Electrical Insulation Performance Research Articles

Vertically aligned and conformal BN-coated carbon fiber to achieve enhanced thermal conductivity and electrical insulation of a thermal interface material

Due to excellent thermal conductivity, high aspect ratio, and low density, mesophase pitch-based carbon fibers (MPCFs) are highly desired in electronic packaging. However, their thermal conductivity is hard to present in the polymer matrix because of the disordered stacking and low filling. Moreover, few researches are focused on the enhancement of the electrical insulation performance for MPCFs. Herein, we report vertically aligned and insulating boron nitride (BN) coated carbon fiber (CF) powders as significant fillers for polymer composites, endowing markedly improved thermal conductivity and electrical insulation. The high-quality BN coating layer on the surface of the CF is produced by a cooling precipitation method and high-temperature treatment with ingenious use of solubility properties, exhibiting a conformal, dense, and highly crystalline structure. This preparation method overcomes the limitations of coating thickness and particle agglomeration, resulting in a 31-fold enhancement of the electrical resistivity of the CF powders. After orientation treatment in a silicone rubber matrix, such CF@BN-filled pads exhibit good thermal conductivity, significantly improved insulation performance, and excellent mechanical properties. Among them, the optimized pad achieves a thermal conductivity of 12.06 W m−1 K−1, a volume resistivity of 50 × 108 Ω cm and a breakdown voltage of 3100 V mm−1, exceptional flexibility, and a favorable compression ratio (@45 psi) of 41.7 %. This work provides unique insights into constructing carbon fiber fillers as well as the preparation of high thermal conductivity composites, thereby expanding the application scenarios of carbon fiber powder in electronic packaging.

Enhancement of thermal conductivity and insulation of silicone thermal interface material through surface modification and synergistic effects of nanofillers for thermal management of electronic devices

Thermal interface materials (TIMs) play an irreplaceable role in highly integrated microelectronic devices. In this work, the addition of acidified carbon nanotubes modified by 3-aminopropyl triethoxysilane (KH550) had an effective enhancement to the thermal conductivity, thermal stability, and electrical insulation performance of silicone grease. On this basis, multi-filled silicone grease composites with better thermal conductivity and electrical insulation were prepared by introducing zinc oxide (ZnO) and Graphene nanoflakes (GNFs). The thermal conductivity of silicone grease achieved 1.438 W m−1 K−1, while the volume resistivity still exceeded 1013 Ω·cm. Additionally, the study explored the impact of varying filler parameters, temperature, and contact pressure on the interface thermal contact resistance of silicone grease. The best performance silicone grease applied to the cooling of the high-power LED exhibited excellent heat dissipation. This work presented a reference for the design and development of low cost, high performance TIMs.

Atomically engineered Al-doped LaOCl for chlorine-ion batteries

LaOCl belongs to one kind of promising solid electrolyte for chlorine-ion batteries due to its excellent electric insulation performance and special layered structure. However, LaOCl still suffers from poor chlorine-ion conductivity. Then, we proposed microstructure modulation of LaOCl to solve this problem based on Al doping method. Firstly, we carried out first-principles and ab-initio molecular dynamics (AIMD) calculations to investigate the internal relation among structure stability, chlorine-ion conductivity and related physicochemical properties of Al doped LaOCl(La1-xAlxOCl). It is found that La0.75Al0.25OCl not only possesses most stable structure but also demonstrates the best ductility. Moreover, La0.75Al0.25OCl also possesses much lower chlorine-ion diffusion energy barrier than LaOCl(0.40 eV vs.0.78 eV) and its chlorine-ion conductivity goes as high as 5.4 × 10−3 S/cm at 300K. This is attributed to the optimal reconstruction of La–Cl coordination structure induced by Al dopant, which weakens the limiting effect of La–Cl bond as far as possible. Meanwhile,La0.75Al0.25OCl exhibits excellent electrical insulating property due to its wide band gap of 5.87 eV. In addition, La0.75Al0.25OCl exhibits wide electrochemical window with La and Al metal acted as anode materials, respectively (1.92–9.66 V for La and 0–7.74 V for Al). At this stage, La0.75Al0.25OCl solid electrolyte requires no chlorine-ion uptake and loss in the process of oxidation and reduction, indicating its excellent electrochemical stability.

Fabrication Aspects and Performance Characterization of α-Al2O3/AlPO4 Based Sandwich Configuration Flow Channel Inserts and Coatings for High Temperature Liquid Metal Applications

Abstract Liquid metals (LMs) exhibit several key characteristics justifying their utilization as coolants and breeders for nuclear fusion reactors and advanced fission reactors. In fusion reactors, the LMs confront an exorbitantly high flow retarding force, due to the magneto-hydro-dynamics (MHD) effect, imposing significant demands on the pumping power and designs of ancillary coolant systems. Corrosion of structural materials leading to activated corrosion products and coolant chemistry control are some of the vital issues common to both fusion and fission reactors employing liquid lead (Pb) and its alloys. To address these concerns, different technological solutions such as flow channel inserts (FCIs) and high temperature compatible corrosion resistant coatings are being investigated to provide a chemical and/or electrical isolation between the LM and structural material for advanced reactors. In this study, three different prototype geometries (circular, square, and 90 deg bend) of steel-insulator-steel sandwich FCIs are fabricated for fusion reactor applications and an extensive characterization of the electrical insulation is performed over an operating temperature range of 100 °C–600 °C. Welding trials and pneumatic pressure tests up to 10 kg/cm2 (g) are performed on the assemblies to validate the electrical and mechanical integrity over typical fusion reactor operational regime. This paper presents detailed fabrication aspects along with quantitative estimations of insulation filling density, electrical insulation performance and, for the first time, a detailed systematic study of insulation degradation resulting from the combined effects of tungsten inert gas (TIG) welding, exposure to pressure and machining operations on these FCIs. The paper also provides critical details derived from the metallurgical examinations and visual observations from the destructive tests executed on the prototypes. Further, from an implementation perspective toward Lead-cooled Fast Reactors (LFRs), a preliminary feasibility assessment of the α-Al2O3/AlPO4 coating is performed through thin film deposition trials on planar and non-planar substrates followed by mechanical characterizations, such as coating thickness, surface roughness, adhesion strength and microhardness. Metallurgical analyses are presented and discussed to assess Pb ingress after 700 h of continuous exposure to molten Pb alloy at 300 °C–400 °C.

A polymer trench filling based silicon isolation technique and its application to two-axis scanning comb-drive micromirrors

Electrostatic micromirrors can be widely used in LiDAR, displays, AR/VR and medical imaging. Electrically insulated silicon enabled by trenches filled with thermal oxide and polysilicon is commonly used for 2-axis electrostatic comb-drive scanning mirrors made on SOI (silicon-on-insulator) wafers. These trenches provide both electrical isolation and mechanical stability. However, this method has drawbacks such as high deposition temperature, voids, and high residual stress. In this work, a polymer filling method is proposed to form electrical insulation trenches in the silicon device layer of SOI wafers. Only low-temperature processes are used in this method and the silicon trenches can be fully filled up reliably. Furthermore, the filling polymer not only relieves residual stresses but also significantly increases the shock resistance of the micromirrors made with this method. In particular, Benzocyclobutene (BCB) is employed and a process has been developed to effectively fill deep silicon trenches. Using this method, two-axis electrostatic micromirrors have been successfully fabricated and tested. Experimental results show that the BCB-filled trenches demonstrate excellent electrical insulation performance and mechanical stability and the fabricated 2-axis mirrors can achieve a large field of view of 60°×40° and stand high impact over 2500 g.

Introduction to Topology Optimization for the Design of High Voltage Insulators

High Voltage insulators play a vital role in power transmission systems and are subjected to combined electrical, mechanical, and thermal stress. Common design strategies for HV insulators involve semi-analytical methods and Finite Element Analyses (FEA) to arrive at designs that meet the required design and manufacturing criteria. Topology Optimization (TO) is a design strategy widely adopted to minimize the weight and volume of the design while retaining its performance. In this work, we propose a modification to the traditional TO process to maximize the combined electrical and structural performance of HV insulators. This modification incorporates electric field considerations into the T.O. process.

A metal-based microencapsulated phase change material (MEPCM) with high thermal conductivity, electrical insulation and flame retardancy and its application in epoxy resin

Using the “double-layer coating, sacrificial inner layer” method, MEPCM with a thermal expansion void was prepared by encapsulating Sn particles into a magnesium hydroxide shell. The results showed that MEPCM exhibited better thermal reliability than those without a thermal expansion void. More importantly, the Sn was selected as the core material that MEPCM was enabled to have large volume latent heat (425.2 J/cm3) and high thermal conductivity (10.06 W/m·K), and magnesium hydroxide was chosen as the shell material that MEPCM was given great heat absorption ability (260 J/g), excellent electrical insulation performance and flame retardancy. By adding 20 vol% MEPCM to EP, the thermal conductivity of the composite improved 164.9 %. The volume resistivity of EP/MEPCM composites was 2.1 × 1012 Ω·cm. The pHRR and THR of EP/MEPCM composites were only 471.64 kW/m2 and 12.95 m2, respectively. The existence of MEPCM enhanced the thermal conductivity, electrical insulation performance and flame retardancy of EP.

Ultralong Nanowires of Cadmium Phosphate Hydroxide Synthesized Using a Cadmium Oleate Precursor Hydrothermal Method and Sulfidation Conversion to Ultralong CdS Nanowires.

Ultralong nanowires with ultrahigh aspect ratios exhibit high flexibility, and they are promising for applications in various fields. Herein, a cadmium oleate precursor hydrothermal method is developed for the synthesis of ultralong nanowires of cadmium phosphate hydroxide. In this method, water-soluble cadmium salt is used as the cadmium source, water-soluble phosphate is used as the phosphorus source, and sodium oleate is adopted as a reactant to form cadmium oleate precursor and as a structure-directing agent. By using this method, ultralong nanowires of cadmium phosphate hydroxide are successfully synthesized using CdCl2, sodium oleate, and NaH2PO4 as reactants in an aqueous solution by hydrothermal treatment at 180 °C for 24 h. In addition, a new type of flexible fire-resistant inorganic paper with good electrical insulation performance is fabricated using ultralong nanowires of cadmium phosphate hydroxide. As an example of the extended application of this synthetic method, ultralong nanowires of cadmium phosphate hydroxide can be converted to ultralong CdS nanowires through a convenient sulfidation reaction. In this way, ultralong CdS nanowires are successfully synthesized by simple sulfidation of ultralong nanowires of cadmium phosphate hydroxide under mild conditions. The as-prepared ultralong nanowires of cadmium phosphate hydroxide are promising for applications as the precursors and templates for synthesizing other inorganic ultralong nanowires and have wide applications in various fields.

Ameliorated DC Insulation Performance of EPDM through Chemical Grafting with a Voltage Stabilizer

Ethylene-Propylene-Diene Rubber (EPDM) is widely utilized as a high-performance insulation material in high-voltage direct current (HVDC) cable accessories, owing to its exceptional electrical and thermal properties. In this study, we have successfully synthesized and employed 4-vinyl oxyacetophenone (VPE) as a modification agent to develop the chemically grafted EPDM materials (EPDM-g-VPE) just through thermal crosslinking reaction and melt blending approach. Infrared spectroscopy results reveal that during thermal cross-linking process, VPE efficiently grafted onto EPDM molecular-chains through free radical addition reaction. Following VPE grafting, the DC dielectric breakdown strength and electrical conductivity of EPDM are significantly increased and noticeably decreased respectively. Theoretical electronic structure calculations corroborate that VPE’s electron-affinity and energy-gap enable it to efficiently absorb thermal electron energy without undergoing collision ionization, thereby enhancing EPDM’s breakdown resistance. Simultaneously, VPE molecules exhibit a high affinity for capturing electron charge carriers within EPDM polymer-molecules. Space charge and thermally stimulated current tests demonstrate that the stable and uniformly distributed charge traps can be effectively introduced into EPDM matrix by grafting VPE modification, thereby suppressing transport and injection of charge carriers. Consequently, this approach substantially improves DC electrical insulation performance of EPDM. This research not only successfully enhances the electrical insulation performance of EPDM but also showcases the wide-ranging potential of chemical modification technology in cable accessory materials.

GMP/Al2O3/ZnO/PDMS thermal interface materials with anisotropic thermal conductivity and electrical insulation ability obtained by 3D‐printing method

AbstractDue to the continuous increase in power density and power consumption, thermal management has become a crucial issue in electronic devices like integrated circuits. Polymer‐based thermal conductive composites possess excellent thermal and mechanical properties, making them ideal materials for thermal management in the modern microelectronic industry. In this work, we present a combination of filler hybridization strategy and 3D‐printing technology to synergistically enhance the thermal conductivity of graphite microplatelets (GMP)/alumina (Al2O3)/zinc oxide (ZnO)/polydimethylsiloxane (PDMS) composite (o‐GAZP). When the content of GMP reaches 4.5 vol%, the 3D‐printed composite material exhibits a directional thermal conductivity of up to 4.51 W m−1 K−1. This value is significantly higher than the thermal conductivity of a randomly mixed GMP/Al2O3/ZnO/PDMS composite (1.98 W m−1 K−1). The remarkable thermal conductivity can be attributed to the anisotropic structural design, which benefits from the orientation of GMP and the creation of a multi‐scale dense structure through filler compounding. Additionally, the presence of Al2O3 and ZnO effectively separates the GMP particles, preventing the formation of electron transfer pathways and improving the electrical insulation performance of the composites. Furthermore, the impact of the anisotropic structural design on the thermal conductivity of the composites was verified through finite element simulation. This study demonstrates that constructing efficient thermally conductive and electrically insulating pathways by densely packing highly oriented two‐dimensional anisotropic graphite‐based fillers with uniformly dispersed thermally conductive and electrically insulating fillers is a simple and effective method to enhance the composites' thermal conductivity, electrical resistivity, and mechanical properties simultaneously. These findings hold great potential for various scalable thermal‐related applications. By implementing this approach, composites can exhibit excellent thermal conductivity, high electrical resistivity, and superior mechanical performance.

Significant enhancement of high-temperature capacitive energy storage in dielectric films through surface self-assembly of BNNS coatings

Polymer dielectrics, serving as integral components in electrostatic capacitors, must meet the escalating demands for electrical energy storage and conversion in harsh environments. However, the current enhancement of breakdown strength in polymer composite materials often relies on intricate nanostructure designs or inorganic deposition methods, which result in high production costs, slow processing, and hinder industrial scalability. Here, we present an economically efficient and easily implementable surface modification approach. This method induces the self-assembly of high-insulation-performance boron nitride nanosheets (BNNS) on the film surface through electrostatic interactions, thereby enhancing the high-temperature electrical insulation and energy storage performance of polymer dielectrics. At room temperature, the breakdown strength of the BNNS-coated polyetherimide (PEI) significantly increased to 544 MV/m, representing a 100 MV/m improvement compared to pure PEI. At elevated temperatures (200 °C), the organic insulator achieved a high breakdown strength of 439 MV/m and a high energy density of 2.59 J/cm3. The tangential orientation of the nanosheets effectively impedes charge injection from electrodes while promoting charge dissipation and heat transfer. This work provides a novel avenue for the design of high-performance polymer dielectrics for high-temperature energy storage through surface engineering.

Thermally matched multilayer ceramic composite insulating layers for high-temperature thick/thin-film sensors on nickel-based superalloy

Thick/thin-film sensors are used for health monitoring of components such as aero-engines, which are mainly cast from electrically conductive nickel-based superalloys. It is necessary to prepare an insulating layer between the nickel-based superalloys and the thick/thin film sensor. For this purpose, a thermally matched multilayer ceramic composite insulating layers for thick/thin-film sensors have been designed. Three dielectric pastes with coefficients of thermal expansion similar to those of the metal substrate and Pt/Rh–Pt thick-film thermocouples were prepared on nickel-based superalloys by screen printing technique. Problems regarding the bonding strength of the insulating layers were solved, which improved the insulating properties. The microstructural characteristics of the insulating layers were characterized by scanning electron microscopy, and their insulation resistance at high temperatures was tested. The results show that the insulation resistance of insulating layers is increased by a factor of about 10 in this paper compared to the insulation resistance of insulating layers prepared by sputtering and other techniques in previous articles. When the temperature is 800 °C, the resistance value of the samples reaches 30.47 MΩ. It is noteworthy that the insulation resistance is still higher than 21 MΩ after annealing at 800 °C for 10 h. Moreover, the insulating coating survived thermal shock tests without cracking or delaminating. A S-type thermocouple is prepared on the insulating layers to verify its high-temperature electrical insulation performance. Test results show that the output voltage of the S-type thermocouple had a high linearity with an average Seebeck coefficient of 10.5 μV/°C during the temperature range of 200–1000 °C. Experiments show that the S-type thermocouple works stably at high temperatures and thermally matched multilayer composite insulation layers have good insulating properties.

Electrical-Tree Resistant Characteristics of SEBS and Nano-SiO2 Modified Polypropylene Composites

Polypropylene (PP) composite materials with both high mechanical toughness and electrical insulation performance are prepared by incorporating styrene-ethylene/butylene-styrene (SEBS) block copolymer as a toughening agent and nanoscale silica (SiO2) as a inorganic modifier to enhance electrical-tree and breakdown resistances. The effects and mechanisms of SEBS toughening agent and SiO2 nanofiller on the thermal-mechanical properties and electrical insulation performances of PP material are investigated through the mechanical tests as well as the accelerated electrical-tree aging and alternative current (AC) breakdown experiments. The elastic modulus of SiO2/SEBS/PP composite is slightly lower than that of pure PP material, while the thermal elongation rate remains superior to cross-linked polyethylene (XLPE), which is competent in mechanical performances for main insulation materials in high-voltage cables. The addition of styrene-ethylene/butylene-styrene (SEBS) facilitates electrical-tree growth in PP matrix and thus leads to the reduction in dielectric breakdown strength of PP material. In contrast, the incorporation of nano-SiO2 can effectively improve the electrical-tree resistance and dielectric breakdown strength of PP material, making the SiO2/SEBS/PP composite a promising candidate for high-voltage cable insulation. The tests and analyses of thermal stimulated depolarization current (TSDC) reveal that the SEBS toughing additive introduces the shallow charge traps in PP matrix, making it easier for the trapped charges to transition into charge carriers, thus leading to a considerable decrease in electrical-tree resistance and insulation strength of PP material. Meanwhile, the SiO2 nanofiller can introduce deeper charge traps into PP matrix than the structural-defect intrinsic charge traps, resulting in a significant amelioration in the electrical-tree resistant and insulation performances for SEBS/PP composite. The present study demonstrates that SiO2/SEBS/PP composite possesses sufficiently high electrical-tree resistance and dielectric breakdown strength as well as suitable thermal-mechanical properties, offering a potential application in main insulation of high-voltage cables and providing an effective pathway for developing novel recyclable AC high-voltage cables.

A hBN/B-Si-Al-O-glass composite coating growth on SiCp/Al composite using one-step PEO with nanoparticle addition for outstanding electrical insulation performance

A comprehensive study of the formation of electrical insulation coatings on SiCp/Al composite using plasma electrolytic oxidation (PEO) in an electrolytic system with hBN nanoparticles has been carried out. A complete coating can be formed under a high positive voltage (550–600 V) in a short period of time (3 min), and the coating is mainly composed of the hBN crystal phase as well as some amorphous phases. The high temperature of the local plasma in the PEO process impels these amorphous phases to form an amorphous B-Si-Al-O glass phase. As the treatment time goes on, the cross-sectional porosity of the coating first decreases rapidly and then increases slowly. This is attributed to the fact that the nanoparticles continuously deposit and sinter to repair the larger pores during the coating growth process, hence reducing porosity. Within 6 min, the coating thickness rapidly increases to 133.3 μm, showing excellent electrical insulation performance (with a breakdown voltage of 1460 ± 28 V, volume resistance of 5.52 ± 0.26 G·Ω, electrical resistivity of 4.18 × 1010 Ω∙cm) and high optical band gap value (above 5 eV), which is suitable for electronic packaging or dielectric materials.

Research and Application Progress of Resin-Based Composite Materials in the Electrical Insulation Field.

The research and application progress of resin-based composite materials in the field of electrical insulation has attracted considerable attention and emerged as a current research hotspot. This review comprehensively summarized the research and application progress of resin-based composite materials in the field of electrical insulation, providing detailed insights into their concept, properties, and preparation methods. In addition, a comprehensive evaluation of the electrical insulation performance, mechanical properties, and thermal properties of resin-based composite materials was presented, along with an in-depth analysis of their current application status. Despite the immense potential and development opportunities of resin-based composite materials, they also face several challenges. This review serves as a valuable reference and resource for researchers in related fields and aimed to promote further research and application development of resin-based composite materials in the field of electrical insulation.

Improvement of electrical insulation performance of silicone rubber cables due to exposure to heat and radiation

AbstractThermal treatments, with and without co‐irradiation with gamma rays, were given to safety‐related cables insulated with silicone rubber for nuclear power plants (NPPs). To examine the effects of the above treatments on the insulation properties of the cables, DC voltages were applied to them and the induced changes in leakage current were measured by the current integration method. As a result, it has become clear that the leakage current is the largest in the pristine untreated cable. In addition, almost no leakage current flows in the cables heated at 200°C or 290°C for several hundred hours. The leakage current remains small when the co‐irradiation with gamma rays was given at 100°C or 200°C for relatively long periods exceeding 1000 h. The reason for these results seems to be that the silicone rubber insulation becomes hardened as a result of the thermal or concurrent treatment, and the transport of ionic carriers becomes difficult. The above results indicate experimentally that the degradation is not a matter of great concern for the insulation performance of silicone‐rubber‐insulated safety‐related cables in NPPs.

Effect of amino-modified SiO2 nanoparticles on micro-water diffusion behaviour in soybean oil-based natural ester oil-paper insulation system

Nanoparticles can significantly improve the insulation property of oil-paper insulation systems. In this paper, amino-modified SiO2 nanoparticles were used as nano-additives to establish a soybean oil-cellulose paper oil-paper insulation model, and the effect of amino-modified SiO2 nanoparticles on micro-water diffusion in oil-paper insulation systems was systematically studied. Simulation experiments show that amino-modified SiO2 nanoparticles can effectively delay the diffusion of water molecules in oil-paper insulation. As the temperature rises, compared with unmodified SiO2 nanoparticles, the diffusion motion of water molecules in amino-modified SiO2 nanoparticles oil–water model is slower. When the temperature is 383 K, the water molecule diffusion coefficient of the unmodified model is 1.22 times that of the modified model, and amino-modified SiO2 nanoparticles can form special hydrogen bonds with water molecules, preventing water molecules from further diffusing into cellulose paper, breaking the cellulose chain leads to a decrease in mechanical property, and further generating small molecules such as water and acid, which accelerate the aging of oil-paper insulation systems. Indirectly improve the electrical performance and aging performance of oil-paper insulation.

Improving the Hydrophobicity and Insulation Properties of Epoxy Resins by the Self-Assembly-Induced Coating of Fluorinated Graphene.

Moisture and insulation deterioration are important factors that cause the failure of epoxy packaging materials. Thus, improving the long-term stability of epoxy resins in a hot and humid environment is an important prerequisite for electronic components to adapt to complex working conditions and achieve high power densities. In this study, fluorinated graphene doped with hydroxy-terminated poly(dimethylsiloxane) was prepared and self-assembled into a micro/nanostructure on the surface of an epoxy resin, which effectively improved the surface hydrophobicity of the epoxy resin. In addition, the doping with hydroxy-terminated poly(dimethylsiloxane) modified the fluorinated graphene filler, thereby forming an arch bridge energy band structure inside the epoxy resin and thus regulating carrier migration. The water absorption of the epoxy resin decreased from 1.02 to 0.24%, and the surface water contact angle increased from 93.58 to 133.2°. Moreover, the electrical insulation performance of the modified epoxy resin was greatly improved when the surface resistivity and flashover voltage increased by 50.5 and 36.4%, respectively. Therefore, the proposed method realizes a simultaneous improvement in the hydrophobicity and insulation of epoxy resins.

Strategy for Constructing Epoxy Composites with High Effective Thermal Conductive Capability Based on Three-Dimensional Cellulose and Multiwalled Carbon Nanotube Network

High effective thermal management materials have become a crucial factor for the reliability and lifetime of devices. Herein, epoxy resin (EP) composites with superior thermal conductive efficiency were fabricated via the homogeneous dispersion of carboxylated multiwalled carbon nanotubes (CMWCNTs) in cellulose nanofiber (CNF) aerogels, and then the EP precursors were impregnated and cured. The thermal conductivity of EP/CNF/CMWCNT thermosets containing only 0.65 wt % CMWCNTs increased from 0.19 W·m–1·k–1 for pristine EP to 0.93 W·m–1·k–1 and increased by 389.5%. As a result, the composites presented excellent heat absorption and dissipation performance, which are demonstrated by the infrared thermal camera tests. Besides, the composites showed highly electric insulating performance, and its volume electrical resistivity was as high as 6.48 × 1015 Ω·cm–1 due to the low content of CMWCNTs in thermosets. The glass-transition temperature of EP/CNF/CMWCNT composites increased from 132.6 °C for neat EP thermosets to 153.3 °C, as indicated by the dynamic mechanical analysis. Moreover, thermal mechanical analysis demonstrated that the resultant EP composites possessed excellent dimensional stability. The obtained EP/CNF/CMWCNT composites were allowed to work at a higher temperature environment. This presented research work provided an alternative approach for preparing EP composites with highly efficient thermal management and electrical insulation performance, which allowed their application in electronic packaging, devices, and other electronic applications.

Preliminary exploration of the electrical insulation performance of APPJ SiO2 coating on 304 stainless steel pipes

The atmospheric pressure plasma jet (APPJ) technique is used to prepare SiO2 insulation coatings onto the outer surface of 304 stainless steel pipes (304-SSPs). The diameter and surface roughness of 304-SSPs increase from 18 to 32 mm and 0.1 to 1.0 μm. The results show that APPJ scanning methods have little influence on the chemical composition, chemical bond structure, crystal structure, and surface morphology of SiO2 coatings, which display Si/O = 1/(1.95 ± 0.02), dominant Si-O bond, amorphous structure, and dense layer structure. However, APPJ scanning methods have obvious influence on the uniformity and electrical insulation resistance (REI) of SiO2 coatings. Only when APPJ is parallel to the normal direction of 304-SSPs outer surface, the balance between APPJ impingement, gravity, and coating surface tension could reach the optimal condition, which improves the uniformity and REI of SiO2 coatings. With the optimal scanning method, REI of SiO2 coatings decrease with the increase of surface roughness of 304-SSPs, which are caused by the decrease of effective thickness of SiO2 coatings. Most importantly, with the other parameters as constant, REI of SiO2 coatings reaches to ∼101 MΩ and displays the better uniformity when the diameter of 304-SSPs is about 5 times the diameter of APPJ tube.