Single-walled carbon nanotube structure and radiation defects under the high energy electron beam

The effect of electron irradiation up to fluence of 1.54×1017 electron/cm2 on the structural parameters, sizes of nanocrystallites, microstrains, and Raman spectra of a single-walled carbon nanotube (SWCNT) was studied. Electron irradiation leads to an increase in the lattice parameters in the a and b directions from 4.7623 Å to 4.9378 Å and a decrease along the c axis from 3.9491 Å to 3.9469 Å. Electron irradiation stimulates the growth of the nanocrystallite size from 4.06 nm to 5.03 nm, leads to a shift of the Raman spectra towards higher frequencies, and indicates the appearance of a spectrum at 805 cm–1, which is caused by the formation of defects in a SWCNT.

Surface structure, nanocrystallite and defects in (ZrTi)CN nanocomposite irradiated by electron beam

Effect of 2 MeV electron beam at the current density 0.09 nA/cm2 on surface structure, nanocrystallite size of (ZrTi)CN nanocomposite coating on steel was investigated at Scanning Electron and Atomic Force microscopes, and also X-ray diffractometer. Using the Rietveld method, two structure phases were indentified in the pristine samples: (ZrTi)(CN)-cubic (space group Fm-3m) and TiC — trigonal (sp.gr.R-3m). Electron beam irradiation to the fluency of [Formula: see text] electron/cm2 resulted in the phase transition of TiC from trigonal (sp.gr.R-3m) to cubic structure (sp.gr.Fm-3m). Besides, nanocrystallite size and shape have changed after the fluency [Formula: see text] electron/cm2. The lattice parameters have increased up to [Formula: see text] electron/cm2 fluence and the nanorcrystallite size of nanocomposite was enlarged 26%, which was attributed to generation of defects.

The Synthesis of Hydroxyapatite Powder Using Shaker Mill Technique

Hydroxyapatite is a material that has the same structure and composition as the main minerals of human teeth and bones. This study's purpose was hydroxyapatite synthesis and determining the effect of variations in the ball sizes, the ratio of a mass of precursors to balls size, milling time, and ball size ratio of crystals and particles, surface area and morphology of hydroxyapatite produced by the mechanochemical method. Two different ball sizes (3mm and 6mm) and three different powder to ball ratio of 1:1.44; 1:2.88; and 1:4.32 were milled for 6 hours. Furthermore, the ball size ratio between the small ball (3 mm) and large ball (6 mm) was 1:1, 1:3, and 3:1 were milled for 2, 4, and 6 hours. The synthesized powder was analyzed by X-ray diffraction, Particle Size Analysis, Brunauer-Emmet-Teller analysis, and Scanning Electron Microscopy to confirm hydroxyapatite structure formation with nanocrystallite size and morphology in all variables. The crystallite size increased as the powder to ball ratio increased. The surface area at powder to ball ratio of 1:2.88 and ball size of 3 mm was 19.51 m2/g, while at ball size ratio of 1:1, it was 18.82 m2/g. The morphology of hydroxyapatite was uniform to granular with mol ratio Ca/P 1.81 for powder to ball ratio and ball size variation.

Green synthesis of silver nanoparticles from Valeriana jatamansi shoots extract and its antimicrobial activity

The present study explores the potential of Valeriana jatamansi shoot extract for Ag-metal bio-reduction and its antimicrobial activity. Among the different ratios of AgNO3 and extract tested, 1:5 (1 mL AgNO3 and 5 mL extract) gave maximum SPR peak at 411.0 nm during UV-Vis spectrophotometric analysis, indicating the synthesis of maximum amount of AgNPs in solution. XRD analysis reported the crystalline nature of AgNPs with 13.32 nm nanocrystallite size. FTIR studies suggested the involvement of carboxylic acid (–[C–O–O–H]) and methane (–CH–) functional groups of different compounds in AgNPs reduction and fabrication. Average size of synthesized uniform shaped nanospheres was 32 nm by SEM image analysis. The produced AgNPs (1.5 mg/disc) showed growth inhibition of 71.46, 65.97, 61.5, 55.32, and 54.83% against Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Xanthomonas campestris, and Staphylococcus aureus. While the least growth inhibition of 48.55% was recorded for Klebsiella pneumonia, suggesting it as the least-susceptible microbe among all the tested microbial species. P. aeruginosa was found to be most sensitive of all tested microbes, while E. coli, C. albicans, and X. campestris reported moderate susceptibility to AgNPs.

Properties of nanocrystalline silicon probed by optomechanics

Nanocrystalline materials exhibit properties that can differ substantially from those of their single crystal counterparts. As such, they provide ways to enhance and optimize their functionality for devices and applications. Here, we report on the optical, mechanical and thermal properties of nanocrystalline silicon probed by means of optomechanical nanobeams to extract information of the dynamics of optical absorption, mechanical losses, heat generation and dissipation. The optomechanical nanobeams are fabricated using nanocrystalline films prepared by annealing amorphous silicon layers at different temperatures. The resulting crystallite sizes and the stress in the films can be controlled by the annealing temperature and time and, consequently, the properties of the films can be tuned relatively freely, as demonstrated here by means of electron microscopy and Raman scattering. We show that the nanocrystallite size and the volume fraction of the grain boundaries play a key role in the dissipation rates through nonlinear optical and thermal processes. Promising optical (13,000) and mechanical (1700) quality factors were found in the optomechanical cavity realized in the nanocrystalline Si resulting from annealing at 950°C. The enhanced absorption and recombination rates via the intragap states and the reduced thermal conductivity boost the potential to exploit these nonlinear effects in applications including Nanoelectromechanical systems (NEMS), phonon lasing and chaos-based devices.

The effect of electron beam on nanocrystallites size, strain and structural parameters of the silicon carbide nanopowder

The effect of high-energy electron beam on the silicon carbide nanopowder’s structural parameters, strain and powder size was studied. The sample was irradiated with [Formula: see text]2-MeV electron beam energy under different fluencies such as 1.13 ⋅ 10[Formula: see text], 1.89 ⋅ 10[Formula: see text], 2.79 ⋅ 10[Formula: see text] and 3.69 ⋅ 10[Formula: see text] cm[Formula: see text] at the linear electronic accelerator. Initial and irradiated samples at various doses have been analyzed in the XRD. The nanostructural effects within FullProf are treated using the pseudo-Voigt profile function. The dependences of maximum strain and nanocrystallite size on irradiation dose were obtained and analyzed.

Interplay Between Silicon Nanocrystal Size and Local Environment Within Porous Silicon on the Analyte-Dependent Photoluminescence Response

Porous silicon (pSi) exhibits strong photoluminescence (PL) and its PL is often exploited for chemical sensor development. However, the sensor response is not uniform across a pSi specimen. We use co-localized confocal PL and Raman scattering mapping to establish a relationship between the analyte-induced PL response and the silicon nanocrystallite size, size distribution, and amorphous silicon (aSi) contribution across a pSi specimen. Using toluene as a model analyte, high analyte-induced PL response is associated with areas within the specimen that have (i) low aSi content, (ii) silicon nanocrystallites having diameters between 2 and 5 nm, and (iii) silicon nanocrystallites that exhibit a narrow size distributions (≤1% relative standard deviation).