Growth Characteristics and Kinetics of Niobium Carbide Coating Obtained on AISI 52100 by Thermal-reactive Diffusion Technique

Niobium carbide coating was produced by thermal-reactive diffusion technique on AISI 52100 steel in salt bath at 1 123 K, 1 173 K, and 1 223 K for 1, 2, 4, and 6 hours. The salt consisted of borax, sodium fl uoride, boron carbide, and niobium pentoxide. The presence of NbC phase on the steel surface was confi rmed by X-ray diffraction analysis. Microscopic observation showed that niobium carbide coating formed on the substrate was smooth and compact. There was a distinct and fl at interface between the coating and substrate. The micro-hardness of niobium carbide coating was 2892±145HV. The thickness of coating ranged from 1.6 μm to 14μm. The forming kinetics of niobium carbide coating was revealed. Moreover, a contour diagram derived from experimental data was graphed for correct selection of process parameters. Some mathematical equations were built for predicting the coating thickness with predetermined processing temperature and time. The results showed that these mathematical equations are very practical as well as the kinetics equation.

Static and Dpoamic Coarsening of Niobium Carbide in HSLA Steel

An experinientally quantitative inveetisation has been made on the precipitationand coarsening behaviors of niobium carbide in a high strength low alloy(HSLA) steel. The results suggest that the static coarsening processes duringisothermal reaction in (α+γ) two phase region and during isothermal stay aftercertain amount of deformation of austenite are principally controlled by thediffusion of niobium atoms along dislocation pipes, and the volume fraction ofthe precipitates exerts sisnificant influence on the coarsening processes.Whereas the dynamic coarsening process during hot deformation of austeniteappoars to be dominated by the carbide/matrix interphase reaction.

Effect of Rare Earths on Precipitation Kinetics of Niobium Carbide in Microalloyed Steel

The effects of rare earths on precipitation of NbC in austenite and ferrite have been investigated. The results show that precipitation of NbC is promoted in ferrite but retarded in austenite. The fit to different models by using the least square technique indicates that the addition of RE changes the rate constant of precipitation rather than the kinetic mechanism of precipitation.

Niobium carbide(MXene)reduces UHMWPE particle-induced osteolysis

Joint replacement surgery is one of the orthopedic surgeries with high successful rates;however,wear debris generated from prostheses can ultimately lead to periprosthetic osteolysis and failure of the implant.The implant-derived particulate debris such as ultrahigh molecular weight polyethylene(UHMWPE)can initiate the local immune response and recruit monocytic cells to phagocytose particles for generating reactive oxygen species(ROS).ROS induces osteoclastogenesis and macrophages to secrete cytokines which ultimately promote the development of osteolysis.In this work,we develop the few-layered Nb_(2)C(FNC)as an antioxidant which possesses the feature of decreasing the production of cytokines and inhibiting osteoclastogenesis by its ROS adsorption.Moreover,local injection of FNC attenuates the UHMWPE-induced osteolysis in a mouse calvarial model.In sum,our results suggest that FNC can be used for treating osteolytic bone disease caused by excessive osteoclastogenesis.

Microstructure and magnetostrictive performance of NbC-doped <100>oriented Fe-Ga alloys

The〈100〉oriented Fe83Ga17 alloy rods with various NbC contents less than 1at%were prepared by the directional solidification method at a growth rate of 720 mm·h^-1. Low NbC-content was found to affect the oriented grain growth and slightly improve the〈100〉ori-entation. Flat grain boundaries in the alloys with low NbC contents less than 0.2at%became greatly curved at higher NbC contents, and a large amount of Nb-rich precipitates were observed in the alloys with high NbC contents. Small amounts of NbC, less than 0.2at%, resulted in an increase in magnetostrictive strain due to the improvement of the〈100〉orientation, and a high magnetostrictive strain value of 335 ×10^-6 under a pre-stress of 15 MPa was obtained in the 0.1at%NbC-doped alloys. The magnetostrictive performance obviously decreased with the NbC addition higher than 0.5at%, and the strain sensitivity under no pre-stress was lower than that in the binary Fe？Ga alloy.

基于二维Nb_(2)C的纳米平台增强声动力抗菌治疗并促进骨修复

快速消除感染和促进骨再生是骨髓炎临床治疗的两个关键环节.当前迫切需要开发高效的生物活性声敏剂用于声动力治疗(SDT).在此,我们设计了一种二维Nb_(2)C纳米片修饰的卟啉基金属有机框架纳米平台(HNTM/Nb_(2)C)用于在超声辐照下同时消除感染和加速骨再生.通过在HNTM和Nb_(2)C纳米片之间构建肖特基结,实现了超声辐照下快速的电荷转移并抑制电子-空穴对的重组,从而产生丰富的活性氧.这种新型的声敏剂可以加速干细胞向成骨细胞的分化.RNA测序表明,该HNTM/Nb_(2)C纳米平台通过阳离子释放及超声响应电流引起的ATP合成耦合的电子传递诱导干细胞分化.此外,KEGG通路富集分析表明,Nb离子可能通过激活Wnt信号通路进一步促进成骨.我们的研究为骨髓炎的高效SDT提供了新的策略,该策略通过声响应电流联合离子疗法,实现了感染的消除同时促进了骨再生.