Key Engineering Materials Vol. 840

Abstract: Ammonium dihydrogen phosphate (ADP) is expected to be an effective catalyst to increase the water-resistance and hasten the curing speed of maltodextrin as wood adhesives. This research investigated the effect of ADP addition on the curing maltodextrin properties. The ratio of maltodextrin/ADP was 100/0 and 90/10 wt%. The heat treatment was 180-220 °C for 10 min. The water-resistance improvement and the chemical changes were analyzed using insoluble matter rate against boiling water and Fourier Transform Infrared (FTIR) analysis, respectively. The thermal behavior of the dried mixture of adhesives was also analyzed through differential scanning calorimetry (DSC) analysis at room temperature until 400 °C. The results showed that the water-resistance properties of maltodextrin increased with the addition of 10 wt% ADP and increasing the heating temperature. FTIR analysis detected a high water-resistant substance of furan in the adhesives with maltodextrin/ADP ratio 90/10 wt% and heat treatment of 220 °C for 10 min. DSC analysis showed that ADP addition can hasten the reaction of maltodextrin as the endotherm peak temperature was shifted from 272 to 204 °C.

Abstract: Membrane Electrode Assembly (MEA) is the most important component in fuel cell devices. Electrodes composing MEA greatly determine the performance and durability of its application in passive Direct Methanol Fuel Cell (DMFC). Fabrication and characterization of electrodes with various loading Pt-Ru/C catalysts and their application to DMFC have been carried out. The XRD characterization results indicate the presence of C atoms which are indicated by the appearance of peaks at angles 2θ = 25°-30°. In areas, 44.4° and 45.1° indicate the presence of Ru even with low intensity and platinum in the area of 54.67°, 39.86°, 54.736°, 39.88°, and 68.3°. The highest ECSA value and electrical conductivity and low resistance showed the best catalytic activity possessed by electrodes with the loading of Pt-Ru/C catalyst 10 mg/cm². MEA with a catalyst loading of 8 mg/cm² is known to have a fairly large initial voltage before the load is given based on the results of Open Circuit Voltage (OCV) measurements. The MEA performance was observed based on I-V and I-P performance tests using the SMART2 WonAtech Fuel Cell Test Station on passive DMFC stacks with 3 M methanol as fuel. The best MEA shown in MEA with catalyst loading is 10 mg/cm² because it can maintain and achieve a voltage and power density that is quite higher than other MEAs in each load increase in the form of current density.

Abstract: Ni-Zn Layered hydroxide salt (Ni-Zn LHS) has been synthesized from equimolar Ni(NO₃)₂ and Zn(NO₃)₂ by co-precipitation method using NaOH. The formation of layered assembly is confirmed in X-ray diffractogram, i.e. by the appearance of peaks at 2θ: 9.60°, 19.40°, 33.48°, and 59.76° which corresponds to diffraction plane (001), (003), (020), and (040), respectively. The synthesized Ni-Zn LHSs possessed the point of zero charge (pH_pzc) at pH 8 and nitrate as the interlamellar ion. The incorporation of salicylic acid into LHS can extend the property of LHS as a reductive adsorbent in the application of metal recovery. The immobilization of salicylic acid on the Ni-Zn-LHS was successfully done and indicated the strong pH-dependent property. The immobilization of salicylic acid on Ni-Zn LHSs was optimum at pH 7 and followed better the Langmuir than Freundlich isotherm models with immobilization capacity 64.93 mg/g. After the immobilization of salicylic acid, the basal spacing of Ni-Zn LHSs did not enlarge indicating that the immobilized salicylic acid was on the outer layer without entering the interlayer and this immobilized salicylic acid was stable at medium pH range 3 to 9.

Abstract: Similarity of chemical and physical properties between rare-earth elements (REEs) and Dy is the main concern in order to get Dy with high purity, which it is necessary to do separation by extraction process. The purpose of this research is to obtain the optimum condition of operation (stirring time and rate, concentration of nitric acid, feed, and solvent) and determine the distribution constant, separation factor, and extraction efficiency of Dy using Aliquat 336. This research was conducted by varying stirring time (10, 15, 20, 30, 40 minutes), stirring rate (100, 150, 200, 250, 300 rpm), nitric acid concentration (2, 3, 4, 5, 6 N), feed concentration (25,000; 50,000; 100,000; 150,000; 200,000 ppm) and solvent concentration (10, 20, 30, 40, 50 % v/v). The optimum result is achieved when operation is carried out at stirring 100 rpm about 15 minutes in nitric acid 3 N with 100,000 ppm of feed concentration using 30% solvent concentration (v/v) which extract more Dy element than Yttrium (Y) and Godolinium (Gd). The highest distribution constant of Dy is 0.427, separation factor of Dy-Y is 6.831, separation factor of Dy-Gd is 1.799, and extraction efficiency of Dy is 31.604%.