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Ceramic composites derived from polysilazane with the addition of silicon carbide
Alfian Noviyanto,Amirudin Wibowo,Galuh Sukmarani,Retno Kusumaningrum,Fiqhi Fauzi,Alvin Muhammad Habieb,Muhamad Ikhlasul Amal,Nurul Taufiqu Rochman 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3
Ceramic composites from the polysilazane with the addition of silicon carbide (SiC) was successfully sintered by a hot pressingfurnace at 1,600-1,800 ºC for 1 h under the applied pressure of 20 MPa in a nitrogen atmosphere. The addition of SiC did notinfluence the densification of sintered polysilazane. However, the phases generated during sintering were affected by theaddition of SiC, resulting in the multi-phases of sintered polysilazane/SiC composite. The formation of SiC, Si3N4, Si2N2O, andSiO2 phases were observed in the sintered polysilazane/SiC composite. The highest hardness of sintered polysilazane wasobtained with the addition of SiC sinter at 1,700 ºC, i.e., 24.3 ± 1.1 GPa, and decreased to 21.8 ± 0.7 GPa at 1,800 ºC. Thisis due to the sintered polysilazane/SiC composite at 1,700 ºC possess fine microstructure compared to 1,800 ºC. Meanwhile,the sintered polysilazane experienced significant grain growth at 1,700 ºC, thus the hardness of this sample was lower thansintered polysilazane/SiC composite.
Metal oxide additives for the sintering of silicon carbide: Reactivity and densification
Alfian Noviyanto,윤당혁 한국물리학회 2013 Current Applied Physics Vol.13 No.1
The effectiveness of sintering additives for b-SiC was examined based on thermodynamic calculations and experimental observations under hot pressing conditions of 1700e1800 C. Various types of oxides, such as Al2O3, Fe2O3, MgO, TiO2, WO3 and Y2O3, were examined theoretically by considering the Gibbs formation free energy and vapor pressure. According to experimental observations expanded to their binary and ternary systems after hot pressing at 1750 C and 20 MPa, Al2O3, MgO, Y2O3 and their mixed systems were found to be the only effective sintering additives that do not react with b-SiC at high temperatures. On the other hand, Fe2O3, TiO2, WO3 and their combinations with other oxides were not effective because of the reaction with b-SiC by forming the corresponding metal carbides and/or silicides, as predicted by thermodynamic simulations. Moreover, the experimental results for the additional possible components were also included.
Alfian Noviyanto 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.4
The effects of pyrolytic carbon interphase (PyC) thickness on the density, microstructure, and mechanical properties of continuous SiC fiber-reinforced SiC composites (SiCf/SiC) have been examined. Electrophoretic deposition combined with ultrasonication was performed to infiltrate a SiC-based matrix phase effectively into the fine voids of a Tyranno-SA SiC fabric preform, which was coated with PyC at thicknesses of 0, 200, 400, 600, and 800 nm. The density of the hot-pressed SiCf/SiC composites decreased with increasing PyC thickness because of the difficulty of matrix-phase infiltration into the fine voids of the preform. SiCf/SiC composites with PyC ≤ 400 nm showed a brittle fracture mode due to the strong fiber-matrix interface, in spite of their relatively high flexural strength. On the other hand, toughened SiCf/SiC composites could be achieved with PyC ≥ 600 nm because of the formation of a weak interface, in spite of their decreased flexural strength.
Alfian Noviyanto,윤당혁 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.1
This paper examines a range of metal oxides, including those containing relatively safe elements under neutron irradiation, such as Cr, Fe, Ta, Ti, V and W, as well as widely used oxides, Al2O3, MgO and Y2O3, as a sintering additive for β-SiC theoretically and experimentally. After selecting the most probable SiC oxidation reaction at 1973-2123 K, the condition where the metal oxide additive does not decompose SiC was calculated based on the standard Gibbs formation free energies. Thermodynamic calculations revealed that Al2O3, MgO and Y2O3 could be an effective sintering additive without decomposing SiC under hot pressing conditions, which was demonstrated experimentally. On the other hand, no one component metal oxide that contains a safe element for nuclear reactor applications was found to be an effective sintering additive due to the formation of metal carbides and/or silicides. Overall, the simulation based on thermodynamic calculations was found to be quite useful for selecting effective metal oxide additives.
Abdi, Alfian,Cha, Hyouk-Kyu Elsevier Ltd 2016 Microelectronics Journal Vol.58 No.-
<P>A bidirectional neural interface analog front-end IC with both stimulation and recording functions is implemented using 0.18-mu m standard CMOS process. The proposed IC is comprised of a bipolar biphasic neural stimulator using a transistor-stacked current- mirror driver to achieve good current matching performance in stimulation mode and low-voltage capacitive feedback neural amplifiers for recording mode. In order to save die area, high-voltage isolation switches are embedded within the stimulator core to protect the low-voltage recording circuits from damage. Despite using a low-voltage process, the stimulator is able to deliver up to 1 mA current through 10 k ohm load using 12.8 V supply voltage and the recording amplifier uses 0.8 V supply voltage while consuming 1 mu A of current. The complete IC occupies 0.29 mm(2) of die area and can be applied for various multi electrode array interface bidirectional neural SoCs in medical implant devices.</P>
Eduard Alfian Syamsya SIJABAT,Umar NIMRAN,Hamidah Nayati UTAMI,Arik PRASETYA 한국유통과학회 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.1
Established and new companies face similar business challenges in achieving performance and competitiveness. Furthermore, several empirical studies using competitive advantage resource-based view theory show that established companies achieve performance and competitiveness with breakthrough innovations. Similarly, new business ventures with limited resources must incorporate breakthrough innovations to achieve performance and competitiveness. Therefore, this study aimed to examine the impact of ambidextrous innovation on new venture performance and competitiveness. It used an online survey to collect data from 178 newly established shipping agency companies in 22 provinces in Indonesia. Data was analyzed using multivariate analysis with WarpPLS 7.0, where the analysis unit was an organization represented by a director. The results showed that ambidextrous innovation positively and significantly affects firm performance and new venture competitiveness. This means that ambidextrous innovation that emphasizes adaptation and development improves the firm’s internal business processes, even with limited resources. Moreover, it increases new ventures’ competitiveness in responding to threats and taking advantage of market opportunities. These results contribute to the competitive advantage resource-based view theory, specifically for new venture empirical examination. Also, they contribute to practical implications in the transportation business, demonstrating that exploitative breakthrough innovation can improve new venture competitiveness and performance.