Synthesis and characterization of high entropy (TiVNbTaM)2AlC (M = Zr, Hf) ceramics

The high-entropy design of MAX phases is expected to confer superior properties, but its study was hindered by the complex synthesis method and limited purity of samples. In this work, two noteworthy types of high-entropy MAX phase structural ceramics, high-entropy (TiVNbTaM)2AlC (M = Zr, Hf), were designed and prepared by the in-situ synthesis using spark plasma sintering (SPS). The microstructure and lattice parameters of sintered samples were determined. Compared with the single-component MAX phases, the highly pure high-entropy (TiVNbTaZr)2AlC sample had good physical and mechanical properties, including electrical conductivity of 0.96×106 Ω−1·m−1, thermal expansion coefficient of 3.65×10−6 K−1, thermal conductivity of 8.98 W·m−1·K−1, Vickers hardness of 9.80 GPa, flexural strength of 507 MPa, fracture toughness of 5.62 MPa·m1/2, and compressive strength of 1364 MPa, which exhibited the remarkable hardening-strengthening effect

MACHINABILITY AND REMOVAL MECHANISM OF METAL-BASED SUPPORT STRUCTURES IN SELECTIVE LASER MELTING

Ph.DDOCTOR OF PHILOSOPHY (CDE-ENG

Molluscicidal activity and physiological toxicity of quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits on Oncomelania hupensis.

Schistosomiasis is a serious worldwide parasitic disease. One of the best ways to control schistosomiasis is to control the population of Oncomelania hupensis snails. We sought to identify a high-efficiency biogenic molluscicide against Oncomelania with low toxicity, to avoid chemical molluscicide contamination and toxicity in aquatic organisms. We extracted quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits. Molluscicidal activity of the QBAs against Oncomelania was determined using bioassay. Our results showed that the extracted QBAs had a strong molluscicidal effect. In treatment of O. hupensis with QBAs for 48 h and 72 h, the lethal concentration (LC50) was 2.89 mg/L and 1.29 mg/L, respectively. The molluscicidal activity of QBAs was close to that of niclosamide (ethanolamine salt), indicating that QBAs have potential development value as novel biogenic molluscicides. We also analyzed physiological toxicity mechanisms by examining the activity of several important detoxification enzymes. We measured the effect of the extracted QBAs on the activities of glutathione S-transferase (GST), carboxylesterase (CarE), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the liver of O. hupensis. We found that the effects of QBAs on detoxification metabolism in O. hupensis were time and concentration dependent. The activities of GST, CarE, AKP, and ACP in the liver of snails increased significantly in the early stage of treatment (24 h), but decreased sharply in later stages (120 h), compared with these activities in controls. GST, CarE, AKP, and ACP activity in the liver of snails treated with LC50 QBAs for 120 h decreased by 62.3%, 78.1%, 59.2%, and 68.6%, respectively. Our results indicate that these enzymes were seriously inhibited by the extracted QBAs and the detoxification and metabolic functions of the liver gradually weakened, leading to poisoning, which could be the main cause of death in O. hupensis snails

Support Removal on Thin-Walled Parts Produced by Laser Powder Bed Fusion

10.1089/3dp.2021.02683D PRINTING AND ADDITIVE MANUFACTURIN

A novel method to improve the removability of cone support structures in selective laser melting of 316L stainless steel

10.1016/j.jallcom.2020.157133JOURNAL OF ALLOYS AND COMPOUNDS85