Characterization of aging-induced microstructural changes in M250 maraging steel using magnetic parameters

The best combinations of mechanical properties (yield stress and fracture toughness) of M250 maraging steel is obtained through short-term thermal aging (3–10 h) at 755 K. This is attributed to the microstructure containing precipitation of intermetallic phases in austenite-free low-carbon martensite matrix. Over-aged microstructure, containing reverted austenite degrades the mechanical properties drastically. Hence, it necessitates identification of a suitable non-destructive evaluation (NDE) technique for detecting any reverted austenite unambiguously during aging. The influence of aging on microstructure, room temperature hardness and non-destructive magnetic parameters such as coercivity (H_c), saturation magnetization (M_s) and magnetic Barkhausen emission (MBE) RMS peak voltage is studied in order to derive correlations between these parameters in aged M250 maraging steel. Hardness was found to increase with precipitation of intermetallics during initial aging and decrease at longer durations due to austenite reversion. Among the different magnetic parameters studied, MBE RMS peak voltage was found to be very sensitive to austenite reversion (non-magnetic phase) as they decreased drastically up on initiation of austenite reversion. Hence, this parameter can be effectively utilized to detect and quantify the reverted austenite in maraging steel specimen. The present study clearly indicates that the combination of MBE RMS peak voltage and hardness can be used for unambiguous characterization of microstructural features of technological and practical importance (3–10 h of aging duration at 755 K) in M250 grade maraging steel.     

The interfacial surface tension of a quark-gluon plasma fireball in a hadronic medium

We calculate the interfacial surface tension of a QGP-fireball in a hadronic medium in the Ramanathan et al statistical model. The constancy of the ratio of the surface tension with the cube of the critical transition temperature is in overall accordance with lattice QCD findings. It is in complete agreement with a recent MIT bag model calculation of surface tension. The velocity of sound in the QGP droplet is predicted to be in the range (0.27 ± 0.02) times the velocity of light in vacuum and this value is independent of both the value of the transition temperature and the model parameters.      

Cu(In,Ga)Se2 thin-film solar cells with ZnS(O,OH), Zn-Cd-S(O,OH), and CdS buffer layers

Cu(In,Ga)Se₂ (CIGS) solar cell junctions prepared by chemical-bath-deposited (CBD) ZnS(O,OH), Zn-Cd-S(O,OH), and CdS buffer layers are discussed in this paper. The device performances are compared by applying CBD ZnS(O,OH), CBD Zn-Cd-S(O,OH), and CBD CdS buffer layers on similar CIGS absorbers. The CN impurities in CBD ZnS(O,OH) are identified with Fourier transform infrared spectroscopy (FTIR) techniques. The impurities containing carbon-nitrogen bonds are most likely cyanamide (NCN²⁻) or thiocyanate (SCN⁻), which resulted from the chemical reaction of thiourea and ammonia.     

Modular synthesis of cyclic peptidomimetics inspired by gamma-turns

[reaction: see text] A series of peptidomimetics based on a gamma-turn motif were synthesized using a modular approach, in which N-protected piperidones were reacted with a selection of 2-hydroxyalkyl azides derived from common l-amino acids. Hydrolysis of the initially formed iminium ethers afforded the targeted series of substituted 1,4-diazepin-5-ones.     

On the reactivity of 3,4-dimethoxycarbonyl-2-pyrazolines with dimethyl acetylenedicarboxylate

The title pyrazolines react with dimethyl acetylenedicarboxylate to give 1-alkyl-3,4,5-trimethoxycarbonylpyrazoles.