Effect of Film Thickness on Fracture Toughness of Amorphous Diamond-Like Carbon

2005 ◽  
Author(s):  
Krishna Jonnalagadda ◽  
Ioannis Chasiotis
Keyword(s):  
Fracture Toughness ◽  
Film Thickness ◽  
Sacrificial Layer ◽  
Thickness Dependence ◽  
Diamond Like Carbon ◽  
Specimen Thickness ◽  
Atomic Force ◽  
Fracture Tests ◽  
Cracked Specimens ◽  
First Time

Fracture toughness, KIC, measurements were conducted for the first time on hydrogen-free tetrahedral amorphous Diamond-like Carbon (ta-C) MEMS-scale specimens of different thicknesses. Uniform gage microscale specimens with mathematically sharp edge pre-cracks were prepared by microindentation on the SiO2 sacrificial layer. The radial-median crack from the indent propagated into the specimen generating a sharp pre-crack. The crack length was measured by an Atomic Force Microscope (AFM). Freestanding fracture specimens were then obtained by wet etching the SiO2 sacrificial layer. Microtensile tests were performed on the pre-cracked specimens under mode-I loading in fixed grip configuration. In order to investigate the specimen thickness dependence of KIC, fracture tests were conducted on specimens with thicknesses in the range of 0.5-3 μm. KIC was 4.25 ± 0.7 MPa m for 0.5 μm specimens, 4.4 ± 0.4 MPa m for 1 μm specimens, and 3.06 ± 0.17 MPa m for 3 μm thick specimens. The 25% lower fracture toughness of the 3 μm films points to a film thickness dependence of fracture toughness that was attributed to different through-the-thickness stresses in considerably thick ta-C films and compositional changes occurring during post-deposition processing.

scholarly journals Strength and Fracture Resistance of Amorphous Diamond-Like Carbon Films for MEMS

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
K. N. Jonnalagadda ◽  
I. Chasiotis
Keyword(s):  
Fracture Toughness ◽  
Mechanical Strength ◽  
Mixed Mode ◽  
Carbon Films ◽  
Mode I ◽  
Diamond Like Carbon ◽  
Specimen Thickness ◽  
Mode I Fracture Toughness ◽  
Theoretical Predictions ◽  
Failure Properties

The mechanical strength and mixed mode I/II fracture toughness of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) films, grown by pulsed laser deposition, are discussed in connection to material flaws and its microstructure. The failure properties of ta-C were obtained from films with thicknesses 0.5–3 μm and specimen widths 10–20 μm. The smallest test samples with 10 μm gage section averaged a strength of 7.3±1.2 GPa, while the strength of 20-μm specimens with thicknesses 0.5–3 μm varied between 2.2–5.7 GPa. The scaling of the mechanical strength with specimen thickness and dimensions was owed to deposition-induced surface flaws, and, only in the smallest specimens, RIE patterning generated specimen sidewall flaws. The mode I fracture toughness of ta-C films isKIc=4.4±0.4 MPam, while the results from mixed mode I/II fracture experiments with cracks arbitrarily oriented in the plane of the film compared very well with theoretical predictions.

scholarly journals The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3469
Author(s):  
Hamed Saghafi ◽  
Ali Nikbakht ◽  
Reza Mohammadi ◽  
Dimitrios Zarouchas
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Double Cantilever Beam ◽  
Thickness Effect ◽  
Toughening Mechanism ◽  
Geometrical Features ◽  
Electrospinning Method ◽  
Fracture Tests ◽  
Mat Thickness ◽  
First Time

The geometrical features of nanofibers, such as nanomat thickness and the diameter of nanofibers, have a significant influence on the toughening behavior of composite laminates. In this study, carbon/epoxy laminates were interleaved with polysulfone (PSF) nanofibrous mats and the effect of the PSF nanomat thickness on the fracture toughness was considered for the first time. For this goal, the nanofibers were first produced by the electrospinning method. Then, double cantilever beam (DCB) specimens were manufactured, and mode-I fracture tests were conducted. The results showed that enhancing the mat thickness could increase the fracture toughness considerably (to about 87% with the maximum thickness). The toughening mechanism was also considered by presenting a schematic picture. Micrographs were taken using a scanning electron microscope (SEM).

Mode–I Fracture Toughness of Tetrahedral Amorphous Diamond-like Carbon (ta-C) MEMS

2004 ◽  
Vol 854 ◽  
Author(s):  
K. Jonnalagadda ◽  
S.W. Cho ◽  
I. Chasiotis ◽  
T.A. Friedmann ◽  
J.P. Sullivan
Keyword(s):  
Fracture Toughness ◽  
Sacrificial Layer ◽  
Mode I ◽  
Diamond Like Carbon ◽  
Finite Width ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness ◽  
Linear Elastic ◽  
Tensile Tester ◽  
Custom Made

ABSTRACTMode-I fracture toughness studies were conducted on hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS specimens of various thicknesses. Mathematically sharp edge pre-cracks were generated through micro indentation on the Silicon dioxide sacrificial layer. An atomic force microscope (AFM) was employed to measure the precise length and orientation of each pre-crack. Upon wet etching and release the freestanding uniform width and varying thickness MEMS-scale specimens were tested in Mode-I using a custom-made micro-tensile tester. Fracture toughness values were computed from the test data using linear elastic fracture mechanics (LEFM) for a finite width specimen with an edge crack in the fixed grip loading configuration. The average Mode-I fracture toughness for 0.5 micron thick specimens was found to be while the average mode-I fracture toughness for 1 micron specimens was .

FRACTURE TOUGHNESS OF DIAMOND-LIKE CARBON FILMS

2001 ◽  
Vol 15 (04n05) ◽  
pp. 157-162 ◽  
Author(s):  
Q. R. HOU ◽  
J. GAO
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Film Thickness ◽  
Pulsed Laser ◽  
Carbon Films ◽  
Laser Deposition ◽  
Diamond Like Carbon ◽  
Deposition Method ◽  
Vickers Indentation ◽  
Different Temperatures

Diamond-like carbon films were deposited on silicon (111) substrates at different temperatures using a pulsed-laser deposition method. Vickers indentation was used to measure the fracture toughness of the deposited diamond-like carbon films. It is found that diamond-like carbon films deposited at low temperature (55°C and 100°C) were very brittle and the fracture toughness was a difficult parameter to measure. The fracture toughness of diamond-like carbon films deposited at 270°C increased with film thickness and the measured values were between 1.0 and 2.3 MPa m 1/2.

FILM THICKNESS DEPENDENCE OF HEAT TRANSMISSION INTO HELIUM

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-825-C6-827
Author(s):  
P. Taborek ◽  
M. Sinvani ◽  
M. Weimer ◽  
D. Goodstein
Keyword(s):  
Film Thickness ◽  
Thickness Dependence ◽  
Heat Transmission

An Study of Influence of Imperfections on the Delamination of Diamond-Like Carbon Films

2002 ◽  
Vol 719 ◽  
Author(s):  
Myoung-Woon Moon ◽  
Kyang-Ryel Lee ◽  
Jin-Won Chung ◽  
Kyu Hwan Oh
Keyword(s):  
Cross Sections ◽  
Focused Ion Beam ◽  
Imaging System ◽  
Ion Beam ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Glass Substrates ◽  
Atomic Force ◽  
Initiation And Propagation

AbstractThe role of imperfections on the initiation and propagation of interface delaminations in compressed thin films has been analyzed using experiments with diamond-like carbon (DLC) films deposited onto glass substrates. The surface topologies and interface separations have been characterized by using the Atomic Force Microscope (AFM) and the Focused Ion Beam (FIB) imaging system. The lengths and amplitudes of numerous imperfections have been measured by AFM and the interface separations characterized on cross sections made with the FIB. Chemical analysis of several sites, performed using Auger Electron Spectroscopy (AES), has revealed the origin of the imperfections. The incidence of buckles has been correlated with the imperfection length.

scholarly journals Structure-Properties Correlation of Cross-Linked Penicillin G Acylase Crystals

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 451
Author(s):  
Marta Kubiak ◽  
Janine Mayer ◽  
Ingo Kampen ◽  
Carsten Schilde ◽  
Rebekka Biedendieck
Keyword(s):  
Mechanical Stability ◽  
Structural Characteristics ◽  
Penicillin G ◽  
Bacillus Species ◽  
Diffusion Limitations ◽  
Small Water ◽  
Long Term Stability ◽  
Atomic Force ◽  
First Time

In biocatalytic processes, the use of free enzymes is often limited due to the lack of long-term stability and reusability. To counteract this, enzymes can be crystallized and then immobilized, generating cross-linked enzyme crystals (CLECs). As mechanical stability and activity of CLECs are crucial, different penicillin G acylases (PGAs) from Gram-positive organisms have proven to be promising candidates for industrial production of new semisynthetic antibiotics, which can be crystallized and cross-linked to characterize the resulting CLECs regarding their mechanical and catalytic properties. The greatest hardness and Young’s modulus determined by indentation with an atomic force microscope were observed for CLECs of Bacillus species FJAT-PGA CLECs (26 MPa/1450 MPa), followed by BmPGA (Priestia megaterium PGA, 23 MPa/1170 MPa) and BtPGA CLECs (Bacillus thermotolerans PGA, 11 MPa/614 MPa). In addition, FJAT- and BtPGA CLECs showed up to 20-fold higher volumetric activities compared to BmPGA CLECs. Correlation to structural characteristics indicated that a high solvent content and low number of cross-linking residues might lead to reduced stability. Furthermore, activity seems to be restricted by small water channels due to severe diffusion limitations. To the best of our knowledge, we show for the first time in this study that the entire process chain for the characterization of diverse industrially relevant enzymes can be performed at the microliter scale to discover the most important relationships and limitations.

scholarly journals Ductile failure analysis of epoxy resin plates containing multiple circular arc cracks by means of the equivalent material concept

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
M. Pourseifi ◽  
A. S. Rahimi
Keyword(s):  
Ductile Failure ◽  
Equivalent Material ◽  
Circular Arc ◽  
Equivalent Material Concept ◽  
Crack Tips ◽  
Fracture Tests ◽  
Polymeric Samples ◽  
Cracked Specimens ◽  
Brittle Fracture Criterion ◽  
Material Concept

AbstractDuctile failure of polymeric samples weakened by circular arc cracks is studied theoretically and experimentally in this research. Various arrangements of cracks with different arc angles are considered in the specimens such that crack tips experienced the mixed mode I/II loading conditions. Fracture tests are conducted on the multi-cracked specimens and their fracture loads are achieved. To provide the results, the equivalent material concept (EMC) is used in conjunction of dislocation method and a brittle fracture criterion such that there is no necessity for performing complex and time-consuming elastic-plastic damage analyses. Theoretical and experimental stress intensity factors are computed and compared with each other by employing the fracture curves which demonstrate the appropriate efficiency of proposed method to predict the tests results.

scholarly journals High resolution nanoscale chemical analysis of bitumen surface microstructures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ayse N. Koyun ◽  
Julia Zakel ◽  
Sven Kayser ◽  
Hartmut Stadler ◽  
Frank N. Keutsch ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Force Microscopy ◽  
Photo Oxidation ◽  
Atomic Force ◽  
Para Phase ◽  
Key Sites ◽  
Respective Surface ◽  
Surface Domains ◽  
Surface Microstructures ◽  
First Time

AbstractSurface microstructures of bitumen are key sites in atmospheric photo-oxidation leading to changes in the mechanical properties and finally resulting in cracking and rutting of the material. Investigations at the nanoscale remain challenging. Conventional combination of optical microscopy and spectroscopy cannot resolve the submicrostructures due to the Abbe restriction. For the first time, we report here respective surface domains, namely catana, peri and para phases, correlated to distinct molecules using combinations of atomic force microscopy with infrared spectroscopy and with correlative time of flight—secondary ion mass spectrometry. Chemical heterogeneities on the surface lead to selective oxidation due to their varying susceptibility to photo-oxidation. It was found, that highly oxidized compounds, are preferentially situated in the para phase, which are mainly asphaltenes, emphasising their high oxidizability. This is an impressive example how chemical visualization allows elucidation of the submicrostructures and explains their response to reactive oxygen species from the atmosphere.

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