No abstract

Irradiation of 9-diazo-1,8-diazafluorene initiates a series of photochemical reactions that lead to isomerization to the diazirine and to loss of nitrogen to form a carbene. The carbene has a triplet ground state but reacts primarily from its upper singlet state. The chemical and physical properties of the diazo compound and the carbene are compared with those for 9-diazofluorene. The differences between these compounds are assigned tentatively to a combination of through-space interaction of the lone pair electrons of the heteroatomic ring atoms with the nonbonding in-plane orbital of the carbene carbon and the electron-withdrawing nature of the pyridine-like nitrogens.

The photochemistry of 9-diazo-l,8-diazafluorene (18DAF) depends on the wavelength of the irradiating light. When photolyzed at ca. 310 nm, into a -* absorption band, excited 18DAF rearranges to a diazirine and loses nitrogen to form the carbene 1,8-diazafluorenylidene (18FL) exclusively in the singlet state. However, when 18DAF is photolyzed at ca. 420 nm, into the -* band, no diazirine is formed, but triplet 18FL is formed directly along (4) Turro, N.

No abstract

Test bends of L415M hot induction bend of 508 mm OD×14.3 mm WT used in –45°C areas were conducted. The bending and tempering process parameters were designed, the influences of bending and tempering process parameters on impact toughness at –45°C and microstructure of tangent weld and bend weld were investigated. Hot induction bend was produced by the process of local induction heating+fast water quenching. After tempering treatment, the weld contained martensite-austenite (M-A) islands, carbide precipitations, welded column crystal structure and little pearlite (P), and the brittle fracture surface contained S segregation, the temper brittleness of the weld occurred, which lead to impact energy of bend weld to be lower than 40 J at –45°C. Without post-bending tempering treatment, the microstructures of bend weld was a composite of polygonal ferrite (PF) and granular bainite (GB) with small size and uniform distribution, the coarse column structure and acicular ferrite (AF) disappeared in the weld, so the impact energy of bend weld was higher than 70 J at –45°C, but the impact energy of tangent weld was very poor. It suggests that the process of overall induction of heating + fast water quenching + no tempering treatment is more reasonable, the process ensures that the impact toughness at –45°C, strength and other properties of bend meet the requirements of CDP-S-OGP-PL-016-2011-2.