Bacteriostatic Effect of Extracts from 10 Kinds of Traditional Chinese Medicinal Materials and Garlic on Pectobacterium chrysanthemi

Pectobacterium chrysanthemi is one of the main pathogens of soft rot disease of Amorphophallus konjac.The bacteriostatic effect of extracts from 10 kinds of traditional Chinese medicine and garlic on Pectobacterium chrysanthemi was studied in this experiment.The results showed that the extracts of Coptis chinensis,garlic,Scutellaria baicalensis,Mume Fructus and Bupleurum had significant bacteriostatic effect.Among them,Coptis chinensis and garlic had the best bacteriostatic effect on Pectobacterium chrysanthemi,and the diameter of inhibition zone was 2.27 and 2.19 cm,respectively,followed by Scutellaria baicalensis,with the diameter of inhibition zone of 1.68 cm.The extracts of Coptis chinensis,Scutellaria baicalensis and garlic with good bacteriostatic effect were diluted by double dilution method,and the bacteriostatic effect was determined.The results showed that 2-fold dilution of Coptis chinensis and 2-fold and 4-fold dilution of Scutellaria baicalensis had significant bacteriostatic effect,but the bacteriostatic effect of garlic extract was not obvious after dilution.

Effects of in-situZrB_2 nanoparticles and scandium on microstructure and mechanical property of 7N01 aluminum alloy

In this study, the in-situ synthesized ZrB_(2) nanoparticles and rare earth Sc were introduced to enhance the strength and ductility of 7N01 aluminum alloy, via the generation of high-melting and uniform nanodispersoids. The microstructure and mechanical property evolution of the prepared composites and the interaction between ZrB_(2) and Sc were studied in detail. The microstructure investigation shows that the introduction of rare earth scandium(Sc) can promote the distribution of ZrB_(2) nanoparticles, by improving their wettability to the Al melt. Meanwhile, the addition of rare earth Sc also modifies the coarse Al Zn Mg Mn Fe precipitated phases, refines the matrix grains and generates high-melting Al_3(Sc,Zr)/Al_3Sc nanodispersoids. Tensile tests of the composites show that with the combinatorial introduction of ZrB_(2) and Sc, the strength and ductility of the composites are improved simultaneously compared with the corresponding 7N01 alloy, ZrB_(2) /7N01 composite and Sc/7N01 alloy. And the optimum contents of ZrB_(2) and Sc are 3 wt% and 0.2 wt% in this study. The yield strength, ultimate strength and elongation of(3 wt% ZrB_(2) +0.2 wt% Sc)/7N01 composite are 477 MPa, 506 MPa and 9.8%, increased about 18.1%, 12.2%and 38% compared to 7N01 alloy. Furthermore, the cooperation strengthening mechanisms of ZrB_(2) and Sc are also discussed.

High strength and high creep resistant ZrB2/Al nanocomposites fabricated by ultrasonic-chemical in-situ reaction

In this study, the ZrB2/Al nanocomposites were fabricated via in-situ reaction of the Al-K2ZrF6-KBF4 system, assisted with ultrasonic vibration and spiral electromagnetic stirring. Microstructure, tensile property and creep behavior of the fabricated nanocomposites were further investigated. Microstructure observation showed that the ultrasonic vibration could prevent the fast growth as well as break the clusters of in-situ synthesized nanoparticles in melt, resulted in smaller size (10-50 nm) and relatively more uniform distribution of the in-situ nanoparticles located on the boundary of and/or inside the aluminum matrix grains in the final composites. The fabricated nanocomposites exhibited an enhancement in both strength and ductility, due to the elevated work hardening ability, i.e., improved dislocation propagating ability and decreased dynamic recovery of the existing dislocations induced by the in-situ nanoparticles. Meanwhile, the nanocomposites exhibited excellent creep resistance ability, which was about 2-18 times higher than those of the corresponding aluminum matrix. The stress exponent of 5 was identified for the fabricated nanocomposites, which suggested that their creep behavior was related to dislocation climb mechanism. The enhanced creep resistance of the nanocomposites was attributed to the Orowan strengthening and grain boundary strengthening induced by the ZrB2 nanoparticles. Thus, the ultrasonicchemical in-situ reaction promises a low cost but effective way to fabricate aluminum nanocomposites with high strength and high creep resistance.