Key Engineering Materials Vol. 862

Abstract: In this research, visible-light responsive g-C₃N₄, photocatalyst was achieved through the simple calcination of urea at 600 °C by using the muffle furnace. The effects of calcination soaking time on preparation of high performance g-C₃N₄ were studied at 1, 2, 3, and 4 h. The g-C₃N₄ prepared at various soaking times were characterized by the X-ray diffraction (XRD) for crystallographic information and the Fourier-transform infrared spectroscopy (FTIR) for chemical composition analysis. Further, in the case of morphology and surface area of prepared photocatalysts, the Transmission Electron Microscope (TEM) and Brunauer, Emmett and Teller (BET) were applied. The results demonstrated that g-C₃N₄ with tri-s-triazine based units could be synthesized by calcination of urea at 600 °C and soaking for 1-4 h, as evidently confirmed by XRD and FTIR. For photocatalytic performance in rhodamine B dye degradation under visible light irradiation of achieved g-C₃N₄ tended to increase as soaking time increased. Moreover, the dye adsorption ability of prepared photocatalysts was obviously developed upon increase of soaking times. Herein, the highest photocatalytic performance was obtained from sample which was soaked at 4 h.

Abstract: Water activity in foods can result in detrimental microbial activity during storage. The usual methods of water activity measurement involve destruction of the sample. Near infrared (NIR) hyperspectral imaging has previously been successfully used as a non-destructive method to determine various physical and chemical characteristics of a variety of foods. Therefore, this method was tested to determine whether it could be used to measure water activity of mamón cakes, a popular sponge cake developed in the Philippines. Individual samples (n = 178) were divided into a calibration set (n=119) and a prediction set (n=59). These samples were tested using NIR hyperspectral imaging (935-1720 nm) with a smoothing spectral pretreatment selected for developing the calibration model. Partial least squares regression was used to establish the model in order to predict the water activity. The results showed the accuracy of the calibration model in prediction that gave a correlation coefficient of 0.767 and the root mean square error of prediction of 0.0130. It was therefore concluded that NIR hyperspectral imaging has a potential for use and application for measuring the water activity of mamón cakes.

Abstract: Composite steel-concrete sections have a broad benefit through increasing structural strength as well as minimizing the self-loads. All past researches were concerned with pre-installed shear connectors (PRSC) in the manufacturing of composite sections. A new fabrication technique for steel-concrete-steel composite sections were presented in the current study by the post-installation shear connectors (POSC) passed-through an embedded polymerizing vinyl chloride (PVC) pipes. The performance of normal strength concrete prisms with a specified strength of 32 MPa connected to square steel tubes (SST) was investigated. Six specimens were fabricated in both methodologies, PRSC and POSC were experimentally tested by Push-out test. The spacing of the shear connectors was changed for every two specimens fabricated in two different ways in order to obtain a full behavioral view. However, POSC does not have full-bond to concrete prisms, the test revealed a comparable strength of POSC specimens. The test shows a slight increase in the ultimate strength of PRSC specimens by (12.11, 11.19, and 9.45) % than POSC specimens for 100mm, 150mm, and 200mm spaced shear connectors.

Abstract: This study aimed to investigate the effect of pH value raging from pH 4 - 8 on color development of silver colloids. Silver colloids with different colors were synthesized by chemical reduction method using NaBH₄ as a reducing agent and then adjusted pH value by adding dropwise of acetic acid. These silver colloids were characterized by Transmission Electron Microscopy and UV-Vis spectrophotometer. The results showed that the colors of silver colloids ranging from blue to yellow depended on amount of NaBH₄ added. Due to Localized Surface Plasmon Resonance (LSPR) properties, different shapes and sizes of silver nanoparticles resulting in different colors. It was found that the pH value also affected color development of silver colloids. By adjusting the pH value, the colors of silver colloids changed to different colors or shades, which were clarified by the changes in the center as well as intensity of the absorption spectra. Moreover, the silver colloid in an acidic condition led to aggregation of nanoparticles.

Abstract: Ultracapacitor is a new electrical energy storage device which has high power density than conventional battery and capacitor. It offers high capacitance in small volume compared to conventional capacitors. While selecting ultracapacitors for various applications, parameters like specific resistance, internal capacitance, pulse current, energy density are required to be considered. Amongst these factors, specific capacitance of ultracapacitor depends mainly on parameters of electrode. The present paper is focused on modeling of ultracapacitor based on variations in some of the electrode parameters. The objective of present research work is to apply a statistical method to obtain an electrode material based model for prismatic type ultracapacitor. To have deep insight about the performance through modeling approach, the number of trials have been taken by doing the variations in the electrode materials of ultracapacitor and the quantity of the electrode material loaded on the current collector. The effect of both these variations is studied over the specific capacitance, which is taken as output parameter of model. Developed model is validated at selected values of input parameters.

Abstract: Nitrogen-containing heterocyclic dicationic compounds with antioxidant properties have been synthesized and characterized by NMR spectroscopy. Their corrosion inhibiting behavior for zinc and steel protection have been studied by electrochemical polarization methods to assess the potential suitability of those compounds in hybrid galvanic zinc protective coatings. The individual assessment for corrosion inhibiting activity will facilitate the shortlisting of eligible candidates, help to avoid potential incompatibilities of ingredients, and reduce times in the process of designing hybrid coatings for corrosion protection. This study has found that the compounds have significant corrosion protecting effect on steel and zinc and those molecules were shortlisted for our future studies on galvanic hybrid coating of steel.

Abstract: Silica nanoparticles are a very promising functional material when purified from silica sand for wide application. In addition, a low cost and easy method to obtain the material will be increasing the value of silica sand. To synthesize of nanoparticles using an easily scalable, cheap and simple method, we suggest a sodium silicate solution as a precursor that silica sand was diluted on the NaOH. After that, the sodium silicate solution under various alcohols (methanol and ethanol) in the acid medium was conducted by sol gel method to obtain silica nanoparticles. The synthesized of silica nanoparticles was observed to the non-agglomerate, homogeneous and spherical shape with an average size about 200 nm. We also noted the existence of NaNO₃ by side product of reaction on the system, which may be the amorphous silica unidentified on the XRD results.

Abstract: Areca nut extract provides a variety of pharmacological effects that are beneficial for skincare applications. A nanoemulsion of areca nut extract was developed to mask the intense color and to improve the water solubility of the extract. This work studied the impact of a co-solvent on the characteristics and stability of the nanoemulsion. Our former optimized nanoemulsion was modified by adding a common co-solvent, propylene glycol or polyethylene glycol 400 (PEG400), to the formula. Phase separation, particle characteristics, antioxidant activity, in vitro cytotoxicity, and stability of the modified nanoemulsion were evaluated. This work has shown the successful encapsulation of areca nut extract with a great improvement of stability, well-maintained antioxidant activity and low toxicity on normal human skin fibroblast.

Abstract: Tapioca starch adulterated with dolomite is sold in markets, but this adulteration cannot be identified by normal visual inspection. Near infrared (NIR) hyperspectral imaging has been successfully used as a non-destructive method of identifying various characteristics of food, therefore it was tested to identify dolomite adulteration. Adulterated tapioca starch samples were prepared by adding dolomite in the range of 0.5-100% (wt/wt). Samples (N=400) of pure tapioca starch (0) and adulterated tapioca starch (1) were divided into calibration set (N=300) and a prediction set (N=100). All samples were scanned using NIR hyperspectral imaging (935-1720 nm) and spectra were pre-processed using Savitzky-Golay first derivative differentiation pretreatment in order to obtain the optimal conditions for establishing a classification model. Partial least squares-discriminant analysis was carried out to evaluate the accuracy of classification tapioca starch adulterated with dolomite. The results showed the total accuracy of prediction for classification was 100%. Therefore, NIR hyperspectral imaging was demonstrated to have a potential for use in detecting adulteration of tapioca starch with dolomite.