scholarly journals Chitosan Hydrogels Crosslinked by Genipin and Reinforced with Cellulose Nanocrystals: Production and Characterization

2019 ◽  
Vol 3 (3) ◽  
pp. 84 ◽  
Author(s):  
Andréia Aparecida do Nascimento Pomari ◽  
Thaís Larissa do Amaral Montanheiro ◽  
Cristiane Pereira de Siqueira ◽  
Rodrigo Sousa Silva ◽  
Dayane Batista Tada ◽  
...  
Keyword(s):  
Cellulose Nanocrystals ◽  
Crosslinking Agent ◽  
Nanocomposite Hydrogel ◽  
Compression Tests ◽  
Sem Images ◽  
Force Microscopy ◽  
Nanocomposite Hydrogels ◽  
Atomic Force ◽  
Significant Difference ◽  
Chitosan Hydrogels

In this work, chitosan hydrogels crosslinked with genipin and reinforced with cellulose nanocrystals (CNC) were developed and characterized with the aim of future biomedical applications. CNC was produced by acid hydrolysis and characterized by atomic force microscopy (AFM). Chitosan/CNC nanocomposite hydrogels were produced with different CNC concentrations (w/w): 0%, 2%, 4%, and 6%. The genipin was used as a crosslinking agent in a genipin/chitosan molar proportion of 1:8. The hydrogels were characterized by porosity measurements, scanning electron microscopy (SEM), swelling test, and mechanical compression test. No significant differences were observed concerning the porosity of the hydrogels; however, a trend of decreasing porosity was observed with increasing CNC content. The SEM images showed a better pore structure as the CNC concentration increased. A decrease in the swelling degree with increasing CNC content in the chitosan/CNC nanocomposite hydrogel was verified in the swelling tests. An increase in the CNC concentration in the chitosan/CNC nanocomposite hydrogel caused a gradual increase in the maximum stress and maximum strain as observed in the compression tests, showing a significant difference between chitosan/CNC 6 wt % and neat chitosan hydrogel.

scholarly journals Comparison of the Enamel Surface Roughness from Different Polishing Methods: Scanning Electron Microscopy and Atomic Force Microscopy Investigation

2020 ◽  
Vol 14 (02) ◽  
pp. 299-305
Author(s):  
Kiatanan Sugsompian ◽  
Ratchawan Tansalarak ◽  
Thosapol Piyapattamin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Enamel Surface ◽  
Similar Data ◽  
Force Microscopy ◽  
Atomic Force ◽  
Significant Difference ◽  
Scanning Electron

Abstract Objective This study aimed to compare the enamel surface roughness created by four polishing methods after debonding, by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Materials and Methods Four experimental polishing groups (Sof-Lex disc, SD; sandblaster, SB; tungsten carbide bur, TB; and white stone bur, WB) and one control group were selected from 100 premolars (n = 20/group). The experimental teeth were bonded with a bracket, thermocycled, and debonded. Residual adhesive was removed by either of the respective methods. Pre and postdebonding root mean square (Rq) values were obtained from AFM evaluations. All specimens were examined and evaluated with SEM using a modified enamel surface index (modified ESI). Statistical Analysis Differences among the polishing methods were compared with analysis of variance and Fisher’s least significant difference test at p < 0.05. Results Both microscopic evaluations indicated that the surface with the greatest roughness herein belonged to the SD group, followed by that for SB, TB, and WB groups. AFM measurements indicated a maximum postdebonding Rq herein for the WB group and a significantly greater surface roughness for the TB and WB groups than for the SD and SB groups. Among the experimental groups, SEM followed by modified ESI evaluations revealed similar data to those obtained with AFM. Significant differences were seen among all paired groups, except for that between the SB and TB groups. Conclusion Within the limitations of this study, all four polishing methods were concluded to be clinically acceptable for removing residual orthodontic adhesives.

scholarly journals Estimating Step Heights from Top-Down SEM Images

2019 ◽  
Vol 25 (4) ◽  
pp. 903-911 ◽  
Author(s):  
Kerim Tugrul Arat ◽  
Jens Bolten ◽  
Aernout Christiaan Zonnevylle ◽  
Pieter Kruit ◽  
Cornelis Wouter Hagen
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Semiconductor Industry ◽  
Step Edge ◽  
Step Height ◽  
Top Down ◽  
Sem Images ◽  
Force Microscopy ◽  
Atomic Force ◽  
Primary Electrons

AbstractScanning electron microscopy (SEM) is one of the most common inspection methods in the semiconductor industry and in research labs. To extract the height of structures using SEM images, various techniques have been used, such as tilting a sample, or modifying the SEM tool with extra sources and/or detectors. However, none of these techniques focused on extraction of height information directly from top-down images. In this work, using Monte Carlo simulations, we studied the relation between step height and the emission of secondary electrons (SEs) resulting from exposure with primary electrons at different energies. It is found that part of the SE signal, when scanning over a step edge, is determined by the step height rather than the geometry of the step edge. We present a way to quantify this, arriving at a method to determine the height of structures from top-down SEM images. The method is demonstrated on three different samples using two different SEM tools, and atomic force microscopy is used to measure the step height of the samples. The results obtained are in qualitative agreement with the results from the Monte Carlo simulations.

Rod- and sphere-shaped cellulose nanocrystals (CNCs) type-II derived from Asclepias Syriaca stem residues: Composition, Morphology and Thermal properties.

2020 ◽  
Author(s):  
Jérémy Astruc ◽  
Michel Grandbois ◽  
Gaétan Laroche ◽  
Mathieu Robert ◽  
Said Elkoun
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscopy ◽  
Cellulose Nanocrystals ◽  
Cellulose Content ◽  
Cellulose Ii ◽  
Type Ii ◽  
Cellulose I ◽  
Asclepias Syriaca ◽  
Force Microscopy ◽  
Atomic Force

Cellulose nanocrystals or nanoparticles (CNCs) has drawn a lot of attention due to their abundance, biocompatibility, renewability and their excellent mechanical properties paving the way to innovative and sustainable applications. In the present work, the stem residues of Asclepias Syriaca, better known as milkweed and generally regarded as a weed, was used for the first time to extract CNCs with a crystalline structure type-II (CNCs-II). Structural, thermal, morphological and mechanical properties of extracted CNCs-II were characterized by means of Fourier Transform Infrared (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Thermogravimetric Analysis (TGA) and Atomic Force Microscopy (AFM). Asclepias Syriaca stem fibers revealed quite similar cellulose content as compared to other milkweed species and, stable suspensions made of nanosphere- and nanorod- shape CNCs-II were successfully extracted from raw milkweed fibers. In addition, after conversion from cellulose-I to cellulose-II by mercerization, milkweed cellulose-II exhibited higher thermal resistance as compared to cellulose-I with degradation temperature at 328 °C and 310 °C respectively. Finally, the transversal elastic modulus of individuals CNCs-II, as measured by atomic force microscopy, was found to be in the range of 3.5-27 GPa which is consistent with reported values for CNCs-I or -II in the literature.

scholarly journals Atomic Force Microscopy Study of Discrete Dislocation Pile-ups at Grain Boundaries in Bi-Crystalline Micro-Pillars

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 411
Author(s):  
Xiaolei Chen ◽  
Thiebaud Richeton ◽  
Christian Motz ◽  
Stéphane Berbenni
Keyword(s):  
Atomic Force Microscopy ◽  
Microscopy Study ◽  
Anisotropic Elasticity ◽  
Critical Force ◽  
Face Centered Cubic ◽  
Compression Tests ◽  
Free Surfaces ◽  
Force Microscopy ◽  
Atomic Force ◽  
Micro Pillars

Compression tests at low strains were performed to theoretically analyze the effects of anisotropic elasticity, misorientation, grain boundary (GB) stiffness, interfacial dislocations, free surfaces, and critical force on dislocation pile-ups in micro-sized Face-Centered Cubic (FCC) Nickel (Ni) and α -Brass bi-crystals. The spatial variations of slip heights due to localized slip bands terminating at GB were measured by Atomic Force Microscopy (AFM) to determine the Burgers vector distributions in the dislocation pile-ups. These distributions were then simulated by discrete pile-up micromechanical calculations in anisotropic bi-crystals consistent with the experimentally measured material parameters. The computations were based on the image decomposition method considering the effects of interphase GB and free surfaces in multilayered materials. For Ni and α -Brass, it was found that the best predicted step height spatial profiles were obtained considering anisotropic elasticity, free surface effects, a homogeneous external stress and a certain critical force in the material to equilibrate the dislocation pile-ups.

Structural and mechanical properties of tantalum thin films ected by nitrogen ion implantation

2020 ◽  
Vol 34 (15) ◽  
pp. 2050163 ◽  
Author(s):  
A. H. Ramezani ◽  
S. Hoseinzadeh ◽  
Zh. Ebrahiminejad
Keyword(s):  
Friction Coefficient ◽  
Wear Mechanism ◽  
Mechanism Study ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Force Microscopy ◽  
Atomic Force ◽  
Coefficient Measurement ◽  
Nitrogen Ions ◽  
Nitrogen Ion

Tantalum bulk were implanted with nitrogen ions at different dose of [Formula: see text] ions/cm2 to [Formula: see text] ions/cm2 and at a energy 30 keV. The implanted samples were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), microhardness testing, friction coefficient measurements and wear mechanism study. Scanning electron microscopy (SEM) images were used to analyze the friction of samples. The XRD results confirmed that the increasing dose affects the formation of the TaN phase. Based on AFM images, the morphology and surface roughness change proportionally to grain size after implantation. It was found that hardness increases as energy increases. From the friction coefficient measurement, this coefficient decreases as energy increases. For the un-implanted sample, the wear mechanism has abrasion, and with increasing the energy, it shifts to being flake and sticky.

scholarly journals Comparative abrasive wear resistance and surface analysis of dental resin-based materials

2018 ◽  
Vol 12 (01) ◽  
pp. 057-066 ◽  
Author(s):  
Maleeha Nayyer ◽  
Shahreen Zahid ◽  
Syed Hammad Hassan ◽  
Salman Aziz Mian ◽  
Sana Mehmood ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Structural Changes ◽  
Wear Testing ◽  
Dental Resin ◽  
Force Microscopy ◽  
Atomic Force ◽  
Custom Made ◽  
Significant Difference ◽  
Before And After ◽  
Roughness Analysis

ABSTRACT Objective: The objective of this study was to assess the surface properties (microhardness and wear resistance) of various composites and compomer materials. In addition, the methodologies used for assessing wear resistance were compared. Materials and Methods: This study was conducted using restorative material (Filtek Z250, Filtek Z350, QuiXfil, SureFil SDR, and Dyract XP) to assess wear resistance. A custom-made toothbrush simulator was employed for wear testing. Before and after wear resistance, structural, surface, and physical properties were assessed using various techniques. Results: Structural changes and mass loss were observed after treatment, whereas no significant difference in terms of microhardness was observed. The correlation between atomic force microscopy (AFM) and profilometer and between wear resistance and filler volume was highly significant. The correlation between wear resistance and microhardness were insignificant. Conclusions: The AFM presented higher precision compared to optical profilometers at a nanoscale level, but both methods can be used in tandem for a more detailed and precise roughness analysis.

Fabrication of a highly elastic nanocomposite hydrogel by surface modification of cellulose nanocrystals

RSC Advances ◽  
2015 ◽  
Vol 5 (18) ◽  
pp. 13878-13885 ◽  
Author(s):  
Dong Yang ◽  
Xinwen Peng ◽  
Linxin Zhong ◽  
Xuefei Cao ◽  
Wei Chen ◽  
...  
Keyword(s):  
Surface Modification ◽  
Cellulose Nanocrystals ◽  
Nanocomposite Hydrogel ◽  
Efficient Strategy ◽  
Nanocomposite Hydrogels

A new and efficient strategy was first employed to fabricate highly elastic nanocomposite hydrogels by surface modification of cellulose nanocrystals.

Optical and Structural Properties of Fluorine Doped SnO2 on Si (100) for Photovoltaic Application

2018 ◽  
Vol 13 (10) ◽  
pp. 1522-1532 ◽  
Author(s):  
S. Nivetha ◽  
K. Kaviyarasu ◽  
A. Ayeshamariam ◽  
N. Punithavelan ◽  
R. Perumalsamy ◽  
...  
Keyword(s):  
Spray Pyrolysis Technique ◽  
Energy Difference ◽  
Vital Role ◽  
X Ray Diffraction ◽  
Energy Storage Devices ◽  
Sem Images ◽  
Storage Devices ◽  
Force Microscopy ◽  
Photovoltaic Application ◽  
Atomic Force

Photovoltaic material plays a vital role in the production of energy storage devices, more specifically in solar cell fabrications. In this work, ITO:F-doped materials were coated over the silicon substrate through spray pyrolysis technique. X-ray diffraction studies were conducted for porous silicon (PSi) coated with ITO:F structures formed at different current densities. This pore formation is evident from the broad peak at 69.9°, revealing an amorphous-like nature but at the same location where the single crystalline peak also is observed. These pores are explicitly shown in the SEM images in which very fine surface fragments are observed. At 20 mA/cm2, well-defined porous patterns that were uniformly distributed over the surface were observed. The microstructures observed via atomic force microscopy for these PSi coated with ITO:F structures are randomly aligned and almost evenly distributed over the entire surface of these nanorods, which are approximately 40 nm. Radiative recombination of electrons from a level in the conduction band or its subband to a level at an energy difference of greater than 1.7 eV in the valance band or its subband will emit visible light.

scholarly journals Self-Assembly of Rice Bran Globulin Fibrils in Electrostatic Screening: Nanostructure and Gels

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lihua Huang ◽  
Yehui Zhang ◽  
Haibin Li
Keyword(s):  
Ionic Strength ◽  
Rice Bran ◽  
Self Assembly ◽  
Gel Properties ◽  
Sem Images ◽  
Force Microscopy ◽  
Atomic Force ◽  
Repulsive Forces ◽  
Low Ionic Strength ◽  
Kinetics Of

The effects of various ionic strengths and protein concentrations on the fibrils structure and gel properties of rice bran globulin (RBG) at pH 2.0 were investigated using atomic force microscopy (AFM), rheometer, and scanning electron microscope (SEM). AFM images showed the morphology of assembling RBG fibrils from strand beads to becoming branch clustered, when electrostatic repulsive forces attenuated gradually with increasing ionic strength. NaCl seems to accelerate the kinetics of fibrils formation, resulting in a significant increase in Th T fluorescence intensity. The increased ionic strengths promote particle size increasing and zeta potential decreasing synchronously. The percolation modelG'~C-Cpnbe used to calculate theoretical RBG gels concentration at various ionic strengths (0–500 mM), which decreased from 15.17 ± 0.63 to 2.26 ± 0.27 wt%. SEM images exhibited a granular mesh-like gel structure. A more homogenous structure occurred in low ionic strength. This study elucidates properties of RBG fibrils and gels as a bioactive material.

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