The role of hydrogen in a-C:H films deposited from hexane or acetylene

Present work provides results for amorphous hydrogenated carbon (a-C:H) films deposited by direct ion beam deposition method. Hexane (C6H14) or acetylene (C2H2) precursors and their mixture with hydrogen (H2) were used. The films were characterized by Raman spectroscopy (RS), ellipsometry, IR transmittance and electrical resistance measurements. RS indicated increase of sp3/sp2 bonding ratio and disorder in graphite clusters with increasing hydrogen content (from O to 50% for acetylene precursor) in deposition gas mixture. The opposite trend was observed when the hydrogen concentration exceeds 50% (for acetylene) or additional hydrogen was used (for hexane). The data of electrical resistance measurements supported the correlations defined by RS

Laser-Induced Transformation of Different Types of A-C:H Thin Films

Amorphous carbon films are perspective materials for many biological applications. Laser treatment is very useful technique for precise pattering of diamond-like carbon (DLC) films and the pulsed laser processing has some advantages over mechanical and chemical processing. Additionally, laser influence should depend on the properties of DLC films. The different types of a-C:H films were deposited on Si by direct ion beam using different mixtures of acetylene and hydrogen, liexane and hydrogen. In order to reduce an influence of atmosphere during the laser irradiation, the a-C:H films were coated by silica. After that the samples were irradiated in a scanning mode of a YAG:Nd laser (532nm, 10ns). An increasing intensity of the laser irradiation reduces film thickness, develops a grain structure, increases film density and roughness, and stimulates diffusion of Si atoms into a-C:H film and H atoms into SiOx layer and Si wafer. The films were destroyed at high laser intensities (-10 MW/cm2 or ~7 MW/cm2 for films with high hydrogen (>40at%) concentration). Raman spectra of laser-irradiated samples depend on the initial properties of the a-C:H films. The samples with relatively low H-content (-35%) and high percentage (-70%) of sp3-bonds (DLC films) were not significantly changed using low and moderate laser intensity (Fig.l). At higher intensify -5 MW/cm2, the D-peak decreased and shifted towards lower frequency whereas the G-peak parameters remained almost unchanged. Additionally, infrared spectroscopy indicated an increase CH2 in sp3 hybridization of C-sp3 and C-sp2 modes simultaneously. Contrary, Raman spectra of laser-irradiated (using 4-7 MW/cm2) a-C:H films with initially dominating sp2-bonds (GLC films) were typical for glassy carbon. For the films with high hydrogen (PLC) content, the transformation to glassy-carbon occurs at yet lower laser intensity. Summarizing, the a-C:H films containing higher hydrogen content (PLC films) were more sensitive to laser irradiation. The laser irradiation leads to graphitization of a-C:H films and formation of glassy carbon. As results of laser irradiation, SiC and diamond-like nanocrystals were also formed

The role of hydrogen in a-C:H films deposited from hexane or acetylene

Present work provides results for amorphous hydrogenated carbon (a-C:H) films deposited by direct ion beam deposition method. Hexane (C6H14) or acetylene (C2H2) precursors and their mixture with hydrogen (H2) were used. The films were characterized by Raman spectroscopy (RS), ellipsometry, IR transmittance and electrical resistance measurements. RS indicated increase of sp3/sp2 bonding ratio and disorder in graphite clusters with increasing hydrogen content (from O to 50% for acetylene precursor) in deposition gas mixture. The opposite trend was observed when the hydrogen concentration exceeds 50% (for acetylene) or additional hydrogen was used (for hexane). The data of electrical resistance measurements supported the correlations defined by RS

The fire resistance assessment of protected steel elements using various fire protection materials and different heating conditions /

The problem of the resistance to fire of metal constructions is examined and different fire resistance furnaces are overviewed. Testing conditions and testing methods by which the elements were tested resistance to fire were performed and provided. The article describes the behaviour of different fireproof materials during the tests and it analyzes the influence of different heating conditions to element’s fire resistance class. The tests’ results, findings, advices are also included. Santrauka Darbe nagrinėjama metalinių konstrukcijų atsparumo ugniai problema. Apžvelgta skirtinga atsparumo ugniai nustatymo įranga. Pateikiamos sąlygos, kuriomis buvo atliekami atsparumo ugniai bandymai su skirtingais elementais. Nagrinėjama skirtingų priešgaisrinių apsaugos medžiagų reakcija bandymo metu ir analizuojama, kaip skirtingos klimatobei aplinkos sąlygos gali lemti elementų atsparumo ugniai klasę. Pateikiami atliktų bandymų rezultatai, atlikta išsami rezultatų analizė, pateiktos išvados. Raktiniai žodžiai: atsparumas ugniai, plieninė konstrukcija, temperatūros ir laiko kreivė, apsauginė medžiag

Comparison of different extraction techniques for isolation of antioxidants from sweet grass (Hierochloe odorata)

Strong antioxidants, 5,8-dihydroxycoumarin and 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone were extracted from sweet grass (Hierochloe odorata L.) by using Soxhlet (SE), microwave-assisted (MAE) and supercritical fluid carbon dioxide (SFE) extractions at different extraction schemes and parameters. One-step MAE gave the most concentrated extract with 8.15% of 5,8-dihydroxycoumarin (extract yield 0.42%). Comparable results were obtained by one-step SFE and Soxhlet extraction. A two-step extraction was applied in order to increase the concentration of active compounds. Taking into account antioxidant recovery and concentration as well the extraction time and environmental aspects, two-step SFE was considered as a preferable method. The obtained crude extract contained 20.31% of 5,8-dihydroxycoumarin and 2.18% of 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone. The extraction yields were 0.46 and 0.06%, respectively. First-step of SFE extraction was performed from dried herb at 35 MPa and 40degreesC with 20% of ethanol as a modifier; the second extraction step was performed from the crude extract at 25 MPa and 40degreesC