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Electron beam welding at ISI Brno
Dupák, Libor; Zobač, Martin; Vlček, Ivan; Zobačová, Jitka
2018 - English
In vacuum technology, and especially in UHV, we often encounter the necessity of joining\nparts of various metals in combination with the demand for perfect vacuum tightness,\ncleanness of joints and minimum deformations. Electron beam welding belongs to the\nbest technologies capable of fulfilling such requirements.\nThe principle of electron beam welding is based on the transfer of the kinetic energy of the\nincident accelerated electrons to the welded material in the form of heat. The temperature in\nthe spot rises with the beam power density. At power densities as high as 104 - 106 W/mm2,\nthe melted material at the center of the focal point evaporates. This produces a vapor capillary surrounded by melted material that allows the beam to penetrate deeper and melt more material. The speed of the penetration can be much higher than the heat transfer by\nconduction into the surrounding material. This results in narrow melted area and typical knifelike\nprofile of the weld. Thanks to this effect the thermal deformations of welded\npieces are highly reduced to almost none. Small heat affected zone also allows welding near\nheat sensitive parts like sensors, ceramic feed-throughs and brazed joints.
Keywords:
electron beam welding
Available at various institutes of the ASCR
Electron beam welding at ISI Brno
In vacuum technology, and especially in UHV, we often encounter the necessity of joining\nparts of various metals in combination with the demand for perfect vacuum tightness,\ncleanness of joints and ...
Possibilites of a secondary electrons bandpass filter for standard SEM
Mika, Filip; Pokorná, Zuzana; Konvalina, Ivo; Khursheed, A.
2018 - English
Secondary electron filtering in Scanning Electron Microscope (SEM) has been in use for over\na decade. This technique uncovers interesting contrasts in an otherwise ordinary SEM image\nwhich can possibly be used for dopant concentration mapping or for discerning the slight molecular weight differences in apparently homogeneous organic materials. Secondary\nelectron filtering of semiconductor samples seems very promising as it may shed light on the mechanism of SEM image contrast between p-doped and n-doped semiconductors, possibly\nallowing to determine dopant concentration from SEM image alone.
Keywords:
secondary electron; filtering; imaging
Available at various institutes of the ASCR
Possibilites of a secondary electrons bandpass filter for standard SEM
Secondary electron filtering in Scanning Electron Microscope (SEM) has been in use for over\na decade. This technique uncovers interesting contrasts in an otherwise ordinary SEM image\nwhich can ...
Secondary electron hyper spectral imaging in helios nanolab - mapping materials properties or artefacts?
Rodenburg, C.; Masters, R.; Abrams, K.; Dapor, M.; Krátký, Stanislav; Mika, Filip
2018 - English
A link between peaks in secondary electron (SE) spectra and Electron Energy Loss Spectra\n(EELS) was shown decades ago. Also, materials properties (bulk modulus, band gap)\ncorrelate with the bulk plasmon position in EELS, and local modulus maps in carbon fibres\nhave been presented. If any features as result of plasmon decay into SE can be identified,\nSE spectroscopy combined with hyperspectral imaging could transform the SEM into a tool\nfor mapping materials properties with ground-breaking potential for nanotechnology. To\nbecome a reality, we first need to establish SE collection conditions spectra that represent a\nmaterial reliably. Second, we need to gain a better understanding of the processes involved in the SE emission processes.
Keywords:
secondary electrons; polymers; hyperspectral imaging
Available at various institutes of the ASCR
Secondary electron hyper spectral imaging in helios nanolab - mapping materials properties or artefacts?
A link between peaks in secondary electron (SE) spectra and Electron Energy Loss Spectra\n(EELS) was shown decades ago. Also, materials properties (bulk modulus, band gap)\ncorrelate with the bulk ...
Thickness determination of a cathodoluminescence active nanoparticles by means of Quantitative STEM imaging
Skoupý, Radim; Krzyžánek, Vladislav
2018 - English
Labeling of specimens by nanoscale probes is common approach of complex biological\nsystems exploration. Namely gold nanoparticles immuno-staining is well established method\nin electron microscopy. However, if more than two label sizes are used, the differentiation of\nindividual nanoparticles becomes difficult.\nThis can be overcome by cathodoluminescence (CL) active particles – nanophosphors where\nlabels recognition is done by wavelength of emitted light. This gives a great opportunity to\nuse advanced multi probe labeling within one sample.\nThere is a huge variety of nanophosphors: green fluorescent protein, quantum dots, ZnO\nnanoparticles, organic molecules, rare earth-doped nanophosphors etc. Therefore, in order\nto choose best type of nanophosphors for a given task, it is important to measure particles\nsize/thickness, as the CL intensity is proportional to the probe volume.
Keywords:
quantitative imaging; Monte Carlo
Available at various institutes of the ASCR
Thickness determination of a cathodoluminescence active nanoparticles by means of Quantitative STEM imaging
Labeling of specimens by nanoscale probes is common approach of complex biological\nsystems exploration. Namely gold nanoparticles immuno-staining is well established method\nin electron microscopy. ...
Gel Polymer Electrolytes Modified Nanoparticles or Copolymers and Polymerized in Magnetic and Electric Fields
Jahn, M.; Veselková, I.; Sedlaříková, M.; Zatloukal, M.; Bartušek, Karel
2018 - English
Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of electrochemistry. The gel polymer electrolyte is composed of a conductive component (liquid electrolyte) and the polymer component (methacrylate-based polymer). In this paper, I present fundamental characteristics of gel polymer electrolytes modified nanoparticles or copolymers and preparation of these gel polymer materials with nanoparticles or copolymers polymerized in electric and magnetic fields.
Keywords:
magnetic and electric fields; gel polymer electrolytes; nanoparticles
Available at various institutes of the ASCR
Gel Polymer Electrolytes Modified Nanoparticles or Copolymers and Polymerized in Magnetic and Electric Fields
Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of ...
Sixty years of the Institute os Scientific Instruments
Müllerová, Ilona
2018 - English
The Institute of Scientific Instruments (ISI) was established in 1957 as an institution providing instrumental equipment for other institutes of the Academy of Sciences, mainly in the field of electron microscopy, nuclear magnetic resonance and coherent optics. Three examples are shown in Figure 1. In the beginning the institute had only 83 employees, including the workshop which produced the electronics and all mechanical parts of the instruments. During the process of post-Communist transformation of the Academy of Sciences, which began in 1989, the development of entire instruments and devices was brought to a halt and scientific activities of our Institute focused on the methodology of probing the physical properties of matter in the above-mentioned main fields. New components of scientific instruments were developed that help push the limits of what hadpreviously been possible, continuing the long tradition of the Institute in these topics.
Keywords:
electron-microscopy; sem
Available at various institutes of the ASCR
Sixty years of the Institute os Scientific Instruments
The Institute of Scientific Instruments (ISI) was established in 1957 as an institution providing instrumental equipment for other institutes of the Academy of Sciences, mainly in the field of ...
Photolitography on flexible substrates
Urbánek, M.; Urbánek, P.; Kuřitka, I.; Kolařík, Vladimír
2018 - English
Nowadays preparation of structures on flexible substrates is highly demanded because of using this patterns in field of flexible electronics. This contribution deals with photolitographic procces for preparation of structures on flexible substrates. The method of photolitography enables to create designed patterns in various material (e.g. metals as conductive layers) on various substrates (silicon wafers, foils, etc.). First the designed pattern is exposed through the mask by UV light into polymer resist, then the pattern is transfered into metal layer by wet etching through the developed windows in resist. In this paper several patterns are prepared through the positive resist PMMA by photolitography into various metal layer (Cu, Al) on flexible substrates.
Keywords:
photolithography; flexible substrates; metal layer
Available at various institutes of the ASCR
Photolitography on flexible substrates
Nowadays preparation of structures on flexible substrates is highly demanded because of using this patterns in field of flexible electronics. This contribution deals with photolitographic procces for ...
Analysis of linear ion Paul traps using 3-D FEM and the azimuthal multipole expansion
Oral, Martin; Číp, Ondřej; Slodička, L.
2018 - English
Radiofrequency (RF) Paul traps are valuable in the design and in the operation of highly stable\noptical atomic clocks based on suitable trapped ions. The traditional setup involves a single\nion in an RF trap irradiated with a laser beam. The frequency of the laser light is then fine-tuned to match that of photons coming from an electronic transition in the atomic shell. The\nachievable frequency stability is about 10-17 for laser-cooled ions. However, the stability can be\nfurther improved by using heavy atoms (such as Thorium) and the more stable frequencies of\ntheir nuclear transitions, and by setting up so-called Coulomb crystals, to improve the frequency measurement statistics by increasing the number of reference atoms. These techniques and their combination could reach relative stabilities beyond 10-20.
Keywords:
linear ion traps; atomic clock; electric RF fields; simulation of electrostatic fields; finite element method; multipole field expansion; ion trajectories; particle tracing
Available at various institutes of the ASCR
Analysis of linear ion Paul traps using 3-D FEM and the azimuthal multipole expansion
Radiofrequency (RF) Paul traps are valuable in the design and in the operation of highly stable\noptical atomic clocks based on suitable trapped ions. The traditional setup involves a single\nion in ...
Orbital motion from optical spin: the extraordinary momentum of circularly polarized light beams
Svak, Vojtěch; Brzobohatý, Oto; Šiler, Martin; Jákl, Petr; Zemánek, Pavel; Simpson, Stephen Hugh
2018 - English
We provide a vivid demonstration of the mechanical effect of transverse spin momentum in an\noptical beam in free space. This component of the Poynting momentum was previously thought\nto be virtual, and unmeasurable. Here, its effect is revealed in the inertial motion of a probe\nparticle in a circularly polarized Gaussian trap, in vacuum. Transverse spin forces combine with\nthermal fluctuations to induce a striking range of non-equilibrium phenomena. With increasing\nbeam power we observe (i) growing departures from energy equipartition, (ii) the formation of\ncoherent, thermally excited orbits and, ultimately, (iii) the ejection of the particle from the trap.\nOur results complement and corroborate recent measurements of spin momentum in evanescent\nwaves, and extend them to a new geometry, in free space. In doing so, we exhibit fundamental,\ngeneric features of the mechanical interaction of circularly polarized light with matter. The work\nalso shows how observations of the under-damped motion of probe particles can provide detailed\ninformation about the nature and morphology of momentum flows in arbitrarily structured light\nfields as well as providing a test bed for elementary non-equilibrium statistical mechanics.
Keywords:
optical trapping; optical levitation; counter-propagating beams; optical spin
Available at various institutes of the ASCR
Orbital motion from optical spin: the extraordinary momentum of circularly polarized light beams
We provide a vivid demonstration of the mechanical effect of transverse spin momentum in an\noptical beam in free space. This component of the Poynting momentum was previously thought\nto be virtual, ...
In vivo study of diatom assemblages using low temperature method for ESEM
Tihlaříková, Eva; Neděla, Vilém; Fránková, Markéta
2017 - English
Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is predominantly based on the morphology of ornate silicified cell wall called frustule composed of two overlapping parts (thecae). This frustule displays intricate patterns and designs unique to each species. For these studies conventional scanning electron microscopy (SEM) was and still is widely used. This method requires cleaning of diatom frustules in strong acids and peroxides followed by conductive coating.This aggressive procedure removes protoplast and damages delicate structures. Environmental scanning electron microscopy (ESEM) brings advantages of observation of fresh diatom material that are presence of whole intact diatom cells, not only empty diatom frustules, extracellular mucilaginous diatom secrets (e.g. pads, stalks, tubes) and whole diatom assemblages directly in situ together with other algal assemblages (e.g. cyanobacteria or green algae). However, in diatom research, ESEM is used mainly for elimination of conductive coating and observation of these organisms in their native wet state adhered directly on the host plant is not yet common. The ESEM observation of native aquatic samples is usually affected with radiation damage that can be lovered by the use of special methods like the Low Temperature Method (LTM) for the ESEM.
Keywords:
ESEM; diatom; morphology; LTM
Available at various institutes of the ASCR
In vivo study of diatom assemblages using low temperature method for ESEM
Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is ...
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