Effects of polymorphic form and particle size of SiO_(2)fillers on the properties of SiO_(2)-PEEK composites

The effects of polymorphic form and particle size of SiO_(2)fillers on the dielectric,mechanical and thermal properties of SiO_(2)-Poly-etheretherketone(SiO_(2)-PEEK)composites were investigated in this paper.Strong low frequency(<10Hz)Debye-like dielectric dispersions could be observed for all samples.The dielectric permittivity at high frequencies of the composite exhibits little morphology or particle size-sensitive characteristics of the SiO_(2)fillers.All the composites obtained in this case demonstrate the dielectric permittivities of~3.5 at high frequencies.The crystalline a-cristobalite filled composite exhibits lower dielectric loss and mechanical strength,but larger thermal expansion coefficient and thermal conductivity,compared with the similar particle sized amorphous SiO_(2)filled one.The crystalline a-quartz filled composite demonstrates the lowest mechanical strength and high-est dielectric loss.An increase in particle size of the spherical fused silica fillers decreases the dielectric loss,while increases the thermal conductivity of the composite.The flexural strength of the composite reaches the maximum value of 113 MPa when the particle size of spherical SiO_(2)filler is~10μm.Particle packing by combining optimal amounts of differently sized spherical fused silica fillers leads to a substantial improvement of mechanical strength(153MPa)coupled with reasonable dielectric and thermal properties due to the synergic effect(dielectric permittivity(ε_(r))=3.35,dielectric loss(tanδ)=1.63×10−3@10 GHz,thermal conductivity(l)=0.74 W/m*k(90°C),coefficient of thermal expansion(a)=23.6ppm/°C and relative density(r)=99.72%).

Broadband absorption performance of 3D-printed polyetheretherketone-based electromagnetic wave-absorbing composites

The rapid development of additive manufacturing technology has offered a new avenue for designing and fabricating high wave-absorbing meta structures.In this study,the mechanical properties and broadband absorption performance of Poly-Ether-Ether-Ketone(PEEK)–based electromagnetic wave–absorbing composite materials was investigated.The high-performance polymer PEEK was used as the matrix,and the materials with electromagnetic wave loss,such as reduced graphene oxide,Carbonyl Iron(CI),and Flake CI(FCI),were used as absorbers.Based on the theory of impedance matching,a wave-absorbing structure with a gradual impedance gradient was designed and printed.The test results showed that at the 2.0–18.0 GHz frequency band,the coverage rate of the effective absorption bandwidth was up to 72.0%,the average optimal reflectivity was–18.09 dB,and the wide-angle absorption range was 0°–30°.The advantages of additive manufacturing technology in designing and fabricating wave-absorbing structures are presented,demonstrating that the technology is an effective method for creating broadband absorbing structures.

Effects of FDM-3D printing parameters on mechanical properties and microstructure of CF/PEEK and GF/PEEK

Fused deposition modeling(FDM)has unique advantages in the rapid prototyping of thermoplastics which have been developed in diverse fields.However,although great efforts have been made to optimize FDM process,the mechanical properties of printed parts are limited by the weak interlamination bonding as well as the poor performance of raw filaments used,such as acrylonitrile butadiene styrene(ABS),polylactic acid(PLA).Adding fibers into thermoplastic matrix and preparing high-performance filaments have been indicated to enhance the properties of fabricated parts.Recently,heat-resistant polyetheretherketone(PEEK)and its fiber reinforced composites were proposed for FDM process due to overcoming the limitation of equipment and process.However,few researches have been reported on the effects of FDM-3 D printing parameters on the mechanical properties of fiber reinforced PEEK composites.Therefore,5 wt%carbon fiber(CF)and glass fiber(GF)reinforced PEEK composite filaments were prepared respectively in this study.The effects of various printing parameters including nozzle temperature,platform temperature,printing speed and layer thickness on the mechanical properties(including tensile strength,flexural strength and impact strength)were surveyed.To analyze the microstructure and failure reasons of printed CF/PEEK and GF/PEEK samples,the tensile fractured surfaces were investigated via scanning electron microscope(SEM).

MoS_(2) reinforced PEEK composite for improved aqueous boundary lubrication

Polyether-etherketone(PEEK)is a corrosion-resistant material that has been widely used in aqueous lubrication.However,its anti-wear performance must be improved for its application in the industry.In this study,to improve the anti-wear performance of PEEK for aqueous boundary lubrication,PEEK/MoS_(2)composites were prepared by ball-milling and spark plasma sintering processes.A competitive MoS_(2)mechanism between the low shear strength property and the role of promoting wear debris generation influences the anti-wear performance of PEEK/MoS_(2)composites.Experiments demonstrated that the coefficients of friction(COF)and wear rate of PEEK composite with 0.25 wt%MoS_(2)were significantly reduced 68%and 94%,respectively.Furthermore,this was the first time that a PEEK composite could achieve a COF of less than 0.05 in aqueous boundary lubrication.Its anti-wear performance was verified to be better than that of PEEK/carbon fiber(CF)and Thordon composites.The PEEK/MoS_(2)composite may be a potential material for underwater equipment because of its outstanding anti-wear performance in aqueous boundary lubrication.