Super-durable ultralong carbon nanotubes

Science ◽  
2020 ◽  
Vol 369 (6507) ◽  
pp. 1104-1106 ◽  
Author(s):  
Yunxiang Bai ◽  
Hongjie Yue ◽  
Jin Wang ◽  
Boyuan Shen ◽  
Silei Sun ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Fatigue Resistance ◽  
Fatigue Behavior ◽  
Acoustic Resonance ◽  
Test System ◽  
Measurement Methods ◽  
Small Samples ◽  
Service Lifetime ◽  
Resonance Test ◽  
Individual Cnts

Fatigue resistance is a key property of the service lifetime of structural materials. Carbon nanotubes (CNTs) are one of the strongest materials ever discovered, but measuring their fatigue resistance is a challenge because of their size and the lack of effective measurement methods for such small samples. We developed a noncontact acoustic resonance test system for investigating the fatigue behavior of centimeter-long individual CNTs. We found that CNTs have excellent fatigue resistance, which is dependent on temperature, and that the time to fatigue fracture of CNTs is dominated by the time to creation of the first defect.

scholarly journals Tension-Tension Fatigue Behavior of High-Toughness Zr61Ti2Cu25Al12 Bulk Metallic Glass

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2815
Author(s):  
Yu Hang Yang ◽  
Jun Yi ◽  
Na Yang ◽  
Wen Liang ◽  
Hao Ran Huang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Fatigue Resistance ◽  
Metallic Glasses ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Bulk Metallic Glasses ◽  
High Toughness

Bulk metallic glasses have application potential in engineering structures due to their exceptional strength and fracture toughness. Their fatigue resistance is very important for the application as well. We report the tension-tension fatigue damage behavior of a Zr61Ti2Cu25Al12 bulk metallic glass, which has the highest fracture toughness among BMGs. The Zr61Ti2Cu25Al12 glass exhibits a tension-tension fatigue endurance limit of 195 MPa, which is higher than that of high-toughness steels. The fracture morphology of the specimens depends on the applied stress amplitude. We found flocks of shear bands, which were perpendicular to the loading direction, on the surface of the fatigue test specimens with stress amplitude higher than the fatigue limit of the glass. The fatigue cracking of the glass initiated from a shear band in a shear band flock. Our work demonstrated that the Zr61Ti2Cu25Al12 glass is a competitive structural material and shed light on improving the fatigue resistance of bulk metallic glasses.

Surface Engineering of Polycrystalline Silicon Microelectromechanical Systems for Fatigue Resistance

2002 ◽  
Vol 729 ◽  
Author(s):  
C.L. Muhlstein ◽  
W.R. Ashurst ◽  
E.A. Stach ◽  
R. aboudian ◽  
R.O. Ritchie
Keyword(s):  
Stress Corrosion ◽  
Fatigue Resistance ◽  
Reaction Layer ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Fatigue Behavior ◽  
Ambient Air ◽  
Degradation Process ◽  
Native Oxide ◽  
Premature Failure

AbstractRecent research has established that for silicon structural films used in microelectromechanical systems (MEMS), the susceptibility to premature failure under cyclic fatigue loading originates from a degradation process that is confined to the surface oxide. In ambient air environments, a sequential, stress-assisted oxidation and stress-corrosion cracking process can occur within the native oxide on polycrystalline silicon (referred to as reaction-layer fatigue); for the structural films of micron-scale dimensions, such incipient cracking in the oxide can lead to catastrophic failure of the entire silicon component. Since the degradation process is intimately linked to the thin reaction layer on the silicon, modification of this surface and the access of the environment to it can dramatically alter the fatigue resistance of the material. The purpose of this paper is to evaluate the efficacy of modifying the fatigue behavior of polycrystalline silicon with alkene-based monolayers. Specifically, 2-μm thick polysilicon fatigue structures were coated with a monolayer film based on 1-octadecene and cyclically tested to failure in laboratory air. By applying the coating, the formation of the native oxide was prevented. Compared to the fatigue behavior of untreated polysilicon, the lives of the coated samples ranged from 105 to >1010 cycles at stress amplitudes greater than ∼90% of the ultimate strength of the film. The dramatic improvement in fatigue resistance was attributed to the monolayer inhibiting the formation of the native oxide and stress corrosion of the surface. It is concluded that the surprising susceptibility of thin structural silicon films to premature fatigue failure can be inhibited by such monolayer coatings.

ELECTRON BEAM INDUCED CARBONACEOUS DEPOSITION AS A LOCAL DIELECTRIC FOR CNT CIRCUITS

2011 ◽  
Vol 10 (04n05) ◽  
pp. 935-941
Author(s):  
T. VIJAYKUMAR ◽  
NARENDRA KURRA ◽  
G. U. KULKARNI
Keyword(s):  
Carbon Nanotubes ◽  
Electron Beam ◽  
Dielectric Layer ◽  
Chemical Process ◽  
Deposition Process ◽  
Electrical Contacts ◽  
Si Substrate ◽  
Individual Cnts ◽  
As If

Evaluating the electrical nature of carbon nanotubes (CNTs) from a collection requires establishing electrical contacts across individual CNTs lying on a dielectric layer. In this work, it is shown how a dielectric layer may be inserted underneath a chosen CNT. This has been accomplished by the electron beam induced carbonaceous deposition process in the presence of moisture and residual hydrocarbons present in the SEM chamber. When performed at a CNT location on a Si substrate, the CNT instead of getting buried underneath is found to be lifted on top of the carbonaceous platform, as if due to nonwetting nature of CNT surface. By fixing one end of the CNT on the Ag/Si substrate using a Pt deposit and lifting rest of the length to lie on a carbonaceous platform, the I–V data from nanotubes of varying resistances have been collected using conducting AFM. The chosen nanotubes have also been examined by Raman measurements. The method is particularly useful while working with a random collection of nanotubes resulting from a chemical process.

Fatigue behavior of stent in tapered arteries: The role of arterial tapering and stent material

2019 ◽  
Vol 233 (10) ◽  
pp. 989-998
Author(s):  
Xiang Shen ◽  
Hongfei Zhu ◽  
Song Ji ◽  
Jiabao Jiang ◽  
Yongquan Deng
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
High Efficiency ◽  
Fatigue Behavior ◽  
Great Success ◽  
Term Outcome ◽  
Long Term Outcome ◽  
Minimal Invasiveness ◽  
Goodman Diagram ◽  
Stent Material

Stenting has achieved great success in treating cardiovascular diseases due to its high efficiency and minimal invasiveness. However, fatigue of stents severely limits its long-term outcome. In this article, finite element method was adopted to study the effects of arterial tapering and stent material on the fatigue performance of stents. A series of tapered vessels with different taper levels and two sets of stents with different materials were modeled. The Goodman diagram was used to evaluate the fatigue resistance of stents. Results showed that the fatigue resistance of stents can be extremely improved by simply changing stent material. In addition, the taper of the arteries had an important influence on the fatigue resistance of the stent. The fatigue life of the stent will be shortened with the increase of the arterial taper. The method that predicted stent fatigue life in tapered vessels can help clinicians select stents that are more suitable for tapered vessels and help stent engineers design stents that are more resistant to fatigue.

Fatigue behavior of nanoscale Mo/W multilayers on flexible substrates

MRS Advances ◽  
2019 ◽  
Vol 4 (43) ◽  
pp. 2309-2317
Author(s):  
Fang Wang ◽  
Xue-Mei Luo ◽  
Dong Wang ◽  
Peter Schaaf ◽  
Guang-Ping Zhang
Keyword(s):  
Fatigue Resistance ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Properties ◽  
Individual Layer ◽  
Out Of Plane ◽  
Inclination Angles ◽  
Plane Direction ◽  
Columnar Grain ◽  
20 Nm

ABSTRACTFatigue properties of Mo/W multilayers with individual layer thickness (λ) of 5, 20, 50 and 100 nm on flexible polyimide substrates were investigated. The experimental results show that the fatigue resistance increases with decreasing λ from 100 nm to 20 nm, and reaches the maximum at λ=20 nm, and then decreases when further decreasing λ. Fatigue cracks of Mo/W multilayers with different λ were found to propagate along columnar grain boundary in the out-of-plane direction and along the boundary of cluster structures. The enhanced fatigue resistance is attributed to the larger cluster inclination angles and the more tortuous in-plane cracking paths.

Creep-Fatigue Resistance of a Nickel-Aluminide

1988 ◽  
Vol 133 ◽  
Author(s):  
J. K. Tien ◽  
R. S. Bellows
Keyword(s):  
Fatigue Resistance ◽  
Nickel Aluminide ◽  
Fatigue Behavior ◽  
Mean Stress ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Temperature Regimes ◽  
Creep Fatigue ◽  
The Matrix ◽  
Stress Damage

ABSTRACTA modified fatigue test matrix that provided both creep (high mean stress) and fatigue (alternating stress) damage was used to evaluate the creep-fatigue behavior of D.S. Ni3 Al(B,Hf). The three generic regimes of below, at, and above peak yield strength temperature were investigated. It was found that the creep-fatigue resistance of this intermetallic remains high through the three temperature regimes, allowing it to be further considered as a monolith or as the matrix of high-temperature fiber reinforced composite.

Study on Thermal Fatigue Resistance of Non-Smooth Cast Iron Treated by Laser Surface Alloying of CrNi Powders

2011 ◽  
Vol 291-294 ◽  
pp. 1405-1411
Author(s):  
Tong Xin ◽  
Zhou Hong ◽  
Liu Min
Keyword(s):  
Cast Iron ◽  
Fatigue Resistance ◽  
Thermal Fatigue ◽  
Fatigue Behavior ◽  
Laser Surface ◽  
Surface Alloying ◽  
Laser Melting ◽  
Cast Irons ◽  
Laser Surface Alloying ◽  
Thermal Fatigue Resistance

The past studies indicated that thermal fatigue resistance of cast irons could be improved by partly laser melting treatment. However the only disadvantage of this technology is that the enhancement of thermal fatigue resistance would be limited because of the fixed chemical composition of sample matrix. For this purpose, the laser surface alloying of CrNi was selected for changing both the compositions and the microstructures of laser treated zone, and the effects of alloy powder compositions on thermal fatigue behavior were also investigated in this paper. The results indicate that the alloy elements distribute homogeneously, and their contents increase markedly in the non-smooth unit on the alloyed layer. The non-smooth unit is strengthened further compared with laser melting treatment. Thermal fatigue resistance of cast iron is enhanced evidently by laser surface alloying of CrNi powders, and for all samples tested, those treated with 25%Cr-75%Ni powders have the best thermal fatigue resistance.

Nanomechanical Measurement Methods on the Basis of MEMS

2014 ◽  
Vol 651-653 ◽  
pp. 465-471
Author(s):  
Feng Luo ◽  
Liang Zhang ◽  
Zhi Kai Zhang
Keyword(s):  
Numerical Simulation ◽  
Finite Element Analysis ◽  
Microelectromechanical Systems ◽  
Test System ◽  
Measurement Methods ◽  
Test Results ◽  
Performance Parameters ◽  
Sensors And Actuators ◽  
Element Analysis ◽  
Measurement Systems

Recently microelectromechanical systems (MEMS) have found increasingly more applications in measurement technique in form of sensors and actuators. Here a report on the development and test of nanomechanical measurement methods and systems on the basis of MEMS will be delivered. A nanoforce actuator, a nanotensile test system which are all realized in the form of MEMS are in the focus. Design and numerical simulation of the nanoforce actuator with the help of finite element analysis (FEA) are detailed . In the article the principle of these measurement systems, the design, the manufacture and the assembly of the MEMS as well as first test results and achieved performance parameters are described.

scholarly journals Molecular Simulations of Cyclic Loading Behavior of Carbon Nanotubes Using the Atomistic Finite Element Method

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
Jianfeng Wang ◽  
Marte S. Gutierrez
Keyword(s):  
Finite Element Method ◽  
Carbon Nanotubes ◽  
Finite Element ◽  
Cyclic Loading ◽  
Large Strain ◽  
Fatigue Behavior ◽  
Dominant Role ◽  
Molecular Simulations ◽  
Viscoelastic Behavior ◽  
Element Method

The potential applications of carbon nanotubes (CNT) in many engineered bionanomaterials and electromechanical devices have imposed an urgent need on the understanding of the fatigue behavior and mechanism of CNT under cyclic loading conditions. To date, however, very little work has been done in this field. This paper presents the results of a theoretical study on the behavior of CNT subject to cyclic tensile and compressive loads using quasi-static molecular simulations. The Atomistic Finite Element Method (AFEM) has been applied in the study. It is shown that CNT exhibited extreme cyclic loading resistance with yielding strain and strength becoming constant within limited number of loading cycles. Viscoelastic behavior including nonlinear elasticity, hysteresis, preconditioning (stress softening), and large strain have been observed. Chiral symmetry was found to have appreciable effects on the cyclic loading behavior of CNT. Mechanisms of the observed behavior have been revealed by close examination of the intrinsic geometric and mechanical features of tube structure. It was shown that the accumulated residual defect-free morphological deformation was the primary mechanism responsible for the cyclic failure of CNT, while the bond rotating and stretching experienced during loading/unloading played a dominant role on the strength, strain and modulus behavior of CNT.

scholarly journals Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Dongsheng Wang ◽  
Junyan Yi ◽  
Decheng Feng
Keyword(s):  
Thin Film ◽  
Fatigue Behavior ◽  
Asphalt Binder ◽  
Low Frequency ◽  
Test System ◽  
Silica Content ◽  
Fatigue Performance ◽  
Adhesion Performance ◽  
Aggregate System

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

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