Surface properties of laser processed ductile iron

On laser melt treatment,Sliding Wear of pearlitic ductile iron reduced from severe metallic wear to oxidative mild wear by nearly two orders of magnitude at 7.5 ms^–1 over a load range of 14–31 kg cm^–2; resistance toCavitation Erosion improved by a factor ofseven in corrosive media and surface hardness increased from 20–22 to 40–58 HR_c. Laser melting could effectively reduceCorrosion rates in dilute acids by nearly 40%.These improvements were caused by the ultrafine microstructure (1–41 ,DAS), microhardness (700–900,HV _0,1) and the consequent high resistance to plastic flow and subsurface crack initiation.In this investigation, pin-on-disc adhesive wear, ultrasonic vibratory cavitation erosion and potentiodynamic corrosion in synthetic sea water and 0.01 N H₂SO₄, were assessed after laser surface melting or transformation hardening of hyper-eutectic ductile iron, typically employed in automotive and marine engine components by using CO₂ CW or Nd-YAG pulsed high power laser. Also the processing parameters viz, beam power (P), scan rate (U), and specific energy intensity (P/UD _b ² ) for threshold and specific depth of transformation hardening or melting have been determined.     

Structural considerations from dielectric measurements on the aliphatic alcohols

Precise static dielectric constants are reported for methanol, ethanol, andn-propanol at 10,25, and 40° C and at pressures up to 3 kbar. The measurements were carried out by a low-frequency bridge method using a threeterminal, all-glass cell. An uncertainty of 0.05% is claimed for the data. The results are compared to data from previous investigations, whith the agreement in the absolute magnitude poor but the agreement in the pressure coefficient reasonable in most cases. The data are analyzed in terms of the Kirkwood correlation factorg _K as obtained from the Fröhlich equation. In all cases, theg _K factor decreases with increased pressure. The problems involved in calculating this factor from the experimental data are discussed, and it is shown that the trends ing _K are very dependent upon the assumptions made in isolating the liquid dipole moment from its gas-phase value. This fact also indicates that an interpretation of theg _K values in terms of stepwise association of correlation dipoles is premature at this time.     

Electron impact induced fragmentation of some 1,2,4-triazole derivatives

The mass spectra of eight 1,2,4-triazole derivaties have been recorded and found tao reveal extensive hydrogen and skeletal migrations. The structures of the fragments have been confirmed by deuterium labelling and exact mass measurement. The compounds revealed striking differences in their spectra depending on the nature of the substituents.     

Syntheses and structures of isomeric [6.6]- and [8.8]cyclophanes with 1,4-dioxabut-2-yne and 1,6-dioxahexa-2,4-diyne bridges

All three isomers (ortho, meta, and para) of [8.8]cyclophane bearing 1,6-dioxahexa-2,4-diyne bridges have been synthesized and structually characterized by single-crystal X-ray crystallography to determine the conformation of the cyclophanes and their cavity dimensions. The three isomeric [6.6]cyclophanes bearing 1,4-dioxabut-2-yne bridges have also been synthesized from but-2-yne-1,4-diol ditosylate and the isomeric dihydroxybenzenes. The [6.6]orthocyclophane has been structurally characterized by single-crystal X-ray crystallography. The energy-minimized structures from the semiempirical AM1 calculations of these cyclophanes compare very well with the structures obtained by X-ray crystallography.     

Block copolymerization initiated by Mn(III)-poly(ethylene glycol) redox system — general features and kinetics

The kinetics and mechanism of thermal polymerization of acrylonitrile initiated by Mn(III) pyrophosphate — poly(ethylene glycol) (PEG, molecular weight 6000) redox system in aqueous sulfuric acid medium was studied in the temperature range 30–60°C. The overall rates of polymerization and the disappearance of Mn³⁺ were determined. The polymerization was initiated by the organic free radical produced from the Mn³⁺-PEG reaction and the termination was by the metal ions. The rate of polymerization of acrylonitrile was found to be directly proportional to the square of the monomer concentration and first power of PEG concentration, and inversely proportional to the concentration of Mn³⁺. The rate of manganic ion disappearance was found to be directly proportional to manganic ion concentration and PEG concentration, and independent of the monomer concentration. Based on these observations, a plausible reaction scheme was suggested and suitable kinetic expressions were evaluated.