查看更多>>摘要：TiNiSi-type MnCoSi-based alloys show large magnetostriction during the magnetic-field-induced meta-magnetic transition.However,the high critical field required to drive the transition directly hinders their potential applications.In this work,we systematically investigate the tricritical behavior and mag-netostrictive effect in substituted MnCoSi alloys.Replacing Si with Sb or In,Co with Fe or Cu,and Mn with Co,which can simultaneously reduce the critical field and the temperature of tricritical point,are explored.Among the substituted MnCoSi alloys,Mn0.983Co1.017Si displays a temperature of a tricritical point of 250 K and a room-temperature critical field of 0.60 T,which is the lowest up to now.Profited from these optimizations,a large reversible magnetostrictive effect under low field is successfully realized at room temperature.In a field of 1 T,the magnetostriction of Mn0.983Co1.017Si alloy is close to 1000 ppm.Besides,a strong relation between critical field and valence electron concentration is revealed in the transition-metal-substituted MnCoSi alloys.Our work greatly enhances the low-field magnetostrictive performance of MnCoSi-based alloys and make them be of interest in potential applications.
查看更多>>摘要：A double holmium-silver sulfate was obtained for the first time.The temperature intervals for the for-mation and stability of the compound were determined by differential scanning calorimetry.The crystal structure of AgHo(SO4)2 was determined by Rietveld method.The X-ray diffraction(XRD)analysis showed that the compound crystallizes in the monoclinic syngony,space group P21/m,with the unit cell param-eters a=4.71751(4)Å,b=6.84940(6)Å and c=9.89528(9)Å,β=95.1466(4)°,V=318.448(5)Å3,Z=2,RB=1.55％,T=303K.Two types of sulfate tetrahedra were found in the structure,which significantly affected the spectral properties in the infrared range.In the temperature range of 143-703 K,a negative thermal expansion along the b direction accompanied by a positive thermal expansion along the a and c directions was observed.It was established that negative thermal expansion is the result of the deforma-tion of sulfate tetrahedra,which is affected by the movement of holmium and silver atoms.The excitation in the blue spectral range(457.9 nm)produces a luminescence in light blue(489 nm),green(545 nm)and red(654 nm)spectral ranges,and the latter two were of comparable intensity that is favorable for WLED sources.The observed luminescent band distribution is ascribed to the specific crystal field at Ho3+ion sites rather than a variation of radiationless probability.
查看更多>>摘要：In this study,a novel strategy for developing α+β dual-phase titanium alloys with low Young's modulus and high yield strength was proposed,and a Ti-15Nb-5Zr-4Sn-1Fe alloy was developed through theoret-ical composition design and microstructure manipulation.After hot-rolling and subsequent annealing,a high volume fraction of ultrafine grained α phase embedded in metastable β-matrix was formed in the microstructure as intended.Consequently,this alloy exhibits both low Young's modulus(61 GPa)and high yield strength(912 MPa).The experimental results prove that the proposed strategy is appropriate for developing titanium alloys with superior yield strength-to-modulus ratio than those of conven-tional metallic biomedical materials.Present study might shed light on the research and development of advanced biomedical titanium alloys with low Young's modulus and high yield strength.
Alejandra Rodriguez-ContrerasMiquel PunsetJosé A.CaleroFrancisco Javier Gil...
129-149页
查看更多>>摘要：One of the biggest challenges in the biocompatibility of implantable metals is the prevention of the stress shielding effect,which is related to the coupling of the bone-metal mechanical properties.This stress shielding phenomenon provokes bone resorption and the consequent adverse effects on prosthesis fixation.However,it can be inhibited by adapting the stiffness of the implant material.Since the use of titanium(Ti)porous structures is a great alternative not only to inhibit this effect but also to improve the osteointegration of orthopedic and dental implants,a brief description of the techniques used for their manufacturing and a review of the current commercialized implants produced from porous Ti assemblies are compiled in this work.As powder metallurgy(PM)with space holder(SH)is a powerful technology used to produce porous Ti structures,it is here discussed its potential for the fabrication of medical devices from the perspectives of both design and manufacture.The most important parameters of the technique such as the size and shape of the initial metallic particles,the SH and binder type of materials,the compaction pressure of the green form,and in the sintering stage,the temperature,atmosphere,and time are reviewed according to the bibliography reported.Furthermore,the importance of the porosity and its types together with the influence of the mentioned parameters in the final porosity and,consequently,in the ultimate mechanical properties of the structure are discussed.Finally,a few examples of the PM-SH application for the manufacturing of orthopedic implants are presented.
查看更多>>摘要：In a solution treated Co-20Ni-6Si shape memory alloy,coherent nano-particles were precipitated after annealing at 873 K for 1 min,but the shape memory effect almost vanished.It is attributed to that the coherent nano-particles not only suppressed the stress-induced face-centered cubic to close-packed hexagonal martensite transformation but also damaged the crystallographic reversibility of reverse martensite transformation.After further annealing at 1073 K for 1 min,the shape memory effect was reju-venated owing to the dissolution of nano-particles.Besides,the recovery strain significantly increased to 5.1％ from the solution treatment of 3.1％ after annealing at 1073 K for 1 min.
查看更多>>摘要：Lithium(Li)metal is widely considered the ultimate anode for future rechargeable batteries.However,dendritic growth and related parasitic reactions during long-term cycling often lead to severe safety hazards and catastrophic failure.Herein,we fabricate a hybrid anode by coating single-phase Li21Si5 on lithium metal.The resultant electrodes show a stable cycle and depressed polarization in symmetric and half cells.A planar plating/stripping behavior is observed on the modified anode.The investigation of the interplay of Li and Li21Si5 shows relatively large adsorption energy in the Li-Si system.The deposition and stripping are surface processes,and Li21Si5 maintains its intrinsic phase structure.The deposited Li layer around Li21Si5 also has the advantage of diminished preferred orientation,which also contributes to the planar growth of Li.Both LiFePO4(LFP)and LiNi1/3Co1/3Mn1/3O2(NCM)cathodes were applied to further demonstrate the enhanced rate and cycle performance.
查看更多>>摘要：The microwave absorption properties of Ti2O3 were systematically investigated.Experimental results indicate that Ti2O3 has microwave absorption performance with a minimum reflection loss value of-37.6 dB at 18.6 GHz and an effective absorption bandwidth(RL＜-10 dB)of 2 GHz.Further,vacancy defects were introduced into Ti2O3 by carbothermal reduction.Interestingly,the effective absorption bandwidth of Ti2O3 with vacancy defects reach 3.2 GHz.First-principles calculations provide evidence that vacancy defects result in the changes of electric dipole state,leading to a wider effective absorption bandwidth.These results have significance in understanding the origin of electromagnetic phenomena and developing electromagnetic wave absorption materials.
查看更多>>摘要：This paper models hot compression testing using a dilatometer in loading mode.These small-scale tests provide a high throughput at low cost,but are susceptible to inhomogeneity due to friction and temper-ature gradients.A novel method is presented for correcting the true stress-strain constitutive response over the full range of temperatures,strain-rates and strain.The nominal response from the tests is used to predict the offset in the stress-strain curves due to inhomogeneity,and this stress offset Δσ is applied piecewise to the data,correcting the constitutive response in one iteration.A key new feature is the smoothing and fitting of the flow stress data as a function of temperature and strain-rate,at multiple discrete strains.The corrected model then provides quantitative prediction of the spatial and tempo-ral variation in strain-rate and strain throughout the sample,needed to correlate the local deformation conditions with the microstructure and texture evolution.The study uses a detailed series of 144 hot compression tests of a Zr-Nb alloy.While this is an important wrought nuclear alloy in its own right,it also serves here as a test case for modelling the dilatometer for hot testing of high temperature alloys,particularly those with dual α-β phase microstructures(such as titanium alloys).
查看更多>>摘要：Construction of metal-organic-frameworks-based composite photocatalysts has attracted much atten-tion for the reasonable band gap and high surface areas to improve the photocatalytic activity.In this study,the ternary heterojunction Pd@UiO-66-NH2@Znln2S4 nanocomposites were facilely prepared for the first time by a two-step method.The visible-light-promoted hydrogen production rate of 0.3％ Pd@UiO-66-NH2@Znln2S4 reaches up to 5.26 mmol g-1 h-1,which is evidently much higher than pure UiO-66-NH2,ZnIn2S4 and binary UiO-66-NH2/ZnIn2S4 composites.Such a huge improvement in the pho-tocatalytic performance is mainly attributed to the matched band gap of ZnIn2S4 and UiO-66-NH2,and the introduction of Pd NPs into photocatalysts that broaden spectral response range and promote the photon induced charge carrier separation.This work may provide a feasible approach for the design and construction of metal-organic-frameworks-based photocatalytic materials.
查看更多>>摘要：Separating high-purity hydrogen isotopes from their mixture still remains a huge challenge due to almost the identical physicochemical properties.Much importance has been attached to tune microstructure of porous materials,while heat management during hydrogen isotope separation tends to be ignored.Herein,a porous material 5A molecular sieve(5A)is mixed with graphene(GE)under ball grinding to enhance its thermal conductivity for hydrogen isotope separation.The thermal conductivity increases from 0.19 W m-1 K-1 of neat 5A,0.75 W m-1 K-1 of 5A/GE2(2 wt％GE)to 1.23 W m-1 K-1 of 5A/GE8.In addition,introducing GE into 5A promotes hydrogen adsorption and D2/H2 adsorption ratio.5A/GE2 shows the highest D2 adsorption capacity(5.40 mmol/g)and the largest D2/H2 adsorption ratio(1.07)among the composites.It also displays a high efficiency of heat transfer that contributes to a low energy consumption due to the shortened cycle time during hydrogen isotope separation.This work offers new insights into material design for improved hydrogen isotope separation,which is greatly crucial to scientific and industrial applications,such as fuel self-sustaining in fusion reactors.
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