4.2 V Stack of metal oxide-polypyrrole-based composite electrodes and their power management

Polypyrrole (PPy)-based composites containing nanostructured VO _x, PbO _x, and MnO _x are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm²) formed as a result of the intercalation with their metals. Both intercalation and synthesis are performed in the synthesis solution containing metal(II)tetrafluoroborate salts, pyrrole monomer, HBF₄, H₂O, Triton-X 100 (TX100), and carboxymethyl cellulose (CMC). The mass loading of the composite at the electrode is maintained at 10 mg cm⁻². Symmetric and asymmetric unit cells are prepared in polyvinyl alcohol (PVA)/H₂SO₄ (1:1) gel electrolyte using composites synthesized on the treated graphite paper electrode. The electrical properties of these cells are examined by electrochemical impedance spectroscopy and their capacitive properties by cyclic voltammetry and galvanostatic-charge discharge test. The asymmetrical cell, prepared with PPy/PbO _x/CMC composite having energy density and cycle life better than others, exhibits 7.77 Wh kg⁻¹ and 0.51 kW kg⁻¹ at a working voltage of 1.4 V, considering the total mass of all sub-components. The three-cell asymmetric stack design, which is prepared using these composite-coated electrodes, achieves a coulombic efficiency of 76% at 4.2 V. Finally, an electronic control system (DC/DC buck-boost converter) is designed and implemented to manage the charge and discharge cycles of single-cell and bipolarly connected stack to operate the asymmetric supercapacitor arrays with high performance.     

Prevalence of Nitrite and Nitrate Contents and Its Effect on Edible Bird Nest's Color

Edible bird nests (EBNs) are important ethnomedicinal commodity in the Chinese community. Recently, But and others showed that the white EBNs could turn red by vapors from sodium nitrite (NaNO₂) in acidic condition or from bird soil, but this color‐changing agent remained elusive. The aim of this study was to determine the prevalence of nitrite and nitrate contents and its affects on EBN's color. EBNs were collected from swiftlet houses or caves in Southeast Asia. White EBNs were exposed to vapor from NaNO₂ in 2% HCl, or bird soil. The levels of nitrite (NO₂^?) and nitrate (NO₃^?) in EBNs were determined through ion chromatography analysis. Vapors from NaNO₂ in 2% HCl or bird soil stained white bird nests to brown/red colors, which correlated with increase nitrite and nitrate levels. Moreover, naturally formed cave‐EBNs (darker in color) also contained higher nitrite and nitrate levels compared to white house‐EBNs, suggesting a relationship between nitrite and nitrate with EBN's color. Of note, we detected no presence of hemoglobin in red “blood” nest. Using infrared spectra analysis, we demonstrated that red/brown cave‐EBNs contained higher intensities of C‐N and N‐O bonds compared to white house‐EBNs. Together, our study suggested that the color of EBNs was associated with the prevalence of the nitrite and nitrate contents.     

Warp and weft directional tensile properties of multistitched biaxial woven E-glass/polyester composites

The objective of this research work was to understand the warp and weft directional tensile properties of the two-dimensional multistitched multilayer E-glass/polyester woven composites. The warp and weft directional specific tensile strength and modulus of unstitched structure were higher than those of multistitched structures as stitching caused minor warp and weft yarn filament breakages. Contrarily, the specific tensile strains of unstitched structure were slightly lower than those of all multistitched structures. The stitching yarn type, the number of stitching directions, and the stitching density generally influenced the warp and weft directional tensile properties of multistitched E-glass/polyester woven composites. The failure of warp and weft directional multistitched woven E-glass/polyester composite structures was matrix breakages, and partial and complete yarn breakages in their surfaces. They had a local delamination in their cross-sections and the delamination did not propagate to the large areas due to multidirectional stitching. Also, the failure was confined at a narrow area and resulted in the catastrophic fiber breakages. The warp and weft directional specific damaged areas of multistitched structures, in particular four-directional stitching, were significantly lower than those of the unstitched structures. This indicated that the multistitching made the structures better damage-tolerance materials.     

Nanofiltration of glucose solution containing salts: Effects of membrane characteristics,organic component and salts on retention

The understanding on nanofiltration especially the rejection of uncharged solutes, charged solutes and mixture of solutes is crucial for its application in food industry. This is because process streams in food industry usually contain organic components without charge and salts. In this work, DK and CK membranes were utilized for the separation of multi-component feeds containing glucose, NaCl and multivalent salts (MgCl₂ or Na₂SO₄). Glucose rejection is slightly affected by salt concentration which may due to pore swelling of CK membranes at high concentration of NaCl. Meanwhile, rejection of NaCl is reduced by the increment of glucose and NaCl concentration which causes concentration polarization. The addition of multivalent salts even induces negative rejection of NaCl in DK membranes. However, both membranes show high rejection of multivalent salts with or without the presence of glucose. The rejection behavior follows the pattern expected from the structural and electrical properties of the membranes.     

Plasticized chitosan-PVA blend polymer electrolyte based proton battery

This paper focused on the transport studies of PVA-chitosan blended electrolyte system and application in proton batteries. The electrolytes were prepared by the solution cast technique. In this work, 36 wt.% PVA and 24 wt.% chitosan blend doped with 40 wt.% NH₄NO₃ exhibited the highest room temperature conductivity. The conductivity value obtained was 2.07 × 10⁻⁵ S cm⁻¹. EC was then added in various quantities to the 60 wt.% [60 wt.% PVA-40 wt.% chitosan]-40 wt.% NH₄NO₃ composition in order to enhance the conductivity of the sample. The highest conductivity obtained was 1.60 × 10⁻³ S cm⁻¹ for the sample containing 70 wt.% EC. The Rice and Roth model was applied to analyze the conductivity enhancement. The highest conducting sample in the plasticized system was used to fabricate several batteries with configuration Zn//MnO₂. The open circuit potential (OCP) of the fabricated batteries was between 1.6 and 1.7 V.     

An expert system approach for die and mold making operations

In the modern manufacturing of sophisticated parts with 3D sculptured surfaces, die and mold making operations are the most widely used machining processes to remove unwanted material. To manufacture a die or a mold, many different cutting tools are involved, from deep hole drills to the smallest ball nose end mills. Since the specification of each tool is very different from each other, each mold or die is specific with their complicated shapes and many machining rules exist to consider, a great deal of expertise is needed in planning the machining operations. An expert system (DieEX) developed for this purpose is described in the present work. The geometry and the material of the workpiece, tool material, tool condition and operation type are considered as input values and various recommendations about the tool type, tool specifications, work holding method, type of milling operation, direction of feed and offset values are provided.     

The substituent effects on the structure and surface morphology of polyaniline

In this work, poly(2‐fluoroaniline), poly(2‐chloroaniline), poly(2‐methylaniline), and poly(N‐ethylaniline) were prepared by a self‐assembly method using an oxidizing system consisting of a dopant anion, p‐toluene sulfonate with ammonium peroxydisulfate. The effects of substituents on the surface morphology, conductivity, molecular weight, spectral and thermal properties of the polymers were studied. SEM results revealed that the surface morphology of the resulting polymers changed from nanofiber to spherical structure by changing the substituent on the aniline monomers. The structure and properties of these conducting films were characterized by FTIR, UV‐vis, elemental analysis, TGA, conductivity, and cyclic voltammetry. The polymer films show electroactivity in monomer free solution. Molecular weight of the polymers was determined by gel permeation chromatography. The dry electrical conductivity values of the substituted‐polyanilines were found to be lower than that of PANI. The results revealed that the molecular structures of the polymers were similar to those of the emeraldine form of polyaniline. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Estimation of Minimum Working Capital for Construction Projects in Malaysia

Forecasting cash requirements is essential for all contractors during the tendering stage since cash flow at the beginning of the project is a major cause of construction companies’ failure. Unfortunately, estimating minimum working capital (MWC) is not the mainstream practice of the majority of contractors in Malaysia, who find that the present models for estimating MWC are cumbersome and seldom give an accurate estimate. Therefore estimates of MWC made during the tendering stage need to be simplified so they can be prepared quickly with minimum input. It is important for the developer or owner to select a qualified contractor with competent financial backing. This paper establishes the relationship among the factors that contribute to MWC requirements and presents a simple model that could be used as a guide to estimate MWC for housing construction projects in Malaysia. The estimation is based on percentages of variables of contract value based on the historical data that influence MWC; the MWC obtained is then expressed in terms of percentage of contract value.     

Processing of a multi‐layer polyetheretherketone composite for use in acetabular cup prosthesis

The hydroxyapatite polyetheretherketone (HAPEEK) as a non‐degradable bioactive polymer composite material with coating of hydroxyapatite (HA) as a bioactive ceramic material can enhance the osteointegration of carbon fiber reinforced polyetheretherketone (CFRPEEK) as a non‐degradable bioinert polymer composite. This study describes the joining process of CFRPEEK and HAPEEK beam components and coating process of HA on the HAPEEK substrate to achieve the multi‐layer PEEK composite for use in the application of acetabular cup prosthesis. The CFRPEEK and HAPEEK components were ultrasonically welded while the HA was plasma sprayed on the HAPEEK substrate. Ultrasonic welding parameters (length and direction of the energy directors at the interface, welding time, and pressure) were investigated by single cantilever beam and lap shear tests to achieve the optimum bonding strength of CFRPEEK and HAPEEK components. Plasma spraying parameters (e.g., surface speed, powder feed, current, primary gas flow, and system voltage) were altered to achieve the good adhesion of HA coating on the HAPEEK substrate, which was evaluated by scratch test. The results showed that the proposed multi‐layer composite was successfully processed by carrying out the ultrasonic welding and plasma spraying coating processes. The outcomes of this study could be used to develop a non‐metal acetabular cup prosthesis using the proposed multi‐layer composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40915.     

Influence of Al concentration on structural and optical properties of Al-doped ZnO thin films

Undoped ZnO and Al-doped zinc oxide (ZnO:Al) thin films with different Al concentrations were prepared onto Si (100) substrate by pulsed filtered cathodic vacuum arc deposition system at room temperature. The influence of doping on the structural and optical properties of thin films was investigated. The preferential (002) orientation was weakened by high aluminum doping in films. Raman measurement was performed for the doping effects in the ZnO. Atomic force microscopy images revealed that the surface of undoped ZnO film grown at RT was smoother than that of the Al-doped ZnO (ZnO:Al) films. The reflectance of all films was studied as a function of wavelength using UV–Vis–NIR spectrophotometer. Average total reflectance values of about 35 % in the wavelength range of 400–800 nm were obtained. Optical band gap of the films was determined using the reflectance spectra by means of Kubelka–Munk formula. From optical properties, the band gap energy was estimated for all films.