A comparative study of two kinds of oxidants(H2O and O3) with the combination of two metal precursors(TMA and La(~iPrCp)3) for atomic layer deposition(ALD) La2O3/Al2O3 nanolaminates is carried out. The effect...A comparative study of two kinds of oxidants(H2O and O3) with the combination of two metal precursors(TMA and La(~iPrCp)3) for atomic layer deposition(ALD) La2O3/Al2O3 nanolaminates is carried out. The effects of different oxidants on the physical properties and electrical characteristics of La2O3/Al2O3 nanolaminates are studied. Initial testing results indicate that La2O3/Al2O3 nanolaminates could avoid moisture absorption in the air after thermal annealing. However, moisture absorption occurs in H2O-based La2O3/Al2O3 nanolaminates due to the residue hydroxyl/hydrogen groups during annealing. As a result, roughness enhancement, band offset variation, low dielectric constant and poor electrical characteristics are measured because the properties of H2O-based La2O3/Al2O3 nanolaminates are deteriorated. Addition thermal annealing effects on the properties of O3-based La2O3/Al2O3 nanolaminates indicate that O3 is a more appropriate oxidant to deposit La2O3/Al2O3 nanolaminates for electron devices application.展开更多
Nanolaminates are composed of nanoscale-thick alternating layers of different materials and their properties are dependent on the individual layers,the layer thickness and the interfaces between the layers.Nanolaminat...Nanolaminates are composed of nanoscale-thick alternating layers of different materials and their properties are dependent on the individual layers,the layer thickness and the interfaces between the layers.Nanolaminates composed of cubic crystal structured metals are usually ductile compared to nanolaminates containing hexagonal crystal structured metals.Mechanical properties such as strength and hardness of nanolaminates increase with a decrease in individual layer thickness down to a few nanometers and they become independent when the thickness of individual layers is less than a couple of nanometers.This review provides a detailed analysis of the effects of individual layer thickness and the interface structures on the strength and the strengthening mecha nisms of nanolaminates,their ductility and fracture behavior in terms of structural variations including grain morphologies,nanotwins,amorphous phases and crystal structures of the layers.The principles for designing nanolaminates with exceptionally high mechanical and physical properties and their fabrication are also highlighted.Some contradictory issues such as strengthening mechanisms,elastic modulus dependency on individual layer thickness and the effect of a thin amorphous layer on the strength are discussed.This review also provides future research directions in designing the high-strength nanolaminates that will facilitate practical engineering applications through analyzing up-to-date research efforts.展开更多
The amorphous/amorphous nanolaminates(A/ANLs)have aroused great attentions owing to their tunable structure and enhanced mechanical properties.However,the plastic deformation mechanism of A/ANLs have yet been clarifie...The amorphous/amorphous nanolaminates(A/ANLs)have aroused great attentions owing to their tunable structure and enhanced mechanical properties.However,the plastic deformation mechanism of A/ANLs have yet been clarified.Here,we systematically examined the mechanical properties and deformation behavior of series of NiNb/ZrCuNi Al A/ANLs via nanoindentaion test.It was found that both the amount and morphology of amorphous/amorphous interface(A/AIs)played crucial roles in the plastic deformation of A/ANLs.Less and straighter A/AIs facilitated multiple shear banding deformation,of which the hardness increased with decreasing layer thickness,as the A/AIs hindered the propagation of shear bands(SBs).Whilst,more and wavier A/AIs promoted homogeneous deformation,of which the hardness stayed at a much lower value and was relatively irrelevant with the layer thickness,for the promoted activation of shear transformation zones by A/AIs.Our results provide guidance for modifying the mechanical properties of amorphous alloys with interface engineering design.展开更多
Achieving homogeneous plastic deformation in metallic glasses is a long-standing goal yet to be solved in materials science. Here we investigate the effect of ion irradiation on the plastic deformation behavior of ZrC...Achieving homogeneous plastic deformation in metallic glasses is a long-standing goal yet to be solved in materials science. Here we investigate the effect of ion irradiation on the plastic deformation behavior of ZrCu/ZrCuNiAlSi amorphous/amorphous nanolaminates(A/ANLs) via nanoindentation testing. The experimental results indicate a dramatic change in deformation mode from multiple shear banding events to homogeneous compressive deformation before and after ion irradiation on the A/ANLs in the areas underneath the indenter. Ion irradiation-induced changes of both fraction and distribution of free volume inside each constituent layer and interfacial state in the A/ANLs may be responsible for the unusual homogeneous deformation behavior. Our results suggest that the mechanical property of A/ANLs could be modified by tuning both the inner and interfacial structure via ion irradiation.展开更多
In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,an...In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical properties.It ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased hardness.Contrary to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation hard-ening.By contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 nm.Below this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion irradiation.Nevertheless,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced SRS.Such unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.展开更多
Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformati...Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.展开更多
Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and port...Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and portable OLEDs are being employed in more diverse climates and environmental conditions, the OLED encapsulation layer must retain robust mechanical properties and stability in high temperature/high humidity conditions. Al2O3 films have demonstrated excellent barrier performance, but they readily hydrolyze when exposed to prolonged harsh environments. In this study, we fabricated a thin film encapsulation (TFE) film that was resistant to hydrolysis, using Al2O3/MgO (AM) nanolaminates. MgO has superior resistance to harsh environments, and the aluminate phase generated by the chemical reaction of Al2O3 and MgO provided excellent barrier performance, even after storage in harsh conditions. A multi-barrier fabricated using the AM nanolaminate showed excellent barrier performance, close to the level required by OLEDs. It did not significantly deteriorate even after a bending test of 1,000 iterations at 0.63% strain. After 1,000 cycle of bending, the electrical properties of the passivated OLEDs were not significantly degraded at shelf-lifetime test where the fabricated device was stored for 50 days in a harsh environment of 60℃, 90% relative humidity. The multi-barrier shows the best performance compared to previous studies on flexible encapsulation that can be used in harsh environments.展开更多
Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical p...Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates(DPNLs)with different layer thicknesses are investigated using molecular dynamics simulations.The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible,while it affects the plastic deformation mechanism of amorphous layers distinctly.The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs,which is inversely proportional to the layer thickness.It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat.Young's moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces.Furthermore,the main plastic deformation mechanism in crystalline part:grain reorientation,transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti,has also been displayed in the present work.The results may provide a guideline for design of high-performance Ti and its alloy.展开更多
A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The ...A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The nanolaminated and ultrafine-grained structure initially created in the CNT/AlSi flaky powder was perfectly conserved, due to the typical ‘cold’ feature of CS. As discussed based on finite element analysis and single splat observation, self-alignment behavior of the flaky powders during impact also allowed the formation of the microlaminated structure. Hence, the scalable CS technique opens a new avenue for bioinspired material design and fabrication with complex shape.展开更多
Flexible thin-film transistors(TFTs)have attracted wide interest in the development of flexible and wearable displays or sensors.However,the conventional high processing temperatures hinder the preparation of stable a...Flexible thin-film transistors(TFTs)have attracted wide interest in the development of flexible and wearable displays or sensors.However,the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates.Here,we develop a stable laminated Al_(2)O_(3)/HfO_(2) insulator by atomic layer deposition at a relatively lower temperature of 150℃.A sputtered amorphous indium-gallium-zinc oxide(IGZO)with the stoichiometry of In_(0.37)Ga_(0.20)Zn_(0.18)O_(0.25) is used as the active channel material.The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al_(2)O_(3)/HfO_(2) nanolaminates.Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al_(2)O_(3),crystallized HfO_(2),and the aluminate Al-Hf-O phase,the as-prepared TFTs present the carrier mobilities of 9.7 cm^(2) V^(−1) s^(−1),ON/OFF ratio of-1.3×10^(6),subthreshold voltage of 0.1 V,saturated current up to 0.83 mA,and subthreshold swing of 0.256 V dec^(−1),signifying a high-performance flexible TFT,which simultaneously able to withstand the bending radius of 40 mm.The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60-70%,a temperature of 25-30℃ environment.The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%.展开更多
Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directi...Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directions are utilized to systematically study the mechanical performance of the cracked material.The results indicate that pre-existing crack dramatically changes the plastic deformation mechanism of the Ti/Ni nanolaminate.Unlike the initial plastic deformation originating from the interface or weak Ti layer of the crack-free samples,the plastic behavior of cracked Ti/Ni nanolaminate first occurs at the crack tip due to the local stress concentration.Subsequent plastic deformation is dominated by the interaction between the crack and interface.The Ti/Ni interface not only impedes the movement of the initial plastic deformation carriers(dislocation,slip band,and deformation twinning)from the crack tip,but also promotes the movement of interfacial dislocations in the tension process.Microstructure evolution analysis further confirms that the plastic deformation mechanism transition is ascribed to the orientation-dependent tensile behavior at the crack tip,which is intrinsically attributed to the anisotropy of the certain crystal structure and loading direction of the cracked Ti/Ni nanolaminate.In addition,by analyzing the effects of different plastic deformation carriers on crack propagation in specific crystal,it can be discovered that the interfacial dislocations moving towards the crack tip can further promote the crack growth.展开更多
Metallic nanolaminated materials possess excellent mechanical properties due to their unique modulation structures and interfacial properties.However,how microdefects affect their mechanical properties is still uncert...Metallic nanolaminated materials possess excellent mechanical properties due to their unique modulation structures and interfacial properties.However,how microdefects affect their mechanical properties is still uncertain.To evaluate the influences of void location(in the crystalline layer and the Ti/Ni interface),void diameter(d)and thickness of the intermediate layer(h)on overall tensile behaviors,various types of defective Ti/Ni nanolaminates with pre-existing void are established by the molecular dynamics method in this work.The results indicate that the strength and plastic deformation mechanisms are strongly dependent on those determinants.Yield stresses of Ti/Ni nanolaminates decrease distinctly with increasing void diameter,while peak stresses with a void in the crystalline layer decrease with increasing d/h.Different void locations lead eventually to disparate initial plastic deformation carriers around the void,and various evolutions in the microstructure of the defective Ti/Ni nanolaminates.The Ti/Ni interface plays a significant role in the tensile process.The semi-coherent interface impedes new grains and lattice dislocations from passing across the interface,while the incoherent interface facilitates dislocations generating and sliding along the interface,and absorbs the dislocations moving to the interface.The results also indicate that the strain rate significantly affects the evolution of the microstructure and the tensile properties of defective Ti/Ni nanolaminates.展开更多
Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a...Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a new strategy to develop a hierarchical and interconnected amorphous-crystalline nanocomposite arising from the nanoscale elemental interdiffusion and oxygen adsorption behavior dur-ing thermal treatment processes.The nanocomposite consisted of a three-dimensional(3D)hierarchical network structure where the crystalline phase(Cr-Co-Ni-Al)was embedded into the Al-O-based amor-phous phase network with critical feature sizes encompassing three orders of magnitude(from microm-eter to nanometer scale).It can achieve ultrahigh compression yield strength of-3.6 GPa with large homogeneous deformation of over 50%strain.The massive interstitial atoms induced lattice distortion and hierarchical amorphous phase boundary contributed to the strength improvement.in situ Uniaxial compression inside a transmission electron microscope(TEM)revealed that the exceptional deformability of the nanocomposites resulted from the homogenous plastic flow of nano-sized amorphous phase and the plastic co-deformation behavior restricted by the nano-architected dual-phase interface.The proposed dual-phase synthesis approach can outperform conventional nanolaminates design strategies in terms of the mechanical properties achievable while providing a pathway to easily tune the microstructure of these nanolaminates.展开更多
Metastable high entropy alloys(HEAs) and amorphous metallic glasses(MGs), with the chemical disordered character, are intensively studied due to their excellent performance. Here, we introduce Cu to separately constra...Metastable high entropy alloys(HEAs) and amorphous metallic glasses(MGs), with the chemical disordered character, are intensively studied due to their excellent performance. Here, we introduce Cu to separately constrain these two metastable materials and comparatively investigate their deformation behaviors and mechanical properties of Cu/HEA Fe Co Cr Ni and Cu/MG Cu Zr nanolaminated micropillars in terms of intrinsic layer thickness h and extrinsic pillar diameter D. The metastable HEA layers, as the hard phase in Cu/HEA micropillars, are stable and dominate the deformation, while transformation(crystallization) occurs in MG which plays a minor role in deformation of Cu/MG micropillars. The h-controlled deformation mode transits from the D-independent homogenous-like deformation at large h to the Ddependent shear banding at small h in both Cu/HEA and Cu/MG micropillars. Although both Cu/HEA and Cu/MG micropillars exhibit a maximum strain hardening capability controlled by h, the former manifests much lower hardening capability compared with the latter. The intrinsic size h and extrinsic size D have a strong coupling effect on the strength of Cu/HEA and Cu/MG micropillars. The strength of strength of Cu/HEA micropillars exhibits the D-dependent transition from "smaller is stronger" to "smaller is weaker"with increasing h. By contrast, the strength of Cu/MG micropillars exhibits the transition from bulk-like D-independent behavior at large h to small volume D-dependent behavior(smaller is stronger) at small h.展开更多
Nanolaminated structures composed of low-angle grain boundaries(LAGBs) possess high thermal stability. In this paper, a gradient nanolaminated(GNL) surface layer with smooth finish was fabricated on an interstitial-fr...Nanolaminated structures composed of low-angle grain boundaries(LAGBs) possess high thermal stability. In this paper, a gradient nanolaminated(GNL) surface layer with smooth finish was fabricated on an interstitial-free steel by means of surface mechanical rolling treatment. Microstructural observations demonstrated that the average lamellar thickness is about 80 nm in the topmost surface layer and increases with increasing depth. High thermal stability was confirmed in the GNL surface layer after annealing at 500℃. Diffusion measurements showed that effective diffusivity of Cr in GNL layer is 4–6 orders of magnitude higher than lattice diffusivity within the temperature range from 400 to 500℃. This might be attributed to numerous LAGBs or dislocation structures with a higher energy state in the GNL surface layer. This work demonstrates the possibility to advanced chromizing(or other surface alloying)processes of steels with formation of GNL surface layer, so that a thicker alloyed surface layer with a stable nanostructure is achieved.展开更多
Structural, electronic and mechanical properties of ZnO/Graphene(ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition(ALD) and chemical vapor deposition(CVD) were investigated.We performed ...Structural, electronic and mechanical properties of ZnO/Graphene(ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition(ALD) and chemical vapor deposition(CVD) were investigated.We performed scanning and transmission electron microscopy(SEM/TEM), X-ray diffraction(XRD), electron energy loss spectroscopy(EELS), Raman spectroscopy, X-Ray photoelectron spectroscopy(XPS) and nanoindentation to characterize the ZnO/G nanolaminates. The main structural and mechanical parameters of ZnO/G nanolaminates were calculated. The obtained results were analyzed and interpreted taking into account mechanical interaction and charge effects occurring at the G-ZnO interface. The influence of graphene sublayers number on the mechanical behavior of the ZnO/G nanolaminates was studied. By reducing the bilayer thickness, the mechanical parameters of the films can be tuned(Young's modulus100-200 GPa, hardness 3-9 GPa). The softer response of the multilayers as compared to the single layers of ZnO and graphene was attributed to the structural changes in the ZnO layer and the interfaces. This study shows the mechanical behavior of ZnO/G nanolaminates and their influence on the development of novel electro-optical devices based on these structures.展开更多
Different laminated structures of TiO_(2)/SiO_(2) composite film were prepared via atomic layer deposition(ALD)on alumina substrates.The effect of the annealing temperature in the air on the surface morphologies,cryst...Different laminated structures of TiO_(2)/SiO_(2) composite film were prepared via atomic layer deposition(ALD)on alumina substrates.The effect of the annealing temperature in the air on the surface morphologies,crystal structures,binding energies,and ingredient content of these films was investigated using X-ray diffraction,field emission scanning electron microscopy,and X-ray photoelectron spectroscopy.Results showed that the binding energy of Ti and Si increased with decrease of the Ti content,and the TiO_(2)/SiO_(2) nanolaminated films exhibited a complex bonding structure.As the annealing temperature increased,the thickness of the nanolaminated films decreased,and the density and surface roughness increased.An increase in the crystallization temperature was proportional to the SiO_(2) content in TiO_(2)/SiO_(2) composite film.The annealing temperature and thin thickness strongly affected the phase structure of the ALD TiO_(2) thin film.To be specific,the TiO_(2) thin film transformed into an anatase phase from an amorphous phase after an increase in the annealing temperature from 400℃ to 550℃,and the TiO_(2) film exhibited an anatase phase until the annealing temperature reached 850℃,owing to its extremely small thickness.The annealing process caused the Al ions in the substrate to diffuse into the films and bond with 0.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61604016 and 51501017)the Fundamental Research Funds for the Central Universities,China(Grant No.310831161003)
文摘A comparative study of two kinds of oxidants(H2O and O3) with the combination of two metal precursors(TMA and La(~iPrCp)3) for atomic layer deposition(ALD) La2O3/Al2O3 nanolaminates is carried out. The effects of different oxidants on the physical properties and electrical characteristics of La2O3/Al2O3 nanolaminates are studied. Initial testing results indicate that La2O3/Al2O3 nanolaminates could avoid moisture absorption in the air after thermal annealing. However, moisture absorption occurs in H2O-based La2O3/Al2O3 nanolaminates due to the residue hydroxyl/hydrogen groups during annealing. As a result, roughness enhancement, band offset variation, low dielectric constant and poor electrical characteristics are measured because the properties of H2O-based La2O3/Al2O3 nanolaminates are deteriorated. Addition thermal annealing effects on the properties of O3-based La2O3/Al2O3 nanolaminates indicate that O3 is a more appropriate oxidant to deposit La2O3/Al2O3 nanolaminates for electron devices application.
基金financial support for this research by the Australian Research Council (ARC) through the Discovery Project (DP170102557)Future Fellowship (FT160100252)National Health and Medical Research Council (NHMRC), Australia through project grant (GNT1087290)。
文摘Nanolaminates are composed of nanoscale-thick alternating layers of different materials and their properties are dependent on the individual layers,the layer thickness and the interfaces between the layers.Nanolaminates composed of cubic crystal structured metals are usually ductile compared to nanolaminates containing hexagonal crystal structured metals.Mechanical properties such as strength and hardness of nanolaminates increase with a decrease in individual layer thickness down to a few nanometers and they become independent when the thickness of individual layers is less than a couple of nanometers.This review provides a detailed analysis of the effects of individual layer thickness and the interface structures on the strength and the strengthening mecha nisms of nanolaminates,their ductility and fracture behavior in terms of structural variations including grain morphologies,nanotwins,amorphous phases and crystal structures of the layers.The principles for designing nanolaminates with exceptionally high mechanical and physical properties and their fabrication are also highlighted.Some contradictory issues such as strengthening mechanisms,elastic modulus dependency on individual layer thickness and the effect of a thin amorphous layer on the strength are discussed.This review also provides future research directions in designing the high-strength nanolaminates that will facilitate practical engineering applications through analyzing up-to-date research efforts.
基金financially supported by the Guangdong Basic and Applied Basic Research Foundation,China(Grant No.2021A1515010756,2019B1515130005)the Guangdong Major Project of Basic and Applied Basic Research,China(Grant No.2019B030302010)+5 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180266)the Basic Research Program of Nantong(No.JC2019083)the National Natural Science Foundation of China(No.51822107,11972037,52001269)the Fundamental Research Funds for the Central Universitiesthe National Key Research and Development Plan(Grant No.2018YFA0703603)the Strategic Priority Research Program of Chinese Academy of Sciences with Grant No.XDB30000000
文摘The amorphous/amorphous nanolaminates(A/ANLs)have aroused great attentions owing to their tunable structure and enhanced mechanical properties.However,the plastic deformation mechanism of A/ANLs have yet been clarified.Here,we systematically examined the mechanical properties and deformation behavior of series of NiNb/ZrCuNi Al A/ANLs via nanoindentaion test.It was found that both the amount and morphology of amorphous/amorphous interface(A/AIs)played crucial roles in the plastic deformation of A/ANLs.Less and straighter A/AIs facilitated multiple shear banding deformation,of which the hardness increased with decreasing layer thickness,as the A/AIs hindered the propagation of shear bands(SBs).Whilst,more and wavier A/AIs promoted homogeneous deformation,of which the hardness stayed at a much lower value and was relatively irrelevant with the layer thickness,for the promoted activation of shear transformation zones by A/AIs.Our results provide guidance for modifying the mechanical properties of amorphous alloys with interface engineering design.
基金financial support from the National Natural Science Foundation of China (No. 51471131)the Natural Science Foundation of Shaanxi Province (No. 2019TD-020)+4 种基金National Science Basic Research Plan in shaanxi Province of China (No. 2020JM-41)financial support from the Fundamental Research Funds for the Central Universities (No. 021314380118)the Natural Science Foundation of Jiangsu Province, China (No. BK20180266)financial support from Fundamental Research Funds for the Central UniversitiesNational Science Basic Research Plan in shaanxi Province of China (No. 2020JM-33)。
文摘Achieving homogeneous plastic deformation in metallic glasses is a long-standing goal yet to be solved in materials science. Here we investigate the effect of ion irradiation on the plastic deformation behavior of ZrCu/ZrCuNiAlSi amorphous/amorphous nanolaminates(A/ANLs) via nanoindentation testing. The experimental results indicate a dramatic change in deformation mode from multiple shear banding events to homogeneous compressive deformation before and after ion irradiation on the A/ANLs in the areas underneath the indenter. Ion irradiation-induced changes of both fraction and distribution of free volume inside each constituent layer and interfacial state in the A/ANLs may be responsible for the unusual homogeneous deformation behavior. Our results suggest that the mechanical property of A/ANLs could be modified by tuning both the inner and interfacial structure via ion irradiation.
基金financially supported by the National Natural Science Foundation of China(Nos.U2067219,51722104,51790482,51761135031 and 92163201)the National Key Research and Development Program of China(No.2017YFA0700701)+1 种基金the 111 Project 2.0 of China(No.BP2018008)the Fundamental Research Funds for the Central Universities(No.xtr022019004)。
文摘In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical properties.It ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased hardness.Contrary to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation hard-ening.By contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 nm.Below this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion irradiation.Nevertheless,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced SRS.Such unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.
基金financially supported by the National Natural Science Foundation of China(Nos.51690163 and 51601147)the Science Challenge Project(No.TZZT2019-D1.5)+4 种基金the Ministry of Science and Technology of China(No.2017YFA0700700)the United States National Science Foundation(Nos.DMR-1006557,1611180,and 1809640)the Fundamental Research Funds for the Central Universities in China(No.G2016KY0302)the CyberStar cluster funded by NSF through grant No.OCI-0821527the XSEDE clusters supported by NSF through Grant No.ACI-1053575。
文摘Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.
基金This research was supported by the Engineering Research Center of Excellence(ERC)Program supported by the National Research Foundation(NRF)of the Korean Ministry of Science,ICT&Future Planning(MSIP)(Grant No.NRF-2017R1A5A1014708).The authors express sincere gratitude to National NanoFab(NNFC)for the measurements.We also thank Prof.Byeong:Soo Bae from KAIST for help in synthesis of the polymers.
文摘Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and portable OLEDs are being employed in more diverse climates and environmental conditions, the OLED encapsulation layer must retain robust mechanical properties and stability in high temperature/high humidity conditions. Al2O3 films have demonstrated excellent barrier performance, but they readily hydrolyze when exposed to prolonged harsh environments. In this study, we fabricated a thin film encapsulation (TFE) film that was resistant to hydrolysis, using Al2O3/MgO (AM) nanolaminates. MgO has superior resistance to harsh environments, and the aluminate phase generated by the chemical reaction of Al2O3 and MgO provided excellent barrier performance, even after storage in harsh conditions. A multi-barrier fabricated using the AM nanolaminate showed excellent barrier performance, close to the level required by OLEDs. It did not significantly deteriorate even after a bending test of 1,000 iterations at 0.63% strain. After 1,000 cycle of bending, the electrical properties of the passivated OLEDs were not significantly degraded at shelf-lifetime test where the fabricated device was stored for 50 days in a harsh environment of 60℃, 90% relative humidity. The multi-barrier shows the best performance compared to previous studies on flexible encapsulation that can be used in harsh environments.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51902254 and 12072286)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2021JZ-53 and 2018JQ5108)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.20JK0845)。
文摘Crystalline/amorphous nanolaminate is an effective strategy to improve the mechanical properties of metallic materials,but the underlying deformation mechanism is still under the way of exploring.Here,the mechanical properties and plastic deformation mechanism of Ti/TiCu dual-phase nanolaminates(DPNLs)with different layer thicknesses are investigated using molecular dynamics simulations.The results indicate that the influence of the layer thickness on the plastic deformation mechanism in crystalline layer is negligible,while it affects the plastic deformation mechanism of amorphous layers distinctly.The crystallization of amorphous TiCu is exhibited in amorphous parts of the Ti/TiCu DPNLs,which is inversely proportional to the layer thickness.It is observed that the crystallization of the amorphous TiCu is a process driven by stress and heat.Young's moduli for the Ti/TiCu DPNLs are higher than those of composite material due to the amorphous/crystalline interfaces.Furthermore,the main plastic deformation mechanism in crystalline part:grain reorientation,transformation from hexagonal-close-packed-Ti to face-centered cubic-Ti and body-centered cubic-Ti,has also been displayed in the present work.The results may provide a guideline for design of high-performance Ti and its alloy.
基金financial support from China Scholarship Council for his Ph.D. projectThe TEM facility in Lille, France, is supported by the Conseil Regional du Nord-Pas de Calais and the European Regional Development Fund
文摘A fully dense carbon nanotubes (CNTs) reinforced AlSi matrix composite with the multiscale nacre-like architecture was designed and successfully realized by flake powder metallurgy followed by cold spraying (CS). The nanolaminated and ultrafine-grained structure initially created in the CNT/AlSi flaky powder was perfectly conserved, due to the typical ‘cold’ feature of CS. As discussed based on finite element analysis and single splat observation, self-alignment behavior of the flaky powders during impact also allowed the formation of the microlaminated structure. Hence, the scalable CS technique opens a new avenue for bioinspired material design and fabrication with complex shape.
基金This work was supported by the Competitive Research Program(Award No.NRF-CRP13-2014-02),RIE2020 ASTAR AME IAF-ICP(I1801E0030)Campus for Research Excellence and Technological Enterprise(CREATE)that was supported by the National Research Foundation,Prime Minister’s Office,Singapore+1 种基金Q.W.S.thanks to the Natural Science Foundation of China(52003122)the"Longshan scholar"start-up foundation of NUIST.
文摘Flexible thin-film transistors(TFTs)have attracted wide interest in the development of flexible and wearable displays or sensors.However,the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates.Here,we develop a stable laminated Al_(2)O_(3)/HfO_(2) insulator by atomic layer deposition at a relatively lower temperature of 150℃.A sputtered amorphous indium-gallium-zinc oxide(IGZO)with the stoichiometry of In_(0.37)Ga_(0.20)Zn_(0.18)O_(0.25) is used as the active channel material.The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al_(2)O_(3)/HfO_(2) nanolaminates.Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al_(2)O_(3),crystallized HfO_(2),and the aluminate Al-Hf-O phase,the as-prepared TFTs present the carrier mobilities of 9.7 cm^(2) V^(−1) s^(−1),ON/OFF ratio of-1.3×10^(6),subthreshold voltage of 0.1 V,saturated current up to 0.83 mA,and subthreshold swing of 0.256 V dec^(−1),signifying a high-performance flexible TFT,which simultaneously able to withstand the bending radius of 40 mm.The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60-70%,a temperature of 25-30℃ environment.The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%.
基金Project supported by the National Natural Science Foundation of China(Grant No.11572259)the Program for International Cooperation and Exchanges of Shaanxi Province,China(Grant No.2016KW-049)+1 种基金the Natural Science Foundation of Shaanxi Province,China(Grant No.2019JQ-827)the Scientific Research Program Funded by Shaanxi Provincial Education Department,China(Grant No.19JK0672).
文摘Tensile behaviors of Ti/Ni nanolaminate with model-I crack are investigated by molecular dynamics simulations.The Ti/Ni nanolaminates with center crack either in Ti layer or in Ni layer under different loading directions are utilized to systematically study the mechanical performance of the cracked material.The results indicate that pre-existing crack dramatically changes the plastic deformation mechanism of the Ti/Ni nanolaminate.Unlike the initial plastic deformation originating from the interface or weak Ti layer of the crack-free samples,the plastic behavior of cracked Ti/Ni nanolaminate first occurs at the crack tip due to the local stress concentration.Subsequent plastic deformation is dominated by the interaction between the crack and interface.The Ti/Ni interface not only impedes the movement of the initial plastic deformation carriers(dislocation,slip band,and deformation twinning)from the crack tip,but also promotes the movement of interfacial dislocations in the tension process.Microstructure evolution analysis further confirms that the plastic deformation mechanism transition is ascribed to the orientation-dependent tensile behavior at the crack tip,which is intrinsically attributed to the anisotropy of the certain crystal structure and loading direction of the cracked Ti/Ni nanolaminate.In addition,by analyzing the effects of different plastic deformation carriers on crack propagation in specific crystal,it can be discovered that the interfacial dislocations moving towards the crack tip can further promote the crack growth.
基金the National Natural Science Foundation of China(Grant No.12072286)the Natural Science Foundation of Shaanxi Province(No.2020JM-095 and 2021JM-045)Fundamental Research Funds for the Central Universities(No.G2020KY05112).
文摘Metallic nanolaminated materials possess excellent mechanical properties due to their unique modulation structures and interfacial properties.However,how microdefects affect their mechanical properties is still uncertain.To evaluate the influences of void location(in the crystalline layer and the Ti/Ni interface),void diameter(d)and thickness of the intermediate layer(h)on overall tensile behaviors,various types of defective Ti/Ni nanolaminates with pre-existing void are established by the molecular dynamics method in this work.The results indicate that the strength and plastic deformation mechanisms are strongly dependent on those determinants.Yield stresses of Ti/Ni nanolaminates decrease distinctly with increasing void diameter,while peak stresses with a void in the crystalline layer decrease with increasing d/h.Different void locations lead eventually to disparate initial plastic deformation carriers around the void,and various evolutions in the microstructure of the defective Ti/Ni nanolaminates.The Ti/Ni interface plays a significant role in the tensile process.The semi-coherent interface impedes new grains and lattice dislocations from passing across the interface,while the incoherent interface facilitates dislocations generating and sliding along the interface,and absorbs the dislocations moving to the interface.The results also indicate that the strain rate significantly affects the evolution of the microstructure and the tensile properties of defective Ti/Ni nanolaminates.
基金supported by Shenzhen-Hong Kong-Macao Science and Technology Program(Category C)(No.SGDX2020110309300301)Key R&D Program from the Science and Technology Department of Sichuan Province(Key Science&Technology Project)(No.2022YFSY0001)+1 种基金Changsha Municipal Science and Technology Bureau(No.kh2201035)the Innovation and Technology Commission of Hong Kong(No.GHP/221/21GD).
文摘Amorphous/nanocrystalline dual-phase structures have recently emerged as an effective way for over-coming the strength-ductility trade-offand breaking the limitation of the reverse Hall-Petch effect.Here,we proposed a new strategy to develop a hierarchical and interconnected amorphous-crystalline nanocomposite arising from the nanoscale elemental interdiffusion and oxygen adsorption behavior dur-ing thermal treatment processes.The nanocomposite consisted of a three-dimensional(3D)hierarchical network structure where the crystalline phase(Cr-Co-Ni-Al)was embedded into the Al-O-based amor-phous phase network with critical feature sizes encompassing three orders of magnitude(from microm-eter to nanometer scale).It can achieve ultrahigh compression yield strength of-3.6 GPa with large homogeneous deformation of over 50%strain.The massive interstitial atoms induced lattice distortion and hierarchical amorphous phase boundary contributed to the strength improvement.in situ Uniaxial compression inside a transmission electron microscope(TEM)revealed that the exceptional deformability of the nanocomposites resulted from the homogenous plastic flow of nano-sized amorphous phase and the plastic co-deformation behavior restricted by the nano-architected dual-phase interface.The proposed dual-phase synthesis approach can outperform conventional nanolaminates design strategies in terms of the mechanical properties achievable while providing a pathway to easily tune the microstructure of these nanolaminates.
基金supported by the National Natural Science Foundation of China(U2067219,92163201,52001247)the Initiative Postdocs Supporting Program(BX20190266)+1 种基金Shaanxi Province Youth Innovation Team Project(22JP042)the Fundamental Research Funds for the Central Universities(xtr022019004,xzy022019071)。
基金supported by the National Natural Science Foundation of China (Grant Nos.51722104,51625103,51790482,and 51761135031)the National Key Research and Development Program of China (2017YFA0700701)+3 种基金the 111 Project 2.0 of China(BP2018008)the Fok Ying-Tong Education Foundation (161096)the Fundamental Research Funds for the Central Universitiessupported by the Fundamental Research Funds for the Central Universities (xzy022019071)。
文摘Metastable high entropy alloys(HEAs) and amorphous metallic glasses(MGs), with the chemical disordered character, are intensively studied due to their excellent performance. Here, we introduce Cu to separately constrain these two metastable materials and comparatively investigate their deformation behaviors and mechanical properties of Cu/HEA Fe Co Cr Ni and Cu/MG Cu Zr nanolaminated micropillars in terms of intrinsic layer thickness h and extrinsic pillar diameter D. The metastable HEA layers, as the hard phase in Cu/HEA micropillars, are stable and dominate the deformation, while transformation(crystallization) occurs in MG which plays a minor role in deformation of Cu/MG micropillars. The h-controlled deformation mode transits from the D-independent homogenous-like deformation at large h to the Ddependent shear banding at small h in both Cu/HEA and Cu/MG micropillars. Although both Cu/HEA and Cu/MG micropillars exhibit a maximum strain hardening capability controlled by h, the former manifests much lower hardening capability compared with the latter. The intrinsic size h and extrinsic size D have a strong coupling effect on the strength of Cu/HEA and Cu/MG micropillars. The strength of strength of Cu/HEA micropillars exhibits the D-dependent transition from "smaller is stronger" to "smaller is weaker"with increasing h. By contrast, the strength of Cu/MG micropillars exhibits the transition from bulk-like D-independent behavior at large h to small volume D-dependent behavior(smaller is stronger) at small h.
基金Financial supports from the National Key Research and Development Program of China (No. 2017YFA0204401)Shenyang National Laboratory for Materials Science (No. 2015RP04)
文摘Nanolaminated structures composed of low-angle grain boundaries(LAGBs) possess high thermal stability. In this paper, a gradient nanolaminated(GNL) surface layer with smooth finish was fabricated on an interstitial-free steel by means of surface mechanical rolling treatment. Microstructural observations demonstrated that the average lamellar thickness is about 80 nm in the topmost surface layer and increases with increasing depth. High thermal stability was confirmed in the GNL surface layer after annealing at 500℃. Diffusion measurements showed that effective diffusivity of Cr in GNL layer is 4–6 orders of magnitude higher than lattice diffusivity within the temperature range from 400 to 500℃. This might be attributed to numerous LAGBs or dislocation structures with a higher energy state in the GNL surface layer. This work demonstrates the possibility to advanced chromizing(or other surface alloying)processes of steels with formation of GNL surface layer, so that a thicker alloyed surface layer with a stable nanostructure is achieved.
基金support by Latvia National Research Program IMIS 2 and France-LatviaOSMOSE Project no. LVFR/2017/3the support from Ministry of Science and Higher Education of Poland by the Polish-Portuguese bilateral projectsupport by a grant (No. S-LAT-17-1) from the Research Council of Lithuania
文摘Structural, electronic and mechanical properties of ZnO/Graphene(ZnO/G) nanolaminates fabricated by low temperature atomic layer deposition(ALD) and chemical vapor deposition(CVD) were investigated.We performed scanning and transmission electron microscopy(SEM/TEM), X-ray diffraction(XRD), electron energy loss spectroscopy(EELS), Raman spectroscopy, X-Ray photoelectron spectroscopy(XPS) and nanoindentation to characterize the ZnO/G nanolaminates. The main structural and mechanical parameters of ZnO/G nanolaminates were calculated. The obtained results were analyzed and interpreted taking into account mechanical interaction and charge effects occurring at the G-ZnO interface. The influence of graphene sublayers number on the mechanical behavior of the ZnO/G nanolaminates was studied. By reducing the bilayer thickness, the mechanical parameters of the films can be tuned(Young's modulus100-200 GPa, hardness 3-9 GPa). The softer response of the multilayers as compared to the single layers of ZnO and graphene was attributed to the structural changes in the ZnO layer and the interfaces. This study shows the mechanical behavior of ZnO/G nanolaminates and their influence on the development of novel electro-optical devices based on these structures.
基金supported by the National Special Support Program for Young Top-notch TalentNational Natural Science Foundation of China(No.61975215)+2 种基金Youth Innovation Promotion Association of the Chinese Academy of SciencesShanghai Young Top-notch Talent ProgramStrategic Priority Research Program of the Chinese Academy of Sciences(No.XDB16030400)。
文摘Different laminated structures of TiO_(2)/SiO_(2) composite film were prepared via atomic layer deposition(ALD)on alumina substrates.The effect of the annealing temperature in the air on the surface morphologies,crystal structures,binding energies,and ingredient content of these films was investigated using X-ray diffraction,field emission scanning electron microscopy,and X-ray photoelectron spectroscopy.Results showed that the binding energy of Ti and Si increased with decrease of the Ti content,and the TiO_(2)/SiO_(2) nanolaminated films exhibited a complex bonding structure.As the annealing temperature increased,the thickness of the nanolaminated films decreased,and the density and surface roughness increased.An increase in the crystallization temperature was proportional to the SiO_(2) content in TiO_(2)/SiO_(2) composite film.The annealing temperature and thin thickness strongly affected the phase structure of the ALD TiO_(2) thin film.To be specific,the TiO_(2) thin film transformed into an anatase phase from an amorphous phase after an increase in the annealing temperature from 400℃ to 550℃,and the TiO_(2) film exhibited an anatase phase until the annealing temperature reached 850℃,owing to its extremely small thickness.The annealing process caused the Al ions in the substrate to diffuse into the films and bond with 0.