Polishing Performance of a Recycled Grinding Wheel Using Grinding Wheel Scraps for the Wet Polishing of Stainless-Steel Sheets

The surfaces of large austenitic stainless-steel sheets, which have side lengths of at least 1 m a sheet thickness of at least 6 mm, used for food tanks and sliding plates in seismic isolation devices, must be finished to a mirror surface. Polishing is performed to improve the surface quality of such sheets and dry machining is typically applied. The problems associated with dry machining are the exhaust heat of machining and treatment of chips. A transition to wet machining is required to solve these problems. In our laboratory, we have developed a wet polishing machine and researched the selection of grinding wheels to develop wet polishing technology for large stainless-steel sheets. In this study, to reduce tool cost and reuse resources, we attempted to manufacture a recycled grinding wheel using snippets of grinding wheel scraps. A polyvinyl alcohol (PVA) aqueous solution was used as the bonding agent for the recycled grinding wheel to reduce environmental load. To overcome the ease of dissolution of PVA in water, we attempted to improve the water resistance of the PVA aqueous solution by incorporating an organic titanium compound. This is one of our efforts to contribute to sustainable development goals. The results are summarized below. (1) A recycled grinding wheel was fabricated by kneading crushed pieces of grinding wheel scrap with a bonding agent. (2) The maintenance of the shape of the recycled grinding wheel was controlled by the concentration of the bonding agent. (3) The recycled grinding wheel with a PVA bonding agent was vulnerable to water. In contrast, the recycled grinding wheel to which the organic titanium compound was added exhibited improved water resistance. (4) The polishing of stainless-steel sheets using the plain PVA recycled wheel was relatively ineffective, but polishing using the recycled wheel with the titanium additive was comparable to polishing with a new grinding wheel.

TITANIUM OXIDE-OXIFLUORIDE SYNTHESIS AND STUDY OF ITS PHOTOCATALYTIC PROPERTIES

The research article discusses a new method for the photocatalyst synthesis based on a mixture of titanium oxide - titanium oxyfluoride. The synthesis was performed by dissolving titanium metal in an acidified solution of ammonium bifluoride, followed by oxidation to the highest oxidation state and hydrolysis with ammonia to obtain metatitanic acid. The decomposition of metatitanic acid was carried out in a muffle furnace at a temperature of 380°C. It was found that during the precipitation of metatitanic acid, the titanium compound with the fluoride ion also passes into the precipitate, which, after calcination, transforms into titanium oxyfluoride. Photocatalytic activity was determined by the oxidation reaction of the methyl orange dye upon irradiation with ultraviolet radiation. The source of ultraviolet radiation was a DRT-125 lamp with a wavelength in the range of 200-400 nm. Suspensions containing 60 mg/L of the dye and various contents of the photocatalyst in the concentration range of 1-7 g/L were subjected to oxidation. The construction of the calibration graph and the determination of the concentrations were carried out on an SF-2000 spectrophotometer at a wavelength of 466.4 nm. The operating wavelength was determined by scanning the solution in the wavelength range of 200-800 nm. It was found that as a result of oxidation, the solution pH shifts to the acidic side to 3.5, which leads to a shift in the wavelength of the maximum absorption; in this regard, the solutions pH was adjusted to the same values.

Bis(pyrene)metal complexes of vanadium, niobium and titanium: isolable homoleptic pyrene complexes of transition metals

Reduction of VCl3(THF)3(THF is tetrahydrofuran) and NbCl4(THF)2by alkali metal pyrene radical anion salts in THF affords the paramagnetic sandwich complexes bis[(1,2,3,3a,10a,10b-η)-pyrene]vanadium(0), [V(C16H10)2], and bis[(1,2,3,3a,10a,10b-η)-pyrene]niobium(0), [Nb(C16H10)2]. Treatment of tris(naphthalene)titanate(2−) with pyrene provides the isoelectronic titanium species, isolated as an (18-crown-6)potassium salt, namelycatena-poly[[(18-crown-6)potassium]-μ-[(1,2-η:1,2,3,3a,10a,10b-η)-pyrene]-titanate(−I)-μ-[(1,2,3,3a,10a,10b-η:6,7-η)-pyrene]], {[K(C12H24O6)][Ti(C16H10)2]}n. The first two compounds have very similar packing, with neighboring molecules arranged orthogonally to one another, such that aromatic donor–acceptor interactions are likely responsible for the specific arrangement. The asymmetric unit contains a half-occupancy metal center η6-coordinated to one pyrene ligand, with the fullM(pyrene)2molecule generated by a crystallographic inversion center. In the titanium compound, the cations and anions are in alternating contact throughout the crystal structure, in one-dimensional chains along the [101] direction. As in the other two compounds, the asymmetric unit contains a half-occupancy Ti atom η6-coordinated to one pyrene ligand. Additionally, the asymmetric unit contains one half of an (18-crown-6)potassium cation, located on a crystallographic inversion center coincident with the K atom. The full formula units are generated by those inversion centers. In all three structures, the pyrene ligands are eclipsed and sandwich the metals in one of two inversion-related sites. These species are of interest as the first isolable homoleptic pyrene transition metal complexes to be described in the scientific literature.

Research on Grain Refinement Effect of Al-5Ti-C Alloy on Pure Aluminum and its Attenuation Mechanism

The texture feature and grain refinement effect of Al-5Ti-C alloy on pure aluminum were analyzed and its attenuation mechanism was discussed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy (OM) and other experimental methods.The results show that: Al-5Ti-C alloy is composed of Al, TiAl3 and TiC. Al-5Ti-C alloy has a good grain refining capacity for commercially pure aluminum. During the heat preservation process, due to precipitation of titanium compound in the aluminum melt, refinement effect of Al-Ti-C alloy is declined.