Studies on the Pitting Corrosion of the Delta-52 Steel in aqueous solutions. 2. Variation of the pitting potential in relation to the concentration of the aggressive anion

Potentiodynamic anodic polarization curves have been traced for an electrode of the steel Delta-52 (0.40, 0.78Mn, 0.045 S, 0.06P, 0.23 Si): the aggresive media used were potassium hydroxide without and with additions of potassium chloride, bromide and iodide. The oxide film present on the steel surface does not inhibit active dissolution; only at potentials exceeding+2 (S. C. E.) passivity sets in. The polarization behaviour of the steel is not influenced by the addition of the halide salts; above a certain salt concentration, however, there is a sharp increase in dissolution current. This phenomenon is an indication of the start of pitting. Between the pitting potential and the anion concentration there exists a well defined relation.     

Copolyamides of caprolactam and m-xylylenediammonium isophthalate

Caprolactam was copolymerized with m-xylylenediammonium isophthalate (MXD-I) to form a series of partially aromatic, thermoplastic copolyamides. The MXD-I mole-% in these systems varied between 91% and 31%. Using differential scanning calorimetry (DSC), the glass transition temperature of these copolyamides was shown to decrease with decrease in their aromatic content. The T_g of a typical copolyamide with an MXD-I mole fraction of 0.34 is about 50°C higher than that of nylon 6. The DSC thermograms of MXD-I homopolymer and all the reported copolymers revealed no distinct melting endotherms or crystallization exotherms, and these polymers were considered to be essentially amorphous. Most of these copolyamides were shown by thermogravimetric analysis to be more thermally stable than nylon 6. Compression-molded films of several copolymers were prepared and were shown to be less hydrophilic than nylon 6, regardless of their suggested amorphous nature. Tensile properties of several copolyamides were measured and were shown to depend on their MDX-I content, degree of polymerization, and chain sequential arrangement. A few of the reported copolyamides exhibited some unusual solution, thermal, and tensile properties. This was ascribed to the presence of block structures and/or branching in these systems.     

The coefficient of performance for a solar absorption dual cycle

The traditional definition of the coefficient of performance (COP) can create misleading results because this definition does not define the heat input base to be used for estimating the COP. Furthermore, such one-dimensional definitions do not consider other important factors which may affect the system selection.

A new selection criterion for a solar powered dual absorption system will be presented in this paper. The dual cycle, which has the advantage of not using a cooling tower, has often been ignored because of the misleading definition of the COP.

The present paper also describes a lithium bromide dual absorption cycle.     

Dyeing properties of poly(methyl vinyl pyridine)-poly(ethylene terephthalate) graft copolymers

Grafting of poly(ethylene terephthalate) fibers (PET) with 2-methyl-5-vinylpyridine (MVP) was carried out using γ rays and benzoyl peroxide independently for the initiation of grafting. The poly(MVP)-PET graft copolymers were analyzed for density, moisture regain, and dyeability. Radiation-induced grafting yielded copolymers with densities and moisture regain appreciably higher than those produced by benzoyl peroxide. The same results occurred when acid dyes were used. The behavior of (MVP)-PET graft copolymers towards some reactive dyes was also studied. The extent and rate of dyeing were dependent of pH of the dye bath, nature of the dye and the magnitude of grafting. Dyeing occurs through formation of salt linkages between the pyridine moieties and the solubilizing groups (usually sulfonate groups) in the dye molecule.     

A solar-powered LiBr dual cycle

The absorption system is one of the most suitable techniques for utilising solar energy for air-conditioning purposes. Although it uses solar energy directly with minimum conversion, it consumes considerable quantities of water for the cooling tower. This is a serious disadvantage where solar energy is available whilst water is scarce.The main purpose of this paper is to introduce the lithium bromide (LiBr) absorption cycle which avoids the use of a wet cooling tower. The characteristics of this dual cycle will be examined and new selection criteria for such solar-powered dual absorption systems will be introduced.     

Very high-speed and high-accuracy current-steering CMOS D/A converter using a novel 3-D decoder

In this paper a 10-bit 1.2-GSample/s Nyquist current-steering CMOS digital-to-analog converter (DAC) is presented. Segmentation (90%) has been used to get the best DNL and reduce glitch energy. This segmentation ratio guarantees the monotonicity. Higher performance is achieved using a novel 3-D thermometer decoding method which reduces the area, power consumption, and the number of control signals of the digital section. Simulation results show that the spurious-free-dynamic-range (SFDR) in Nyquist rate is better than 65 dB for sampling frequency up to 1.2-GSample/s. The analog voltage supply is 3.3 V while the digital part of the chip operates at only 2.4 V. Total power consumption in Nyquist rate measurement is 149 mW. The chip has been processed in a standard 0.35 μm CMOS technology. Active area of chip is 1.97 mm².     

Transport properties study of supplementary cementitious materials: case of tuff,limestone filler and granodiorite

The aim of this research is to determine the effects of replacing cement with tuffs on the transport properties and service life of cement-based materials. Specimens were prepared replacing 5% and 15% by weight of cement with both white and brown tuffs. Additional specimens were prepared replacing cement with 5% and 15% limestone filler and granodiorite to compare the effects of these types of materials. For these four types of specimen as well as a control mortar with no cement replacement transport properties (gas permeability and chloride ingress) were measured as well as porosity and pore diameter. The transport properties were compared the changes in these porosity and pore diameter. Based on the results, white tuff significantly improves the transport properties of the mortars due to its pozzolanic reaction and that white tuff may be an economically and functionally viable replacement for cement where concrete durability is important. Pore diameter and porosity did not correlate well with transport properties.     

Wear and Tribological Performance of Different Ceramic Tools in Dry High Speed Machining of Ni-Co-Cr Precipitation Hardenable Aerospace Superalloy

Tool wear is an important machinability criterion. To reduce total machining costs, this study demonstrates the wear and tribological performance of four ceramic tools in dry high-speed turning of Ni-Co-Cr precipitation hardenable superalloy (Inconel 100). Wear of the tool materials and the structural and phase transformations at the tool–chip interface were investigated. Results obtained reveal that SiAlON ceramic outperformed other ceramic tool materials at different cutting speeds due to the formation of a large amount of mullite tribofilms on the tool face, which serve as a thermal barrier layer. Alumina ceramic with the addition of ZrO₂ can be recommended for machining Inconel 100 at speeds above 150 m/min due to its ability to form thermal barrier ZrO₂ tribofilms, which decrease the coefficient of friction at the tool–chip interface. Mixed alumina and an alumina matrix reinforced with SiC_w were found to be unsuitable for machining age-hardened Inconel 100 superalloy.     

Structural,magnetic, and optical properties of nano-sized Ni0.85Se

Nanocrystalline Ni_0.85Se was synthesized by a hydrothermal method. X-ray diffraction analysis by Rietveld method indicated that Ni_0.85Se has a NiAs-type hexagonal structure. Narrow crystallite size distribution with an average area-weighted size of 〈ɛ_F〉 = 8.5 nm is obtained by Warren-Averbach method. Structural analysis revealed deformed Se atoms octahedron with the shortest distance between Se atoms in adjacent planes 〈Se–Se〉_adj smaller than between nearest neighbors in layer plane 〈Se–Se〉_nea, and a rather short interatomic distance between the transition metal atoms 〈Ni–Ni〉. The optical property of Ni_0.85Se was studied by UV-spectroscopy. Magnetic measurement shows a ferromagnetic phase transition for Ni_0.85Se below 14 K.