scholarly journals The Analysis of Micro-Scale Deformation and Fracture of Carbonized Elastomer-Based Composites by In Situ SEM

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 587
Author(s):  
Eugene S. Statnik ◽  
Semen D. Ignatyev ◽  
Andrey A. Stepashkin ◽  
Alexey I. Salimon ◽  
Dilyus Chukov ◽  
...  
Keyword(s):  
Structural Engineering ◽  
Elastic Moduli ◽  
Carbon Composite ◽  
Image Correlation ◽  
Butadiene Rubber ◽  
Sem Images ◽  
Micro Electro Mechanical Systems ◽  
Strength Limit ◽  
Before And After

Carbonized elastomer-based composites (CECs) possess a number of attractive features in terms of thermomechanical and electromechanical performance, durability in aggressive media and facile net-shape formability, but their relatively low ductility and strength limit their suitability for structural engineering applications. Prospective applications such as structural elements of micro-electro-mechanical systems MEMS can be envisaged since smaller principal dimensions reduce the susceptibility of components to residual stress accumulation during carbonization and to brittle fracture in general. We report the results of in situ in-SEM study of microdeformation and fracture behavior of CECs based on nitrile butadiene rubber (NBR) elastomeric matrices filled with carbon and silicon carbide. Nanostructured carbon composite materials were manufactured via compounding of elastomeric substance with carbon and SiC fillers using mixing rolling mill, vulcanization, and low-temperature carbonization. Double-edge notched tensile (DENT) specimens of vulcanized and carbonized elastomeric composites were subjected to in situ tensile testing in the chamber of the scanning electron microscope (SEM) Tescan Vega 3 using a Deben microtest 1 kN tensile stage. The series of acquired SEM images were analyzed by means of digital image correlation (DIC) using Ncorr open-source software to map the spatial distribution of strain. These maps were correlated with finite element modeling (FEM) simulations to refine the values of elastic moduli. Moreover, the elastic moduli were derived from unloading curve nanoindentation hardness measurements carried out using a NanoScan-4D tester and interpreted using the Oliver–Pharr method. Carbonization causes a significant increase of elastic moduli from 0.86 ± 0.07 GPa to 14.12 ± 1.20 GPa for the composite with graphite and carbon black fillers. Nanoindentation measurements yield somewhat lower values, namely, 0.25 ± 0.02 GPa and 9.83 ± 1.10 GPa before and after carbonization, respectively. The analysis of fractography images suggests that crack initiation, growth and propagation may occur both at the notch stress concentrator or relatively far from the notch. Possible causes of such response are discussed, namely, (1) residual stresses introduced by processing; (2) shape and size of fillers; and (3) the emanation and accumulation of gases in composites during carbonization.

scholarly journals Operando in-SEM Study of Micro-Deformation and Fracture Behaviour of Carbonized Elastomer-Based Composites

2020 ◽  
Author(s):  
Eugene S. Statnik ◽  
Semen D. Ignatyev ◽  
Andrey A. Stepashkin ◽  
Alexey I. Salimon ◽  
Dilyus Chukov ◽  
...  
Keyword(s):  
Structural Engineering ◽  
Elastic Moduli ◽  
Carbon Composite ◽  
Image Correlation ◽  
Sem Images ◽  
Strength Limit ◽  
Deformation And Fracture ◽  
Sem Study ◽  
Before And After ◽  
Micro Deformation

The carbonized elastomer-based composites (CECs) possess a number of attractive features in terms of thermomechanical and electromechanical performance, durability in aggressive media and facile net-shape formability, but their relatively low ductility and strength limit their suitability for structural engineering applications. Prospective applications such as structural elements of MEMS can be envisaged, since smaller principal dimensions reduce the susceptibility of components to residual stress accumulation during carbonization, and to brittle fracture in general. We report the results of operando in-SEM study of micro-deformation and fracture behavior of CECs based on NBR elastomeric matrices filled with carbon and silicon carbide. Nanostructured carbon composite materials were manufactured via compounding of elastomeric substance with carbon and SiC fillers using mixing rolling mill, vulcanization, and low-temperature carbonization. Double Edge Notched Tensile (DENT) specimens of vulcanized and carbonized elastomeric composites were subjected to in situ tensile testing in the chamber of the scanning electron microscope (SEM) Tescan Vega 3 using Deben Microtest 1 kN Tensile Stage. The series of acquired SEM images were analyzed by means of Digital Image Correlation (DIC) using Ncorr open source software to map the spatial distribution of strain. These maps were correlated with Finite Element Modelling (FEM) simulations to refine the values of elastic moduli. Besides, the elastic moduli were derived from unloading curve nanoindentation hardness measurements carried out using NanoScan-4D tester and interpreted using the Oliver-Pharr method. Carbonization causes significant increase of elastic moduli from 0.86 ± 0.07 to 14.12 ± 1.20 GPa for the composite with graphite and carbon black fillers. Nanoindentation measurements yield somewhat lower values, namely, 0.25 ± 0.02 GPa and 9.83 ± 1.10 GPa before and after carbonization respectively. The analysis of fractography images suggests that crack initiation, growth and propagation may occur both at the notch stress concentrator and relatively far from the notch. Possible causes of such response are discussed, namely, (1) residual stresses introduced by processing; (2) shape and size of fillers; and (3) the emanation and accumulation of gases in composites during carbonization.

scholarly journals Vacuum Casting and Mechanical Characterization of Nanocomposites from Epoxy and Oxidized Multi-Walled Carbon Nanotubes

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 510
Author(s):  
Gerald Singer ◽  
Philipp Siedlaczek ◽  
Gerhard Sinn ◽  
Patrick Kirner ◽  
Reinhard Schuller ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Mechanical Tests ◽  
Image Correlation ◽  
Sem Images ◽  
Vacuum Casting ◽  
Multi Walled Carbon Nanotubes ◽  
Properties Of Materials ◽  
Walled Carbon Nanotubes

Sample preparation is an important step when testing the mechanical properties of materials. Especially, when carbon nanotubes (CNT) are added to epoxy resin, the increase in viscosity complicates the casting of testing specimens. We present a vacuum casting approach for different geometries in order to produce specimens from functional nanocomposites that consist of epoxy matrix and oxidized multi-walled carbon nanotubes (MWCNTs). The nanocomposites were characterized with various mechanical tests that showed improved fracture toughness, bending and tensile properties performance by addition of oxidized MWCNTs. Strengthening mechanisms were analyzed by SEM images of fracture surfaces and in-situ imaging by digital image correlation (DIC).

scholarly journals Silane Treatment as an Effective Way of Improving the Reinforcing Activity of Carbon Nanofibers in Nitrile Rubber Composites

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3481
Author(s):  
Bolesław Szadkowski ◽  
Anna Marzec ◽  
Przemysław Rybiński
Keyword(s):  
Electrical Conductivity ◽  
Carbon Nanofibers ◽  
Ethanol Solution ◽  
Butadiene Rubber ◽  
Silane Treatment ◽  
Silane Coupling Agents ◽  
Sem Images ◽  
Silane Modification ◽  
Direct Incorporation

Two different silane treatment methods were used to improve the reinforcing activity of carbon nanofibers (CNF) in acrylonitrile-butadiene rubber (NBR) composites. The first method was chemical silanization with [3-(2-aminoethylamino)propyl]trimethoxysilane (APTS) in ethanol solution, preceded by oxidation of the CNF with H2SO4/HNO3. The second method was direct incorporation of silanes during preparation of the composites (in-situ silanization). Three different silane coupling agents were used: [3-(2-aminoethylamino)propyl]trimethoxysilane, (3-mercaptopropyl)trimethoxysilane (MPTS), and 3-ureidopropyltrimethoxysilane (UPTS). The NBR composites were prepared in an internal laboratory mixer, with increasing concentrations of pure or modified CNF. The crosslink density and flammability of the NBR-filled composites were analyzed, as well as their rheological and mechanical properties. The electrical conductivity of the composites was measured to assess the formation of CNF networks in the elastomer matrix. The morphology of the CNF was assessed by scanning electron microscopy (SEM). Both the dispersion of the CNF in the NBR matrix and the polymer-filler interactions were improved following silane modification, as shown in SEM images and by the Payne Effect. The composites were also found to have enhanced moduli, tensile strength, hardness, damping, and electrical conductivity. Chemical treatment proved to be more effective at improving the reinforcing effect of CNF in the elastomer matrix than in-situ silanization. The results of this study demonstrate the great potential of both in-situ and chemical silanization for the preparation of reinforced polymer composites filled with CNF.

scholarly journals Effect of the gold remodeling preparation method on the microstructure and mechanical behavior of steel

2020 ◽  
Vol 2 (10) ◽  
Author(s):  
Christian Oen Paulsen ◽  
Tore Børvik ◽  
Ida Westermann
Keyword(s):  
Elevated Temperatures ◽  
Preparation Method ◽  
Tensile Behavior ◽  
Image Correlation ◽  
Polished Surface ◽  
Dual Phase ◽  
Sem Images ◽  
Dp Steel ◽  
Successful Technique

Abstract The application of gold speckles on a polished surface is a successful technique for improving digital image correlation (DIC) contrast in scanning electron microscope (SEM) images. In the process of creating the gold speckles, the material is subjected to elevated temperatures for prolonged times. As a consequence, not all materials are suitable for the gold speckled method to improve the contrast for DIC measurements during an in-situ SEM tensile test. In this letter, the effect of gold remodeling on two different steels is investigated. These steels are a dual-phase (DP) steel and a ferrite–pearlite steel (NVE36). The results demonstrate that the temperature these steels are subjected to during gold remodeling will influence the tensile behavior of the DP steel while the NVE36 steel is unaffected by the heat treatment. As a result, we can conclude that the gold remodeling method for creating contrast in SEM images may affect the microstructure. However, the effect of these changes depends on the material at hand and will vary from material to material.

scholarly journals Thermoplastic Dynamic Vulcanizates with In Situ Synthesized Segmented Polyurethane Matrix

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1663 ◽  
Author(s):  
Andrea Kohári ◽  
István Zoltán Halász ◽  
Tamás Bárány
Keyword(s):  
Mechanical Properties ◽  
Butadiene Rubber ◽  
Scanning Calorimetry ◽  
Dynamic Vulcanization ◽  
Sem Images ◽  
Acrylonitrile Butadiene Rubber ◽  
Atomic Force ◽  
Rubber Particles ◽  
Rubber Phase

The aim of this paper was the detailed investigation of the properties of one-shot bulk polymerized thermoplastic polyurethanes (TPUs) produced with different processing temperatures and the properties of thermoplastic dynamic vulcanizates (TDVs) made by utilizing such in situ synthetized TPUs as their matrix polymer. We combined TPUs and conventional crosslinked rubbers in order to create TDVs by dynamic vulcanization in an internal mixer. The rubber phase was based on three different rubber types: acrylonitrile butadiene rubber (NBR), carboxylated acrylonitrile butadiene rubber (XNBR), and epoxidized natural rubber (ENR). Our goal was to investigate the effect of different processing conditions and material combinations on the properties of the resulting TDVs with the opportunity of improving the interfacial connection between the two phases by chemically bonding the crosslinked rubber phase to the TPU matrix. Therefore, the matrix TPU was synthesized in situ during compounding from diisocyanate, diol, and polyol in parallel with the dynamic vulcanization of the rubber mixture. The mechanical properties were examined by tensile and dynamical mechanical analysis (DMTA) tests. The morphology of the resulting TDVs was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM) and the thermal properties by differential scanning calorimetry (DSC). Based on these results, the initial temperature of 125 °C is the most suitable for the production of TDVs. Based on the atomic force micrographs, it can be assumed that phase separation occurred in the TPU matrix and we managed to evenly distribute the rubber phase in the TDVs. However, based on the SEM images, these dispersed rubber particles tended to agglomerate and form a quasi-continuous secondary phase where rubber particles were held together by secondary forces (dipole–dipole and hydrogen bonding) and can be broken up reversibly by heat and/or shear. In terms of mechanical properties, the TDVs we produced are on a par with commercially available TDVs with similar hardness.

scholarly journals Deformation mechanism of neutron irradiated Al-B based on SEM-DIC

2022 ◽  
Vol 355 ◽  
pp. 01004
Author(s):  
Jiaqi Xiang ◽  
Qijie Feng ◽  
Junchao Cheng ◽  
Lei Lu ◽  
Junyu Huang ◽  
...  
Keyword(s):  
Slip Band ◽  
Electron Backscatter Diffraction ◽  
Image Correlation ◽  
High Concentration ◽  
Helium Bubbles ◽  
Band Area ◽  
Transmission Electron ◽  
Before And After ◽  
Backscatter Diffraction

The electron backscatter diffraction (EBSD) characterization of irradiated Al-B shows that there is a high concentration defect region around the borides. Nanoscale speckle particles were successfully prepared on the surface of Al-B before and after irradiation, and then the mesoscale strain during in-situ deformation was obtained by digital image correlation (DIC) technique. The results shows that slip band bypass such an area through cross slips with slip band deflection. Transmission electron microscopy (TEM) indicates that abundant helium bubbles exist in the deflected slip band area pinning the dislocations.

In-situ Modification of Graphene Oxide by Insoluble Sulfur and Application for Nitrile Butadiene Rubber

2020 ◽  
Vol 35 (2) ◽  
pp. 221-228
Author(s):  
S.-B. Chen ◽  
T.-X. Li ◽  
S.-H. Wan ◽  
X. Huang ◽  
S.-W. Cai ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Butadiene Rubber ◽  
Nitrile Butadiene Rubber ◽  
In Situ Modification

Real-life Field Studies of the NOx Removing Properties of Photocatalytic Surfaces in Roskilde and Copenhagen Airport, Denmark

2020 ◽  
Vol 01 ◽  
Author(s):  
Henrik Jensen ◽  
Pernille D. Pedersen
Keyword(s):  
Air Quality ◽  
High Stability ◽  
Reference Site ◽  
Real Life ◽  
Field Studies ◽  
The Real ◽  
Before And After ◽  
Parking Lot ◽  
Photocatalytic Concrete

Aims: To evaluate the real-life effect of photocatalytic surfaces on the air quality at two test-sites in Denmark. Background: Poor air quality is today one of the largest environmental issues, due to the adverse effects on human health associated with high levels of air pollution, including respiratory issues, cardiovascular disease (CVD), and lung cancer. NOx removal by TiO2 based photocatalysis is a tool to improve air quality locally in areas where people are exposed. Methods: Two test sites were constructed in Roskilde and Copenhage airport. In Roskilde, the existing asphalt at two parking lots was treated with TiO2 containing liquid and an in-situ ISO 22197-1 test setup was developed to enable in-situ evaluation of the activity of the asphalt. In CPH airport, photocatalytic concrete tiles were installed at the "kiss and fly" parking lot, and NOx levels were continuously monitored in 0.5 m by CLD at the active site and a comparable reference site before and after installation for a period of 2 years. Results: The Roskilde showed high stability of the photocatalytic coating with the activity being largely unchanged over a period of 2 years. The CPH airport study showed that the average NOx levels were decreased by 12 % comparing the before and after NOx concentrations at the active and reference site. Conclusion: The joined results of the two Danish demonstration projects illustrate a high stability of the photocatalytic coating as well as a high potential for improvements of the real-life air quality in polluted areas.

scholarly journals Digital Image Correlation for Evaluation of Cracks in Reinforced Concrete Bridge Slabs

2021 ◽  
Vol 6 (7) ◽  
pp. 99
Author(s):  
Christian Overgaard Christensen ◽  
Jacob Wittrup Schmidt ◽  
Philip Skov Halding ◽  
Medha Kapoor ◽  
Per Goltermann
Keyword(s):  
Reinforced Concrete ◽  
Digital Image Correlation ◽  
Crack Initiation ◽  
Laboratory Test ◽  
Digital Image ◽  
Crack Detection ◽  
Image Correlation ◽  
In Situ Tests ◽  
Stop Criterion

In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.

scholarly journals Nanocomposites of Polyaniline and Cellulose Nanocrystals Prepared in Lyotropic Chiral Nematic Liquid Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Dawei Zhang ◽  
Lihong Zhang ◽  
Bingzhe Wang ◽  
Guangzhe Piao
Keyword(s):  
Liquid Crystals ◽  
Cellulose Nanocrystals ◽  
Nematic Liquid Crystals ◽  
Weight Ratio ◽  
Asymmetric Reaction ◽  
Reaction Field ◽  
Electron Microscopies ◽  
Chiral Nematic ◽  
Before And After

Stable lyotropic chiral nematic liquid crystals (N*-LCs) of cellulose nanocrystals (CNs) were prepared via hydrolysis using sulfuric acid. The lyotropic N*-LCs were used as an asymmetric reaction field to synthesize polyaniline (PANI) onto CNs by in situ polymerization. As a primary step, we examined the mesophase transition of the N*-LCs of CNs suspension before and after in situ polymerization of aniline (ANI) by polarizing optical microscopy. The structure of nanocomposites of PANI/CNs was investigated at a microscopic level using Fourier transform infrared spectroscopy and X-ray diffraction. Influence of the CNs-to-ANI ratio on the morphology of the nanocomposites was also investigated at macroscopic level by scanning electron and transmission electron microscopies. It is found that the weight ratio of CNs to aniline in the suspension significantly influenced the size of the PANI particles and interaction between CNs and PANI. Moreover, electrical properties of the obtained PANI/CNs films were studied using standard four-probe technique. It is expected that the lyotropic N*-LCs of CNs might be available for an asymmetric reaction field to produce novel composites of conjugated materials.

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