Fiber-optic LIBS for evaluation of surface hardness using ambient gas emission

Laser induced breakdown spectroscopy (LIBS) offers a unique tool for in-situ and remote analysis of sample characteristics. Recently, LIBS has been used to evaluate the hardness of a material. This approach capitalizes on the findings that harder surface produce faster laser-induced plasma shockwave, eventually giving rise to higher density plasmas. This promotes excitation and ionization of neutral atoms. Thus, the ratio of the ionic to neutral emission intensity and the electron temperature from LIBS measurements allows us to evaluate the surface hardness. In the present study, we assess the potential use of emission lines from ambient gas instead of that from investigated elements to diagnose surface hardness using a portable fiber-optic LIBS device.11th International Conference on Laser-Induced Breakdown Spectroscopy (LIBS2020

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

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

Application of MCR analysis to time-resolved LIBS measurement using liquid jet sampling method

In LIBS measurement of a solution of metal ions, the emission spectrum shows very complicated structure, where electronic transition bands of metal ions and neutrals are overlapped each other. If we know kinds of the metal ions prior to the LIBS measurement, we assign the electronic transition bands based on spectroscopic database. On the other hand, when there is no information, the assignment becomes tough work. In this study, focusing on similarity of emission decay from the same metal species, we design to classify the emission bands into groups using multivariate curve resolution by alternating least-squares (MCR-ALS). Although the MCR-ALS method was applied to the LIBS analysis in order to explore kinetics of ionic recombination and molecular formation within the plasma, there has been few applications on the LIBS. In this work, we observed time-resolved LIBS spectra of an aqueous solution containing Mo and Sr ions by ultra-thin liquid jet sampling method, and analyzed a series of the LIBS spectra using the MCR-ALS. Though the analysis, we discuss possibility to deconvolute a complicated LIBS spectrum into the groups of emission bands of each metal species.11th International Conference on Laser-Induced Breakdown Spectroscop

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

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