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Phthalonitrile monomer containing oxazine ring (BPS‐Ph) was synthesized using bisphenol‐S, aniline, paraformaldehyde, and 4‐nitrophthalonitrile via a two‐step method. The differential scanning calorimetry (DSC) data of the curing process of BPS‐Ph monomer indicates that the peak polymerization temperature of the cyan group is about 250°C and that confirms the promoting effect of oxazine ring on the curing reaction of phthalonitrile. The rheological data of E51/DDS containing BPS‐Ph indicates that the BPS‐Ph monomer also has promoting effect on the curing process. The activation energy was studied via the iso‐conversional method principle. The activation energy corresponding to the E51/DDS crosslinking reaction is 75.79 and 60.54 kJ mol−1, respectively, for pure E51/DDS and E51/DDS/BPS‐Ph. Moreover, the activation energy of the crosslinking of phthalhydrazine is 74.1 kJ mol−1 which is rather lower than that in pure BPS‐Ph, and that implies the synergistically catalytic effect of the oxazine ring and the amine. The addition of BPS‐Ph monomer significantly improves the thermal behaviors of the thermoset. The char yield in N2 atmosphere increased from 15.6% to 53.9% when adding 30% BPS‐Ph to the E51/DDS. Moreover, the peak weight loss temperature decreased from 407 to 385°C. The phase separation size of poly‐BPS‐Ph in E51/DDS is about tens to hundreds nanometers according to the atomic force microscopy (AFM) phase diagram. It is indicated that incorporation of phthalonitrile monomer containing oxazine ring into epoxy/amine system is an applicable and effective way to promote the thermal behavior of the thermoset. [ABSTRACT FROM AUTHOR]

This paper explores the potential use of fused deposition modeling (FDM) technology for manufacturing microwave and millimeter-wave dielectric resonator antennas (DRAs) for 5G and beyond communication systems. DRAs operating at microwave and millimeter-wave (mmWave) frequency bands were simulated, fabricated, and analyzed in terms of manufacturing quality and radio frequency (RF) performance. Samples were manufactured using a 3D printer and PREPERM® ABS1000 filament, which offers a stable dielectric constant ( ε r = 10 ± 0.35) and low losses (tan δ = 0.003) over wide frequency and temperature ranges. Surface profile tests and microscope measurements revealed discrepancies in the dimensions in the xy-plane and along the z-axis, consistent with the observed shift in resonant frequency. Despite these variations, reasonably good agreement between RF-simulated and measured results was achieved, and the DRA array successfully covered the intended mmWave band. However, challenges in achieving high precision may restrict applications at higher mmWave bands. Nevertheless, compared with conventional methods, FDM techniques offer a highly accessible and flexible solution with a wide range of materials for home and micro-manufacturing of mmWave DRAs for modern 5G systems. [ABSTRACT FROM AUTHOR]

Four non-fluorinated sulfonimide polyamides (s-PAs) were successfully synthesized and a series of membranes were prepared by blending s-PA with polyvinylidene fluoride (PVDF) to achieve high-methanol-permeation resistivity for direct methanol fuel cell (DMFC) applications. Four membranes were fabricated by blending 50 wt% PVDF with s-PA, named BPD-101, BPD-102, BPD-111 and BPD-211, respectively. The s-PA/PVDF membranes exhibit high methanol resistivity, especially for the BPD-111 membrane with methanol resistivity of 8.13 × 10−7 cm2/s, which is one order of magnitude smaller than that of the Nafion 117 membrane. The tensile strength of the BPD-111 membrane is 15 MPa, comparable to that of the Nafion 117 membrane. Moreover, the four membranes also show good thermal stability up to 230 °C. The BPD-x membrane exhibits good oxidative stability, and the measured residual weights of the BPD-111 membrane are 97% and 93% after treating in Fenton's reagent (80 °C) for 1 h and 24 h, respectively. By considering the mechanical, thermal and dimensional properties, the polyamide proton-exchange membrane exhibits promising application potential for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Scheelite structure phase inorganic oxides show their irreplaceable role in numerous application areas due to their clear structure and superior properties, especially in dielectrics. Scheelite structure phase BiVO4 has been permanently studied but substitutions, modifications, and explorations of novel phases persist hitherto and inspire more interest. In this work, we report a novel Scheelite structure phase of Bi(Ge0.5Mo0.5)O4 and a detailed study of both structural analysis and dielectric properties investigation. Bi(Ge0.5Mo0.5)O4 adopts the monoclinic Scheelite structure, identical to BiVO4, with a dielectric permittivity of ∼ 35, Qf value of ∼20 000 GHz, and TCF value of ‒46 ppm/°C. No secondary ferroelastic transition was seen in Bi(Ge0.5Mo0.5)O4 till 600°C, close to its synthetical temperature. The results indicate the success of discovering a new Scheelite structure phase and its prior engineering potential in modifying and substituting BiVO4 over the dielectric area, photocatalyst, ion conductor, and so forth. [ABSTRACT FROM AUTHOR]