• Composites Research
• /
• v.30 no.2
• /
• pp.102-107
• /
• 2017

The preceramic polymer can realize a variety of complex ceramic structures that can not be obtained by conventional ceramic processes. Polycarbosilane, which is a typical preceramic polymer, can control the molecular structure, molecular weight and molecular weight distribution for preparing complex morphology and microstructure of SiC ceramics, including SiC fiber. In this paper, synthesis and molecular structure control technique of polycarbosilane is explained. The silicon carbide fiber prepared by melt spinning, stabilization and heat treatment, and ceramic fiber composites technology made by PIP process are also discussed. In addition, we introduce an example of the development of a complex silicon carbide material such as a silicon carbide hollow fiber having a nanoporous structure.

• Journal of the Korean Ceramic Society
• /
• v.49 no.4
• /
• pp.279-286
• /
• 2012

Microstructure tailoring of filler loaded preceramic polymer systems offers a high potential for property improvement of Si-based ceramics and composites. Advancements in manufacturing of bulk materials by controlling microstructure evolution during thermal induced polymer-ceramic transforma-tion and polymer-filler reactions will be presented. Rate controlled pyrolysis, multilayer gradient laminate design and surface modification by gas solid reaction are demonstrated to yield ceramic components of high fractional density and superior mechanical properties. Emerging fields of applications are presented.

• Applied Chemistry for Engineering
• /
• v.9 no.6
• /
• pp.791-797
• /
• 1998

As organosilicon based preceramic polymer, new zirconium hybridized polycarbosilane having a good thermal stability and forming stage was synthesized. Oxidative stability(infusibility) and mechanical property of this polymer during the thermal curing process and heat treatment were examined. Prepared zirconium hybridized polycarbisilane (PZC) was spun into fiber at $250{\sim}270^{\circ}C$. Spinnability of PZC polymer having a molecular weight of 1000 to 1400 and having a dispersity<2 was good. The thermal curing process of the PZC fiber was done at 140 to $200^{\circ}C$. The mechanical properties of PZC ceramic fiber depend on curing temperature of PZC as precursor of PZC ceramic fiber. It was found that the optimum curing temperature was variable with the molecular weight of PZC. The cured PZC fiber need constant gel fraction to have good tensile strength.

• Journal of the Korean institute of surface engineering
• /
• v.36 no.1
• /
• pp.85-88
• /
• 2003

By utilization of preceramic polymer of polymethylsiloxane (PMS), a $MoSi_2$SiOC/SiC ceramic composite was fabricated. The prepared composite displayed superior high temperature oxidation resistance by forming $SiO_2$ on the surface. The thin $SiO_2$ layer had some surface cracks, but they had not adversely deteriorated the oxidation resistance. The composite fabrication method employed in this study can be applied to protect any possible substrate material from aggressive oxidative attack, if the composite were coated on the substrate material.

• Journal of the Korean Ceramic Society
• /
• v.52 no.4
• /
• pp.243-247
• /
• 2015

Si(Al)ON precursor was synthesized by formation of new Si-N bond using organoaluminum imine and liquid type poly(phenyl carbosilane). It was decomposed between $200-600^{\circ}C$, and the ceramic yield was 51% after pyrolysis. 150 - 200 nm in thickness of coating film was obtained by spin coating method. The precursor was easily oxidized during process because it was unstable in air. However the oxygen content was limited to 0.5 - 0.7 to silicon in heat treatment step. Even though the content of nitrogen was decreased by pyrolysis, Al-N and Si-N bonds were formed in ammonia atmosphere, and Si(Al)ON film was formed with 0.2 in content to silicon.

• Journal of the Korean Ceramic Society
• /
• v.47 no.6
• /
• pp.572-577
• /
• 2010

Reaction-bonded $Si_3N_4$ has cost-reduction merit because inexpensive silicon powder was used as a start material. But its density was not so high enough to be used for structural materials. So the sintered reaction-bonded $Si_3N_4$techniques were developed to solve the low density problem. In this study the sintered reaction-bonded $Si_3N_4$ manufacturing method by using polymer precursor which recently attained significant interest owing to the good shaping and processing ability was proposed. The formations, properties of reaction-bonded $Si_3N_4$ from silicon and polysilazane mixture were investigated. High density reaction-bonded $Si_3N_4$ was manufactured from silicon and silicon-containing preceramic polymers and post-sintering technique. The mixtures of silicon powder and polysilazane were prepared and reaction sintered in $N_2$ atmosphere at $1350^{\circ}C$ and post-sintered at 1600~$1950^{\circ}C$. Density and phase were analyzed and correlated to the resulting material properties.

• Journal of the Korean Ceramic Society
• /
• v.43 no.8 s.291
• /
• pp.486-491
• /
• 2006

A new $TiN-Ti_5Si_3$ bulk composite was synthesized from preceramic, inorganic polymer (methylpolysilsesquioxane) and $TiH_2$ filler powders via polymer pyrolysis. Using this process, ceramics with high melting points can be produced relatively easily to a near net shape. The $TiN-Ti_5Si_3$ composite oxidized slowly during heating to $1000^{\circ}C$. During heating at the temperatures of at 700 and $800^{\circ}C$, TiN oxidized to Rutile-$TiO_2$ whereas $Ti_5Si_3$ resisted to oxidation. The oxide scale formed consisted primarily of $TiO_2$ containing $Ti_5Si_3$.

• Journal of the Korean Ceramic Society
• /
• v.46 no.5
• /
• pp.462-466
• /
• 2009

We investigated the pore properties of inorganic membranes applied for hydrogen separation industry. Inorganic membranes were derived from polysilazanes. The thermal reactions involved were studied using thermogravimetry(TG) and IR spectroscopy(FTIR) of the solids. To determine the thermal effect of pore properties, polysilazanes were pyrolysed in inert atmosphere. Pore volume and BET surface area showed the maximum value at a pyrolysis temperature of $500^{\circ}C$. For amorphous SiCN membrane derived from polysilazanes, selectivity of $H_2/N_2$ was 4.81 at $600^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.41 no.7
• /
• pp.555-559
• /
• 2004

Ceramic foams were prepared by a self-blowing process of a polysiloxane with A1$_2$O$_3$ as a filler. The release of water and ethanol vapor during the condensation reaction of the polymer triggered the pores in the polymer melt. The size. interconnectivity and shape of the pores in the ceramic foams were strongly dependent on the viscosity of the polymer melt, which could be varied by the content and size oi the filler. When the content of the filler inceased and the size of the filler decreased. the size of the pores were decreased and the thickness between the pores were increased. In the addition, the viscosity of polymer melt increased by the pretreatment at 130$^{\circ}C$ for Ire intermolecular cross linking thereby stabilizing the foam structure. The density and compressive strength of the ceramic foams were affected by the heating rate during the blowing process.

• Journal of the Korean Ceramic Society
• /
• v.41 no.7
• /
• pp.528-533
• /
• 2004

Macroporous SiC with pore size 84∼658 nm and mesoporous SiC with pore size 15∼65 nm were respectively prepared by infiltrating low viscosity preceramic polymer solutions into the various sacrificial templates obtained by natural sedimentation or centrifuge of 20∼700 nm silica sol, which were subsequently etched off with HF after pyrolysis at 1000∼140$0^{\circ}C$ in an argon atmosphere. Three-dimensionally long range ordered macroporous SiC ceramics derived from polymethylsilane (PMS) showed surface area 584.64$m^2$g$^{-1}$ when prepared with 112nm silica sol and at 140$0^{\circ}C$, whereas mesoporous SiC from polycarbosilane (PCS) exhibited the highest surface area 619.4 $m^2$g$^{-1}$ with random pore array when prepared with 20-30 nm silica sol and at 100$0^{\circ}C$. Finally, tile pore characteristics of porous SiC on the types of silica sol, polymers and pyrolytic conditions were interpreted with the analytical results of SEM, TEM, and BET instruments.