Search results for "Microscopy"
showing 10 items of 3390 documents
Graphene Oxide Carboxymethylcellulose Nanocomposite for Dressing Materials.
2020
Sore, infected wounds are a major clinical issue, and there is thus an urgent need for novel biomaterials as multifunctional constituents for dressings. A set of biocomposites was prepared by solvent casting using different concentrations of carboxymethylcellulose (CMC) and exfoliated graphene oxide (Exf-GO) as a filler. Exf-GO was first obtained by the strong oxidation and exfoliation of graphite. The structural, morphological and mechanical properties of the composites (CMCx/Exf-GO) were evaluated, and the obtained composites were homogenous, transparent and brownish in color. The results confirmed that Exf-GO may be homogeneously dispersed in CMC. It was found that the composite has an i…
Experimental Characterization of the Properties of Double-Lap Needled and Hybrid Joints of Carbon/Epoxy Composites
2015
The effect of through-thickness reinforcement by thin 1 mm steel needles (z-pins) on the static tensile strength of double-lap joints of a carbon/epoxy composite was investigated. Two types of joints—z-pinned and hybrid (including glued ones)—were considered. The joints were reinforced in the overlap region with 9, 25, or 36 z-pins. Comparing mechanical properties of the double-lap joints with the corresponding characteristics of their unpinned counterparts, the z-pins were found to be highly effective: the strength and stiffness of the pinned joints increased up to 300% and 280%, respectively. These improvements were due to a transition in the failure mechanism from debonding of the joint …
Molecular Scale Study of Domain Boundaries and Frictional Stick-Slip Motion on Lipid Bilayers
1995
A highly 2-dimensional (2D) anisotropic crystal formation of an organic one component lipid bilayer system is presented measured in air by atomic force microscopy. 2D domains with different crystal orientation could be observed. Their molecularly smooth domain boundaries are perceived to be either commensurable or incommensurable lattice joints. Differences in the orientation of the crystal lattice affects dynamic friction on the micrometer scale. High resolution friction images provide stick-slip motions depending on the scan direction in respect to the lattice orientation. It is shown that sliding friction can be determined by an averaged value of the molecular stick-slip motion of the fr…
Evidence for Graphene Edges Beyond Zigzag and Armchair
2009
The edges of nanoscopic objects determine most of their properties. For this reason the edges of honeycomb carbon--always considered either zigzag- or armchair-like--need special attention. In this report we provide experimental evidence confirming a previous unexpected prediction: zigzag is a metastable edge, as its planar reconstruction lowers energy and forms the most stable graphene edge. Our evidence is based on re-analyzing a recent experiment. Since the reconstructed edge, along with other unconventional edges we discuss, has distinct chemical properties, this discovery urges for care in experiments and theory--we must enter the realm beyond zigzag and armchair.
Micro-structure evolution of wall based crystals after casting of model suspensions as obtained from Bragg microscopy.
2012
Growth of heterogeneously nucleated, wall based crystals plays a major role in determining the micro-structure during melt casting. This issue is here addressed using a model system of charged colloidal spheres in deionized aqueous suspension observed by Bragg microscopy which is a combination of light scattering and microscopy. We examine the evolution of the three-dimensional size, shape, and orientation of twin domains in monolithic crystals growing from two opposing planar walls into a meta-stable (shear-) melt. At each wall crystal orientation and twinning emerges during nucleation with small domains. During growth these widen and merge. From image analysis we observe the lateral coars…
Maxwell and Sharvin conductance in gold point contacts investigated using TEM-STM
2000
We have investigated the conductance of gold point contacts using a scanning tunneling microscope ~STM! inside a transmission electron microscope ~TEM!. Measuring the conductance of these point contacts as a function of radius, we could directly compare it with theories both in the ballistic regime ~Sharvin! as well as in the diffusive regime ~Maxwell!. The width of the contacts were between a single atom and 20 nm. Using an interpolation formula ~Wexler! between the two limits, we obtain a mean free path of 4 nm, which is about ten times shorter than the room-temperature bulk value. The low value indicates an enhanced scattering, which is not due to high temperature in the point contact, i…
Temperature-driven spin reorientation transition inFe∕Mo(110)nanostructures
2007
Using low-temperature spin polarized scanning tunneling microscopy and spectroscopy, we observed a temperature-driven spin-reorientation transition (SRT) in Fe double layer (DL) nanostructures grown by step-flow growth on Mo(110). Magnetization components along the vertical and horizontal directions were detected with $4∕16$ ML Co∕10 ML $\mathrm{Au}∕\mathrm{W}(110)$ tips with out-of-plane (4 ML Co) and in-plane (16 ML Co) magnetic sensitivities. The magnetic easy axis of the Fe DL nanostructures continuously rotates from the vertical direction at $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ to an in-plane direction at $20\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The rotation angle is independent …
Nanoscale Domain Structure in Relaxor PLZT x/65/35 Ceramics
2006
We present the experimental study of the geometry of the nanoscale domain structure in classical lead zirconate-titanate relaxor ceramics (Pb1 − x La x )(Zr0.65Ti0.35)O3 (PLZT) with La concentration from 5 to 10%. The analysis of the switching current data measured in rectangular pulses indicates the existence of random three-dimensional maze-type domain structure. High-resolution domain visualization performed using Piezoresponse Force Microscopy (PFM) reveals nanoscale domain patterns. The domain structures existing in PLZT ceramics after zero-field-cooling represent the nanoscale quasi-regular maze (“finger-print”). Statistical and fractal analysis of PFM images was performed for quantit…
Critical currents and micro-structure in YBa2Cu3O7−δ thin films
1996
In an attempt to clarify the origin of the large critical current densitiesJ c observed in Laser Ablated and Sputtered YBa2Cu3O7−δ (YBCO) thin films, we make a systematic study of the low temperatureJ c in samples carefully analysed using STM and AFM.J c (B) is determined from torque-magnetometry performed in ring-patterned thin films. Epitaxial YBCO films nucleate in c-axis oriented single-crystalline islands with sizes ranging between 200 and 700 nm. We show thatJ c can be mainly explained by vortex pinning localised in the island boundaries.
Histotomography of the odontoblast processes at the dentine-enamel junction of permanent healthy human teeth in the confocal laser scanning microscope
1998
The translucency of teeth allows the non-destructive subsurface visualisation of their microstructure by confocal laser scanning microscopy (CLSM) at a level of about 150 μm below the surface. The dentine–enamel junction (DEJ) is accessible only directly adjacent to the cervix of the tooth. Therefore teeth have to be sectioned for studying marginal areas of the dental hard tissue. The potential of the technique for (pseudo) three-dimensional visualisation allows the study of an array of individual confocal images, the interpretation of which is similar to that of macroscopic tomographs (CT-scan, MRI). Additionally, the extended focus mode yields the overlay of individual confocal images in …