Electrospraying and electrospinning processes were employed for the production of nanocomposite material of polymer nanofibers blended with nanoparticles. The diameter of polymer nanofibers made of ...PVC, PSU or nylon was smaller than 500
nm. Metal oxide nanoparticles of TiO
2, MgO, and Al
2O
3 of the size 20–100
nm suspended in methanol were deposited on the polymer nanofibers. Three configurations of electrospray/electrospun nozzles used for the nanocomposite production were tested: 1. simultaneous electrospraying during the electrospinning process, 2. electrospraying onto the same rotating drum after the electrospinning is completed, and 3. electrospraying onto the electrospun mat removed from the drum and placed onto a heated table.
Positron annihilation techniques, being non-destructive, allowing depth profiling down to a few micrometers and detecting open-volume defects (vacancies, dislocations etc.) at single ppm ...concentrations constitute a valuable and complementary method, compared to other solid-state-physics studies. We give examples of investigation in the field of semiconductors with different techniques, both with and without use of positron low-energy beams. The Doppler broadening of the 511keV annihilation line method and the slow positron beam were used to study helium-implanted silicon and the surface reduction processes in semiconducting glasses. The positron lifetime technique and coincidence spectra of the Doppler broadening were used for systematic studies of metals and semiconductors. Doppler-coincidence method was then used to identify the kinetics of oxygen precipitates in Czochralski-grown silicon.
We compare the recent values of positron total cross sections in benzene, cyclohexane and aniline by Zecca et al. with our previous measurements Karwasz et al. Acta Phys. Pol. A, 107 (2005) 666 on ...the same apparatus. An apparent discrepancy disappears if Zecca's data are shifted by +0.2 eV; then their data can be approximated by the modified effective range theory, as well. This observation induced us to compare recent Trento data with other experiments and theories for polar targets, H2O and HCOOH. The evidence points out towards the need of a careful energy calibration in positron experiments.
Positron scattering in helium: Virtual-positronium resonances Karwasz, G.P.; Pliszka, D.; Zecca, A. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
November 2005, 2005-11-00, Letnik:
240, Številka:
3
Journal Article
Recenzirano
Total cross sections for positron scattering in helium and argon were measured at 0.5–25eV with a new spectrometer from Trento University, with a good angular resolution (3.1×10−4sr). Data in argon ...fall in-between earlier measurements; those for He agree well with the previous above the positronium formation thresholds but are up to 50% higher at low energies. Data for He show four resonant-like structures, one at the positronium threshold formation (17.8eV) predicted by Van Reeth and Humberston J. Phys. B 32 (1999) L103, another at about 6.8eV and two very prominent centred at 1.6eV and 2.2eV. Following Gribakin and King J. Phys. B 27 (1994) 2639 the two latter could be signs of virtual-positronium formation in helium.
In this work, we study the modification of hydrogenated diamond films deposited on silicon resulting from its exposure to DBr followed by an annealing above 600
K, using high resolution electron ...energy loss spectroscopy (HREELS). This procedure results in silicon carbide SiC formation within the diamond film, as evidenced by the observation of a loss peak at 117
meV and its first harmonic at 233
meV in HREEL spectra. This diamond surface modification is interpreted as resulting from the reaction of products of the silicon support thermally activated etching with hydrogenated diamond.
One-dimensional (1D) metal oxides, typically nanowires and nanorods, have unique electronic and optical properties due to quantum phenomena that find applications in modern energy and electronic ...devices. We present here the electrospinning method that produces the aligned TiO
2
nanofibres directly on the fluorine-doped tin oxide (FTO) substrates mounted rotating disc collector. The aligned TiO
2
ceramic nanofibres mat of 6
μ
m thickness is achieved in 4 h using a nonconductive enclosed-air-shield with air-hood design over the FTO mounted rotating disc collector. The aligned TiO
2
nanofibers are found to retain its integrity and binding on FTO surface even after sintering at 500°C. SIMON 8 modeling package is used to determine the behaviour of the charged polymer/TiO
2
jet when single and double needles are used for electrospinning process. The simulation study reveals that the repulsive force of the charged fibers from the double needle exerts stronger electric field distribution along the flow of stream that results in the reduction of the fibers diameter, which is about 28 nm than that of using single-needle system.
The time required for osseointegration with a metal implant having a smooth surface ranges from three to six months. We hypothesized that biomimetic coating surfaces with poly(lactic-co-glycolic ...acid) (PLGA)/collagen fibers and nano-hydroxyapatite (n-HA) on the implant would enhance the adhesion of mesenchymal stem cells. Therefore, this surface modification of dental and bone implants might enhance the process of osseointegration. In this study, we coated PLGA or PLGA/collagen (50:50 w/w ratio) fiber on Ti disks by modified electrospinning for 5 s to 2 min; after that, we further deposited n-HA on the fibers. PLGA fibers of fiber diameter 0.957 ± 0.357 µm had a contact angle of 9.9 ± 0.3° and PLGA/collagen fibers of fiber diameter 0.378 ± 0.068 µm had a contact angle of 0°. Upon n-HA incorporation, all the fibers had a contact angle of 0° owing to the hydrophilic nature of n-HA biomolecule. The cell attachment efficiency was tested on all the scaffolds for different intervals of time (10, 20, 30 and 60 min). The alkaline phosphatase activity, cell proliferation and mineralization were analyzed on all the implant surfaces on days 7, 14 and 21. Results of the cell adhesion study indicated that the cell adhesion was maximum on the implant surface coated with PLGA/collagen fibers deposited with n-HA compared to the other scaffolds. Within a short span of 60 min, 75% of the cells adhered onto the mineralized PLGA/collagen fibers. Similarly by day 21, the rate of cell proliferation was significantly higher (p ⩽ 0.05) on the mineralized PLGA/collagen fibers owing to enhanced cell adhesion on these fibers. This enhanced initial cell adhesion favored higher cell proliferation, differentiation and mineralization on the implant surface coated with mineralized PLGA/collagen fibers.
The paper presents investigations of a method of the production of non-woven polymer fabrics with incorporated metal oxide nanoparticles based on electrospinning and electrospraying. Two main ...configurations of electrospraying/electrospinning systems have been tested: two-step process of electrospinning of polymer solution followed by electrospraying of nanoparticle suspension, and simultaneous electrospinning of polymer solution and electrospraying of nanoparticle suspension. By this method TiO2, MgO, or Al2O3 nanoparticles of the size from 20 to 100 nm were deposited onto electrospun PVC nanofibers.
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