Search

An electrical tree discharge model of multilayer insulation paper was prepared, and a voltage of 20 kV was used for electrical tree cultivation and initiation tests. Based on the microscopic image information and partial discharge (PD) information during the aging of the electrical tree, the development of electrical tree discharges between layers of paper comprising epoxy resin-impregnated paper insulation was studied. The results show that, by analysing PD information such as the discharge volume phase spectrum and the discharge repetition rate phase spectrum, the development of the electrical tree branch progresses in four stages: initial, growth, stagnation, and bursting. During the growth and stagnation stages, the main discharge paths of the electrical tree are mainly formed, and there are many filamentous fibres on the path edge. During the burst stage, more branches will be formed on the electrical tree, which will cause the greatest damage to the insulation. With the extension of the electrical tree path, the discharge magnitude and discharge times also increase. There are specific discharge patterns in different growth stages of the electrical tree, and the number of discharge events in each positive half-cycle is significantly greater than that in a negative half-cycle. Combining the microscopic image information and PD information during the aging of such an electrical tree, a theoretical basis for evaluating insulation state by PD monitoring is realised. The long-chain molecules of cellulose and epoxy resin break bonds and oxidise, which decompose into a large number of free radicals, monosaccharides, and other low-molecular-weight products.

Kevlar pulp treated with low-temperature plasma and nano cellulose fibrils (NCFs) have been introduced as reinforcements in the preparation for composite insulating paper with low relative permittivity, dielectric loss, good mechanical properties, and thermal stability. More polar groups of Kevlar fibers could be exposed after plasma treatment. Results showed that the relative permittivity of the composite paper containing 20% Kevlar pulp, 10% NCF, and 70% softwood pulp is decreased by 29.6% and the dielectric loss is decreased by 43.2% at 50 Hz, 25°, compared with the conventional paper formed by pure softwood pulp. The change was due to the introduction of Kevlar pulp with intrinsic low dielectric constant and loss, which decreases the whole polarizability of the paper. The mechanical properties of the composite paper became worse after introducing 20% Kevlar pulp. About 10% NCF can work as a mechanical reinforcement to compensate for the tensile and Yang's modulus loss. Scanning electron microscopy results showed that NCF could fill the void defects and improve the interface bonding of the fibers to enhance the paper mechanical properties. The composite paper also had better insulating and thermal properties than the conventional paper. It has been concluded that the Kevlar pulp/NCF/softwood pulp composite paper has the potential to replace the pure softwood paper for the application of high-voltage ac transformer insulation.

Disposable low-cost sensors are essential for the detection of urea for environmental and healthcare applications. In this paper, we proposed a hand-drawn electrode paper chip sensor by utilising the enzyme modified cellulose fibre as a sensing and substrate material. Further modified cellulose fibres increase the impedance measurement stability and facilitate for performing detection. By demonstrating detection of the low-level concentration of urea in the micromolar range, it shows that developed paper chip has excellent potential as a low-cost disposable sensor.

Flexible supercapacitors are considered as a promising candidate for power supplementation in wearable electronics due to their high power density. However, effectively fabricate flexible and low-cost supercapacitor electrodes in a big scale is still a key challenge. Herein we demonstrate a scalable fabrication method for hierarchical electrodes via metalizing air-laid paper and loading with MnO2 as cathode active materials. To be specific, we coat a thin layer of Ni on air-laid paper by magnetron sputtering, then deposit Ni nanocone arrays (NNAs) on the Ni sputtered paper and finally deposit MnO2 on the NNAs to obtain the NNAs@MnO2 paper electrode. The as-prepared paper-based electrode possesses high conductivity and fine wettability, which facilitates the electrons and ions transporting through the conductive network. Additionally, this electrode provides large specific surface area with a hierarchical architecture. Thus the electrode shows high capacitance (451 F/g) and favorable cycle performance (92.9% capacity retention after cycling for 5000 times). By coupling with activated carbon (AC) coated on the NNAs conductive paper as anode, an NNAs paper-based asymmetric supercapacitor is constructed. Benefiting from the high mechanical durability and the 3D hierarchical architecture of the electrodes, the asymmetric supercapacitor exhibits excellent mechanical flexibility and high energy density (26.9 μWh/cm2 at 1.08 mW/cm2). This method can be easily scaled up to produce lightweight and low-cost conductive paper electrodes, making it promising for the application of flexible supercapacitors in wearable electronics.

We demonstrate the paper-based hydrogen peroxide sensors for the biomedical and healthcare applications. Porphyrin with central ions of Ti is coated on a PDMS/paper substrate, and Au interdigitated electrodes are sputtered on the porphyrin/PDMS/paper substrate for the sensor applications. The fabricated sensors show a good response in the range of ca. 2 ~ 90 ppm of hydrogen peroxide vapor, and high selectivity to NH 3 , H 2 S, CO, and NO gases, which are representative biomarkers including exhaled breath.

The influence of the degree of polymerisation (DP) of cellulose macromolecules in the short-term dielectric strength and mechanical tensile strength of the electrical insulating paper (EIP) was studied for the sulphate pine pulp. The resistance to prolonged exposure to elevated temperature was investigated. The changes of the structure of EIP and cellulose fibers during heat aging were analyzed. The data presented are expanding representations about the physical existence of the cellulose fibers and about the relationship between the operational resource of EIP and DP. On the basis of the data obtained the assumptions about the causes of discrepancies between experimental and calculated values of DP and limit of the mechanical strength of the paper are explained. The conclusions of the work are confirmed by micrographs the morphological features of the paper web before and after thermal aging. The opinion about need of correction of common perceptions about operational resource of cellulose dielectrics and paper impregnated insulation are reasoned.

We report a very simple and fast method to develop a fluidic system on Parylene C coated paper, based on fabrication of surface-tension-confined channels. As described here, the proposed method can be applied to fast fabrication of reusable and cheap analytical devices, as an alternative to disposable fluidic devices on paper. © 2017 IEEE.

Demand of wearable, portable, lightweight, foldable and eco-friendly electronics is enlarged, and compatible energy storage systems is a prominent topic of research. Highly cost efficient and foldable energy storage systems should be mounted on wearable, foldable and portable electronics. Current fabrication techniques of typical electronic systems are complex and expensive. To address these requirements, paper based foldable and easy go designed supercapacitor-based energy storage devices are suggested and reported. Electrochemical supercapacitors (ESCs) could store charges without chemical reaction and have fast charging/discharging speed. We reported an electric three-layer capacitor fabricated using aluminum foil-based electrodes on baking papers. Low cost and solvent free bench top fabrication process includes direct deposition of aluminum foil using gum on baking paper is demonstrated. Four layers of aluminum foil are stacked on baking paper to achieve high energy storage capability. This aluminum foil based layered structure gives us high conductivity and reliable charging/discharging properties. This device exhibits an excellent cyclability (>5,000 cycles). Device having minor retention in performance under continuous dynamic operations of forceful bending at different angles. The design concept is based on folding-cutting-pasting procedure that provides us flexible production protocol to design and manufacture supercapacitors with adaptable electrical characteristics and configurations. Baking paper is biopolymer-based substrate and can store 0.72 mJ energy. The Electrochemical supercapacitors are based on aluminum foil electrodes on baking paper with gum, so there can realize foldable, eco-friendly, ultra-low cost and easy go designed energy sources for foldable, portable, flexible, wearable and green electronics in the future. Electrochemical supercapacitors could be able to store energy generated from small portable energy generators like triboelectric Nanogenerators for portable, flexible and wearable electronic systems.

A commonly accepted serious drawback for cellulose paper is high water susceptibility, making it susceptible to moisture attack. In this study, six fully atomic cellulose models with different water contents were constructed to disclose the effects of water states on the mechanical properties of cellulose. Results showed that at low water concentrations, almost all water molecules belong to the bound state. With increasing water content, free water gradually prevails since the hydrophilic sites of cellulose have been occupied. Furthermore, free water has a strong capacity of the molecular movement to diffuse in amorphous cellulose, while bound water is fixed by cellulose. For the mechanical properties, both the young's modulus and elastic modulus are slightly increased at low water concentrations, but once the water content exceeds 5%, they start to drop dramatically. This phenomenon is ascribed to the result of the competition between free water and bound water.

In the daily operation of oil-immersed power transformer, with the increase of temperature, thermal aging happens to the insulation paper, resulting in the decrease of mechanical properties of insulation paper and the decrease of thermal stability. In order to improve the thermal stability of transformer insulation paper, the insulating paper cellulose was grafted and modified by polysiloxane. Then, the differences of elastic modulus, the mean square displacement and the end-to-end distance of cellulose chain before and after the modification were researched through molecular dynamics simulation. Results showed that the elastic modulus of insulation paper cellulose in the modified model was larger than that of unmodified model, and the mechanical properties of modified model were also improved. While, the mean square displacement and the end-to-end distance of cellulose chain of modified model were smaller than those of unmodified model, which means the mechanical properties of modified cellulose were improved. Therefore, it is concluded that using polysiloxane to graft and modify cellulose can improve the thermal stability of cellulose insulation paper.

Energy harvesting from human body itself (i.e. wearable energy harvesters) is a promising approach to respond the rapid-growth energy demand of wearable electronics. In order to make an impact in practical applications, its further improvement is needed in particular in the choice of biocompatible materials for ultra-flexibility and simple manufacture process for mass-fabrication. Therefore, a novel paper-like piezoelectric energy harvester (PEH) was developed here. The main scientific contribution of this work can be summarized as follows. Firstly, natural cellulose nanofibrils and barium titanate (BTO) nanoparticles were successfully combined to realize piezoelectric composite films. Secondly, a printing fabrication process based on roll-coating and screen-printing were proposed, which is simple, high-throughput, and cost-effective. Finally, it was demonstrated that this paper-like ultra-flexible energy harvester is effective to collect omnidirectional bio-mechanical energy from human body motion.

This study introduces a novel and rapid digital fabrication technique for transferring metals on flexible substrates such as cloth, paper, and thermo-resistant films, and demonstrates a low-cost method for prototyping and producing micro/nano flexible sensors and devices. A set of office equipment such as a laser jet printer, a thermal laminator, a craft cutting machine, and inexpensive copper leaf sheets (for furniture restoration) is used for this technique. The proposed method takes advantage of the strong adhesion property of the laser jet toner particles on printed patterns under heating. The applications have been demonstrated for the detection and remediation of heavy metal contaminants in water with devices made on paper and cloth, respectively.

This paper reports a highly sensitive nitrogen dioxide (NO 2 ) sensor based on two-dimensional (2D) tungsten diselenide (WSe 2 ) nanolayers. The WSe 2 nanolayers are integrated on a paper substrate by abrasion from their bulk form, which can be rapidly and cost-effectively completed. The 2D WSe 2 shows a high sensing response of ~1000% toward 10 ppm NO 2 exposure in air at room temperature, and at the same time, the paper substrate provides a high flexibility. The sensitivity of WSe 2 -based sensor reaches to ~238.35% ppm-1 at low concentration of NO 2 from 0.1 to 0.5 ppm. Our approach would be useful for constructing 2D nanomaterial-based highly sensitive gas sensor that can be fabricated by low-cost.

Growing demand for wearable and disposable electronics leads to a need for cost effective and compact sensor designs and fabrication. Most of the devices are multi-layered and require a carrier substrate to hold the sensors. Paper substrates have gained attention since they have the potential to act as both the sensor and the substrate itself. Paper-based printed sensors have been demonstrated and shown functional. However, device fabrication on paper is challenging because of the surface roughness, bleeding, and incompatibility with high temperature sintering processes needed to achieve high conductivity. The conductivity of the interconnects is therefore usually relatively low and imposes performance limitations. Here we report, for the first time, highly conductive silver nano-particle interconnects printed on a paper substrate and sintered with a continuous wave laser. The printing process was identified and the laser sintering parameters were optimized to achieve a conductivity of approximately 67% of the bulk material. As an example of application, interdigitated electrodes were printed and laser sintered. The leakage current was monitored while aging at 50°C /85% RH conditions and exposing to water and artificial sweat.

A paper-based, disposable strain sensor by means of a direct laser printing process with high sensitivity has been developed and demonstrated. Commercially-available printing papers are first soaked with the gelatin-Mo5+ ink and ablated by a CO 2 laser to convert molybdenum ions into conductive MoC and graphene nanocomposite flakes for disposable paper electronics. The strain sensor made of continuous MoC flakes has the capability of detecting and distinguishing both tensile and compressive strain. It is found that the stability of the sensor is preserved when there are defects in the device as well as in environments with heavy humidity for potential applications in wearable devices.

This paper presents a $\mathrm{WS}_{2}$ - functionalized carbon nanotube (CNT)-based sensitive, foldable, and twistable NO 2 sensor that is integrated on cellulose paper. The CNTs form percolation network on the surface of cellulose paper with NO 2 reactivity. Functionalization of CNTs with nanolayers of $\mathrm{WS}_{2}$ significantly improves the response over 200% under 10 ppm NO 2 exposure. At the same time, the cellulose paper offers a high foldability and twistability needed for robust flexible sensors. All these characteristics could enable the stable and sensitive NO 2 detection even under heavy deformation as confirmed by bending down to 0.85 mm and twisting up to 1080°.

A low-cost and simple approach involving soaking and electrochemical deposition is employed to deposit carbon nanotubes (CNTs) and Ni-Co-S (NCS) on papers to prepare paper-based electrodes for flexible solid-state symmetric supercapacitors. The as-prepared Paper-CNTs-NCS electrode shows excellent electrochemical performance such as high areal capacitance and good rate capability. In addition, the electrode possesses good mechanical stability even after bending for 100 cycles. The symmetric supercapacitor (SC) based on the NCS-CNTs paper electrode is fabricated and exhibits a maximum energy density of 4.2 mWh Wh/m2 and power density of 1.26 W/m2.

In order to investigate the insulation characteristics of AC oil-impregnated paper bushing during its operation, the electrical-thermal combined test platform was established to carry out the insulation characteristics tests under different oil temperature condition and different load condition. The change law of dielectric loss factor, capacitance, insulation resistance and frequency domain dielectric spectrum for AC oil-impregnated paper bushing under different oil temperature and different load conditions were mastered and the mechanism of the change law for these parameters were analyzed systematically based on the dielectric polarization theory as well. The results showed that the change of transformer oil temperature will lead to the regular change of insulation performance parameters of AC oil-impregnated paper bushing. The influence of different loads on the insulation performance of the bushing was mainly concentrated on the thermal effect, and the change of load would be finally reflected by the change of the internal temperature of the bushing. With the same oil temperature, when the bushing, which was applied with voltage and current simultaneously, was under the different load condition, it had worse insulation performance than the one with single assessment factor. Therefore, it can be more accurate to grasp the insulation characteristics of the bushing when insulation characteristics tests with electrical-thermal combined effect were taken, and will provide a strong support for the evaluation and diagnosis of bushing as well.

Cellulose is the Earth's major biopolymer and it is of tremendous global economic importance, especially in Europe representing 30% of the world's total production. Nevertheless the use of paper can be expanded tremendously if electronic, sensor and display applications could also be applied on it and by it. Some promising applications have been already demonstrated, like solar cells, displays, capacitors, actuators, gas sensors, magnetic devices, biosensors, food packaging and batteries [1]–[6].

With the rapid development of portable electronics, such as e-paper and other flexible devices, power sources with a high flexibility become an important prerequisite. In this run, supercapacitors with a small form factor are recently emerging as a competitive candidate. Here, we introduce an all-printed paper based supercapacitor (PPS) assembled by screen printing and stencil printing technology, which shows superior electrochemical performance; moreover, it is compatible with mass production processes. The key electrode material, δ-MnO 2 nanosheets, synthesized by one-step synthetic process exhibit a high specific capacitance of 120 F g−1. Using this δ-MnO 2 nanosheets electrode material and aqueous electrolyte, the capacity of the device could reach 4.7 mF g−1 with the volume of 2.0*1.7*0.2mm3. More important, the supercapacitor is lightweight and miniaturized, which can well cater to the development of future wearable electronics.

Ultrasonic welding of carbon paper and proton exchange membrane (PEM) for membrane exchange assemblies (MEAs) of fuel cells (FCs) is a viable technology to replace hot-pressing, which may be time consuming and energy inefficient. Ultrasonic spot welding of carbon paper and PEM is investigated in order to understand the bonding mechanisms and obtain the suitable processing parameters. Micrographs of the tested specimens are examined to evaluate the welding quality. Effects of the welding time on the quality of the ultrasonic welds of the MEAs are studied. It is found that joints made by ultrasonic welding has the strength comparable to that of the base material. Values of welding time, holding time and downward force for successful bonding in terms of mechanical strength are obtained.

We report a laser-ablation aided, direct-write fabrication technique that could convert non-conductive paper rinsed with metal ions and polymer solution into conductive metal carbide and graphene with a typical sheet resistance of 45.3 Ω/□. As fabricated paper electronics inherit the microfiber network from paper and have nanoscale pores and 2D metal carbide flakes due to the laser ablation process. This conducive porous structure could be potentially utilized for sensor and capacitor applications, which usually need large specific area. As preliminary demonstrations, we show a wireless moisture sensor and a supercapacitor fabricated with this foldable paper based electronics. Experimentally, the moisture changes are successfully detected in ambient environment by a paper-based moisture sensor and the paper-based supercapacitor has a measured capacitance of 1.2 mF/cm2. As such, this laser converted paper electronics could be useful for multiple applications such as sensors and energy storage devices.

There has been an increasing need of technologies to manufacturing chemical and biological sensors for various applications ranging from environmental monitoring to human health monitoring. Currently, manufacturing of most chemical and biological sensors relies on a variety of standard microfabrication techniques, such as physical vapor deposition and photolithography, and materials such as metals and semiconductors. Though functional, they are hampered by high cost materials, rigid substrates, and limited surface area. Paper based sensors offer an intriguing alternative that is low cost, mechanically flexible, has the inherent ability to filter and separate analytes, and offers a high surface area, permeable framework advantageous to liquid and vapor sensing. However, a major drawback is that standard microfabrication techniques cannot be used in paper sensor fabrication. To fabricate sensors on paper, low temperature additive techniques must be used, which will require new manufacturing processes and advanced functional materials. In this work, we focus on using aerosol jet printing as a highresolution additive process for the deposition of ink materials to be used in paper-based sensors. This technique can use a wide variety of materials with different viscosities, including materials with high porosity and particles inherent to paper. One area of our efforts involves creating interdigitated microelectrodes on paper in a one-step process using commercially available silver nanoparticle and carbon black based conductive inks. Another area involves use of specialized filter papers as substrates, such as multi-layered fibrous membrane paper consisting of a poly(acrylonitrile) nanofibrous layer and a nonwoven poly(ethylene terephthalate) layer. The poly(acrylonitrile) nanofibrous layer are dense and smooth enough to allow for high resolution aerosol jet printing. With additively fabricated electrodes on the paper, molecularly-functionalized metal nanoparticles are deposited by molecularly-mediated assembling, drop casting, and printing (sensing and electrode materials), allowing full functionalization of the paper, and producing sensor devices with high surface area. These sensors, depending on the electrode configuration, are used for detection of chemical and biological species in vapor phase, such as water vapor and volatile organic compounds, making them applicable to human performance monitoring. These paper based sensors are shown to display an enhancement in sensitivity, as compared to control devices fabricated on non-porous polyimide substrates. These results have demonstrated the feasibility of paper-based printed devices towards manufacturing of a fully wearable, highly-sensitive, and wireless human performance monitor coupled to flexible electronics with the capability to communicate wirelessly to a smartphone or other electronics for data logging and analysis.

Solution-processing has gained widespread attention over the past years due to their potential low-cost advantage in terms of fabrication of electronics as well as application to flexible electronics. Cyclopentasilane is used for the solution-based processing of silicon. As a liquid, the material has the potential to be applied directly on low-cost flexible substrates that generally have a low thermal budget, by annealing the liquid using an excimer laser treatment. So far, electronics based on this material have only been demonstrated on rigid and high cost substrates. In this work, silicon has been applied as a solution on top of a paper substrate and processed into PMOS and NMOS thin-film transistors (TFTs). The maximum fabrication temperature was limited to approximately 100° C. By being able to fabricate devices on top of a paper substrate, a pathway opens towards new applications that combine the true low-cost and biodegradability with the high performance of silicon electronics.

In this work, we report paper-based microbial fuel cells (MFCs) that produce high power and current densities from one drop of bacteria-containing liquid. The devices feature (i) a simple and versatile fabrication technique by using paper as a substrate and (ii) an exceptional performance by incorporating novel nanostructured polymers, PAA-Poly (amic) acid) and PPDD-Poly(pyromellitic dianhydride-p-phenylene diamine), into the paper substrate. Four 3-D MFC configurations were designed by using different numbers of 2-D sheets of paper layers. Each device integrated four functional compartments (i.e. anode, reservoir, proton exchange membrane, and air-cathode) into one, two, three or four paper layers, respectively. The nanostructured polymers were engineered as a proton exchange membrane to enhance ion traveling efficiency or an oxygen mitigating layer to prevent diverting electrons away from the anode. Among the four MFC devices with different numbers of layers, two-layer paper-based MFC generated the highest current density of 47|UA/cm2 and power density of 4|UW/cm2, both of which are substantially greater than achieved by previous paper-based MFCs and even comparable to that of conventional micro-sale counterparts.

Nanocarbon materials made from graphite are used in diverse applications as semiconductors, fuel cells, optical devices, and structural materials because of their excellent mechanical, electrical, and thermal characteristics. Numerous papers are published annually in this area, and thus it is difficult to assess overall development in the field. Consequently, there is a need for approaches that predict advances from diverse and numerous sources of information. In this study, we used machine learning to examine papers on nanocarbon materials and related topics and to predict papers with emerging ideas that are expected to grow in popularity. We specifically predicted emerging papers that were ranked in the top 5% by number of citations. A total of 411,084 related papers were extracted from the Web of Science Core Collection (Thomson Reuters). A time-expanded network was produced from these data using citation links, and features of each paper were used as explanatory variables to build a prediction model. In this model, 9 of the top 10 papers from 2011 predicted to be emerging satisfied the conditions for emerging papers. These results suggest that the model can predict the direction of nanocarbon materials technology, which is of considerable value for private companies and research institutions.

In this paper, we present a novel compressible solid-state supercapacitor with PVA/H 3 PO 4 solid-state electrolyte and folded carbon-nanotube (CNT)/paper electrode. In this structure, both of the compression tolerance of folding structure and the strain capability of CNT film contribute to achieve high compression-tolerant abilities of the electrode, which can be widely used in various environments. This solid-state supercapacitor has achieved the specific capacitance to 11.07 mF/cm2, and capacitance retention retains more than 90% after 100 cycling tests. In addition, the performance of this supercapacitor is very stable even when it is compressed under 50% strain, which enlightens a broad field of compressible energy storage devices to be compatible with high compression-tolerant electronics and flexible self-powered systems.

In this paper, a flexible supercapacitor electrode with high electrochemical performance was fabricated via a electroless plating-electrodeposition combined method which was facile and efficient. The low-cost and available cellulose paper (CP) was employed as flexible substrate loaded highly conductive current collect materials and electrochemical active materials. Results indicate that the as-fabricated electrode is sandwich-structured and flexible and the electrode itself is easy to be bended, twisted and rolled. The electrochemical data showed that the as-fabricated composite electrode displays excellent areal specific capacitance (2485 mF/cm2 at scan rate of 5 mV/s) and the series resistance of the electrode was about 2.2 Ω, which is relatively low enough to be used.

We present a novel triboelectric nanogenerator (TENG) based on a paper-Teflon configuration fabricated by an easy and cost-efficient process. Carbon electrodes were hand-drawn by means of a graphite pencil on commercial paper cards, and the conductivity was confirmed by multimeter. In order to increase the effective triboelectric area, we used sandpaper imprinting to increase the surface roughness more than 2-fold compared to flat surfaces yielding a more than 6-fold enhancement of power density. The achieved output voltage, current and power density were ∼55 V, ∼2.5 μA and ∼17 μW/cm2, respectively. The arch-shaped TENG shows robust output power when pressed by fingers to power a 2-bit liquid crystal display (LCD) demonstrating its use as energy harvester based on low-cost, commodity materials such as paper, Teflon and graphite.

A homogeneous film of acid functionalized Carbon Nanotubes was deposited on the paper substrate using Langmuir-Blodgett technique. The palladium nanoparticles were dropped on the nanotubes network afterword for device enhancement. The sensitivity of the device towards hydrogen gas was tested at three temperatures; room temperature, 200 °C and 300 °C in atmospheric conditions. The results show that CNT network with Pd decorated has high sensing response up to 22 % recorded at room temperature.

Heat generated by electronic devices and circuitry must be dissipated to improve their performance, reliability and prevent the premature failure. One of important methods is to fabricate composites with high thermal conductivity. In this study, we develop a novel approach for surface modification of boron nitride nanosheets and silicon nanowires by being decorated with silver nanoparticles. The resultant composite paper possesses a high through-plane thermal conductivity up to 1.80 W m−1K−1. This attributes to the fact that the silver nanoparticles efficiently links the assembled boron nitride nanosheets and silicon carbide nanowires, which results in formation of more thermally conductive pathways. This work offers a new insight into the strategies for the enhancement of thermal conductivity of polymer-based composites, for the widely identified and pursued potential applications in modern electronics.

Manipulating the particles' movement within the micro-cavity has created a new category of reflective display, termed “Electro-Phoretic Display, (EPD).” The superior performances of EPD under sunlight ambience and the capability of fabricated with roll-to-roll process has make it as a very unique and critical technology. This paper intends to discuss the intriguing physics of how particles being charged, bistable, and operated for EPD applications; meanwhile, discussing the strategies for achieving full-color.

With the wide application of vegetable insulating oil in power transformers, it is essential to investigate the influence of moisture on the frequency domain dielectric spectrum (FDS) analysis in order to propose an accurate moisture assessment method for vegetable oil-paper insulation system. In this regard, various vegetable oil-paper samples are prepared in a laboratory environment. FDS curves for all samples are obtained at different moisture contents and operating temperatures. A new method to estimate the moisture content in insulation paper is proposed based on the low-frequency characteristic quantity. Also, the effect of operating temperature and water migration between the oil and paper insulation on the FDS analysis is investigated. Based on this analysis, a compensation factor is introduced to eliminate the influence of temperature on paper moisture assessment. Furthermore, an improved normalization method for the temperature effect on the FDS of vegetable oil-paper insulation with different moisture contents is proposed. The proposed moisture assessment and temperature normalization methods are validated thorough their application on an operating power transformer.

International audience; This paper investigated the thermal behavior of biomass, coal, municipal solid waste (MSW) and their 50/50 in weight % mixtures using thermogravimetric analysis. The thermo-kinetic behavior was modeled using Coats and Redfern method. In fact, this work presented a complementary study between single and multiple steps process to determine the activation energy (Ea). Thus, Ea values were in average 21, 18 and 40 kJ/mol for biomass, coal and MSW respectively and showed a significant synergism effect between experimental and theoretical data.

Atomic force microscopy (AFM) is a powerful tool to visualize biological molecules at nm resolution in liquid conditions and thus has been applied to a wide variety of biological molecules. One of the most coveted functions of AFM is “fast recording” because it should allow us to directly visualize dynamic processes of biological molecules at work. We have been challenging to break this limitation over 15 years and established fast imaging of dynamic molecular processes. The most advanced high-speed AFM can now capture successive images at 30–60 ms/frame. Further, the interaction force between the tip and the sample, which significantly influences on soft biological molecules, is greatly reduced without deterioration of the scanning performance. In this short paper, typical applications of HS-AFM on biological and artificial molecules will be demonstrated.

Mineral insulation oils have been used as a liquid insulation in electrical equipment for several decades. However, mineral oil is non-biodegradable and non-renewable. It has been predicted that they may run out in the near future. There is thus an urgent need to find their alternatives. Natural, plant based insulating oils are the solution. They are non-toxic, and possess higher fire points and excellent biodegradability characteristics. Therefore, to improve fire safety of transformers and to decrease the harmful environmental impact, there is an increasing demand for these insulating liquids as transformer insulating oils. Persea americana ester (PAE), a plant based oil has high biodegradability and is renewable. PAE has shown through experiments, a likelihood of being an alternative to mineral insulation oil (MIO) because of its good physico-chemical and electrical properties, so far investigated. Since insulating oil for transformers is used over several years, it is imperative to study the ageing characteristics of proposed new insulation oils. Accelerated ageing using open beaker method with copper catalyst was carried out to predict the reliability of Persea americana oil when in operation. The ageing test was based on accelerated thermal ageing to induce the ageing mechanisms within a short period (96 and 164 hours). Results obtained for Specific Resistivity at 27°C and 90°C, Dielectric dissipation factor, Total acidity and sludge for PAE; suggest that PAE could be a potential transformer insulating liquid. For comparison, the corresponding properties of mineral insulation oil (MIO) in the same experimental conditions were also measured. The results obtained as per the IEC and ASTM specifications gives hope for new natural liquid insulation oil.

Oil-impregnated paper is generally used as insulation material in power transformer, which consists of transformer oil and insulating paper (pressboard). And the pressboard made of cellulose is one of important components in transformer insulating system. Oil-impregnated pressboard stays in the environment with high temperature during normal operation of transformer. It is generally recognized that the hot-spot temperature may be the chief factor determining the lifespan of transformer. Furthermore, the inner temperature of transformer will also influence both electrical and mechanical performances of oil- impregnated pressboard. In this paper, the micro surface appearance and mechanical strength of insulating pressboard under different aging time are studied. The sample preparation includes the following steps: vacuum drying for pressboard and transformer oil, impregnating pressboard with transformer oil, and taking oil-impregnated pressboard into vacuum drying oven for thermal aging. When the aging time of oil-immersed pressboard reaches 100h, 200h, 400h and 800h, the pressboard will be taken out of the oven as specimens respectively. After all the specimens under different aging time are obtained, the micro surface appearance of them was observed by scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). Then the tensile strength of them was tested by tensile strength tester. The results indicate that long cellulose chain in the surface of pressboard is broken into the shorter one or shed directly with the aging time becoming longer, meanwhile the mechanical strength of pressboard becomes weaker.

Cu is commonly used as filling material for TSV in 3D integration [1]. However, there is a problem of thermal mismatch between Cu and Si, and also there is still space for improvement in electrical resistivity. In order to improve the physical properties of TSV electroplating copper, we added high conductivity and low expansion coefficient nanoparticles such as graphene to the copper plating solution. Composite electrodeposition is a convenient method of nano-powders composite coating, so we adopt the method of composite electrodeposition for copper and graphene composite materials. Copper and graphene composite electrodeposition has not been researched particularly. In this paper, we discuss a composite electrodeposition method of copper and graphene and evaluate the physical properties of the composite coatings. Firstly does the graphene dispersion, and under the condition we research the feasibility of copper and graphene composite electrodeposition. And graphene composite samples are obtained. Secondly we test the growth rate and electrical characteristics, and get the growth rate curve and the resistivity of composite material, and compare the result with pure copper material. The result shows that copper and graphene composite electrodeposition is feasible, and the electrical properties of composite samples is a little better than pure copper material sample. It has proved that it has a good application prospect in electrical performance.

Field-effect transistors with graphene (GFETs) as the conducting channels are under investigation as promising chemical and biological sensors. In order for graphene to fulfill this promise and become a material for the large-scale manufacture of high-performance electronics, large-area, high-quality graphene on substrates amenable to electrical device operation and sensors fabrication is needed. So the purpose of this paper is to provide in detail how reduced graphene oxide suspension (100 µ g RGO/ 1ml NMP) was developed, and functionalized the back gate FETs. Following an introduction, we report a solution-based method that allows uniform and controllable deposition of reduced graphene oxide thin films ranging from a single monolayer to several layers in thicknesses between the electrodes in FET. The Raman spectrum of graphene consists of a number of peaks which are well characterized and understood. Electrical transfer property tests revealed that both of the two FETs exhibit V-shaped ambipolar field effect behavior from p-type region to n-type region. This research investigared the preparation of back gate field effect transistor with reduced graphene oxide via a low-cost manufacturing method. The reasults suggest that our method is fast, facile, and substrate independent.

Rice straw is the largest residue of Sri Lankan paddy cultivation which has not yet subjected to an effective value addition. But, rice straw can be converted to a high value product as it contains significant amount of Cellulose. Therefore, it is beneficial in many aspects to identify rice straw varieties which provide a sufficient cellulose yield. This research work focuses on introducing a novel, easy to use method based on Thermogravimetric Analysis to predict cellulose yield from most abundant traditional (Suwandel, Raththal) and technically modified (BG300, BG352) rice straw varieties in Sri Lanka. The above method was validated by comparing the results with the yields from established three-step wet chemical method. Proposed method showed a high level of accuracy as percentage variations were less than 5% for all four varieties. Highest cellulose yield was obtained from the rice straws of Suwandel variety. This study reveals a potentially effective course of value addition for Sri Lankan agricultural waste.

In this paper, nickel oxide/graphene aerogel composites (NiO/GA) have been synthesized by a simple solvothermal route starting with graphene oxide (GO). The morphology, composition and microstructure of the as-obtained samples are systematically characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Moreover, the electrochemical performances of composites were evaluated by cyclic voltammogram (CV) and galvanostatic charge-discharge. The nickel oxide was electrochemically deposited into the highly porous GA to form NiO/GA composites. NiO/GA electrodes exhibit excellent electrochemical performance with a maximum specific capacitance of 489.9 F g−1 at the charge/discharge current density of 1 A g−1 in 2 M KOH electrolyte.

Graphene oxide (GO) films are fabricated by direct evaporation of GO suspension on Cu foils under mild heating, and ultrathin paper-like reduced graphene films are produced by reducing graphene oxide films on Cu foils in H 2 -containing atmosphere at different temperature. Further investigation demonstrates that the reduced graphene film with ∼15um in thickness not only possesses high electrical conductivity of ∼ 2.0 * 104 S/m, but also high in-plane thermal conductivity of ∼ 1200W m−1 K−1.

Graphene, a single layer of carbon atoms in a two-dimensional honeycomb lattice, have attracted tremendous attention from researchers in recent years, due to its excellent electrical, mechanical and optical performances. However, preparation of grapheme with simple methods is still a huge challenge. In this paper, graphene oxide is prepared by Hummers method. The graphene prepared by hydrazine hydrate chemical reduction of graphite oxide are characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy. Additionally, the electrochemical performance is tested. Results show that the prepared graphene has good performance and safe manufacturing process.

High sensitive NO2 sensors working at different temperatures using sulfur doped graphene were announced in this paper. The graphene was doped by introducing hydrogen sulfide gas flow as sulfur source at 1000°C in CVD after its transfer on a Si substrate with 300 nm thick SiO2 layer through PMMA coating method. The sensitivity of our S-doped graphene (SG) sensors varied with temperature from 70°C to 150°C. Although the sensitivity was not the best at 150°C, it still distinguished itself with shortest recovery time and the estimated detection limit of 50 ppb, which revealing a potential use in further detection of NO2 with low cost and high sensitivity.

In this paper, we report a novel water transfer printing method, which can transfer chemical vapor deposition (CVD) graphene from copper foil to 3D surface. By the aid of surface tension and Van der Waals force, multilayer graphene film can be transferred to various substrates with smooth surface including glass sheet, colophony filament, silicon oxide micro structure, polyimide (PI) film, polymethyl methacrylate (PMMA) tube and optical fibers. As the graphene film can be selectively transferred to assigned position in 3D surface, this simple room temperature transfer method has promising application potential in flexible MEMS and device on curved surface.

In this paper we report a novel transfer-free graphene fabrication process, which does not damage the graphene layer. Uniform graphene layers on 4 silicon wafers were deposited by chemical vapor deposition using the CMOS compatible Mo catalyst. Removal of the Mo layer after graphene deposition results in a transfer-free and controlled placement of the graphene on the underlying SiO2. Moreover, pre-patterning the Mo layer allows customizable graphene geometries to be directly obtained, something that has never been achieved before. This process is extremely suitable for the large-scale fabrication of MEMS/NEMS sensors, especially those benefitting from specific properties of graphene, such as gas sensing. © 2016 IEEE.

This paper reports a novel nanostructure sensor array combining with back-propagation (BP) neural network toward multi-component gases detection. Tin dioxide and copper oxide modified reduced oxide graphene (rGO) were used as sensing materials toward ammonia and formaldehyde. The sensor array was fabricated via a facile hydrothermal route and layer-by-layer self-assembly method on the substrate with interdigital electrodes (IDEs). And furthermore, this work successfully achieves the recognition and prediction of components in the gas mixture of ammonia and formaldehyde through the combination of graphene-based high-performance sensor array and neural network-based signal processing technologies.

We have demonstrated a new composite thin film for encapsulation consisting of polydimethylsiloxane (PDMS) and graphene. Graphene is a kind of hydrophobic material, causing that moisture could hardly penetrate into the surface of graphene. Graphene is usually fabricated by the method of Chemical Vapor Deposition (CVD). The atomic distance of graphene is very small; thus the water vapor channel from one layer to the nearby layer has been cut off, achieving the barrier of oxygen, water vapor and particle. Graphene and PDMS have high transmittance, making this method be widely used in various photoelectric devices. Meanwhile, graphene owes excellent heat dissipation which can reduce the temperature gradient and the junction temperature, thus improves the comprehensive performance and reliability of the device. Furthermore, PDMS has a good cohesiveness property, by which fit graphene very well and meet the requirement of encapsulation at the same time. Using Ca film test, we have found that the composite thin film has the greatest water oxygen barrier effect among them.

Heterostructures of carbon nanotube on graphene, CNT-graphene, with two graphene layers connected by a CNT normal to the graphene planes, are investigated using first-principle calculations, leading to computed density of states (DOS) and electron transmission spectra. Based on these results, the structure consisting of graphene and a (4,4) CNT is determined to be metallic while that of graphene and (8,0) CNT semiconducting. Multiple peaks are observed in the transmission spectrum of both heterostructures, which depend on the width of graphene. Further, it is found that the heterostructures are three-dimensional thermal conductors, although the resistance is higher than that of pure graphene or CNT. These results lay the foundation for further studies of CNT-graphene as a potential all-carbon interconnect building block.

We report the results of investigations of thin films of the composite based on the semiconducting polymer polyfluorene and graphene oxide particles with different content of the graphene oxide by terahertz time-domain spectroscopy.