Tamikuni Komatsu

Polycondensation/pyrolysis of tris-s-triazine derivatives leading to graphite-like carbon nitrides

Polycondensation/pyrolysis of 2,5,8-tricarbodiimide-tris-s-triazine and its derivatives gave hexagonal graphite-like pseudo carbon nitrides, CH0.3–0.08N1.0–0.63, composed of tris-s-triazine nuclei. The materials were stable up to 600–800°C under an inert atmosphere depending on their nitrogen content.

Prototype carbon nitrides similar to the symmetrictriangular form of melon

Solid polymerization of 2,5,8-tricarbodiimide-tris-s-triazine potassium salt (potassium melonate) and 2,5,8-trichloro-tris-s-triazine (cyameluryl trichloride) gave a symmetric triangular form of a prototype carbon nitride which is deammonation-polycondensed with fifteen 2,5,8-triamino-tris-s-triazine molecules.

Synthesis and characterization of a shock-synthesized cubic B–C–N solid solution of composition BC2.5N

A cubic BC2.5N solid solution (c-BC2.5N) was synthesized in 18% yield by shock-compression of a hexagonal BC2.5N compound. c-BC2.5N was confirmed to have a diamond structure without a long range order of atomic arrangement. The material is a polycrystal composed of microcrystals of 5–20 nm in size. All constituent atoms are teterahedrally coordinated, giving C—C, C—B, C—N, and B—N bonds, and are homogeneously distributed on the lattice planes rather than showing a full short range order of atomic arrangement.

Shock synthesis and characterization of new diamond-like carbon nitrides

New diamond-like carbon nitrides (C–N heterodiamonds), no less hard than diamond, have been synthesized for the first time in bulk form by shock compression of graphitic carbon nitride precursors in the dynamic pressure–temperature range around 30 GPa–3000 K. Typically, the C2N heterodiamond obtained from graphitic C3N2 consists of sp3-bonded carbon and nitrogen atoms, belongs to a diamond crystal system, has a lattice constant of 0.351 ± 0.001 nm, 1.6–1.9% smaller than that of diamond, is able to scratch the surface of a sintered-diamond and is very IR active due to the dipole moment of the C–N single bonds. These properties suggest that it could be slightly harder than diamond.

The effects of pressure on drawing polyoxymethylene: 2. Drawn fibre properties and structure

Abstract Superdrawn polyoxymethylene fibres produced by pressurized drawing are dense and transparent, and have good mechanical properties. Maximum tensile modulus and strength and apparent density were found to be 58 GPa, 2.0 GPa and 1.45 g cm −3 , respectively. A study was made of the effects of pressure on the mechanical properties and structural characteristics of drawn fibres. The relationship between these parameters is discussed.

Heat resistance of a shock-synthesized B–C–N heterodiamond

The heat resistance of a B–C–N heterodiamond (c-BC2.5N) has been investigated and compared with that of the starting material (h-BC2.5N), graphite, diamond, c-BN and h-BN. With regard to thermogravimetry c-BC2.5N showed partial pyrolysis up to 1300 °C and its thermal oxidation resistance lay between that of diamond and c-BN. The TG-residue of c-BC2.5N contained significant amounts of unchanged c-BC2.5N. This was due to coverage of c-BC2.5N by pyrolytically produced B2O3. The structure transition temperatures of the three cubic materials were in the range 1800–2000 °C at atmospheric pressure and increased in the order: c-BN ≲ C-BC2.5N < diamond. These characteristics of c-BC2.5N can be related to its diamond-type structure composed of hetero atoms.

The effects of pressure on drawing polyoxymethylene: 1. Processing

Abstract A new process has been developed for the continuous drawing of polymers under pressure. Draw ratios up to 34 were achieved by this process using polyoxymethylene. The pressure applied in the process acts effectively on the drawing behaviour, temperature, stress and velocity.

Novel emission properties of melem caused by the heavy metal effect of lanthanides(III) in a LB film

A novel emissive molecular system is constructed by the intercalation of the fluorophore melem (triamino-tri-s-triazine) within a Langmuir-Blodgett (LB) film of stearic acid with the periodic arrangement of lanthanides (Ln(III)), mainly Pr(III) with supporting of Eu(III). From emission spectra, decay curves, quantum yields and XPS measurements, it is clarified that the external heavy metal effect of Pr(III) on melem is much stronger in the film than in the bulk solid state, resulting in producing an unusual triplet state of melem. The triplet state of melem in the LB film donates the excitation energy to Pr(III) in the LB film, which is completely different from the energy transfer pathway of Pr-melem complex in the solid state through the singlet state of melem.

Bulk synthesis and characterization of graphite-like B-C-N and B-C-N heterodiamond compounds

High quality graphite-like B–C–N compounds used for the shock-synthesis of B–C–N heterodiamonds were bulk-synthesized in good yield by pyrolysis of the polymers between BCl3 and commercially available nitriles at 1773 K. It was elucidated that the series of obtained heterodiamond compounds are described by the formula CBxNx(BN)y composed of CBxNx and (BN)y segments and have an unusual structure in which diamond-like carbon atoms are randomly substituted for B/N atoms and (BN)y segments, based on IR, XPS and X-ray powder diffraction.

Preparation of carbon nitride C2N by shock-wave compression of poly(aminomethineimine)

Shock-wave compression of poly(aminomethineimine) under a pressure of 40 GPa produced no crystalline material but amorphous carbon nitrides having microscopically different morphologies, a quasi-spherically concentric closed-shell form, a random-layer-structure and a completely amorphous structure. These have the same composition, C2N, and the same chemical structure consisting of sp2 carbon and sp2 nitrogen.