Autoxidation of the furan fatty acid ester, methyl 9,12-epoxyoctadeca-9,11-dienoate

The objective of this study was to identify autoxidation products of methyl 9,12-epoxyoctadeca-9,11-dienoate (F_9,12). Previous work has shown that F_9,12 is a product both of autoxidation and singlet oxygen oxidation of the methyl ester derivative of conjugated linoleic acid (CLA). F_9,12, 95% pure, was synthesized from methyl ricinoleate. The synthetic F_9,12 was heated at 50°C in sealed tubes containing air. Each tube contained 6 mg F_9,12 and 1 mg methyl stearate as an internal standard. Samples were taken at 4.5, 7, 23, 46.5, 69.5, and 93 h. The oxidized F_9,12 was dissolved in isooctane and analyzed by gas chromatography (GC), GC-direct deposition-Fourier transform infrared spectroscopy, and GC-electron ionization mass spectrometry. CLA methyl ester was oxidized in a similar manner. Under these conditions, the half-lives of CLA and F_9,12 were 40 and 35 h, respectively. Oxidation products of F_9,12 that were identified included: 5-hexyl-2-furaldehyde (I), methyl 8-oxooctanoate (II), methyl 13-oxo-9,12-epoxytrideca-9,11-dienoate (III), methyl 8-oxo-9,12-epoxy-9,11-octadecadienoate (IV), and methyl 13-oxo-9,12-epoxy-9,11-octadecadienoate (V).     

NH4+ directed assembly of zinc oxide micro-tubes from nanoflakes

A simple precipitation process followed with the heat treatment was developed to synthesize ZnO micro-tubes by self-assembly of nanoflakes composed of nanoparticles. The resulting ZnO micro-tubes demonstrated excellent photocatalytic performance in degrading methylene blue (MB) under UV illumination. It was found that NH₄⁺ ion played a critical role in directing the assembly of the nanoflakes to form the micro-tube structure. A critical reaction ratio existed at or above which the ZnO micro-tubes could be obtained. For the mixtures of solutions of (NH₄)₂CO₃ and zinc salt, the ratio () was 2:1.     

Rapid prototyping technique for ceramic mini-devices containing internal channels with asymmetrical contour

The electrophoretic deposition (EPD) is used to serve as rapid prototyping technology (RPT) to manufacture ceramic mini-devices containing internal channels or asymmetrical contour patterns to overcome the technical obstacles by conventional ceramic forming techniques. The spacing and geometry of such internal channels, either liner, curvilinear, symmetrical or asymmetrical, can be considered at the preliminary design stage to prepare the fugitive inactive inserts to be involved in EPD operations. Such inserts are limited to any undesirable chemical reaction with the EPD suspension and of easy elimination from EPD-formed ceramic green body followed by pyrolysis or solvent dissolution to remove from embedment. In this study, ferroelectric ceramic mini-devices based on barium titanate with the pattern containing internal channels was deposited via EPD route unto electrically conducting or non-conducting inserts buried in the ceramic laminates. The inserts can be removed after drying step. Effects of EPD conditions on shape integrity of internal channel in the mini-devices were examined. This novel ceramic shaping technique enables us to produce the ceramic mini-devices in terms of formation of desirable array patterns for the unique prototype of ceramic components such as dielectric resonators, waveguide or mini-actuators.     

Properties of electron-beam-welded and laser-welded austenitic Fe-28Mn-5Al-1C alloy

Austenitic Fe-28Mn-5Al-1C alloy was welded by electron-beam and CW CO₂ laser techniques. Tensile tests, impact tests, potentiodynamic and cyclic polarization measurements were used to evaluate the mechanical properties and corrosion behaviour of the weld materials, Metallographic examination showed that the microstructure of the electron-beam-welded and laser-welded metals consisted mainly of the columnar and equiaxed austenitic structures. Grain growth in the heat-affected zone (HAZ) was minimal for welding with these two techniques. The tensile and impact tests indicated that the weld materials exhibited lower tensile strength, percentage elongation, percentage reduction in area and impact energy than those of the base alloy. The polarization measurements revealed that the anodic polarization behaviour of the HAZs of the electron-beam-welded and laser-welded materials was identical to that of the base alloy when exposed in 1M Na₂SO₄ solution. However, the electron-beam-welded and laser-welded metals exhibited a higher current density in the passive region than that of the base alloy when exposed to 1N H₂SO₄ acid solution.     

Impact of Pre-Ozonation on Mechanical Properties of Selected Genotypes of Cucumber Fruits During the Souring Process

Cucumber souring is a process mediated by a microorganisms present on the surface of cucumber fruits. Sour pickles are fresh cucumbers that have been poured over with a sodium chloride solution and various types of spices. In the present research, pre-ozonated and control cucumber fruits were subjected to the souring processes. It was observed that ozone treatment had no negative impact on the quality of the fruit before the souring process. Moreover, sour pickles after pre-ozonation had better mechanic and sensory properties than the control.     

Piezoelectric properties of (Na1−xKx)NbO3‐based lead‐free piezoelectric ceramics and their application in knocking sensor

Piezoelectric knocking sensors with a dense microstructure were fabricated at 960°C for 2 hours using various CuO‐added (Na_0.5K_0.5)NbO₃ (NKN)‐based piezoelectric ceramics. The practical sensitivity (S_P) of the knocking sensor, which is the ability to detect the knocking of a car engine, was influenced by the g₃₃ × k_p value of the piezoelectric ceramics, indicating that the g₃₃ × k_p can be considered a figure of merit of the piezoelectric ceramics used in the knocking sensor. The knocking sensor synthesized using the CuO‐added 0.95(Na_0.5K_0.5)(Nb_0.95Sb_0.05)O₃–0.05CaTiO₃ (CNKNS–CT) ceramic, which showed a g₃₃ of 25.7 Vm/N and k_p of 0.46, exhibited a high S_P of 119 mV/g at the resonance frequency. The S_P of the commercial knocking sensor, which was synthesized using the Pb(Zr,Ti)O₃ (PZT)‐based ceramic, was 112 mV/g at the resonance frequency. Hence, the knocking sensor fabricated using the CNKNS–CT piezoelectric ceramic can be used to replace the commercial PZT‐based knocking sensor.     

Controller design for active noise control of compressor by using the time window POCS technique

Journal of Mechanical Science and Technology - To design an active noise controller, the transfer function between the reference signal and the error signal should be measured and defined. When the...     

Solid-state grafting of maleic anhydride onto polypropylene: The influence of morphology of polypropylene on heterogeneous reaction

Polypropylene (PP) was modified with maleic anhydride (MAH) via heterogeneous solid-state radical grafting performed in a fluidized polymerization reactor. The effect of PP morphology and different concentration of initiator (dibenzoyl peroxide, DBP) on the course of the reaction and grafting efficiency was evaluated with using infrared spectroscopy, scanning electron microscopy (SEM) and particle surface analysis (BET method). With respect to obtained results, the reaction course can be strongly affected by the reaction conditions and PP morphology. Unlike the reactive modification in melt, heterogeneous reaction exhibits lower extent of β-scission albeit the reaction conversion is lower. Solid-state grafting can be used as an alternative method for the surface modification of nonpolar surfaces with polar monomers under mild conditions.