Boron-containing films are promising materials for improving the hardness, wear-resistance and durability of mechanical parts used in industry. We describe a novel approach for deposition of such ...coatings – by using electron-beam evaporation of boron-containing target material (pure boron or boron nitride) in inert (helium) or chemically-active (oxygen, nitrogen, residual atmosphere) gases at medium vacuum. Boron-containing films deposited on titanium substrates were characterized using a nanohardness tester and a non-contact 3D profilometer. Elemental composition of the coatings was studied using raster electron microscope equipped with a device for EDX analysis. All boron-containing coatings provided significant improvement (by a factor of 4–16) in the microhardness of the substrate surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Using sequential electron-beam evaporation of high-temperature dielectric (alumina ceramic) and magnetic (iron) targets in various gas atmospheres (helium, air, and oxygen) in medium vacuum (5–8 Pa), ...magneto-dielectric coatings with thickness of around 2 μm were deposited from a multicomponent beam plasma at a deposition rate of 0.2–0.3 μm/min. The coating magnetic properties were explored by the ferromagnetic resonance technique, revealing that their effective magnetization depends on the type of operating gas and varied from 4.2 to 6.8 kGs (for deposition in helium) to 0.3 kGs (in oxygen), which is characteristic of oxide ferromagnetic materials and is considerably lower than the corresponding value (∼22 kGs) for thin iron films formed by vacuum arc deposition in high vacuum. X-ray structural analysis of coatings deposited in medium vacuum in helium showed that the magnetic layer has a magnetite (Fe3O4) structure. The alumina ceramic layer provides the dielectric properties of the magneto-dielectric coating; a relative dielectric constant of 6.0 and a conductivity of 8.4 mS/m were achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We describe a method that uses a condensation probe for measuring the degree of ionization of the vapor of electron-beam evaporated materials in the forevacuum pressure range. The probe design and ...its working principles are described. The degree of ionization of solid targets evaporated by an electron beam is shown to exceed 65%.
•Magnetic condensation probe has been introduced to analyze complex beam plasma.•Degree of ionization of electron-beam-evaporated targets vapors has been measured.•Beam plasma formed from Pb, Zn, Cu and Al2O3 targets has more than 65% of ions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract We have documented that epidermal growth factor receptor protein tyrosine kinase (EGFR-PTK) signaling negatively affects intracellular trafficking and transduction efficiency of recombinant ...adeno-associated virus 2 (AAV2) vectors. Specifically, inhibition of EGFR-PTK signaling leads to decreased ubiquitination of AAV2 capsid proteins, which in turn, facilitates viral nuclear transport by limiting proteasome-mediated degradation of AAV2 vectors. In the present studies, we observed that AAV capsids can indeed be phosphorylated at tyrosine residues by EGFR-PTK in in vitro phosphorylation assays and that phosphorylated AAV capsids retain their structural integrity. However, although phosphorylated AAV vectors enter cells as efficiently as their unphosphorylated counterparts, their transduction efficiency is significantly reduced. This reduction is not due to impaired viral second-strand DNA synthesis since transduction efficiency of both single-stranded AAV (ssAAV) and self-complementary AAV (scAAV) vectors is decreased by ∼ 68% and ∼ 74%, respectively. We also observed that intracellular trafficking of tyrosine-phosphorylated AAV vectors from cytoplasm to nucleus is significantly decreased, which results from ubiquitination of AAV capsids followed by proteasome-mediated degradation, although downstream consequences of capsid ubiquitination may also be affected by tyrosine-phosphorylation. These studies provide new insights into the role of tyrosine-phosphorylation of AAV capsids in various steps in the virus life cycle, which has implications in the optimal use of recombinant AAV vectors in human gene therapy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Efficient and ambient synthesis of aromatic polyimides (PIs) from readily available starting materials remains a very challenging task in polymer chemistry. Herein, we report for the first time a ...robust, one-step synthesis of organo-soluble functional aromatic PIs. Room temperature, metal-free, superacid (TFSA)-catalyzed step polymerization of aryl-terminated diimides with carbonyl compounds (2,2,2-trifluoroacetophenone and indoline-2,3-dione (isatin)) afforded 14 high-molecular-weight, linear, film-forming PIs. The effect of structural variation of the dianhydride segment, the amount of catalyst, and monomer concentration were studied. The PIs were obtained in quantitative yields, with high thermal stabilities up to 525 °C and 55% weight residue at 800 °C under an inert atmosphere and number-average molecular weights (M n) in a range of 51–195 kg mol–1. Well-controlled proportions of the functional phenolic hydroxyl groups (at the ortho-position to the imide ring) and diaryloxindole reactive sites were introduced into macromolecules during polyimide syntheses, while pendent allyl and propargyl groups were formed by the chemical postpolymerization reactions. Subsequent modifications of the reactive sites using click-chemistry can afford multifunctional polymers with tunable properties. The thermal postpolymerization modification of polyhydroxyimides converts them into polybenzoxazoles (so-called thermally rearranged polymers).
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IJS, KILJ, NUK, PNG, UL, UM
We have explored the formation of alumina coatings by electron beam evaporation of bulk alumina ceramic using a forevacuum-pressure plasma-cathode electron beam source at a pressure of 60 mTorr of ...air. The alumina e-beam target material is evaporated at a rate up to 4.2 g/h, and the coating deposition rate is up to 18 μm/h. The evaporated ceramic is partially ionized by the energetic electron beam, and we have measured the plasma composition as a function of beam power. The deposited alumina coatings were characterized by scanning electron microscopy and energy-dispersive x-ray spectroscopy and found to be uniform and pore-free with a composition that is over 99% aluminum and oxygen, with less than 1% impurities including carbon, silicon and calcium.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The work is concerned with the efficiency of inclusion of the additional layer of por-Si applied as a buffer into the growth technology of AlxGa1-xN/AlN/Si as well as its influence on the ...morphological parameters and composition of surface of the grown heterostructures. In the course of the study, it was found that the heterostructure grown using a nanoporous por-Si buffer layer on a Si(111) n-type monocrystalline silicon wafer has a more homogeneous structure of the epitaxial layer and its surface morphology.
Abstract
We have investigated the formation of electron beam-generated (EBG) plasma near a dielectric (ceramic) target and an insulated metal target, and the compensation of the negative charge ...accumulated on the insulated metal target when the targets are irradiated by an intense pulsed electron beam in the forevacuum pressure range (4–15 Pa). It is shown that the density of the EBG plasma near the irradiated ceramic target (or the irradiated insulated metal target) is greater than the plasma density for a beam propagating freely in a vacuum chamber (or for the grounded metal target). The EBG plasma near the target is formed with a certain delay with respect to the electron beam current pulse, because of which the negative potential of the insulated target is also compensated by a delay. The delay time in the formation of the EBG plasma and in the compensation of the target negative potential decreases with increasing gas pressure. Expressions have been proposed for estimating this delay time.
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