Low-temperature sintering behaviour and ferroelectric properties of lead zirconate titanate (PZT95/5) ferroelectric (FE) ceramics doped with CdO were investigated. The addition of CdO significantly promoted the densification and decreased the sintering temperature of PZT95/5 ceramic. When the addition of CdO content is 1 mol-%, PCZT95/5 ceramics with a relative high density of approximately 97.5% can be obtained by sintering at 1100°C and exhibits excellent electric properties with d 33 values of 65 pC/N, this d 33 value is close to that of PZT95/5 ceramic sintered at 1350°C. With an increase in the CdO content, the FE phase content decreases and the antiferroelectric (AFE) phase content increases gradually. When the CdO content is 2 mol-%, the most of FE phase of PCZT 95/5 ceramics changes to AFE phase, the polarisation value is quite small and the d 33 value drops to zero.

Abstract. Effect of the addition of carbon on the sintering properties of pressureless sintered boron carbide ceramics was investigated by using carbon black and phenolic resins as the main additives. There were three ways for adding Carbon, carbon black adding, phenolic resins adding and adding carbon black and phenolic resins mixtures . The density and microstructure of sintered B 4 C ceramics were analyzed by densitometer and optical microscope respectively. The effect on the densification of B 4 C ceramics by different content and adding method of carbon were analyzed and summarized. The results showed that the B 4 C ceramics has the optimum properties, that bulk density , bending strength, hardness and fracture toughness achieve 2.42g/cm 3 ,335MPa,22Gpa and 3.17 Mpa•m 1/2 , respectively under the adding the mixture of 5.5%, carbon black and 1.5%, phenolic resins.

To improve the safety of cyclotetramethylenetetranitramine (HMX) particles, the polymer thermoplastic polyurethane elastomer (TPU) and nitrocellulose (NC) were introduced to coat HMX powder by water-solution suspension method and internal solution method, respectively. Scanning electron microscope (SEM) and X-ray photo-electron spectrometry (XPS) were employed to characterize the HMX samples and the role of NC and TPU in the coating processes were discussed. The impact sensitivity, friction sensitivity, and the thermal decomposition of coated HMX particles were investigated, and compared to the unprocessed ones. The results indicate that both TPU and NC can improve the wetting ability of the coating materials on HMX surface and reinforce the connection between HMX and the coating materials. The impact sensitivity and friction sensitivity of HMX samples decrease obviously after they have been surface coated; the drop height (H50) is increased from 35.24 cm to 50.08 cm, and the friction probability is reduced from 93.2 % to 58.3%. The activation energy (Ea) and the self-ignition temperature increase by 10.46 KJ·mol-1 and 1.8, respectively.

Titanium alloys are widely used in aerospace, chemical engineering and medicine because of their excellent tensile, fatigue strength and corrosion resistance. For aerospace titanium alloys, fatigue performance is an important parameter, especially as a structural material. Welding is an indispensable method. After welding, there is a large unevenness in the structure and mechanical properties of the welded joint. Fatigue performance also has a profound effect. This article has done a deep research on the fatigue performance of titanium alloy welded streets, using ANSYS software to calculate and analyze the stress concentration of welded joints, observe and analyze the welding defects on fatigue fractures, and discuss the effect of welding defects on fatigue behavior The equivalent residual stress after spot welding at the center of the joint weld obtained by conventional laser welding near the welding end position is 547 MPa, of which the longitudinal residual stress along the weld direction is tensile stress, the magnitude is 482 MPa, and the transverse direction perpendicular to the weld direction The residual stress is a compressive stress of 114.0 MPa, and the equivalent residual stress of the weld is reduced after the use of SGCW technology. The equivalent residual stress at this point is reduced to 489 MPa, which is a reduction of nearly 12%.

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