MOCVD and MOALD of nanostructured cemented Carbides, oxide semiconductors, II-VI and III-V semiconductors

This paper analyzes the microstructure evolution and its influence on tribological performance of WC-Co cemented carbide, with surface modified by a thermochemical borated treatment. This surface modification was implemented by the method of boronizing through solid powders. Microstructural and tribological characterization was done by inspection of the boronized layer, and the determination of the surface
microhardness and wear resistance were determined in boronized and non-boronized samples. The wear tests were performed according to “block on ring” configuration, using AISI E52100 steel as
counterpart. The results allowed for evaluation of the influence of microstructure on the treated area
and on the surface properties in terms of micro-hardness and wastage resistance. The boronized surface
presents an improvement of the tribomechanical properties, being more evident in the softer parts. Finally,
the correlation between wastage rate and microstructural parameters was analyzed; attempting to identify
the optimum microstructure for the application of boronized surface regarding to wear resistance

The application of chamfered tools in metal cutting is yet very much limited. Despite their better edge strength, relatively little research have been done so far to understand the effect of tool geometry on cutting variables and the mechanics of chip formation. The present study focuses on the performance of chamfered tools during continuous and interrupted turning of medium carbon low alloy steel. Several cutting tests were conducted in turning on a conventional lathe machine with cemented carbide chamfered solid tools and its performance with respect to cutting force, tool life and chip formation have been investigated. The tools were ground to different chamfer widths varying from 0.10 to 0.40 mm at a constant chamfer angle of 45° and to a varying main cutting edge chamfer angles ranging from 15° to 35° at a constant chamfer width of 0.20 mm. For the purpose of interrupted turning, four axial slots were milled on the cylindrical work material. It has been observed that both in continuous and interrupted turning, with the increase chamfer width, both the main cutting force and feed forces increases and the effect on the feed force is more significant. With the increase of chamfer angle, cutting forces increased but at the maximum chamfer angle, both main cutting force and feed force were low. The chip thickness was observed to decrease with increasing chamfer width. However the effect of chamfer angle on the chip thickness was insignificant. Shear angle increased with the increase of both width and angle of the chamfer. © 2005 Elsevier B.V. All rights reserved.

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http://www.sciencedirect.com/science/article/pii/S0924013605005285

Highly relaxed GaN nanodots and submicron ridges have been selectively grown in the NSAG regime using MOVPE on lattice mismatched 6H–SiC and AlN substrates. 2D real space and 3D reciprocal space mapping was performed with a CCD detector using 10.4 keV synchrotron X-ray radiation at the 2-ID-D micro-diffraction beamline at Advanced Photon Source (APS). Calibration procedures have been developed to overcome the unique challenges of analyzing NSAG structures grown on highly mismatched sub-strates. We studied crystallographic planar bending on the submicron scale and found its correlation with strain relaxation in the NSAG ridges.

One of the central challenges of nanoscience is fabrication of nanoscale structures with well-controlled architectures using planar thin-film technology. Herein, we report that ordered nanocheckerboards in ZnMnGaO 4 films were grown epitaxially on single-crystal MgO substrates by utilizing a solid-state method of the phase separation-induced self-assembly. The films consist of two types of chemically distinct and regularly spaced nanorods with mutually coherent interfaces, ∼4 × 4 × 750 nm 3 in size and perfectly aligned along the film growth direction. Surprisingly, a significant in-plane strain, more than 2%, from the substrate is globally maintained over the entire film thickness of about 820 nm. The strain energy from Jahn−Teller distortions and the film−substrate lattice mismatch induce the coherent three-dimensional (3D) self-assembled nanostructure, relieving the volume strain energy while suppressing the formation of dislocations.

The industrial demand for automated machining systems to enhance process productivity and quality in machining aerospace components requires investigation of tool condition monitoring. The formation of chip and its removal have a remarkable effect on the state of the cutting tool during turning. This work presents a new technique using acoustic emission (AE) to monitor the tool condition by separating the chip formation frequencies from the rest of the signal which comes mostly from tool wear and plastic deformation of the work material. A dummy tool holder and sensor setup have been designed and integrated with the conventional tool holder system to capture the time-domain chip formation signals independently during turning. Several dry turning tests have been conducted at the speed ranging from 120 to 180 m/min, feed rate from 0.20 to 0.50 mm/rev, and depth of cut from 1 to 1.5 mm. The tool insert used was TiN-coated carbide while the work material was high-carbon steel. The signals from the dummy setup clearly differ from the AE signals of the conventional setup. It has been observed that time-domain signal and corresponding frequency response can predict the tool conditions. The rate of tool wear was found to decrease with chip breakage even at higher feed rate. The tool wear and plastic deformation were viewed to decrease with the increased radius of chip curvature and thinner chip thickness even at the highest cutting speed, and these have been verified by measuring tool wear. The chip formation frequency has been found to be within 97.7 to 640 kHz. © Springer-Verlag London Limited 2011.

http://link.springer.com/article/10.1007/s00170-011-3722-7