Key Engineering Materials Vol. 840

Abstract: To overcome the increased processing of eggshell waste in East Java, Indonesia, the important solution is to synthesize chicken eggshells into calcium carbonate. The process of synthesizing eggshells into calcium carbonate is carried out by a mechanochemical process using a ball milling machine for 10 h and the sintering time for 120 min at a temperature of 900, 1000, 1100, and 1200 °C. The results of the eggshell synthesis were characterized using X-ray Diffraction, SEM, Raman spectroscopy and FTIR. Those characterizations aimed to obtain the result of phase identification, morphology, physicochemical, and functional group of calcium carbonate. From the phase identification, calcium carbonate obtained from eggshell sintered 1000 °C shows the single-phase triangular structure with agglomeration and spherical morphology. The physicochemical results show that phonon interaction of calcium carbonate obtained from eggshell sintered at 1200 °C has the highest intensity at Raman shift 1083 cm^‒1 which indicates the C‒O symmetric stretching band. The functional group of calcium carbonate shows from FTIR results at 3642, 2987, 2508 cm^‒1 for O‒H bond, and 1790, 1507 cm^‒1 for C‒H bond, and 874, 712 cm^‒1 for calcite bonds respectively.

Abstract: The development of nanotechnology applications is rapidly growing in many sectors. One of them is silver nanoparticles (AgNPs) which are metal nanoparticles that play an important role, especially in nanomedicine. The most effective method of purifying to obtain stable AgNPs is very important to study. Experiments on the separation of AgNPs have been carried out using the size exclusion chromatography and centrifugation methods to see the effectiveness of refining the two methods. This experiment begins with the synthesis of AgNPs using the chemical reduction method. Then, the synthesized AgNPs were purified by Size Exclusion Chromatography (SEC) and centrifugation method then analyzed using UV-Vis spectrophotometer to determine the maximum peaks before and after purification. The experimental results were obtained that centrifugation methods and SEC having the same effectiveness in refining AgNPs. The centrifugation method at various speed (0, 3000, 6000, 9000, 12000 and 15000 rpm) gave wavelength results 403, 404, 404, 405, 404, and 404 nm. The SEC method using Sephadex-25 column showed the 4^th to 8^th fractions gave the maximum wavelength 404, 404, 404, 405, and 404 nm, respectively. The maximum wavelength of both methods showed the surface plasmon resonance characteristic of AgNPs. However, centrifugation at 3000 rpm has better homogeneity than SEC method.

Abstract: Reaction pathways for a water molecule dissociation (H₂O_ads) to form hydroxyl (OH_ads) and hydrogen (H_ads) on the Ru-alloyed Pt(111) surface were computationally modelled on the basis of density functional theory (DFT). The aim of this study was to evaluate whether or not such a reaction can take place and to determine the most probable route for this reaction. To get the answer, we calculated the potential energy surfaces (PES) of the proposed reaction pathways. From the results of the PES scan, we then obtained the most preferential pathway for H₂O dissociation, i.e., the reaction route with an activation energy of 0.72 eV. This activation energy value is lower than the value of pure Pt (111), the surface at which H₂O dissociation can occur in the real system. Thus, it can be said that water splitting may be easier when catalyzing Ru-alloyed surfaces compared to pure Pt catalysts.

Abstract: The addition of alcohol as an oxygenated compound in gasoline blends may increase the vapor pressure of gasoline mixture. As a result, the study of vapor-liquid equilibrium for gasoline component and alcohol is necessary. In this study, the vapor-liquid equilibrium of isobutanol – isooctane/n-heptane blends were obtained experimentally at temperatures in the range 303.15 to 323.15 K using modified simple quasi-static ebulliometer. The apparatus was validated by comparing the vapor pressure of pure isobutanol, isooctane, and n-heptane with the published data and giving average absolute deviation (AAD) between experimental and calculated ones with magnitude less than 1.0%. The addition of isobutanol with the mole fraction range from 0.2 to 0.6 would increase the vapor pressure of the isooctane and n-heptane up to 12% and 14% respectively. The vapor pressure of binary mixtures was correlated with the Wilson, Non-random two-liquid (NRTL), and Universal quasi-chemical (UNIQUAC) equations with AAD 1.6%, 1.5%, and 1.7%, respectively for isobutanol + isooctane system and 1.8%, 1.7%, and 2.0%, respectively for isobutanol + n-heptane system. The systems studied show positive deviation from Raoult’s Law.

Abstract: A Numerical calculation of the Fermi Surface (FS) evolution in cuprate using the one-band Hubbard model by the matrix diagonalization method has been done. This work focusses on the study of the evolution of the FS in the cuprate material, namely , numerically by introducing a specific order parameter in the Hubbard model matrix. In this study, we confirm two evolution types of the FS of as an experimental result. Firstly, the evolution of the antibonding FS topology from the electron-like to the hole-like is generated by the order parameter that has a form of where is the order parameter coefficient that corresponds to the hopping parameter of the atomic neighbor long-range interaction and is the normalized momenta coordinate of the first Brillouin zone. On the contrary, the order parameter that has a form of generates the evolution of the FS from the hole-like topology to the electron-like topology. Secondly, the anisotropic evolution of the FS can be described by an extended d-wave order parameter which generating either the V-shape or U-shape type of the energy gap.

Abstract: Rare Earth Element plus Yttrium (REY) is an critical element in green technology and consumer goods. Due to its limited supply, it is necessary to look for alternative sources of REY which one of the potential candidates is coal fly ash. Two samples of coal fly ash which originated from Indonesia were leached in an alkaline solution in order to remove Si and increase REY content. Samples were collected from pulverized coal power plant in East Java (sample T) and West Java (sample I). Leaching conditions were studied including concentration of NaOH, ratio of volume of liquid (L) to weight of solid (S) and leaching time. It was found that the optimum condition was reached at NaOH concentration of 8M, L/S ratio (10 mL: 1 g) and leaching time of 120 min. At this condition, percent removal of Si and REY enrichment were respectively 56.22% and 30% for sample I, and 33.75% and 24% for sample T.

Abstract: Acid treatment of mordenite was conducted using acetic acid to increase the Si/Al ratio. The acid treatment of mordenite by acetic acid was performed using sonication. The various time of treatments was used to investigate the effect of sonication in acid treatment of mordenite. Mordenite and all samples after treatment were characterized by ICP, FT-IR, XRD, and ammonia adsorption to measure their acidity. The Si/Al ratio of mordenite was increased from 11.33 to 17.31, 19.47, and 20.58 respectively for 3, 6, and 9 h of sonication. This result was supported by the T‒O bond vibration of samples which shift to higher wavenumber. The increase of the Si/Al ratio was followed by the decrease of acidity. The XRD test result revealed partial loss of mordenite framework after acid treatment. The results indicated that the sonication method can be used for acid treatment of mordenite.

Abstract: Synthesis strategy of hierarchical aluminosilicates was carried out by varying the starting material, type of a basic solution, and the hydrothermal condition. Aluminosilicate was synthesized using pre-treated low-quality kaolin by three kinds of basic solution, such as sodium hydroxide, sodium fluoride, and tetrapropyl ammonium hydroxide. The hydrothermal condition was carried out by gradual temperature and constant temperature. The desired mole ratio of Si/Al achieved by dealumination or by addition of silica. Products were characterized by X-ray diffraction, FTIR spectrometry, and nitrogen physisorption. Cation exchange was carried out on the product to obtain an acid catalyst. The acidity test of the catalyst was carried out by FTIR-pyridine spectrometry. The catalyst activity test was carried out to the acetalization reaction of 3,4-dimethoxybenzaldehyde with propylene glycol. The results showed that the catalyst synthesized with the basic solution of tetrapropyl ammonium hydroxide had the highest acid site number and the highest conversion of 3,4-dimethoxybenzaldehyde to acetal.

Abstract: Sound-absorbing acoustic materials are usually made of special materials which are sometimes expensive and prone to fire and do not have sufficient strength. This research offers materials that have sufficient properties for the above problems, namely by using porous concrete. This study aims to calculate the absorption values of porous concrete values. Porous concrete is concrete which does not use sand to forms a void in concrete that also might be used as a sound absorbent. The concrete then is substituted with silica fume to reach more compressive strength. The value of absorption was measured by the impedance method of two microphones. The sample was put in a tube with a diameter of 10 cm and a height of 5 cm. The proportion of samples using American NRMCA. Tests were carried out in the frequency range of 0-1600 Hz. The best sample is a sample with a 25% void ratio that could absorb sound over a long frequency range of 432-1600 Hz even though it only reaches class B. While the highest value of absorption coefficients was the sample with a void ratio of 20% which reach a value of 0.99997. The highest stiffness was achieved by 5% void concrete with a value of k= 5.8×10⁶.

Abstract: In an attempt to reduce the use of a formaldehyde-based adhesive that is dangerous for both human health and environment, several studies had been done to develop particleboard with natural bio-based adhesives. Between those bio-based adhesives that have been investigated, the combination of citric acid-starch was potential to be developed further as an adhesive to particleboard. In this research, the effect of starch addition and press temperature on the properties of bamboo particleboard were evaluated. This research uses a combination of citric acid/starch with the composition weight ratio of 100/0, 90/10, 80/20 and 70/30 and press temperature of 160, 180 and 200 °C. The manufacture of particleboard also used a three-step press cycle method which has not been done before in Petung bamboo particleboard production. The result showed that the three-press cycle method used in this research was able to produce a board with excellent properties than board produced by single-step press cycle method. This showed that the manufacture of the board in this research was more efficient to produce citric acid-starch bonded particleboard than previous method being used. The results also showed that both the addition of starch and the increase of press temperature especially improved bamboo particleboard mechanical properties. The board with the optimum properties resulted from particleboard with citric acid/starch adhesive with the composition weight ratio of 80/20 and press temperature of 180 °C which could meet JIS A 5908 (2003) type 18 requirement.