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Studium cesno-hafničitého chloridu metodami termické analýzy
Král, Robert; Zemenová, Petra; Bystřický, Aleš; Vaněček, Vojtěch; Kohoutková, M.
2018 - Czech
Tato práce se zabývá studiem procesů probíhajících při tepelném zatížení připraveného chloridu cesno-hafničitého (Cs2HfCl6) a jeho monokrystalu metodami termické analýzy: simultánní diferenciální skenovací kalorimetrií a termogravimetrií (DSC-TG) a termomechanickou analýzou (TMA). Výsledky prokázaly tepelnou nestabilitu Cs2HfCl6 a jeho rozklad na chlorid cesný a hafničitý nad eutektickou teplotou.\n This work deals with the study of processes in cesium hafnium chloride (Cs2HfCl6) and its single crystal under thermal treatment by thermal analyses (different scanning calorimetry, thermogravimetry and thermomechanical analysis). Results showed thermal instability of Cs2HfCl6 and its significant decomposition to cesium and hafnium chloride above the eutectic temperature.
Keywords:
Cs.sub.2./sub.HfCl.sub.6./sub.; DSC-TG; TMA; krystal
Available at various institutes of the ASCR
Studium cesno-hafničitého chloridu metodami termické analýzy
Tato práce se zabývá studiem procesů probíhajících při tepelném zatížení připraveného chloridu cesno-hafničitého (Cs2HfCl6) a jeho monokrystalu metodami termické analýzy: simultánní diferenciální ...
Modeling of monocrystalline magnesium microbeam bending
Němeček, J.; Maňák, Jan; Němeček, J.
2018 - English
This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to fit experimental load displacement curves.
Keywords:
magnesium; microbeams; crystal anisotropy; FE model
Available at various institutes of the ASCR
Modeling of monocrystalline magnesium microbeam bending
This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to ...
Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Stuchlík, Jiří; Fajgar, Radek; Kupčík, Jaroslav; Remeš, Zdeněk; Stuchlíková, The-Ha
2018 - English
Substrates with ZnO (or ITO) conductive layers were covered by thin film of a-Si:H deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to cover this a-Si:H thin film by germanium NPs. The RLA was performed using focused excimer ArF laser beam (193 nm, 100 mJ/pulse) under SiH4 background atmosphere (0.5 Pa). As a target the elemental germanium was used. Reaction between ablated Ge and silane led to formation of Ge NPs covered by thin SiGe layer. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes was alternated and applied a few times. The Si:H thin films with integrated Ge NPs were characterized by microscopic, spectroscopic and diffraction techniques. I-V characteristics of final diode structures without and under illumination were measured as well as their electroluminescence behaviour.
Keywords:
PECVD; a-Si:H diode structures; Ge; nanoparticles
Available at various institutes of the ASCR
Characterization of hydrogenated silicon thin films and diode structures with integrated germanium nanoparticles
Substrates with ZnO (or ITO) conductive layers were covered by thin film of a-Si:H deposited by PECVD technique. Under a turbo-molecular vacuum (10-4 Pa) the reactive laser ablation (RLA) was used to ...
Characterization of hydrogenated silicon thin films and diode structures with integrated silicon and germanium nanoparticles
Stuchlík, Jiří; Fajgar, R.; Remeš, Zdeněk; Kupčík, Jaroslav; Stuchlíková, Hana
2018 - English
P-I-N diode structures based on the thin films of amorphous hydrogenated silicon (a-Si:H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique were prepared with embedded Si and Ge nanoparticles. The Reactive Laser Ablation (RLA) of germanium target was used to cover the intrinsic a-Si:H layer by Ge NPs under a low pressure of the silane. The RLA was performed using focused excimer ArF laser beam under SiH4 background atmosphere. Reaction between ablated Ge NPs and SiH4 led to formation of Ge NPs covered by thin GeSi:H layer. The deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes were alternated repeatedly. Volt-ampere characteristics of final diode structures were measured in dark and under illumination as well as their electroluminescence spectra.
Keywords:
a-Si:H; PIN diode; thin films; reactive laser ablation; nanoparticles
Available at various institutes of the ASCR
Characterization of hydrogenated silicon thin films and diode structures with integrated silicon and germanium nanoparticles
P-I-N diode structures based on the thin films of amorphous hydrogenated silicon (a-Si:H) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique were prepared with embedded Si and Ge ...
Histology and micro-CT study of diamond-coated metal bone implants in rabbit femurs
Potocký, Štěpán; Ižák, Tibor; Dragounová, Kateřina; Kromka, Alexander; Rezek, Bohuslav; Mandys, V.; Bartoš, M.; Bačáková, Lucie; Sedmera, David
2018 - English
A conformal coating of a thin diamond layer on three-dimensional metal bone implants was shown directly on stainless steel and TiAl6V4 cortical screw implant using ultrasonic and composite polymer pretreatment method. The best conformation coverage was achieved in the case of the WO3 interlayer for both stainless steel and TiAl6V4 screws. The process of osteointegration of the screw implants into rabbit femurs is evidenced by the formation of a bone edge via desmogenous ossification around the screws in less than six months after implantation. A detailed evaluation of the tissue reaction around the implanted screws shows good biocompatibility of diamond-coated metal bone implants.
Keywords:
screw implant; diamond coating; osteointegration; histology
Available at various institutes of the ASCR
Histology and micro-CT study of diamond-coated metal bone implants in rabbit femurs
A conformal coating of a thin diamond layer on three-dimensional metal bone implants was shown directly on stainless steel and TiAl6V4 cortical screw implant using ultrasonic and composite polymer ...
Electronic transfer between nanostructures. Negative differential resistance in conductive polymers.
Král, Karel; Menšík, Miroslav
2018 - English
The effect of negative differential resistance can be observed experimentally in some material systems based on polymers. These observation are explained usually to be due to the presence of certain carrier traps which can capture the carriers of the electric current. In the present theoretical work we are going to show that besides this carrier trapping origin of the negative differential resistance there can also be an intrinsic mechanism present, causing such an effect. Namely, instead of the traps, the electron-phonon interaction can cooperate with the tunneling of the charge carriers between their localized states and can provide the effect the negative differential resistance. This electron-phonon interaction is included in a non-perturbative way. The theory will be briefly summarized and explained.
Keywords:
electronic transfer; charge transfer; nanostructures; quantum dots; nonequilibrium transport theory
Available at various institutes of the ASCR
Electronic transfer between nanostructures. Negative differential resistance in conductive polymers.
The effect of negative differential resistance can be observed experimentally in some material systems based on polymers. These observation are explained usually to be due to the presence of certain ...
Mechanical properties of Cr-DLC layers prepared by hybrid laser technology
Písařík, Petr; Jelínek, Miroslav; Remsa, J.; Tolde, Z.
2017 - English
Diamond like carbon (DLC) layers have excellent biological properties for use in medicine for coating implants, but poor adhesion to biomedical alloys (titanium alloys, chromium alloys and stainless steel). The adhesion can be improved by doping the DLC layer by chromium, as described in this article. Chromium doped diamond like carbon layers (Cr DLC) were deposited by hybrid deposition system using KrF excimer laser (deposition diamond like carbon - graphite target) and\nmagnetron sputtering (deposition chromium - chromium target). Carbon and chromium contents were determined by wavelength dispersive X-ray spectroscopy.\n
Keywords:
DLC; chromium doped; mechanical properties; PLD
Available at various institutes of the ASCR
Mechanical properties of Cr-DLC layers prepared by hybrid laser technology
Diamond like carbon (DLC) layers have excellent biological properties for use in medicine for coating implants, but poor adhesion to biomedical alloys (titanium alloys, chromium alloys and stainless ...
Correlated microscopy of electronic and material properties of graphene grown on diamond thin films
Rezek, Bohuslav; Čermák, Jan; Varga, Marián; Tulic, S.; Skákalová, V.; Waitz, T.; Kromka, Alexander
2017 - English
In this work we compare growth of graphene on diamond thin films that enable large area processing. We use films with different crystal size and surface roughness to obtain deeper insight into formation and properties of GoD. The diamond films are coated by a nm thin sputtered Ni layer and heated to 900°C in a forming gas atmosphere (H2/Ar) to initiate catalytic thermal CVD process. The samples are cleaned from residual Ni after the growth process. We employ scanning electron microscopy, Raman micro-spectroscopy and Kelvin probe force microscopy to correlate material, structural, and electronic properties of graphene on diamond. We show how grain size and grain boundaries influence graphene growth and material and electronic properties. For instance we show that the grain boundaries (with non-diamond carbon phases) in diamond films have an important role. They influence the electronic properties and they are beneficial for forming graphene on diamond higher quality.
Keywords:
graphene; diamond; microscopy; micro-spectroscopy; electronic properties
Available at various institutes of the ASCR
Correlated microscopy of electronic and material properties of graphene grown on diamond thin films
In this work we compare growth of graphene on diamond thin films that enable large area processing. We use films with different crystal size and surface roughness to obtain deeper insight into ...
Performance of cement composites reinforced with surface-modified polypropylene micro-fibers
Antoš, J.; Dejdar, L.; Trejbal, J.; Prošek, Zdeněk
2017 - English
This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ratio equal to 0.4). Two polypropylene fiber types (micro-and macro-fibers) were used as randomly distributed and oriented reinforcement in volume amount of 2 %. The fibers were modified in the low-pressure inductively coupled cold oxygen plasma in order to enhance their surface interaction with the cement matrix. The investigated composite mechanical properties (load bearing capacity and response during loading) were examined indirectly by means of four-point bending mechanical destructive tests. A response of loaded samples containing treated fibers were compared to samples with reference fibers. Moreover, cracking behavior development was monitored using digital image correlation (DIC). This method enabled to record the micro-cracks system evaluation of both fiber reinforced samples.\n
Keywords:
cement composite; fiber reinforcement; polymeric fiber; surface modification; four-point bending; plasma treatment
Available at various institutes of the ASCR
Performance of cement composites reinforced with surface-modified polypropylene micro-fibers
This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ...
Structure and properties of DLC layers for industrial applications
Mates, Tomáš; Ledinský, Martin; Vetushka, Aliaksi; Pikna, Peter; Fejfar, Antonín; Marek, A.; Vyskočil, J.; Erichsen, J.; Dawah, P.
2017 - English
Diamond-like carbon (DLC) layers based on amorphous carbon are used for wide range of applications, mostly for mechanical protection of various industrial components. We examined DLC layers at micro- and nanoscale by two independent microscopic techniques: Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) with a good agreement. We compared DLC layers grown on steel substrate and Si wafer and found similarly structured clusters and a certain difference in the density of nucleation centres. The measurements of local mechanical properties by the AFM tip revealed that the Si wafer behaves as softer material compared to the growing DLC nanoclusters that also exhibit lower values in the map of the relative local friction coefficient. Finally, we observed changes in the Raman spectra of the DLC exposed to annealing at ambient conditions and found a gradual shift from the diamond phase to the graphite phase as a function of increasing temperature.
Keywords:
DLC; PACVD; AFM; SEM; Raman
Available at various institutes of the ASCR
Structure and properties of DLC layers for industrial applications
Diamond-like carbon (DLC) layers based on amorphous carbon are used for wide range of applications, mostly for mechanical protection of various industrial components. We examined DLC layers at micro- ...
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