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Silicon carbide nanofiber/silicon carbide (SiCnf/SiC) composites with a laminar stacking structure were prepared by the slurry impregnation hot‐press sintering using aluminum (Al) powder, boron (B) powder, and carbon black as sintering aids. SiCnf paper was fabricated using nanofibers and impregnated with the slurry of SiCnp and sintering aids, and the SiCnf/SiC preforms were fabricated by the alternating stack of the SiCnf paper and SiCnp. The pyrolysis carbon and boron nitride interface layers were deposited on the surface of SiCnf by chemical vapor deposition and vacuum impregnation‐pyrolysis methods. The effects of different sintering temperatures on the relative density, porosity, sectional microscopic morphology, and mechanical properties of the composites were investigated. The results show that the fracture toughness of SiCnf/SiC composites is significantly improved. The mechanical properties of the composites were optimized at a sintering temperature of 1950°C and a sintering pressure of 30 MPa, with flexural strength and fracture toughness of 548 MPa and 15.86 MPa·m1/2, respectively. The liquid phase Al8B4C7 compound generated at the high temperature promoted the densification of the composites. [ABSTRACT FROM AUTHOR]

This paper presents a picowatt voltage reference circuit using a voltage regulation scheme consisting of a self-regulation native N-type transistor, a double regulation topology formed by a stacked structure of two native N-type transistors, and a P-type transistor-based self-biased current source, to feed a diode-connected P-type load and a PNP transistor load. This improves the line sensitivity and the power supply rejection ratio (PSRR) without the use of an on-chip capacitor. The circuit is designed in a 180 nm CMOS process with an area of 13,700 μm2 and operates with a minimum supply voltage of 0.8 V. Post layout simulation results show that the circuit provides a constant output voltage of 160.2 mV with a temperature coefficient (TC) of 151.6 ppm/ ∘ C from 0 to 100 ∘ C, a line sensitivity of 0.00114%/V, a PSRR of - 72.6 dB at 100 Hz, and an untrimmed voltage accuracy ( σ / μ ) of 0.99%. [ABSTRACT FROM AUTHOR]

SiC nanofibers preforms with different volume fraction of nanofibers were fabricated by the different molding pressures. SiC nanofiber-toughened SiC ceramic matrix composites were prepared by the combined processes of precursor infiltration and pyrolysis with reactive melt infiltration. The effect of molding pressure on the structure and properties of SiC ceramic matrix composites was investigated. Results show that the preforms with high volume fraction of SiC nanofibers can be fabricated by compression molding. When the molding pressure is 40 MPa, the volume fraction of SiC nanofibers is 22.13%. However, there exists the fracture of SiC nanofibers if the molding pressure is too high. The porosity of the composites prepared by the combined processes of precursor infiltration and pyrolysis with reactive melt infiltration is much lower than that by the simple process of precursor infiltration and pyrolysis. The average porosity of the composite materials prepared by these two methods is 1.43% and 14.19%, respectively. When the molding pressure is 30 MPa, the composites have low content of free silicon and the long SiC nanofibers have high length-diameter ratio. Meanwhile, the corresponding value of the bending strength and fracture toughness of the composites is 178 MPa and 21.6 MPa ⋅ m², which is the largest under the different molding pressures. [ABSTRACT FROM AUTHOR]