Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by the conventional solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of BST perovskite pha...Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by the conventional solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of BST perovskite phase structure besides some calcium oxide peaks for samples with high Ca content, x. Scanning electron microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy dispersive X-ray (EDX) analysis verified the increase of the amount of Ca element with increasing of its content. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz frequency. Investigations of ceramic microstructures and mechanical properties showed their dependence on composition. Increasing of Ca content resulted in a decrease in bulk density and ultrasonic attenuation and an increase in porosity, velocity, and modulus. High temperature ultrasonic studies showed, in addition to Curie phase transition, three or more relaxation peaks and its origin was investigated.展开更多
Continuously improving the performance of satellite antennas has always been one of the goals in the field of antennas.However,the contradiction between the payload volume and mass of the launch vehicle and the antenn...Continuously improving the performance of satellite antennas has always been one of the goals in the field of antennas.However,the contradiction between the payload volume and mass of the launch vehicle and the antenna size makes achieving this goal challenging.In this article,we propose a deployable helical antenna that can be mounted on a CubeSat.It achieves controllable deployment and retraction of a largesized helical antenna using bistable composite slit tube(BCST)and enhances the overall stiffness of the antenna after deployment using tensioned strings.Compared to existing spaceborne helical antennas,the larger deployment size improves the gain the antenna can provide,while the smaller stowage volume allows it to be carried on a CubeSat.Then,the structural performance of the antenna is analyzed,and the results show that this design susbstantially enhances the structural stiffness of the antenna,achieving a fundamental frequency of 6.87 Hz.It also reduces the deformation of the antenna,minimizing performance fluctuations caused by disturbances.This design enables a 2-m helical antennas to be installed on small satellites,expanding the use cases for helical antennas.Moreover,this controllable deployment method allows the helical antenna to achieve additional functionalities.展开更多
文摘Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by the conventional solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of BST perovskite phase structure besides some calcium oxide peaks for samples with high Ca content, x. Scanning electron microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy dispersive X-ray (EDX) analysis verified the increase of the amount of Ca element with increasing of its content. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz frequency. Investigations of ceramic microstructures and mechanical properties showed their dependence on composition. Increasing of Ca content resulted in a decrease in bulk density and ultrasonic attenuation and an increase in porosity, velocity, and modulus. High temperature ultrasonic studies showed, in addition to Curie phase transition, three or more relaxation peaks and its origin was investigated.
基金supported by the National Natural Science Foundation of China(no.U2241247)the Civil Aerospace Technology Research Project(D030206)+3 种基金the Open Project of Yunnan Precious Metals Laboratory Co.Ltd.(YPML-20240502031)the Academician Expert Workstation of Yunnan(no.202305AF150170)the Fundamental Research Funds for the Central Universities(no.QTZX24002)the Natural Science Basic Research Program of Shaanxi(program no.2022JC-DW-01).
文摘Continuously improving the performance of satellite antennas has always been one of the goals in the field of antennas.However,the contradiction between the payload volume and mass of the launch vehicle and the antenna size makes achieving this goal challenging.In this article,we propose a deployable helical antenna that can be mounted on a CubeSat.It achieves controllable deployment and retraction of a largesized helical antenna using bistable composite slit tube(BCST)and enhances the overall stiffness of the antenna after deployment using tensioned strings.Compared to existing spaceborne helical antennas,the larger deployment size improves the gain the antenna can provide,while the smaller stowage volume allows it to be carried on a CubeSat.Then,the structural performance of the antenna is analyzed,and the results show that this design susbstantially enhances the structural stiffness of the antenna,achieving a fundamental frequency of 6.87 Hz.It also reduces the deformation of the antenna,minimizing performance fluctuations caused by disturbances.This design enables a 2-m helical antennas to be installed on small satellites,expanding the use cases for helical antennas.Moreover,this controllable deployment method allows the helical antenna to achieve additional functionalities.
