Mesoporous Silicon Carbide Research Articles

Preparation of Mesoporous Silicon Carbide

Mesoporous silicon carbide with and without SiC filler was prepared from the pyrolysis of polycarbosilane (PCS), and the relationship between pyrolysis and properties of micro/meso pores was investigated. The surface area of pyrolyzed PCS without filler significantly decreased from 268 to 0.5m2/g with increasing pyrolysis temperature, and disappearance of the micropores was observed. In contrast, the pyrolyzed PCS with filler showed the retention of micro/mesopores, regardless of pyrolysis temperature. In addition, high surface area ranging from 120 to 180m2/g and a bimodal pore distribution were observed in pyrolyzed PCS with filler. FT-IR showed the decomposition of Si-H, Si-CH3 and Si-CH2-Si in the PCS network during pyrolysis, which led to the evolution of hydrogen and methane gas. However, the obtained pores might be larger than the size of evolved gases. Thus, though micro/meso pores and large surface area were retained by the addition of filler, coalescence between pores could occur during pyrolysis.

Synthesis of a novel mesoporous silicon carbide with a thorn-ball-like shape

A novel kind of mesoporous silicon carbide (SiC) was synthesized via the carbothermal reduction reaction of carbonaceous silicon xerogel . The purified SiC sample was characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, electron microscopy and N 2 porosimetry . The results show that the SiC obtained has a thorn-ball-like (TBL) shape. The TBL SiC sample has a surface area of 141 m 2 /g and a pore diameter in the range of 2–30 nm, and possesses two different kinds of pores.

Thermal stability of high surface area silicon carbide materials

The synthesis of mesoporous silicon carbide by chemical vapor infiltration of dimethyl dichlorosilane into mesoporous silica SBA-15 and subsequent dissolution of the silica matrix with HF was investigated. The influence of the synthesis parameters of the composite material (SiC/SBA-15) on the final product (mesoporous SiC) was determined. Depending on the preparation conditions, materials with specific surface areas from 410 to 830 m 2 g −1 and pore sizes between 2 and 10 nm with high mesopore volume (0.31–0.96 cm 3 g −1) were prepared. Additionally, the thermal stability of mesoporous silicon carbide at 1573 K in an inert atmosphere (argon) was investigated, and compared to that of SBA-15 and ordered mesoporous carbon (CMK-1). Mesoporous SiC has a much higher thermal textural stability as compared to SBA-15, but a lower stability than ordered mesoporous carbon CMK-1.

Highly Ordered Mesoporous Silicon Carbide Ceramics with Large Surface Areas and High Stability

AbstractHighly ordered mesoporous silicon carbide ceramics have been successfully synthesized with yields higher than 75 % via a one‐step nanocasting process using commercial polycarbosilane (PCS) as a precursor and mesoporous silica as hard templates. Mesoporous SiC nanowires in two‐dimensional (2D) hexagonal arrays (p6m) can be easily replicated from a mesoporous silica SBA‐15 template. Small‐angle X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images show that the SiC nanowires have long‐range regularity over large areas because of the interwire pillar connections. A three‐dimensional (3D) bicontinuous cubic mesoporous SiC structure (Ia3d) can be fabricated using mesoporous silica KIT‐6 as the mother template. The structure shows higher thermal stability than the 2D hexagonal mesoporous SiC, mostly because of the 3D network connections. The major constituent of the products is SiC, with 12 % excess carbon and 14 % oxygen measured by elemental analysis. The obtained mesoporous SiC ceramics are amorphous below 1200 °C and are mainly composed of randomly oriented β‐SiC crystallites after treatment at 1400 °C. N2‐sorption isotherms reveal that these ordered mesoporous SiC ceramics have high Brunauer–Emmett–Teller (BET) specific surface areas (up to 720 m2 g–1), large pore volumes (∼ 0.8 cm3 g–1), and narrow pore‐size distributions (mean values of 2.0–3.7 nm), even upon calcination at temperatures as high as 1400 °C. The rough surface and high order of the nanowire arrays result from the strong interconnections of the SiC products and are the main reasons for such high surface areas. XRD, N2‐sorption, and TEM measurements show that the mesoporous SiC ceramics have ultrahigh stability even after re‐treatment at 1400 °C under a N2 atmosphere. Compared with 2D hexagonal SiC nanowire arrays, 3D cubic mesoporous SiC shows superior thermal stability, as well as higher surface areas (590 m2 g–1) and larger pore volumes (∼ 0.71 cm3 g–1).

ポリカルボシランとナノ粒子によるメソポーラス炭化ケイ素の作製

Mesoporous silicon carbide (SiC) ceramics were produced via the pyrolysis of polycarbosilane (PCS) with and without SiC nano sized particle filler, and their pore characteristics such as size and BET surface area were investigated. The amount of filler and the pyrolysis temperature significantly affected the surface area and pore size. The surface area of PCS reached around 0.5 m2/g by the pyrolysis at 800°C and pore also was found to almost disappear. In contrast, the specimen with filler showed high surface area above 200 m2/g after the pyrolysis at 800°C and the retention of mesopore even after the pyrolysis at 1200°C.

Morphology-Controlled Synthesis of Nanostructured Silicon Carbide

AbstractPhenolic resin and tetraethoxysilane were used to prepare a binary carbonaceous silicon xerogel, the precursor of silicon carbide (SiC). By employing different additives in the sol-gel process, a series of xerogel precursors with differently chemical composition were obtained. Heating these xerogels to 1250°C, nanostructured β-SiC with various morphologies including nanowires, nanofibers, nanoparticles and mesoporous SiC were produced via carbothermal reduction. The preparation method of the xerogels was presented and the influences of different additives on the sol-gel process and the SiC formation were discussed in this paper.

Synthesis and characterization of mesoporous silicon carbide

A modified sol–gel method is proposed for the preparation of mesoporous silicon carbide. In this method, tetraethoxysilane (TEOS) and phenolic resin are used for preparing a binary carbonaceous silicon xerogel, and nickel nitrate is employed in the sol–gel process as a pore-adjusting reagent. SiC was produced in the carbothermal reduction of the binary xerogel at 1250 °C in an argon flow (40 cm 3 min −1) and purified by removing excess silica, carbon and other impurities. The purified SiC sample was characterized by XRD, SEM, TEM, and N 2 adsorption, and the results showed that the SiC sample had a surface area of 112 m 2 g −1 (BET) and an average pore diameter of about 10 nm.