties of tissues are urgently required for seamless brain–machine interfaces. Here, a multinetwork hydrogel combining electrical conductivity of 26 S m^?1, stretchability of 800%, and tissue‐like elastic modulus of 15 kPa with mimicry of the extracellular matrix is reported. Engineering this unique set of properties is enabled by a novel in‐scaffold polymerization approach. Colloidal hydrogels of the nanoclay Laponite are employed as supports for the assembly of secondary polymer networks. Laponite dramatically increases the conductivity of in‐scaffold polymerized poly(ethylene‐3,4‐diethoxy thiophene) in the absence of other dopants, while preserving excellent stretchability. The scaffold is coated with a layer containing adhesive peptide and polysaccharide dextran sulfate supporting the attachment, proliferation, and neuronal differentiation of human induced pluripotent stem cells directly on the surface of conductive hydrogels. Due to its compatibility with simple extrusion printing, this material promises to enable tissue‐mimetic neurostimulating electrodes.     

Simulation of Crude Palm Oil Dilution in a Palm Oil Mill Using Computational Fluid Dynamics

Computational fluid dynamics (CFD) simulation was applied to simulate the dilution of undiluted crude oil (UCO) in a dilution tank of a palm oil mill. Fluid flow and mixing characteristics were examined. Considering the mixing behavior, the mixing of dilution water and UCO occurred as soon as these fluids entered the dilution tank, and the oil mass fraction in the mixture decreased gradually towards the outlet of the tank. Meanwhile, the velocity of dilution water and UCO declined as the fluids moved from their respective inlets. The intensity of turbulence flow remained until near the tank outlet. For the parametric study, the oil mass fraction of diluted crude oil (DCO) increased with higher UCO flow rate and oil mass fraction in the UCO but declined with higher dilution water flow rate.     

Comparison of catalyst-coated membranes and catalyst-coated substrate for PEMFC membrane electrode assembly:A review

Catalyst-coated membranes (CCMs) have gained popularity among membrane electrode assembly (MEA) fabri-cators for their abilities and advantages compared with those of other methods, such as catalyst-coated sub-strates (CCSs). CCMs show a profound new analysis for reducing platinum (Pt) catalyst loading. In addition, they increase the total number of reactions that occur on the MEA because of their active area amplification, which leads to an improved catalyst-utilization efficiency rate. Moreover, several characteristics are involved in the MEA fabrication methods. Material-manufacturing effects with regard to catalyst inks and analysis of the overall performance of MEAs prepared by the CCM and CCS methods are deliberated. This deliberation empha-sizes the practical approaches in minimizing performance deterioration during the fabrication of MEAs using the CCM method and converses the commercialization of the CCM fabrication method toward developing an end product. Novel research is required for MEA fabrication using the CCM methods to ensure that the fuel cell performance is improved. Therefore, this review is focusing on the pros and cons of both distinguished methods, that is, CCM and CCS fabrication, for better comparison.