查看更多>>摘要：The dynamic microstructure and texture of dilute Mg-0.50Al-0.71Ca-0.33Mn(wt.％)during hot rolling at two slab temperatures were investigated by electron backscattered diffraction(EBSD)and high resolu-tion transmission electron microscopy(HRTEM).The results show that the development of the rolling microstructures is to first form{10-12}extension twins in the original grains,thereby forming the extension-twinned regions,and then to further form{10-11}-{10-12}double twins and kinks in the extension-twinned regions,and finally to form continuous dynamic recrystallized(continuous DRXed)grains in the double twins and the cross parts of the shear-deformed coarse extension-twinned regions.These extension twins,double twins and kinks show a decisive effect on the formation of rolling texture.The number of{10-11}-{10-12}double twins and resultant the continuous DRX process are strongly affected by the rolling slab temperature and the reduction thickness per pass.By optimizing the rolling conditions,texture and microstructures of the multi-pass rolled Mg-Al-Ca-Mn alloy sheets are success-fully modified.Although the total alloy content is only 1.5 wt.％,these Mg-Al-Ca-Mn alloy sheets show much higher strength than the commercial Mg-3Al-1 Zn(wt.％)(AZ31B)sheet.
查看更多>>摘要：At present,the problem of electromagnetic wave(EMW)pollution is critical,and the design of high-performance absorbers is of great significance.Based on the synergy between dielectric and magnetic losses,and between multicomponents in heterostructures,the development of light-weight absorbers with a strong absorption capability and multiple scattering is a promising strategy to achieve high-performance absorbers.In this work,CoFe-MOF precursors with a bouquet-like structure were prepared via the hydrothermal method,and Co7Fe3/C and Co9S8/Fe/CoS2/C composites were obtained through a carbonization and sulfuration treatment during the high-temperature pyrolysis process,respectively.The experimental and theoretical results show that the Co9S8/FeCoS2/C composite has a better EMW absorp-tion performance,and its optimal reflection loss(RL)value is-53.9 dB at a low filler loading of 20 wt.％,which is due to the S doping that enhances the interface polarization relaxation process and improves the impedance matching characteristics.Moreover,the Co9S8/FeCoS2/C composite can be as candidates of high-efficiency absorbers in extreme application environments.
查看更多>>摘要：Black phosphorus(BP),as one of the most promising fillers for flame retarding polymer,has been seri-ously limited in practical application,due to the agglomeration and poor structural stability challenges.Here,the BP was modified by MXene and polydopamine(PDA)via ultrasonication and dopamine mod-ification strategy to improve the structural stability and dispersibility in the matrix.Then,the obtained(BP-MXene@PDA)nanohybrid was employed to promote the mechanical performance,thermal stability,and flame retardancy of thermoplastic polyurethane elastomer(TPU).The resultant TPU composite con-taining 2 wt.％of BP1-MXene2@PDA showed a 19.2％improvement in the tensile strength and a 13.8％increase in the elongation at break compared to those of the pure TPU.The thermogravimetric analysis suggested that BP-MXene@PDA clearly enhances the thermal stability of TPU composites.Furthermore,the introduction of the BP-MXene@PDA nanohybrids could considerably improve the flame retardancy of TPU composite,i.e.,64.2％and 27.3％decrease in peak heat release rate and total heat release,respec-tively.The flame-retardant mechanisms of TPU/BP-MXene@PDA in the gas phase and condensed phase were investigated systematically.This work provides a novel strategy to simultaneously enhance the fire safety and mechanical properties of TPU,thus expanding its industrial applications.
查看更多>>摘要：Inspired by the lotus leaf effect,non-wetting artificial superhydrophobic surfaces demonstrate an enor-mous potential in numerous fields.However,limited by poor stability and durability,superhydrophobic surfaces are rarely available for practical applications.In this review,based on the wettability mechanisms and failure modes of superhydrophobic surfaces,it is proposed that the construction of highly stable superhydrophobic materials can be approached from four aspects,including structural design,chemical bonding,interfacial-strengthening of hydrophobic materials and substrates,and self-healing.We intro-duced in detail the design ideas,strengthening approaches,and characterization tools of highly stable su-perhydrophobic materials from the perspective of multi-strategy design and strengthening,and provided corresponding insights.Eventually,the development,current status,and prospects of highly stable and multifunctional superhydrophobic materials were also presented in detail.Recent advances and develop-ment prospects of durable superhydrophobic materials were summarized and discussed in this review,providing certain insights and design guidelines for the fabrication of stable superhydrophobic materials.
查看更多>>摘要：The presence of chloride ions is the critical factor of passivity breakdown of the protective film and even-tually leads to localized corrosion.However,the mechanism and the role of chlorides in these processes are still controversial.Hematite and chromia are generally believed to be the major components of outer and inner oxide layers on stainless steels.In the present paper,a comparative study of Cl ingress into pristine and defective α-Fe2O3(0001)surface,α-Cr2O3(0001)surface,along with their interface,was conducted using density functional theory.Vacancy formation energy calculation confirms good stability of α-Cr2O3 and high reactive activity of the interface region.Cl inserts into an O vacancy is energetically more favorable than Fe vacancy and interstitial site,demonstrating Cl-induced degradation complies with the ion exchange model.Transition state search for Cl diffusion through O vacancies shows α-Cr2O3 is more protective than α-Fe2O3,while the interface region is the weak point of the duplex passive film.
查看更多>>摘要：Spontaneous growth of metal whiskers,represented by tin whiskers,has haunted tin-based platings and solder joints for decades and caused huge losses to the electronics industry.Despite numerous efforts,the underlying growth mechanism has been resisting interpretation,and the whiskering phenomenon even continues to expand its territory.Here,we report the growth of tin whiskers from a Ti6Sn5 intermetallic.These tin whiskers share similar characteristics with those found on the platings or solder joints,but grow more and faster,with finer diameters.After tin whisker growth,Ti6Sn5 retains its crystal structure,implying a dealloying process.Combining experimental and first-principles calculation results,we ana-lyzed the growth mechanism of tin whiskers in detail,and proposed a diffusion-based growth model.The strain energy stored in Ti6Sn5 during deformation provides a driving force for whisker growth,and the short-circuit diffusion paths generated by such deformation accelerate whisker growth.These find-ings identify the critical role of intermetallic substrate in the whiskering phenomenon,shedding new light for comprehensively understanding the whisker growth mechanisms.Furthermore,the plenty and rapid growth of tin whiskers also means a new method for the preparation of one-dimensional metallic materials.
查看更多>>摘要：Radiation-tolerant materials are widely desired in nuclear reactors.High-entropy alloys(HEAs)exhibiting superior mechanical performance and swelling tolerance are being considered as next-generation nuclear structural materials.However,an understanding of HEAs irradiation tolerance at an atomic scale is still lacking.In this study,the atomic scale irradiation response of AlCoCrFeNi2.1,composed of face-centered cubic(FCC)phase and B2 phase,has been systematically investigated at 298 and 723 K.The bubble vol-ume ratio of the B2 phase is much larger than that of the FCC phase under the same irradiation condi-tions,and hence,the FCC phase has superior swelling tolerance than the B2 phase.Also,order-disorder transformation occurred in both L12 and B2 phases.The different irradiation responses between the FCC and B2 phases,depend firstly on composition and secondly on crystal structure.The higher composi-tional complexity and complicated atomic-level lattice environment of the FCC phase contribute to better radiation performance than B2 phase.The results pave a way for exploring radiation-tolerant structural high-entropy alloys.
查看更多>>摘要：An extra-low interstitial near alpha alloy Ti-3Al-2Zr-2Mo(wt％)was fabricated by hydrogenation and thermomechanical consolidation(TMC)of the coarse and spherical pre-alloyed powder with particle sizes of 60 to 270 μm.The coarse powder is a byproduct of pre-alloyed powder produced for selective laser and electron beam additive manufacturing.The TMC process involves powder compaction,fast sintering,in-situ dehydrogenation and an immediate hot extrusion to form a fully dense and fine-grained marten-sitic microstructure.Further dehydrogenation in vaccum at 700℃converted the martensitic microstruc-ture into an interwoven α/β microstructure which exhibited an improved yield strength,apparent neck-ing and premature cracking at grain boundary α(αGB)ribbons.A further annealing of 880℃/1 h/AC led to the formation of a fine-grained α/βt composite structure,which achieved an enhance ultimate tensile strength of 835 MPa and excellent tensile ductility of 16.0％.Analysis of the deformation behavior of the alloy in different states revealed that the α/βt composite structures brought about an enhanced strain hardening capability by heterogeneous deformation effect of hard βt and soft α-laths,which inhibited the formation of microcracks and consequently improved the coordinated deformation.
查看更多>>摘要：We report that the integration of filter membrane and Ca2Nb3O10 nanosheets(FM@CNO)UV photode-tector(UV PD)shows high performance and excellent flexibility.The Ca2Nb3O10 nanosheets were pre-pared by a facile solid-state reaction and liquid exfoliation process.The Ca2Nb3O10 nanosheets can be integrated into the pores of a filter membrane via a simple vacuum filtration method.The FM@CNO UV PD shows high performance under 300 nm light illumination at 5 V bias,including high responsivity(0.08 AW-1),high detectivity(1.1×1012 Jones),high UV/visible rejection ratio(3.86×103)and fast speed(0.12/1.24 ms).Furthermore,the FM@CNO device exhibits excellent flexibility after many bending cycles.In addition,the FM@CNO array device was used as a pixel array detector for UV imaging.This work provides a novel approach to achieve high performance flexible PDs based on filter membrane and two dimensional materials.
Timothy Alexander ListyawanMaya Putri AgustianingrumYoung Sang NaKa Ram Lim...
115-126页
查看更多>>摘要：Composition modification was introduced to improve the oxidation resistance by varying Al and excluding Co from the Al-Co-Cr-Fe-Ni system.Since adjusting the composition shifted the valence electron concen-tration(VEC)of the alloys,the dual-phase structure of the alloys is expected to be more stable.At low temperatures(T＜1273 K),the alloys formed mixed oxide products.As oxidation temperature increased,only Cr2O3 or Al2O3 dominated the alloy's surface.Compared to equiatomic AlCoCrFeNi(5-Equi),non-equiatomic AlCoCrFeNi(5-B 40)and four-component AlCrFeNi(4-B 2013)had better oxidation resistance due to monocrystalline-Al2O3 formation.Besides the role of oxide formation,maintaining BCC and B2 phases within the alloys is also beneficial to supporting the stable Cr2O3 or Al2O3.
NETL
NSTL
维普
万方数据