Effect of Graphite Filler Type on the Thermal Conductivity and Mechanical Behavior of Polysulfone-Based Composites

Cation Bimetallic MOF Anchored Carbon Fiber for Highly Efficient Microwave Absorption

Carbon fiber (CF) is a potential microwave absorption (MA) material due to the strong dielectric loss. Nevertheless, owing to the high conductivity, poor impedance matching of carbon-based  materials results in limited MA performance. How to solve this problem and achieve excellent MA performance remains a principal challenge. Herein, taking full advantage of CF and excellent impedance matching of bimetallic metal-organic frameworks (MOF) derivatives layer, an excellent microwave absorber based on micron-scale 1D CF and NiCoMOF (CF@NiCoMOF-800) is developed. After adjusting the oxygen vacancies of the bimetallic MOF, the resultant microwave absorber presented excellent MA properties including the minimum reflection loss (RLmin ) of -80.63 dB and wide effective absorption bandwidth (EAB) of 8.01 GHz when its mass percent is only 5 wt.% and the thickness is 2.59 mm. Simultaneously, the mechanical properties of the epoxy resin (EP)-based coating with this microwave absorber are effectively improved. The hardness (H), elastic modulus (E), bending strength, and compressive strength of CF@NiCoMOF-800/EP coating are 334 MPa, 5.56 GPa, 82.2 MPa, and 135.8 MPa, which is 38%, 15%, 106% and 53% higher than EP coating. This work provides a promising solution for carbon materials achieving excellent MA properties and mechanical properties.

Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young's modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10-4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates.

Reinforced Polymer Composites III

The development of modern technology requires the development of new materials with improved operational and technological properties [...].

Multiscale Thermal Investigations of Graphite Doped Polystyrene Thermal Insulation

Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or cooling due to the environment compensation. One way to create this is to reduce the heat loss in buildings. An option to achieve this is the application of thermal insulations. Nowadays, the use of super insulation materials such as aerogel and vacuum insulation panels and other nano-structured insulations, such as graphite doped expanded polystyrene, is becoming increasingly justified. These are relatively new materials, and we know only a little about them. This paper presents research results based on temperature-induced investigations of nanostructured graphite expanded polystyrene, to reveal its thermal stability after long-term and short-term thermal annealing, simulating the ageing of the material. Firstly, with a differential scanning calorimeter, we will explore the thermal stability profile of the specimens. After this, the paper will present temperature-induced changes in both the thermal properties and the structure of the samples. We will also present changes in the thermal conductivity, modifications in the surface, and compressive property variation induced by thermal annealing. The samples were thermal annealed at 70 °C for 6 weeks, at 100 and 110 °C for 1 h. Besides the thermal conductivity measurements with Netzsch 446 heat flow meter equipment, we will present specific heat capacity measurement results executed with the same equipment. Moreover, sorption isotherms of the as-received and annealed samples were registered and completed with hydrophobic experiments, too. Furthermore, from the measurements, we showed that temperature should affect a significant change in the thermal conductivity of materials. Moreover, the changes in the graphite expanded polystyrene before and after thermal annealing were investigated by Scanning Electron Microscopy, as well as optical microscopy. The structural changes were further followed by an X-ray diffractometer and the IR absorption capability was tested, too.

Development of Nanocomposite Materials Based on Conductive Polymers for Using in Glucose Biosensor

Electropolymerized neutral red, thionine, and aniline were used as part of hybrid nanocomposite conductive polymers, to create an amperometric reagent-less biosensor for glucose determination. The structure of the obtained polymers was studied using infrared (IR) spectroscopy and scanning electron microscopy. Electrochemical characteristics were studied by cyclic voltammetry and impedance spectroscopy. It was shown that, from the point of view of both the rate of electron transfer to the electrode, and the rate of interaction with the active center of glucose oxidase (GOx), the most promising is a new nanocomposite based on poly(neutral red) (pNR) and thermally expanded graphite (TEG). The sensor based on the created nanocomposite material is characterized by a sensitivity of 1000 ± 200 nA × dm³/mmol; the lower limit of the determined glucose concentrations is 0.006 mmol/L. The glucose biosensor based on this nanocomposite was characterized by a high correlation (R² = 0.9828) with the results of determining the glucose content in human blood using the standard method. Statistical analysis did not reveal any deviations of the results obtained using this biosensor and the reference method. Therefore, the developed biosensor can be used as an alternative to the standard analysis method and as a prototype for creating sensitive and accurate glucometers, as well as biosensors to assess other metabolites.