查看更多>>摘要：The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation of α-→β in Ti-6Al-4 V alloy under solution treatment have been investigated by the ex-periments and phase field simulations,which reveal the evolutions of microstructure and compositions at the non-equilibrium state and well verify the experimental results.The specific results indicate that the compositions measured through electron probe micro-analysis (EPMA) under a lower heating rate are close to the equilibrium ones corresponding to the solution temperature.Heating up to the target solution temperature,as the heating rate increases,the Al content decreases and V increases in the pri-mary α (αp) grain with a larger size,the volume fraction of αp increases and the composition gradient between αp and β phases gets steeper.The interrelated relationship among the diffusion,compositions,solution temperature and free energy of the system has been discussed in detail.Moreover,increasing the heating rate (～20.0 K/min) may help to improve the mechanical properties of the alloy by mainly adjusting the αp/βt volume fractions,αp particle size and secondary α (αs) size during the process of heating up to the solution temperature.These results may shed some light on the optimization of the knowledge-based heat treatment route.
查看更多>>摘要：The unique hot carrier-driven direct plasmonic photocatalysis of coinage metal nanomaterials (NMs) via energetic localized surface plasmon resonance (LSPR) in visible-light region has been explored in recent years.However,the low photoinduced electron transfer efficiency and insufficient separation of electron-hole pairs would severely preclude their widespread practical applications.Herein,we demonstrate an interesting plasmonic photocatalyst based on the construction of icosahedral (Ih) Au@C60 core-shell NMs,taking advantage of specific delocalized π electrons structure of a tight C60 shell and enhanced LSPR property of Ih Au core.Then,the pronounced interfacial interaction at junction region endows the ob-tained Au@C60 NMs with an outstanding photoinduced hot carrier-transmission during photocatalytic reaction,facilitating a remarkably higher (1.89 times) photocatalytic activity toward visible-light driven degradation of crystal violet (CV) dyes,as compared to bare Au NMs.Impressively,the photocatalytic activity of Ih Au@C60 NMs can be effectively optimized by changing the pH value of reaction solution,with the kinetic rate constant reaching the maximum value of 0.179 min-1 in pH011.4 solution,while 0.005 min-1 at pH03.0.Moreover,due to the protection of a tight C60 shell,the Ih Au@C60 NMs also pos-sess excellent photocatalytic stability/reusability in recycling runs,holding great potential for the design of robust and high-performance plasmonic photocatalysts in repeated practical applications.
查看更多>>摘要：Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5Cu alloy,Mg-2.5Cu-6.0Al alloy exhibits an improved compressive strength of 378 MPa and com-pressive strain of 27g,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg17Al12+Al2Cu phases.They form a discontinuous net-work and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhance-ment of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical defor-mation.This accounts for the good ductility in Mg-Cu-Al alloys.
查看更多>>摘要：Although a variety of processing routes were developed to in-situ manipulate microstructure for fabri-cating high-performance Ti-6Al-4V alloy by directed energy deposition (DED),the in-situ microstructural control ability has been limited and lead to a narrowed mechanical property control range.This work proved the microstructural correlation betweenβ-grains and α-laths resulting from the unique thermal characteristics of DED for the first time and solved such a dilemma through synchronous induction heat-ing assisted laser deposition (SILD) technology.The results confirmed that the laser energy and inductive energy have a different effect on the solidification and solid phase transformation conditions.By adjust-ing the laser-induction parameters,the microstructural correlation can be tuned;the β-grains and α-laths can be controlled relatively separately,thereby significantly enhancing the ductility of as-deposited sam-ple (elongation from 14.2％ to 20.1％).Furthermore,the mechanical properties of the tuned microstructures are even comparable to that of DED Ti-6Al-4V with post heat treatment,which indicates that the poten-tial of SILD to be a one-step manufacturing process to fabricate high performance components without post heat treatment.Furthermore,the tensile testing results of the tuned microstructures indicate that α-lath size is more influential on the mechanical properties than the β-grain size due to its stronger hin-dering effect on the slipping of dislocations.This work promotes the understanding of the microstructural formation mechanism in DED titanium alloy and proves that the combination of synchronous induction and laser can expand the ability to control the microstructure and properties of multi-layer deposition.
Mehmet CagiriciPan WangFern Lan NgMui Ling Sharon Nai...
53-66页
查看更多>>摘要：Electron beam melting (EBM) is a promising technology to manufacture various alloys with outstanding properties;however,the number of available alloys is limited.We propose in situ alloying to acceler-ate the development of advanced and novel alloys,based on thermophysical calculations and CALPHAD approach,during the EBM process.We demonstrate our concept through the design and fabrication of high entropy alloys (HEAs).Three CoCrFeNiMn-xTi (x=0.18,0.50,2.00,in molar ％) HEAs are manufac-tured.EBM-built HEAs achieve a homogeneous distribution of elements while forming multiphase alloys resulted from the hot powder bed.The topological structures formed by secondary phases contribute to an increase in the hardness of EBM-built HEAs up to 900 HV1.Considering alloy design,a systematic analysis on CoCrFeNiMn-038Ti HEA elucidates the microstructural evolution in detail.These findings pro-vide a deep understanding of in situ alloying and pave the way to develop new alloys specific to the EBM process.
查看更多>>摘要：The development of high-efficiency photocatalysts is the primary goal in the field of photocatalytic an-tibacterial research.In this work,the GaN∶ZnO solid solution nanoparticles (NPs) photocatalyst with strong visible absorption and large specific surface area was synthesized via the sol-gel and nitridation reaction process.Also,we systematically investigated the removal efficiency of the organic pollutant and antibacterial activity on E.coli and S.aureus.Notably,methylene blue solution could be completely de-graded after 100 min of visible light illumination using 2 mg/mL GaN∶ZnO catalyst.Moreover,-94％ of the E.coli were inactivated within 120 min,whereas 100％ antibacterial activity against S.aureus was achieved after 90 min of visible light illumination mediated by GaN∶ZnO NPs.We further explore the potential mechanism of visible light photocatalytic antibacterial activity enhanced by GaN∶ZnO NPs photocatalyst.The current work not only provides a new and efficient photocatalytic antibacterial nanomaterial but also demonstrates its promising applications in environmental and biological fields.
查看更多>>摘要：Myocardial infarction (MI) is one of the common cardiovascular diseases that occurs with a blockage in one or more of the coronary arteries to lead to the damage of the myocardium,resulting in a life-threatening condition.To repair the damaged myocardium in MI,researchers are looking forwards to new ways to postpone the progression of myocardial injury.Cardiac patches,the scaffolds layered on the heart surface,can provide mechanical support for the infarction site and improve cardiac function by delivering various bioactive factors or cells,showing considerable curative effect in the treatment of MI.Biomate-rials with certain biocompatibility and mechanical properties have received widespread attention for the application in cardiac patches.In this review,we focus on the recent progress on these biomaterials-based cardiac patches,which could be categorized into two types according to the sources of materials including (i) natural materials and (ii) synthetic materials.The major advantages and current challenges of each type are discussed and a brief perspective on the future research directions is presented.
查看更多>>摘要：Waste plastics recycling and oil/organics remediation are environmental issues of global concem.In this work,a protectant was introduced,for the first time,to make highly efficient catalysts for pyrolysis of waste plastics into carbon nanotubes (CNTs) with high yield.By using waste polyethylene,Co(NO3)2 and oleylamine respectively as carbon source,catalyst precursor and protectant,a yield as high as 59.0％ was achieved.The CNTs exhibited a high adsorption capacity for methylene blue (up to 107.1 mg/g).Fur-thermore,by combining the CNTs with graphene oxide,a graphene-CNT aerogel with a low density of 8.2 mg/cm3 and high porosity of 96.0％ was successfully prepared.It showed excellent hydrophobicity and mechanical stability,as well as high adsorption capacity of 289-410 g/g oil/organic solvent,which was much higher than most of these achieved by carbon-based three-dimensional materials reported previously,making the as-prepared aerogel a very promising adsorbent for oil/water separation.
查看更多>>摘要：High-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C ceramics,with different contents (0,5,10,and 20 vol.％) of SiC whiskers (SiCw),were fabricated by spark plasma sintering using raw powders synthesized via car-bothermal reduction.The application of a uniaxial compaction force led to texture development of the SiCw within the (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C matrix.Fracture toughness increased with the increase in SiCw content,while Vickers hardness remains almost unchanged.The toughness of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-20 vol.％ SiCw ceramics reached 4.3 ± 0.3 MPa m1/2,which was approximately 43％ higher than that of the monolithic (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C ceramic (3.0 ± 0.2 MPa m1/2).The main toughening mechanisms were attributed to crack deflection,whisker debonding,and whisker pullout.
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