Advanced Materials Research Vol. 858

Abstract: Activated carbon fiber is known to posses better properties compared to granular and powdered variants, with significantly higher surface area and higher pore volume. Source of raw material and activation step are two crucial parameters for the pore development of activated carbon. Palm oil empty fruit bunch fiber contains naturally formed long open channels which offer better access of adsorbates into micropores. Chemical activation step typically involves inorganic acids such as phosphoric acid and sulfuric acid. However, such residues of inorganic acids might create unfavourable conditions for certain adsorption applications, if not removed properly from synthesized activated carbon fiber. Additionally, subsequent to the acid cleaning or removal step, most inorganic acids would eventually cause problems to the environment if acid disposal is not properly managed. This paper investigates on the effect of utilization of organic acids acetic acid and citric acid, as compared to commonly used inorganic acids, on the pore characteristics of palm oil empty fruit bunch fiber derived activated carbon fiber.

Abstract: The use of banana stem waste (BW) was evaluated as a pore-forming agent to manufacture a porous clay ceramic body. Raw clay was characterized by XRD, XRF and TGA. After the clay was mixed with banana stem waste, in various proportions, the mixtures were pressed before being fired at different temperatures i.e 1100°C, 1125 and 1150°C, for 3 h with a heating rate of 5°C/min. Pore formation and microstructure in the fired samples were characterized using FE-SEM, whilst bulk densities, porosities and water absorption were determined using the Archimedes method. The mechanical strength was also investigated in order to optimize the fabrication process itself. The results obtained showed shrinkages between 13.08-16.10%, density values ranging between 1.37-1.51g/cm³, whilst porosity was determined to be between 18.5 to 18.78 % and water absorption 9.77-10.06 %, respectively. The tensile strength was in the range of 9.03 to 9.80MPa. These results proved that banana stem waste (BW) is potentially capable to produce porous ceramic materials.

Abstract: Cordierite (2MgO.2Al₂O₃.5SiO₂) is an advanced ceramic which is popular for its high melting temperature and high resistance to thermal, chemical and corrosion and also low dielectric constant. The use of various structure of cordierite especially porous structure became more popular where its properties can be tailored by controlling the open and closed porosity, cell size distribution and cell morphology. In this study, porous cordierite was synthesized using sol gel method with addition of corn starch (5wt%, 10 wt%, 15 wt% and 20 wt %) as pore forming agent. Characterizations have done using scanning electron microscope (SEM) show that the corn starch used is polyhedral shape with pore size between 6-7 μm. Whereas SEM analysis on sintered sample shows that the porosity obtained ranging from 13 to 46 % with interconnected pores.

Abstract: In this work, soft combustion technique was used to study the effect of lanthanum (La) doping on the properties of Bi_0.5Na_0.5TiO₃ (BNT). The amount of La dopant investigated for (Bi_0.5Na_0.5)_(1-1.5x)La_xTiO₃ (BNLT) pellets were x = 0, 0.01, 0.02, 0.05 and 0.10 (0, 1, 2, 5 and 10 mol% La). The addition of La dopant into the BNT structure caused lattice distortion and altered the crystal symmetry of the BNT from hexagonal to tetragonal symmetry for BNLT. BNT and BNLT pellets were sintered at 1100°C for 3 hours and pure perovskite phase BNT was obtained with the addition of La up to 5 mol%. A secondary phase of Bi₂(Ti₂O₇) appeared when the pellet was doped with 10 mol% of La dopant. Increasing of La dopant in the pellet resulted in the increasing of dielectric constant and decreasing of dielectric loss. An optimum property was obtained by 5 mol% BNLT with dielectric constant of 753 and dielectric loss of 0.0377. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Abstract: The second-order responses depend on the structural symmetry of the metal nanostructures, which can give rise to interesting polarization dependences in the responses. We also show that the sensitivity of second-order processes to the symmetry provides important information about plasmonic effects in the nonlinear properties of the structures.

Abstract: Fe-doped zinc oxide nanorods (ZnO NRs) were synthesized by ex-situ doping using spray pyrolysis technique. In this work, the undoped ZnO NRs were pre-synthesized via chemical vapor deposition using Zn powder and oxygen gas at 650 °C. The average length and diameter of the ZnO NRs are 4.1 ± 1.1 μm and 553.1 ± 89.6 nm, respectively. The average aspect ratio and areal density of ZnO NRs is 8.2 ± 2.9 and 6.2 ± 1.1 NRs/um², respectively. Subsequently, these undoped ZnO NRs were kept in the horizontal tube furnace, whereas the dopant solution (FeCl₃) of 0.05 M concentration was kept in the aerosol generator, which was located outside of the furnace. The Fe aerosol was flowed into the reactor when substrate temperature reached 650 °C to achieve ex-situ doping. At this temperature, some of the Fe atoms were driven into the NRs, forming Fe-doped ZnO NRs particularly at their outer layer. The presence of Fe 2p_1/2 and Fe 2p_3/2 peaks at 722.3 eV and 705.7 eV in XPS analysis indicates that Fe atoms were in the local structure of FeO. The Fe-doped ZnO NRs have poor crystal quality attributed to the low I_UV/I_Vis ratio in room temperature PL analysis.

Abstract: A major effort has been made over last 20 or so years to introduce TiAl-based alloys into the market-place as engineering component. Recently, titanium aluminide based composites are competitive candidate for aerospace use due to the favorable properties of matrix material, such as low density, high specific strength and relative good properties at elevate temperature [1-4]. The amount of aluminum in titanium alloys exceeds that used in conventional alloys and can range from 10 to 48at%. This concentration of aluminum allows the formation of an in-situ alumina reinforcement which is responsible for the excellent oxidation, sulfidation and carburization resistance at temperatures of 1000°C and higher. However, their brittleness and rapid crack growth rate at low to intermediate temperature hinders their application/3/. Nevertheless, nanostructure of monolithic TiAl is unstable at elevate temperatures which deteriorate the high temperature properties. In order to improve the high temperature strength of intermetallic, ceramic particles can be utilized as reinforcements [4, 5]. Recently, in-situ techniques have been utilized to fabricate TiAl-Al₂O₃ composite through displacement reaction between TiO₂ and Al in planetary ball milling and subsequence heat treatment. The knowledge of reaction characteristic in the Al-TiO₂ system is great importance to optimize the processing/4, 6/. The chemical compatibility with the iron aluminide matrix at temperature above 1000°C is an important factor for the selection of reinforcements because extreme interfacial reaction during processing results in the degradation of mechanical properties [3, 4].

Abstract: This paper discussed the preparation of porous silica using styrene natural rubber (SNR) sacrificial template. The preparation of porous silica based on SNR template involved three steps which were the synthesis of SNR, the formation of SNR/silica, and the formation of porous silica. The SNR sacrificial template was synthesized using styrene as monomer and deproteinized natural rubber (DPNR) latex as based material. The effects of different silica loading and mixing methods were studied to produce SNR/silica films. Calcinations process was carried out to remove SNR to produce porous silica structure. The increasing of silica loadings enhanced the porosity of the template structure. The shaker mixing method produced better porous structure compared to the mechanical stirring and the magnetic stirring methods. The porous structure was analyzed via SEM which the optimum silica loading was obtained at 15 % of silica loading.

Abstract: n-Type NC-FeSi₂/p-type Si heterojunctions were successfully fabricated by PLD, and their forward current-voltage characteristics were analyzed on the basis of thermionic emission theory (TE) in the temperature range from 300 down to 77 K. With a decrease in the temperature, the ideality factor was increased while the zero-bias barrier height was decreased. The calculated values of ideality factor and barrier height were 3.07 and 0.63 eV at 300 K and 10.75 and 0.23 eV at 77 K. The large value of ideality factor indicated that a tunneling process contributes to the carrier transport mechanisms in the NC-FeSi₂ films. The series resistance, which was estimated by Cheungs method, was strongly dependent on temperature. At 300 K, the value of series resistance was 12.44 Ω and it was dramatically enhanced to be 1.71× 10⁵ Ω at 77 K.

Abstract: Microbiological Influenced Corrosion (MIC) is a common cause of metallic failure and currently known as one of the important case in pipeline failure. Otherwise it was often found also in cooling water system, in the equipment of pulp and paper, and oil and gas industry. Certain bacteria have a wide range of life condition and can be found anywhere. Sulfate Reducing Bacteria (SRB) is a bacteria that was frequently found as a cause of corrosion in steel surface by creating pits. In this research, the corrosion test was done by using one species of SRB which is Desulfovibrio Baculatus. The water that contains bacteria growth medium (API Sulfate Broth) is used as a media for API 5L X65 steel corrosion test. Sulfate for the growing of SRB was added in the solution in 8.56 , 17.12 , 42.8 and 85.64 ppm concentration, and the immersion test was done during 1,7,14,21 days. The source of sulfate is FeSO₄.7H₂O, and this compound was considered also as a source of Iron (II). The result shows that the weight loss is increase with increasing of immersion period. Between 7-14 days of immersion time, the increase of weight loss that present a corrosion rate attains the highest condition and decrease again after a longer time of immersion period. Morphologic observation reveals that the corrosion product consists of Iron Oxide and biological deposits that were formed at the beginning of corrosion test, and continuing with the formation of Iron Sulfide at a longer period of immersion. The formation of Iron Sulfide was associated with the increase of corrosion rate. Keywords: MIC, SRB, Desulfovibrio Baculatus, Immersion, FeSO₄ content.