Thermal Degradation of Vegetable Oils.

Vegetable oils provide lipids and nutrition and provide foods with a desirable flavor, color, and crispy texture when used to prepare fried foods. However, the oil quality is degraded at elevated temperatures, and thus must be examined frequently because of the damage to human health. In this study, sunflower, soybean, olive, and canola oils were examined, and their properties were measured periodically at different elevated temperatures. The unsaturated triglyceride in oils reacted with the environmental oxygen or water vapor significantly changes in optical absorbance, viscosity, electrical impedance, and acid value. We used defect kinetics to analyze the evolution of these oil properties at elevated temperatures. The optical absorbance, viscosity, and electrical impedance follow the second-order, first-order, and zeroth-order kinetics, respectively. The rate constants of the above kinetics satisfy the Arrhenius equation. Olive oil has the lowest rate of color center and dynamic viscosity among the four oils, with the smallest pre-exponential factor and the largest activation energy, respectively. The rate constants of acid reaction also satisfy the Arrhenius equation. The activation energies of the polar compound and acid reaction are almost the same, respectively, implying that the rate constant is controlled by a pre-exponential factor if four oils are compared. Olive oil has the largest rate constant of acid reaction among the four oils, with the lowest pre-exponential factor.

Stress Relaxation Behavior of Poly(Methyl Methacrylate)/Graphene Composites: Ultraviolet Irradiation.

The graphene/poly (methyl methacrylate) (PMMA) composites are a promising candidate for electronic, optoelectrical, and environmental applications. Understanding the mechanical degradation of PMMA-based materials is of practical importance in improving the reliability and lifespan of the associated structures and systems. In this study, we investigate the effects of functionalized graphene (FG) and UV irradiation on the stress-relaxation of PMMA. Uniaxial tensile and stress -relaxation tests are performed to evaluate the mechanical properties of the composites. The mechanical strength and elongation at the break increase with the graphene concentration but decrease with the increase of the irradiation dose. Raman spectroscopy and intrinsic viscosity measurement are applied to examine the root cause of the degradation in the composites. UV irradiation leads to polymer chain scission and loss of molecular weight. The Kelvin representation of the standard linear solid model (SLSM) is used to describe the stress-relaxation curves of the composites. The value of the elastic modulus in the Kelvin element decreases with the increase in temperature. The viscosity follows the Arrhenius equation. The activation energy of viscosity increases with the increasing FGs concentration because the FGs hinder the chain motion of PMMA. However, UV irradiation makes chain scission of PMMA/FGs composite so that the polymer chain moves more easily and the activation energy of stress relaxation lowers. The steady-state stress follows the van 't Hoff equation that stress relaxation is an exothermal deformation process. Although Maxwell's representation of SLSM is mathematically identical to the Kelvin representation of SLSM, the former cannot interpret the stress-relaxation behavior of PMMA/FGs composite, which is against the concept of Young's modulus as a decreasing temperature function.

Caffeine Extraction from Raw and Roasted Coffee Beans.

Coffee is a stimulant, psychoactive, popular daily beverage, and its caffeine affects human physiological health and behavior. These important issues prompted us to study caffeine extraction from both the raw and roasted coffee beans of 3 types at different temperatures. A hemispheric model is developed to simulate the extraction process of the caffeine from the coffee beans of hemisphere is proposed. The experimental data are in good agreement with the predicted model. The effective diffusivities of caffeine in both the raw and roasted beans increase with temperature in all 3 types. An incubation period, decreasing with increasing temperature, is observed in all samples studied. Caffeine extraction in roasted beans is more rapid than that for the raw beans and the time difference is significant at low temperatures. In both the raw and roasted samples, caffeine diffusion in the raw beans and the incubation behavior are thermally activated processes. Single activation energies are obtained for diffusion within the extraction temperature range for all beans tested with the exception of one type of the coffee beans, Mandheling, which exhibits 2 activation energies in raw samples. The surface energies of the epidermis of the raw beans and roasted beans obtained from the contact angle measurements are used to interpret the difference of incubation periods. PRACTICAL APPLICATION: This study has a potential application to the decaffeinated coffee industry.Caffeine affects human physiological health and behavior so that caffeine extraction from coffee beans of different types at different temperatures is important for product refining and customers.

Kinetics of Field-Induced Surface Patterns on PMMA.

A simple model was developed to analyze the growth of a liquid pillar under the action of an electric field between two parallel electrodes. A quadratic relationship between time and the diameter of the pillar was obtained. The diameter of the pillar increases with time. Large electric field assists the growth of the liquid pillar, while a liquid with a large viscosity hinders the growth of the liquid pillar. The field-induced formation and growth of PMMA pillars on PMMA films were observed using the configuration of a parallel capacitor. Pillars of larger sizes and smaller densities were formed on thicker PMMA films than on thinner PMMA films. The root-mean-square ( https://en.wikipedia.org/wiki/Root_mean_square ) diameter of the pillars increases with the increase of the annealing time and annealing temperature. The growth behavior of the pillars can be described by an Arrhenius relation with an activation energy of 24.4 kJ/mol, suggesting that the growth of the pillars is controlled by a thermal activation process.

Preparation of Aluminum Oxide-Coated Glass Slides for Glycan Microarrays.

In this study, we report the fabrication of aluminum oxide-coated glass (ACG) slides for the preparation of glycan microarrays. Pure aluminum (Al, 300 nm) was coated on glass slides via electron-beam vapor deposition polymerization (VDP), followed by anodization to form a thin layer (50-65 nm) of aluminum oxide (Al-oxide) on the surface. The ACG slides prepared this way provide a smooth surface for arraying sugars covalently via phosphonate formation with controlled density and spatial distance. To evaluate this array system, a mannose derivative of α-5-pentylphosphonic acid was used as a model for the optimization of covalent arraying based on the fluorescence response of the surface mannose interacting with concanavalin A (ConA) tagged with the fluorescence probe A488. The ACG slide was characterized using scanning electron microscopy, atomic force microscopy (AFM), and ellipsometry, and the sugar loading capacity, uniformity, and structural conformation were also characterized using AFM, a GenePix scanner, and a confocal microscope. This study has demonstrated that the glycan array prepared from the ACG slide is more homogeneous with better spatial control compared with the commonly used glycan array prepared from the N-hydroxysuccinimide-activated glass slide.

Head-up display using an inclined Al2O3 column array.

An orderly inclined Al2O3 column array was fabricated by atomic layer deposition and sequential electron beam evaporation using a hollow nanosphere template. The transmittance spectra at various angles of incidence were obtained through the use of a Perkin-Elmer Lambda 900 UV/VIS/NIR spectrometer. The inclined column array could display the image information through a scattering mechanism and was transparent at high viewing angles along the deposition plane. This characteristic of the inclined column array gives it potential for applications in head-up displays in the automotive industry.

FTO films deposited in transition and oxide modes by magnetron sputtering using tin metal target.

Fluorine-doped tin oxide (FTO) films were prepared by pulsed DC magnetron sputtering with a metal Sn target. Two different modes were applied to deposit the FTO films, and their respective optical and electrical properties were evaluated. In the transition mode, the minimum resistivity of the FTO film was 1.63×10(-3) Ω cm with average transmittance of 80.0% in the visible region. Furthermore, FTO films deposited in the oxide mode and mixed simultaneously with H2 could achieve even lower resistivity to 8.42×10(-4) Ω cm and higher average transmittance up to 81.1% in the visible region.

Conductive and transparent multilayer films for low-temperature TiO2/Ag/SiO2 electrodes by E-beam evaporation with IAD.

Conductive and transparent multilayer thin films consisting of three alternating layers (TiO2/Ag/SiO2, TAS) have been fabricated for applications as transparent conducting oxides. Metal oxide and metal layers were prepared by electron-beam evaporation with ion-assisted deposition, and the optical and electrical properties of the resulting films as well as their energy bounding characteristics and microstructures were carefully investigated. The optical properties of the obtained TAS material were compared with those of well-known transparent metal oxide glasses such as ZnO/Ag/ZnO, TiO2/Ag/TiO2, ZnO/Cu/ZnO, and ZnO/Al/ZnO. The weathering resistance of the TAS film was improved by using a protective SiO2 film as the uppermost layer. The transmittance spectra and sheet resistance of the material were carefully measured and analyzed as a function of the layer thickness. By properly adjusting the thickness of the metal and dielectric films, a low sheet resistance of 6.5 ohm/sq and a high average transmittance of over 89% in the 400 to 700 nm wavelength regions were achieved. We found that the Ag layer played a significant role in determining the optical and electrical properties of this film.

Edge isolation of transparent conductive polymer (TCP) thin films on flexible substrates using UV laser ablation.

The purpose of this study was to directly use the writing techniques for the complex electrode edge isolation of transparent conductive polymer (TCP) thin films by a nanosecond pulsed UV laser processing system. The processing parameters including the laser pulse energy, the pulse repetition frequency, and the scan speed of galvanometers were examined to ablate the TCP films deposited on polyethylene terephtalate substrates of 188 microm thick. The thickness of TCP films was approximately 20 nm. The laser pulse repetition frequency and the scan speed of galvanometers were applied to calculate the overlapping rate of laser spots and to discuss the patterning region quality. Surface morphology, edge quality, and width and depth of edge isolated patterning structures after laser ablation process were measured by a three-dimensional confocal laser scanning microscope. In addition, the electrical conductivity of ablated TCP films was measured by a four-point probes instrument. After isolated line patterning was formed, the ablated TCP films with a better edge quality were obtained directly when the overlapping rate of laser spots, the scan speed, and the pulse repetition rate were 83.3%, 200 mm/s, and 40 kHz, respectively. The better surface morphology of electrode pattern structures was also obtained when the scan speed and the pulse repetition rate were 500 mm/s and 40 kHz, respectively.

The sub-micron hole array in sapphire produced by inductively-coupled plasma reactive ion etching.

The sub-micron hole array in a sapphire substrate was fabricated by using nanosphere lithography (NSL) combined with inductively-coupled-plasma reactive ion etching (ICP-RIE) technique. Polystyrene nanospheres of about 600 nm diameter were self-assembled on c-plane sapphire substrates by the spin-coating method. The diameter of polystyrene nanosphere was modified by using oxygen plasma in ICP-RIE system. The size of nanosphere modified by oxygen plasma was varied from 550 to 450 nm with different etching times from 15 to 35 s. The chromium thin film of 100 nm thick was then deposited on the shrunk nanospheres on the substrate by electron-beam evaporation system. The honeycomb type chromium mask can be obtained on the sapphire substrate after the polystyrene nanospheres were removed. The substrate was further etched in two sets of chlorine/Argon and boron trichloride/Argon mixture gases at constant pressure of 50 mTorr in ICP-RIE processes. The 400 nm hole array in diameter can be successfully produced under suitable boron trichloride/Argon gas flow ratio.

Binary blazed grating based on autostereoscopic display mechanism.

The diffractive optical element blazed grating is proposed as the beam splitter for autostereoscopic displays in this study. With Lithographie Galvanoformung Abformung and inductively coupled plasma reactive-ion etching, a four-level blazed grating structure is produced. Moreover, highly translucent polydimethylsiloxane is transformed into symmetrical four-level blazed grating films. The experimental results show that the film can successfully transmit the left and the right images to the accurate positions, and the diffraction efficiency is 70.4% and the contrast ratio is above 80%, presenting the original stereoscopic image without it being affected by brightness and crosstalk. In the experiment of stereoscopic imaging, both the left and the right images could be clearly acquired, which proves the feasibility of blazed gratings as practical for the beam splitter of autostereoscopic displays.

Mechanical properties of Pt-Ir and Ni-Ir binary alloys for glass-molding dies coating.

In this study, the different compositions of Pt-Ir and Ni-Ir alloys were deposited by utilizing ion source assisted magnetron sputtering system (ISAMSS). The surface roughness and crystallite size of the Pt-Ir and Ni-Ir coatings were analyzed by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. In addition, coatings were soaked at 700 degrees and maintained 10 min under N2 atmosphere using a glass-molding machine. The annealed coatings for oxidation test were examined by energy dispersive X-ray spectrometry (EDS) and for microhardness and reduced modulus test were evaluated by nanoindentation instrucment. The cross-sectional structures between the Pt-Ir and Ni-Ir coating layer and substrates were also examined by field emission scanning electron microscope (FESEM). The results show that surface roughness Ra from 1.25 nm to 3.426 nm was observed with increasing the Ni elements. However, the Ra is less than 2 nm measured in Ir-based coatings doped with Pt concentrations under this study. With increasing Pt and Ni doping, the microhardness of both coatings decreased significantly and the values of reduced modulus of Pt-Ir alloys are larger than that of Ni-Ir alloys. After oxidation process, the oxygen concentration of Pt-Ir coatings is less than that of Ni-Ir coatings and the Pt-Ir coatings exhibit superior properties including oxidation resistance, low surface roughness and high reduced modulus over Ni-Ir coatings, especially for the high Pt concentration coatings such as Pt-Ir 2 (55.25 at.% Pt) and Pt-Ir 3 (79.42 at.% Pt) coatings. The surface roughnesses of all specimens annealed at 700 degrees C were slightly larger than as-deposited coatings. Moreover, due to the serious oxidation occurred in Ni-Ir 3 (73.45 at.% Ni) coatings, the value of reduced modulus of this specimen coating is the lowest and the corrsponding Ra value is the largest compared with the rest of Ir-based coatings in the oxidation testing.