Graphite Polymer Research Articles

Performance investigation of variant polymer graphite electrodes used in electrochemical micromachining of ASTM A240 grade 304

ABSTRACTIn this paper, experiments in Electrochemical Micromachining (ECMM) were conducted to produce micro-holes of high aspect ratio using a cathode ‘Polymer Graphite Electrode’ (PGE). The effect of electrochemical dissolution of ASTM A240 type 304 stainless steel is comparatively studied using cryogenically treated PGE (CTPGE) tool and non-treated PGE tool (NTPGE) that owes to enhance the overall quality of micro-hole produced, which is assessed on the basis of the most imperative output responses namely the material removal rate (MRR), and the Overcut (Oc) in relation to the predominant input process parameters namely, Voltage (S1), Electrolytic concentration (S2) and the Duty cycle (S3). Response surface modeling based on Box-Behnken (BB) DoE was used to obtain the corresponding responses for the process factors. Numerical models were developed to study and effects of process factors individually and their interactional effect. ANOVA was used to study the statistical significant process factors. The outcome of the multi-objective optimization based on cuckoo search algorithm (MOCS) was found to be enhanced, owing to better surface characteristics of the workpiece machined using the CTPGE tool. The effect of the micro spark and stray current have dwindled when using CTPGE electrode that can be visually seen via SEM.

Development of additively manufacturable and electrically conductive graphite–polymer composites

The selectivity between electrically conductive and insulating regions within one additively manufactured part can open new domains for customized, smart, and active products. In this article, new electrically conductive polymer matrix composites (ePMC) were developed for additive manufacturing (AM) by loading an aqueous matrix of carboxymethyl cellulose with micro-sized graphite particles. Electrically conductive AM can be achieved using the developed ePMC with the direct ink writing (DIW) technique. The effects of graphite loading on the properties of ePMCs and their suitability for AM were investigated using various characterization techniques. The non-Newtonian shear-thinning behavior of the ePMC inks indicates the suitability of these inks for DIW. Tunable electrical conductivity in the range of 87–128 S m−1 can be achieved with a 15% margin of error. DIW of scaffolds with rectilinear and honeycomb infill patterns demonstrate the additive manufacturability of the developed ePMCs. Furthermore, an application of additively manufactured and electrically conductive part as a heating element was demonstrated. The developed ePMCs can be employed in diverse applications such as AM of conductive tracks, resistors, and electrodes for capacitors and energy storage devices.

Nitrogen‐doped graphene prepared by thermal annealing of fluorinated graphene oxide as supercapacitor electrode

AbstractBACKGROUNDNitrogen doping significantly improves the electrochemical properties of graphene. Here, a new and effective methodology of preparing nitrogen‐doped graphene (NG) by thermal annealing of fluorinated graphene oxide (FGO) under the atmosphere of ammonia, is reported, in which ammonia is the reductant for FGO reduction and also the nitrogen source for nitrogen doping. This method can achieve higher nitrogen doping content than conventional approaches.RESULTSFGO prepared from fluorinated graphite polymer (CF) is directly used as a precursor to synthesize NG. Four samples with the same reaction time and different annealing temperatures are compared, and the highest nitrogen content of the NG reaches 12.45 at% at the reaction condition of 800 °C and 3 h. The synthesized NG samples are examined as a supercapacitor electrode material, displaying excellent performance due to the high nitrogen doping and a large number of active sites.CONCLUSIONWith the increase of annealing temperature, the nitrogen content of different NG samples first increases and then decreases. The specific capacitance of NG electrode material also shows the same trend as the nitrogen content. The highest specific capacitance in three‐electrode configuration attains 225.2 F g−1 at a current density of 1 A g−1. The electrode maintains a 90% capacitance after 5000 cycles, showing good cycle stability. This synthetic method provides a new approach for the preparation of NG with high nitrogen doping as supercapacitor electrode materials. © 2019 Society of Chemical Industry

Multi-response optimization of electrochemical micromachining parameters for SS304 using polymer graphite electrode with NaNO3 electrolyte based on TOPSIS technique

This research experimentally investigates the influence of electrochemical micromachining (ECMM) process parameters of SS304 alloy with “polymer graphite electrode (PGE),” employing sodium nitrate as the electrolyte solution. The machining parameters were considered based on their significance in machining such as machining voltage, duty cycle and electrolyte concentration to assess and evaluate their effect on response parameters such as material removal rate, over cut and taper angle. The experimental results revealed that 23 g/l of electrolyte concentration, machining voltage of 9 V and 55% duty cycle are considered as the optimal parameters for accessing the multi-response characteristics in ECMM process with hole within the aspect ratio 0.8 micron meters. The experimental results indicated that the multi-response characteristics considered in electrochemical micromachining of SS304 alloy are enhanced using TOPSIS optimization methodology. ANOVA is used to analyze the process parameters and to identify the best contributing factor in chosen limited parameters. The results indicated that voltage is the most influencing factor which contributes 52.29%. The research possibilities of using PGE electrode are discovered for electrochemical micromachining.

A Competitive Design and Material Consideration for Fabrication of Polymer Electrolyte Membrane Fuel Cell Bipolar Plates

The bipolar plate is one of the most significant components of a polymer electrolyte membrane (PEM) fuel cell, and contributes substantially to the cost structure and the weight of the stacks. A number of graphite polymer composites with different fabrication techniques have been reported in the literature. Graphite composites show excellent electromechanical properties and chemical stability in acidic environments. Compression and injection molding are the most common manufacturing methods being used for mass production. In this study, a competitive bipolar plate design and fabrication technique is adopted in order to develop a low-cost and light-weight expanded graphite (EG) polymer composite bipolar plate for an air-breathing PEM fuel cell. Cutting molds are designed to cut fuel flow channels on thin expanded graphite (EG) sheets (0.6 mm thickness). Three separate sheets, with the flow channel textures removed, are glued to each other by a commercial conductive epoxy to build a single bipolar plate. The final product has a density of 1.79 g/cm3. A bipolar plate with a 20 cm2 active area weighs only 11.38 g. The manufacturing cost is estimated to be 7.77 $/kWe, and a total manufacturing time of 2 minutes/plate is achieved with lab-scale fabrication. A flexural strength value of 29 MPa is obtained with the three-point bending method. A total resistance of 22.3 milliohms.cm2 is measured for the three-layer bipolar plate. We presume that the suggested design and fabrication process can be a competitive alternate for the small-scale, as well as mass production of bipolar plates.

Effect of Graphite Loading and Addition of Ferric Chloride (FeCl3) on the Properties of Poly (Vinyl Chloride)/Poly (Ethylene Oxide)/Graphite Polymer Films

In this study, films consisting of a blend of poly (ethylene oxide)/poly (vinyl chloride) (PEO/PVC) and a conductive filler, graphite with the addition of FeCl3 as a doping were prepared and characterized for their mechanical and electrical properties. Solid polymer blend films based on PVC/PEO (50/50 wt%/wt%) with different graphite loading were prepared by using solution casting technique. Electrical conductivity results discovered the conductivity increased with increasing of filler loading and addition of FeCl3. However, the addition of FeCl3 in graphite loading led to a decreased in tensile strength of PEO/PVC/Graphite polymer films. The dispersion of graphite and mechanism of conductive path in the polymer films were also investigated by scanning electron microscopy (SEM). The morphology of the PEO/PVC/Graphite polymer films shows that agglomeration occurred to complete the connection of conductive path, thus improving the conductivity behavior of the polymer films.

Enhancement of Graphite Functionality in Renewable Polymer Composite Properties

The preparation and characterization of composite thin films of renewable polymer graphite (PG) is disclosed. Thin films ~ 0.1 mm thick are prepared using a simple solution mixing with mass proportion of 2/1 (renewable monomer/ Methylene Diphenyl Diisocyanate, MDI), upon differ graphite content (PG0, PG5, PG10, PG15, PG20, PG25 andPG30) and drop casting at room temperature. The morphology-structure relations of renewable PG composites with respect to electrical conductivity were diagnosed using Optical microscope (OM), Fourier transform infra-red spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The homogeneous random dispersion and strong interface between the graphite in the classical insulating renewable polymer matrix were observed. Thus resulting of enhancements in thermal stability with slight shift of decomposition temperature and better mechanical properties through the modulus and tensile strength increment up to ~440% and ~100% respectively. The result shows that it can simultaneously leads to renewable PG conductivity (σ) where the percolation threshold occurs at higher graphite content (PG20, PG25 andPG30) of 103 - 104 S/m. Thus, this non-petroleum based renewable polymer graphite composites have remarkably more to offer as conducting polymer composites material in multidisciplinary applications.

Preparation and noise analysis of polymer graphite cathode

Preparation and noise analysis of polymer graphite cathode

Preparation of Conductive Polymer Graphite (PG) Composites

The preparation of conductive polymer graphite (PG) composites thin film is described. The thickness of the PG composites due to slip casting method was set approximately ~0.1 mm. The optical microscope (OM) and fourier transform infra-red spectroscopy (FTIR) has been operated to distinguish the structure–property relationships scheme of PG composites. It shows that the graphite is homogenously dispersed in polymer matrix composites. The electrical characteristics of the PG composite were measured at room temperature and the electrical conductivity (σ) was discovered with respect of its resistivity (Ω). By achieving conductivity of 103 S/m, it is proven that at certain graphite weight loading (PG20, PG25 and PG30) attributes to electron pathway in PG composites.

Strain Sensors: 3D Graphite–Polymer Flexible Strain Sensors with Ultrasensitivity and Durability for Real‐Time Human Vital Sign Monitoring and Musical Instrument Education (Adv. Mater. Technol. 6/2017)

Strain Sensors: 3D Graphite–Polymer Flexible Strain Sensors with Ultrasensitivity and Durability for Real‐Time Human Vital Sign Monitoring and Musical Instrument Education (Adv. Mater. Technol. 6/2017)

Evaluation of the probability of reaction of fast oxygen atoms with polymers and graphite

On the basis of analysis of published data on the reaction efficiency of various polymer materials and graphite in their interaction with fast oxygen atoms (energy of about 4.5 eV) as obtained in flight tests of materials in low-Earth orbits of the International Space Station and ground tests, probability P r of chemical oxidation reactions accompanied by ablation has been evaluated. Estimates have been made for 33 polymers consisting of carbon, hydrogen, oxygen, and nitrogen and graphite for two extreme cases when the carboncontaining oxidation products are either CO or CO2 alone. The average probability values found are P r(CO)(av) = 0.184 and P r(CO2)(av) = 0.317. The probability values range from P r(CO) = 0.604 and P r(CO2) = 0.963 for allyl diglycol carbonate to P r(CO) = 0.038 and P r(CO2) = 0.075 for pyrolytic graphite.

3D Graphite–Polymer Flexible Strain Sensors with Ultrasensitivity and Durability for Real‐Time Human Vital Sign Monitoring and Musical Instrument Education

The design and fabrication of various types of flexible, portable, and foldable devices have received immense interest owing to the remarkable potential in impacting peoples' lives including real‐time health monitoring, point‐of‐care diagnosis, and athletic training. In this work, the authors present 3D graphite as the key sensing element of polymer composite strain sensors that offers ultrahigh sensitivity and durability in the detection of fine motions. The graphite–polymer sensors in this work provide high bending sensitivities that are reproducible within 3% signal shift after 11 000 bending cycles and exhibit gauge factors of 100 and 52 at tensile strains of 80% and 100%, respectively. The sensing mechanism is modeled, and correlated with experimental studies. The high strain sensitivity compared to graphene based devices is analyzed and understood with respect to levels of defect in materials. Such graphite–polymer sensors are able to detect fine features of human pulses, respiration rates, and throat vibration in real time and are also applied in the detection of posture correctness of musical instrument learners for the first time.

Morphology, flammability, and properties of graphite reinforced polymer composites. Systematic review

Increasing concern for the environment and economy has stimulated interest in the research and development of graphite polymer composites. Graphite is naturally abundant and has significant influence on the thermal conductivity, flammability properties and thermal stability of filled materials. It is frequently used as filler for improvement of most polymer properties. Polymer/graphite composites have long been used in structural, aerospace and sporting goods applications. The importance of thermal conductivity in polymer composites is needed for acceptable levels of thermal conductance in circuit boards, heat exchangers, appliances and machinery. Graphite halogen‐free flame‐retardant materials can be used in the manufacturer of electric engineering materials and electronics, such as the wires and cables. In this review, we focus on graphite and its various modifications on the flammability, thermal conductivity and thermal stability of the composites. POLYM. COMPOS., 39:E1487–E1499, 2018. © 2017 Society of Plastics Engineers

Breaking through the Solid/Liquid Processability Barrier: Thermal Conductivity and Rheology in Hybrid Graphene-Graphite Polymer Composites.

Thermal conductivity (TC) enhancement of an insulating polymer matrix at low filler concentration is possible through the loading of a high aspect ratio, thermally conductive single filler. Unfortunately, the dispersion of high-aspect-ratio particles greatly influences the rheological behavior of the polymer host at relatively low volume fractions, which makes further polymer processing or mixing difficult. A possible remedy is using two (hybrid) fillers, differing in their aspect ratios: (1) a plate-like filler, which sharply increases both viscosity and TC, and (2) an isotropic filler, which gradually increases these properties. We examine this hypothesis in a thermosetting silicone rubber by loading it with different ratios, (1)/(2), of graphene nanoplatelets (GNPs) (1) and graphite powder (2). We constructed a "phase diagram" delineating two composite processability regions: solid-like (moldable) or fluid-like (pourable). This diagram may be employed to tailor the mixture's viscosity to a desired TC value by varying the fillers' volume fraction. The phase diagram highlights the low volume fraction value, above which the composite is solid-like (low processability) for a single high-aspect-ratio nanofiller. By using hybrid filling, one can overcome this limit and prepare a fluid-like composite at a desired TC, not accessible by the single nanofiller. Thus, it provides an indicative tool for polymer processing, especially in applications such as the encapsulation of electronic devices. This approach was demonstrated for a heat source (resistor) potted by silicon rubber graphene-graphite composites, for which a desired TC was obtained in both solid- and liquid-like regions.

Mechanical Behavior of Ultra Violet (UV) Curable Renewable Polymer/Graphite (PG)

The mechanical behaviors of the renewable polymer/graphite (PG) films with prolonged UV irradiation exposure were investigated. Renewable PG films were prepared by mixing with varying weight percent of graphite (neat, 10 wt. %, 20 wt. % and 30 wt. %) and crosslinker. Then, casting film solution on square container and cured upon stimulated ultraviolet (UV) irradiation (UV accelerated weathering tester) at different time exposure (0, 250, 500 and 750 hours) was applied. Based on observations, different UV exposure time yield PG with varying tensile strength, tensile modulus and elongation at break. However, the mechanical behavior of resulting PGs gives plateau series due to chemical crosslink and chain scissions within renewable polymer and graphite that shown in infrared spectra (FTIR) of the films. The system indicates that the mechanical behavior of renewable PG can be tailored based on requirements of an application upon UV treatment.

Experimental investigation on tribological behaviours of PA6, PA6-reinforced Al2 O 3 and PA6-reinforced graphite polymer composites

This article reports on the preparation, characterization and experimental investigation of polyamide 6 (PA6) reinforced with alumina oxide (Al2O3) and graphite composites. The test specimens were prepared in an injection-moulding machine by varying the weight proportions of Al2O3 and graphite particles blended with PA6. The tribological properties of the composites were observed by using pin-on-disc wear test rig under dry sliding conditions. The worn surfaces of the composites were examined using scanning electron microscope. The addition of Al2O3 and graphite significantly enhanced the tribological properties of PA6. The PA6 containing 30 wt% Al2O3 and 20 wt% graphite revealed the best tribological behaviours due to the stronger interfacial bonding characteristics with improved wear resistance. Further, the thermal stability of Al2O3 and graphite particles was studied through thermogravimetric analysis test. It was also found that further addition of Al2O3 and graphite in PA6 had no significant improvement in wear resistance, the co-efficient of friction and heat generation.

Adjusting the thermoelectric properties of copper(I) oxide-graphite-polymer pastes and the applications of such flexible composites.

We present a facile alternative to other well known strategies for synthesizing flexible thermoelectric materials. Instead of printing thin active layers on flexible substrates or doping conductive polymers, we produce thermoelectric pastes, using a mixture of graphite, copper(I) oxide and polychlorotrifluoroethene. The Seebeck coefficient of the investigated pastes varies between 10 and 600 μV K(-1), while the electrical conductivity spans over an even wider range of 10(-4) to 10(2) S m(-1). Here, the influence of phenomena such as percolation on the electrical transport is revealed. The resulting power factor reaches 5.69 × 10(-4) ± 0.70 × 10(-4) μW m(-1) K(-2) for the graphite-polymer paste, with an unexpected minimum at a graphite molar fraction of approximately 0.4. The values are comparable to those of the powder mixtures, which are slightly higher, but less precisely tunable. Such compounds are further evaluated for practical applications. The graphite-polymer paste is used to exemplify, how a flexible thermoelectric sensor can be easily manufactured, step by step. Our results represent a proof of principle, that thermoelectric pastes are viable alternatives to current solutions. A further expansion of the scope for the composites can be achieved by using high performance thermoelectric materials and conductive polymers.

Recovery and utilization of graphite and polymer materials from spent lithium-ion batteries for synthesizing polymer–graphite nanocomposite thin films

The present study focuses on the synthesis of polyethylene (PE), polypropylene (PP) and graphite composite thin film (PE/GRx and PP/GRx) using recovered anode (graphite) and separator (polymers) materials of spent Lithium-ion batteries (LIBs). The synthesized PE/GRx and PP/GRx thin films are characterized by X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry and differential scanning calorimetric analysis. The mechanical and electrical properties of the synthesized PP/GRx and PE/GRx composite thin films have been evaluated. The results demonstrated ∼10 times increase in tensile strength in composite thin films (PP/GR20wt%; 33MPa; PE/GR20wt%; 38MPa) as compared to neat polymer thin film (PP and PE thin film: 3.4 and 3.0MPa). Similarly after graphite loading the specific conductance of composite films is increased 5–6 orders compared to the neat polymer thin film. The synthesis of polymer–graphite composite thin film using recovered materials of spent LIBs may effectively be used as an alternative for commercial graphite and polymer. The recovering of waste may decrease the quantity of the solid waste and reduce the potential pollution to the environment.

Implication of composite electrode on the functioning of photo-bioelectrocatalytic fuel cell operated with heterotrophic-anoxygenic condition

Electrode materials play a vital role in biofilm formation and electron conduction for efficient functioning of fuel cells. In the present study, graphite polymer composite electrode (GPF) was evaluated as anode for photo-bioelectrocatalytic fuel cell (PhFC; biophotovoltaic system) and compared with much studied graphite electrode (Gc) with photosynthetic bacteria as biocatalyst under anoxygenic condition. The electrogenic activity noticed in GPF (584mV; 2.67mA) was slightly lower than Gc (604mV; 2.92mA; OL2/HRT2). Consequently, COD removal observed by GPF (87.3%) was lower than Gc (91.8%). The increase in bacterial chlorophyll pigment showed a positive influence on electrogenic activity for both the electrodes. The polarization resistance (OL2 and HRT2 condition) was significantly higher for GPF (330Ω) as compared to Gc (110Ω). It is interesting to note that the performance of GPF is slightly lower than Gc based PhFC. The findings have opened avenues for composite materials for PhFC.

Explosive Emission Properties of Cathode Materials in Relativistic Electron Beam Generation

Relativistic electron beam generation studies have been carried out in LIA-400 system through explosive electron emission for various cathode materials. This paper presents the emission properties of different cathode materials at peak diode voltages varying from 10 to 220 kV and at peak current levels from 0.5 to 2.2 kA in a single pulse duration of 160-180 ns. The cathode materials used are graphite, stainless steel, and red polymer velvet. The perveance data calculated from experimental waveforms are compared with 1-D Child Langmuir formula to obtain the cathode plasma expansion velocity for various cathode materials. Various diode parameters are subject to shot to shot variation analysis. Velvet cathode proves to be the best electron emitter because of its lower plasma expansion velocity and least shot to shot variability.