Shuling Zhang

Size-dependent melting point of noble metals

A simple model, without any free parameter, is introduced to predict the size-dependent melting temperature of noble metals in this contribution. It is found that the model predictions for the melting point depression of both Au and Ag nanoparticles correspond to the experimental and computer simulation results well.

A material with high electromagnetic radiation shielding effectiveness fabricated using multi-walled carbon nanotubes wrapped with poly(ether sulfone) in a poly(ether ether ketone) matrix

An electromagnetic radiation absorber material with high shielding effectiveness as well as good mechanical and thermal properties was produced using multi-walled carbon nanotubes (MWCNTs) wrapped in poly(ether sulfone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix fabricated by melt-blending. The electromagnetic, mechanical, and thermal properties of this material were characterized using a vector network analyzer, universal tester, and thermal gravimetric analyzer, respectively. The results indicate that wrapped-MWCNT–PEEK composites show different degrees of improvement in the measured properties compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the good dispersion of wrapped-MWCNTs in PEEK, and the strong interfacial adhesion between wrapped-MWCNTs and PEEK.

Ultra low dielectric constant soluble polyhedral oligomeric silsesquioxane (POSS)–poly(aryl ether ketone) nanocomposites with excellent thermal and mechanical properties

A series of novel ultra low dielectric constant soluble organic–inorganic nanocomposites in which nanoscale octa-aminophenyl polyhedral oligomeric silsesquioxanes (octaAmino POSS-Ph8) were covalently linked onto the fluoropoly(ether ether ketone)s (PEEK-CF3-COOH) were prepared and characterized. The chemical structures of the polymer matrix and nanocomposites were confirmed by 1H NMR and FT-IR spectra. The analysis of wide-angle X-ray diffraction (WAXD) and X-ray photoelectron spectra (XPS) indicated that the POSS clusters were successfully incorporated into the polymer matrix and the homogeneous dispersion of POSS cages in the polymer matrix was evidenced by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (Si-mapping). Furthermore, the influence of the incorporation of POSS particles on the properties of nanocomposites is investigated. The dielectric constants of the organic–inorganic nanocomposites were drastically reduced relative to neat PEEK-CF3-COOH films and the dielectric constant could achieve as low as 1.71 (1 MHz). Besides, the thermal and mechanical properties of the nanocomposites were significantly improved by incorporation of octaAmino POSS-Ph8 moieties. Meanwhile, the nanocomposite thin films still retained the good transparency.

Material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties produced using multi-wall carbon nanotubes wrapped with poly(ether sulphone) in a poly(ether ether ketone) matrix

A material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties was produced using multi-wall carbon nanotubes (MWCNTs) wrapped with poly(ether sulphone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix. The material was fabricated using melt-blending, and MWCNT/PEEK composites show different degrees of improvement in the measured dielectric, mechanical, and thermal properties as compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the effect of wrapping MWCNTs with PES, the good dispersion of the wrapped MWCNTs in PEEK, and the strong interfacial adhesion between the wrapped MWCNTs and the PEEK.

Synthesis and Characterization of Soluble Low-κ Poly (aryl ether ketone) Copolymers with Pendent Adamantyl Groups:

The aromatic bisphenol monomers containing bulky pendant (adamantyl) groups, 4-(1-adamantyl)-1,3-benzene diol (AdRES) and 4,8-bis(1-adamantyl)-1,5-dihydroxy naphthalene (AdNp) were successfully prepared via the Friedel—Crafts reaction and used to synthesize a series of new poly (aryl ether ketone) copolymers with (3-trifluoromethyl) phenyl hydroquinone or other bisphenols and 4,4′-difluorobenzophenone (DFB) by nucleophilic aromatic substitution polycondensation. All the novel PAEKs were amorphous and their solubility was improved by the introduction of bulky pendant groups, so they were readily soluble in common organic solvents. DSC data showed that Tg values of the resultant copolymers were dramatically increased when adamantane is incorporated into the copolymers as a pendent group and their T g values increased with increasing content of adamantyl groups. According to thermogravimetric analysis, all the polymers showed excellent thermal stabilities. The mechanical properties of the polymers can be con...The aromatic bisphenol monomers containing bulky pendant (adamantyl) groups, 4-(1-adamantyl)-1,3-benzene diol (AdRES) and 4,8-bis(1-adamantyl)-1,5-dihydroxy naphthalene (AdNp) were successfully prepared via the Friedel–Crafts reaction and used to synthesize a series of new poly (aryl ether ketone) copolymers with (3-trifluoromethyl) phenyl hydroquinone or other bisphenols and 4,4 difluorobenzophenone (DFB) by nucleophilic aromatic substitution polycondensation. All the novel PAEKs were amorphous and their solubility was improved by the introduction of bulky pendant groups, so they were readily soluble in common organic solvents. DSC data showed that Tg values of the resultant copolymers were dramatically increased when adamantane is incorporated into the copolymers as a pendent group and their Tg values increased with increasing content of adamantyl groups. According to thermogravimetric analysis, all the polymers showed excellent thermal stabilities. The mechanical properties of the polymers can be controlled by varying the molar ratio of diphenol-containing adamantyl to (3-trifluoromethyl) phenyl hydroquinone. These novel poly (aryl ether ketone) films had low dielectric constants ranged from 2.62 to 2.95 at 1 MHz and low water absorptions of 0.12–0.29% their dielectric constants decreased with the increasing content of the adamantyl group.

Design and preparation of graphene/poly(ether ether ketone) composites with excellent electrical conductivity

Graphene/poly(ether ether ketone) (m-TRG/PEEK) composites with excellent electrical conductivity were fabricated by hot pressing technique with thermally reduced graphene nanosheets (m-TRG) which were modified by poly(ether sulfone). Moreover, the conductive, thermal, and mechanical properties of PEEK/m-TRG composites were investigated by the precision impedance analyzer, thermal gravimetric analyzer, differential scanning calorimetry, and universal tester, respectively. The electrical conductivity of m-TRG/PEEK composites was greatly improved by incorporating graphene, resulting in a sharp transition from electrical insulator to semiconductor with a low percolation threshold of 0.76 vol.%. A high electrical conductivity of 0.18 S m−1 was achieved with 3.84 vol.% of m-TRG. The data were compared with those of composites reduced chemically, and the results showed that thermal reduction was an effective method to acquire higher electrical conductive composites. The excellent electrical property should be attributed to the large specific surface area of m-TRG, well dispersion of m-TRG in PEEK matrix, and good compatibility of m-TRG with PEEK matrix, as proven by scanning electron microscope. Besides, m-TRG/PEEK composites also exhibited relatively good thermal and mechanical properties.

Ultra low dielectric constant hybrid films via side chain grafting reaction of poly(ether ether ketone) and phosphotungstic acid

The novel ultra low dielectric constant poly(ether ether ketone) hybrid films in which nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups (PEEK–CF3–COOH) in the presence the silane coupling agent γ-aminopropyltriethoxysilane (KH-550) were prepared and characterized. The chemical structures of the PWA/PEEK–CF3–COOH hybrid films were confirmed by FT-IR spectroscopy and 1H-NMR. The analysis of wide-angle X-ray diffraction (WAXD) indicated that the PWA clusters could not form crystalline structures in the PEEK–CF3–COOH matrix, and the investigation of the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (W-mapping) revealed that the PWA particles were well dispersed in the PEEK–CF3–COOH matrix with nanoscale. The influence of the incorporation of PWA particles by side chain grafting reaction on the properties of PEEK–CF3–COOH was studied. The dielectric constants of the PWA/PEEK–CF3–COOH hybrid films were remarkably lower than that of the neat PEEK–CF3–COOH film and the lowest value their dielectric constant could achieve was as low as 1.96 (1 MHz) when the content of grafted PWA reached 10 wt%. Meanwhile, the hybrid films still retain the excellent thermal and mechanical properties as well as the good transparency.

Multi-walled carbon nanotube induced co-continuity of poly(ether ether ketone)/polyimide blends for high performance conductive materials

A high performance conductive material with excellent mechanical and thermal properties was prepared by melt-blending, and its performance was adjusted by controlling the selective location of multi-walled carbon nanotubes (MWCNTs) in a poly(ether ether ketone) (PEEK)/thermoplastic polyimide (TPI) matrix. With increasing content of MWCNTs, the morphology of the PEEK/TPI blends was changed from typical sea-island morphology to a co-continuous structure, which was due to the selective location of MWCNTs in the TPI phase. Notably, the electrical percolation threshold was reduced to as low as 0.6 wt% due to the selective distribution of MWCNTs in the induced co-continuous PEEK/TPI structure, which is the lowest value reported for PEEK-based MWCNTs composites. Moreover, the introduction of MWCNTs could improve the dynamic mechanical properties and thermal stability of the PEEK/TPI blend effectively.

The preparation and electrical properties of the functionalized graphene/poly (ether sulfone) nanocomposites

Chemical functionalized graphene (f-G) was obtained by the reaction of the residual epoxide and carboxyl functional groups on the hydrazine-reduced graphene (G) sheets with hydroquinone. The efficacy of the functionalization reaction of graphene was confirmed by X-ray photoelectron spectroscopy and thermogravimetric analysis. Atomic force microscopy and transmission electron microscopy images showed that the functionalized graphene can be easily exfoliated into functionalized graphene nanosheets composed of single or bilayers of graphene sheets. The f-G was used to prepare conductive poly (ether sulfone) (PES) composites (f-G/PES) via the solution casting method and the alternating current (AC) and direct current (DC) properties of f-G/PES composites were investigated. It was observed that good dispersion of f-G nanosheets in PES matrix resulted in a low percolation threshold of 0.355 vol.%. Hopping type of charge transport occurred during the insulator–semiconductor transition of f-G/PES composites. Impedance measurement was carried out to evaluate interfacial capacitance of the composites, and the interfacial capacitance of the composites increased to 1041.9 pF of f-G/PES composites with 5 wt.% f-G from 30.48 pF of f-G/PES composites with 0.5 wt.% f-G.

Influence of the addition of lubricant on the properties of poly(ether ether ketone)/basalt fiber composites

Improvement in the processability of poly(ether ether ketone)/basalt fiber (PEEK/BF) composites with less influence on other properties is important. A novel high-temperature lubricant GENIOPLAST PELLETS (GPPS) was used in order to decrease the melt viscosity of PEEK/BF composites. The compounds of PEEK/BF/GPPS were characterized by torque of screw, universal tester, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The results showed that a small amount of GPPS could greatly decrease melt viscosity of the composites during processing, and improve the dispersion uniformity and orientation of BF in the PEEK matrix, followed by the enhancement of the modulus and strength of PEEK/BF composites, meanwhile the thermal stability of the compounds was almost unaffected.