Electrical Properties For Use Research Articles

Using supervised machine learning methods to predict microfiber alignment and electrical conductivity of polymer matrix composite materials fabricated with ultrasound directed self-assembly and stereolithography

Engineered polymer matrix composite materials with designer electrical properties are important for a myriad of engineering applications including flexible actuators and wearable sensors. We use stereolithography in combination with ultrasound directed self-assembly to align electrically conductive microfibers in a photopolymer matrix. We relate the fabrication process parameters to the resulting filler material alignment and corresponding electrical conductivity using supervised machine learning methods and quantify the prediction accuracy of data-driven models derived from different interpretable and non-interpretable algorithms. We determine that decision tree and artificial neural network algorithms result in data-driven models with R2 scores that are 79.8% and 83.2% higher, respectively, than a traditional multivariate regression analysis benchmark model in predicting the microfiber alignment. Similarly, random forest and artificial neural network algorithms result in data-driven models that predict composite material electrical conductivity 9.1% and 13.7% more accurately, respectively, than a logistic multivariate regression benchmark model. Relating the fabrication process parameters to the resulting electrical conductivity of the material is a crucial step towards fabricating polymer matrix composite materials with designer electrical properties for use in engineering applications.

ULTRASONIC SPRAY-ASSISTED CVD GROWTH OF HIGHLY TRANSPARENT AND CONDUCTIVE ALUMINUM-DOPED ZnO

Zinc oxide [Formula: see text], undoped and Al-doped thin films have been synthesized by the ultrasonic spray-assisted chemical vapor deposition (USCVD) system. The films were deposited on glass substrates. The precursor solution was prepared dissolving zinc chloride in distilled water. First, the precursor concentrations were investigated and optimized before studying [Formula: see text] doped, after we have studied the [Formula: see text]-doped influence on [Formula: see text] films especially optical and electrical properties for use as a transparent conductive oxide (TCO) in solar cell electrodes. The characterizations have been carried out using X-ray diffraction technique, UV-vis spectrophotometry, Hall Effect measurement (ECOPIA), atomic force microscopy (AFM, VEECO Dimension [Formula: see text] and scanning electron microscopy (SEM). X-ray diffraction (XRD) results showed that [Formula: see text] and [Formula: see text]-doped [Formula: see text] films were crystallized in the hexagonal wurtzite structure with [Formula: see text] orientation. Optical measurements have shown that all films exhibit, along the visible range, high transmittance and that optical band gap depends strongly to [Formula: see text]-doped concentration. Hall-effect measurement indicates that the highest carrier concentration [Formula: see text] and the lowest resistivity [Formula: see text] are obtained for the [Formula: see text] AZO sample. The SEM shows that the microstructures of [Formula: see text] and [Formula: see text] are homogeneous and the AFM images prove their microcrystallinity with grains orthogonal to the film surface.

Structure and Dielectric Properties of Electroactive Tetraaniline Grafted Non-Polar Elastomers

Intrinsic modification of polybutadiene and block copolymer styrene–butadiene–styrene with the electrically conducting emeraldine salt of tetraaniline (TANI) via a three-step grafting method, is reported in this work. Whilst the TANI oligomer grafted at a similar rate to both polybutadiene and styrene–butadiene–styrene under the same conditions, the resulting elastomers exhibited vastly different properties. 1 mol% TANI-PB exhibited an increased relative permittivity of 5.9, and a high strain at break of 156%, whilst 25 mol% TANI-SBS demonstrated a relative permittivity of 6.2 and a strain at break of 186%. The difference in the behaviour of the two polymers was due to the compatibilisation of TANI by styrene in SBS through π-π stacking, which prevented the formation of a conducting TANI network in SBS at. Without the styrene group, TANI-PB formed a phase separated structure with high levels of TANI grafting. Overall, it was concluded that the polymer chain structure, the morphology of the modified elastomers, and the degree of grafting of TANI, had the greatest effect on the mechanical and dielectric properties of the resultant elastomers. This work paves the way for an alternative approach to the extrinsic incorporation of conducting groups into unsaturated elastomers, and demonstrates dielectric elastomers with enhanced electrical properties for use in actuation devices and energy harvesting applications.

Electrical, thermal and rheological properties of low-density polyethylene/ethylene vinyl acetate/graphene-like composite

Composites of low-density polyethylene (LDPE), ethylene vinyl acetate (EVA), and a graphene-like material were explored for their electrical properties for use in high-volume low-cost conductive applications. A graphene-like material, obtained from hybrid clay-sucrose carbonization, was investigated as an alternative filler with advantages over conventional graphene technology. The electrical properties of the composites as synthesized by the solvent–casting technique were studied using broadband dielectric spectroscopy. The percolation threshold was identified for both as synthesized and annealed composite samples. Due to charge transport and electrode polarization, the sub-percolating composites exhibited low frequency dispersion particularly at elevated temperatures. Composites of LDPE/EVA/graphene-like above the percolation threshold exhibited a higher rheological storage modulus and thermal stability which indicates an alignment between the electrical, thermal and rheological properties.

Rare earth-doped lead titanate zirconate grown on carbon fibers by microwave-assisted hydrothermal synthesis

This study aimed to develop a flexible carbon fiber/oxide layer coating composite with improved electrical properties for use in electronic devices. For this, lead titanate zirconate, cerium-doped lead titanate zirconate, and yttrium-doped lead titanate zirconate were grown on carbon fibers via microwaves-assisted hydrothermal synthesis. The performed synthesis presented advantages when compared to conventional routes used in nanoparticles obtention since it allows the morphological control even at low temperatures. Carbon fiber was selected as substrates due to their thermal stability, excellent mechanical properties, chemical characteristics that allow the creation of functional groups on their surface, and good microwave radiation absorption. The composites were investigated by X-ray diffraction, spectroscopy Raman, and field emission scanning electron microscopy. The electrochemical evaluations were made by four-point probe method, cyclic voltammetry, and electrochemical impedance spectroscopy. The syntheses were successful and the carbon fiber coated with lead zirconate titanate had promissory results, with a boost in the electrical conductivity and better capacitance behavior when compared to the undoped carbon fiber, showing to be a good alternative for applications in electrical devices.

Processing and electrical conductivity of non-stoichiometric lanthanum strontium manganite perovskites prepared from powders synthesized by a polymerizable-complexation route

Perovskite ceramics with non-stoichiometric compositions given by (La0.85Sr0.15)0.98MnO3-δ ((LS)0.98M-85) and (La0.80Sr0.20)0.98MnO3-δ ((LS)0.98M-80) were obtained by pressureless sintering (1500 °C for 2 h) from powders synthesized by a polymerizable-complexation route and then calcined (500 °C for 1 h). It was found that the two sintered ceramics contain trigonal (i.e., R3̅c) Sr-doped lanthanum manganite as majority phase, and also hexagonal (i.e., P63/m) La(OH)3 in trace amounts in the case of (LS)0.98M-85 and in abundant amounts in the case of (LS)0.98M-80. The (LS)0.98M-85 ceramic is stable and therefore usable, whereas on the contrary the (LS)0.98M-80 ceramic eventually swelled and turned into a powder due to the abundant La(OH)3 that uptakes water from the atmosphere. Finally, it was found that the (LS)0.98M-85 ceramic has appropriate electrical properties for use as cathode in solid oxide fuel cells, with a total conductivity of ~ 145 S/cm at 1000 °C and an activation energy of 0.067(2) eV.

Water-Erasable Memory Device for Security Applications Prepared by the Atomic Layer Deposition of GeO2

We have investigated the atomic layer deposition (ALD) of GeO2 thin films that dissolve in water rapidly and have excellent electrical properties for use in memory devices. The growth characteristics based on surface reactions during the ALD process are discussed by correlation with experimental results and atomistic theoretical calculation. Compared to sputtered GeO2 films, the ALD-grown GeO2 is perfect, pure, and water-soluble at room temperature and has better electrical properties for use as the dielectric layer in memory devices. The superior film properties of ALD GeO2 are attributed to the higher film density, high purity, low roughness, and highly stoichiometric film composition. Finally, we demonstrate the fabrication of charge-trapping memory (CTM) devices with ALD GeO2, and that the electrical information stored in the CTM can be eliminated immediately by exposure to one droplet of water at room temperature. Thus, ALD GeO2 could find widespread application in the fabrication of secure memory de...

Morphological and Electrical Stability Studies of Pt/Yttria-Stabilized Zirconia Nanocomposite Thin Film Cathodes for Microfabricated Solid Oxide Fuel Cells

Abstract Microfabricated solid oxide fuel cells (mSOFCs) have recently gained attention as a promising technology for portable power applications. At present, porous Pt is the most common cathode being investigated for mSOFCs, which has poor bulk ionic conductivity and suffers from instability due to Ostwald ripening. Nanocomposite materials based on Pt/Yttria-Stabilized Zirconia (YSZ) are a promising alternative approach for high performance mSOFCs because of their potential for providing mixed ionic-electronic conduction, improving adhesion to the YSZ electrolyte, and improving oxygen diffusion characteristics over a pure Pt material. The objective of this research was to systematically explore the processing of the nanocomposite thin films to achieve stable morphological and electrical properties for use as a mSOFC cathode. A percolation theory model was utilized to guide the processing of the Pt/YSZ composition, ensuring a networked connection of ionic- and electronic-conduction through the electrode. The Pt/YSZ nanocomposite cathodes were deposited by co-sputtering. It was observed that the Ar deposition pressure played a key role in stabilizing the morphology of the film to higher temperatures, up of 600°C. Analyses of the Pt/YSZ composite microstructure and composition by TEM confirmed an interconnected network of Pt and YSZ thereby suggesting that it is a viable candidate as a high performance and stable cathode material for mSOFCs.

Nanopillar InGaN/GaN light emitting diodes integrated with homogeneous multilayer graphene electrodes

InGaN/GaN nanopillar light-emitting diodes (LEDs) were fabricated using a highly homogeneous multilayer graphene (h-MLG) electrode. Four layers of h-MLG were prepared homogeneously using chemical vapor deposition and layer-by-layer transfer methods. The h-MLG exhibited excellent optical, structural and electrical properties for use as an electrode in the LEDs. The h-MLG was applied as a transparent top electrode by suspending only on the tip of nanopillar LEDs. The current-driven InGaN/GaN nanopillar LED with the h-MLG electrode was successfully operated at a high current injection and exhibited bright electroluminescence.

Glasses for High-Resistivity Thick-Film Resistors

Knowledge about the role of the glass matrix in thick-film resistors is necessary for improvement of their electrical properties for use in high-performance components. The influence of glass composition on the microstructure of ruthenate conductor and resistor parameters has been studied. Additions of TiO 2 , GeO 2 , and TeO 2 , which in dilute concentrations markedly increase the resistivity, improve the temperature coefficient of the resistance and the voltage stability. The oxide enrichment of the glass film between the conducting particles reduces the ruthenium-ion solubility and decreases the tunneling conductivity between the conductor grains.

Deposition of highly crosslinked fluorinated amorphous carbon film and structural evolution during thermal annealing

Highly crosslinked fluorinated amorphous carbon films are obtained by increasing deposition temperature, enhancing ion bombardment, and fine tuning the fluorine-to-carbon ratio. The as-deposited films undergo significant mechanical, chemical, and electrical changes after thermal annealing. Most importantly, these changes occur only at the initial stage of annealing. After the thermal treatment, the films tend to be thermally stable and retain reasonably good electrical properties for use as a low-k dielectric.

R.F. sputtering of plastics

This paper outlines the application of r.f. sputtering to plastic as a means of obtaining thinner dielectric layers with good electrical properties for use in the capacitor industry. The construction and characteristics of the sputtering system employed to obtain thin films of PTFE are described. A brief résumé of the differences observed between such films and conventional PTFE is included together with a short discussion of the observed electrical behaviour.