Effect of Surfactant Stabilizers on the Distribution of Carbon Nanotubes in Aqueous Media

The results of a study on the homogeneity of suspensions are described considering the effect of different types of surfactant stabilizers and their concentrations on the uniform distribution of a carbon nanotubes (CNTs)-based modifying additive to construction materials in an aqueous medium. This problem was solved herein by using surfactants and ultrasound. The sonication treatment of CNTs particle agglomerates allowed for dispersing their globules and achieving a 15-20-fold decrease in their average size, for which it became possible to make better use of the CNTs as cement modifier. As a result of the experimental studies carried out, the effect of the surfactant type and concentration promoting uniform distribution of the CNTs in the bulk of the suspension and, correspondingly, in the structural composite matrix was revealed. The CNTs-based additive improved the physical-mechanical and operational characteristics of the material.     

Nano-scale multi-layered coatings for improved efficiency of ceramic cutting tools

Electron beam welding, though considered a sophisticated welding process, still requires the operator to first carry out several trial welds to find the right combination of welding parameters based on intuition and experience. This archaic method is often unreliable, leading to unproductive manufacturing lead time, man hours, quality control tests, and material wastage. The current study eliminates this “trial and error” method by providing a reliable model which can predict the right combination of weld parameters to achieve a high-quality weld. Beads on plate welds were carried out on AISI 304 stainless steel plates using a low-kilovolt electron beam welding (EBW) machine. A model that can predict weld bead geometry and provide optimized output for minimum weld area condition without compromising on weld quality was developed. Experimental data were collected as per full factorial design of experiments, and the levels for each input parameter were established through pilot experiments. A multivariate regression analysis has been conducted to establish a relationship between four weld input parameters (three levels each) and four weld bead responses. Response surface methodology (RSM) has been used to study the interrelationship between input parameters and their effect on each response variable. Further, minimization of weld cross-sectional area was done using genetic algorithm for maximum penetration and minimum weld area condition. The optimized mathematical model convincingly establishes that the focusing current is a significant input parameter with very high influence over the weld bead geometry. Extensive material characterization and mechanical tests have been carried out to validate the regressed input-output relationship and the optimized mathematical model.     

Mixed signal SIMD processor array vision chip for real-time image processing

A prototype vision chip has been designed that incorporates a 20 × 64 array of processing elements on a 31 μm pitch. Each processor element includes 14 bits of digital memory in addition to seven analogue registers. Digital operands include NOR and NOT with operations of diffusion, subtraction, inversion and squaring available in the analogue domain. The cells of the array can be configured as an asynchronous propagation network allowing operations such as flood filling to occur with times of ~1 μs across the array. Exploiting this feature allows the chip to recognise the difference between closed and open shapes at 30,000 frames per second. The chip is fabricated in 0.18 μm CMOS technology.     

A Study on the Action of Ozone and on the Thermal Stability of Nanodiamond

Ultradisperse detonation diamond (UDD), a nanodiamond having particle size around 4 nm has been treated with ozone in an aqueous slurry. The reaction kinetics appeared to be relatively slow and long ozonation times were needed in order to functionalize the surface of a special nanodiamond sample with a very low degree of oxidation and foreign groups. The resulting ozonated nanodiamond has been studied by FT-IR and electronic spectroscopy. It has been shown that the ozonation of cyclohexane and adamantane can be taken as a model reaction for the ozonation of diamond. Together with ketonic groups of various nature formed on the surface of nanodiamond, the ozonation leads also to the formation of simple molecules like for instance HCOOH and HCHO which remain in the water solution and which have been detected by HPLC analysis using a diode-array detector. The thermal stability of the nanodiamond sample has been studied by thermogravimetric analysis (TGA-DTG) combined with differential thermal analysis (DTA) both under inert atmosphere and in air flow. The studies on thermal stability have been conducted in comparison to a sample of bulk diamond. It appears that the behavior of nanodiamond is completely different than the bulk diamond sample. For instance, under inert atmosphere and at 900°C the weight loss undergone by the nanodiamond is 11.5% while it is negligible in the case of bulk diamond under the same conditions. Similarly, in air flow the nanodiamond burns abruptly above 450°C while bulk diamond starts to burn only above 850°C. These differences have been explained in terms of different particle size and surface functionalization.     

NUMERICAL SIMULATION OF OPEN WAVEGUIDE CONVERTERS USING FDTD METHOD

We study 3-dimensional asymmetric diffraction problems for waveguide-based electro-dynamic systems, radiating to infinite free space. For calculations we utilize the FDTD (Finite Difference Time Domain) numerical simulation method with the UPML (Unsplit Perfectly Matched Layer) absorbing boundary conditions. This paper states that the FDTD method, in spite of its relatively low calculation speed, has an approved ability of solving certain problems that cannot be solved by the other traditional numerical simulation methods (the method of integral equation, the method of scattering matrix).     

Complexation of macroporous amphoteric cryogels based on N,N‐dimethylaminoethyl methacrylate and methacrylic acid with dyes,surfactant, and protein

Macroporous amphoteric cryogels based on N,N‐dimethylaminoethylmethacrylate and methacrylic acid p(DMAEM‐co‐MAA) crosslinked by N,N′‐methylenebisacrylamide (MBAA) were synthesized by radical copolymerization of monomer mixtures in cryoconditions. The structure and morphology of cryogels were evaluated by FTIR and SEM. Cryogels exhibited interconnected porous structure with pore size ranging from 40 to 80 µm, which depended on their crosslinking degree. The value of the isoelectric point (IEP) of equimolar amphoteric cryogel determined from the water flux was equal to 4.4, while the IEP of cryogel with the excess of DMAEM units was equal to 7.1. The mechanical strength of equimolar amphoteric cryogels increases with increasing amount of crosslinking agent. The complexation ability of amphoteric cryogels with respect to surfactant, dyes, and protein was demonstrated. The adsorption isotherms with respect to anionic surfactant—sodium dodecylbenzene sulfonate (SDBS) and protein—lysozyme correspond to Langmuir equation, while adsorption isotherms of anionic and cationic dyes—methylene blue (MB) and methyl orange (MO) are well described by Freundlich equation. It was found that the binding ability of p(DMAEM‐co‐MAA) with respect to various low‐ and high‐molecular weight compounds changes in the following order: SDBS > lysozyme ? MO > MB. The preferential adsorption of MB from the mixture of protein and MB was shown. The quantitative release of protein, surfactant and dye molecules from the matrix of cryogels takes place at the IEP of cryogel. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43784.     

Influence of metal powder particle's shape on the kinetics of hydriding

The aim of this paper is to study the influence of the metal powder particle's shape on the kinetics of isothermal hydriding under constant pressure. We present arguments that this influence is small and may be neglected. The mathematical model of hydriding is described and applied to two series of experimental curves (for uranium and magnesium) for three convenient symmetrical model shapes: sphere, long thin cylinder, and flat thin plate. The fitting shows that quality of the approximation of the experimental curves by the model ones is comparable for these three shapes (yet spheres and cylinders provide better results compared to a plate) for similar kinetic parameters. The reasons for the shape-independent behaviour are discussed using some theoretical arguments based on the suggested model.     

The formation of a peroxoantimonate thin film coating on graphene oxide (GO) and the influence of the GO on its transformation to antimony oxides and elemental antimony

The ultrathin peroxoantimonate coating of graphene oxide from hydrogen peroxide-rich solutions of hydroxoantimonate is demonstrated. An amorphous 1–2 nm Sb (V) oxide film is formed and can be further crystallized by exposure to an electron beam to give a 2–5 nm thick supported Sb₆O₁₃ particulate coating. Heat treatment of the peroxoantimonate yielded different crystalline oxides, whereas in the presence of the graphene support only trigonal Sb (0) was produced by heat treatment in vacuum or an argon atmosphere. The graphene oxide support is essential for the formation of the Sb (0) phase and even in air a substantial elemental antimony was obtained. Whereas heat treatment of uncoated graphene oxide in an inert atmosphere produces reduced graphene oxide, the antimony oxide coated graphene oxide is not reduced by the heat treatment. Only after the supported antimony oxide is reduced to give the trigonal Sb (0) phase the graphene oxide was reduced by the heat treatment. The phases before and after the different heat treatments are characterized by electron and X-ray diffraction, thermal analysis, XPS studies, electron microscopy and wet chemistry.