Deposition of hydroxyapatite on SiC nanotubes in simulated body fluid

SiC nanotubes can become candidate reinforcement materials for dental and orthopedic implants due to their light weight and excellent mechanical properties. However, the development of bioactive SiC materials has not been reported. In this study, hydroxyapatites were found on SiC nanotubes treated with NaOH and subsequently HCl solution after soaking in simulated body fluid. On the other hand, hydroxyapatites did not deposit on as-received SiC nanotubes, the SiC nanotubes with NH4OH solution treatment and SiC bulk materials with NaOH and subsequently HCl solution treatment. Therefore, we succeeded in the development of bioactive SiC nanotubes by downsizing SiC materials to nanometer size and treating with NaOH and subsequently HCl solutions for the first time

Comprehensive Understanding of Hillocks and Ion Tracks in Ceramics Irradiated with Swift Heavy Ions

Amorphizable ceramics (LiNbO3, ZrSiO4, and Gd3Ga5O12) were irradiated with 200 MeV Au ions at an oblique incidence angle, and the as-irradiated samples were observed by transmission electron microscopy (TEM). Ion tracks in amorphizable ceramics are confirmed to be homogenous along the ion paths. Magnified TEM images show the formation of bell-shaped hillocks. The ion track diameter and hillock diameter are similar for all the amorphizable ceramics, while there is a tendency for the hillocks to be slightly bigger than the ion tracks. For SrTiO3 (STO) and 0.5 wt% niobium-doped STO (Nb-STO), whose hillock formation has not been fully explored, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO. The material dependence of the nanostructure formation is explained in terms of the intricate recrystallization process

Synthesis and formation mechanism of novel double-thick-walled silicon carbide nanotubes from multiwalled carbon nanotubes

　In this study, double-thick-walled (DTW) silicon carbide (SiC) nanotubes, the walls of which comprise connected disordered polycrystalline nanograins, were successfully synthesized for the first time via the reaction of multiwalled carbon nanotubes (MWCNTs) with Si powder. DTW SiC nanotubes exhibit novel properties unlike other SiC nanomaterials, owing to their intriguing geometries. The DTW SiC nanotubes had a wall thickness exceeding 20 nm, regardless of the external diameter, as indicated by transmission electron microscopy results. The DTW SiC nanotubes with a spacing of above 30 nm between the outer and inner nanotubes exhibited perfect double-walled structures. The inner and outer nanotubes were not connected in any region. When all the carbon was transformed into SiC, the volume of carbon increased to 2.2 times the initial value. These results reveal that DTW SiC nanotubes with perfect structures cannot be synthesized without an MWCNT wall thickness of at least 50 nm. Several types of DTW SiC nanotubes with different morphologies, such as diameter, end structure, and distance between the inner and outer nanotubes, were synthesized. The morphology of DTW SiC nanotubes can be controlled by changing the wall thickness and/or diameter of the original MWCNTs and the reaction conditions

Synthesis of new structured hybrid carbon nanomaterials by ion irradiation of C-SiC coaxial nanotubes

　これまでに、C-SiC同軸ナノチューブの創製に成功しているが、これらC-SiC同軸ナノチューブのイオン照射を行ったところ、SiCナノチューブ内に新奇カーボンナノ材料の創製に成功したので報告する。　室温におけるイオン照射後のC-SiC同軸ナノチューブの透過型電子顕微鏡(TEM)写真より、外側のSiCはアモルファスに変化するが、内部のカーボン層は結晶性を維持していることが分かった。さらに、元々存在したナノチューブの径方向に垂直なカーボン層だけでなく、径方向に平行な新しいカーボン層が、イオン照射後に出現した。これらの結果から、アモルファスSiCナノチューブ内に、長さ方向に積層した50nm以下の微小円状グラフェンと多層カーボンナノチューブが複合化された新奇構造を有するハイブリッドカーボンナノ材料の創製に成功したことが示唆された。第29回 日本MRS年次大

Ion Irradiation Induced Synthesis of Novel Amorphous Double-Thick-Walled Silicon Carbide Nanotubes

　The synthesis of new structured SiC nanomaterials with novel properties is required because there is the possibility that they have novel properties relative to bulk SiC materials. We also have synthesized polycrystalline double-thick-walled (DTW) SiC nanotubes. Herein, we report the successful synthesis of novel amorphous DTW SiC nanotubes for the first time.　The degree of crystallinity of the SiC nanotube was decreasing with growing irradiation damage, and the SiC crystals were completely amorphized when irradiated at 3.2 dpa. According to these TEM images, the double-walled structure in the amorphous SiC nanotube was maintained even after ion irradiation. When the irradiation damage increased up to 24.0 dpa, the amorphous DTW SiC nanotube altered to the amorphous SiC nanowire.The 9th International Symposium on Surface Science (ISSS9

Synthesis of Polycrystalline and Amorphous Double-Thick-Walled Silicon Carbide Nanotubes

　The formation of novel structured SiC nanomaterials with new properties is required because there is the possibility that they have novel properties relative to bulk SiC materials. Polycrystalline double-thick-walled (DTW) SiC nanotubes were successful synthesized by the reaction of multi-walled carbon nanotubes with Si powder. We also synthesized novel amorphous DTW SiC nanotubes for the first time.　The degree of crystallinity of the SiC nanotube was decreasing with growing irradiation damage, and the SiC crystals were completely amorphized when irradiated at 3.2 dpa. According to these TEM images, the double-walled structure in the amorphous SiC nanotube was maintained even after ion irradiation. When the irradiation damage increased up to 24.0 dpa, the amorphous DTW SiC nanotube altered to the amorphous SiC nanowire.Materials Research Meeting 202