In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substanti...In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substantially accelerates the degradation of alloys at elevated temperatures.Here,a Nb alloy with impressive thermal stability and mechanical properties was designed using theoretical calculations and a two-step graded heat treatment process.The superlative properties of the Nb alloy are primarily associated with the NbC hierarchical structures,i.e.,stable nanoparticles in Nb-BCC grains and discontinuous microparticles at grain boundaries(GBs).The hierarchical carbides configuration avoids continuous precipitation of carbides at GBs and preferential coarsening within the grains.The process involves precipitating ZrC nanoparticles at 1350℃,then stabilizing NbC at 1800℃ by replacing Zr with Nb.Nb-FCC nanophases enveloping NbC prevent coarsening and have strong relationships with both NbC nanoparticles and matrix.The concept of fine-tuning NbC precipitation within grains and introducing NbC at GBs with a substitution method offers a strategy for high-strength,heat-resistant materials.展开更多
The durability performance in molten aluminum with high chemical activity is considered to be a crucial factor for the application of traditional ceramicmatrix composites in the aluminum industry.Herein,novel Ti(C,N)c...The durability performance in molten aluminum with high chemical activity is considered to be a crucial factor for the application of traditional ceramicmatrix composites in the aluminum industry.Herein,novel Ti(C,N)cermet composites with excellent corrosion resistance,featuring distinct ratios of high-entropy alloy binders,were meticulously synthesized by spark plasma sintering(SPS).The synergetic effect of porosity and binder on the corrosion resistance was detailed analyzed.The results show that 8 wt%binder provides an optimum balance of porosity,hardness,fracture toughness and corrosion resistance of the cermets.The appealing corrosion resistance is intimately associated with the formation of a continuous layer consisting of Ti N/Al N,which is introduced through the decarburization of the Ti(C,N)cermets.Additionally,a corrosion mechanism is proposed to elucidate the formation of alternating morphologies within the reaction layers of the cermets.This work is beneficial for selecting structural materials for use in the aluminum industry.展开更多
为探究干燥方式对蛋清蛋白(egg white protein,EWP)功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液(EWPC)相比,喷雾干燥使蛋清蛋白(EWP-P)...为探究干燥方式对蛋清蛋白(egg white protein,EWP)功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液(EWPC)相比,喷雾干燥使蛋清蛋白(EWP-P)的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白(EWP-D)分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D(接触角为65.97°),表明喷雾干燥能显著提高蛋白的疏水性(P<0.05)。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52471025 and 51901252)the Natural Science Foundation of Hunan Province(Grant No.2023JJ30684)the Natural Science Foundation of Changsha Municipal(Grant No.kq2202091).
文摘In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substantially accelerates the degradation of alloys at elevated temperatures.Here,a Nb alloy with impressive thermal stability and mechanical properties was designed using theoretical calculations and a two-step graded heat treatment process.The superlative properties of the Nb alloy are primarily associated with the NbC hierarchical structures,i.e.,stable nanoparticles in Nb-BCC grains and discontinuous microparticles at grain boundaries(GBs).The hierarchical carbides configuration avoids continuous precipitation of carbides at GBs and preferential coarsening within the grains.The process involves precipitating ZrC nanoparticles at 1350℃,then stabilizing NbC at 1800℃ by replacing Zr with Nb.Nb-FCC nanophases enveloping NbC prevent coarsening and have strong relationships with both NbC nanoparticles and matrix.The concept of fine-tuning NbC precipitation within grains and introducing NbC at GBs with a substitution method offers a strategy for high-strength,heat-resistant materials.
基金financially supported by the National Natural Science Foundation of China(No.52271014)the Foundation of Education Bureau of Hunan Province(No.22B0163)Jiangxi Provincial Department of Education(No.GJJ2200819)。
文摘The durability performance in molten aluminum with high chemical activity is considered to be a crucial factor for the application of traditional ceramicmatrix composites in the aluminum industry.Herein,novel Ti(C,N)cermet composites with excellent corrosion resistance,featuring distinct ratios of high-entropy alloy binders,were meticulously synthesized by spark plasma sintering(SPS).The synergetic effect of porosity and binder on the corrosion resistance was detailed analyzed.The results show that 8 wt%binder provides an optimum balance of porosity,hardness,fracture toughness and corrosion resistance of the cermets.The appealing corrosion resistance is intimately associated with the formation of a continuous layer consisting of Ti N/Al N,which is introduced through the decarburization of the Ti(C,N)cermets.Additionally,a corrosion mechanism is proposed to elucidate the formation of alternating morphologies within the reaction layers of the cermets.This work is beneficial for selecting structural materials for use in the aluminum industry.
文摘为探究干燥方式对蛋清蛋白(egg white protein,EWP)功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液(EWPC)相比,喷雾干燥使蛋清蛋白(EWP-P)的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白(EWP-D)分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D(接触角为65.97°),表明喷雾干燥能显著提高蛋白的疏水性(P<0.05)。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。
