Optimization of Blended-Elemental Powder-Based Titanium Alloy Extrusions for Aerospace Applications

The process of canless extrusion in ambient environment, using cold isostatic pressed, and vacuum-sintered, direct-consolidated blended-elemental hydrided ADMA titanium powder, mixed with master alloy powder for the Ti-6Al-4V composition, has been successfully demonstrated. However, these initially processed unoptimized powder-based extrusions also exhibited oxygen content of about 3000 ppm, within the ASTM B817 Standard, but exceeding the AMS Specification 4935 maximum limit of 2000 ppm, and with pre-extrusion residual hydrogen within 300–500 ppm resulting in post-extrusion void nucleation aligned with the extrusion direction. Additional optimization of extrusion billets during the CIP-and-sintering steps has been successfully demonstrated reducing both oxygen and hydrogen contents to levels at or below the AMS Specification limits for Ti-6Al-4V composition (oxygen content of 2000 ppm maximum, and hydrogen content of 125 ppm maximum). Processing-microstructure-property correlations of the optimized, AMS-4935-Specification-conformant, Ti-6Al-4V blended-elemental powder-based product form exhibited an overall mechanical property balance matching that of double-arc-remelted ingot-based extrusions. Property matching was not only in terms of static mechanical properties (room-temperature tensile properties, and monotonic fracture toughness K _IC (K _Q) values), but also in terms of dynamic fatigue properties (combined S/N plus da/dN properties), as well as stress-corrosion resistance, as measured in terms of K _ISCC threshold values.     

Electrochemical synthesis of polypyrrole nanowires in the presence of gelatin

Biotemplating is an emerging, unique approach for the synthesis and organization of the organic or inorganic materials into well-defined nanostructures. In this article, conducting polymer polypyrrole (PPy) nanowires were electrochemically synthesized using a protein molecule, gelatin, as a template. The morphologies, microstructures, chemical compositions, and electrochemical performances of the obtained nanowires were investigated in detail. It was found that the gelatin played an important role in the formation of the PPy nanowires and the morphologies of the nanowires were closely related to the electrodes used. This work not only extended the application of gelatin to the synthesis of the conducting polymer nanowires, but also presented a simple and useful route to the fabrication of PPy nanowires with different length, from normal size to superlong size.     

An effective computational tool for parametric studies and identification problems in materials mechanics

Parametric studies and identification problems require to perform repeated analyses, where only a few input parameters are varied among those defining the problem of interest, often associated to complex numerical simulations. In fact, physical phenomena relevant to several practical applications involve coupled material and geometry non-linearities. In these situations, accurate but expensive computations, usually carried out by the finite element method, may be replaced by numerical procedures based on proper orthogonal decomposition combined with radial basis function interpolation. Besides drastically reducing computing times and costs, this approach is capable of retaining the essential features of the considered system responses while filtering most disturbances. These features are illustrated in this paper with specific reference to some elastic–plastic problems. The presented results can however be easily extended to other meaningful engineering situations.     

Fractal Approach to ac Impedance Spectroscopy Studies of Ceramic Materials

A novel fractal model for grain boundary regions of ceramic materials was developed. The model considers laterally inhomogeneous distribution of charge carriers in the vicinity of grain boundaries as the main cause of the non-Debye behaviour and distribution of relaxation times in ceramic materials. Considering the equivalent circuit the impedance of the grain boundary region was expressed. It was shown that the impedance of the grain boundary region has the form of the Davidson–Cole equation. The fractal dimension of the inhomogeneous distribution of charge carriers in the region close to the grain boundaries could be calculated based on the relation d _s = 1 + , where is the constant from the Davidson–Cole equation.     

Hybrid Thermoelectric–Photovoltaic Generators in Wireless Electroencephalography Diadem and Electrocardiography Shirt

Hybrid wearable energy harvesters consisting of a thermoelectric generator (TEG) and photovoltaic (PV) cells are used in this work for powering two autonomous medical devices: an electroencephalography (EEG) system and an electrocardiography (ECG) system in a shirt. Two alternative solutions for powering the systems have been implemented. In the battery-free EEG diadem, PV cells cover the outer surface of radiators used in a TEG. In the ECG shirt, thermoelectric modules are the main power supply that constantly recharges a battery, while PV cells are used mainly to provide standby power, i.e., when the shirt is not worn. Both devices are maintenance free for their entire service life.     

Assessment of process parameters on the production of diglycerides rich in omega-3 fatty acids through the enzymatic glycerolysis of fish oil

The main objective of this work is to present new experimental information concerning the effect of relevant process parameters related to the production of diglycerides by enzymatic glycerolysis of fish oil. Reaction products can be applied as ingredients in food industry, joining the emulsifying properties of partial glycerides along with the nutritional benefits attributed to the omega-3 fatty acids. From preliminary reactions, conversion was higher for a solvent- and surfactant-free system but the long time to reach appreciable amounts of diglycerides may be a drawback for practical purposes. To overcome this problem, the addition of tert-butanol revealed to be relevant, leading to high diglycerides contents in short times. The system containing Tween 65 led to the highest amount of diglycerides. This study described the feasibility of enzymatic synthesis of diglycerides rich in EPA and DHA in short reaction times as well by using a more environmentally friendly process.     

The utilisation of grapeseed oil in improving the quality of dry fermented sausages

This study aims to examine the scope of changes in colour, texture and sensory characteristics of fermented sausages by substituting 20% of backfat with grapeseed oil prepared as liquid (GS), encapsulated (EGS) and pre‐emulsified [with soy protein isolate (GSI) and alginate (GSA)], and their stability during 30 days of refrigerated storage. Protein and fat contents, pH and TBA values were not significantly different between products after production and storage. Treatments with added oil had higher weight loss (1.5–2.5%), while moisture content was significantly lowest in GS. Internal product colour evaluation showed the highest values of L*, b* and hue angle in GSI. GSI had the highest hardness and chewiness. Storage affected more surface than internal product colour, hardness was significantly changed only in GSI (lower) and EGS (higher), and increasing of TBA did not lead to significant differences between treatments. The study showed that GSA was the most promising of all treatments investigated.     

Identification and characterization of Clostridium perfringens using single target DNA microarray chip

A DNA microarray method was developed to identify the presence of toxin genes: encoding beta toxin (cpb), epsilon toxin (etx), enterotoxin (cpe), alpha toxin (cpa), and iota toxin (iA) in Clostridium perfringens. To build the DNA chip, each gene sequence was represented by one approximately 22-bp amino-modified oligonucleotide printed twice on aldehyde-coated slides. Multiplex PCR with Cy3 and Cy5-dCTP derivatized fluorescent nucleotides was used to label five genes and fluorescent probes were prepared. The PCR probes were denatured and single-strand-labeled DNAs were separated and purified using magnetic beads. The presence of toxin genes in C. perfringens was detected by hybridization of amplified ssDNA probes to oligonucleotides on the chip representing one target sequence of each toxin gene. The DNA chip was able to identify eight strains of C. perfringens.     

Distribution of iron,zinc and manganese in milling streams of common Serbian wheat cultivars: Preliminary survey

This study investigates distribution of three micronutrients in milling streams of three common wheat cultivars to estimate nutritive value of white and brown flours. Among the analysed wheat cultivars, the majority of flour streams of NS Todorka showed a higher content of soluble micronutrients than the other two investigated wheat cultivars. It is necessary to improve bioavailability of Fe and Zn in flours since these micronutrients were mostly in insoluble form. In contrast, considering average Serbian portion sizes for bread, bread made from flour Type ‘110’ could supply almost 75% of the recommended daily intake for Mn.