The corrosion behavior of TiN coated and uncoated incoloy 800 alloy

Incoloy alloy 800 is used in a variety of applications in industry as well as in domestic appliances for sheeting on electric heating elements. The composition of the alloy enables it to resist deterioration in many corrosive environments. However, resistance of the alloy to corrosion in aqueous media needs to be further examined. The present study examines the corrosion properties of Incoloy 800 alloy of both coated and uncoated workpieces obtained in a 0.1N H₂SO₄ + 0.05N NaCl solution. TiN coating is achieved using a physical vapor deposition (PVD) technique while corrosion tests are carried out using electrochemical polarization methods. Moreover, in order to examine the influence of hydrogen diffusion, reduction of hydrogen at the Incoloy 800 surface is carried out in a solution of 0.1N HNO₃ + 1 g/L thiourea. Tensile tests are conducted on the workpieces to determine the influence of hydrogen embrittlement on the resulting mechanical properties of the substrate. To examine the pit formation and stress induced microcracking, scanning electron microscope (SEM) analysis is carried out. The results show that the corrosion resistance of the alloy improves after TiN coating. In addition, no specific pattern or differentiation on the pit geometry is observed. The pitting rate and its size reduce considerably for TiN coated workpieces.     

Studies on a terephthalic acid and dihydroxydiphenyl sulfone liquid crystalline copolymer and its composites with different thermoplastics

A liquid crystalline polymer (LCP) was synthesized by an interfacial polycondensation reaction at room temperature from terephthaloyl chloride and p,p′-dihydroxydiphenyl sulfone. The LCP synthesized was so stable and molecularly rigid that it did not show any phase transition until it degraded at about 320°C. Composites of the LCP with polycarbonate (PC), polystyrene (PS), and sulfonated polystyrene (SPS) were formed by compression molding at a temperature at which the thermoplastic matrix was in the melt state. They were thermally analyzed by differential scanning calorimetry. Tensile specimens were cut from the compression-molded plates, and mechanical tests were performed. The morphology of the material systems was studied by performing scanning electron microscopy analysis on cryogenically fractured specimens. For LCP/PS and LCP/SPS systems, a sharp two-phase morphology was formed, which suggested poor interfacial adhesion. The tensile strength of both systems decreased with LCP addition. The LCP/PC system also revealed a two-phase morphology; however, the interfaces between the LCP domains and the PC matrix were not so well defined, showing better interfacial adhesion than the two previous systems studied. Stronger bonding between the LCP and PC resulted in a significant improvement in the mechanical behavior of PC by LCP addition. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 645–652, 1997     

A surface wear model for hypoid gear pairs

In this paper, a methodology was proposed for simulation of surface wear of face-milled or face-hobbed hypoid gear pairs. The methodology combines Archard's wear model with a finite-element based hypoid gear contact model. The wear model requires the sliding distances and contact pressures to be computed along the contact zones at each rotational gear position. Formulations were proposed for computation of sliding distance along the tooth contact zones based on hypoid gear kinematics and geometry of the tooth surfaces, and the contact model was used to predict the normal contact pressure distributions. An example hypoid gear pair was analyzed for its wear behavior. Influences of gear position errors on wear patterns were demonstrated. An approximate method that is computationally more efficient was also proposed at the end.     

Carbon nanotube-DNA nanoarchitectures and electronic functionality

Biological molecules such as deoxyribonucleic acid (DNA) possess inherent recognition and self-assembly capabilities, and are attractive templates for constructing functional hierarchical material structures as building blocks for nanoelectronics. Here we report the assembly and electronic functionality of nanoarchitectures based on conjugates of single-walled carbon nanotubes (SWNTs) functionalized with carboxylic groups and single-stranded DNA (ssDNA) sequences possessing terminal amino groups on both ends, hybridized together through amide linkages by adopting a straightforward synthetic route. Morphological and chemical-functional characterization of the nanoarchitectures are investigated using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Electrical measurements (I-V characterization) of the nanoarchitectures demonstrate negative differential resistance in the presence of SWNT/ssDNA interfaces, which indicates a biomimetic route to fabricating resonant tunneling diodes. I-V characterization on platinum-metallized SWNT-ssDNA nanoarchitectures via salt reduction indicates modulation of their electrical properties, with effects ranging from those of a resonant tunneling diode to a resistor, depending on the amount of metallization. Electron transport through the nanoarchitectures has been analyzed by density functional theory calculations. Our studies illustrate the great promise of biomimetic assembly of functional nanosystems based on biotemplated materials and present new avenues toward exciting future opportunities in nanoelectronics and nanobiotechnology.     

Supercapacitors based on pillared graphene nanostructures

We describe the fabrication of highly conductive and large-area three dimensional pillared graphene nanostructure (PGN) films from assembly of vertically aligned CNT pillars on flexible copper foils for applications in electric double layer capacitors (EDLC). The PGN films synthesized via a one-step chemical vapor deposition process on flexible copper foils exhibit high conductivity with sheet resistance as low as 1.6 ohms per square and possessing high mechanical flexibility. Raman spectroscopy indicates the presence of multi walled carbon nanotubes (MWCNT) and their morphology can be controlled by the growth conditions. It was discovered that nitric acid treatment can significantly increase the specific capacitance of the devices. EDLC devices based on PGN electrodes (surface area of 565 m2/g) demonstrate enhanced performance with specific capacitance value as high as 330 F/g extracted from the current density-voltage (CV) measurements and energy density value of 45.8 Wh/kg. The hybrid graphene-CNT nanostructures are attractive for applications including supercapacitors, fuel cells and batteries.     

Identification of phenolic profiles,fatty acid compositions,antioxidant activities,and enzyme inhibition effects of seven wheat cultivars grown in Turkey: A phytochemical approach for their nutritional value

In the present article, seven wheat cultivars (Ahmetaga, Bezostaya, Dagdas-94, Ekiz, Karahan-99, Konya-2002, and Tosunbey) grown in Turkey were compared for their phytochemical composition, antioxidant, and enzyme inhibitory activities. Antioxidant capacities and enzyme inhibitory effects were investigated with colorimetric methods. Total phenolic content ranged from 40.71 to 86.34 mg of gallic acid equivalent/100 g wheat grain. Tosunbey (92 mg Trolox equivalent/100 g wheat grain) and Ahmetaga (114.56 mg Trolox equivalent/100 g wheat grain) cultivars exhibited strong 2,2 azino-bis (3-ethylbenzothiazloine-6-sulfonic acid) and 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activities. As compared to other wheat cultivars, Tosunbey cultivar had remarkable both antioxidant and enzyme inhibitory effects with the highest level of phenolics. Ferulic acid, chlorogenic acid, and apigenin were the major phenolics in extracts tested. This study suggested that an increased intake of wheat derived products could represent an effective strategy for the management of oxidative stress related chronic and degenerative diseases such as Alzheimers and diabetes mellitus.     

Investigation of the Microstructural,Mechanical and Corrosion Properties of Grade A Ship Steel-Duplex Stainless Steel Composites Produced <Emphasis Type="Italic">via</Emphasis> Explosive Welding

Grade A ship-building steel-AISI 2304 duplex stainless steel composite plates were manufactured via explosive welding. The AISI 2304 plates were used to clad the Grade A plates. Optical microscopy studies were conducted on the joining interface for characterization of the manufactured composite plates. Notch impact, tensile-shear, microhardness, bending and twisting tests were carried out to determine the mechanical properties of the composites. In addition, the surfaces of fractured samples were examined by scanning electron microscopy (SEM), and neutral salt spray (NSS) and potentiodynamic polarization tests were performed to examine corrosion behavior. Near the explosion zone, the interface was completely flat, but became wavy as the distance from the explosion zone increased. The notch impact tests indicated that the impact strength of the composites decreased with increasing distance from the explosion zone. The SEM studies detected brittle behavior below the impact transition temperature and ductile behavior above this temperature. Microhardness tests revealed that the hardness values increased with increasing distance from the explosion zone and mechanical tests showed that no visible cracking or separation had occurred on the joining interface. The NSS and potentiodynamic polarization tests determined that the AISI 2304 exhibited higher corrosion resistance than the Grade A steel.     

Analysis of quantum noise in a singly resonant nondegenerate optical parametric oscillator

We have analyzed the evolution of quantum operators in a three-wave mixing process by using the nonlinear polarization driven wave equations and linearization of the quantum operators. We have theoretically shown that a nondegenerate optical parametric amplifier can generate amplitude-squeezed light when operated in the backconversion regime. Furthermore, a nondegenerate optical parametric oscillator, where only the signal wave is resonant, is proved to generate amplitude-squeezed light when the pump intensity is above the value at which 100% photon conversion efficiency is achieved. The calculated limit for amplitude-squeezing in this case is 3 d B.     

Capacitated lot sizing with alternative routings and overtime decisions

Material requirements planning (MRP) is a basic tool for performing detailed material planning function in the manufacture of component parts and their assembly into finished items. MRP's managerial objective is to provide ‘the right part at the right time’ to meet the schedules for completed products. However satisfying end customer demands faster with lower inventories implies smarter scheduling which must simultaneously reflect actual capacity conditions. Therefore, the need is to schedule both capacity and materials simultaneously. Since MRP does not consider the availability of capacity resources to schedule production, consequently the schedules so developed are usually capacity infeasible. This paper proposes a three-step procedure to develop capacity feasible material and production schedules in a finite capacity environment. In the first step, an LP model produces capacity feasible but lot size relaxed planned order releases for all end products and assembly components which are then fed into a MRP processor, where a bill of material (BOM) explosion process generates material plans. Finally, these material plans are introduced to another LP model which assures that capacity feasibility is again restored. The mathematical models developed consider restrictions on lot sizes as well as alternative production routings and overtime decisions. A numerical example also is provided and some future research directions are outlined.