In-Situ Observation and Mechanical Criterion on Interface Cracking in Nano-Components

2012 ◽  
Vol 1415 ◽  
Author(s):  
T. Kitamura ◽  
T. Sumigawa
Keyword(s):  
Mechanical Property ◽  
Fatigue Behavior ◽  
In Situ Observation ◽  
Displacement Curve ◽  
Si Substrate ◽  
Nano Scale ◽  
Cu Film ◽  
20 Nm ◽  
Interface Edge

ABSTRACTWe have investigated the criterion of interfacial crack initiation in nanometer-scale components (nano-components) by means of a loading facility built in a transmission electron microscope (TEM). Three types of experiments are conducted in this project. (1) In order to clarify the applicability of conventional continuum mechanics to the nano-components, we prepare cantilever specimens with different size, which introduce different stress fields, containing an interface between a 20 nm-thick copper (Cu) thin film and a silicon (Si) substrate. These demonstrate the validity of the “stress” criterion even for the nano-scale fracture. (2) In order to examine the effect of microscopic structure on the mechanical property, we fabricate a bending specimen in the nano-scale with thin Cu bi-crystal (the thickness of about 100 nm) formed on Si substrate, of which understructure can be observed in situ by means of a TEM during the mechanical experiment. The initial plastic deformation takes place near the interface edge in a grain with a high critical resolved shear stress and expands preferentially in the grain. Then, the plasticity appears near the between Cu grain boundary and Cu/Si interface, and this development brings about the interfacial cracking from the junction. These indicate the governing influence of understructure on the mechanical property in the nano-components. (3) In order to investigate the fatigue behavior of metal in a nano-component, a cyclic bending experiment is carried out using nano-cantilever specimens with a 20 nm-thick Cu constrained by highly rigid materials (Si and SiN). The high strain region is in the size of 20-40 nm near the interface edge. The specimen breaks along the Cu/Si interface before the maximum load under the fatigue loading. The load-displacement curve shows nonlinear behavior and a distinct hysteresis loop, indicating plasticity in the Cu film. Reverse yielding appearing after the 2nd cycle suggests the development of a cyclic substructure in the Cu film. These indicate that the crack is caused by characteristic understructure owing to fatigue cycles.

In-Situ Observation of Clay Minerals Hydrated and Intercalated With Liquid Chemicals Using Film-Sealed Environmental Cell

1980 ◽  
Vol 38 ◽  
pp. 208-209 ◽  
Author(s):  
K. Fukushima ◽  
N. Kohyama ◽  
A. Fukami
Keyword(s):  
Carbon Film ◽  
Resolving Power ◽  
In Situ Observation ◽  
Interlayer Water ◽  
Saturated Water ◽  
Structure Changes ◽  
Environmental Cell ◽  
Gas Layer ◽  
20 Nm

A film-sealed high resolution environmental cell(E.C) for observing hydrated materials had been developed by us(l). Main specification of the E.C. is as follows: 1) Accelerated voltage; 100 kV. 2) Gas in the E.C.; saturated water vapour with carrier gas of 50 Torr. 3) Thickness of gas layer; 50 μm. 4) Sealing film; evaporated carbon film(20 nm thick) with plastic microgrid. 5) Resolving power; 1 nm. 6) Transmittance of electron beam; 60% at 100 kV. The E.C. had been successfully applied to the study of hydrated halloysite(2) (3). Kaolin minerals have no interlayer water and are basically non-expandable but form intercalation compounds with some specific chemicals such as hydrazine, formamide and etc. Because of these compounds being mostly changed in vacuum, we tried to reveal the structure changes between in wet air and in vacuum of kaolin minerals intercalated with hydrazine and of hydrated state of montmori1lonite using the E.C. developed by us.

Study of Abrasive Wear Mechanism through Nano Machining

2011 ◽  
Vol 462-463 ◽  
pp. 931-936 ◽  
Author(s):  
Sumaiya Islam ◽  
Raafat N. Ibrahim ◽  
Raj Das
Keyword(s):  
Abrasive Wear ◽  
Wear Mechanism ◽  
Bulk Material ◽  
Elastic Recovery ◽  
In Situ Observation ◽  
Nano Scale ◽  
Nickel Coatings ◽  
Machining Operations ◽  
Tip Radius

The objective of this paper is to understand the abrasive wear mechanism for producing a nano scale groove on a bulk material through nano machining. A nano indenter equipped with a nano scratching attachment was used for nano machining operation and in situ observation of the machined surfaces. Two different tools (Berkovich and Conical) with the same tip radius (100nm) but different edge geometries were used to machine both Copper and Nickel coatings. It was found that the percentage of elastic recovery was lower for Cu than Ni during this nano machining operations. Hence, the deformation mechanism in nano machining operation was identified as elasto-plastic in nature as opposed to the well established completely plastic mode of conventional machining operations. The pile up volume due to plastic deformation was utilized to distinguish between the ploughing and cutting modes of abrasive wear mechanisms. The results reveal that the ploughing mechanism was dominant for Cu and the cutting mechanism was dominant for Ni machining. Moreover, both mechanisms ploughing and cutting were the dominant modes of abrasive wear using the Berkovich tip compared to the Conical tip for producing a nano scale groove through nano machining.

In-situ Observation of SUS 304 Stainless Steel on Fatigue Behavior in Hydrogen Environment

2003 ◽  
Vol 2003.56 (0) ◽  
pp. 3-4
Author(s):  
Takashi YOSHIMURA ◽  
Yasuji ODA ◽  
Tatsuhiko YOSHIMURA ◽  
Hiroshi NOGUCHI
Keyword(s):  
Stainless Steel ◽  
Fatigue Behavior ◽  
304 Stainless Steel ◽  
In Situ Observation ◽  
Hydrogen Environment

Investigation of the Tensile Fracture Behavior of Notched C/SiC Composite Using In Situ SEM and Micro-CT

2019 ◽  
Vol 298 ◽  
pp. 155-160
Author(s):  
Bai Hong Jiang ◽  
Yi Yu ◽  
Lei Zhang ◽  
Shi Zhang Yu ◽  
Xiao Jin Gao
Keyword(s):  
Failure Mechanism ◽  
Linear Part ◽  
Tensile Fracture ◽  
In Situ Observation ◽  
Displacement Curve ◽  
Micro Ct ◽  
Pull Out ◽  
Load Displacement ◽  
Sic Composites

In order to better understand the failure mechanism of C/SiC composites, the tensile behavior of notched C/SiC composites was investigated by the in-situ scanning electron microscopy (SEM) and the micro-CT technique. Surface morphologies of the C/SiC sample during tensile loading were in-situ observed by SEM, while the three-dimensional microscopic images of the C/SiC sample before loading and after failure were obtained by micro-CT. The results showed that no cracks formed in the initial elastic stage corresponding to the linear part of the load-displacement curve. However, corresponding to the following non-linear part of the load-displacement curve, matrix crack initiation, fiber pull-out, crack propagation and deflection appeared consecutively in the notched region of the sample. What’s more, different crack growth paths existed in different directions of the sample during tensile failure. In general, approximately flat fracture formed in the plying direction and serrated or stepped fracture were observed in the needling direction. It indicated that the in-situ observation method combining SEM and micro-CT can obtain the micro-structure images of the material in different states, which is helpful to analyze the fracture failure mechanism of composites.

Fabrication of Nanometer Sized Si Dot Arrays Using Ar Ion Milling with Calixarene Resist Dot Arrays

2010 ◽  
Vol 459 ◽  
pp. 116-119 ◽  
Author(s):  
Takuro Tamura ◽  
Yasunari Tanaka ◽  
Takashi Akahane ◽  
You Yin ◽  
Sumio Hosaka
Keyword(s):  
Electron Beam ◽  
Dry Etching ◽  
Ion Milling ◽  
Si Substrate ◽  
Etching Technique ◽  
Nano Scale ◽  
Vertical Milling ◽  
Scale Structures ◽  
20 Nm

In this study, we investigated the possibility of forming the fine Si dot arrays by means of electron beam (EB) lithography and dry etching technique for the future’s devices with nano-scale structures. We examined the properties of Ar ion milling for the fabrication of nanometer sized Si dot arrays on a Si substrate. We have succeeded in forming 40 nm pitched Si dot arrays with a diameter of <20 nm using dot array patterns of the calixarene resist as a mask. We also obtained the Ar ion milling property that there exists the horizontal milling rate as well as the vertical milling rate. We formed Si dot arrays with a dot diameter of about 10 nm using this property. It was clarified that Ar ion milling and EB lithography with calixarene resist has the potential to form Si nano dot arrays for the nano devices.

Low Temperature Synthesis of Carbon Nanotube on Si substrate Using Alcohol Gas Source in High Vacuum

2007 ◽  
Vol 1057 ◽  
Author(s):  
Takahiro Maruyama ◽  
Kenji Tanioku ◽  
Shigeya Naritsuka
Keyword(s):  
Low Temperature ◽  
Growth Temperature ◽  
Intensity Ratio ◽  
High Vacuum ◽  
In Situ Observation ◽  
Si Substrate ◽  
Growth Pressure ◽  
Gas Source ◽  
In Situ Observations

ABSTRACTConventional alcohol catalytic chemical vapor deposition (ACCVD) growth of carbon nanotubes (CNTs) have been carried out under ambient gases from 103 to105 Pa. These ambient gas pressures have prevented in situ observations using an electron beam during CNT growth, such as scanning electron microscopy (SEM), scanning tunneling microscopy (STM). Therefore, in order to realize the in situ observations and to clarify the growth mechanism of nanotube, CNT growth in a high vacuum is essential. In addition, the effects of residual gases also may be avoided in the growth under high vacuum. In this study, we carried out CNT growth under high vacuum using an alcohol gas source in an ultrahigh vacuum (UHV) chamber and we achieved CNT growth below 400°C without any excitation processes of carbon source. After deposition of Co catalyst of 1 nm in thickness on SiO2/Si substrate, ethanol gas was supplied to the substrate surface through a stainless steel nozzle in the UHV chamber. The growth temperature was monitored by a pyrometer during the growth, and set between 350 and 900°C. The supply of ethanol gas was controlled by monitoring an ambient pressure, which was varied from 1 ∼10-1 to 1 ∼10-4 Pa. The grown CNTs were characterized by SEM and Raman spectroscopy. The G/Si intensity ratio reached its maximum at 700°C, when the pressure was 1 ∼10-1 Pa. The maximum point of the G/Si peak intensity shifted to a lower temperature as the growth pressure decreased. When the pressure was 1 ∼10-4 Pa, the G/Si intensity ratio reached its maximum at 400°C, at which clear RBM peaks were observed in the Raman spectrum. From the RBM peaks, the CNT diameters were estimated to be between 0.9 to 1.7 nm, and CNTs of 1.2-1.4 nm in diameter were dominant at 1 ∼10-1 Pa, whereas thinner CNTs (diameter is below 1.0 nm) were increased with the reduction of the pressure. Our largest G/D ratio was about 40 for the sample grown at 1 ∼10-1 Pa, which is considerably larger than the reported value for the CNTs grown under low pressure. From these results, we conclude that the reduction of the growth pressure lowers the growth temperature. This technique can be applied to in situ observation, and may also be useful for low temperature growth of CNTs, which opens new possibilities for the fabrication of CNT based nanodevices.

Sign in / Sign up

Export Citation Format

Share Document