热处理工艺对40CrMnMo钢硬度及冲击韧性的影响

本文探讨了各种不同的热处理工艺所获得的各种组织状态对40CrMnMo钢的硬度和冲击韧性的影响,结果表明：该钢调质状态的冲击韧性较高，但硬度偏低；而等温下贝氏体组织状态，硬度较高，冲击韧性适中,对于承受较小冲击载荷而要求有较高硬度的零件，应以下贝氏体组织状态最佳．     

Corrosion and oxidation properties of NiCr coatings sprayed in presence of gas shroud system

The oxidation of a NiCr bond coat during air plasma spraying was controlled by designing a gas shroud system attached to the plasma torch nozzle. Two nozzles, termed as “normal” and “high-speed” nozzles examined the effect of nozzle internal design on the microstructure and phase structure of coatings. X-ray diffraction and SEM morphologies showed that the shroud system reduced the oxidation of NiCr particles during the spray process. Compared with conventional air plasma spraying, the argon gas shroud reduced the coating hardness because the volume fraction of partially melted particles increased. The high-speed nozzle reduced the oxidation and hardness of NiCr coatings due to the increase of partially melted particles in the coatings.     

Effect of annealing on the nanoscratch behavior of multilayer Si0.8Ge0.2/Si films

In this study, we examined the nanoscratch behavior of annealed multilayered silicon-germanium (SiGe) films comprising alternating sublayers (Si) deposited using an ultrahigh-vacuum chemical vapor deposition (UHV/CVD) system. Annealing consisted of ex situ thermal treatment in a furnace system. We used a nanoscratch technique to investigate the nanotribological behavior of the SiGe films and atomic force microscopy (AFM) to observe deformation phenomena. Our AFM morphological studies of the SiGe films revealed that pile-up phenomena occurred on both sides of each scratch. The scratched surfaces of the SiGe films that had been subjected to various annealing conditions exhibited significantly different features, it is conjectured that cracking dominates in the case of SiGe films while ploughing dominates during the scratching process. We obtained higher coefficients of friction (μ) when the ramped force was set at 6000 μN, rather than 2000 μN, suggesting that annealing of SiGe films leads to higher shear resistance; annealing treatment not only produced misfit dislocations in the form of a significantly wavy sliding surface but also promoted scratching resistance.     

Void formation in zirconium under irradiation in the high-voltage electron microscope

NUCLEAR TRACKS IN SOLIDS PRINCIPLES AND APPLICATIONS, by Robert L Fleischer, P. Buford Price and Robert M. Walker. University of California Press 1975. 605 pages, £20.50.

NEW USES OF ION ACCELERATORS, J. F. Ziegler, ed. Plenum Publishing Corporation, $33.60.

ATOMIC COLLISIONS IN SOUDS, Volumes 1 and 2, Edited by S. Datz, B. R. Appleton and C. D. Moak. Plenum Publishing Corporation, New York, $90.00.

HYPERFINE INTERACTIONS, Journal devoted to research in the border region of solid state, atomic and nuclear physics. Editors: B. I. Deutch and H. de Waard. North-Holland, Amsterdam, $46.95 per year.

ATOMIC ENERGY LEVELS AND GROTRIAN DIAGRAMS, VOL. 1, HYDROGEN I-PHOSPHORUS XV, by S. Bashkin and J. 0. Stoner, Jr., North-Holland Publishing Co., Amsterdam 1975. 615 pp., $59.95, Dfl. 150.00.

THE DYNAMICS OF SPECTROSCOPIC TRANSITIONS, by James D. Macomber. John Wiley and Sons, New York, 1976, $23.00, £1.50. 332 pages, 93 figures, 67 bibliographical references, 37 problems, a general index and a key to symbols.     

o-C8 Carbon: a New Allotrope of Superhard Carbon

An orthonormal crystal of carbon with PMMA space group (o-C₈) was found to be a stable superhard carbon allotrope by particle swarm optimization algorithm and density functional calculations. The phonon spectrum calculations demonstrate that the o-C₈ carbon phase is dynamically stable. The volume compression calculations show that it is highly incompressible, with bulk modulus of 298.6 GPa. The calculations demonstrate that it is a low-density superhard material with density of 2.993 g/cm³ and Vickers hardness of 82.4 GPa.     

Internal and external eigenvalue problems of Hermitian operators and their use in electronic structure theory

Within the fragment resolution of molecular systems the conceptual and interpretative advantages of using the separate eigenvalue problems for the internal and external part of the Hermitian matrix representing a physical quantity in quantum mechanics are examined. By definition, these two parts accordingly combine only the diagonal and off-diagonal subsystem-resolved blocks of matrix elements. These two partial eigenvalue problems bring about the matrix internal or external decouplings, respectively, which have recently been used in several interpretations of the molecular electronic structure. A character and structure of the external eigensolutions is examined in some detail and their recent applications in the Charge Sensitivity Analysis—to extract the most important electron-transfer effects between constituent atoms of model chemisorption systems, and in the Molecular-Orbital theory—to precisely identify the inter-orbital flows of electrons, are summarized and commented upon. The grouping relation, for combining the external/internal eigensolutions into those for the whole matrix, is derived in the context of the complementary “rotations” of the basis set vectors.     

The effects of organoclay on the morphology and mechanical properties of PAI/clay nanocomposites coatings prepared by the ultrasonication assisted process

In this research, solvent based polyamide – imide (PAI)/clay nanocomposites were prepared successfully using the solution dispersion technique. With the assistance of the ultrasonic wave, the effect of the ultrasonic wave time on the microstructure of 3 wt% PAI/C20A nanocomposite (NC) was investigated. Then, the best ultrasonic parameters were selected and the effects of the concentration of Cloisite 20A (C20A) (1, 3 and 5 wt% C20A) on the microstructure and mechanical properties (adhesion, hardness, flexibility, wear and impact) of NCs were investigated. The PAI, C20A and nanocomposites (NC)s were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), and Wide-angle X-ray diffraction (WAXD). The results showed that the sample with 1 and 3 wt% C20A had better mechanical properties, as compared to the pure PAI and the 5 wt% NC.     

Preparation and properties of electroless Ni-P-SiO2 composite coatings

Dispersible SiO₂ nanoparticles were co-deposited with electroless Ni-P coating onto AISI-1045 steel substrates in the absence of any surfactants in plating bath. The resulting Ni-P/nano-SiO₂ composite coatings were heat-treated for 1 h at 200 °C, 400 °C, and 600 °C, respectively. The hardness and wear resistance of the heat-treated composite coatings were measured. Moreover, the structural changes of the composite coatings before and after heat treatment were investigated by means of X-ray diffraction (XRD), while their elemental composition and morphology were analyzed using an energy dispersive spectrometer (EDS) and a scanning electron microscope (SEM). Results show that co-deposited SiO₂ particles contributed to increase the hardness and wear resistance of electroless Ni-P coating, and the composite coating heat-treated at about 400 °C had the maximum hardness and wear resistance.     

The influence of processing gas on the mechanical properties of sputtered B-C-N-H films

This work describes the microstructure and mechanical properties of B-C-N-H films synthesized by medium frequency magnetron sputtering from a boron target in a N₂ + CH₄ + Ar gas mixture. The increase in the CH₄ flow rate increases the carbonaceous compound species, causes the increase of the C atomic concentration and promotes the formation of sp³-hybridized carbon. The change of hardness with the CH₄ flow rate had a relationship with the residual stress. The coefficient of friction was reduced approximately from 0.8 to 0.18, and wear resistance was considerably improved by increasing the flow of CH₄ gas component from 0 to 40 sccm. The change of films’ hardness was discussed and attributed primarily to the internal defects and bonding characteristics, while the superior tribological properties of the films could be assigned to the formation of sp³-hybridized carbon and the C-H bonding.     

Optical, dielectric and microhardness studies on 1 0 0 directed ADP crystal

1 0 0 directed ammonium dihydrogen phosphate single crystal has been grown using the uniaxially solution-crystallization method of Sankaranarayanan–Ramasamy (SR). The size of the grown crystal is 40 mm in diameter and 50 mm in thickness. The grown crystals were characterized by UV–vis spectroscopy, Vickers hardness and dielectric studies. Comparing the 1 0 0 plane of the conventional method grown ADP crystal with 1 0 0 directed SR method grown ADP crystal, optical transparency, dielectric constant and Vickers hardness number are increased and dielectric loss is decreased in SR method grown crystal.