Surface Resistance Properties Research Articles

Spray-deposition of graphene/polymer thin coatings on polyimide sheets for lunar dust adhesion mitigation

NASA seeks to develop technologies to mitigate dust accumulation from planetary surfaces on robotic and human systems hardware during planned space exploration missions. With a return to the Lunar surface, lunar dust threatens the durability and reusability of components and vehicles due to its fine, jagged morphology and highly abrasive nature. Lunar dust consists of particles less than 60 μm in size that are chemically reactive, electrostatically and sometimes magnetically charged. Unique materials and technologies that reduce or mitigate lunar dust adhesion will be critical to support long duration missions and eventual sustained presence on the lunar surface. The goal of this work was to prepare dust resistant, space durable polymer films to satisfy dust accumulation mitigation needs for future NASA missions. In this regard, several graphene coated polyimide thin films have been developed with surface resistivity properties in the range of 103 Ω/sq to 1011 Ω/sq and evaluated for their dust adhesion performance. Raman spectroscopy was used to characterize and assess the quality of graphene ink coated sheets while surface resistivity measurements were used to assess electrical conductivity. Scratch testing and abrasion resistance measurements were used to evaluate overall abrasion performance. Water contact angle and optical microscopy were used to evaluate changes in surface topography and chemistry. Graphene coated polyimide surfaces with charge dissipative resistivity (106 Ω/sq) demonstrated a minimum in residual particle areal coverage compared to conductive and insulating surfaces.

Evaluation of Resistance Properties of Selected Surface Treatments on Medium Density Fibreboards

The protection and decorative value of raw wood-based boards with various coatings can be enhanced during the service life of furniture using surface treatment techniques. In this study, selected transparent, pigmented polyurethane email finish and thin foils, commonly used in furniture, were used for surface treatments of medium-density fibreboards with a thickness of 18 mm. Water-borne finish with polyurethane–acrylate resin, solvent-borne finish with polyacrylate resin, and finish based on native oil and waxes, as well as pigmented polyurethane email finish, were used on veneered medium-density fibreboards. The thin foils (polyvinyl chloride, polyethylene terephthalate, and lacquered acryl film) were used for raw medium-density fibreboards. Several resistance surface properties were investigated. It was found that the hardness and resistance to impact were very much related to the interactions between the coating film or thin foil and the substrate. The type of surface finish had a substantial impact on the coating and foil’s resistance qualities, such as resistance to mould and cold liquids.

The Effects of Laser Cladding Surface Treatment on Surface Degradation Properties :a Review

Surface degradation due to hot corrosion and erosion in thermal power plants and gas turbines, is one of the primary concerns for many researchers, scientists and surface engineers. Hot corrosion is considered as a serious problem in coal-based thermal power plants which fulfill approximately 58.3% of the total electricity demand of India. The practice of using low-grade fuels at high functional temperatures is the overriding reason for accelerated hot corrosion. A case study stated that approximately 56% of boiler failures occur due to hot corrosion that may lead to reduced economical efficiency of the thermal power plants. Fortunately, this problem can be controlled by some preventive measures, and surface modification is one of the effective methods to enhance the lifespan of boiler components. Surface modification can be done through different surface coating processes like plasma spray, HVOF and D-gun etc. In this paper, we will discuss the effects of Laser cladding surface coating process to develop the corrosion resistance surface properties of different substrate materials

Poly(vinyl alcohol)/reduced graphene oxide multilayered coatings: The effect of filler content on gas barrier and surface resistivity properties

Polymer-filler multilayered coatings fabricated by layer-by-layer (LbL) methods exhibit enhanced gas barrier properties alongside with transparency and flexibility. However, the traditional LbL methods which consist of repeated cycles of dipping (or spinning), washing, and drying, are time-consuming and complex to industrialize. Here, it is proposed an easy-operating and time-saving rod-coating assisted LbL method for the fabrication of poly(vinyl alcohol)/reduced graphene oxide (PVA/rGO) multilayered coatings on poly(ethylene terephthalate) (PET) substrates. Scanning electron microscopies revealed that PVA/rGO multilayered coatings exhibited a brick-and-wall structure with PVA able to bind the rGO buildings blocks. The oxygen transmission rate of the films coated with five layers of PVA/rGO coatings (8.4 cm3 m-2 day-1 atm-1) is about 92% lower than that of the uncoated PET substrate, whereas the optical transparency is still 94%. The water permeability of films coated with the multi-layered PVA/rGO coatings is about 30% lower than that of pristine PET substrate. Furthermore, the resulting films exhibited a low surface resistivity, which contrasts the negative effects of static electricity accumulation, and high mechanical property, fulfilling the technological requirements for traditional application in electronic packaging.

Quality of Oil- and Wax-Based Surface Finishes on Thermally Modified Oak Wood

In this study, natural linseed oil, hard wax oil, and hard wax, commonly used as finishes for wooden furniture and parquet, were used for surface finishes on Turkey oak wood (Quercus cerris L.), thermally modified at temperatures of 175 °C and 195 °C for 4 h. Several resistance surface properties were investigated. The mechanical resistance properties of all surface finishes were very much allied to interactions between the finish and the type of substrate. The adhesion strength and impact resistance decreased if higher temperature was used for thermal modification of the substrate. The surface hardness and the resistance to abrasion were high and increased slightly with increasing temperature during thermal modification of wood. It was also found that surface adhesion, hardness and resistance to impact were very much related to interactions between the coating film and the substrate. The resistance properties of finishes, such as resistance to cold liquids and mold, were mainly influenced by the type of the surface finish. The resistance to cold liquids increased in the order: surface finish with hard wax < linseed oil < finish system of linseed oil + hard wax oil. The lowest resistance to cold liquids showed up in condensed milk and sanitizer. Resistance to Aspergillus niger and Penicillium purpurogenum was relatively weak, however apparently improved during the first 7 days of the fungal test; the surfaces were covered with a lower distribution density of fungal mycelium after 21 days of the fungal test. Individual surface performances of oil and wax-based surface finishes on native wood were different from thermally modified wood.

Measurement of Surface Resistance Properties with Coaxial Resonators - Review

Measurement of Surface Resistance Properties with Coaxial Resonators - Review

Wicking behavior and antibacterial properties of multifunctional knitted fabrics made from metal commingled yarns

In this study, stainless steel wires (SSWs) were selected as conductive filler to produce antibacterial nylon (AN)/crisscross-section polyester (CSP)/SSW multifunctional metal commingled yarns with hollow spindle spinning technique. All metal commingled yarns used AN and CSP yarns to wind around the SSW in the S- and Z-directions as the outer and inner wrap yarns, respectively. The wrapping density varied from 8.0 to 15.5 turns/cm, which exhibited an obvious influence on the tenacity and elongation of the commingled yarns. Metal composite knitted fabrics made from the commingled yarns were tested in terms of their horizontal wicking capability, drying rate, and surface resistivity properties. Results showed that knitted fabric KC-11 displayed the best horizontal wicking capability, drying rate, and surface resistivity values. To evaluate the effect of the layer number of knitted fabrics on comfort, the air permeability of the fabric KC-11 was also discussed. The air permeability decreased from 421.6 to 140 cm3/cm2/s, when the layer number increased from one layer to six layers. The antibacterial activity of the KC-11 sample was assessed against Staphylococcus aureus and Escherichia coli bacteria according to the AATCC 90-2011 standard method. The presence of the AN yarns in the metal composite knitted fabrics displayed an obvious inhibition zone for both types of bacteria, which can be attributed to the high antibacterial activity of organosilicon quaternary ammonium salt component.

Influence of atomic oxygen exposure on surface resistivity of silicon doped polyimide affecting spacecraft charging

In the present research work, the vulnerability of silicon doped polyimide by atomic oxygen present in LEO (lower earth orbit) of space was investigated. AO-exposure of a fluence of 5.4 × 1018 atoms cm−2 significantly changed the surface resistivity properties of polyimide which is a prime factor governing spacecraft surface charging problem. This amount of fluence affected surface morphology and eroded the surface thickness as observed by SEM (scanning electron microscopy), laser beam imaging and surface profilometer study. This much exposure also increased the oxygen and silicon content on the surface as observed by XPS (X-ray photoelectron spectroscopy) and EDX (Energy-dispersive X-ray spectroscopy) study.

Effect of Mechanical Treatment Temperature on Electrical Properties and Crystallite Size of PVDF Film

Fabrication of PVDF films has been making using Hot Roll Press. Preparation of samples carried out for nine different temperatures. This condition is carried out to see the effect of temperature fabrication on electrical properties and crystallite size of PVDF films. The electrical properties like as surface resistivity are discussion focus in this paper. Surface resistivity properties of PVDF can be improved by mechanical treatment on the varying film thickness and the temperature. To obtain the diffraction pattern of sample characterization is performed using X-Ray Diffraction. Crystallite size of PVDF films calculate from broadening pattern of X-Ray Diffraction. Furthermore, from the diffraction pattern calculated β fraction and crystallite size, for calculation to determine the crystallite size of the sample by using the Scherrer equation. Has been obtained an increase piezoelectric properties of PVDF films that characterized by increasing β fraction. Have been obtained β fraction increased from 25.4% up to 44% for temperatures of 130°C up to 170°C, respectively. Resistivity value has been obtained at temperature 130°C up to 170°C, decreased from 1.23 × 104 Wm up to 0.21 × 104 Wm respectively. From the experimental results and the calculation of crystallite sizes obtained for the samples with temperature 130°C up to 170°C respectively are increased from 7.2 nm up to 20.54 nm. These results indicate that mechanical treatment caused increase β fraction and decrease surface resistivity. Increasing temperatures will also increase the size of the crystallite of the sample. This happens because with the increasing temperature causes the higher the degree of crystallization of PVDF film sample is formed, so that the crystallite size also increases.

Highly reflective coatings for interior and exterior steel cladding and the energy efficiency of buildings

The effect of surface heat-radiation properties of coil-coated steel cladding material on the energy efficiency of buildings in Nordic climate is addressed by parallel temperature and energy usage measurements in a series of test cabins with different exterior solar reflectivity and interior thermal reflectivity. During one year, a number of one- or two-week experiments with air conditioner cooling and electrical floor heating were made while logging air-, radiation- and surface temperatures, energy consumption and weather conditions. Measurements show significant energy savings in the test cabins by the use of high thermal reflectivity interior surfaces both during heating and cooling and a strongly reduced cooling demand by the use of high solar reflectivity exterior surfaces. Results are interpreted within the context of a steady-state energy flux model, to illuminate the importance of surface resistance properties (radiation and convective heat dissipation).

Island structure and growth of pulsed laser deposited YBa 2Cu 3O 7− x superconducting thin films

Surface and grain topography of YBa 2Cu 3O 7− x epitaxial thin films grown on (100) NdGaO 3 using pulsed laser deposition has been studied using atomic force and scanning tunneling microscopy under ambient conditions. X-ray diffraction and transmission electron microscopy results support the force microscopy findings. Parametric studies of the effect of substrate temperature, annealing time and deposition rate were performed on 33 nm thick films. The observed island re-orientation as a function of time-at-temperature suggest that under our epitaxial growth conditions, the nuclei ripening time can be on the order of seconds. Implications for the observed island structure on transport and microwave surface resistance properties are briefly discussed.