Effect of metal catalyst thermal expansion on thermal stability of synthetic diamonds

Thermal stability of synthetic diamonds grown in various metallic solutions in terms of their residual strength after thermal loading is studied. The micromechanical, cohesive zone model of crack initiation and propagation in the diamond crystal in a vicinity of metal inclusion has been developed. The inclusion-diamond thermal expansion mismatch is found to be a key factor responsible for the strength reduction of diamond crystals after high-temperature treatment. The results of computer simulation satisfactory correlate with the available experimental data.     

Morphology, optical, and photoelectrochemical properties of electrodeposited nanocrystalline ZnO films sensitized with Cd x Zn1−x S nanoparticles

Nanocrystalline ITO/ZnO films formed by porous zinc oxide microplatelets 1–3 μm in size and 100–200 nm in thickness, which consist of 30–50 nm ZnO crystallites, were sensitized to visible light by Cd _x Zn_1?x S nanocrystals deposited using the method of successive ionic layer adsorption and reaction (SILAR). The composition of Cd _x Zn_1?x S nanocrystals as well as the dependence between molar Cd(II) fraction in the films and the ratio of cadmium and zinc nitrate concentrations in solutions used for the SILAR procedure were determined by a combination of electron, Raman, and energy-dispersive X-ray spectroscopies. The photovoltage observed at illumination of the ITO/ZnO/Cd _x Zn_1?x S heterostructures by white light (λ >400 nm) in aqueous Na₂S solution increases with a decrease of Cd(II) content proportionally to an increment in the conduction band potential of the Cd _x Zn_1?x S nanocrystals. The photocurrent density normalized to the light absorbance of the ITO/ZnO/Cd _x Zn_1?x S films increases by a factor of around four when the conduction band potential of Cd _x Zn_1?x S nanocrystals grows by 220 mV as a result of Cd(II) fraction changing from 1.0 to 0.62–0.67. The results show that Cd _x Zn_1?x S solid solutions are more advantageous sensitizers for the short-wavelength part of the sensitivity window of the liquid-junction solar cells (400–450 nm) than conventionally used cadmium sulfide.     

Study of surface quality in high speed turning of Inconel 718 with uncoated and coated CBN tools

Inconel 718 is known to be among the most difficult-to-machine materials due to its special properties which cause the short tool life and severe surface damages. The properties, which are responsible for poor machinability, include rapid work hardening during machining; tendency to weld with the tool material at high temperature generated during machining; the tendency to form a built-up edge during machining; and the presence of hard carbides, such as titanium carbide and niobium carbide, in their microstructure. Conventional method of machining Inconel 718 with cemented carbide tool restricts the cutting speed to a maximum 30?m/min due to the lower hot hardness of carbide tool, high temperature strength and low thermal conductivity of Inconel 718. The introduction of new coated carbide tools has increased cutting speed to 100?m/min; nevertheless, the time required to machine this alloy is still considerably high. High speed machining using advanced tool material, such as CBN, is one possible alternative for improving the productivity of this material due to its higher hot hardness in comparison with carbide tool. This paper specifically deals with surface quality generated under high speed finishing turning conditions on age-hardened Inconel 718 with focus on surface roughness, metallographic analysis of surface layer and surface damages produced by machining. Both coated and uncoated CBN tools were used in the tests, and a comparison between surfaces generated by both tools was also discussed.     

Development of Resource-Saving Technology of Linseed Harvesting

ABSTRACT

The traditional technology of linseed harvesting involves the cutting of the stems with subsequent threshing. During cutting part of the stem remains on the field, which causes significant losses of fibrous raw materials. Threshing of stems by traditional technology also causes significant damage to the linseed straw. Developed resource-saving technology of linseed harvesting provides first linseed thrashing on the plants with subsequent pulling of stems. With this sequence of technological operations, all linseed stems and seeds are preserved without damage. For the implementation of resource-saving technology proposed design of flax thresher and flax puller. The results of experimental studies of the properties of linseed fibre obtained from the linseed showed that such fibre is suitable for the production of non-woven materials, technical textiles and paper. The introduction of resource-saving technology of linseed harvesting will save the harvest of seeds and straw with minimal losses and damage. Resource-saving technology will increase the profitability of linseed cultivation.     

Deposition of BaTiO3 Films from EthanoI-PVB Medium

EPD （electrophoretic deposition） of barium titanate from organic medium ethanol-PVB （polyvinyl butyral） was performed on Ni, Ti, steel substrate. Stable BaTiO3 suspensions with concentration of 2 wt.% have been prepared for the deposition. A uniform and dense layer was obtained for films deposited from ethanol with PVB of 0.1%. The surface topology of deposited films can be controlled via the applied voltage. This method allows to obtain crack-free and smooth layers BaTiO3 from organic medium with thickness of 4-20 μm.     

A novel copolymer of N-[(tert-butylperoxy)methyl]acrylamide and maleic anhydride for use as a reactive surfactant in emulsion polymerization

A new copolymer of N-[(tert-butylperoxy)methyl]acrylamide (tBPMAAm), containing a primary–tertiary peroxide group and maleic anhydride (MA), was synthesized and employed as a reactive surfactant (inisurf) for the emulsion polymerization of styrene to yield surface-functionalized (peroxidized) reactive latex particles. The copolymerization characteristics were analyzed to determine the monomer reactivity ratios and to provide a way to control the copolymer composition. The ability of tBPMAAm–MA to act as a reactive surfactant during emulsion polymerization was confirmed by the synthesis of monodisperse polystyrene latexes of varying particle size. In addition, peroxide groups were localized on the surface of the particles in a controllable amount (depending on the copolymer concentration), thus, providing the opportunity for further modification of the surface of the particles. This novel copolymer is expected to be a promising and efficient material in the synthesis of functional polymer nanoparticles with well-defined core–shell morphologies.     

Removing the outliers in root-MUSIC via pseudo-noise resampling and conventional beamformer

A joint use of pseudo-noise resampling technique and a conventional beamformer is proposed to mitigate the effect of outliers in Root-MUSIC estimator. After resampling of Root-MUSIC via pseudo-randomly generated noise we combine it with a conventional beamformer (in the sense that identification of the signal roots is based on the power of the conventional beamformer response). The resulting estimator can be referred to as modified resampled Root-MUSIC. The estimator bank is formed from a number of modified resampled Root-MUSIC. Censored selection of the results of modified pseudo-randomly resampled Root-MUSIC estimators is exploited based on an appropriate local performance test.     

Variational generation of prismatic boundary‐layer meshes for biomedical computing

Boundary‐layer meshes are important for numerical simulations in computational fluid dynamics, including computational biofluid dynamics of air flow in lungs and blood flow in hearts. Generating boundary‐layer meshes is challenging for complex biological geometries. In this paper, we propose a novel technique for generating prismatic boundary‐layer meshes for such complex geometries. Our method computes a feature size of the geometry, adapts the surface mesh based on the feature size, and then generates the prismatic layers by propagating the triangulated surface using the face‐offsetting method. We derive a new variational method to optimize the prismatic layers to improve the triangle shapes and edge orthogonality of the prismatic elements and also introduce simple and effective measures to guarantee the validity of the mesh. Coupled with a high‐quality tetrahedral mesh generator for the interior of the domain, our method generates high‐quality hybrid meshes for accurate and efficient numerical simulations. We present comparative study to demonstrate the robustness and quality of our method for complex biomedical geometries. Copyright © 2009 John Wiley & Sons, Ltd.     

3D-printed polymer packing structures: Uniformity of morphology and mechanical properties via microprocessing conditions

Three-dimensional (3D) printing is an attractive approach to fabricate highly porous extremely lightweight structures for architecture antivibrational packaging. We report 3D printing processing of model packaging structures using biodegradable poly(lactic acid) (PLA) as a source material, with acrylonitrile butadiene styrene (ABS) utilized as a common 3D printing source material as a traditional benchmarked material. The effects of printing temperature, speed, and layer morphology on the layer-by-layer 3D-printed structures and their mechanical properties were considered. Three different characteristic morphologies were identified based on printing temperature; the microscopic surface roughness was dependent on the printing speed and layer height. We demonstrate that the mechanical performances and surface properties of 3D-printed PLA structures could be improved by optimization of printing conditions. Specifically, we evaluate that these PLA-based 3D structures printed exhibited better surface qualities and enhanced mechanical performance than traditional ABS-based structures. Results showed that the PLA-based 3D structures possessed the favorable mechanical performance with 34% higher Young's modulus and 23% higher tensile strength in comparison to the ABS-based 3D structures. This study provides guidelines for achieving high-quality 3D-printed lightweight structures, including smooth surfaces and durable mechanical properties, and serves as a framework to create biodegradable 3D-printed parts for human use.     

Thermo-sensitive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) microgels: 1—synthesis and characterization

In the present paper, polymeric microgels have been prepared by surfactant-free emulsion co-polymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with water-soluble azo-initiator 2,2′-azobis(2-methylpropioamidine) dihydrochloride (AMPA). It was found that the particle diameter decreased gradually when higher amounts of AAEM were used in monomer mixture. Obtained microgels possess lower critical solution temperature (LCST) in water solutions, so rapid decrease of the particle size was observed at elevated temperatures. As was found using simultaneous static and dynamic light scattering, microgels undergo soft sphere–hard sphere transition during heating.