Current conduction mechanisms of atomic-layer deposited Al 2 O 3 (13 nm) stacked on different the... more Current conduction mechanisms of atomic-layer deposited Al 2 O 3 (13 nm) stacked on different thermal nitrided SiO 2 thicknesses (2, 4, and 6 nm) on n-type 4 H-SiC have been systematically analyzed. It has been observed that the oxides were thermally stable at the investigated temperature range (25–140°C). By using different conduction process models, such as Schottky emission, direct tunneling, Fowler–Nordheim tunneling, Poole–Frenkel emission, and space-charge limited conduction, which consists of three limited conduction processes, namely, Ohm's law, Child's law, and trap-filled limit, the conduction mechanisms of charge through the oxides have been evaluated. It has been found that the conduction mechanisms were not affected by the investigated temperature range. A relationship plot has been proposed among nitrided SiO 2 thickness, electric field, and conduction mechanisms.
... Talib, Othman Mohd Yusof, Saiful Aman Hj Sulaiman, Mat Akhir Md Wazir, Azani Azizan Centre of... more ... Talib, Othman Mohd Yusof, Saiful Aman Hj Sulaiman, Mat Akhir Md Wazir, Azani Azizan Centre of Geospatial Technology (CGT) Department Surveying Science and Geomatics Faculty of Architecture, Planning and Surveying Universiti Teknologi MARA, MALAYSIA Shah Alam ...
The gram negative bacterium Escherichia coli has evolved a highly specific system for the transpo... more The gram negative bacterium Escherichia coli has evolved a highly specific system for the transport of exogenous long-chain fatty acids (C12-C18) across the cell envelope that requires the outer membrane protein FadL and the inner membrane associated fatty acyl CoA synthetase. The transport of oleate (C18:1) across the cell envelop responds to metabolic energy. In order to define the source of metabolic energy which drives this process, oleate transport was measured in wild-type and ATP synthase-defective (Deltaatp) strains which were (i) subjected to osmotic shock and (ii) starved and energized with glucose or d-lactate in the presence of different metabolic inhibitors. Osmotic shock did not eliminate transport but rather reduced the rate to 33-55% of wild-type levels. These results suggested a periplasmic protein may participate in this process or that osmotic shock disrupts the energized state of the cell which in turn reduces the rate of oleate transport. Transport systems which are osmotically sensitive also require ATP. The process of long-chain fatty acid transport requires ATP generated either by substrate-level or oxidative phosphorylation. Following starvation, the basal rate of transport for wild-type cells was 340.4 pmol/min/mg protein compared to 172.0 pmol/min/mg protein for the Deltaatp cells. When cells are energized with glucose, the rates of transport were increased and comparable (1242.6 and 1293.8 pmol/min/mg protein, respectively). This was in contrast to cells energized with d-lactate in which only the wild-type cells were responsive. The role of ATP is likely due to the ATP requirement of fatty acyl CoA synthetase for catalytic activity. The process of oleate transport is also influenced by the energized state of the inner membrane. In the presence of carbonyl cyanide-m-chlorophenylhydrazone oleate transport is depressed to 30-50% of wild-type levels in wild-type and Deltaatp strains under starvation conditions. These results are mirrored in cells energized with glucose and d-lactate, indicating that an energized membrane is required for optimal levels of oleate transport. These data support the hypothesis that the fatty acid transport system of E. coli responds to both intracellular pools of ATP and an energized membrane for maximal proficiency.
In water phase,silver nano-colloid was prepared by chemical reduction method with sodium borohydr... more In water phase,silver nano-colloid was prepared by chemical reduction method with sodium borohydride as reductant,lauric acid as dispersant,and silver-ammonia complex as main salt.Then,by adding phosphoric acid to adjust pH value of the colloidal system,silver nanoparticles were precipitated and separated.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses showed that the prepared Ag nanoparticles have an average diameter of about 17 nm with the distribution of 5~30 nm,and had no agglomeration.FT-IR spectrum indicated that the nanoparticles are capsulated by lauric acid,and UV-Vis spectrum revealed that the Ag nano-colloid has a strong absorption peak at 397 nm.Using the prepared wet Ag nanoparticles as functional phase,a conductive nano-silver paste was formulated with an organic vehicle by dispersion methods of mechanical stirring and ultrasonic vibration.Thermogravimetry analysis(TGA) showed that the paste contains 67 wt% Ag.Its electrical resistivity is up to 4.2×10-5 Ω·cm after sintering at 220℃ for 2 h.Upon direct-writing by micro-pen,an array pattern with the resolution of 60 μm is achieved.
... but did not show size dependency effects [15]. Recent reports on other magnetic ion-doped fer... more ... but did not show size dependency effects [15]. Recent reports on other magnetic ion-doped ferromagnetic oxides (eg Co-doped ZnO, Cr-doped ZnO and Ni-doped SnO2 nanoparticle samples) [1619] also indicate a link between defects and ferromagnetism. ...
The combination effects of hybrid nano–micron fillers and filler treatment on the thermal propert... more The combination effects of hybrid nano–micron fillers and filler treatment on the thermal properties of silver-filled epoxy composites are experimentally evaluated. These hybrid composites are fabricated using two different sizes and shapes of silver particles, namely 80 nm with spherical shape and 4–8 μm with flaky shape. In this study, the ratio of silver flakes to silver nanoparticles was varied from 100:0, 75:25, 50:50, 25:75, and 0:100 at a fixed silver loading of 6 vol.%. The silver fillers are treated with 3-aminopropyl triethoxysilane (3AMPTES) at different concentrations of 5, 10, and 30 wt%. The hybrid micro:nano at 50:50 shows the highest storage modulus and the lowest coefficient of thermal expansion (CTE) value compared with other ratios. The silver fillers with 10 wt% of 3AMPTES show improvement in storage modulus, CTE, and thermal stability compared with untreated and further increasing of 3AMPTES at 30 wt% did not show any significant improvement.
ABSTRACT Optically transparent, conductive, and mechanically flexible epoxy thin films are produc... more ABSTRACT Optically transparent, conductive, and mechanically flexible epoxy thin films are produced in the present study. Two types of multiwalled carbon nanotubes (MWCNTs) with different aspect ratios are dispersed in epoxy resin through an ultrasonication process. The MWCNT content is varied during the preparation of the thin films. The light transmittance and electrical conductivity of the thin films are characterized. Results show that composites containing MWCNTs with a lower aspect ratio exhibit enhanced electrical conductivity compared to those with a higher aspect ratio. A sheet resistance as low as 100 Ω/sq with nearly 60% optical transparency in 550 nm is achieved with the addition of MWCNTs in epoxy. In summary, transparent, conductive, and flexible MWCNT/epoxy thin films are successfully produced, and the properties of such films are governed by the aspect ratio and content of MWCNTs.
Current conduction mechanisms of atomic-layer deposited Al 2 O 3 (13 nm) stacked on different the... more Current conduction mechanisms of atomic-layer deposited Al 2 O 3 (13 nm) stacked on different thermal nitrided SiO 2 thicknesses (2, 4, and 6 nm) on n-type 4 H-SiC have been systematically analyzed. It has been observed that the oxides were thermally stable at the investigated temperature range (25–140°C). By using different conduction process models, such as Schottky emission, direct tunneling, Fowler–Nordheim tunneling, Poole–Frenkel emission, and space-charge limited conduction, which consists of three limited conduction processes, namely, Ohm's law, Child's law, and trap-filled limit, the conduction mechanisms of charge through the oxides have been evaluated. It has been found that the conduction mechanisms were not affected by the investigated temperature range. A relationship plot has been proposed among nitrided SiO 2 thickness, electric field, and conduction mechanisms.
... Talib, Othman Mohd Yusof, Saiful Aman Hj Sulaiman, Mat Akhir Md Wazir, Azani Azizan Centre of... more ... Talib, Othman Mohd Yusof, Saiful Aman Hj Sulaiman, Mat Akhir Md Wazir, Azani Azizan Centre of Geospatial Technology (CGT) Department Surveying Science and Geomatics Faculty of Architecture, Planning and Surveying Universiti Teknologi MARA, MALAYSIA Shah Alam ...
The gram negative bacterium Escherichia coli has evolved a highly specific system for the transpo... more The gram negative bacterium Escherichia coli has evolved a highly specific system for the transport of exogenous long-chain fatty acids (C12-C18) across the cell envelope that requires the outer membrane protein FadL and the inner membrane associated fatty acyl CoA synthetase. The transport of oleate (C18:1) across the cell envelop responds to metabolic energy. In order to define the source of metabolic energy which drives this process, oleate transport was measured in wild-type and ATP synthase-defective (Deltaatp) strains which were (i) subjected to osmotic shock and (ii) starved and energized with glucose or d-lactate in the presence of different metabolic inhibitors. Osmotic shock did not eliminate transport but rather reduced the rate to 33-55% of wild-type levels. These results suggested a periplasmic protein may participate in this process or that osmotic shock disrupts the energized state of the cell which in turn reduces the rate of oleate transport. Transport systems which are osmotically sensitive also require ATP. The process of long-chain fatty acid transport requires ATP generated either by substrate-level or oxidative phosphorylation. Following starvation, the basal rate of transport for wild-type cells was 340.4 pmol/min/mg protein compared to 172.0 pmol/min/mg protein for the Deltaatp cells. When cells are energized with glucose, the rates of transport were increased and comparable (1242.6 and 1293.8 pmol/min/mg protein, respectively). This was in contrast to cells energized with d-lactate in which only the wild-type cells were responsive. The role of ATP is likely due to the ATP requirement of fatty acyl CoA synthetase for catalytic activity. The process of oleate transport is also influenced by the energized state of the inner membrane. In the presence of carbonyl cyanide-m-chlorophenylhydrazone oleate transport is depressed to 30-50% of wild-type levels in wild-type and Deltaatp strains under starvation conditions. These results are mirrored in cells energized with glucose and d-lactate, indicating that an energized membrane is required for optimal levels of oleate transport. These data support the hypothesis that the fatty acid transport system of E. coli responds to both intracellular pools of ATP and an energized membrane for maximal proficiency.
In water phase,silver nano-colloid was prepared by chemical reduction method with sodium borohydr... more In water phase,silver nano-colloid was prepared by chemical reduction method with sodium borohydride as reductant,lauric acid as dispersant,and silver-ammonia complex as main salt.Then,by adding phosphoric acid to adjust pH value of the colloidal system,silver nanoparticles were precipitated and separated.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses showed that the prepared Ag nanoparticles have an average diameter of about 17 nm with the distribution of 5~30 nm,and had no agglomeration.FT-IR spectrum indicated that the nanoparticles are capsulated by lauric acid,and UV-Vis spectrum revealed that the Ag nano-colloid has a strong absorption peak at 397 nm.Using the prepared wet Ag nanoparticles as functional phase,a conductive nano-silver paste was formulated with an organic vehicle by dispersion methods of mechanical stirring and ultrasonic vibration.Thermogravimetry analysis(TGA) showed that the paste contains 67 wt% Ag.Its electrical resistivity is up to 4.2×10-5 Ω·cm after sintering at 220℃ for 2 h.Upon direct-writing by micro-pen,an array pattern with the resolution of 60 μm is achieved.
... but did not show size dependency effects [15]. Recent reports on other magnetic ion-doped fer... more ... but did not show size dependency effects [15]. Recent reports on other magnetic ion-doped ferromagnetic oxides (eg Co-doped ZnO, Cr-doped ZnO and Ni-doped SnO2 nanoparticle samples) [1619] also indicate a link between defects and ferromagnetism. ...
The combination effects of hybrid nano–micron fillers and filler treatment on the thermal propert... more The combination effects of hybrid nano–micron fillers and filler treatment on the thermal properties of silver-filled epoxy composites are experimentally evaluated. These hybrid composites are fabricated using two different sizes and shapes of silver particles, namely 80 nm with spherical shape and 4–8 μm with flaky shape. In this study, the ratio of silver flakes to silver nanoparticles was varied from 100:0, 75:25, 50:50, 25:75, and 0:100 at a fixed silver loading of 6 vol.%. The silver fillers are treated with 3-aminopropyl triethoxysilane (3AMPTES) at different concentrations of 5, 10, and 30 wt%. The hybrid micro:nano at 50:50 shows the highest storage modulus and the lowest coefficient of thermal expansion (CTE) value compared with other ratios. The silver fillers with 10 wt% of 3AMPTES show improvement in storage modulus, CTE, and thermal stability compared with untreated and further increasing of 3AMPTES at 30 wt% did not show any significant improvement.
ABSTRACT Optically transparent, conductive, and mechanically flexible epoxy thin films are produc... more ABSTRACT Optically transparent, conductive, and mechanically flexible epoxy thin films are produced in the present study. Two types of multiwalled carbon nanotubes (MWCNTs) with different aspect ratios are dispersed in epoxy resin through an ultrasonication process. The MWCNT content is varied during the preparation of the thin films. The light transmittance and electrical conductivity of the thin films are characterized. Results show that composites containing MWCNTs with a lower aspect ratio exhibit enhanced electrical conductivity compared to those with a higher aspect ratio. A sheet resistance as low as 100 Ω/sq with nearly 60% optical transparency in 550 nm is achieved with the addition of MWCNTs in epoxy. In summary, transparent, conductive, and flexible MWCNT/epoxy thin films are successfully produced, and the properties of such films are governed by the aspect ratio and content of MWCNTs.
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