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The conventional circular waveguide 90° TE01 bend makes it difficult to achieve broadband because of the serious interference from TM11 mode. To solve this problem, the mode coupling characteristics in the hexagonal waveguides are investigated in this paper, and it is found that when the deformation amplitude is appropriate, not only the degradation between TE01 and TM11 is broken but other parasitic modes can be efficiently suppressed. Based on the analysis, an oversized broadband TE01 waveguide bend with variable curvature is proposed, and its transmission efficiency is over 95% from 8.5 to 11 GHz, while its structure length is only 26.16 times wavelength. Measurement results indicate that the S21 of the bend is about −0.4 dB from 8.5 to 11 GHz, and it works stably under a microwave output power of 1 MW. The consistency between theoretical calculations, simulation, and experiments indicates the feasibility of this novel TE01 bend. [ABSTRACT FROM AUTHOR]

The oversized TE11 mode bend is able to make the transmission direction of electromagnetic wave to turn 90°, and it is one of the key components in the high‐power microwave system. The mode coupling characteristics between the TE11 and parasitic modes under two different polarisations in the bending waveguide are analysed, and it is found that the TE11 suffers less interferences from parasitic modes when its polarisation direction is perpendicular to the bending plane, and the corresponding 90° TE11 bend is easier to realise high performance. To verify this analysis, an oversized 90° TE11 bend waveguide working at 10 GHz is designed, and its structural length is only 7.5 times the central working wavelength. Simulated results indicate that its relative bandwidth is 15.6% when the transmission efficiency is over 98%, and its maximum power handling capacity reaches 5.6 GW at short microwave pulse duration (less than 100 ns). The S‐parameters indicate that its S21 is about −0.1 dB from 9.5 to 10.5 GHz, and its S11 is under −25 dB in the same frequency range. Meanwhile, the high power test indicates that the bend works stably when the injected power is 3 GW. [ABSTRACT FROM AUTHOR]

Mode converter is one of the most important devices in the high-power microwave (HPM) applications. To conduct an in-depth research for the orthogonal mode converter, a novel 90° compact TM01-TE11 circular waveguide converter working at 9.7 GHz is proposed in this article. This design innovatively integrates the traditional mode converter with 90° bend techniques based on the mode coupling theory, which ensures a compact structure and high-power handling capacity. Calculated and simulated results illustrate that the maximum conversion efficiency of the converter at central frequency reaches 99.4% when the structure length is 535 mm, and the bandwidth reaches 680 MHz when the conversion efficiency exceeds 95%. For demonstration, a prototype is fabricated, and the corresponding experiments are investigated. According to the $S$ -parameter measurement, it has a high conversion efficiency at central frequency. Meanwhile, the high-power performance is conducted by connecting it with a relativistic backward oscillator (RBWO), and the converter works stably under a maximum output power of 4 GW. The good agreement of the theoretical analyses, simulations, and experimental results indicates the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

A compact L-band relativistic magnetron (RM) with the diffraction output (DO) of the TEM mode is proposed. In this DO configuration, a ridged circular waveguide is used to replace the cylindrical waveguide to decrease its radial dimension. The RF field of the operating π-mode is extracted from every resonator cavity and guided to the ridged circular waveguide. Even at the operating frequency of 1.55 GHz, the ridged circular waveguide can reduce the cutoff radius of the RF wave to 73 mm. The output RF field is further effectively converted to the TEM mode by a compact mode converter. Moreover, in the resonant system, a 10-cavity rising-sun slow wave structure (SWS) is applied to lower the phase velocity of the operating spatial harmonic and enhance the mode separation between the operating mode and the adjacent mode. The particle-in-cell (PIC) simulations demonstrate that the practical RM could output a relatively pure TEM mode at the frequency of 1.55 GHz, and its total efficiency is up to 60% with gigawatt radiation power for a diode voltage of 400 kV. [ABSTRACT FROM AUTHOR]

The talc-filled ABS compounds were prepared by melt blending, and the effects of talc content and size as well as lubrication on their weld line strength were investigated. The micro-morphology of the interface between weld line and dispersed fillers was observed with scanning electron microscope. The results indicated that the weld line strength of the compoundsdecreased due to the barrier effect on diffusion and fusion of macromolecular chains by talc sheets. Theweld line strength of ABS could be improved effectively by incorporation of talc at a low content, mixture of talc and wollastonite, or amide lubrication with polar groups. The ABS compounds achieved the weld mark strength of 33. 4 MPa when 5 wt % of talc, 5 wt % of wollastonite and 1 wt %of modified amide lubrication were added. [ABSTRACT FROM AUTHOR]

Abstract: Pt2Sn1 nanoparticles supported on wormholelike mesoporous carbons (WMCs) with three different pore diameters, namely WMC-F7, WMC-F30, and WMC-F0 have been synthesized by adopting a modified pulse microwave-assisted polyol method. The pore diameters (Dp) of WMC-F7, WMC-F30, and WMC-F0 are 8.5 nm, 4.4 nm, and 3.1 nm respectively, while the particle size of Pt2Sn1 (DPt) on each support is identical (∼3 nm). Based on the experimental results, it has been found that the pore diameter plays an important role in the electrochemical activity of Pt2Sn1 catalysts towards ethanol electrooxidation reaction (EOR). Pt2Sn1/WMC-F7 catalyst exhibits the highest electrochemical surface area (ESA) and activity towards EOR. Moreover, Pt2Sn1/WMC-F7 gives the comparable activity to the Pt2Sn1 supported on the commercial XC-72 carbon. However, in the cases of WMC-F30 (DPt < Dp < 2 DPt) and WMC-F0 (Dp = DPt) as the supports, the corresponding catalysts obtain much lower ESA and EOR activity with respect to WMC-F7 (Dp > 2 DPt). This could be attributed to the easy accessibility of Pt2Sn1 nanoparticles in the case of WMC-F7 with Dp > 2 DPt for the easy fuel transportation, and consequently the EOR activity has been greatly improved. [Copyright &y& Elsevier]