糸井 貴臣

Disposable bamboo chopsticks (DBCs) are difficult to recycle, which inevitably cause secondary pollution. Based on energy and environmental issues, we propose a facile strategy to fabricate floatable photocatalyst (fPC) coated onto DBCs, which can be flexibly used in water purification. The photocatalyst of titania and titanium carbide on bamboo (TiO2/TiC@b) was successfully constructed from TiC-Ti powders and DBCs using a coating technique followed heat treatment in carbon powder, and the fPC exhibited excellent photocatalytic activity under visible light irradation. The analysis results indicate that rutile TiO2 forms on TiC during heat treatment, achieving a low-density material with an average value of approximately 0.5233 g/cm3. The coatings of TiO2/TiC on the bamboo are firm and uniform, with a particle size of about 20–50 nm. XPS results show that a large amount of oxygen vacancies is generated, due to the reaction atmosphere of more carbon and less oxygen, further favoring to narrowing the band gap of TiO2. Furthermore, TiO2 formed on residual TiC would induce the formation of a heterojunction, which effectively inhibits the photogenerated electron–hole recombination via the charge transfer effect. Notably, the degradation of dye Rhodamine B (Rh.B) is 62.4% within 3 h, while a previous adsorption of 36.0% for 1 h. The excellent photocatalytic performance of TiO2/TiC@b can be attributed to the enhanced reaction at the water/air interface due to the reduced light loss in water, improved visible-light response, increased accessible area and charge transfer effect. Our findings show that the proposed strategy achieves a simple, low-cost, and mass-producible method to fabricate fPC onto the used DBCs, which is expected to applied in multiple fields, especially in waste recycling and water treatment.

Photocatalytic reduction of CO2 into C2,3 hydrocarbons completes a C‐neutral cycle. The reaction pathways of photocatalytic generation of C2,3 paraffin and C2H4 from CO2 are mostly unclear. Herein, a Co0–ZrO2 photocatalyst converted CO2 into C1–3 paraffin, while selectively converting CO into C2H4 and C3H6 (6.0 ± 0.6 μmol h−1 gcat−1, 70 mol%) only under UV–visible light. The photocatalytic cycle was conducted under 13CO and H2, with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C2H4 and C3H6 increased up to 61–87 mol%, attributed to the accumulation of CH2 species at the interface between Co0 nanoparticles and the ZrO2 surface. CO2 adsorbed onto the O vacancies of the ZrO2 surface, with resulting COH species undergoing hydrogenation on the Co0 surface to yield C1–3 paraffin using either H2 or H2O (g, l) as the reductant. In contrast, CO adsorbed on the Co0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO2, respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO2 into paraffin and CO to olefins.

Abstract The band gap of rutile TiO₂ has been narrowed, via the formation of oxygen vacancies (OVs) during heat treatment in carbon powder (cHT) with embedding TiO₂ coatings. The narrowed band gap efficiently improves the visible light response of TiO₂ coatings, to further enhance the visible-light-driven photocatalytic activity. The change in OVs during cHT has been studied by manipulation of cHT temperature and time. The effect of OVs on the band structure of nonstoichiometric TiO_2-x has been further calculated by first-principles calculations. With raising the temperature, SEM images show that the nano-size fiber-like structure forms on the surface of TiO₂ coatings, and the amount of the fiber-like structure significantly increases and their size changes from nano to micro under 800 °C, contributing to cause an increase in accessible surface area. The UV–Vis results reveal that the band gap of TiO₂ has been narrowed during cHT, due to the formed oxygen vacancies. The XPS results further confirm that the formation of surface defects including OVs, and the XPS depth profile further shows the decreased relative amount of O whereas increased relative amount of carbon. Notably, after cHT for TiO₂ coatings, the photocatalytic activity first increases then decreases with raising the temperature, achieving approximately 3 times at 850 °C. The first-principles calculation suggest that the OVs in TiO₂ coatings with localized electrons could facilitate the band gap narrowing, further favoring to enhance the photocatalytic activity under visible light.

To enhanced photocatalytic activity and stability of titania (TiO2) coatings, graphene oxide (GO) forms on the surface of TiO2 coatings is fabricated by electrophoretic deposition (EPD). The results show the effect of EPD time on the formed hydroxyl groups from GO is significant, especially the controllable amount of GO by adjusting EPD time. The change in surface morphology of the GO on TiO2 coatings is obvious, showing an increased amount of GO. Owing to the effect of charge transfer between TiO2 and GO, the TiO2/GO composites coatings exhibit excellent and stable photocatalytic activity. Notably, the cycle result of the sample after ultrasonic cleaning every 10 min reveal that the combination of TiO2 and GO is satisfactory.

Silicon (Si) has attracted considerable interest as a negative electrode material for next-generation lithium (Li)-ion batteries because of its high capacity density. In this study, ex situ electron microscopy was applied to observe Si negative electrodes under different charge states within an actual battery structure to reveal the Li intrusion direction and the effects of Li concentration on the electrode structure. All of the processes from disassembly of the charged battery and preparation of specimens for use in electron microscopy observation to specimen transport to the electron microscopes were performed under non-atmospheric exposure conditions. The orientation of the single-crystal Si powder in the charged state was observed by electron backscatter diffraction, indicating that lithiation occurred preferentially along the (110) plane of Si. The initial stage of amorphization was observed by high-angle annular dark field-scanning transmission electron microscopy, demonstrating that the Li atoms occupied the tetrahedral sites of Si crystals, and that the crystal structure was destroyed via the severing of Si-Si bonds between the {111} planes. During the charge reaction, Li occupied the tetrahedral sites via intrusion along the &lt 110&lt direction of Si, and amorphization proceeded as the Li concentration increased. Thus, the amorphous region grew preferentially in the &lt 110&lt direction of Si.

A SEI（Solid Electrolyte Interphase）is formed on the surface layer of the negative electrode active material of a lithium ion secondary battery（LIB）during the initial charging process, and its morphology and structure significantly affect performance and safety. In this study, by conducting ex-situ experiments, SEM, TEM and STEM-EELS observations were performed on Si negative electrodes under charge state within an actual battery and Si negative electrodes directly charged on a TEM thin film, revealed morphology and structure of the SEI. All of the processes from specimen preparation for electron microscopy observation to specimen transport were performed under non-atmospheric exposure conditions. The SEI on the surface of the Si negative electrode grew thicker as the charge depth increased. On the other hands, LixSi amorphous phase due to the lithiation by solid-state reaction was confirmed inside the Si negative electrode. It was found that Li2O was formed on the most surface of the Si negative electrode at the initial stage of charging, and the SEI was mainly composed of Li2O. The SEI of about 1 µm was observed on the Si negative electrode after 40％ charge, and the thickness of the SEI decreased to less than 1/5 after discharge.

Mg alloys with a long-period stacking-order (LPSO) phase are categorized into two types. Those in which the LPSO phase forms in as-cast state are referred to as Type I, while those in which the LPSO phase does not appear until a heat treatment is performed are categorized as Type II. However, the reason that gives rise to these two types of alloy is still not well understood. In the present study, in an attempt to clarify this issue, three different Mg-85(Al,Zn)(6)Gd-9 quaternary alloys were prepared. The alpha-Mg, Al2Gd, Mg3Gd and LPSO phases were identified in the as-cast quaternary alloys by microstructural observations, composition analysis and crystal structure analysis using electron probe microanalysis and X-ray diffraction. The results indicated that all the quaternary alloys could be categorized as Type I, even though ternary Mg(85)Al(6)GD(9) and Mg85Zn6Gd9 alloys were Type II. The crystal structure of the LPSO phase in the as-cast alloys is considered to be18R with dilute solute elements, and the fraction of this phase increases with increasing Zn content. The presence of this phase is thought to be the cause of destabilization of the primary Al2Gd phase. It is thus concluded that the relative stability of phases in the vicinity of the LPSO phase is crucial in determining the type of Mg alloy formed.

Be careful of false “solar fuel” converted from adventitious carbon! Time course of isotope-labeled 13CO2 photoconversion into a 13C-product was successfully monitored using a Ag–Zr oxide photocatalyst.

The 6061-T6 sheet and the DP 780 steel sheet were joined under the condition with the gap length d of 1.17 to 1.42 mm and discharge energy W of 3.0 kJ. The impact speed ranged from 430 to 460 m/s. The weld width showed a tendency to increase due to the increase of the collision speed. However, when the gap length exceeds 1.59 mm (impact speed of &gt 460 m/s), the weld width became narrow. Considering that the electromagnetic force continues to apply on the flyer sheet after collides with the fixed sheet, it is desirable to perform the welding in a time shorter than the time tm when the collision time reaches the maximum current value. Therefore, the collision time is considered to be one of factors that affect the welding condition. As a result of experiments in consideration of above conditions, it was possible to achieve a strong lap joint of the 6061-T6 sheet and the DP 980 steel sheet, although the welding condition was limited as compared with the case of the DP 780 steel sheet. Thus, sound lap joint between 6061-T6 sheet and high-tensile steel sheet with 1 GPa class was achieved by magnetic pulse welding.

Mg alloys with long period stacking ordered (LPSO) phases are categorized into two types. Mg alloys where the LPSO phase forms in as-cast state are categorized as Type I, while those where the LPSO phase does not appear in as-cast state but forms during heat treatment are categorized as Type H. However, the origin of the formation type of Mg alloys with LPSO phases still remains poorly understood. In the present study, three different Mg-85 (Al, Zn)(6)Gd-9 quaternary alloys were prepared to elucidate the dominant factors that determine the formation type of Mg alloys with LPSO phases. The a-Mg. Al2Gd, Mg3Gd and LPSO phases were characterized in the as-cast quaternary alloys by microstructural observation, composition analysis and crystal structure analysis by using electron probe microanalysis and X -ray diffraction. It indicates that all the quaternary alloys are categorized as Type I even though the original two ternary Mg85Al6Gd9 and Mg85Zn6Gd9 alloys are categorized as Type II. The crystal structure of the LPSO phases observed in the as-cast alloys is considered to be 18R with dilute solute elements. The amount of the LPSO phases in the as-cast state increases with increasing the 7,n content in the alloys. it is considered to be the cause of destabilization of the primary crystallized Al2Gd phase by the addition of Zn and hence relative stabilization of the LPSO phases. It is thus concluded that the relative phase stability in the vicinity of the LPSO phase is considered to be crucial for determination of the formation type of Mg alloys with LPSO phases.

Microstructure and mechanical property of the Mg-TM (TM=Ni or Cu)-Y alloys were investigated. Results revealed that Mg phase, Long period stacking ordered (LPSO) phase, and Mg2TM phase were formed in the Mg-TM-Y alloy around the composition ratios of TM and Y are 1:1 or 1:2. Tensile test clearly showed relationship between the mechanical property and microstructure in Mg-Ni-Y cast alloy. The 0.2% proof stress (σ0.2) of the Mg-Ni-Y cast alloy increase with the increasing solute elements contents, while the elongation decreases. This result indicated that the Mg-TM-Y alloy with the composition ratios of TM and Y are 1:1 or 1:2 have both high proof stress and appropriate elongation. It was suggested that the LPSO phase was appropriate strengthening phase in the Mg-rich region in the Mg-TM-Y alloy system. Basal texture of the LPSO and Mg phases was formed by hot-rolling in the sheet plane and the Mg2TM phase was dispersed in the Mg phase. The Mg97Cu1Y2 rolled sheet showed highσ0.2 about 350 MPa at room temperature. Furthermore, formation of an oxide film on the Mg-Cu-Y alloy was investigated at 973 K in air. As a result, it was suggested that the Y2O3 film was formed on the re-melted Mg-Cu-Y alloy surface as an incombustible oxide film.

We successfully applied mechanical coating technique to prepare Ti coatings on the substrates of steel balls and stainless steel balls. The prepared samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The weight increase of the ball substrates and the average thickness of Ti coatings were also monitored. The results show that continuous Ti coatings were prepared at different revolution speeds after different durations. Higher revolution speed can accelerate the formation of continuous Ti coatings. Substrate hardness also markedly affected the formation of Ti coatings. Specifically, the substance with lower surface hardness was more suitable as the substrate on which to prepare Ti coatings. The substrate material plays a key role in the formation of Ti coatings. Specifically, Ti coatings formed more easily on metal/alloy balls than ceramic balls. The above conclusion can also be applied to other metal or alloy coatings on metal/alloy and ceramic substrates.