National Repository of Grey Literature 12 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Histology and micro-CT study of diamond-coated metal bone implants
Potocký, Štěpán ; Ižák, Tibor ; Dragounová, Kateřina ; Kromka, Alexander ; Rezek, Bohuslav ; Mandys, V. ; Bartoš, M. ; Bačáková, Lucie ; Sedmera, David
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.
The hydrogen plasma doping of ZnO thin films and nanoparticles
Remeš, Zdeněk ; Neykova, Neda ; Potocký, Štěpán ; Chang, Yu-Ying ; Hsu, H.S.
The optical absorptance and photoluminescence studies has been applied on the hydrogen and oxygen plasma treated, nominally undoped ZnO thin films and aligned nanocolumns grown on the nucleated glass substrate by the hydrothermal process in an oil bath containing a flask with ZnO nutrient solution. The localized defect states at 2.3 eV below the optical absorption edge were detected by photothermal deflection spectroscopy (PDS) in a broad spectral range from near UV to near IR. The optical absorptance spectroscopy shows that hydrogen doping increases free electron concentration changing ZnO to be electrically conductive (hydrogen doping).\n
Wettability enhancement of polymeric and glass micro fiber reinforcement by plasma treatment
Trejbal, J. ; Šmilauer, V. ; Kromka, Alexander ; Potocký, Štěpán ; Kopecký, L.
Plasma treatments were used to modify surface properties of polyethylene terephthalate (PET) and glass micro fibers, to improve their wettability. PET fibers, having diameter of 400 μm, and glass fibers (14 μm) were exposed to low pressure oxygen plasma. A direct horizontal optical method was used for contact angle measurements on fiber surfaces submerged into distilled water. Surface morphology changes before and after treatment were characterized by scanning electron microscopy. Finally, cement paste specimens reinforced with PET and lime-based mortars reinforced with glass fibers were made and after 28 days of mixture curing tested by four-point bending tests. After oxygen plasma treatment contact angles decreased by 60 % on PET fibers and by 25 % on glass fibers in comparison with untreated fibers. Next, SEM images revealed the significant surface damages of PET fibers and minor damages of glass fibers. Both four-point tested samples reinforced with treated fibers exhibited the maximum bending strength loss about to 10 to 20 percent compared to samples with untreated reinforcement.
Polymeric nanofibrous scaffolds reinforced with diamond and ceramic nanoparticles for bone tissue engineering
Bačáková, Lucie ; Pařízek, Martin ; Staňková, Ľubica ; Novotná, Katarína ; Douglas, T.E.L. ; Brady, M. A. ; Kromka, Alexander ; Potocký, Štěpán ; Stránská, D.
Three types of nanofibrous scaffolds were prepared by electrospining: (1) poly(lactide-co-glycoside) (PLGA) scaffolds reinforced with 23 wt.% of diamond nanoparticles (DNPs), (2) poly(L-lactide) (PLLA) scaffolds with DNPs in concentration ranging from from 0.4 wt.% to 12.3 wt.%, and (3) PLLA scaffolds with 5 wt.% or 15 wt.% of hydroxyapatite (HAp) nanoparticles. The diameter of the nanofibers ranged between 160 and 729 nm. The nanofibers with nanoparticles were thicker and the void spaces among them were smaller. Mechanical properties of the nanoparticle-loaded scaffolds were better, as demonstrated by a rupture test in scaffolds with DNPs and by a creep behavior test in scaffolds with HAp. On PLGA scaffolds with DNPs, the human osteoblast-like MG-63 cells adhered in similar numbers and grew with similar kinetics as on pure PLGA scaffolds. Human bone marrow mesenchymal stem cells grew faster and reached higher population densities on PLGA-DNP scaffolds. However, on PLLA-based scaffolds, the activity of mitochondrial enzymes and concentration of osteocalcin in MG-63 cells decreased with increasing DNP concentration. On the other hand, the metabolic activity of MG-63 cells and content of osteocalcin in these cells were positively correlated with the HAp concentration in PLLA scaffolds. Thus, PLGA nanofibers with 23 wt% of DNPs and PLLA nanofibers with 5 and particularly 15 wt.% of HAp seem to be promising for bone tissue engineering.
In situ XPS characterization of diamond films after AR.sup.+./sup. cluster ion beam sputtering
Artemenko, Anna ; Babchenko, Oleg ; Kozak, Halyna ; Ukraintsev, Egor ; Ižák, Tibor ; Romanyuk, Olexandr ; Potocký, Štěpán ; Kromka, Alexander
In this work, in situ XPS analysis of chemical composition of H- and O-terminated nano- and microcrystalline diamond (NCD and MCD) films before and after their sputtering by the Ar+ cluster ion beam was investigated. Scanning electron microscopy confirmed sputtering of all diamond surfaces with a rate about 0.5 nm/min. Raman spectroscopy and XPS revealed surface graphitization of diamond surface induced by sputtering. Moreover, XPS data showed the presence of about 0.7 % of Ar atoms on the investigated diamond surface after 66 min of sputtering. Also, oxygen residuals were still presented on the H-NCD surface after 66 min of sputtering. In contrast, no oxygen was found on the H-MCD surface just after 2 min of sputtering. Surface composition is discussed in respect to the diamond films growth parameters and surface structure.
General methodology for high temperature processes of semiconductor technology by the finite element methods
Jirásek, Vít ; Potocký, Štěpán ; Sveshnikov, Alexey
A general methodology for modeling of high-temperature reactors produced by SVCS Process Innovation, Ltd., using the finite element, resp. finite volume method, was developed. The methodology covers basics principles of working with SW packages for CFD modeling with the emphasis on the strongly coupled processes of chemically reacting fluid flow, mass and heat transport. An important part is devoted to the model-experiment relationship, verification and validation of models and comparison with experiments.
Growth of diamond thin films: a review
Kromka, Alexander ; Potocký, Štěpán ; Rezek, Bohuslav
Diamond is shown as an extraordinary material which offers promising solution for variety of fundamental studies and industrial uses. Here, growth of synthetic diamond films at low pressures (1 atm) and low temperatures (<1000°C) from carbon consisting gas mixtures is discussed. Variety of chemical vapor deposition techniques are reviewed, their advantages and disadvantages are pointed out too.
Study of nucleation and growth of diamond thin films
Ižák, Tibor ; Babchenko, Oleg ; Varga, Marián ; Potocký, Štěpán ; Marton, M. ; Vojs, M. ; Domonkos, Mária ; Kromka, Alexander
This study deals with the nucleation and growth of CVD diamond films on Si substrates. In nucleation part two different nucleation methods were studied: (i) the bias enhanced nucleation (BEN) and (ii) ultrasonic seeding. In the case of BEN, (i) the nucleation time and (ii) the influence of bias voltage were studied. For ultrasonic seeding the effect of different solutions of ultradisperzed detonation nanodiamond (UDD) powder with metal particles on the nucleation efficiency and growth process was investigated (i.e. diamond powder, nanosized Ni, microsized Co and Y metal powders).
Foreign substrates pre-treatment using polymer composites in plasma-enhanced CVD growth of diamond fibers and layers
Potocký, Štěpán ; Babchenko, Oleg ; Ižák, Tibor ; Varga, Marián ; Kromka, Alexander ; Rezek, Bohuslav ; Tesárek, P.
Nanocrystalline diamond wires and layers were grown by microwave plasma CVD technique on Si substrates. The substrates were pretreated by non-woven composite nanofiber textile composed by poly(vinyl alcohol) matrix and ultra-dispersed diamond (UDD) nanoparticles prepared by needleless electrospinning method. High concentration of UDD in the PVA fibers lead to formation of diamond wires due to a combined effect of UDD particles used as seeding and high pressure difference across the fibers interface. A preferable growth of diamond layers was observed on areas with a low porosity volume of nanofiber textile. The influence of spundond structure on the growth of diamond decreased with lowering of UDD concentra-tion in the primary polymer matrix.

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