China Academy of Engineering Physics

About: China Academy of Engineering Physics is a facility organization based out in Mianyang, China. It is known for research contribution in the topics: Laser & Microstructure. The organization has 14158 authors who have published 12055 publications receiving 115810 citations. The organization is also known as: Ninth Institute of Second Ministry of Mechanical Industry & Ninth Institute of Ministry of Nuclear Industry.

Thermal drift analysis using a multiphysics model of bulk silicon MEMS capacitive accelerometer

Abstract: An interpretation of the thermal drift of the bulk silicon MEMS capacitive accelerometer using multiphysics analysis is proposed in this paper. Stress, strain, electrostatics, thermal and structural interactions are simulated based on the finite element method. The thermal drift is generated by both the stiffness asymmetry of the U-springs of the structure and relative displacement caused by the mismatch in thermal expansion coefficients between the Pyrex glass substrate and heavily boron-doped silicon structure, neither of which is dispensable. Although the layout design is symmetrical, the asymmetric widths of the U-springs, which cause stiffness asymmetry, are observed by scanning electron microscopy. To achieve a fast and feasible simulation, we divide the model into two components with different configurations. During the simulation, boundary conditions are carefully set up according to the fabrication process. A series of experiments is designed to verify the result, including a temperature experiment from −40 to 100 °C and DC voltage polarity experiment. To verify the conclusion, a new layout design that gradually increases the width of the U-springs without changing any other dimension is simulated, fabricated, and tested. The simulation and experiment results are compared and discussed.

High temperature resistant polyimide/boron carbide composites for neutron radiation shielding

Abstract: Boron carbide (B4C) is an important type of neutron radiation shielding material with relatively high efficiency due to the high content of 10B element. Incorporation of B4C particles into polymer to prepare high-performance neutron radiation shielding material has become more and more important for the safe operation of nuclear power in the defense industry and nuclear power plant. The polyimide/B4C composite films with different micro-sized B4C contents were successfully prepared by in-situ polymerization. Silane coupling agent KH550 was employed to functionalize B4C particles to improve the dispersion of B4C particles in the polyimide matrix with strengthened interfacial interaction. As shown that the micro-sized B4C functional particles can be well dispersed in the BPDA/ODA polyimide matrix. With the B4C content increase, thermal stability of the polyimide/B4C composite films can be significantly improved, even mechanical properties partly declined. Meanwhile, the polyimide/B4C composite films exhibit good thermal neutron radiation shielding properties. The neutron permeability I/I0 changes exponentially with the change of B4C content. When the B4C content is increased to 30 wt%, the polyimide/B4C composite films show optimum properties combination with thermal decomposition temperature (Td10) of 622 °C, neutron permeability (I/I0) of 0.24 (800 μm in thickness), and tensile strength of 406 MPa. The composite thus shows great potential for use in applications which require materials with high thermal stability and neutron radiation shielding ability, such as fusion reactor system and nuclear waste disposal.

Nonlinear, Active, and Tunable Metasurfaces for Advanced Electromagnetics Applications

Abstract: We demonstrate a series of nonlinear, active, and tunable metasurfaces for a variety of electromagnetic applications. The metasurfaces have achieved a range of exotic properties by populating nonlinear or active circuit components on a periodically patterned metallic surface. The circuit components such as diodes, varactors, transistors, and other devices can be controlled manually, actively, or self-adaptively. This allows nonlinear metasurfaces to have active tuning, power-dependent behavior, self-focusing, reconfigurable surface topology, or frequency self-tuning capabilities. The power-dependent metasurfaces can be applied to active RF absorbers that only absorb high-power surface waves to prevent malfunction or damages to sensitive devices. The rectifier-based waveform-dependent metasurface absorber can be specifically designed to absorb either high power pulsed waves or continuous waves. The transistor-based surface wave metasurface absorber provides another degree of freedom in that it can be manually switched to tune the absorber, or it can be tuned using computer controlled feedback. The self-focusing effect has been demonstrated for the first time at RF frequencies to automatically collimate high-power surface waves. The reconfigurable and self-tuning metamaterial surfaces can be implemented to support a broadband reconfigurable antenna system or to adapt to a wide range of incoming frequencies. In this paper, the concepts of nonlinear and active tunable metasurfaces are discussed, including results of full-wave simulation analysis, EM/circuit co-simulation, and experimental results in waveguides, using a near-field scanner, as well as far-field measurements in an anechoic chamber.

On the failure load and mechanism of polycrystalline graphene by nanoindentation

Abstract: Nanoindentation has been recently used to measure the mechanical properties of polycrystalline graphene. However, the measured failure loads are found to be scattered widely and vary from lab to lab. We perform molecular dynamics simulations of nanoindentation on polycrystalline graphene at different sites including grain center, grain boundary (GB), GB triple junction, and holes. Depending on the relative position between the indenter tip and defects, significant scattering in failure load is observed. This scattering is found to arise from a combination of the non-uniform stress state, varied and weakened strengths of different defects, and the relative location between the indenter tip and the defects in polycrystalline graphene. Consequently, the failure behavior of polycrystalline graphene by nanoindentation is critically dependent on the indentation site, and is thus distinct from uniaxial tensile loading. Our work highlights the importance of the interaction between the indentation tip and defects, and the need to explicitly consider the defect characteristics at and near the indentation site in polycrystalline graphene during nanoindentation.