Effect of hexagonal-BN on phase transformation of additive-free Si3N4/SiC nanocomposites prepared from amorphous precursor

NOVIYANTO, Alfian,YOON, Dang-Hyok,LEE, Kyungseok,KIM, Young Moon,KIM, Doo-In,JEONG, Young-Keun,KIM, Kwang Ho,KWON, Sehun,HAN, Young-Hwan Elsevier 2013 Transactions of Nonferrous Metals Society of China Vol.23 No.2

Rare-earth oxide additives for the sintering of silicon carbide

Noviyanto, A.,Yoon, D.H. Elsevier 2013 Diamond and related materials Vol.38 No.-

The feasibility of a single component rare-earth oxide (Sc<SUB>2</SUB>O<SUB>3</SUB>, CeO<SUB>2</SUB>, Nd<SUB>2</SUB>O<SUB>3</SUB>, Sm<SUB>2</SUB>O<SUB>3</SUB>, Gd<SUB>2</SUB>O<SUB>3</SUB>, Dy<SUB>2</SUB>O<SUB>3</SUB>, Ho<SUB>2</SUB>O<SUB>3</SUB>, Er<SUB>2</SUB>O<SUB>3</SUB>, La<SUB>2</SUB>O<SUB>3</SUB>, Tm<SUB>2</SUB>O<SUB>3</SUB>, Yb<SUB>2</SUB>O<SUB>3</SUB> and Lu<SUB>2</SUB>O<SUB>3</SUB>) as a sintering additive for β-SiC was examined. The Gibbs formation free energies were first considered to identify the rare-earth oxides that would not decompose SiC at the typical hot pressing temperatures (1973-2123K). The results from the thermodynamic calculations were then tested experimentally. All rare-earth oxides examined in this study increased the density of the samples without decomposing SiC, which is in contrast to that observed with most main-group oxides reported previously. Rare-earth oxide appeared to form a eutectic composition with SiO<SUB>2</SUB> existed on the SiC surface at temperatures lower than 1700<SUP>o</SUP>C and acted as a liquid-phase sintering additive. The decrease in particle size of the sintering additive resulted in an increase in SiC density, indicating the importance of a uniform additive distribution to achieve a dense SiC.

Metal oxide additives for the sintering of silicon carbide: Reactivity and densification

Noviyanto, Alfian,Yoon, Dang-Hyok Elsevier 2013 Current Applied Physics Vol.13 No.1

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.

One Component Metal Oxide Sintering Additive for β-SiC Based on Thermodynamic Calculation and Experimental Observations

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.

The effects of pyrolytic carbon interphase thickness on the properties of hot-pressed SiCf/SiC composites

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.

SiC_f/SiC 복합체의 특성에 미치는 열간가압소결 조건의 영향

노비얀토 알피안,윤당혁,Noviyanto, Alfian,Yoon, Dang-Hyok 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5

Continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by electrophoretic infiltration combined with ultrasonication. Nano-sized ${\beta}$-SiC added with 12 wt% of $Al_2O_3-Y_2O_3$ additive and Tyranno$^{TM}$-SA3 fabric were used as a matrix phase and fiber reinforcement, respectively. After hot pressing at 5 different conditions, the density, microstructure and mechanical properties of $SiC_f$/SiC were characterized. Hot pressing at relatively severe conditions, such as $1750^{\circ}C$ for 1 and 2 h, resulted in a brittle fracture behavior due to the strong fiber-matrix interface in spite of their high flexural strength. On the other hand, toughened $SiC_f$/SiC composite could be achieved by hot pressing at milder condition because of the formation of weak interface in spite of the decreased flexural strength. These results proposed the importance of weak fiber-matrix interface in the fabrication of ductile $SiC_f$/SiC composite.

액상소결 시의 β-SiC의 입자성장 방지

길건영,노비얀토 알피안,한영환,윤당혁,Gil, Gun-Young,Noviyanto, Alfian,Han, Young-Hwan,Yoon, Dang-Hyok 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.6

In our previous studies, continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by two different slurry infiltration methods: vacuum infiltration and electrophoretic deposition (EPD). 12 wt% of $Al_2O_3-Y_2O_3$-MgO with respect to SiC powder was used as additives for liquid-phase assisted sintering. After hot pressing at $1750^{\circ}C$ under 20 MPa for 2 h in Ar atmosphere, a high composite density could be achieved for both cases, whereas the problems such as large grain size and non-uniform distribution of liquid phase were observed, which was resulted in the relatively poor mechanical properties of composites. Therefore, efforts have been made to reduce the grain growth during the sintering, including the optimization for hot pressing condition and utilization of spark plasma sintering using a SiC monolith. Based on the results, spark plasma sintering was found to be effective method in decreasing the amount of sintering additive, time and grain growth, which will be explained in comparison to the results of hot pressing in this paper.

Characterization of Bioactive Sialyl Oligosaccharides Separated from Colostrum of Indonesia Dairy Goat

Epi Taufik,Irma Isnafia Arief,Cahyo Budiman,Yusuf Wibisono,Alfian Noviyanto 한국축산식품학회 2022 한국축산식품학회지 Vol.42 No.3

The bioactive functions of oligosaccharides from human milk have been reported by many studies. Many of oligosaccharides isolated from colostrum and/or milk of dairy animals have been reported to have similar chemical structures with those in human colostrum and/or milk. It has been proved by several studies that the oligosaccharides with similar chemical structure shared common bioactivities. Among domesticated dairy animals, bovine/cattle, caprine/goat, and ovine/sheep are the most commonly used species to isolate oligosaccharides from their colostrum and/or milk. Several studies on the oligosaccharides from goat colostrum and milk have revealed similar properties to that of human milk and possess the highest content of sialyl oligosaccharides (SOS) as compared to other ruminants. Indonesia ranks first in Association of Southeast Asian Nations (ASEAN) for goat milk production. Therefore, goat milk is the second most consumed milk in the country. The most reared dairy goat breed in Indonesia is Etawah Grade. However, oligosaccharides from Indonesia dairy animals including goat, have not been characterized. This is the first study to characterize oligosaccharides from Indonesia dairy animals. The present study was aimed to isolate and characterize oligosaccharides, specifically SOS from the colostrum of Etawah Grade goats by using proton/1H-nuclear magnetic resonance. The SOS successfully characterized in this study were: Neu5Ac(α2- 3)Gal(β1-4)Glc (3’-N-acetylneuraminyllactose), Neu5Ac(α2-6)Gal(β1-4)Glc (6’-Nacetylneuraminyllactose), Neu5Gc(α2-3)Gal(β1-4)Glc (3’-N-glycolylneuraminyllactose), Neu5Gc(α2-6)Gal(β1-4)Glc (6’-N-glycolylneuraminyllactose), Neu5Ac(α2-6)Gal(β1-4) GlcNAc (6’-N-acetylneuraminyllactosamine) and Neu5Gc(α2-6)Gal(β1-4)GlcNAc (6’- N-glycolylneuraminyllactosamine). This finding shows that Etawah Grade, as a local dairy goat breed in Indonesia, is having significant potential to be natural source of oligosaccharides that can be utilized in the future food and pharmaceutical industries.