Phase Competition Induced Bio-Electrochemical Resistance and Bio-Compatibility Effect in Nanocrystalline Zr x -Cu100-x Thin Films.

PubMed

Badhirappan, Geetha Priyadarshini; Nallasivam, Vignesh; Varadarajan, Madhuri; Leobeemrao, Vasantha Priya; Bose, Sivakumar; Venugopal, Elakkiya; Rajendran, Selvakumar; Angleo, Peter Chrysologue

2018-07-01

Nano-crystalline Zrx-Cu100-x (x = 20-100 at.%) thin films with thickness ranging from 50 to 185 nm were deposited by magnetron co-sputtering with individual Zr and Cu targets. The as-sputtered thin films were characterized by Field Emission Scanning Electron Microscope (FE-SEM), Atomic Force Microscopy (AFM) and Glancing Incidence X-ray Diffraction (GIXRD) for structural and morphological properties. The crystallite size was found to decrease from 57 nm to 37 nm upon increasing the Zr content from 20 to 30 at.% with slight increase in the lattice strain from 0.17 to 0.33%. Further, increase in Zr content to 40 at.% leads to increase in the crystallite size to 57 nm due to stabilization of C10Zr7 phase along with the presence of nanocrystalline Cu-Zr phase. A bimodal distribution of grain size was observed from FE-SEM micrograph was attributed to the highest surface roughness in Zr30Cu70 thin films comprised of Cu10Zr7, Cu9Zr2, Cu-Zr intermetallic phases. In-vitro electrochemical behaviors of nano-crystalline Zrx-Cu100-x thin films in simulated body fluid (SBF) were investigated using potentiodynamic polarization studies. Electrochemical impedance spectroscopy (EIS) data fitting by equivalent electrical circuit fit model suggests that inner bulk layer contributes to high bio-corrosion resistance in Zrx-Cu100-x thin films with increase in Zr content. The results of cyto-compatibility assay suggested that Zr-Cu thin film did not introduce cytotoxicity to osteoblast cells, indicating its suitability as a bio-coating for minimally invasive medical devices.

Grain Growth in Nanocrystalline Mg-Al Thin Films

DOE PAGES

Kruska, Karen; Rohatgi, Aashish; Vemuri, Rama S.; ...

2017-10-05

We report that an improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing ~10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull.more » The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. In conclusion, the low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.« less

Grain Growth in Nanocrystalline Mg-Al Thin Films

NASA Astrophysics Data System (ADS)

Kruska, Karen; Rohatgi, Aashish; Vemuri, Rama S.; Kovarik, Libor; Moser, Trevor H.; Evans, James E.; Browning, Nigel D.

2017-12-01

An improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing 10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.

Nanocrystalline SnO2 formation by oxygen ion implantation in tin thin films

NASA Astrophysics Data System (ADS)

Kondkar, Vidya; Rukade, Deepti; Kanjilal, Dinakar; Bhattacharyya, Varsha

2018-03-01

Metallic tin thin films of thickness 100 nm are deposited on fused silica substrates by thermal evaporation technique. These films are implanted with 45 keV oxygen ions at fluences ranging from 5 × 1015 to 5 × 1016 ions cm-2. The energy of the oxygen ions is calculated using SRIM in order to form embedded phases at the film-substrate interface. Post-implantation, films are annealed using a tube furnace for nanocrystalline tin oxide formation. These films are characterized using x-ray diffraction, Raman spectroscopy, UV-vis spectroscopy and photoluminescence spectroscopy. XRD and Raman spectroscopy studies reveal the formation of single rutile phase of SnO2. The size of the nanocrystallites formed decreases with an increase in the ion fluence. The nanocrystalline SnO2 formation is also confirmed by UV-vis and photoluminescence spectroscopy.

Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.

PubMed

Chaisitsak, Sutichai

2011-01-01

This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors

PubMed Central

Chaisitsak, Sutichai

2011-01-01

This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

NASA Astrophysics Data System (ADS)

Pedersen, Joachim D.; Esposito, Heather J.; Teh, Kwok Siong

2011-10-01

We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.

Microstructure factor and mechanical and electronic properties of hydrogenated amorphous and nanocrystalline silicon thin-films for microelectromechanical systems applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mouro, J.; Gualdino, A.; Chu, V.

2013-11-14

Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three differentmore » types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.« less

Effect of aging heat time and annealing temperature on the properties of nanocrystalline tin dioxide thin films

NASA Astrophysics Data System (ADS)

Kadhim, Imad H.; Abu Hassan, H.

2017-04-01

Nanocrystalline tin dioxide (SnO2) thin films have been successfully prepared by sol-gel spin-coating technique on p-type Si (100) substrates. A stable solution was prepared by mixing tin(II) chloride dihydrate, pure ethanol, and glycerin. Temperature affects the properties of SnO2 thin films, particularly the crystallite size where the crystallization of SnO2 with tetragonal rutile structure is achieved when thin films that prepared under different aging heat times are annealed at 400∘C. By increasing aging heat time in the presence of annealing temperatures the FESEM images indicated that the thickness of the fabricated film was directly proportional to solution viscosity, increasing from approximately 380 nm to 744 nm, as well as the crystallization of the thin films improved and reduced defects.

Depth profiling of nitrogen within 15N-incorporated nano-crystalline diamond thin films

NASA Astrophysics Data System (ADS)

Garratt, E.; AlFaify, S.; Cassidy, D. P.; Dissanayake, A.; Mancini, D. C.; Ghantasala, M. K.; Kayani, A.

2013-09-01

Nano-Crystalline Diamond (NCD) thin films are a topic of recent interest due to their excellent mechanical and electrical properties. The inclusion of nitrogen is a specific interest as its presence within NCD modifies its conductive properties. The methodology adopted for the characterization of nitrogen incorporated NCD films grown on a chromium underlayer determined a correlation between the chromium and nitrogen concentrations as well as a variation in the concentration profile of elements. Additionally, the concentration of nitrogen was found to be more than three times greater for these films versus those grown on a silicon substrate.

Structural and magnetic properties of nanocrystalline NiFe2O4 thin film prepared by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Chavan, Apparao R.; Chilwar, R. R.; Shisode, M. V.; Hivrekar, Mahesh M.; Mande, V. K.; Jadhav, K. M.

2018-05-01

The nanocrystalline NiFe2O4 thin film has been prepared using a spray pyrolysis technique on glass substrate. The prepared thin film was characterized by using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and Field Emission-Scanning Electron Microscopy (FE-SEM) characterization techniques for the structural and microstructural analysis. The magnetic property was measured using vibrating sample magnetometer (VSM) at room temperature. X-ray diffraction studies show the formation of single phase spinel structure of the thin film. The octahedral and tetrahedral vibration in the sample was studied by Fourier transform infrared (FT-IR) spectra. Magnetic hysteresis loop was recorded for thin film at room temperature. At 15 kOe, saturation magnetization (Ms) was found to increase while coercivity (Hc) decreases with thickness of the NiFe2O4 thin film.

Size-controlled synthesis of nanocrystalline CdSe thin films by inert gas condensation

NASA Astrophysics Data System (ADS)

Sharma, Jeewan; Singh, Randhir; Kumar, Akshay; Singh, Tejbir; Agrawal, Paras; Thakur, Anup

2018-02-01

Size, shape and structure are considered to have significant influence on various properties of semiconducting nanomaterials. Different properties of these materials can be tailored by controlling the size. Size-controlled CdSe crystallites ranging from ˜ 04 to 95 nm were deposited by inert gas-condensation technique (IGC). In IGC method, by controlling the inert gas pressure in the condensation chamber and the substrate temperature or both, it was possible to produce nanoparticles with desired size. Structure and crystallite size of CdSe thin films were determined from Hall-Williamson method using X-ray diffraction data. The composition of CdSe samples was estimated by X-ray microanalysis. It was confirmed that CdSe thin film with different nanometer range crystallite sizes were synthesized with this technique, depending upon the synthesis conditions. The phase of deposited CdSe thin films also depend upon deposition conditions and cubic to hexagonal phase transition was observed with increase in substrate temperature. The effect of crystallite size on optical and electrical properties of these films was also studied. The crystallite size affects the optical band gap, electrical conductivity and mobility activation of nanocrystalline CdSe thin films. Mobility activation study suggested that there is a quasi-continuous linear distribution of three different trap levels below the conduction band.

Evidence of extended cation solubility in atomic layer deposited nanocrystalline BaTiO3 thin films and its strong impact on the electrical properties.

PubMed

Falmbigl, Matthias; Karateev, Igor A; Golovina, Iryna S; Plokhikh, Aleksandr V; Parker, Thomas C; Vasiliev, Alexander L; Spanier, Jonathan E

2018-06-22

Thin films of ≈50 nm thickness with Ba/Ti-ratios ranging from 0.8 to 1.06 were prepared by depositing alternating layers of Ba(OH)2 and TiO2. Annealing at 750 °C promoted the solid-solid transformation into polycrystalline BaTiO3 films containing a mixture of the perovskite and the hexagonal polymorphs with average crystallite sizes smaller than 14 nm and without impurity phases. This, together with an increase of the cubic lattice parameters for Ba-rich films, suggests an extended metastable solubility range for the perovskite-phase in these nanocrystalline thin films on both sides of the stoichiometric composition. Mapping of the cation distribution utilizing energy-filtered transmission electron microscopy corroborates defect accommodation within the BaTiO3 grains. While the cation off-stoichiometry in thermodynamic equilibrium is negligible for BaTiO3, the metastable extended solubility range in the thin films can be directly correlated to the low annealing temperature and nanocrystalline nature. The leakage current behavior can be explained by the formation of Schottky defects for nonstoichiometric films, and the cation ratio has a distinct impact on the dielectric properties: while excess-BaO has a marginal detrimental effect on the permittivity, the dielectric constant declines rapidly by more than 50% towards the Ti-rich side. The present findings highlight the importance of compositional control for the synthesis of nanocrystalline BaTiO3 thin films, in particular for low annealing and/or deposition temperatures. Our synthesis approach using alternating layers of Ba(OH)2 and TiO2 provides a route to precisely control the cation stoichiometry.

Synthesis and properties of nanocrystalline copper indium oxide thin films deposited by Rf magnetron sputtering.

PubMed

Singh, Mandeep; Singh, V N; Mehta, B R

2008-08-01

Nanocrystalline copper indium oxide (CuInO2) thin films with particle size ranging from 25 nm to 71 nm have been synthesized from a composite target using reactive Rf magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) combined with glancing angle X-ray diffraction (GAXRD) analysis confirmed the presence of delafossite CuInO2 phase in these films. The optical absorption studies show the presence of two direct band gaps at 3.3 and 4.3 eV, respectively. The resistance versus temperature measurements show thermally activated hopping with activation energy of 0.84 eV to be the conduction mechanism.

Effect of film thickness on NO2 gas sensing properties of sprayed orthorhombic nanocrystalline V2O5 thin films

NASA Astrophysics Data System (ADS)

Mane, A. A.; Moholkar, A. V.

2017-09-01

The nanocrystalline V2O5 thin films with different thicknesses have been grown onto the glass substrates using chemical spray pyrolysis (CSP) deposition method. The XRD study shows that the films exhibit an orthorhombic crystal structure. The narrow scan X-ray photoelectron spectrum of V-2p core level doublet gives the binding energy difference of 7.3 eV, indicating that the V5+ oxidation state of vanadium. The FE-SEM micrographs show the formation of nanorods-like morphology. The AFM micrographs show the high surface area to volume ratio of nanocrystalline V2O5 thin films. The optical study gives the band gap energy values of 2.41 eV, 2.44 eV, 2.47 eV and 2.38 eV for V2O5 thin films deposited with the thicknesses of 423 nm, 559 nm, 694 nm and 730 nm, respectively. The V2O5 film of thickness 559 nm shows the NO2 gas response of 41% for 100 ppm concentration at operating temperature of 200 °C with response and recovery times of 20 s and 150 s, respectively. Further, it shows the rapid response and reproducibility towards 10 ppm NO2 gas concentration at 200 °C. Finally, NO2 gas sensing mechanism based on chemisorption process is discussed.

Determination of dispersive optical constants of nanocrystalline CdSe (nc-CdSe) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Kriti; Al-Kabbi, Alaa S.; Saini, G.S.S.

2012-06-15

Highlights: ► nc-CdSe thin films are prepared by thermal vacuum evaporation technique. ► TEM analysis shows NCs are spherical in shape. ► XRD reveals the hexagonal (wurtzite) crystal structure of nc-CdSe thin films. ► The direct optical bandgap of nc-CdSe is 2.25 eV in contrast to bulk (1.7 eV). ► Dispersion of refractive index is discussed in terms of Wemple–DiDomenico single oscillator model. -- Abstract: The nanocrystalline thin films of CdSe are prepared by thermal evaporation technique at room temperature. These thin films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-raymore » diffraction (XRD) and photoluminescence spectroscopy (PL). The transmission spectra are recorded in the transmission range 400–3300 nm for nc-CdSe thin films. Transmittance measurements are used to calculate the refractive index (n) and absorption coefficient (α) using Swanepoel's method. The optical band gap (E{sub g}{sup opt}) has been determined from the absorption coefficient values using Tauc's procedure. The optical constants such as extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants, dielectric loss (tan δ), optical conductivity (σ{sub opt}), Urbach energy (E{sub u}) and steepness parameter (σ) are also calculated for nc-CdSe thin films. The normal dispersion of refractive index is described using Wemple–DiDomenico single-oscillator model. Refractive index dispersion is further analysed to calculate lattice dielectric constant (ε{sub L}).« less

Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size.

PubMed

Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

2018-02-16

The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb 2 Te 3 ) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb 2 Te 3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb 2 Te 3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb 2 Te 3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size

NASA Astrophysics Data System (ADS)

Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

2018-02-01

The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb2Te3) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb2Te3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb2Te3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb2Te3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

Effect of annealing on structure, morphology and optoelectronic properties of nanocrystalline CuO thin films

NASA Astrophysics Data System (ADS)

Jundale, D. M.; Pawar, S. G.; Patil, S. L.; Chougule, M. A.; Godse, P. R.; Patil, V. B.

2011-10-01

The nanocrystalline CuO thin films were prepared on glass substrates by the sol-gel method. The structural, morphological, electrical and optical properties of CuO thin films, submitted to an annealing treatment in the 400-700 °C ranges are studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Four Probe Technique and UV-visible spectroscopic. XRD measurements show that all the films are crystallized in the monoclinic phase and present a random orientation. Four prominent peaks, corresponding to the (110) phase (2θ≈32.70°), (002) phase (2θ≈35.70°), (111) phase (2θ≈38.76°) and (202) phase (2θ≈49.06°) appear on the diffractograms. The crystallite size increases with increasing annealing temperature. These modifications influence the microstructure, electrical and optical properties. The optical band gap energy decreases with increasing annealing temperature. These mean that the optical quality of CuO films is improved by annealing.

Gadolinia doped hafnia (Gd2O3- HfO 2) thermal barrier coatings for gas turbine applications

NASA Astrophysics Data System (ADS)

Gullapalli, Satya Kiran

Thermal efficiency of the gas turbines is influenced by the operating temperature of the hot gas path components. The material used for the hot gas path components can only withstand temperature up to a certain limit. Thermal barrier coatings (TBC) provide the additional thermal protection for these components and help the gas turbine achieve higher firing temperatures. Traditionally available yttria stabilized zirconia (YSZ) TBCs have a limitation up to 1200 C due to their phase transformation. The present work focuses on gadolinia based hafnia (GSH) TBCs to study their potential to replace the YSZ coatings. Different compositions of gadolinia doped hafnia coatings have been deposited using electron beam physical vapor deposition (EB-PVD) technique and characterized using x-ray diffraction (XRD) and scanning electron microscope (SEM). The crystal structure analysis performed using XRD confirmed the stabilization of the high temperature cubic phase of hafnia. Cross sectional analysis confirmed the presence of columnar structure in the coatings which is a signature of the EB-PVD coatings. Mechanical properties of the coatings were investigated using nanoindentation and nano impact testing at both room temperature and high temperature. Indentation tests indicate a reduction in hardness with an increase in temperature and gadolinia content in hafnia. Impact testing reveals the fracture resistance of the coatings as a function of stabilizer content and heat treatment. Thermal measurements and impedance testing was performed on the bulk material to study the effect of gadolinia content. Thermal cycling was performed to study the spallation behavior of the as deposited and aged samples. Finite element models were developed to study the interfacial stress development in the coatings subjected to thermal cycling.

Flexible pressure sensor based on graphene aerogel microstructures functionalized with CdS nanocrystalline thin film

NASA Astrophysics Data System (ADS)

Plesco, Irina; Dragoman, Mircea; Strobel, Julian; Ghimpu, Lidia; Schütt, Fabian; Dinescu, Adrian; Ursaki, Veaceslav; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

2018-05-01

In this paper, we report on functionalization of graphene aerogel with a CdS thin film deposited by magnetron sputtering and on the development of flexible pressure sensors based on ultra-lightweight CdS-aerogel nanocomposite. Analysis by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis disclose the uniform deposition of nanocrystalline CdS films with quasi-stoichiometric composition. The piezoresistive response of the aforementioned nanocomposite in the pressure range from 1 to 5 atm is found to be more than one order of magnitude higher than that inherent to suspended graphene membranes, leading to an average sensitivity as high as 3.2 × 10-4 kPa-1.

Thermal conductivity of self-ion irradiated nanocrystalline zirconium thin films

DOE PAGES

Pulavarthy, Raghu; Wang, Baoming; Hattar, Khalid; ...

2017-07-15

Thermomechanical stability and high thermal conductivity are important for nuclear cladding material performance and reliability, which degrade over time under irradiation. The literature suggests nanocrystalline materials as radiation tolerant, but little or no evidence is present from thermal transport perspective. In this study, we irradiated 10 nm grain size zirconium thin films with 800 keV Zr + beam from a 6 MV HVE Tandem accelerator to achieve various doses of 3 × 10 10 to 3.26 × 10 14 ions/cm 2, corresponding to displacement per atom (dpa) of 2.1 × 10 –4 to 2.28. Transmission electron microscopy showed significant grainmore » growth, texture evolution and oxidation in addition to the creation of displacement defects due to the irradiation. The specimens were co-fabricated with micro-heaters to establish thermal gradients that were mapped using infrared thermometry. An energy balance approach was used to estimate the thermal conductivity of the specimens, as function of irradiation dosage. As a result, up to 32% reduction of thermal conductivity was measured for the sample exposed to a dose of 2.1 dpa (3 × 10 14 ions/cm 2).« less

Thermal conductivity of self-ion irradiated nanocrystalline zirconium thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pulavarthy, Raghu; Wang, Baoming; Hattar, Khalid

Thermomechanical stability and high thermal conductivity are important for nuclear cladding material performance and reliability, which degrade over time under irradiation. The literature suggests nanocrystalline materials as radiation tolerant, but little or no evidence is present from thermal transport perspective. In this study, we irradiated 10 nm grain size zirconium thin films with 800 keV Zr + beam from a 6 MV HVE Tandem accelerator to achieve various doses of 3 × 10 10 to 3.26 × 10 14 ions/cm 2, corresponding to displacement per atom (dpa) of 2.1 × 10 –4 to 2.28. Transmission electron microscopy showed significant grainmore » growth, texture evolution and oxidation in addition to the creation of displacement defects due to the irradiation. The specimens were co-fabricated with micro-heaters to establish thermal gradients that were mapped using infrared thermometry. An energy balance approach was used to estimate the thermal conductivity of the specimens, as function of irradiation dosage. As a result, up to 32% reduction of thermal conductivity was measured for the sample exposed to a dose of 2.1 dpa (3 × 10 14 ions/cm 2).« less

Temperature and field dependent magnetization studies on nano-crystalline ZnFe2O4 thin films

NASA Astrophysics Data System (ADS)

Sahu, B. N.; Suresh, K. G.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

2018-05-01

Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops.

Correlation study of nanocrystalline carbon doped thin films prepared by a thermionic vacuum arc deposition technique

NASA Astrophysics Data System (ADS)

Dinca-Balan, Virginia; Vladoiu, Rodica; Mandes, Aurelia; Prodan, Gabriel

2017-11-01

The synthesis of Ag, Mg and Si nanocrystalline, embedded in a hydrogen-free amorphous carbon (a-C) matrix, deposited by a high vacuum and free buffer gas technique, were investigated. The films with compact structures and extremely smooth surfaces were prepared using the thermionic vacuum arc method in one electron gun configuration, on glass and silicon substrates. The surface morphology and wettability of the obtained multifunctional thin films were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and free surface energy (FSE) by See System. The results from the TEM measurements show how the Ag, Mg and Si interacted with carbon and the influence these materials have on the thin film structure formation and the grain size distribution. SEM correlated with EDX results reveal a very precise comparative study, regarding the quantity of the elements that morphed into carbides nanostructures. Also, the FSE results prove how different materials in combination with carbon can make changes to the surface properties.

Gadolinia depletion analysis by CASMO-4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Y.; Saji, E.; Toba, A.

1993-01-01

CASMO-4 is the most recent version of the lattice physics code CASMO introduced by Studsvik. The principal aspects of the CASMO-4 model that differ from the models in previous CASMO versions are as follows: (1) heterogeneous model for two-dimensional transport theory calculations; and (2) microregion depletion model for burnable absorbers, such as gadolinia. Of these aspects, the first has previously been benchmarked against measured data of critical experiments and Monte Carlo calculations, verifying the high degree of accuracy. To proceed with CASMO-4 benchmarking, it is desirable to benchmark the microregion depletion model, which enables CASMO-4 to calculate gadolinium depletion directlymore » without the need for precalculated MICBURN cross-section data. This paper presents the benchmarking results for the microregion depletion model in CASMO-4 using the measured data of depleted gadolinium rods.« less

Nanocrystalline CuNi alloys: improvement of mechanical properties and thermal stability

NASA Astrophysics Data System (ADS)

Nogues, Josep; Varea, A.; Pellicer, E.; Sivaraman, K. M.; Pane, S.; Nelson, B. J.; Surinach, S.; Baro, M. D.; Sort, J.

2014-03-01

Nanocrystalline metallic films are known to benefit from novel and enhanced physical and chemical properties. In spite of these outstanding properties, nanocrystalline metals typically show relatively poor thermal stability which leads to deterioration of the properties due to grain coarsening. We have studied nanocrystalline Cu1-xNix (0.56 < x < 1) thin films (3 μm-thick) electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates. CuNi thin films exhibit large values of hardness (6.15 < H < 7.21 GPa), which can be tailored by varying the composition. However, pure Ni films (x = 1) suffer deterioration of their mechanical and magnetic properties after annealing during 3 h at relatively low temperatures (TANN > 475 K) due to significant grain growth. Interestingly, alloying Ni with Cu clearly improves the thermal stability of the material because grain coarsening is delayed due to segregation of a Cu-rich phase at grain boundaries, thus preserving both the mechanical and magnetic properties up to higher TANN.

Effect of substrate temperature on implantation doping of Co in CdS nanocrystalline thin films.

PubMed

Chandramohan, S; Kanjilal, A; Sarangi, S N; Majumder, S; Sathyamoorthy, R; Hong, C-H; Som, T

2010-07-01

We demonstrate doping of nanocrystalline CdS thin films with Co ions by ion implantation at an elevated temperature of 573 K. The modifications caused in structural and optical properties of these films are investigated. Co-doping does not lead to amorphization or formation of any secondary phase precipitate for dopant concentrations in the range of 0.34-10.8 at.% used in the present study. However, we observe a systematic reduction in the d-spacing with increasing cobalt concentration. Optical band gap of CdS does not show any obvious change upon Co-doping. In addition, implantation gives rise to grain growth and increase in the surface roughness. The results are discussed in the light of ion-matter interaction in the keV regime.

FAST TRACK COMMUNICATION: Nanocrystalline silicon film growth morphology control through RF waveform tailoring

NASA Astrophysics Data System (ADS)

Johnson, Erik V.; Verbeke, Thomas; Vanel, Jean-Charles; Booth, Jean-Paul

2010-10-01

We demonstrate the application of RF waveform tailoring to generate an electrical asymmetry in a capacitively coupled plasma-enhanced chemical vapour deposition system, and its use to control the growth mode of hydrogenated amorphous and nanocrystalline silicon thin films deposited at low temperature (150 °C). A dramatic shift in the dc bias potential at the powered electrode is observed when simply inverting the voltage waveform from 'peaks' to 'troughs', indicating an asymmetric distribution of the sheath voltage. By enhancing or suppressing the ion bombardment energy at the substrate (situated on the grounded electrode), the growth of thin silicon films can be switched between amorphous and nanocrystalline modes, as observed using in situ spectroscopic ellipsometry. The effect is observed at pressures sufficiently low that the collisional reduction in average ion bombardment energy is not sufficient to allow nanocrystalline growth (<100 mTorr).

Nanocrystalline mesoporous SMO thin films prepared by sol gel process for MEMS-based hydrogen sensor

NASA Astrophysics Data System (ADS)

Gong, Jianwei; Fei, Weifeng; Seal, Sudipta; Chen, Quanfang

2004-01-01

MEMS based SnO2 gas sensor with sol gel synthesized mesoporous nanocrystalline (<10 nm) semiconductor thin (100~150 nm) film has been recently developed. The SnO2 nano film is fabricated with the combination of polymeric sol gel chemistry with block copolymers used for structure directing agents. The novel hydrogen sensor has a fast response time (1s) and quick recovery time (3s), as well as good sensitivity (about 90%), comparing to other hydrogen sensors developed. The improved capabilities are credited to the large surface to volume ratio of gas sensing thin film with nano sized porous surface topology, which can greatly increase the sensitivity even at relatively low working temperature. The gas sensing film is deposited onto a thin dielectric membrane of low thermal conductivity, which provides good thermal isolation between substrate and the gas-sensitive heated area on the membrane. In this way the power consumption can be kept very low. Since the fabrication process is completely compatible with IC industry, it makes mass production possible and greatly reduces the cost. The working temperature of the new sensor can be reduced as low as 100°C. The low working temperature posse advantages such as lower power consumption, lower thermal induced signal shift as well as safe detection in certain environments where temperature is strictly limited.

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

PubMed Central

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-01-01

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

NASA Astrophysics Data System (ADS)

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-07-01

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

Ferroelectric polarization in nanocrystalline hydroxyapatite thin films on silicon.

PubMed

Lang, S B; Tofail, S A M; Kholkin, A L; Wojtaś, M; Gregor, M; Gandhi, A A; Wang, Y; Bauer, S; Krause, M; Plecenik, A

2013-01-01

Hydroxyapatite nanocrystals in natural form are a major component of bone--a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

Layer-by-layer assembled thin films and microcapsules of nanocrystalline cellulose for hydrophobic drug delivery.

PubMed

Mohanta, Vaishakhi; Madras, Giridhar; Patil, Satish

2014-11-26

A layer-by-layer (LbL) approach has been employed for the fabrication of multilayer thin films and microcapsules having nanofibrous morphology using nanocrystalline cellulose (NCC) as one of the components of the assembly. The applicability of these nanoassemblies as drug delivery carriers has been explored by the loading of an anticancer drug, doxorubicin hydrochloride, and a water-insoluble drug, curcumin. Doxorubicin hydrochloride, having a good water solubility, is postloaded in the assembly. In the case of curcumin, which is very hydrophobic and has limited solubility in water, a stable dispersion is prepared via noncovalent interaction with NCC prior to incorporation in the LbL assembly. The interaction of various other lipophilic drugs with NCC was analyzed theoretically by molecular docking in consideration of NCC as a general carrier for hydrophobic drugs.

Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

NASA Astrophysics Data System (ADS)

Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

2017-12-01

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

Disorder induced semiconductor to metal transition and modifications of grain boundaries in nanocrystalline zinc oxide thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Fouran; Kumar, Vinod; Chaudhary, Babloo

2012-10-01

This paper report on the disorder induced semiconductor to metal transition (SMT) and modifications of grain boundaries in nanocrystalline zinc oxide thin film. Disorder is induced using energetic ion irradiation. It eliminates the possibility of impurities induced transition. However, it is revealed that some critical concentration of defects is needed for inducing such kind of SMT at certain critical temperature. Above room temperature, the current-voltage characteristics in reverse bias attributes some interesting phenomenon, such as electric field induced charge transfer, charge trapping, and diffusion of defects. The transition is explained by the defects induced disorder and strain in ZnO crystallitesmore » created by high density of electronic excitations.« less

Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

DOE PAGES

Craciun, D.; Socol, G.; Lambers, E.; ...

2015-01-17

Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH 4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH 4 pressures exhibited slightly higher nanohardness and Young modulus values than filmsmore » deposited under higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.« less

Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

PubMed

Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

2016-02-10

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

A light-trapping strategy for nanocrystalline silicon thin-film solar cells using three-dimensionally assembled nanoparticle structures.

PubMed

Ha, Kyungyeon; Jang, Eunseok; Jang, Segeun; Lee, Jong-Kwon; Jang, Min Seok; Choi, Hoseop; Cho, Jun-Sik; Choi, Mansoo

2016-02-05

We report three-dimensionally assembled nanoparticle structures inducing multiple plasmon resonances for broadband light harvesting in nanocrystalline silicon (nc-Si:H) thin-film solar cells. A three-dimensional multiscale (3DM) assembly of nanoparticles generated using a multi-pin spark discharge method has been accomplished over a large area under atmospheric conditions via ion-assisted aerosol lithography. The multiscale features of the sophisticated 3DM structures exhibit surface plasmon resonances at multiple frequencies, which increase light scattering and absorption efficiency over a wide spectral range from 350-1100 nm. The multiple plasmon resonances, together with the antireflection functionality arising from the conformally deposited top surface of the 3D solar cell, lead to a 22% and an 11% improvement in power conversion efficiency of the nc-Si:H thin-film solar cells compared to flat cells and cells employing nanoparticle clusters, respectively. Finite-difference time-domain simulations were also carried out to confirm that the improved device performance mainly originates from the multiple plasmon resonances generated from three-dimensionally assembled nanoparticle structures.

Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

PubMed Central

Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

2016-01-01

Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

NASA Astrophysics Data System (ADS)

Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

2016-05-01

Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

Structure, Morphology, and Optical Properties of Amorphous and Nanocrystalline Gallium Oxide Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, S. Sampath; Rubio, E. J.; Noor-A-Alam, M.

Ga2O3 thin films were produced by sputter deposition by varying the substrate temperature (Ts) in a wide range (Ts=25-800 oC). The structural characteristics and optical properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous while those grown at Ts≥500 oC were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films atmore » Ts=300-700 oC. The spectral transmission of the films increased with increasing temperature. The band gap of the films varied from 4.96 eV to 5.17 eV for a variation in Ts in the range 25-800 oC. A relationship between microstructure and optical property is discussed.« less

Design and investigation of properties of nanocrystalline diamond optical planar waveguides.

PubMed

Prajzler, Vaclav; Varga, Marian; Nekvindova, Pavla; Remes, Zdenek; Kromka, Alexander

2013-04-08

Diamond thin films have remarkable properties comparable with natural diamond. Because of these properties it is a very promising material for many various applications (sensors, heat sink, optical mirrors, chemical and radiation wear, cold cathodes, tissue engineering, etc.) In this paper we report about design, deposition and measurement of properties of optical planar waveguides fabricated from nanocrystalline diamond thin films. The nanocrystalline diamond planar waveguide was deposited by microwave plasma enhanced chemical vapor deposition and the structure of the deposited film was studied by scanning electron microscopy and Raman spectroscopy. The design of the presented planar waveguides was realized on the bases of modified dispersion equation and was schemed for 632.8 nm, 964 nm, 1 310 nm and 1 550 nm wavelengths. Waveguiding properties were examined by prism coupling technique and it was found that the diamond based planar optical element guided one fundamental mode for all measured wavelengths. Values of the refractive indices of our NCD thin film measured at various wavelengths were almost the same as those of natural diamond.

Optical Properties of Ar Ions Irradiated Nanocrystalline ZrC and ZrN Thin Films

NASA Technical Reports Server (NTRS)

Martin, C.; Miller, K. H.; Makino, H.; Craciun, D.; Simeone, D.; Craciun, V.

2017-01-01

Thin nanocrystalline ZrC and ZrN films (less than 400 nanometers), grown on (100) Si substrates at a substrate temperature of 500 degrees Centigrade by the pulsed laser deposition (PLD) technique, were irradiated by 800 kiloelectronvolts Ar ion irradiation with fluences from 1 times 10(sup 14) atoms per square centimeter up to 2 times 10(sup 15) atoms per square centimeter. Optical reflectance data, acquired from as-deposited and irradiated films, in the range of 500-50000 per centimeter (0.06–6 electronvolts), was used to assess the effect of irradiation on the optical and electronic properties. Both in ZrC and ZrN films we observed that irradiation affects the optical properties of the films mostly at low frequencies, which is dominated by the free carriers response. In both materials, we found a significant reduction in the free carriers scattering rate, i.e. possible increase in mobility, at higher irradiation flux. This is consistent with our previous findings that irradiation affects the crystallite size and the micro-strain, but it does not induce major structural changes.

Final Report: Hot Carrier Collection in Thin Film Silicon with Tailored Nanocrystalline/Amorphous Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, Reuben T.

This project developed, characterized, and perfected a new type of highly tunable nanocrystalline silicon (nc-Si:H) incorporating quantum confined silicon nanoparticles (SiNPs). A dual zone deposition process and system were developed and demonstrated. The depositions of SiNPs, the amorphous phase, and co-deposited material were characterized and optimized. Material design and interpretation of results were guided by new theoretical tools that examined both the electronic structure and carrier dynamics of this hybrid material. Heterojunction and p-i-n solar cells were demonstrated and characterized. Photo-thin-film-transistors allowed mobility to be studied as a function SiNP density in the films. Rapid (hot) transfer of carriers frommore » the amorphous matrix to the quantum confined SiNPs was observed and connected to reduced photo-degradation. The results carry quantum confined Si dots from a novelty to materials that can be harnessed for PV and optoelectronic applications. The growth process is broadly extendable with alternative amorphous matrices, novel layered structures, and alternative NPs easily accessible. The hot carrier effects hold the potential for third generation photovoltaics.« less

Characteristics of W Doped Nanocrystalline Carbon Films Prepared by Unbalanced Magnetron Sputtering.

PubMed

Park, Yong Seob; Park, Chul Min; Kim, Nam-Hoon; Kim, Jae-Moon

2016-05-01

Nanocrystalline tungsten doped carbon (WC) films were prepared by unbalanced magnetron sputtering. Tungsten was used as the doping material in carbon thin films with the aim of application as a contact strip in an electric railway. The structural, physical, and electrical properties of the fabricated WC films with various DC bias voltages were investigated. The films had a uniform and smooth surface. Hardness and frication characteristics of the films were improved, and the resistivity and sheet resistance decreased with increasing negative DC bias voltage. These results are associated with the nanocrystalline WC phase and sp(2) clusters in carbon networks increased by ion bombardment enhanced with increasing DC bias voltage. Consequently, the increase of sp(2) clusters containing WC nanocrystalline in the carbon films is attributed to the improvement in the physical and electrical properties.

Method for the preparation of nanocrystalline diamond thin films

DOEpatents

Gruen, Dieter M.; Krauss, Alan R.

1998-01-01

A method and system for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip.

Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukoje, Ivana D., E-mail: ivanav@vinca.rs; Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com; Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com

Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical andmore » morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.« less

Optical properties of PVA capped nanocrystalline Cd1-xZnxS thin film synthesized by chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Gogoi, Lipika; Chaliha, Sumbit; Saikia, Prasanta Kumar

2018-04-01

A simple cost effective Chemical Bath Deposition (CBD) technique has been employed for the preparation of nanocrystalline Cd1-xZnxS thin films in an alkaline medium at 333K for 120 minutes in polymer matrix. Optical parameters such as transmittance, optical band gap, reflectance, refractive index and extinction coefficient of the films was made using UV-Visible spectrophotometer. UV-spectroscopy study shows a good transmittance of 80-88% in visible wavelength region for the deposited films. The direct band gap energy (Eg) for the deposited films ranged from 3.5 to 3.7 eV depending on attribution of Zn into CdS. It shows a blue shift with respect to bulk value. A increase in transmittance and band gap is found with the increase of volume of Zn content. Cd1-xZnxS thin films exhibit the least reflectance for all the wavelengths in the visible region. The refractive indices (n) of the Cd1-xZnxS films were found in the range 1.38 to 2.94 in the visible region.

Method for the preparation of nanocrystalline diamond thin films

DOEpatents

Gruen, D.M.; Krauss, A.R.

1998-06-30

A method and system are disclosed for manufacturing nanocrystalline diamond film on a substrate such as field emission tips. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrocarbon and possibly hydrogen, and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous vapor and deposition of a diamond film on the field emission tip. 40 figs.

Hydrogen plasma treatment of very thin p-type nanocrystalline Si films grown by RF-PECVD in the presence of B(CH3)3

PubMed Central

Filonovich, Sergej Alexandrovich; Águas, Hugo; Busani, Tito; Vicente, António; Araújo, Andreia; Gaspar, Diana; Vilarigues, Marcia; Leitão, Joaquim; Fortunato, Elvira; Martins, Rodrigo

2012-01-01

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (∼20 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film. PMID:27877504

Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films.

PubMed

Vishwas, M; Sharma, Sudhir Kumar; Rao, K Narasimha; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

2010-03-01

Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO(2) thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO(2) films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO(2) films was estimated by Tauc's method at different annealing temperature. Copyright 2010 Elsevier B.V. All rights reserved.

Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells.

PubMed

Park, Jinjoo; Shin, Chonghoon; Park, Hyeongsik; Jung, Junhee; Lee, Youn-Jung; Bong, Sungjae; Dao, Vinh Ai; Balaji, Nagarajan; Yi, Junsin

2015-03-01

We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (σ(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with σ(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively.

Effect Of Chromium Underlayer On The Properties Of Nano-Crystalline Diamond Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garratt, Elias; AlFaify, Salem; Yoshitake, T.

2013-01-11

This paper investigated the effect of chromium underlayer on the structure, microstructure and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on silicon substrate with a thin film of chromium as an underlayer. The composition, structure and microstructure of the deposited layers were analyzed using non-Rutherford Backscattering Spectrometry, Raman Spectroscopy, Near-Edge X-Ray Absorption Fine Structure, X-ray Diffraction and Atomic Force Microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphiticmore » phases of the films evaluated by x-ray and optical spectroscopic analysis determined consistency between sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.« less

Effect of chromium underlayer on the properties of nano-crystalline diamond films

NASA Astrophysics Data System (ADS)

Garratt, E.; AlFaify, S.; Yoshitake, T.; Katamune, Y.; Bowden, M.; Nandasiri, M.; Ghantasala, M.; Mancini, D. C.; Thevuthasan, S.; Kayani, A.

2013-01-01

This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

Soft magnetic properties of nanocrystalline FeRuGaSi-Hf alloy films and head characteristics for the embedded thin film tape head

NASA Astrophysics Data System (ADS)

Ohmori, H.; Shoji, M.; Kobayashi, T.; Yamamoto, T.; Sugiyama, Y.; Hayashi, K.; Hono, K.

1996-04-01

The Hf-added FeRuGaSi alloy film has an amorphous structure in the as-deposited state and becomes nanocrystalline after annealing. Due to this structure change from crystalline to amorphous by the addition of Hf, soft magnetic degradation of the film deposited on the slant grooved substrate, which is necessary for the sophisticated embedded thin film (ETF) head structure, is greatly suppressed and the undesirable film stress is relieved. The FeRuGaSi-Hf alloy film has higher resistivity and permeability at high frequencies than those of sendust film, and the read/write characteristics of this alloy film show better performance than sendust film.

Nanocrystalline ceramic materials

DOEpatents

Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

1994-01-01

A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

Effect of Various Catalysts on the Stability of Characteristics of Acetone Sensors Based on Thin Nanocrystalline SnO2 Films

NASA Astrophysics Data System (ADS)

Sevastyanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Khludkova, L. S.; Chernikov, E. V.; Davydova, T. A.

2018-02-01

The results of studies of electrical and gas sensitive characteristics of acetone sensors based on thin nanocrystalline SnO2 films with various catalysts deposited on the surface (Pt/Pd, Au) and introduced into the volume (Au, Ni, Co) are presented. Films containing impurities of gold and 3d-metals were obtained by the method of magnetron sputtering of mosaic targets. Particular attention was paid to the influence of the longterm tests and humidity level on the properties of sensors. It is shown that the sensors with the deposited dispersed gold layers with Au+Ni and, especially, Au+Co additives introduced into the volume are characterized by the increased stability in the process of testing under prolonged exposure to acetone and also under conditions of varying humidity.

Nanocrystalline ceramic materials

DOEpatents

Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

1994-06-14

A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

The influence of interfacial defects on fast charge trapping in nanocrystalline oxide-semiconductor thin film transistors

NASA Astrophysics Data System (ADS)

Kim, Taeho; Hur, Jihyun; Jeon, Sanghun

2016-05-01

Defects in oxide semiconductors not only influence the initial device performance but also affect device reliability. The front channel is the major carrier transport region during the transistor turn-on stage, therefore an understanding of defects located in the vicinity of the interface is very important. In this study, we investigated the dynamics of charge transport in a nanocrystalline hafnium-indium-zinc-oxide thin-film transistor (TFT) by short pulse I-V, transient current and 1/f noise measurement methods. We found that the fast charging behavior of the tested device stems from defects located in both the front channel and the interface, following a multi-trapping mechanism. We found that a silicon-nitride stacked hafnium-indium-zinc-oxide TFT is vulnerable to interfacial charge trapping compared with silicon-oxide counterpart, causing significant mobility degradation and threshold voltage instability. The 1/f noise measurement data indicate that the carrier transport in a silicon-nitride stacked TFT device is governed by trapping/de-trapping processes via defects in the interface, while the silicon-oxide device follows the mobility fluctuation model.

A study on the structural and mechanical properties of nanocrystalline CuS thin films grown by chemical bath deposition technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, Nillohit; Sinha, Arijit; Khan, Gobinda Gopal

2011-01-15

We report a chemical route for the deposition of nanocrystalline thin films of CuS, using aqueous solutions of Cu(CH{sub 3}COO){sub 2}, SC(NH{sub 2}){sub 2} and N(CH{sub 2}CH{sub 2}OH){sub 3} [triethanolamine, i.e. TEA] in proper concentrations and ratios. The films were structurally characterized using X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM) and optical analysis [both photo luminescence (PL) and ultraviolet-visible (UV-vis)]. Optical studies showed a large blue shift in the band gap energy of the films due to quantum confinement effect exerted by the nanocrystals. From both XRD and FESEM analyses, formation of CuS nanocrystals with sizes withinmore » 10-15 nm was evident. A study on the mechanical properties was carried out using nanoindentation and nanoscratch techniques, which showed good mechanical stability and high adherence of the films with the bottom substrate. Such study on the mechanical properties of the CuS thin films is being reported here for the first time. Current-voltage (I-V) measurements were also carried out for the films, which showed p-type conductivity.« less

Thermal conductivity of amorphous and nanocrystalline silicon films prepared by hot-wire chemical-vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jugdersuren, B.; Kearney, B. T.; Queen, D. R.

We report 3..omega.. thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity of the films is controlled by the hydrogen dilution during growth. The thermal conductivity of the amorphous silicon film is in agreement with several previous reports of amorphous silicon prepared by a variety of deposition techniques. The thermal conductivity of the as-grown nanocrystalline silicon film is 70% higher and increases 35% more after an anneal at 600 degrees C. They all have similarly weak temperature dependence. Structural analysis shows that the as-grown nanocrystalline siliconmore » is approximately 60% crystalline, nanograins and grain boundaries included. The nanograins, averaging 9.1 nm in diameter in the as-grown film, are embedded in an amorphous matrix. The grain size increases to 9.7 nm upon annealing, accompanied by the disappearance of the amorphous phase. We extend the models of grain boundary scattering of phonons with two different non-Debye dispersion relations to explain our result of nanocrystalline silicon, confirming the strong grain size dependence of heat transport for nanocrystalline materials. However, the similarity in thermal conductivity between amorphous and nanocrystalline silicon suggests the heat transport mechanisms in both structures may not be as dissimilar as we currently understand.« less

Mechanical properties of nanocrystalline cobalt

NASA Astrophysics Data System (ADS)

Karimpoor, Amir A.; Erb, Uwe

2006-05-01

Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

Investigations into the formation of nanocrystalline quantum dot thin films by mist deposition process

NASA Astrophysics Data System (ADS)

Kshirsagar, Aditya

Semiconductor nanocrystalline quantum dots (NQDs) have material properties remarkably different compared to bulk semiconductors with the same material composition. These NQDs have various novel applications in the electronic and photonic industry, such as light emitting diodes (LEDs) and flat-panel displays. In these applications, ultra-thin films of NQDs in the monolayer regime are needed to ensure optimal current transport properties and device efficiency. There is ongoing search to find a suitable method to deposit and pattern such ultra-thin films of quantum dots with few monolayer thicknesses. Several competing approaches are available, each with its pros and cons. This study explores mist deposition as the technique to fill this void. In this study, ultra-thin films of quantum dots are deposited on diverse substrates and are characterized to understand the mechanics of mist deposition. Various applications of blanket deposited and patterned quantum dot films are studied. The results discussed here include atomic force microscopy analysis of the films to study surface morphology, fluorescence microscopy to study light emission and optical microscope images to study patterning techniques. These results demonstrate the ability of mist deposition to form 1-4 monolayers thick, uniform, defect-free patterned films with root mean square (RMS) surface roughness less than 2 nm. LEDs fabricated using mist deposition show a peak luminescence greater than 500 cd/m2 for matched red, yellow and green devices using Alq3 as the electron transport layer, and over 9000 cd/m2 for red devices using ZnO as the electron transport layer, respectively. In addition to the experimental approach to study the process and explore potential applications, simulation and modeling are carried out to understand the various aspects of mist deposition. A mathematical model is presented which discusses the atomization process of the precursor solution, the physics involved during the deposition

Properties of Nanocrystalline Cubic Silicon Carbide Thin Films Prepared by Hot-Wire Chemical Vapor Deposition Using SiH4/CH4/H2 at Various Substrate Temperatures

NASA Astrophysics Data System (ADS)

Tabata, Akimori; Komura, Yusuke; Hoshide, Yoshiki; Narita, Tomoki; Kondo, Akihiro

2008-01-01

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH4/CH4/H2 gases, and the influence of substrate temperature, Ts (104 < Ts < 434 °C), on the properties of the SiC thin films was investigated. X-ray diffraction patterns and Raman scattering spectra revealed that nanocrystalline cubic SiC (nc-3C-SiC) films grew at Ts above 187 °C, while completely amorphous films grew at Ts = 104 °C. Fourier transform infrared absorption spectra revealed that the crystallinity of the nc-3C-SiC was improved with increasing Ts up to 282 °C and remained almost unchanged with a further increase in Ts from 282 to 434 °C. The spin density was reduced monotonically with increasing Ts.

Formation of nanocrystalline SiGe in Polycrystalline-Ge/Si thin film without any metal induced crystallization

NASA Astrophysics Data System (ADS)

Tah, Twisha; Singh, Ch. Kishan; Madapu, K. K.; Polaki, S. R.; Ilango, S.; David, C.; Dash, S.; Panigrahi, B. K.

2017-05-01

The formation of nanocrystalline SiGe without the aid of metal induced crystallization is reported. Re-crystallization of the as-deposited poly-Ge film (deposited at 450 °C) leads to development of regions with depleted Ge concentration upon annealing at 500 °C. Clusters with crystalline facet containing both nanocrystalline SiGe and crystalline Ge phase starts appearing at 600 °C. The structural phase characteristics were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The stoichiometry of the SiGe phase was estimated from the positions of the Raman spectral peaks.

Preparation and bioactive properties of nanocrystalline hydroxyapatite thin films obtained by conversion of atomic layer deposited calcium carbonate.

PubMed

Holopainen, Jani; Kauppinen, Kyösti; Mizohata, Kenichiro; Santala, Eero; Mikkola, Esa; Heikkilä, Mikko; Kokkonen, Hanna; Leskelä, Markku; Lehenkari, Petri; Tuukkanen, Juha; Ritala, Mikko

2014-09-01

Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts.

A Nanocrystalline Fe2O3 Film Anode Prepared by Pulsed Laser Deposition for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Teng, Xiaoling; Qin, Youzhi; Wang, Xia; Li, Hongsen; Shang, Xiantao; Fan, Shuting; Li, Qiang; Xu, Jie; Cao, Derang; Li, Shandong

2018-02-01

Nanocrystalline Fe2O3 thin films are deposited directly on the conduct substrates by pulsed laser deposition as anode materials for lithium-ion batteries. We demonstrate the well-designed Fe2O3 film electrodes are capable of excellent high-rate performance (510 mAh g- 1 at high current density of 15,000 mA g- 1) and superior cycling stability (905 mAh g- 1 at 100 mA g- 1 after 200 cycles), which are among the best reported state-of-the-art Fe2O3 anode materials. The outstanding lithium storage performances of the as-synthesized nanocrystalline Fe2O3 film are attributed to the advanced nanostructured architecture, which not only provides fast kinetics by the shortened lithium-ion diffusion lengths but also prolongs cycling life by preventing nanosized Fe2O3 particle agglomeration. The electrochemical performance results suggest that this novel Fe2O3 thin film is a promising anode material for all-solid-state thin film batteries.

Ultrasonic Emission from Nanocrystalline Porous Silicon

NASA Astrophysics Data System (ADS)

Shinoda, Hiroyuki; Koshida, Nobuyoshi

A simple layer structure composed of a metal thin film and a porous silicon layer on a silicon substrate generates intense and wide-band airborne ultrasounds. The large-bandwidth and the fidelity of the sound reproduction are leveraged in applications varying from sound-based measurement to a scientific study of animal ecology. This chapter describes the basic principle of the ultrasound generation. The macroscopic properties of the low thermal conductivity and the small heat capacity of nanocrystalline porous silicon thermally induce ultrasonic emission. The state-of-the-art of the achievable sound pressure and sound signal properties is introduced, with the technological and scientific applications of the devices.

Structural, electrical and optical properties of nanostructured ZrO2 thin film deposited by SILAR method

NASA Astrophysics Data System (ADS)

Salodkar, R. V.; Belkhedkar, M. R.; Nemade, S. D.

2018-05-01

Successive Ionic Layer Adsorption and Reaction (SILAR) method has been employed to deposit nanocrystalline ZrO2 thin film of thickness 91 nm onto glass substrates using ZrOCl2.8H2O and NaOH as cationic and anionic precursors respectively. The structural and surface morphological characterizations have been carried out by means of X-ray diffraction and field emission scanning electron microscopy confirms the nanocrystalline nature of ZrO2 thin film. The direct optical band gap and activation energy of the ZrO2 thin film are found to be 4.74 and 0.80eV respectively.

Solution-processed nanocrystalline PbS on paper substrate with pencil traced electrodes as visible photodetector

NASA Astrophysics Data System (ADS)

Vankhade, Dhaval; Chaudhuri, Tapas K.

2018-04-01

Paper-based PbS photodetector sensitive in the visible spectrum is reported. Nanocrystalline PbS-on-paper devices are fabricated by a spin coating method on white paper (300 GSM) from a methanolic precursor solution. Photodetector cells of gap 0.2 cm and length 0.5 cm are prepared by drawing contacts by monolithic cretacolor 8B pencil. X-ray diffractometer confirmed the deposition of nanocrystalline PbS films with 14 nm crystallites. The SEM illustrated the uniform coating of nanocrystalline PbS thin films on cellulose fibres of papers having an average thickness of fibres are 10 µm. The linear J-V characteristics in dark and under illumination of light using graphite trace on nanocrystalline PbS-on-paper shows good ohmic contact. The resistivity of pencil trace is 30 Ω.cm. Spectral response measurements of photodetector reveal the excellent sensitivity from 400 to 700 nm with a peak at 550 nm. The best responsivity anddetectivity are 0.7 A/W and 1.4 × 1012 Jones respectively. These paper-based low-cost photodetectors devices have fast photoresponse and recovery without baseline deviation.

Probing nanocrystalline grain dynamics in nanodevices

PubMed Central

Yeh, Sheng-Shiuan; Chang, Wen-Yao; Lin, Juhn-Jong

2017-01-01

Dynamical structural defects exist naturally in a wide variety of solids. They fluctuate temporally and hence can deteriorate the performance of many electronic devices. Thus far, the entities of these dynamic objects have been identified to be individual atoms. On the other hand, it is a long-standing question whether a nanocrystalline grain constituted of a large number of atoms can switch, as a whole, reversibly like a dynamical atomic defect (that is, a two-level system). This is an emergent issue considering the current development of nanodevices with ultralow electrical noise, qubits with long quantum coherence time, and nanoelectromechanical system sensors with ultrahigh resolution. We demonstrate experimental observations of dynamic nanocrystalline grains that repeatedly switch between two or more metastable coordinate states. We study temporal resistance fluctuations in thin ruthenium dioxide (RuO2) metal nanowires and extract microscopic parameters, including relaxation time scales, mobile grain sizes, and the bonding strengths of nanograin boundaries. These material parameters are not obtainable by other experimental approaches. When combined with previous in situ high-resolution transmission electron microscopy, our electrical method can be used to infer rich information about the structural dynamics of a wide variety of nanodevices and new two-dimensional materials. PMID:28691094

The Sulphur Poisoning Behaviour of Gadolinia Doped Ceria Model Systems in Reducing Atmospheres

PubMed Central

Gerstl, Matthias; Nenning, Andreas; Iskandar, Riza; Rojek-Wöckner, Veronika; Bram, Martin; Hutter, Herbert; Opitz, Alexander Karl

2016-01-01

An array of analytical methods including surface area determination by gas adsorption using the Brunauer, Emmett, Teller (BET) method, combustion analysis, XRD, ToF-SIMS, TEM and impedance spectroscopy has been used to investigate the interaction of gadolinia doped ceria (GDC) with hydrogen sulphide containing reducing atmospheres. It is shown that sulphur is incorporated into the GDC bulk and might lead to phase changes. Additionally, high concentrations of silicon are found on the surface of model composite microelectrodes. Based on these data, a model is proposed to explain the multi-facetted electrochemical degradation behaviour encountered during long term electrochemical measurements. While electrochemical bulk properties of GDC stay largely unaffected, the surface polarisation resistance is dramatically changed, due to silicon segregation and reaction with adsorbed sulphur. PMID:28773771

Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells

NASA Astrophysics Data System (ADS)

Klingsporn, M.; Kirner, S.; Villringer, C.; Abou-Ras, D.; Costina, I.; Lehmann, M.; Stannowski, B.

2016-06-01

Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

Effect of fluorine doping on highly transparent conductive spray deposited nanocrystalline tin oxide thin films

NASA Astrophysics Data System (ADS)

Moholkar, A. V.; Pawar, S. M.; Rajpure, K. Y.; Bhosale, C. H.; Kim, J. H.

2009-09-01

The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence of optical, structural and electrical properties of SnO 2 films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning electron microscope (SEM) and Hall effect studies have been performed on SnO 2:F (FTO) films coated on glass substrates. The film thickness varies from 800 to 1572 nm. X-ray diffraction pattern reveals the presence of cassiterite structure with (2 0 0) preferential orientation for FTO films. The crystallite size varies from 35 to 66 nm. SEM and AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The 20 wt% F doped film has a minimum resistivity of 3.8 × 10 -4 Ω cm, carrier density of 24.9 × 10 20 cm -3 and mobility of 6.59 cm 2 V -1 s -1. The sprayed FTO film having minimum resistance of 3.42 Ω/cm 2, highest figure of merit of 6.18 × 10 -2 Ω -1 at 550 nm and 96% IR reflectivity suggest, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter electrode.

Study of electronic characteristics of heterojunction with intrinsic thin-layer devices and defect density profile of nanocrystalline silicon germanium devices

NASA Astrophysics Data System (ADS)

Mulder, Watson

Heterojunction with Intrinsic Thin-layer (HIT) solar cells are an important photovoltaic technology, recently reaching record power conversion efficiencies. HIT cells hold advantages over the conventional crystalline Si solar cells, such as their fabrication at lower temperatures and their shorter fabrication time. It is important to understand the electronic characteristics and transport properties of HIT cells to continue to improve their efficiencies. The fundamental measurements of a HIT solar cell with an innovative n+/p/p+ structure are presented. We also report on a series of these HIT cells fabricated on wafers with different doping concentrations, observing the relationship between doping concentration and characteristics such as open-circuit voltage and diffusion length. Nanocrystalline Silicon-Germanium (nc-SiGe) is a useful material for photovoltaic devices and photodetectors. The material features good absorption extending to the infrared region even in thin layers. Its bandgap can be adjusted between that of Si (˜1.1 eV) and Ge (˜0.7 eV) by varying the alloy composition ratio during deposition. However, there has been very little previous work to measure and understand the defect density spectrum of nc-SiGe. Defects are responsible for controlling the recombination and thus the performance of solar cell devices. Capacitance-Frequency measurements at various temperatures are used in order to estimate the trap density profile within the bandgap of nc-SiGe.

Thermally Stable Nanocrystalline Steel

NASA Astrophysics Data System (ADS)

Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

2017-10-01

Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

Effect of RF power density on micro- and macro-structural properties of PECVD grown hydrogenated nanocrystalline silicon thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gokdogan, Gozde Kahriman, E-mail: gozdekahriman@gmail.com; Anutgan, Tamila, E-mail: tamilaanutgan@karabuk.edu.tr

2016-03-25

This contribution provides the comparison between micro- and macro-structure of hydrogenated nanocrystalline silicon (nc-Si:H) thin films grown by plasma enhanced chemical vapor deposition (PECVD) technique under different RF power densities (P{sub RF}: 100−444 mW/cm{sup 2}). Micro-structure is assessed through grazing angle X-ray diffraction (GAXRD), while macro-structure is followed by surface and cross-sectional morphology via field emission scanning electron microscopy (FE-SEM). The nanocrystallite size (∼5 nm) and FE-SEM surface conglomerate size (∼40 nm) decreases with increasing P{sub RF}, crystalline volume fraction reaches maximum at 162 mW/cm{sup 2}, FE-SEM cross-sectional structure is columnar except for the film grown at 162 mW/cm{sup 2}. The dependence of previously determinedmore » ‘oxygen content–refractive index’ correlation on obtained macro-structure is investigated. Also, the effect of P{sub RF} is discussed in the light of plasma parameters during film deposition process and nc-Si:H film growth models.« less

Growth of nanocrystalline Cu2ZnSnS4 thin films using the spray pyrolysis technique and their characterization

NASA Astrophysics Data System (ADS)

Chandel, Tarun; Halaszova, Sona; Prochazka, Michal; Hasko, Daniel; Velic, Dusan; Thakur, Vikas; Dwivedi, Shailendra Kumar; Zaman, M. Buhanuz; Rajaram, Poolla

2018-05-01

Nanocrystalline thin films of Cu2ZnSnS4 (CZTS) were grown on the glass substrates using the spray pyrolysis technique. The films were grown at a substrate temperature of 300 °C after which they were annealed at 350 °C in vacuum. X-ray diffraction (XRD) studies showed that the films crystallized in the kesterite structure. Energy dispersive analysis of X-rays (EDAX) studies showed that the films possess the desired stoichiometry i.e. the proportion of Cu:Zn:Sn:S in the CZTS solid solution is close to 2:1:1:4. Secondary Ions Mass Spectroscopy (SIMS) depth profiling confirmed the uniformity in elemental composition along the depth of the films. SEM studies showed that the films are covered with CZTS particles forming sheet like structures. AFM studies show that the size of the particles on the surface of the films is around 10-15 nm. UV-VIS-NIR transmission spectra were used to determine the optical band gap of the CZTS films which was found to be around 1.55eV.

Tribochemistry of contact interfaces of nanocrystalline molybdenum carbide films

NASA Astrophysics Data System (ADS)

Kumar, D. Dinesh; Kumar, N.; Panda, Kalpataru; Kamalan Kirubaharan, A. M.; Kuppusami, P.

2018-07-01

Transition metal carbides (TMC) are known for their improved tribological properties and are sensitive to the tribo-atmospheric environment. Nanocrystalline molybdenum carbide (MoC) thin films were deposited by DC magnetron sputtering technique using reactive CH4 gas. The friction and wear resistance properties of MoC thin films were significantly improved in humid-atmospheric condition as compared to high-vacuum tribo-condition. A comprehensive chemical analysis of deformed contact interfaces was carried out by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. XPS and Raman spectroscopy showed the formation of stable molybdenum-oxide (MoO), molybdenum carbide (MoC) and amorphous carbon (a-C) tribo-phases. Moreover, during the sliding in humid-atmospheric condition, these phases were extensively deposited on the sliding steel ball counter body which significantly protected against undesirable friction and wear.

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

DOE PAGES

El Atwani, Osman; Nathaniel, James; Leff, Asher C.; ...

2017-05-12

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

Direct Observation of Sink-Dependent Defect Evolution in Nanocrystalline Iron under Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Atwani, Osman; Nathaniel, James; Leff, Asher C.

Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K. Interstitial loops of a 0 /2 [111] Burgers vector were directly observed asmore » a result of the displacement damage. Loop density trends with grain size demonstrated an increase in the nanocrystalline (<100 nm) regime, but scattered behavior in the transition from the nanocrystalline to the ultra-fine regime (100–500 nm). To examine the validity of such trends, loop density and area for different grains at various irradiation doses were compared and revealed efficient defect absorption in the nanocrystalline grain size regime, but loop coalescence in the ultra-fine grain size regime. Lastly, a relationship between the denuded zone formation, a measure of grain boundary absorption efficiency, grain size, grain boundary type and misorientation angle is determined.« less

Band gap states in nanocrystalline WO3 thin films studied by soft x-ray spectroscopy and optical spectrophotometry.

PubMed

Johansson, M B; Kristiansen, P T; Duda, L; Niklasson, G A; Österlund, L

2016-11-30

Nanocrystalline tungsten trioxide (WO3) thin films prepared by DC magnetron sputtering have been studied using soft x-ray spectroscopy and optical spectrophotometry. Resonant inelastic x-ray scattering (RIXS) measurements reveal band gap states in sub-stoichiometric γ-WO3-x with x  =  0.001-0.005. The energy positions of these states are in good agreement with recently reported density functional calculations. The results were compared with optical absorption measurements in the near infrared spectral region. An optical absorption peak at 0.74 eV is assigned to intervalence transfer of polarons between W sites. A less prominent peak at energies between 0.96 and 1.16 eV is assigned to electron excitation of oxygen vacancies. The latter results are supported by RIXS measurements, where an energy loss in this energy range was observed, and this suggests that electron transfer processes involving transitions from oxygen vacancy states can be observed in RIXS. Our results have implications for the interpretation of optical properties of WO3, and the optical transitions close to the band gap, which are important in photocatalytic and photoelectrochemical applications.

Magnetoresistance measurements of superconducting molybdenum nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baskaran, R., E-mail: baskaran@igcar.gov.in; Arasu, A. V. Thanikai; Amaladass, E. P.

2016-05-23

Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

Investigations of the drift mobility of carriers and density of states in nanocrystalline CdS thin films

NASA Astrophysics Data System (ADS)

Singh, Baljinder; Singh, Janpreet; Kaur, Jagdish; Moudgil, R. K.; Tripathi, S. K.

2016-06-01

Nanocrystalline Cadmium Sulfide (nc-CdS) thin films have been prepared on well-cleaned glass substrate at room temperature (300 K) by thermal evaporation technique using inert gas condensation (IGC) method. X-ray diffraction (XRD) analysis reveals that the films crystallize in hexagonal structure with preferred orientation along [002] direction. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) studies reveal that grains are spherical in shape and uniformly distributed over the glass substrates. The optical band gap of the film is estimated from the transmittance spectra. Electrical parameters such as Hall coefficient, carrier type, carrier concentration, resistivity and mobility are determined using Hall measurements at 300 K. Transit time and mobility are estimated from Time of Flight (TOF) transient photocurrent technique in gap cell configuration. The measured values of electron drift mobility from TOF and Hall measurements are of the same order. Constant Photocurrent Method in ac-mode (ac-CPM) is used to measure the absorption spectra in low absorption region. By applying derivative method, we have converted the measured absorption data into a density of states (DOS) distribution in the lower part of the energy gap. The value of Urbach energy, steepness parameter and density of defect states have been calculated from the absorption and DOS spectra.

Investigations of the electron field emission properties and microstructure correlation in sulfur-incorporated nanocrystalline carbon thin films

NASA Astrophysics Data System (ADS)

Gupta, S.; Weiner, B. R.; Morell, G.

2002-06-01

Results are reported on the electron field emission properties of sulfur (S)-incorporated nanocrystalline carbon (n-C:S) thin films grown on molybdenum (Mo) substrates by hot-filament chemical vapor deposition (HFCVD) technique. In addition to the conventionally used methane (CH4) as carbon precursor with high hydrogen (H2) dilution, hydrogen sulfide-hydrogen (H2)S/H2 premix gas was used for sulfur incorporation. The field emission properties for the S-incorporated films were investigated systematically as a function of substrate temperature (TS) and sulfur concentration. Lowest turn-on field achieved was observed at around 4.0 V/mum for the n-C:S sample grown at TS of 900 degC with 500 ppm of H2S. These results are compared with those films grown without sulfur (n-C) at a particular TS. The turn-on field was found to be almost half for the S-assisted film thus demonstrating the effect of sulfur addition to the chemical vapor deposition process. An inverse relation between turn-on field (EC), growth temperature and sulfur concentration was found. The S incorporation also causes significant microstructural changes, as characterized with non-destructive complementary ex situ techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy (RS). S-assisted films show relatively smoother and finer-grained surfaces than those grown without it. These findings are discussed in terms of the dual role of sulfur in enhancing the field emission properties by controlling the sp2 C cluster size and introducing substantial structural defects through its incorporation. The in-plane correlation length (La) of sp2 C cluster was determined from the intensity ratio of the D- and G-bands I(D)/I(G) in the visible RS as a function of deposition temperature and sulfur concentration using a phenomenological model. The turn-on field was found to decrease with increasing sp2 C cluster size in general ranging from 0.8 to 1.4 nm. The films having sp2 C

Nonvolatile memory behavior of nanocrystalline cellulose/graphene oxide composite films

NASA Astrophysics Data System (ADS)

Valentini, L.; Cardinali, M.; Fortunati, E.; Kenny, J. M.

2014-10-01

With the continuous advance of modern electronics, the demand for nonvolatile memory cells rapidly grows. In order to develop post-silicon electronic devices, it is necessary to find innovative solutions to the eco-sustainability problem of materials for nonvolatile memory cells. In this work, we realized a resistive memory device based on graphene oxide (GO) and GO/cellulose nanocrystals (CNC) thin films. Aqueous solutions of GO and GO with CNC have been prepared and drop cast between two metal electrodes. Such thin-film based devices showed a transition between low and high conductivity states upon the forward and backward sweeping of an external electric field. This reversible current density transition behavior demonstrates a typical memory characteristic. The obtained results open an easy route for electronic information storage based on the integration of nanocrystalline cellulose onto graphene based devices.

Nonvolatile memory behavior of nanocrystalline cellulose/graphene oxide composite films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valentini, L., E-mail: luca.valentini@unipg.it; Cardinali, M.; Fortunati, E.

2014-10-13

With the continuous advance of modern electronics, the demand for nonvolatile memory cells rapidly grows. In order to develop post-silicon electronic devices, it is necessary to find innovative solutions to the eco-sustainability problem of materials for nonvolatile memory cells. In this work, we realized a resistive memory device based on graphene oxide (GO) and GO/cellulose nanocrystals (CNC) thin films. Aqueous solutions of GO and GO with CNC have been prepared and drop cast between two metal electrodes. Such thin-film based devices showed a transition between low and high conductivity states upon the forward and backward sweeping of an external electricmore » field. This reversible current density transition behavior demonstrates a typical memory characteristic. The obtained results open an easy route for electronic information storage based on the integration of nanocrystalline cellulose onto graphene based devices.« less

Vapor deposition of thin films

DOEpatents

Smith, David C.; Pattillo, Stevan G.; Laia, Jr., Joseph R.; Sattelberger, Alfred P.

1992-01-01

A highly pure thin metal film having a nanocrystalline structure and a process of preparing such highly pure thin metal films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium by plasma assisted chemical vapor deposition of, e.g., rhodium(allyl).sub.3, iridium(allyl).sub.3, molybdenum(allyl).sub.4, tungsten(allyl).sub.4, rhenium(allyl).sub.4, platinum(allyl).sub.2, or palladium(allyl).sub.2 are disclosed. Additionally, a general process of reducing the carbon content of a metallic film prepared from one or more organometallic precursor compounds by plasma assisted chemical vapor deposition is disclosed.

Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiO{sub x} layers for application in solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klingsporn, M.; Costina, I.; Kirner, S.

2016-06-14

Nanocrystalline silicon suboxides (nc-SiO{sub x}) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO{sub 0.8}:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressuremore » from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.« less

Preparation of high-quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder.

PubMed

Riedl, Thomas; Gemming, Thomas; Mickel, Christine; Eymann, Konrad; Kirchner, Alexander; Kieback, Bernd

2012-06-01

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations. Copyright © 2011 Wiley Periodicals, Inc.

Carrier mobility enhancement of nano-crystalline semiconductor films: Incorporation of redox -relay species into the grain boundary interface

NASA Astrophysics Data System (ADS)

Desilva, L. A.; Bandara, T. M. W. J.; Hettiarachchi, B. H.; Kumara, G. R. A.; Perera, A. G. U.; Rajapaksa, R. M. G.; Tennakone, K.

Dye-sensitized and perovskite solar cells and other nanostructured heterojunction electronic devices require securing intimate electronic contact between nanostructured surfaces. Generally, the strategy is solution phase coating of a hole -collector over a nano-crystalline high-band gap n-type oxide semiconductor film painted with a thin layer of the light harvesting material. The nano-crystallites of the hole - collector fills the pores of the painted oxide surface. Most ills of these devices are associated with imperfect contact and high resistance of the hole conducting layer constituted of nano-crystallites. Denaturing of the delicate light harvesting material forbid sintering at elevated temperatures to reduce the grain boundary resistance. It is found that the interfacial and grain boundary resistance can be significantly reduced via incorporation of redox species into the interfaces to form ultra-thin layers. Suitable redox moieties, preferably bonded to the surface, act as electron transfer relays greatly reducing the film resistance offerring a promising method of enhancing the effective hole mobility of nano-crystalline hole-collectors and developing hole conductor paints for application in nanostructured devices.

Dendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteries.

PubMed

Liu, Zhen; Cui, Tong; Pulletikurthi, Giridhar; Lahiri, Abhishek; Carstens, Timo; Olschewski, Mark; Endres, Frank

2016-02-18

Metallic zinc is a promising anode material for rechargeable Zn-based batteries. However, the dendritic growth of zinc has prevented practical applications. Herein it is demonstrated that dendrite-free zinc deposits with a nanocrystalline structure can be obtained by using nickel triflate as an additive in a zinc triflate containing ionic liquid. The formation of a thin layer of Zn-Ni alloy (η- and γ-phases) on the surface and in the initial stages of deposition along with the formation of an interfacial layer on the electrode strongly affect the nucleation and growth of zinc. A well-defined and uniform nanocrystalline zinc deposit with particle sizes of about 25 nm was obtained in the presence of Ni(II) . Further, it is shown that the nanocrystalline Zn exhibits a high cycling stability even after 50 deposition/stripping cycles. This strategy of introducing an inorganic metal salt in ionic liquid electrolytes can be considered as an efficient way to obtain dendrite-free zinc. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanostructured PdO Thin Film from Langmuir-Blodgett Precursor for Room-Temperature H2 Gas Sensing.

PubMed

Choudhury, Sipra; Betty, C A; Bhattacharyya, Kaustava; Saxena, Vibha; Bhattacharya, Debarati

2016-07-06

Nanoparticulate thin films of PdO were prepared using the Langmuir-Blodgett (LB) technique by thermal decomposition of a multilayer film of octadecylamine (ODA)-chloropalladate complex. The stable complex formation of ODA with chloropalladate ions (present in subphase) at the air-water interface was confirmed by the surface pressure-area isotherm and Brewster angle microscopy. The formation of nanocrystalline PdO thin film after thermal decomposition of as-deposited LB film was confirmed by X-ray diffraction and Raman spectroscopy. Nanocrystalline PdO thin films were further characterized by using UV-vis and X-ray photoelectron spectroscopic (XPS) measurements. The XPS study revealed the presence of prominent Pd(2+) with a small quantity (18%) of reduced PdO (Pd(0)) in nanocrystalline PdO thin film. From the absorption spectroscopic measurement, the band gap energy of PdO was estimated to be 2 eV, which was very close to that obtained from specular reflectance measurements. Surface morphology studies of these films using atomic force microscopy and field-emission scanning electron microscopy indicated formation of nanoparticles of size 20-30 nm. These PdO film when employed as a chemiresistive sensor showed H2 sensitivity in the range of 30-4000 ppm at room temperature. In addition, PdO films showed photosensitivity with increase in current upon shining of visible light.

Nanocrystalline SnO2 formation using energetic ion beam.

PubMed

Mohanty, T; Batra, Y; Tripathi, A; Kanjilal, D

2007-06-01

Nanocrystalline tin oxide (SnO2) thin films grown by RF magnetron sputtering technique were characterized by UV-Visible absorption spectroscopy and Photoluminescence spectroscopy. From atomic force microscopic (AFM) and Glancing angle X-ray diffraction (GAXRD) measurements, the radius of grains was found to be approximately 6+/-2 nm. The thin films were bombarded with 250 keV Xe2+ ion beam to observe the stability of nanophases against radiation. For ion bombarded films, optical absorption band edge is shifted towards red region. Atomic force microscopy studies show that the radius of the grains was increased to approximately 8 +/- 1 nm and the grains were nearly uniform in size. The size of the grains has been reduced after ion bombardment in the case of films grown on Si. During this process, defects such as vacancies, voids were generated in the films as well as in the substrates. Ion bombardment induces local temperature increase of thin films causing melting of films. Ion beam induced defects enhances the diffusion of atoms leading to uniformity in size of grains. The role of matrix on ion beam induced grain growth is discussed.

Gadolinia-Doped Ceria Cathodes for Electrolysis of CO2

NASA Technical Reports Server (NTRS)

Adler, Stuart B.

2009-01-01

Gadolinia-doped ceria, or GDC, (Gd(0.4)Ce(0.6)O(2-delta), where the value of delta in this material varies, depending on the temperature and oxygen concentration in the atmosphere in which it is being used) has shown promise as a cathode material for high-temperature electrolysis of carbon dioxide in solid oxide electrolysis cells. The polarization resistance of a GDC electrode is significantly less than that of an otherwise equivalent electrode made of any of several other materials that are now in use or under consideration for use as cathodes for reduction of carbon dioxide. In addition, GDC shows no sign of deterioration under typical temperature and gas-mixture operating conditions of a high-temperature electrolyzer. Electrolysis of CO2 is of interest to NASA as a way of generating O2 from the CO2 in the Martian atmosphere. On Earth, a combination of electrolysis of CO2 and electrolysis of H2O might prove useful as a means of generating synthesis gas (syngas) from the exhaust gas of a coal- or natural-gas-fired power plant, thereby reducing the emission of CO2 into the atmosphere. The syngas a mixture of CO and H2 could be used as a raw material in the manufacture, via the Fisher-Tropsch process, of synthetic fuels, lubrication oils, and other hydrocarbon prod

Chemical routes to nanocrystalline and thin-film III-VI and I-III-VI semiconductors

NASA Astrophysics Data System (ADS)

Hollingsworth, Jennifer Ann

1999-11-01

The work encompasses: (1) catalyzed low-temperature, solution-based routes to nano- and microcrystalline III-VI semiconductor powders and (2) spray chemical vapor deposition (spray CVD) of I-III-VI semiconductor thin films. Prior to this work, few, if any, examples existed of chemical catalysis applied to the synthesis of nonmolecular, covalent solids. New crystallization strategies employing catalysts were developed for the regioselective syntheses of orthorhombic InS (beta-InS), the thermodynamic phase, and rhombohedral InS (R-InS), a new, metastable structural isomer. Growth of beta-InS was facilitated by a solvent-suspended, molten-metal flux in a process similar to the SolutionLiquid-Solid (SLS) growth of InP and GaAs fibers and single-crystal whiskers. In contrast, metastable R-InS, having a pseudo-graphitic layered structure, was prepared selectively when the molecular catalyst, benzenethiol, was present in solution and the inorganic "catalyst" (metal flux) was not present. In the absence of any crystal-growth facilitator, metal flux or benzenethiol, amorphous product was obtained under the mild reaction conditions employed (T ≤ 203°C). The inorganic and organic catalysts permitted the regio-selective syntheses of InS and were also successfully applied to the growth of network and layered InxSey compounds, respectively, as well as nanocrystalline In2S3. Extensive microstructural characterization demonstrated that the layered compounds grew as fullerene-like nanostructures and large, colloidal single crystals. Films of the I-III-VI compounds, CuInS2, CuGaS2, and Cu(In,Ga)S 2, were deposited by spray CVD using the known single-source metalorganic precursor, (Ph3P)2CuIn(SEt)4, a new precursor, (Ph3P)2CuGa(SEt)3, and a mixture of the two precursors, respectively. The CulnS2 films exhibited a variety of microstructures from dense and faceted or platelet-like to porous and dendritic. Crystallographic orientations ranged from strongly [112] to strongly [220

Solid state consolidation nanocrystalline copper-tungsten using cold spray

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas

It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. Wemore » demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.« less

Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

NASA Astrophysics Data System (ADS)

Luo, X. M.; Zhang, B.; Zhang, G. P.

2014-09-01

Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

Micromechanics Modeling of Fracture in Nanocrystalline Metals

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

2002-01-01

Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

Self-ion irradiation effects on mechanical properties of nanocrystalline zirconium films

DOE PAGES

Wang, Baoming; Haque, M. A.; Tomar, Vikas; ...

2017-07-13

Zirconium thin films were irradiated at room temperature with an 800 keV Zr + beam using a 6 MV HVE Tandem accelerator to 1.36 displacement per atom damage. Freestanding tensile specimens, 100 nm thick and 10 nm grain size, were tested in-situ inside a transmission electron microscope. Significant grain growth (>300%), texture evolution, and displacement damage defects were observed. Here, stress-strain profiles were mostly linear elastic below 20 nm grain size, but above this limit the samples demonstrated yielding and strain hardening. Experimental results support the hypothesis that grain boundaries in nanocrystalline metals act as very effective defect sinks.

Synthesis of Nanocrystalline SnOx (x = 1–2) Thin Film Using a Chemical Bath Deposition Method with Improved Deposition Time, Temperature and pH

PubMed Central

Ebrahimiasl, Saeideh; Yunus, Wan Md. Zin Wan; Kassim, Anuar; Zainal, Zulkarnain

2011-01-01

Nanocrystalline SnOx (x = 1–2) thin films were prepared on glass substrates by a simple chemical bath deposition method. Triethanolamine was used as complexing agent to decrease time and temperature of deposition and shift the pH of the solution to the noncorrosive region. The films were characterized for composition, surface morphology, structure and optical properties. X-ray diffraction analysis confirms that SnOx thin films consist of a polycrystalline structure with an average grain size of 36 nm. Atomic force microscopy studies show a uniform grain distribution without pinholes. The elemental composition was evaluated by energy dispersive X-ray spectroscopy. The average O/Sn atomic percentage ratio is 1.72. Band gap energy and optical transition were determined from optical absorbance data. The film was found to exhibit direct and indirect transitions in the visible spectrum with band gap values of about 3.9 and 3.7 eV, respectively. The optical transmittance in the visible region is 82%. The SnOx nanocrystals exhibit an ultraviolet emission band centered at 392 nm in the vicinity of the band edge, which is attributed to the well-known exciton transition in SnOx. Photosensitivity was detected in the positive region under illumination with white light. PMID:22163690

Determination of the five parameter grain boundary character distribution of nanocrystalline alpha-zirconium thin films using transmission electron microscopy

DOE PAGES

Ghamarian, I.; Samani, P.; Rohrer, G. S.; ...

2017-03-24

Grain boundary engineering and other fundamental materials science problems (e.g., phase transformations and physical properties) require an improvement in the understanding of the type and population of grain boundaries in a given system – yet, databases are limited in number and spare in detail, including for hcp crystals such as zirconium. One way to rapidly obtain databases to analyze is to use small-grained materials and high spatial resolution orientation microscopy techniques, such as ASTAR™/precession electron diffraction. To demonstrate this, a study of grain boundary character distributions was conducted for α-zirconium deposited at room temperature on fused silica substrates using physicalmore » vapor deposition. The orientation maps of the nanocrystalline thin films were acquired by the ASTARα/precession electron diffraction technique, a new transmission electron microscope based orientation microscopy method. The reconstructed grain boundaries were classified as pure tilt, pure twist, 180°-twist and 180°-tilt grain boundaries based on the distribution of grain boundary planes with respect to the angle/axis of misorientation associated with grain boundaries. The results of the current study were compared to the results of a similar study on α-titanium and the molecular dynamics results of grain boundary energy for α-titanium.« less

The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

NASA Astrophysics Data System (ADS)

Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

2016-04-01

Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations

NASA Astrophysics Data System (ADS)

Johansson, Malin B.; Baldissera, Gustavo; Valyukh, Iryna; Persson, Clas; Arwin, Hans; Niklasson, Gunnar A.; Österlund, Lars

2013-05-01

The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (Ptot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low Ptot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies Eg ≈ 3.1 eV, which increase with increasing Ptot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic δ-WO3, and monoclinic γ- and ε-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The δ-WO3 and γ-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3 eV) and allowed transitions (>3.8 eV). The calculations show that Eg in ε-WO3 is higher than in the δ-WO3 and γ-WO3 phases, which provides an explanation for the Ptot dependence of the optical data.

Method of making nanocrystalline alpha alumina

DOEpatents

Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

1992-01-01

Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

Nanocrystalline films for gas-reactive applications

DOEpatents

Eastman, Jeffrey A.; Thompson, Loren J.

2004-02-17

A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vargas, Mirella; Murphy, N. R.; Ramana, C. V., E-mail: rvchintalapalle@utep.edu

2014-03-10

Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and themore » microstructure of HfO{sub 2} films.« less

Nanocrystalline CuInS2 And CuInSe2 via Low-Temperature Pyrolysis Of Single-Source Molecular Precursors

NASA Technical Reports Server (NTRS)

Castro, Stephanie L.; Bailey, Sheila G.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Hepp, Aloysius F.

2002-01-01

Single-source precursors are molecules which contain all the necessary elements for synthesis of a desired material. Thermal decomposition of the precursor results in the formation of the material with the correct stoichiometry, as a nanocrystalline powder or a thin film. Nanocrystalline materials hold potential as components of next-generation Photovoltaic (PV) devices. Presented here are the syntheses of CuInS2 and CuInSe2 nanocrystals from the precursors (PPh3)2CuIn(SEt)4 and (PPh3)2CuIn(SePh)4, respectively. The size of the nanocrystals varies with the reaction temperature; a minimum of 200 C is required for the formation of the smallest CuInS2 crystals (approximately 1.6 nm diameter); at 300 C, crystals are approximately 7 nm.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Compositional and structural analysis of nitrogen incorporated and ion implanted diamond thin films

NASA Astrophysics Data System (ADS)

Garratt, Elias James

Significant progress in area of nano-structured thin film systems has taken place in recent decades. In particular, diamond thin film systems are being widely studied for their wear resistant, optical and electronic properties. Of the various methods researchers use to modify the structure of such films, three techniques in particular are of interest due to their versatility: modification of the growth atmosphere, growth on metalized substrates, providing an interfacial layer, and modification through post-growth ion implantation. The aim of this study is to investigate the effects each has to the structure and composition of elements. Different techniques are applied in each section; nitrogen gas dilution in a microwave plasma CVD system, diamond deposition on a metal interfacial layer and ion implantation in thin nanocrystalline diamond film. The forms of nanocrystalline diamond film resulting from such modifications are investigated using advanced spectroscopic and spectrometric techniques, as well as mechanical testing and surface mapping. The impact of these characterizations will provide valuable perspective to researchers in materials science. Understanding the changes to the structure and properties of this class of thin films, which can be induced through various mechanisms, will allow future researchers to refine these films towards technological applications in areas of hard coatings, electronics and photonics.

Electrochemically synthesized nanocrystalline spinel thin film for high performance supercapacitor

NASA Astrophysics Data System (ADS)

Gupta, Vinay; Gupta, Shubhra; Miura, Norio

Spinels are not known for their supercapacitive nature. Here, we have explored electrochemically synthesized nanostructured NiCo 2O 4 spinel thin-film electrode for electrochemical supercapacitors. The nanostructured NiCo 2O 4 spinel thin film exhibited a high specific capacitance value of 580 F g -1 and an energy density of 32 Wh kg -1 at the power density of 4 kW kg -1, accompanying with good cyclic stability.

Thermal conductivity of ultrathin nano-crystalline diamond films determined by Raman thermography assisted by silicon nanowires

NASA Astrophysics Data System (ADS)

Anaya, Julian; Rossi, Stefano; Alomari, Mohammed; Kohn, Erhard; Tóth, Lajos; Pécz, Béla; Kuball, Martin

2015-06-01

The thermal transport in polycrystalline diamond films near its nucleation region is still not well understood. Here, a steady-state technique to determine the thermal transport within the nano-crystalline diamond present at their nucleation site has been demonstrated. Taking advantage of silicon nanowires as surface temperature nano-sensors, and using Raman Thermography, the in-plane and cross-plane components of the thermal conductivity of ultra-thin diamond layers and their thermal barrier to the Si substrate were determined. Both components of the thermal conductivity of the nano-crystalline diamond were found to be well below the values of polycrystalline bulk diamond, with a cross-plane thermal conductivity larger than the in-plane thermal conductivity. Also a depth dependence of the lateral thermal conductivity through the diamond layer was determined. The results impact the design and integration of diamond for thermal management of AlGaN/GaN high power transistors and also show the usefulness of the nanowires as accurate nano-thermometers.

Grain boundary phase transformations in PtAu and relevance to thermal stabilization of bulk nanocrystalline metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Brien, C. J.; Barr, C. M.; Price, P. M.

There has recently been a great deal of interest in employing immiscible solutes to stabilize nanocrystalline microstructures. Existing modeling efforts largely rely on mesoscale Monte Carlo approaches that employ a simplified model of the microstructure and result in highly homogeneous segregation to grain boundaries. However, there is ample evidence from experimental and modeling studies that demonstrates segregation to grain boundaries is highly non-uniform and sensitive to boundary character. This work employs a realistic nanocrystalline microstructure with experimentally relevant global solute concentrations to illustrate inhomogeneous boundary segregation. Furthermore, experiments quantifying segregation in thin films are reported that corroborate the prediction thatmore » grain boundary segregation is highly inhomogeneous. In addition to grain boundary structure modifying the degree of segregation, the existence of a phase transformation between low and high solute content grain boundaries is predicted. In order to conduct this study, new embedded atom method interatomic potentials are developed for Pt, Au, and the PtAu binary alloy.« less

Grain boundary phase transformations in PtAu and relevance to thermal stabilization of bulk nanocrystalline metals

DOE PAGES

O’Brien, C. J.; Barr, C. M.; Price, P. M.; ...

2017-10-31

There has recently been a great deal of interest in employing immiscible solutes to stabilize nanocrystalline microstructures. Existing modeling efforts largely rely on mesoscale Monte Carlo approaches that employ a simplified model of the microstructure and result in highly homogeneous segregation to grain boundaries. However, there is ample evidence from experimental and modeling studies that demonstrates segregation to grain boundaries is highly non-uniform and sensitive to boundary character. This work employs a realistic nanocrystalline microstructure with experimentally relevant global solute concentrations to illustrate inhomogeneous boundary segregation. Furthermore, experiments quantifying segregation in thin films are reported that corroborate the prediction thatmore » grain boundary segregation is highly inhomogeneous. In addition to grain boundary structure modifying the degree of segregation, the existence of a phase transformation between low and high solute content grain boundaries is predicted. In order to conduct this study, new embedded atom method interatomic potentials are developed for Pt, Au, and the PtAu binary alloy.« less

Mesoporous nanocrystalline film architecture for capacitive storage devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunn, Bruce S.; Tolbert, Sarah H.; Wang, John

A mesoporous, nanocrystalline, metal oxide construct particularly suited for capacitive energy storage that has an architecture with short diffusion path lengths and large surface areas and a method for production are provided. Energy density is substantially increased without compromising the capacitive charge storage kinetics and electrode demonstrates long term cycling stability. Charge storage devices with electrodes using the construct can use three different charge storage mechanisms immersed in an electrolyte: (1) cations can be stored in a thin double layer at the electrode/electrolyte interface (non-faradaic mechanism); (2) cations can interact with the bulk of an electroactive material which then undergoesmore » a redox reaction or phase change, as in conventional batteries (faradaic mechanism); or (3) cations can electrochemically adsorb onto the surface of a material through charge transfer processes (faradaic mechanism).« less

AFM investigation and optical band gap study of chemically deposited PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mansoor, M.; Abubakar; Asim, M. M.

2016-08-01

The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

Aging of Nanocrystalline Mackinawite (FeS): Mineralogical and Physicochemical Properties

NASA Astrophysics Data System (ADS)

Jeong, H. Y.; Lee, H.

2011-12-01

Due to the extraordinary physical properties and high surface areas, nanocrystalline minerals have been widely investigated for their potential uses in treating contaminated groundwaters and surface waters. Most previous studies in this field have focused on either preparation of nanocrystalline minerals or measurement of their reactivity with environmental contaminants. Nanocrystalline minerals, due to the inherent thermodynamic instability, tend to change the physicochemical and mineralogical properties over time, usually resulting in the decreased reactivity. Thus, to better assess the long-term effectiveness of nanocrystalline minerals in field applications, such "aging" effects should be clearly delineated. In the present work, we have investigated the aging impact on nanocrystalline mackinawite (FeS), the ubiquitous Fe-bearing mineral in anoxic sulfidic sediments. Mackinawite (FeS) is known to be an effective scavenger for metal pollutants and a strong reducing reagent for chromate and chlorinated organic compounds. Our preliminary results indicate that nanocrystalline FeS ages via Ostwald ripening, particle aggregation, or mineralogical transformation. By X-ray diffraction (XRD) analysis, aging of nanocrystalline FeS via Ostwald ripening is found to be dominant at acidic pH. Cryogenic transmission electron microscopy (TEM) shows that particle aggregation is most evident at neutral pH. Transformation of nanosized FeS into a more thermodynamically stable greigite (Fe3S4) is observed in the presence of folic acid at acidic pH. The pH-dependent aging process may be linked with changes in the apparent solubility and surface charge of FeS with pH. The Ostwald ripening or particle aggregation of nanocrystalline FeS leads to the decrease surface area, thus causing the decreased reactivity. Given the less reactivity of greigite, the transformation of nanocrystalline FeS to greigite is also expected to result in the decreased reactivity.

Nano-crystalline porous tin oxide film for carbon monoxide sensing

NASA Technical Reports Server (NTRS)

Liu, Chung-Chiun (Inventor); Savinell, Robert F. (Inventor); Jin, Zhihong (Inventor)

2000-01-01

A tin oxide sol is deposited on platinum electrodes (12) of a sensor (10). The sol is calcined at a temperature of 500 to 800.degree. C. to produce a thin film of tin oxide with a thickness of about 150 nm to 2 .mu. and having a nano-crystalline structure with good stability. The sensor rapidly detects reducing gases, such as carbon monoxide, or hydrocarbons and organic vapors. Sensors using films calcined at around 700.degree. C. have high carbon monoxide selectivity with a response time of around 4 minutes and a recovery time of 1 minute, and therefore provide good detection systems for detection of trace amounts of pollutants such as toxic and flammable gases in homes, industrial settings, and hospitals.

Characterization of Softmagnetic Thin Layers Using Barkhausen Noise Microscopy

DTIC Science & Technology

2001-04-01

magnetoresistive (MR) sensors softmagnetic thin layer systems are used. Optimal performance of these layers requires homogeneous magnetic properties , especially a...Sendust, used in inductive sensors and nanocrystalline NiFe , used in MR-sensors. In quality correlations to Barkhausen noise parameters were found...Brillouin scattering are frequently used. An important issue is the influence of mechanical properties , e.g. residual stress on the magnetic performance

X-ray absorption fine structure and x-ray diffraction studies of crystallographic grains in nanocrystalline FePd:Cu thin films

NASA Astrophysics Data System (ADS)

Krupinski, M.; Perzanowski, M.; Polit, A.; Zabila, Y.; Zarzycki, A.; Dobrowolska, A.; Marszalek, M.

2011-03-01

FePd alloys have recently attracted considerable attention as candidates for ultrahigh density magnetic storage media. In this paper we investigate FePd thin alloy film with a copper admixture composed of nanometer-sized grains. [Fe(0.9 nm)/Pd(1.1 nm)/Cu(d nm)]×5 multilayers were prepared by thermal deposition at room temperature in UHV conditions on Si(100) substrates covered by 100 nm SiO2. The thickness of the copper layer has been changed from 0 to 0.4 nm. After deposition, the multilayers were rapidly annealed at 600 °C in a nitrogen atmosphere, which resulted in the creation of the FePd:Cu alloy. The structure of alloy films obtained this way was determined by x-ray diffraction (XRD), glancing angle x-ray diffraction, and x-ray absorption fine structure (EXAFS). The measurements clearly showed that the L10 FePd:Cu nanocrystalline phase has been formed during the annealing process for all investigated copper compositions. This paper concentrates on the crystallographic grain features of FePd:Cu alloys and illustrates that the EXAFS technique, supported by XRD measurements, can help to extend the information about grain size and grain shape of poorly crystallized materials. We show that, using an appropriate model of the FePd:Cu grains, the comparison of EXAFS and XRD results gives a reasonable agreement.

Nanocrystalline heterojunction materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2003-07-15

Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Nonlinear optical parameters of nanocrystalline AZO thin film measured at different substrate temperatures

NASA Astrophysics Data System (ADS)

Jilani, Asim; Abdel-wahab, M. Sh; Al-ghamdi, Attieh A.; Dahlan, Ammar sadik; Yahia, I. S.

2016-01-01

The 2.2 wt% of aluminum (Al)-doped zinc oxide (AZO) transparent and preferential c-axis oriented thin films were prepared by using radio frequency (DC/RF) magnetron sputtering at different substrate temperature ranging from room temperature to 200 °C. For structural analysis, X-ray Diffraction (XRD) and Atomic Force Electron Microscope (AFM) was used for morphological studies. The optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss, tangent loss, first and third order nonlinear optical properties of transparent films were investigated. High transmittance above 90% and highly homogeneous surface were observed in all samples. The substrate temperature plays an important role to get the best transparent conductive oxide thin films. The substrate temperature at 150 °C showed the growth of highly transparent AZO thin film. Energy gap increased with the increased in substrate temperature of Al doped thin films. Dielectric constant and loss were found to be photon energy dependent with substrate temperature. The change in substrate temperature of Al doped thin films also affect the non-liner optical properties of thin films. The value of χ(3) was found to be changed with the grain size of the thin films that directly affected by the substrate temperature of the pure and Al doped ZnO thin films.

Synthesis of Nano-Crystalline Gamma-TiAl Materials

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Vasquez, Peter

2003-01-01

One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

Pulsed photonic fabrication of nanostructured metal oxide thin films

NASA Astrophysics Data System (ADS)

Bourgeois, Briley B.; Luo, Sijun; Riggs, Brian C.; Adireddy, Shiva; Chrisey, Douglas B.

2017-09-01

Nanostructured metal oxide thin films with a large specific surface area are preferable for practical device applications in energy conversion and storage. Herein, we report instantaneous (milliseconds) photonic synthesis of three-dimensional (3-D) nanostructured metal oxide thin films through the pulsed photoinitiated pyrolysis of organometallic precursor films made by chemical solution deposition. High wall-plug efficiency-pulsed photonic irradiation (xenon flash lamp, pulse width of 1.93 ms, fluence of 7.7 J/cm2 and frequency of 1.2 Hz) is used for scalable photonic processing. The photothermal effect of subsequent pulses rapidly improves the crystalline quality of nanocrystalline metal oxide thin films in minutes. The following paper highlights pulsed photonic fabrication of 3-D nanostructured TiO2, Co3O4, and Fe2O3 thin films, exemplifying a promising new method for the low-cost and high-throughput manufacturing of nanostructured metal oxide thin films for energy applications.

Application of micro- and nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Sotnikova, Yu S.; Demina, T. S.; Istomin, A. V.; Goncharuk, G. P.; Grandfils, Ch; Akopova, T. A.; Zelenetskii, A. N.; Babayevsky, P. G.

2018-04-01

Micro- and nanocrystalline forms of cellulose were extracted from flax stalks and evaluated in terms of their applicability for various materials science tasks. It was revealed that both form of cellulose had anisometric morphology with length of 27.1 μm and 159 nm; diameter of 8.7 μm and 85 nm, respectively. They were used as reinforcing fillers for fabrication of composite films based on hydroxyethylcellulose. Film-forming and mechanical properties of the composite materials were significantly varied in dependence on filler content (0–10 wt.%) and size. As a second option of micro- and nanocrystalline cellulose application, a study of their effectiveness as stabilizing agents for oil/water Pickering emulsions was carried out. In contrast to micron-sized cellulose the nanocrystalline form appeared to be successful in the process of CH2Cl2/water interface stabilization and fabrication of polylactide microparticles via oil/water Pickering emulsion solvent evaporation technique.

The activation energy for nanocrystalline diamond films deposited from an Ar/H2/CH4 hot-filament reactor.

PubMed

Barbosa, D C; Melo, L L; Trava-Airoldi, V J; Corat, E J

2009-06-01

In this work we have investigated the effect of substrate temperature on the growth rate and properties of nanocrystalline diamond thin films deposited by hot filament chemical vapor deposition (HFCVD). Mixtures of 0.5 vol% CH4 and 25 vol% H2 balanced with Ar at a pressure of 50 Torr and typical deposition time of 12 h. We present the measurement of the activation energy by accurately controlling the substrate temperature independently of other CVD parameters. Growth rates have been measured in the temperature range from 550 to 800 degrees C. Characterization techniques have involved Raman spectroscopy, high resolution X-ray difractometry and scanning electron microscopy. We also present a comparison with most activation energy for micro and nanocrystalline diamond determinations in the literature and propose that there is a common trend in most observations. The result obtained can be an evidence that the growth mechanism of NCD in HFCVD reactors is very similar to MCD growth.

Investigations of Nanocrystalline Alloy Electrospark Coating Made of Nanocrystalline Alloy Based on 5БДCP Ferrum

NASA Astrophysics Data System (ADS)

Kolomeichenko, A. V.; Kuznetsov, I. S.; Izmaylov, A. Yu; Solovyev, R. Yu; Sharifullin, S. N.

2017-09-01

The article describes the properties of wear resistant electrospark coating made of nanocrystalline alloy of type 5БДCP (Finemet). It is proved that electrospark coating has nanocrystalline structure which is like amorphous matrix with nanocrystals α - Fe. Coating thickness is 33 μm, micro-hardness is 8461 - 11357 MPa, wear resistance is 0,55×104s/g. Coating ofnanocrystalline alloy of type 5БДCP can be used to increase wear resistance of machinery working surfaces.

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

DTIC Science & Technology

2014-11-01

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and...3. DATES COVERED (From - To) August 2014 4. TITLE AND SUBTITLE Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by

Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

USDA-ARS?s Scientific Manuscript database

Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

Nanocrystalline Heterojunction Materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2004-02-03

Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Methods for preparation of nanocrystalline rare earth phosphates for lighting applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comanzo, Holly Ann; Manoharan, Mohan; Martins Loureiro, Sergio Paulo

Disclosed here are methods for the preparation of optionally activated nanocrystalline rare earth phosphates. The optionally activated nanocrystalline rare earth phosphates may be used as one or more of quantum-splitting phosphor, visible-light emitting phosphor, vacuum-UV absorbing phosphor, and UV-emitting phosphor. Also disclosed herein are discharge lamps comprising the optionally activated nanocrystalline rare earth phosphates provided by these methods.

Barium titanate nanocrystals and nanocrystal thin films: Synthesis, ferroelectricity, and dielectric properties

NASA Astrophysics Data System (ADS)

Huang, Limin; Chen, Zhuoying; Wilson, James D.; Banerjee, Sarbajit; Robinson, Richard D.; Herman, Irving P.; Laibowitz, Robert; O'Brien, Stephen

2006-08-01

Advanced applications for high k dielectric and ferroelectric materials in the electronics industry continues to demand an understanding of the underlying physics in decreasing dimensions into the nanoscale. We report the synthesis, processing, and electrical characterization of thin (<100nm thick) nanostructured thin films of barium titanate (BaTiO3) built from uniform nanoparticles (<20nm in diameter). We introduce a form of processing as a step toward the ability to prepare textured films based on assembly of nanoparticles. Essential to this approach is an understanding of the nanoparticle as a building block, combined with an ability to integrate them into thin films that have uniform and characteristic electrical properties. Our method offers a versatile means of preparing BaTiO3 nanocrystals, which can be used as a basis for micropatterned or continuous BaTiO3 nanocrystal thin films. We observe the BaTiO3 nanocrystals crystallize with evidence of tetragonality. We investigated the preparation of well-isolated BaTiO3 nanocrystals smaller than 10nm with control over aggregation and crystal densities on various substrates such as Si, Si /SiO2, Si3N4/Si, and Pt-coated Si substrates. BaTiO3 nanocrystal thin films were then prepared, resulting in films with a uniform nanocrystalline grain texture. Electric field dependent polarization measurements show spontaneous polarization and hysteresis, indicating ferroelectric behavior for the BaTiO3 nanocrystalline films with grain sizes in the range of 10-30nm. Dielectric measurements of the films show dielectic constants in the range of 85-90 over the 1KHz -100KHz, with low loss. We present nanocrystals as initial building blocks for the preparation of thin films which exhibit highly uniform nanostructured texture and grain sizes.

Nanocrystalline cerium oxide materials for solid fuel cell systems

DOEpatents

Brinkman, Kyle S

2015-05-05

Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE PAGES

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; ...

2016-03-11

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tay, Roland Yingjie; Temasek Laboratories@NTU, 50 Nanyang Avenue, Singapore, Singapore 639798; Tsang, Siu Hon

Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO{sub 2}/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random andmore » uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications.« less

Thin film solar cells with Si nanocrystallites embedded in amorphous intrinsic layers by hot-wire chemical vapor deposition.

PubMed

Park, Seungil; Parida, Bhaskar; Kim, Keunjoo

2013-05-01

We investigated the thin film growths of hydrogenated silicon by hot-wire chemical vapor deposition with different flow rates of SiH4 and H2 mixture ambient and fabricated thin film solar cells by implementing the intrinsic layers to SiC/Si heterojunction p-i-n structures. The film samples showed the different infrared absorption spectra of 2,000 and 2,100 cm(-1), which are corresponding to the chemical bonds of SiH and SiH2, respectively. The a-Si:H sample with the relatively high silane concentration provides the absorption peak of SiH bond, but the microc-Si:H sample with the relatively low silane concentration provides the absorption peak of SiH2 bond as well as SiH bond. Furthermore, the microc-Si:H sample showed the Raman spectral shift of 520 cm(-1) for crystalline phase Si bonds as well as the 480 cm(-1) for the amorphous phase Si bonds. These bonding structures are very consistent with the further analysis of the long-wavelength photoconduction tail and the formation of nanocrystalline Si structures. The microc-Si:H thin film solar cell has the photovoltaic behavior of open circuit voltage similar to crystalline silicon thin film solar cell, indicating that microc-Si:H thin film with the mixed phase of amorphous and nanocrystalline structures show the carrier transportation through the channel of nanocrystallites.

[Preparation and transmissivity of ZnS nanocolumn thin films with glancing angle deposition technology].

PubMed

Lu, Li-Fang; Xu, Zheng; Zhang, Fu-Jun; Zhao, Su-Ling; Song, Dan-Dan; Li, Jun-Ming; Wang, Yong-Sheng; Xu, Xu-Rong

2010-02-01

Nanocrystalline ZnS thin films were fabricated by glancing angle deposition (GLAD) technology in an electron beam evaporation system. Deposition was carried out in the custom vacuum chamber at a base pressure 3 x 10(-4) Pa, and the deposition rate was fixed at 0.2 nm x s(-1). ZnS films were deposited on pieces of indium tin oxide (ITO) substrates when the oblique angle of the substrate relative to the incoming molecular flux was set to 0 degrees, 80 degrees and 85 degrees off the substrate normal respectively. X-ray diffraction (XRD) spectra and scanning electron microscope (SEM) images showed that ZnS nanocrystalline films were formed on the substrates at different oblique angle, but the nanocolumn structure was only formed under the situation of alpha = 80 degrees and 85 degrees. The dynamics during the deposition process of the ZnS films at alpha = 0 degrees, 80 degrees and 85 degrees was analyzed. The transmitted spectra of ZnS thin films deposited on ITO substrates showed that the ZnS nanocolumn thin films could enhance the transmissivity in visible range. The ZnS nanocolumn could be used into electroluminescence device, and it would enhance the luminous efficiency of the device.

Reproduction of mouse-pup ultrasonic vocalizations by nanocrystalline silicon thermoacoustic emitter

NASA Astrophysics Data System (ADS)

Kihara, Takashi; Harada, Toshihiro; Kato, Masahiro; Nakano, Kiyoshi; Murakami, Osamu; Kikusui, Takefumi; Koshida, Nobuyoshi

2006-01-01

As one of the functional properties of ultrasound generator based on efficient thermal transfer at the nanocrystalline silicon (nc-Si) layer surface, its potential as an ultrasonic simulator of vocalization signals is demonstrated by using the acoustic data of mouse-pup calls. The device composed of a surface-heating thin-film electrode, an nc-Si layer, and a single-crystalline silicon (c-Si) wafer, exhibits an almost completely flat frequency response over a wide range without any mechanical surface vibration systems. It is shown that the fabricated emitter can reproduce digitally recorded ultrasonic mouse-pups vocalizations very accurately in terms of the call duration, frequency dispersion, and sound pressure level. The thermoacoustic nc-Si device provides a powerful physical means for the understanding of ultrasonic communication mechanisms in various living animals.

Some aspects of pulsed laser deposition of Si nanocrystalline films

NASA Astrophysics Data System (ADS)

Polyakov, B.; Petruhins, A.; Butikova, J.; Kuzmin, A.; Tale, I.

2009-11-01

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed. in here

Electrodeposition of Nanocrystalline Co-P Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2009-09-02

Electrodeposition  of Nanocrystalline Co‐P  Coatings as a Hard Chrome Alternative Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Electrodeposition of Nanocrystalline Co‐P Coatings as a Hard Chrome Alternative 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Defense Conference – 2 September 2009 Conventional  Electrodeposits Polycrystalline (10‐100 µm) Electrodeposited Nanocrystalline Materials Pulsed

Structural, optical and magnetic behaviour of nanocrystalline Volborthite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

2016-05-06

Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

Metastable tantalum oxide formation during the devitrification of amorphous tantalum thin films

DOE PAGES

Donaldson, Olivia K.; Hattar, Khalid; Trelewicz, Jason R.

2016-07-04

Microstructural evolution during the devitrification of amorphous tantalum thin films synthesized via pulsed laser deposition was investigated using in situ transmission electron microscopy (TEM) combined with ex situ isothermal annealing, bright-field imaging, and electron-diffraction analysis. The phases formed during crystallization and their stability were characterized as a function of the chamber pressure during deposition, devitrification temperature, and annealing time. A range of metastable nanocrystalline tantalum oxides were identified following devitrification including multiple orthorhombic oxide phases, which often were present with, or evolved to, the tetragonal TaO 2 phase. While the appearance of these phases indicated the films were evolving tomore » the stable form of tantalum oxide—monoclinic tantalum pentoxide—it was likely not achieved for the conditions considered due to an insufficient amount of oxygen present in the films following deposition. Nevertheless, the collective in situ and ex situ TEM analysis applied to thin film samples enabled the isolation of a number of metastable tantalum oxides. As a result, new insights were gained into the transformation sequence and stability of these nanocrystalline phases, which presents opportunities for the development of advanced tantalum oxide-based dielectric materials for novel memristor designs.« less

[Raman studies of nanocrystalline BaTiO3 ceramics].

PubMed

Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

2008-12-01

High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

Electrochemical and fluorescence properties of SnO2 thin films and its antibacterial activity

NASA Astrophysics Data System (ADS)

Henry, J.; Mohanraj, K.; Sivakumar, G.; Umamaheswari, S.

2015-05-01

Nanocrystalline SnO2 thin films were deposited by a simple and inexpensive sol-gel spin coating technique and the films were annealed at two different temperatures (350 °C and 450 °C). Structural, vibrational, optical and electrochemical properties of the films were analyzed using XRD, FTIR, UV-Visible, fluorescence and cyclic voltammetry techniques respectively and their results are discussed in detail. The antimicrobial properties of SnO2 thin films were investigated by agar agar method and the results confirm the antibacterial activity of SnO2 against Escherichia coli and Bacillus.

Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

DOEpatents

Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

2007-12-25

Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

PubMed

Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

2011-12-01

To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

Nanocrystalline copper films are never flat

NASA Astrophysics Data System (ADS)

Zhang, Xiaopu; Han, Jian; Plombon, John J.; Sutton, Adrian P.; Srolovitz, David J.; Boland, John J.

2017-07-01

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.

Syntheses of nanocrystalline BaTiO3 and their optical properties

NASA Astrophysics Data System (ADS)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Thermal conductivity in nanocrystalline-SiC/C superlattices

DOE PAGES

Habermehl, S.; Serrano, J. R.

2015-11-17

We reported the formation of thin film superlattices consisting of alternating layers of nitrogen-doped SiC (SiC:N) and C. Periodically terminating the SiC:N surface with a graphitic C boundary layer and controlling the SiC:N/C thickness ratio yield nanocrystalline SiC grains ranging in size from 365 to 23 nm. Frequency domain thermo-reflectance is employed to determine the thermal conductivity, which is found to vary from 35.5 W m -1 K -1 for monolithic undoped α-SiC films to 1.6 W m -1 K -1 for a SiC:N/C superlattice with a 47 nm period and a SiC:N/C thickness ratio of 11. A series conductancemore » model is employed to explain the dependence of the thermal conductivity on the superlatticestructure. Our results indicate that the thermal conductivity is more dependent on the SiC:N/C thickness ratio than the SiC:N grain size, indicative of strong boundary layerphonon scattering.« less

Distinctive glial and neuronal interfacing on nanocrystalline diamond.

PubMed

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth.

Distinctive Glial and Neuronal Interfacing on Nanocrystalline Diamond

PubMed Central

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth. PMID:24664111

Microarray of neuroblastoma cells on the selectively functionalized nanocrystalline diamond thin film surface

NASA Astrophysics Data System (ADS)

Park, Young-Sang; Son, Hyeong-Guk; Kim, Dae-Hoon; Oh, Hong-Gi; Lee, Da-Som; Kim, Min-Hye; Lim, Ki-Moo; Song, Kwang-Soup

2016-01-01

Nanocrystalline diamond (NCD) film surfaces were modified with fluorine or oxygen by plasma treatment in an O2 or C3F8 gas environment in order to induce wettability. The oxygenated-NCD (O-NCD) film surface was hydrophilic and the fluorinated-NCD (F-NCD) surface was hydrophobic. The efficiency of early cell adhesion, which is dependent on the wettability of the cell culture plate and necessary for the growth and proliferation of cells, was 89.62 ± 3.92% on the O-NCD film and 7.78 ± 0.77% on the F-NCD film surface after 3 h of cell culture. The wettability of the NCD film surface was artificially modified using a metal mask and plasma treatment to fabricate a micro-pattern. Four types of micro-patterns were fabricated (line, circle, mesh, and word) on the NCD film surface. We precisely arrayed the neuroblastoma cells on the micro-patterned NCD film surfaces by controlling the surface wettability and cell seeding density. The neuroblastoma cells adhered and proliferated along the O-NCD film surface.

Extreme creep resistance in a microstructurally stable nanocrystalline alloy

NASA Astrophysics Data System (ADS)

Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

2016-09-01

Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

Luminescence and related properties of nanocrystalline porous silicon

NASA Astrophysics Data System (ADS)

Koshida, N.

This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

Gigacycle fatigue behavior by ultrasonic nanocrystalline surface modification.

PubMed

Ahn, D G; Amanov, A; Cho, I S; Shin, K S; Pyoun, Y S; Lee, C S; Park, I G

2012-07-01

Nanocrystalline surface layer up to 84 microm in thick is produced on a specimen made of Al6061-T6 alloy by means of surface treatment called ultrasonic nanocrystalline surface modification (UNSM) technique. The refined grain size is produced in the top-layer and it is increased with increasing depth from the top surface. Vickers microhardness measurement for each nanocrystalline surface layer is performed and measurement results showed that the microhardness is increased from 116 HV up to 150 HV, respectively. In this study, fatigue behavior of Al6061-T6 alloy was studied up to 10(7)-10(9) cycles by using a newly developed ultrasonic fatigue testing (UFT) rig. The fatigue results of the UNSM-treated Al6061-T6 alloy specimens were compared with those of the untreated specimens. The microstructure of the untreated and UNSM-treated specimens was characterized by means of scanning electron microscopey (SEM) and transmission electron microscopey (TEM).

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach.

PubMed

Nath, Soumav; Biswas, Ashik; Kour, Prachi P; Sarma, Loka S; Sur, Ujjal Kumar; Ankamwar, Balaprasad G

2018-08-01

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

Swift heavy ion induced topography changes of Tin oxide thin films

NASA Astrophysics Data System (ADS)

Jaiswal, Manoj K.; Kumar, Avesh; Kanjilal, D.; Mohanty, T.

2012-12-01

Monodisperse tin oxide nanocrystalline thin films are grown on silicon substrates by electron beam evaporation method followed by 100 MeV silver ion bombardment with varying ion fluence from 5 × 1011 ions cm-2 to 1 × 1013 ions cm-2 at constant ion flux. Enhancement of crystallinity of thin films with fluence is observed from glancing angle X-ray diffraction studies. Morphological studies by atomic force microscopy reveal the changes in grain size from 25 nm to 44 nm with variation in ion fluence. The effect of initial surface roughness and adatom mobility on topography is reported. In this work correlation between ion beam induced defect concentration with topography and grain size distribution is emphasized.

Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

2014-11-01

This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

Biologically inspired rosette nanotubes and nanocrystalline hydroxyapatite hydrogel nanocomposites as improved bone substitutes

NASA Astrophysics Data System (ADS)

Zhang, Lijie; Rodriguez, Jose; Raez, Jose; Myles, Andrew J.; Fenniri, Hicham; Webster, Thomas J.

2009-04-01

Today, bone diseases such as bone fractures, osteoporosis and bone cancer represent a common and significant public health problem. The design of biomimetic bone tissue engineering materials that could restore and improve damaged bone tissues provides exciting opportunities to solve the numerous problems associated with traditional orthopedic implants. Therefore, the objective of this in vitro study was to create a biomimetic orthopedic hydrogel nanocomposite based on the self-assembly properties of helical rosette nanotubes (HRNs), the osteoconductive properties of nanocrystalline hydroxyapatite (HA), and the biocompatible properties of hydrogels (specifically, poly(2-hydroxyethyl methacrylate), pHEMA). HRNs are self-assembled nanomaterials that are formed from synthetic DNA base analogs in water to mimic the helical nanostructure of collagen in bone. In this study, different geometries of nanocrystalline HA were controlled by either hydrothermal or sintering methods. 2 and 10 wt% nanocrystalline HA particles were well dispersed into HRN hydrogels using ultrasonication. The nanocrystalline HA and nanocrystalline HA/HRN hydrogels were characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical testing studies revealed that the well dispersed nanocrystalline HA in HRN hydrogels possessed improved mechanical properties compared to hydrogel controls. In addition, the results of this study provided the first evidence that the combination of either 2 or 10 wt% nanocrystalline HA and 0.01 mg ml-1 HRNs in hydrogels greatly increased osteoblast (bone-forming cell) adhesion up to 236% compared to hydrogel controls. Moreover, this study showed that HRNs stimulated HA nucleation and mineralization along their main axis in a way that is very reminiscent of the HA/collagen assembly pattern in natural bone. In summary, the presently observed excellent properties of the biomimetic nanocrystalline HA/HRN hydrogel composites

Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

NASA Astrophysics Data System (ADS)

Huseynov, Elchin M.

2018-01-01

It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

Molecular level energy and electron transfer processes at nanocrystalline titanium dioxide interfaces

NASA Astrophysics Data System (ADS)

Farzad, Fereshteh

This thesis describes photo-induced molecular electron and energy transfer processes occurring at nanocrystalline semiconductor interfaces. The Introductory Chapter provides background and describes how these materials may be useful for solar energy conversion. In Chapter 2, results describing excitation of Ru(deeb)(bpy)2 2+, bis(2,2'-bipyridine)(2,2'-bipyridine-4,4 '-diethylester)ruthenium(II) hexafluorophosphate, bound to nanocrystalline TiO2 thin films, immersed in an acetonitrile bath are presented. The data indicates that light excitation forms predominately long-lived metal-to-ligand charge-transfer, MLCT, excited states under these conditions. Modeling of the data as a function of irradiance has been accomplished assuming parallel unimolecular and bimolecular excited state deactivation processes. The quantum yield for excited state formation depends on the excitation irradiance, consistent with triplet-triplet annihilation processes that occur with k > 1 x 108 s-1. Chapter 3 extends the work described in Chapter 2 to LiClO4 acetonitrile solutions. Li+ addition results in a red shift in the MLCT absorption and photoluminescence, PL, and a concentration dependent quenching of the PL intensity on TiO2. The Li+ induced spectroscopic changes were found to be reversible by varying the electrolyte composition. A second-order kinetic model quantified charge recombination transients. A model is proposed wherein Li+ ion adsorption stabilizes TiO2 acceptor states resulting in energetically more favorable interfacial electron transfer. The photophysical and photoelectrochemical properties of porous nanocrystalline anatase TiO2 electrodes modified with Ru(deeb)(bpy)2 2+, Os(deeb)(bpy)22+, and mixtures of both are described in Chapters 4 and 5. In regenerative solar cells with 0.5 M LiI/0.05 M I2 acetonitrile electrolyte, both compounds efficiently inject electrons into TiO2 producing monochromatic incident photon-to-current efficiencies (IPCE), IPCE (460 nm) = 0.70 + 0

Anomalous behavior of B{sub 1g} mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gautam, Subodh K., E-mail: subodhkgtm@gmail.com, E-mail: fouran@gmail.com; Ojha, S.; Singh, Fouran, E-mail: subodhkgtm@gmail.com, E-mail: fouran@gmail.com

2015-12-15

The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO{sub 2} lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb{sup +5} in the TiO{sub 2} lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Ramanmore » (MR) spectra of films with small size crystallites shows stiffening of about 4 cm{sup −1} for the E{sub g(1)} mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B{sub 1g} mode exhibits a large anomalous softening of 20 cm{sup −1} with asymmetrical broadening; which was not reported for the case of pure TiO{sub 2} crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb{sup 5+} doping induced reduction of Ti{sup 4+} ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.« less

Physical properties of nanostructured strontium oxide thin film grown by chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Ahmad, Farhan; Belkhedkar, M. R.; Salodkar, R. V.

2018-05-01

Nanostructured SrO thin film of thickness 139 nm was deposited by chemical bath deposition technique onto glass substrates using SrCl2.6H2O and NaOH as cationic and anionic precursors without complexing agents. The X-ray diffraction studies revealed that, SrO thin film is nanocrystalline in nature with cubic structure. The surface morphology of the SrO film was investigated by means of field emission scanning electron microscopy. The optical studies showed that SrO film exhibits direct as well as indirect optical band gap energy. The electrical resistivity and activation energy of SrO thin film is found to be of the order of 106 Ω cm and 0.58eV respectively.

Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

NASA Astrophysics Data System (ADS)

Kalaivani, A.; Senguttuvan, G.; Kannan, R.

2018-03-01

Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

Direct Coating of Nanocrystalline Diamond on Steel

NASA Astrophysics Data System (ADS)

Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

2012-09-01

Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

NASA Astrophysics Data System (ADS)

Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

2018-05-01

CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

Bulk Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

DTIC Science & Technology

2014-05-13

nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and...the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta...approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are

Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Z.; Chen, Z.; Zhou, D.

1998-10-01

Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

Deposition of thin Si and Ge films by ballistic hot electron reduction in a solution-dripping mode and its application to the growth of thin SiGe films

NASA Astrophysics Data System (ADS)

Suda, Ryutaro; Yagi, Mamiko; Kojima, Akira; Mentek, Romain; Mori, Nobuya; Shirakashi, Jun-ichi; Koshida, Nobuyoshi

2015-04-01

To enhance the usefulness of ballistic hot electron injection into solutions for depositing thin group-IV films, a dripping scheme is proposed. A very small amount of SiCl4 or GeCl4 solution was dripped onto the surface of a nanocrystalline Si (nc-Si) electron emitter, and then the emitter is driven without using any counter electrodes. It is shown that thin Si and Ge films are deposited onto the emitting surface. Spectroscopic surface and compositional analyses showed no extrinsic carbon contaminations in deposited thin films, in contrast to the results of a previous study using the dipping scheme. The availability of this technique for depositing thin SiGe films is also demonstrated using a mixture SiCl4+GeCl4 solution. Ballistic hot electrons injected into solutions with appropriate kinetic energies promote preferential reduction of target ions with no by-products leading to nuclei formation for the thin film growth. Specific advantageous features of this clean, room-temperature, and power-effective process is discussed in comparison with the conventional dry and wet processes.

Defect studies of thin ZnO films prepared by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Vlček, M.; Čížek, J.; Procházka, I.; Novotný, M.; Bulíř, J.; Lančok, J.; Anwand, W.; Brauer, G.; Mosnier, J.-P.

2014-04-01

Thin ZnO films were grown by pulsed laser deposition on four different substrates: sapphire (0 0 0 1), MgO (1 0 0), fused silica and nanocrystalline synthetic diamond. Defect studies by slow positron implantation spectroscopy (SPIS) revealed significantly higher concentration of defects in the studied films when compared to a bulk ZnO single crystal. The concentration of defects in the films deposited on single crystal sapphire and MgO substrates is higher than in the films deposited on amorphous fused silica substrate and nanocrystalline synthetic diamond. Furthermore, the effect of deposition temperature on film quality was investigated in ZnO films deposited on synthetic diamond substrates. Defect studies performed by SPIS revealed that the concentration of defects firstly decreases with increasing deposition temperature, but at too high deposition temperatures it increases again. The lowest concentration of defects was found in the film deposited at 450° C.

Synthesis and characterization of spin-coated ZnS thin films

NASA Astrophysics Data System (ADS)

Zaman, M. Burhanuz; Chandel, Tarun; Dehury, Kshetramohan; Rajaram, P.

2018-05-01

In this paper, we report synthesis of ZnS thin films using a sol-gel method. A unique aprotic solvent, dimethlysulphoxide (DMSO) has been used to obtain a homogeneous ZnS gel. Zinc acetate and thiourea were used as the precursor sources for Zn and S, respectively, to deposit nanocrystalline ZnS thin films. Optical, structural and morphological properties of the films were studied. Optical studies reveal high transmittance of the samples over the entire visible region. The energy band gap (Eg) for the ZnS thin films is found to be about 3.6 eV which matches with that of bulk ZnS. The interference fringes in transmissions spectrum show the high quality of synthesized samples. Strong photoluminescence peak in the UV region makes the films suitable for optoelectronic applications. X-ray diffraction studies reveal that sol-gel derived ZnS thin films are polycrystalline in nature with hexagonal structure. SEM studies confirmed that the ZnS films show smooth and uniform grains morphology having size in 20-25 nm range. The EDAX studies confirmed that the films are nearly stoichiometric.

Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

NASA Astrophysics Data System (ADS)

Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

2016-10-01

In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

"Bulk" Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

NASA Astrophysics Data System (ADS)

Tschopp, M. A.; Murdoch, H. A.; Kecskes, L. J.; Darling, K. A.

2014-06-01

It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

Enhanced magneto-optical Kerr effect in rare earth substituted nanostructured cobalt ferrite thin film prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Avazpour, L.; Toroghinejad, M. R.; Shokrollahi, H.

2016-11-01

A series of rare-earth (RE)-doped nanocrystalline Cox RE(1-x) Fe2O4 (x = 0, 0.1, 0.2 and RE: Nd, Eu) thin films were prepared on silicon substrates by a sol-gel process, and the influences of different RE3+ ions on the microstructure, magnetism and polar magneto-optical Kerr effect of the deposited films were investigated. Also this research presents the optimization process of cobalt ferrite thin films deposited via spin coating, by studying their structural and morphological properties at different thicknesses (200, 350 nm) and various heat treatment temperatures 300-850 °C. Nanoparticulate polycrystalline thin film were formed with heat treatment above 400 °C but proper magnetic properties due to well crystallization of the film were achieved at about 650 °C. AFM results indicated that the deposited thin films were crack-free exhibiting a dense nanogranular structure. The root-mean square (RMS) roughness of the thin films was in the range of 0.2-3.2 nm. The results revealed that both of the magnetism and magneto optical Kerr (MOKE) spectra of Cox RE(1-x) Fe2O4 films could be mediated by doping with various RE ions. The Curie temperature of substituted samples was lower than pristine cobalt ferrite thin films. In MOKE spectra both dominant peaks were blue shifted with addition of RE ions. For low concentration dopant the inter-valence charge transfer related rotation was enhanced and for higher concentration dopant the crystal field rotation peak was enhanced. The MOKE enhancement for Eu3+ substituted samples was more than Nd3+ doped cobalt ferrite films. The enhanced MOKEs in nanocrystalline thin films might promise their applications for magneto-optical sensors in adopted wavelengths.

Confining metal-halide perovskites in nanoporous thin films

PubMed Central

Demchyshyn, Stepan; Roemer, Janina Melanie; Groiß, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Böhm, Anton; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus Clark; Sariciftci, Niyazi Serdar; Nickel, Bert; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

2017-01-01

Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability because the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy x-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next-generation photonic devices. PMID:28798959

Growth characteristics of nanocrystalline silicon films fabricated by using chlorinated precursors at low temperatures.

PubMed

Huang, Rui; Ding, Honglin; Song, Jie; Guo, Yanqing; Wang, Xiang; Lin, Xuanying

2010-11-01

We employed plasma enhanced chemical vapor deposition technique to fabricate nanocrystalline Si films at a low temperature of 250 degrees C by using SiCl4 and H2 as source gases. The evolution of microstructure of the films with deposition periods shows that nanocrystalline Si can be directly grown on amorphous substrate at the initial growth process, which is in contrast to the growth behavior observed in the SiH4/H2 system. Furthermore, it is interesting to find that the area density of nanocrystalline Si as well as grain size can be controlled by modulating the concentration of SiCl4. By decreasing the SiCl4 concentration, the area density of nanocrystalline Si can be enhanced up to 10(11) cm(-2), while the grain size is shown to decrease down to 10 nm. It is suggested that Cl plays an important role in the low-temperature growth of nanocrystalline Si.

Grain Size Threshold for Enhanced Irradiation Resistance in Nanocrystalline and Ultrafine Tungsten

DOE PAGES

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme; ...

2017-02-21

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

PubMed

Yong, Seok; Park, Ji Chan; Lee, Ho-Tae; Yang, Jung-Il; Hong, SungJun; Jung, Heon; Chun, Dong Hyun

2016-02-01

Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

Controlling electrostatic charging of nanocrystalline diamond at nanoscale.

PubMed

Verveniotis, Elisseos; Kromka, Alexander; Rezek, Bohuslav

2013-06-11

Constant electrical current in the range of -1 to -200 pA is applied by an atomic force microscope (AFM) in contact mode regime to induce and study local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films. The NCD films are deposited on silicon in 70 nm thickness and with 60% relative sp(2) phase content. Charging current is monitored by conductive AFM. Electric potential contrast induced by the current is evaluated by Kelvin force microscopy (KFM). KFM shows well-defined, homogeneous, and reproducible microscopic patterns that are not influenced by inherent tip-surface junction fluctuations during the charging process. The charged patterns are persistent for at least 72 h due to charge trapping inside the NCD film. The current-induced charging also clearly reveals field-induced detrapping at current amplitudes >-50 pA and tip instability at >-150 pA, both of which limit the achievable potential contrast. In addition, we show that the field also determines the range of electronic states that can trap the charge. We present a model and discuss implications for control of the nanoscale charging process.

Nanocrystalline copper films are never flat.

PubMed

Zhang, Xiaopu; Han, Jian; Plombon, John J; Sutton, Adrian P; Srolovitz, David J; Boland, John J

2017-07-28

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

NASA Astrophysics Data System (ADS)

Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

2017-12-01

The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

NASA Astrophysics Data System (ADS)

Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

2018-01-01

The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Spectroscopic ellipsometry analysis of nanocrystalline silicon carbide obtained at low temperature

NASA Astrophysics Data System (ADS)

Kerdiles, S.; Madelon, R.; Rizk, R.

2001-12-01

Thin films of silicon carbide obtained by hydrogen-reactive magnetron sputtering with various substrate temperatures TS (100-600 °C) were analysed by transmission electron microscopy (TEM) and spectroscopic ellipsometry (SE). The TEM images show evidence of the growth of hydrogenated nanocrystalline silicon carbide (nc-SiC:H) deposited at TS as low as 300 °C, with an average grain size of 4-5 nm. The SE spectra were reproduced by using the Forouhi-Bloomer model and assuming a 7 nm thick overlayer with a void fraction of 45%. The observed increase of the refractive index with TS is assigned to the improvement of both crystallinity and compactness of the layer. The expected increase of the optical gap seems to be offset by the drop of hydrogen content, leaving the gap unchanged. The fabrication and characteristics of nc-SiC:H/c-Si diode are finally described and the data indicate a good rectifying behaviour, together with a low leakage current.

Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

PubMed

Dasan, Y K; Bhat, A H; Ahmad, Faiz

2017-02-10

The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis and Phase Stability of Scandia, Gadolinia, and Ytterbia Co-doped Zirconia for Thermal Barrier Coating Application

NASA Astrophysics Data System (ADS)

Li, Qi-Lian; Cui, Xiang-Zhong; Li, Shu-Qing; Yang, Wei-Hua; Wang, Chun; Cao, Qian

2015-01-01

Scandia, gadolinia, and ytterbia co-doped zirconia (SGYZ) ceramic powder was synthesized by chemical co-precipitation and calcination processes for application in thermal barrier coatings to promote the durability of gas turbines. The ceramic powder was agglomerated and sintered at 1150 °C for 2 h, and the powder exhibited good flowability and apparent density to be suitable for plasma spraying process. The microstructure, morphology and phase stability of the powder and plasma-sprayed SGYZ coatings were analyzed by means of scanning electron microscope and x-ray diffraction. Thermal conductivity of plasma-sprayed SGYZ coatings was measured. The results indicated that the SGYZ ceramic powder and the coating exhibit excellent stability to retain single non-transformable tetragonal zirconia even after high temperature (1400 °C) exposure for 500 h and do not undergo a tetragonal-to-monoclinic phase transition upon cooling. Furthermore, the plasma-sprayed SGYZ coating also exhibits lower thermal conductivity than yttria stabilized zirconia coating currently used in gas turbine engine industry. SGYZ can be explored as a candidate material of ultra-high temperature thermal barrier coating for advanced gas turbine engines.

Framework Stability of Nanocrystalline NaY in Aqueous Solution at Varying pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petushkov, Anton; Freeman, Jasmine; Larsen, Sarah C.

Nanocrystalline zeolites (with crystal sizes of less than 50 nm) are versatile, porous nanomaterials with potential applications in a broad range of areas including bifunctional catalysis, drug delivery, environmental protection, and sensing, to name a few. The characterization of the properties of nanocrystalline zeolites on a fundamental level is critical to the realization of these innovative applications. Nanocrystalline zeolites have unique surface chemistry that is distinct from conventional microcrystalline zeolite materials and that will result in novel applications. In the proposed work, magnetic resonance techniques (solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)) will be used tomore » elucidate the structure and reactivity of nanocrystalline zeolites and to motivate bifunctional applications. Density functional theory (DFT) calculations will enhance data interpretation through chemical shift, quadrupole coupling constant, g-value and hyperfine calculations.« less

Properties of Resistive Hydrogen Sensors as a Function of Additives of 3 D-Metals Introduced in the Volume of Thin Nanocrystalline SnO2 Films

NASA Astrophysics Data System (ADS)

Sevast'yanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Sergeichenko, N. V.; Chernikov, E. V.; Almaev, A. V.; Kushnarev, B. O.

2017-11-01

Analysis of the results of studying electrical and gas sensitive characteristics of the molecular hydrogen sensors based on thin nanocrystalline SnO2 films coated with dispersed Au layers and containing Au+Ni and Au+Co impurities in the bulk showed that the characteristics of these sensors are more stable under the prolonged exposure to hydrogen in comparison with Au/SnO2:Sb, Au films modified only with gold. It has been found that introduction of the nickel and cobalt additives increases the band bending at the grain boundaries of tin dioxide already in freshly prepared samples, which indicates an increase in the density Ni of the chemisorbed oxygen. It is important that during testing, the band bending eφs at the grain boundaries of tin dioxide additionally slightly increases. It can be assumed that during crystallization of films under thermal annealing, the 3d-metal atoms in the SnO2 volume partially segregate on the surface of microcrystals and form bonds with lattice oxygen, the superstoichiometric tin atoms are formed, and the density Ni increases. If the bonds of oxygen with nickel and cobalt are stronger than those with tin, then, under the prolonged tests, atomic hydrogen will be oxidized not by lattice oxygen, but mainly by the chemisorbed one. In this case, stability of the sensors' characteristics increases.

Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2014-11-01

1 ASETSDefense 2014 Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative Ruben A. Prado, CEF...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative...coatings as a Hard Chrome (EHC) electroplating alternative for DoD manufacturing and repair. – Fully define deposition parameters and properties

Nanocrystalline ferroelectric BaTiO3/Pt/fused silica for implants synthetized by pulsed laser deposition method

NASA Astrophysics Data System (ADS)

Jelínek, Miroslav; Drahokoupil, Jan; Jurek, Karel; Kocourek, Tomáš; Vaněk, Přemysl

2017-09-01

The thin-films of BaTiO3 (BTO)/Pt were prepared to test their potential as coatings for titanium-alloy implants. The nanocrystalline BTO/Pt bi-layers were successfully synthesized using fused silica as substrates. The bi-layers were prepared using KrF excimer laser ablation at substrate temperatures (Ts) ranging from 650 °C to 750 °C. The microstructure and composition of the deposits were investigated by scanning electron microscope, x-ray diffraction and wavelength dispersive x-ray spectroscopy methods. The electrical characterization of the Pt/BTO/Pt capacitors indicated ferroelectric-type response in BTO films containing (40-140) nm-sized grains. The technology, microstructure, and functional response of the layers are presented in detail.

Model for temperature-dependent magnetization of nanocrystalline materials

NASA Astrophysics Data System (ADS)

Bian, Q.; Niewczas, M.

2015-01-01

A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

Structural, thermal, spectroscopic, and spectral dispersion studies of nanocrystalline methyl red thin films

NASA Astrophysics Data System (ADS)

Makhlouf, Mohamed M.; El-Denglawey, Adel

2018-04-01

Methyl red (MR) powder is polycrystalline structure as-purchased. The uniform, homogeneous and no cracks nano MR thin films are successfully prepared using thermal evaporation technique. The structural investigation for the pristine, annealed and UV irradiated MR films shows nanorods spread in amorphous medium. The part of as-prepared films exposed to UV light irradiation of wavelength 254 nm and intensity of 2000 µW/cm2 for 1 h, while the other part of films was treated by the annealing temperature at 178 °C for 1 h. The optical properties of MR thin films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the spectral range 200-2000 nm. The optical constants, dispersion parameters, and energy loss and dielectric functions of MR thin films were calculated and showed remarkable dependence on UV irradiation and annealing temperature upon the films of MR. The dependence of absorption coefficient on the photon energy were analyzed and the results showed that MR films undergo direct allowed optical transition for pristine, annealed and irradiated MR films.

Multifunctionality of nanocrystalline lanthanum ferrite

NASA Astrophysics Data System (ADS)

Rai, Atma; Thakur, Awalendra K.

2016-05-01

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

Multifunctionality of nanocrystalline lanthanum ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

2016-05-06

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

Nanocrystalline diamond thin films on titanium-6 aluminum-4 vanadium alloy temporomandibular joint prosthesis simulants by microwave plasma chemical vapor deposition

NASA Astrophysics Data System (ADS)

Fries, Marc Douglas

A course of research has been performed to assess the suitability of nanocrystal-line diamond (NCD) films on Ti-6Al-4V alloy as wear-resistant coatings in biomedical implant use. A series of temporomandibular (TMJ) joint condyle simulants were polished and acid-passivated as per ASTM F86 standard for surface preparation of implants. A 3-mum-thick coating of NCD film was deposited by microwave plasma chemical vapor deposition (MPCVD) over the hemispherical articulation surfaces of the simulants. Plasma chemistry conditions were measured and monitored by optical emission spectroscopy (OES), using hydrogen as a relative standard. The films consist of diamond grains around 20 nm in diameter embedded in an amorphous carbon matrix, free of any detectable film stress gradient. Hardness averages 65 GPa and modulus measures 600 GPa at a depth of 250 nm into the film surface. A diffuse film/substrate boundary produces a minimal film adhesion toughness (GammaC) of 158 J/m2. The mean RMS roughness is 14.6 +/- 4.2 nm, with an average peak roughness of 82.6 +/- 65.9 nm. Examination of the surface morphology reveals a porous, dendritic surface. Wear testing resulted in two failed condylar coatings out of three tests. No macroscopic delamination was found on any sample, but micron-scale film pieces broke away, exposing the substrate. Electrochemical corrosion testing shows a seven-fold reduction in corrosion rate with the application of an NCD coating as opposed to polished, passivated Ti-6Al-4V, producing a corrosion rate comparable to wrought Co-Cr-Mo. In vivo biocompatibility testing indicates that implanted NCD films did not elicit an immune response in the rabbit model, and osteointegration was apparent for both compact and trabecular bone on both NCD film and bare Ti-6Al-4V. Overall, NCD thin film material is reasonably smooth, biocompatible, and very well adhered. Wear testing indicates that this material is unacceptable for use in demanding TMJ applications without

Nanocarbon Allotropes-Graphene and Nanocrystalline Diamond-Promote Cell Proliferation.

PubMed

Verdanova, Martina; Rezek, Bohuslav; Broz, Antonin; Ukraintsev, Egor; Babchenko, Oleg; Artemenko, Anna; Izak, Tibor; Kromka, Alexander; Kalbac, Martin; Hubalek Kalbacova, Marie

2016-05-01

Two profoundly different carbon allotropes - nanocrystalline diamond and graphene - are of considerable interest from the viewpoint of a wide range of biomedical applications including implant coating, drug and gene delivery, cancer therapy, and biosensing. Osteoblast adhesion and proliferation on nanocrystalline diamond and graphene are compared under various conditions such as differences in wettability, topography, and the presence or absence of protein interlayers between cells and the substrate. The materials are characterized in detail by means of scanning electron microscopy, atomic force microscopy, photoelectron spectroscopy, Raman spectroscopy, and contact angle measurements. In vitro experiments have revealed a significantly higher degree of cell proliferation on graphene than on nanocrystalline diamond and a tissue culture polystyrene control material. Proliferation is promoted, in particular, by hydrophobic graphene with a large number of nanoscale wrinkles independent of the presence of a protein interlayer, i.e., substrate fouling is not a problematic issue in this respect. Nanowrinkled hydrophobic graphene, thus, exhibits superior characteristics for those biomedical applications where high cell proliferation is required under differing conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of voids distribution on the deformation behavior of nanocrystalline palladium

NASA Astrophysics Data System (ADS)

Bachurin, D. V.

2018-07-01

Uniaxial deformation of three-dimensional nanocrystalline palladium containing porosity in the form of voids was investigated by means of molecular dynamics method. Simulations were performed at temperature of 300 K and at a constant strain rate of 108s-1. Two cases of voids distribution were considered: random and at triple or quadrupole junctions. It has been revealed that both the voids distribution and subsequent annealing at elevated temperature influence the deformation behavior of nanocrystalline palladium. In particular, the presence of voids at grain junctions results in a reduction of the Young's modulus and more pronounced softening effect during plastic deformation. The subsequent annealing evokes shrinkage of voids and strengthening effect. Contribution of grain boundary accommodation processes into both elastic and plastic deformation of nanocrystalline materials is discussed.

Electrode characteristics of nanocrystalline (Zr, Ti)(V, Cr, Ni) 2.41 compound

NASA Astrophysics Data System (ADS)

Majchrzycki, W.; Jurczyk, M.

The electrochemical properties of nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 alloy, which has the hexagonal C14 type structure, have been investigated. This material has been prepared using mechanical alloying (MA) followed by annealing. The amorphous phase forms directly from the starting mixture of the elements, without other phase formation. Heating the MA samples at 1070 K for 0.5 h resulted in the creation of ordered alloy. This alloy was used as negative electrode for Ni-MH x battery. The electrochemical results show very little difference between the nanocrystalline and polycrystalline powders, as compared with the substantial difference between these and the amorphous powder. In the annealed nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 powders discharging capacities up to 150 mA h g -1 (at 160 mA g -1 discharging current) have been measured. The properties of nanocrystalline electrode were attributed to the structural characteristics of the compound caused by mechanical alloying.

Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films

PubMed Central

Mahadeva, Sreekanth K.; Fan, Jincheng; Biswas, Anis; Sreelatha, K.S.; Belova, Lyubov; Rao, K.V.

2013-01-01

We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas atmosphere of (N2 + O2) are found to be X-ray amorphous. All these films obtained with oxygen partial pressure (PO2) ~10% to 80% while maintaining the same total pressure of the working gas are found to be ferromagnetic at room temperature. The room temperature saturation magnetization (MS) value of 2.68 emu/cm3 obtained for the MgO film deposited in PO2 of 10% increases to 9.62 emu/cm3 for film deposited at PO2 of 40%. However, the MS values decrease steadily for further increase of oxygen partial pressure during deposition. On thermal annealing at temperatures in the range 600 to 800 °C, the films become nanocrystalline and as the crystallite size grows with longer annealing times and higher temperature, MS decreases. Our study clearly points out that it is possible to tailor the magnetic properties of thin films of MgO. The room temperature ferromagnetism in MgO films is attributed to the presence of Mg cation vacancies. PMID:28348346

Remarkably High Mobility Thin-Film Transistor on Flexible Substrate by Novel Passivation Material.

PubMed

Shih, Cheng Wei; Chin, Albert

2017-04-25

High mobility thin-film transistor (TFT) is crucial for future high resolution and fast response flexible display. Remarkably high performance TFT, made at room temperature on flexible substrate, is achieved with record high field-effect mobility (μ FE ) of 345 cm 2 /Vs, small sub-threshold slope (SS) of 103 mV/dec, high on-current/off-current (I ON /I OFF ) of 7 × 10 6 , and a low drain-voltage (V D ) of 2 V for low power operation. The achieved mobility is the best reported data among flexible electronic devices, which is reached by novel HfLaO passivation material on nano-crystalline zinc-oxide (ZnO) TFT to improve both I ON and I OFF . From X-ray photoelectron spectroscopy (XPS) analysis, the non-passivated device has high OH-bonding intensity in nano-crystalline ZnO, which damage the crystallinity, create charged scattering centers, and form potential barriers to degrade mobility.

Nanocrystalline High-Entropy Alloys: A New Paradigm in High-Temperature Strength and Stability.

PubMed

Zou, Yu; Wheeler, Jeffrey M; Ma, Huan; Okle, Philipp; Spolenak, Ralph

2017-03-08

Metals with nanometer-scale grains or nanocrystalline metals exhibit high strengths at ambient conditions, yet their strengths substantially decrease with increasing temperature, rendering them unsuitable for usage at high temperatures. Here, we show that a nanocrystalline high-entropy alloy (HEA) retains an extraordinarily high yield strength over 5 GPa up to 600 °C, 1 order of magnitude higher than that of its coarse-grained form and 5 times higher than that of its single-crystalline equivalent. As a result, such nanostructured HEAs reveal strengthening figures of merit-normalized strength by the shear modulus above 1/50 and strength-to-density ratios above 0.4 MJ/kg, which are substantially higher than any previously reported values for nanocrystalline metals in the same homologous temperature range, as well as low strain-rate sensitivity of ∼0.005. Nanocrystalline HEAs with these properties represent a new class of nanomaterials for high-stress and high-temperature applications in aerospace, civilian infrastructure, and energy sectors.

Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

NASA Astrophysics Data System (ADS)

Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

2014-09-01

The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

Functionalized coatings by cold spray: An in vitro study of micro- and nanocrystalline hydroxyapatite compared to porous titanium.

PubMed

Vilardell, A M; Cinca, N; Garcia-Giralt, N; Dosta, S; Cano, I G; Nogués, X; Guilemany, J M

2018-06-01

Three different surface treatments on a Ti6Al4V alloy have been in vitro tested for possible application in cementless joint prosthesis. All of them involve the novelty of using the Cold Spray technology for their deposition: (i) an as-sprayed highly rough titanium and, followed by the deposition of a thin hydroxyapatite layer with (ii) microcrystalline or (iii) nanocrystalline structure. Primary human osteoblasts were extracted from knee and seeded onto the three different surfaces. Cell viability was tested by MTS and LIVE/DEAD assays, cell differentiation by alkaline phosphatase (ALP) quantification and cell morphology by Phalloidin staining. All tests were carried out at 1, 7 and 14 days of cell culture. Different cell morphologies between titanium and hydroxyapatite surfaces were exhibited. At 1 day of cell culture, cells on the titanium coating were spread and flattened, expanding the filopodia actin filaments in all directions, while cells on the hydroxyapatite coatings showed round like-shape morphology due to slower attachment. Higher cell viability was detected at all times of cell culture on titanium coating due to a better attachment at 1 day. However, from 7 days of cell culture, cells on hydroxyapatite showed good attachment onto surfaces and highly increased their proliferation, mostly on nanocrystalline, achieving similar cell viability levels than titanium coatings. ALP levels were significantly higher in titanium, in part, because of greatest cell number. Overall, the best cell functional results were obtained on titanium coatings whereas microcrystalline hydroxyapatite presented the worst cellular parameters. However, results indicate that nanocrystalline hydroxyapatite coatings may achieve promising results for the faster cell proliferation once cells are attached on the surface. Copyright © 2018 Elsevier B.V. All rights reserved.

Production of nanocrystalline metal powders via combustion reaction synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frye, John G.; Weil, Kenneth Scott; Lavender, Curt A.

Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

Grain growth in nanocrystalline iron and Fe-Al alloys

NASA Astrophysics Data System (ADS)

Mirzadeh, Hamed; Zomorodian, Amir

2010-02-01

The effects of the annealing temperature and time, cryomilling in liquid nitrogen, and the addition of aluminum powder on the thermal stability and grain growth behavior of nanocrystalline iron were modeled using the Artificial Neural Network (ANN) technique. The developed model can be used as a guide for the quantification of the grain growth by considering the effects of annealing temperature and time. The model also quantified the effect of Al on the thermal stability of cryomilled nanocrystalline Fe. The model results showed that the cryomilling of Fe has a tangible effect on the stabilization of the nanostructure.

Boron-Doped Nanocrystalline Diamond Electrodes for Neural Interfaces: In vivo Biocompatibility Evaluation

PubMed Central

Alcaide, María; Taylor, Andrew; Fjorback, Morten; Zachar, Vladimir; Pennisi, Cristian P.

2016-01-01

Boron-doped nanocrystalline diamond (BDD) electrodes have recently attracted attention as materials for neural electrodes due to their superior physical and electrochemical properties, however their biocompatibility remains largely unexplored. In this work, we aim to investigate the in vivo biocompatibility of BDD electrodes in relation to conventional titanium nitride (TiN) electrodes using a rat subcutaneous implantation model. High quality BDD films were synthesized on electrodes intended for use as an implantable neurostimulation device. After implantation for 2 and 4 weeks, tissue sections adjacent to the electrodes were obtained for histological analysis. Both types of implants were contained in a thin fibrous encapsulation layer, the thickness of which decreased with time. Although the level of neovascularization around the implants was similar, BDD electrodes elicited significantly thinner fibrous capsules and a milder inflammatory reaction at both time points. These results suggest that BDD films may constitute an appropriate material to support stable performance of implantable neural electrodes over time. PMID:27013949

Effects of oxide distributed in grain boundaries on microstructure stability of nanocrystalline metals

NASA Astrophysics Data System (ADS)

Zhou, Kai; Li, Hui; Biao Pang, Jin; Wang, Zhu

2013-06-01

Nanocrystalline copper and zinc prepared by high-pressure compaction method have been studied by positron lifetime spectroscopy associated with X-ray diffraction. For nanocrystalline Cu, mean grain sizes of the samples decrease after being annealed at 900 °C and increase during aging at 180 °C, revealing that the atoms exchange between the two regions. The positron lifetime results indicate that the vacancy clusters formed in the annealing process are unstable and decomposed at the aging time below 6 hours. In addition, the partially oxidized surfaces of the nanoparticles hinder the grain growth during the ageing at 180 °C, and the vacancy clusters inside the disorder regions which are related to Cu2O need longer aging time to decompose. In the case of nanocrystalline Zn, the open volume defect (not larger than divacancy) is dominant according to the high relative intensity for the short positron lifetime (τ1). The oxide (ZnO) inside the grain boundaries has been found having an effect to hinder the decrease of average positron lifetime (τav) during the annealing, which probably indicates that the oxide stabilizes the microstructure of the grain boundaries. For both nanocrystalline copper and zinc, the oxides in grain boundaries enhance the thermal stability of the microstucture, in spite of their different crystal structures. This effect is very important for the nanocrystalline materials using as radiation resistant materials.

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

NASA Astrophysics Data System (ADS)

Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

2016-05-01

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugimura, K.; Miyajima, Y.; Sonehara, M.

2016-05-15

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO{sub 2}) was successfully deposited on the CIP-surface by using hydrolysismore » of TEOS (Si(OC{sub 2}H{sub 5}){sub 4}). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.« less

Ionic Conduction in Nanocrystalline Materials

DTIC Science & Technology

2000-02-10

In the following, we review studies performed films prepared by a polymer precursor process on on stabilized zirconia ceramics with grain sizes alumina ... titania , is reviewed. While it remains too early to make firm conclusions, the following observations are made. Additives which contribute to ion blocking...Keywords: Ionic conductivity; Nanocrystalline; Zirconia; Ceria; Titania ; Defects 1. Introduction tivity by nearly two orders of magnitude [6]. Given the

Investigation of microstructure, micro-mechanical and optical properties of HfTiO{sub 4} thin films prepared by magnetron co-sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazur, Michal, E-mail: michal.mazur@pwr.edu.pl; Wojcieszak, Damian; Domaradzki, Jaroslaw

2015-12-15

Highlights: • HfTiO{sub 4} thin films were deposited by magnetron co-sputtering. • As-prepared and annealed at 800 °C thin films were nanocrystalline. • Optical properties and hardness were investigated in relation to thin films structure. • Hardness was 3-times higher in the case of as-deposited thin films. • HfTiO{sub 4} thin films are suitable for use as optical coatings with protective properties. - Abstract: Titania (TiO{sub 2}) and hafnium oxide (HfO{sub 2}) thin films are in the focus of interest to the microelectronics community from a dozen years. Because of their outstanding properties like, among the others, high stability, highmore » refractive index, high electric permittivity, they found applications in many optical and electronics domains. In this work discussion on the hardness, microstructure and optical properties of as-deposited and annealed HfTiO{sub 4} thin films has been presented. Deposited films were prepared using magnetron co-sputtering method. Performed investigations revealed that as-deposited coatings were nanocrystalline with HfTiO{sub 4} structure. Deposited films were built from crystallites of ca. 4–12 nm in size and after additional annealing an increase in crystallites size up to 16 nm was observed. Micro-mechanical properties, i.e., hardness and elastic modulus were determined using conventional load-controlled nanoindentation testing. the annealed films had 3-times lower hardness as-compared to as-deposited ones (∼9 GPa). Based on optical investigations real and imaginary components of refractive index were calculated, both for as-deposited and annealed thin films. The real refractive index component increased after annealing from 2.03 to 2.16, while extinction coefficient increased by an order from 10{sup −4} to 10{sup −3}. Structure modification was analyzed together with optical energy band-gap, Urbach energy and using Wemple–DiDomenico model.« less

ZrO{sub 2}-ZnO composite thin films for humidity sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velumani, M., E-mail: velumanimohan@gmail.com; Sivacoumar, R.; Alex, Z. C.

2016-05-23

ZrO{sub 2}-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO{sub 2} phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

Isolation of bacterial cellulose nanocrystalline from pineapple peel waste: Optimization of acid concentration in the hydrolysis method

NASA Astrophysics Data System (ADS)

Anwar, Budiman; Rosyid, Nurul Huda; Effendi, Devi Bentia; Nandiyanto, Asep Bayu Dani; Mudzakir, Ahmad; Hidayat, Topik

2016-02-01

Isolation of needle-shaped bacterial cellulose nanocrystalline with a diameter of 16-64 nm, a fiber length of 258-806 nm, and a degree of crystallinity of 64% from pineapple peel waste using an acid hydrolysis process was investigated. Experimental showed that selective concentration of acid played important roles in isolating the bacterial cellulose nanocrystalline from the cellulose source. To achieve the successful isolation of bacterial cellulose nanocrystalline, various acid concentrations were tested. To confirm the effect of acid concentration on the successful isolation process, the reaction conditions were fixed at a temperature of 50°C, a hydrolysis time of 30 minutes, and a bacterial cellulose-to-acid ratio of 1:50. Pineapple peel waste was used as a model for a cellulose source because to the best of our knowledge, there is no report on the use of this raw material for producing bacterial cellulose nanocrystalline. In fact, this material can be used as an alternative for ecofriendly and cost-free cellulose sources. Therefore, understanding in how to isolate bacterial cellulose nanocrystalline from pineapple peel waste has the potential for large-scale production of inexpensive cellulose nanocrystalline.

Improve oxidation resistance at high temperature by nanocrystalline surface layer

NASA Astrophysics Data System (ADS)

Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

2015-08-01

An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying.

PubMed

Tyagi, Beena; Sidhpuria, Kalpesh; Shaik, Basha; Jasra, Raksh Vir

2006-06-01

Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia.

Self-composite comprised of nanocrystalline diamond and a non-diamond component useful for thermoelectric applications

DOEpatents

Gruen, Dieter M.

2012-09-04

One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material. By one approach this non-diamond component comprises an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also preserving the thermal conductivity behavior of the nanocrystalline diamond material.

Self-composite comprised of nanocrystalline diamond and a non-diamond component useful for thermoelectric applications

DOEpatents

Gruen, Dieter M [Downers Grove, IL

2009-08-11

One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material. By one approach this non-diamond component comprises an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also preserving the thermal conductivity behavior of the nanocrystalline diamond material.

Nanocrystalline high-entropy alloy (CoCrFeNiAl 0.3 ) thin-film coating by magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Weibing; Lan, Si; Gao, Libo

High-entropy CoCrFeNiAl0.3 alloy thin films were prepared by magnetron sputtering technique. The thin film surface was very smooth and homogeneous. The synchrotron X-ray experiment confirmed that (111) type of texture existed in the thin film, and the structure was face-centered cubic nanocrystals with a minor content of ordered NiAl-type body-centered cubic structures. Interestingly, the elastic modulus of the thin film was nearly the same to the bulk single-crystal counterpart, however, the nanohardness is about four times of the bulk single-crystal counterpart. It was found that the high hardness was due to the formation of nanocrystal structure inside the thin filmsmore » and the preferred growth orientation, which could be promising for applications in micro fabrication and advanced coating technologies.« less

Nanoscale size effects on the mechanical properties of platinum thin films and cross-sectional grain morphology

NASA Astrophysics Data System (ADS)

Abbas, K.; Alaie, S.; Ghasemi Baboly, M.; Elahi, M. M. M.; Anjum, D. H.; Chaieb, S.; Leseman, Z. C.

2016-01-01

The mechanical behavior of polycrystalline Pt thin films is reported for thicknesses of 75 nm, 100 nm, 250 nm, and 400 nm. These thicknesses correspond to transitions between nanocrystalline grain morphology types as found in TEM studies. Thinner samples display a brittle behavior, but as thickness increases the grain morphology evolves, leading to a ductile behavior. During evolution of the morphology, dramatic differences in elastic moduli (105-160 GPa) and strengths (560-1700 MPa) are recorded and explained by the variable morphology. This work suggests that in addition to the in-plane grain size of thin films, the transitions in cross-sectional morphologies of the Pt films significantly affect their mechanical behavior.

Transition from Irradiation-Induced Amorphization to Crystallization in Nanocrystalline Silicon Carbide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Weilin; Jiao, Liang; Wang, Haiyan

2011-12-01

Response to irradiation of nanocrystalline 3C-SiC is studied using 2 MeV Au+ ions near the critical temperature for amorphization and is compared to the behavior of its monocrystalline counterpart under the identical irradiation conditions. The irradiated samples have been characterized using in-situ ion channeling, ex-situ x-ray diffraction, and helium ion microscopy. Compared to monocrystalline 3C-SiC, a faster amorphization process in the nanocrystalline material (average grain size = 3.3 nm) is observed at 500 K. However, the nanograin grows with increasing ion fluence at 550 K and the grain size tends to saturate at high fluences. The striking contrast demonstrates amore » sharp transition from irradiation-induced interface-driven amorphization at 500 K to crystallization at 550 K. The results could show potential impacts of nanocrystalline SiC on nuclear fuel cladding and structural components of next-generation nuclear energy systems.« less

Spectroscopic Study of Deep Level Emissions from Acceptor Defects in ZnO Thin Films with Oxygen Rich Stoichiometry

NASA Astrophysics Data System (ADS)

Ilyas, Usman; Rawat, R. S.; Tan, T. L.

2013-10-01

This paper reports the tailoring of acceptor defects in oxygen rich ZnO thin films at different post-deposition annealing temperatures (500-800°C) and Mn doping concentrations. The XRD spectra exhibited the nanocrystalline nature of ZnO thin films along with inconsistent variation in lattice parameters suggesting the temperature-dependent activation of structural defects. Photoluminescence emission spectra revealed the temperature dependent variation in deep level emissions (DLE) with the presence of acceptors as dominating defects. The concentration of native defects was estimated to be increased with temperature while a reverse trend was observed for those with increasing doping concentration. A consistent decrease in DLE spectra, with increasing Mn content, revealed the quenching of structural defects in the optical band gap of ZnO favorable for good quality thin films with enhanced optical transparency.

High Temperature Stable Nanocrystalline SiGe Thermoelectric Material

NASA Technical Reports Server (NTRS)

Yang, Sherwin (Inventor); Matejczyk, Daniel Edward (Inventor); Determan, William (Inventor)

2013-01-01

A method of forming a nanocomposite thermoelectric material having microstructural stability at temperatures greater than 1000 C. The method includes creating nanocrystalline powder by cryomilling. The method is particularly useful in forming SiGe alloy powder.

In-situ TEM observation of the response of ultrafine- and nanocrystalline-grained tungsten to extreme irradiation environments

PubMed Central

El-Atwani, O.; Hinks, J. A.; Greaves, G.; Gonderman, S.; Qiu, T.; Efe, M.; Allain, J. P.

2014-01-01

The accumulation of defects, and in particular He bubbles, can have significant implications for the performance of materials exposed to the plasma in magnetic-confinement nuclear fusion reactors. Some of the most promising candidates for deployment into such environments are nanocrystalline materials as the engineering of grain boundary density offers the possibility of tailoring their radiation resistance properties. In order to investigate the microstructural evolution of ultrafine- and nanocrystalline-grained tungsten under conditions similar to those in a reactor, a transmission electron microscopy study with in situ 2 keV He+ ion irradiation at 950°C has been completed. A dynamic and complex evolution in the microstructure was observed including the formation of defect clusters, dislocations and bubbles. Nanocrystalline grains with dimensions less than around 60 nm demonstrated lower bubble density and greater bubble size than larger nanocrystalline (60–100 nm) and ultrafine (100–500 nm) grains. In grains over 100 nm, uniform distributions of bubbles and defects were formed. At higher fluences, large faceted bubbles were observed on the grain boundaries, especially on those of nanocrystalline grains, indicating the important role grain boundaries can play in trapping He and thus in giving rise to the enhanced radiation tolerance of nanocrystalline materials. PMID:24796578

Studying Structural, Optical, Electrical, and Sensing Properties of Nanocrystalline SnO2:Cu Films Prepared by Sol-Gel Method for CO Gas Sensor Application at Low Temperature

NASA Astrophysics Data System (ADS)

Al-Jawad, Selma M. H.; Elttayf, Abdulhussain K.; Saber, Amel S.

Nanocrystalline SnO2 and SnO2:Cu thin films derived from SnCl2ṡ2H2O precursors have been prepared on glass substrates using sol-gel dip-coating technique. The deposited film was 300±20nm thick and the films were annealed in air at 500∘C for 1h. Structural, optical and sensing properties of the films were studied under different preparation conditions, such as Cu-doping concentration of 2%, 4% and 6wt.%. X-ray diffraction studies show the polycrystalline nature with tetragonal rutile structure of SnO2 and Cu:SnO2 thin films. The films have highly preferred orientation along (110). The crystallite size of the prepared samples reduced with increasing Cu-doping concentrations and the addition of Cu as dopants changed the structural properties of the thin films. Surface morphology was determined through scanning electron microscopy and atomic force microscopy. Results show that the particle size decreased as doping concentration increased. The films have moderate optical transmission (up to 82.4% at 800nm), and the transmittance, absorption coefficient and energy gap at different Cu-doping concentration were measured and calculated. Results show that Cu-doping decreased the transmittance and energy gap whereas it increased the absorption coefficient. Two peaks were noted with Cu-doping concentration of 0-6wt.%; the first peak was positioned exactly at 320nm ultraviolet emission and the second was positioned at 430-480nm. Moreover, emission bands were noticed in the photoluminescence spectra of Cu:SnO2. The electrical properties of SnO2 films include DC electrical conductivity, showing that the films have two activation energies, namely, Ea1 and Ea2, which increase as Cu-doping concentration increases. Cudoped nanocrystalline SnO2 gas-sensing material has better sensitivity to CO gas compared with pure SnO2.

A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

NASA Astrophysics Data System (ADS)

Hussnain, Ali; Singh Rawat, Rajdeep; Ahmad, Riaz; Hussain, Tousif; Umar, Z. A.; Ikhlaq, Uzma; Chen, Zhong; Shen, Lu

2015-02-01

Nano-crystalline tungsten nitride thin films are synthesized on AISI-304 steel at room temperature using Mather-type plasma focus system. The surface properties of the exposed substrate against different deposition shots are examined for crystal structure, surface morphology and mechanical properties using X-ray diffraction (XRD), atomic force microscope, field emission scanning electron microscope and nano-indenter. The XRD results show the growth of WN and WN2 phases and the development of strain/stress in the deposited films by varying the number of deposition shots. Morphology of deposited films shows the significant change in the surface structure with different ion energy doses (number of deposition shots). Due to the effect of different ion energy doses, the strain/stress developed in the deposited film leads to an improvement of hardness of deposited films.

Stabilizing Nanocrystalline Oxide Nanofibers at Elevated Temperatures by Coating Nanoscale Surface Amorphous Films.

PubMed

Yao, Lei; Pan, Wei; Luo, Jian; Zhao, Xiaohui; Cheng, Jing; Nishijima, Hiroki

2018-01-10

Nanocrystalline materials often exhibit extraordinary mechanical and physical properties but their applications at elevated temperatures are impaired by the rapid grain growth. Moreover, the grain growth in nanocrystalline oxide nanofibers at high temperatures can occur at hundreds of degrees lower than that would occur in corresponding bulk nanocrystalline materials, which would eventually break the fibers. Herein, by characterizing a model system of scandia-stabilized zirconia using hot-stage in situ scanning transmission electron microscopy, we discover that the enhanced grain growth in nanofibers is initiated at the surface. Subsequently, we demonstrate that coating the fibers with nanometer-thick amorphous alumina layer can enhance their temperature stability by nearly 400 °C via suppressing the surface-initiated grain growth. Such a strategy can be effectively applied to other oxide nanofibers, such as samarium-doped ceria, yttrium-stabilized zirconia, and lanthanum molybdate. The nanocoatings also increase the flexibility of the oxide nanofibers and stabilize the high-temperature phases that have 10 times higher ionic conductivity. This study provides new insights into the surface-initiated grain growth in nanocrystalline oxide nanofibers and develops a facile yet innovative strategy to improve the high-temperature stability of nanofibers for a broad range of applications.

Evidence of a temperature transition for denuded zone formation in nanocrystalline Fe under He irradiation

DOE PAGES

El-Atwani, Osman; Nathaniel II, James E.; Leff, Asher C.; ...

2016-10-18

Nanocrystalline materials are radiation-tolerant materials’ candidates due to their high defect sink density. Here, nanocrystalline iron films were irradiated with 10 keV helium ions in situ in a transmission electron microscope at elevated temperatures. Grain-size-dependent bubble density changes and denuded zone occurrence were observed at 700 K, but not at 573 K. This transition, attributed to increased helium–vacancy migration at elevated temperatures, suggests that nanocrystalline microstructures are more resistant to swelling at 700 K due to decreased bubble density. Finally, denuded zone formation had no correlation with grain size and misorientation angle under the conditions studied.

Method to grow pure nanocrystalline diamond films at low temperatures and high deposition rates

DOEpatents

Carlisle, John A [Plainfield, IL; Gruen, Dieter M [Downers Grove, IL; Auciello, Orlando [Bolingbrook, IL; Xiao, Xingcheng [Woodridge, IL

2009-07-07

A method of depositing nanocrystalline diamond film on a substrate at a rate of not less than about 0.2 microns/hour at a substrate temperature less than about 500.degree. C. The method includes seeding the substrate surface with nanocrystalline diamond powder to an areal density of not less than about 10.sup.10sites/cm.sup.2, and contacting the seeded substrate surface with a gas of about 99% by volume of an inert gas other than helium and about 1% by volume of methane or hydrogen and one or more of acetylene, fullerene and anthracene in the presence of a microwave induced plasma while maintaining the substrate temperature less than about 500.degree. C. to deposit nanocrystalline diamond on the seeded substrate surface at a rate not less than about 0.2 microns/hour. Coatings of nanocrystalline diamond with average particle diameters of less than about 20 nanometers can be deposited with thermal budgets of 500.degree. C.-4 hours or less onto a variety of substrates such as MEMS devices.

Development of Nanocrystalline Zeolite Materials for the Decontamination of Chemical Warfare Agents

DTIC Science & Technology

2008-11-17

phosphite (CH3O)2P(O)H or DMP. There is -40-20020406080100 In te ns ity ppm a) b) c) d) * ** ** ** * * 33 37 1225 9 Figure 6. 31P MAS NMR spectra...The main objective of this research is to use novel nanocrystalline zeolite materials synthesized in our laboratories for the decontamination of...nanocrystalline zeolite materials. In these studies, we have focused our attention on the decontamination of 2-CEES and DMMP, two simulants for mustard gas

Grain growth behavior at absolute zero during nanocrystalline metal indentation

NASA Astrophysics Data System (ADS)

Sansoz, F.; Dupont, V.

2006-09-01

The authors show using atomistic simulations that stress-driven grain growth can be obtained in the athermal limit during nanocrystalline aluminum indentation. They find that the grain growth results from rotation of nanograins and propagation of shear bands. Together, these mechanisms are shown to lead to the unstable migration of grain boundaries via process of coupled motion. An analytical model is used to explain this behavior based on the atomic-level shear stress acting on the interfaces during the shear band propagation. This study sheds light on the atomic mechanism at play during the abnormal grain coarsening observed at low temperature in nanocrystalline metals.

Post-annealing-free, room temperature processed nanocrystalline indium tin oxide thin films for plastic electronics

NASA Astrophysics Data System (ADS)

Nyoung Jang, Jin; Jong Lee, You; Jang, YunSung; Yun, JangWon; Yi, Seungjun; Hong, MunPyo

2016-06-01

In this study, we confirm that bombardment by high energy negative oxygen ions (NOIs) is the key origin of electro-optical property degradations in indium tin oxide (ITO) thin films formed by conventional plasma sputtering processes. To minimize the bombardment effect of NOIs, which are generated on the surface of the ITO targets and accelerated by the cathode sheath potential on the magnetron sputter gun (MSG), we introduce a magnetic field shielded sputtering (MFSS) system composed of a permanent magnetic array between the MSG and the substrate holder to block the arrival of energetic NOIs. The MFSS processed ITO thin films reveal a novel nanocrystal imbedded polymorphous structure, and present not only superior electro-optical characteristics but also higher gas diffusion barrier properties. To the best of our knowledge, no gas diffusion barrier composed of a single inorganic thin film formed by conventional plasma sputtering processes achieves such a low moisture permeability.

Nanocrystalline sp{sup 2} and sp{sup 3} carbons: CVD synthesis and applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terranova, M. L.; Rossi, M.; Tamburri, E., E-mail: emanuela.tamburri@uniroma2.it

The design and production of innovative materials based on nanocrystalline sp{sup 2}- and sp{sup 3}-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

Room temperature chemical bath deposition of cadmium selenide, cadmium sulfide and cadmium sulfoselenide thin films with novel nanostructures

NASA Astrophysics Data System (ADS)

VanderHyde, Cephas A.; Sartale, S. D.; Patil, Jayant M.; Ghoderao, Karuna P.; Sawant, Jitendra P.; Kale, Rohidas B.

2015-10-01

A simple, convenient and low cost chemical synthesis route has been used to deposit nanostructured cadmium sulfide, selenide and sulfoselenide thin films at room temperature. The films were deposited on glass substrates, using cadmium acetate as cadmium ion and sodium selenosulfate/thiourea as a selenium/sulfur ion sources. Aqueous ammonia was used as a complex reagent and also to adjust the pH of the final solution. The as-deposited films were uniform, well adherent to the glass substrate, specularly reflective and red/yellow in color depending on selenium and sulfur composition. The X-ray diffraction pattern of deposited cadmium selenide thin film revealed the nanocrystalline nature with cubic phase; cadmium sulfide revealed mixture of cubic along with hexagonal phase and cadmium sulfoselenide thin film were grown with purely hexagonal phase. The morphological observations revealed the growth and formation of interesting one, two and three-dimensional nanostructures. The band gap of thin films was calculated and the results are reported.

Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

PubMed

Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

2008-08-01

Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

DOE PAGES

Coloyan, Gabriella; Cultrara, Nicholas D.; Katre, Ankita; ...

2016-09-30

Recently, we synthesized Germanane (GeH), a hydrogen-terminated layered germanium structure. We employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. Furthermore, the obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53± 0.03 W m -1 K -1, which is close to the value calculated for 3.3 nm grain size, to 0.29± 0.02more » W m -1 K -1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.« less

Basal-plane thermal conductivity of nanocrystalline and amorphized thin germanane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coloyan, Gabriella; Cultrara, Nicholas D.; Katre, Ankita

Recently, we synthesized Germanane (GeH), a hydrogen-terminated layered germanium structure. We employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. Furthermore, the obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53± 0.03 W m -1 K -1, which is close to the value calculated for 3.3 nm grain size, to 0.29± 0.02more » W m -1 K -1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.« less

Application of ASTAR(TM)/Precession Electron Diffraction Technique to Quantitatively Study Defects in Nanocrystalline Metallic Materials

NASA Astrophysics Data System (ADS)

Ghamarian, Iman

Nanocrystalline metallic materials have the potential to exhibit outstanding performance which leads to their usage in challenging applications such as coatings and biomedical implant devices. To optimize the performance of nanocrystalline metallic materials according to the desired applications, it is important to have a decent understanding of the structure, processing and properties of these materials. Various efforts have been made to correlate microstructure and properties of nanocrystalline metallic materials. Based on these research activities, it is noticed that microstructure and defects (e.g., dislocations and grain boundaries) play a key role in the behavior of these materials. Therefore, it is of great importance to establish methods to quantitatively study microstructures, defects and their interactions in nanocrystalline metallic materials. Since the mechanisms controlling the properties of nanocrystalline metallic materials occur at a very small length scale, it is fairly difficult to study them. Unfortunately, most of the characterization techniques used to explore these materials do not have the high enough spatial resolution required for the characterization of these materials. For instance, by applying complex profile-fitting algorithms to X-ray diffraction patterns, it is possible to get an estimation of the average grain size and the average dislocation density within a relatively large area. However, these average values are not enough for developing meticulous phenomenological models which are able to correlate microstructure and properties of nanocrystalline metallic materials. As another example, electron backscatter diffraction technique also cannot be used widely in the characterization of these materials due to problems such as relative poor spatial resolution (which is 90 nm) and the degradation of Kikuchi diffraction patterns in severely deformed nano-size grain metallic materials. In this study, ASTAR(TM)/precession electron

Stability of nanocrystalline Ni-based alloys: coupling Monte Carlo and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Waseda, O.; Goldenstein, H.; Silva, G. F. B. Lenz e.; Neiva, A.; Chantrenne, P.; Morthomas, J.; Perez, M.; Becquart, C. S.; Veiga, R. G. A.

2017-10-01

The thermal stability of nanocrystalline Ni due to small additions of Mo or W (up to 1 at%) was investigated in computer simulations by means of a combined Monte Carlo (MC)/molecular dynamics (MD) two-steps approach. In the first step, energy-biased on-lattice MC revealed segregation of the alloying elements to grain boundaries. However, the condition for the thermodynamic stability of these nanocrystalline Ni alloys (zero grain boundary energy) was not fulfilled. Subsequently, MD simulations were carried out for up to 0.5 μs at 1000 K. At this temperature, grain growth was hindered for minimum global concentrations of 0.5 at% W and 0.7 at% Mo, thus preserving most of the nanocrystalline structure. This is in clear contrast to a pure Ni model system, for which the transformation into a monocrystal was observed in MD simulations within 0.2 μs at the same temperature. These results suggest that grain boundary segregation of low-soluble alloying elements in low-alloyed systems can produce high-temperature metastable nanocrystalline materials. MD simulations carried out at 1200 K for 1 at% Mo/W showed significant grain boundary migration accompanied by some degree of solute diffusion, thus providing additional evidence that solute drag mostly contributed to the nanostructure stability observed at lower temperature.

Effect of Pre-Annealing on Thermal and Optical Properties of ZnO and Al-ZnO Thin Films

NASA Astrophysics Data System (ADS)

Saravanan, P.; Gnanavelbabu, A.; Pandiaraj, P.

Zinc oxide (ZnO) nanoparticles were synthesized by a simple solution route method using zinc acetate as the precursor and ethanol as the solvent. At a temperature of 60∘C, a clear homogenous solution is heated to 100∘C for ethanol evaporation. Then the obtained precursor powder is annealed at 600∘C for the formation of ZnO nanocrystalline structure. Doped ZnO particle is also prepared by using aluminum nitrate nonahydrate to produce aluminum (Al)-doped nanoparticles using the same solution route method followed by annealing. Thin film fabrication is done by air evaporation method using the polymer polyvinyl alcohol (PVA). To analyze the optical and thermal properties for undoped and doped ZnO nanocrystalline thin film by precursor annealing, characterizations such as UV, FTIR, AFM, TGA/DTA, XRD, EDAX and Photoluminescence (PL) were also taken. It was evident that precursor annealing had great influence on thermal and optical properties of thin films while ZnO and AZO film showed low crystallinity and intensity than in the powder form. TGA/DTA suggests pre-annealing effect improves the thermal stability, which ensures that Al ZnO nanoparticle can withstand at high temperature too which is the crucial advantage in the semiconductor devices. UV spectroscopy confirmed the presence of ZnO nanoparticles in the thin film by an absorbance peak observed at 359nm with an energy bandgap of 3.4eV. A peak obtained at 301nm with an energy bandgap of 4.12eV shows a blue shift due to the presence of Al-doped ZnO nanoparticles. Both ZnO and AZO bandgap increased due to precursor annealing. In this research, PL spectrum is also studied in order to determine the optical property of the nanoparticle embedded thin film. From PL spectrum, it is observed that the intensity of the doped ZnO is much more enhanced as the dopant concentration is increased to 1wt.% and 2wt.% of Al in ZnO.

Europium-doped mesoporous titania thin films: rare-earth locations and emission fluctuations under illumination.

PubMed

Leroy, Celine Marie; Cardinal, Thierry; Jubera, Veronique; Treguer-Delapierre, Mona; Majimel, Jerome; Manaud, Jean Pierre; Backov, Renal; Boissière, Cedric; Grosso, David; Sanchez, Clement; Viana, Bruno; Pellé, Fabienne

2008-10-06

Herein, Eu(III)-doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare-earth-doped titania thin films-synthesized via evaporation-induced self-assembly (EISA)-are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high-resolution scanning electron microscopy, HR-SEM, and transmission electron microscopy, HR-TEM), X-ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium-ion loadings can be incorporated into the titanium-dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu(III) are investigated by using steady-state and time-resolved spectroscopy via excitation of the Eu(III) ions through the titania host. Using Eu(III) luminescence as a probe, the europium-ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations ((5)D(0)-->(7)F(2)) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.

Stacking fault energies and slip in nanocrystalline metals.

PubMed

Van Swygenhoven, H; Derlet, P M; Frøseth, A G

2004-06-01

The search for deformation mechanisms in nanocrystalline metals has profited from the use of molecular dynamics calculations. These simulations have revealed two possible mechanisms; grain boundary accommodation, and intragranular slip involving dislocation emission and absorption at grain boundaries. But the precise nature of the slip mechanism is the subject of considerable debate, and the limitations of the simulation technique need to be taken into consideration. Here we show, using molecular dynamics simulations, that the nature of slip in nanocrystalline metals cannot be described in terms of the absolute value of the stacking fault energy-a correct interpretation requires the generalized stacking fault energy curve, involving both stable and unstable stacking fault energies. The molecular dynamics technique does not at present allow for the determination of rate-limiting processes, so the use of our calculations in the interpretation of experiments has to be undertaken with care.

Effect of power on growth of nanocrystalline silicon films deposited by VHF PECVD technique for solar cell applications

NASA Astrophysics Data System (ADS)

Juneja, Sucheta; Verma, Payal; Savelyev, Dmitry A.; Khonina, Svetlana N.; Sudhakar, S.; Kumar, Sushil

2016-04-01

An investigation of the effect of power on the deposition of nanocrystalline silicon thin films were carried out using a gaseous mixture of silane and hydrogen in the 60MHz assisted VHF plasma enhanced chemical vapor deposition (PECVD) technique. The power was varied from 10 to 50 watt maintaining all other parameters constant. Corresponding layer properties w.r.t. material microstructure, optical, hydrogen content and electrical transport are studied in detail. The structural properties have been studied by Raman spectroscopy and x-ray diffraction (XRD). The presence of nano-sized crystals and their morphology have been investigated using atomic force microscopy (AFM). The role of bonded hydrogen content in the films have been studied from the results of Fourier transform infrared spectroscopy. It was observed from the results that with increase in power, crystalline volume fraction increases and crystallite size changes from 4 to 9 nm. The optical band gap varies from 1.7 to 2.1eV due to quantum confinement effect and which further can be explained with reduced hydrogen content. These striking features of nc-Si films can be used to fabricate stable thin film solar cells.

Ultrathin Nanocrystalline Diamond Films with Silicon Vacancy Color Centers via Seeding by 2 nm Detonation Nanodiamonds.

PubMed

Stehlik, Stepan; Varga, Marian; Stenclova, Pavla; Ondic, Lukas; Ledinsky, Martin; Pangrac, Jiri; Vanek, Ondrej; Lipov, Jan; Kromka, Alexander; Rezek, Bohuslav

2017-11-08

Color centers in diamonds have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report chemical vapor deposition (CVD) growth of nanocrystalline diamond (NCD) films as thin as 5-6 nm with photoluminescence (PL) from silicon-vacancy (SiV) centers at 739 nm. Instead of conventional 4-6 nm detonation nanodiamonds (DNDs), we prepared and employed hydrogenated 2 nm DNDs (zeta potential = +36 mV) to form extremely dense (∼1.3 × 10 13 cm -2 ), thin (2 ± 1 nm), and smooth (RMS roughness < 0.8 nm) nucleation layers on an Si/SiO x substrate, which enabled the CVD growth of such ultrathin NCD films in two different and complementary microwave (MW) CVD systems: (i) focused MW plasma with an ellipsoidal cavity resonator and (ii) pulsed MW plasma with a linear antenna arrangement. Analytical ultracentrifuge, infrared and Raman spectroscopies, atomic force microscopy, and scanning electron microscopy are used for detailed characterization of the 2 nm H-DNDs and the nucleation layer as well as the ultrathin NCD films. We also demonstrate on/off switching of the SiV center PL in the NCD films thinner than 10 nm, which is achieved by changing their surface chemistry.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel.

PubMed

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel

PubMed Central

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification. PMID:22768383

Grain boundary and triple junction diffusion in nanocrystalline copper

NASA Astrophysics Data System (ADS)

Wegner, M.; Leuthold, J.; Peterlechner, M.; Song, X.; Divinski, S. V.; Wilde, G.

2014-09-01

Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, , of ˜35 and ˜44 nm produced by spark plasma sintering were investigated by the radiotracer method using the 63Ni isotope. The measured diffusivities, Deff, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500ṡDgb within the temperature interval from 420 K to 470 K.

Analyzing Dirac Cone and Phonon Dispersion in Highly Oriented Nanocrystalline Graphene.

PubMed

Nai, Chang Tai; Xu, Hai; Tan, Sherman J R; Loh, Kian Ping

2016-01-26

Chemical vapor deposition (CVD) is one of the most promising growth techniques to scale up the production of monolayer graphene. At present, there are intense efforts to control the orientation of graphene grains during CVD, motivated by the fact that there is a higher probability for oriented grains to achieve seamless merging, forming a large single crystal. However, it is still challenging to produce single-crystal graphene with no grain boundaries over macroscopic length scales, especially when the nucleation density of graphene nuclei is high. Nonetheless, nanocrystalline graphene with highly oriented grains may exhibit single-crystal-like properties. Herein, we investigate the spectroscopic signatures of graphene film containing highly oriented, nanosized grains (20-150 nm) using angle-resolved photoemission spectroscopy (ARPES) and high-resolution electron energy loss spectroscopy (HREELS). The robustness of the Dirac cone, as well as dispersion of its phonons, as a function of graphene's grain size and before and after film coalescence, was investigated. In view of the sensitivity of atomically thin graphene to atmospheric adsorbates and intercalants, ARPES and HREELS were also used to monitor the changes in spectroscopic signatures of the graphene film following exposure to the ambient atmosphere.

Multiphase Nanocrystalline Ceramic Concept for Nuclear Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mecartnery, Martha; Graeve, Olivia; Patel, Maulik

2017-05-25

The goal of this research is to help develop new fuels for higher efficiency, longer lifetimes (higher burn-up) and increased accident tolerance in future nuclear reactors. Multiphase nanocrystalline ceramics will be used in the design of simulated advanced inert matrix nuclear fuel to provide for enhanced plasticity, better radiation tolerance, and improved thermal conductivity

Anti-inflammatory activity of nanocrystalline silver-derived solutions in porcine contact dermatitis

PubMed Central

2010-01-01

Background Nanocrystalline silver dressings have anti-inflammatory activity, unlike solutions containing Ag+ only, which may be due to dissolution of multiple silver species. These dressings can only be used to treat surfaces. Thus, silver-containing solutions with nanocrystalline silver properties could be valuable for treating hard-to-dress surfaces and inflammatory conditions of the lungs and bowels. This study tested nanocrystalline silver-derived solutions for anti-inflammatory activity. Methods Inflammation was induced on porcine backs using dinitrochlorobenzene. Negative and positive controls were treated with distilled water. Experimental groups were treated with solutions generated by dissolving nanocrystalline silver in distilled water adjusted to starting pHs of 4 (using CO2), 5.6 (as is), 7, and 9 (using Ca(OH)2). Solution samples were analyzed for total silver. Daily imaging, biopsying, erythema and oedema scoring, and treatments were performed for three days. Biopsies were processed for histology, immunohistochemistry (for IL-4, IL-8, IL-10, TNF-α, EGF, KGF, KGF-2, and apoptotic cells), and zymography (MMP-2 and -9). One-way ANOVAs with Tukey-Kramer post tests were used for statistical analyses. Results Animals treated with pH 7 and 9 solutions showed clear visual improvements. pH 9 solutions resulted in the most significant reductions in erythema and oedema scores. pH 4 and 7 solutions also reduced oedema scores. Histologically, all treatment groups demonstrated enhanced re-epithelialisation, with decreased inflammation. At 24 h, pMMP-2 expression was significantly lowered with pH 5.6 and 9 treatments, as was aMMP-2 expression with pH 9 treatments. In general, treatment with silver-containing solutions resulted in decreased TNF-α and IL-8 expression, with increased IL-4, EGF, KGF, and KGF-2 expression. At 24 h, apoptotic cells were detected mostly in the dermis with pH 4 and 9 treatments, nowhere with pH 5.6, and in both the epidermis and dermis

A general higher-order nonlocal couple stress based beam model for vibration analysis of porous nanocrystalline nanobeams

NASA Astrophysics Data System (ADS)

Ebrahimi, Farzad; Barati, Mohammad Reza

2017-12-01

This paper develops a higher order refined beam model with a parabolic shear strain function for vibration analysis of porous nanocrystalline nanobeams based on nonlocal couple stress theory. Nanocrystalline nanobeam is composed from three phases which are nano-grains, nano-voids and interface. Nano-voids or porosities inside the material have a stiffness-softening impact on the nanobeam. Nonlocal elasticity theory of Eringen is applied in analysis of nanocrystalline nanobeams for the first time. Also, modified couple stress theory is employed to capture grains rigid rotations. The governing equations obtained from Hamilton's principle are solved applying an analytical approach which satisfies various boundary conditions. The reliability of present approach is verified by comparing obtained results with those provided in literature. Finally the influences of nonlocal parameter, couple stress, grain size, porosities and shear deformation on the vibration characteristics of nanocrystalline nanobeams are explored.

Cyclic compression response of micropillars extracted from textured nanocrystalline NiTi thin-walled tubes

DOE PAGES

Ghassemi-Armaki, Hassan; Leff, Asher C.; Taheri, Mitra L.; ...

2017-06-22

Compression-compression cyclic deformation of nanocrystalline NiTi tubes intended for medical stents and with an outer diameter of 1 mm and wall thickness of 70 μm was studied using micropillars produced by FIB with the loading axis orthogonal to the tube axis. These micropillars were cycled in a displacement-controlled mode using a nanoindenter equipped with a flat punch to strain levels of 4, 6 and 8% in each cycle and specimens were subjected to several hundred cycles. Furthermore, the cyclic response of two NiTi tubes, one with Af of 17 °C and the other with an Af of -5 °C ismore » compared. The texture of the tube with the Af of -5 °C was measured at the microscopic level using transmission electron microscopy and at the macroscopic level by X-ray diffraction and good agreement was noted. Characteristics such as i) a reduction in the forward transformation stress, ii) increase in maximum stress for a given displacement amplitude, and iii) a reduction in the hysteresis loop area, all with increasing number of cycles, observed typically during cyclic deformation of conventional macroscopic specimens, were captured in the micropillar cyclic tests. Our observations lead to the conclusion that micropillar compression testing in a cyclic mode can enable characterizing the orientation-dependent response in such small dimension components that see complex loading in service, and additionally provide an opportunity for calibrating constitutive equations in micromechanical models.« less

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

NASA Astrophysics Data System (ADS)

Drake, Christina Hartsell

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature

Functional materials based on nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Surov, O. V.; Voronova, M. I.; Zakharov, A. G.

2017-10-01

The data on the synthesis of functional materials based on nanocrystalline cellulose (NCC) published over the past 10 years are analyzed. The liquid-crystal properties of NCC suspensions, methods of investigation of NCC suspensions and films, conditions for preserving chiral nematic structure in the NCC films after removal of the solvent and features of templated sol-gel synthesis of functional materials based on NCC are considered. The bibliography includes 106 references.

Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

PubMed

Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

2017-05-10

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

NASA Astrophysics Data System (ADS)

Degmová, J.; Sitek, J.

2010-07-01

Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

Remediation of arsenic and lead with nanocrystalline zinc sulfide.

PubMed

Piquette, Alan; Cannon, Cody; Apblett, Allen W

2012-07-27

Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

Solid state amorphization of nanocrystalline nickel by cryogenic laser shock peening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Chang, E-mail: cye@uakron.edu; Ren, Zhencheng; Zhao, Jingyi

2015-10-07

In this study, complete solid state amorphization in nanocrystalline nickel has been achieved through cryogenic laser shock peening (CLSP). High resolution transmission electron microscopy has revealed the complete amorphous structure of the sample after CLSP processing. A molecular dynamic model has been used to investigate material behavior during the shock loading and the effects of nanoscale grain boundaries on the amorphization process. It has been found that the initial nanoscale grain boundaries increase the initial Gibbs free energy before plastic deformation and also serve as dislocation emission sources during plastic deformation to contribute to defect density increase, leading to themore » amorphization of pure nanocrystalline nickel.« less

Influence of film thickness and Fe doping on LPG sensing properties of Mn3O4 thin film grown by SILAR method

NASA Astrophysics Data System (ADS)

Belkhedkar, M. R.; Ubale, A. U.

2018-05-01

Nanocrystalline Fe doped and undoped Mn3O4 thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates using MnCl2 and NaOH as cationic and anionic precursors. The grazing incidence X-ray diffraction (GIXRD) and field emission scanning electron microscopy (FESEM)) have been carried out to analyze structural and surface morphological properties of the films. The LPG sensing performance of Mn3O4thin films have been studied by varying temperature, concentration of LPG, thickness of the film and doping percentage of Fe. The LPG response of the Mn3O4thin films were found to be enhances with film thickness and decreases with increased Fe doping (0 to 8 wt. %) at 573 K temperature.

Grain boundary character distribution in nanocrystalline metals produced by different processing routes

DOE PAGES

Bober, David B.; Kumar, Mukal; Rupert, Timothy J.; ...

2015-12-28

Nanocrystalline materials are defined by their fine grain size, but details of the grain boundary character distribution should also be important. Grain boundary character distributions are reported for ball-milled, sputter-deposited, and electrodeposited Ni and Ni-based alloys, all with average grain sizes of ~20 nm, to study the influence of processing route. The two deposited materials had nearly identical grain boundary character distributions, both marked by a Σ3 length percentage of 23 to 25 pct. In contrast, the ball-milled material had only 3 pct Σ3-type grain boundaries and a large fraction of low-angle boundaries (16 pct), with the remainder being predominantlymore » random high angle (73 pct). Furthermore, these grain boundary character measurements are connected to the physical events that control their respective processing routes. Consequences for material properties are also discussed with a focus on nanocrystalline corrosion. As a whole, the results presented here show that grain boundary character distribution, which has often been overlooked in nanocrystalline metals, can vary significantly and influence material properties in profound ways.« less

Preparation of multilayered nanocrystalline thin films with composition-modulated interfaces

NASA Astrophysics Data System (ADS)

Biro, D.; Barna, P. B.; Székely, L.; Geszti, O.; Hattori, T.; Devenyi, A.

2008-06-01

The properties of multilayer thin film structures depend on the morphology and structure of interfaces. A broad interface, in which the composition is varying, can enhance, e.g., the hardness of multilayer thin films. In the present experiments multilayers of TiAlN and CrN as well as TiAlN, CrN and MoS 2 were studied by using unbalanced magnetron sputter sources. The sputter sources were arranged side by side on an arc. This arrangement permits development of a transition zone between the layers, where the composition changes continuously. The multilayer system was deposited by one-fold oscillating movement of substrates in front of sputter sources. Thicknesses of layers could be changed both by oscillation frequency and by the power applied to sputter sources. Ti/Al: 50/50 at%, pure chromium and MoS 2 targets were used in the sputter sources. The depositions were performed in an Ar-N 2 mixture at 0.22 Pa working pressure. The sputtering power of the TiAl source was feed-back adjusted in fuzzy-logic mode in order to avoid fluctuation of the TiAl target sputter rate due to poisoning of the target surface. Structure characterization of films deposited on <1 0 0> Si wafers covered by thermally grown SiO 2 was performed by cross-sectional transmission electron microscopy. At first a 100 nm thick Cr base layer was deposited on the substrate to improve adhesion, which was followed by a CrN transition layer. The CrN transition layer was followed by a 100 nm thick TiAlN/CrN multilayer system. The TiAlN/CrN/MoS 2 multilayer system was deposited on the surface of this underlayer system. The underlayer systems Cr, CrN and TiAlN/CrN were crystalline with columnar structure according to the morphology of zone T of the structure zone models. The column boundaries contained segregated phases showing up in the under-focused TEM images. The surface of the underlayer system was wavy due to dome-shaped columns. The nanometer-scaled TiAlN/CrN/MoS 2 multilayer system followed this

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings.

PubMed

Wang, Yuxin; Cheng, Guang; Tay, See Leng; Guo, Yunxia; Sun, Xin; Gao, Wei

2017-08-10

In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

Transmission electron microscopy of polyhydroxybutyrate-co-valerate (PHBV)/nanocrystalline cellulose (NCC) bio-nanocomposite prepared using cryo-ultramicrotomy

NASA Astrophysics Data System (ADS)

Ismarul, N. I.; Engku, A. H. E. U.; Siti, N. K.; Tay, K. Y.

2017-12-01

Environmental issues on disposal and end-of-life for product made from synthetic petroleum-derived polymers have gained increasing attention from materials scientist to search for new materials with similar physical and mechanical properties but environmental friendly in a way that they are renewable and biodegradable as well. This work is to study the effect of nanocrystalline cellulose in improving the thermal stability of polyhydroxybutyrate-co-valerate biopolymer for high temperature processing of packaging material. 10 % w/w PHBV-NCC bio-nanocomposite feedstock pellet prepared using RONDOL minilab compounder was used as the sample for the preparation of Transmission Electron Microscopy (TEM) sample. RMC Cryo-Ultramicrotomy equipment was used to prepare the ultra-thin slice of the bio-nanocomposite pellet under liquid nitrogen at - 60 °C. Diamond knife was used to slice off about 80-100 nm ultra-thin bio-nanocomposite films and was transferred into the lacey carbon film coated grid using cooled sugar solution. A few drops of phosphotungstic acid was used as negative stain to improve the contrast during the TEM analysis. HITACHI TEM systems was used to obtain the TEM micrograph of PHBV-NCC bio-nanocomposite using 80kV accelerating voltage. A well dispersed NCC in PHBV matrix, ranging from 5 to 25 nm in width was observed.

Comparative study on corrosion resistance and in vitro biocompatibility of bulk nanocrystalline and microcrystalline biomedical 304 stainless steel.

PubMed

Nie, F L; Wang, S G; Wang, Y B; Wei, S C; Zheng, Y F

2011-07-01

SUS 304 stainless steels have been widely used in orthodontics and implants such as archwires, brackets, and screws. The purpose of present study was to investigate the biocompatibility of both the commercial microcrystalline biomedical 304 stainless steel (microcrystalline 304ss) and novel-fabricated nanocrystalline 304 stainless steel (nanocrystalline 304ss). Bulk nanocrystalline 304ss sheets had been successfully prepared by microcrystalline 304ss plates using severe rolling technique. The electrochemical corrosion and ion release behavior immersion in artificial saliva were measured to evaluate the property of biocorrosion in oral environment. The cell lines of murine and human cell lines from oral and endothelial environment were co-cultured with extracts to evaluate the cytotoxicity and provide referential evidence in vivo. The polarization resistance trials indicated that nanocrystalline 304ss is more corrosion resistant than the microcrystalline 304ss in oral-like environment with higher corrosion potential, and the amount of toxic ions released into solution after immersion is lower than that of the microcrystalline 304ss and the daily dietary intake level. The cytotoxicity results also elucidated that nanocrystalline 304ss is biologically compatible in vitro, even better than that of microcrystalline 304ss. Based on the much higher mechanical and physical performances, nanocrystalline 304ss with enhanced biocorrosion property, well-behaved in vitro cytocompatibility can be a promising alternative in orthodontics and fixation fields in oral cavity. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation.

PubMed

Yang, Lina; Minnich, Austin J

2017-03-14

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation

PubMed Central

Yang, Lina; Minnich, Austin J.

2017-01-01

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials. PMID:28290484

Synthesis and characterization of cadmium sulphide thin films prepared by spin coating

NASA Astrophysics Data System (ADS)

Chodavadiya, Nisarg; Chapanari, Amisha; Zinzala, Jignesh; Ray, Jaymin; Pandya, Samir

2018-05-01

An II-VI group semiconductor is Wide band gap materials and has been widely studied due to their fundamental optical, structural, and electrical properties. Cadmium sulphide (CdS) is one of the most emerged materials in II-VI group. It has many applications such as buffer later in photovoltaic cell, multilayer light emitting diodes, optical filters, thin film field effect transistors, gas sensors, light detectors etc. It is fundamentally an n-type material with an optical band gap of 2.4 eV. Owing to these properties we had studied CdS thin films synthesis and characterized by Raman, Ultraviolet - Visible spectroscopy (UV-VIS) and Hot probe method. CdS thin films were prepared by spin coating of the Cadmium-thiourea precursor solution. Visual inspection after 20 minute thermolysis time the films were looks uniform and shiny pale yellow in color. Raman confirms the A1 vibration of pure CdS. UV-VIS gives the band gap about 2.52 eV, which confirms the formation of nanocrystalline form of CdS. Finally, hot probe signifies the n-type conductivity of the CdS film.

Properties of nanocrystalline Si layers embedded in structure of solar cell

NASA Astrophysics Data System (ADS)

Jurečka, Stanislav; Imamura, Kentaro; Matsumoto, Taketoshi; Kobayashi, Hikaru

2017-12-01

Suppression of spectral reflectance from the surface of solar cell is necessary for achieving a high energy conversion efficiency. We developed a simple method for forming nanocrystalline layers with ultralow reflectance in a broad range of wavelengths. The method is based on metal assisted etching of the silicon surface. In this work, we prepared Si solar cell structures with embedded nanocrystalline layers. The microstructure of embedded layer depends on the etching conditions. We examined the microstructure of the etched layers by a transmission electron microscope and analysed the experimental images by statistical and Fourier methods. The obtained results provide information on the applied treatment operations and can be used to optimize the solar cell forming procedure.

Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

2003-10-01

Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

Effect of oxygen partial pressure and VO2 content on hexagonal WO3 thin films synthesized by pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Kaushal, Ajay; Kaur, Davinder

2011-06-01

We report on the effect of oxygen partial pressure and vacuum annealing on structural and optical properties of pulsed laser-deposited nanocrystalline WO3 thin films. XRD results show the hexagonal phase of deposited WO3 thin films. The crystallite size was observed to increase with increase in oxygen partial pressure. Vacuum annealing changed the transparent as-deposited WO3 thin film to deep shade of blue color which increases the optical absorption of the film. The origin of this blue color could be due to the presence of oxygen vacancies associated with tungsten ions in lower oxidation states. In addition, the effects of VO2 content on structural, electrochemical, and optical properties of (WO3)1- x (VO2) x nanocomposite thin films have also been systematically investigated. Cyclic voltammogram exhibits a modification with the appearance of an extra cathodic peak for VO2-WO3 thin film electrode with higher VO2 content ( x ≥ 0.2). Increase of VO2 content in (WO3)1- x (VO2) x films leads to red shift in optical band gap.

Investigation of physicochemical and tribological properties of transparent oxide semiconducting thin films based on Ti-V oxides

NASA Astrophysics Data System (ADS)

Mazur, M.; Sieradzka, K.; Kaczmarek, D.; Domaradzki, J.; Wojcieszak, D.; Domanowski, P.

2013-08-01

In this paper investigations of structural and optical properties of nanocrystalline Ti-V oxide thin films are described. The films were deposited onto Corning 7059 glass using a modified reactive magnetron sputtering method. Structural investigations of prepared Ti-V oxides with vanadium addition of 19 at. % revealed amorphous structure, while incorporation of 21 and 23 at. % of vanadium resulted in V2O5 formation with crystallites sizes of 12.7 and 32.4 nm, respectively. All prepared thin films belong to transparent oxide semiconductors due to their high transmission level of ca. 60-75 % in the visible light range, and resistivity in the range of 3.3·102-1.4·105 Ωcm. Additionally, wettability and hardness tests were performed in order to evaluate the usefulness of the films for functional coatings.

Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, J.; Sun, C.; Dholabhai, P. P.

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A 2Ti 2O 7 (A = Gd, Ho and Lu)

DOE PAGES

Wen, J.; Sun, C.; Dholabhai, P. P.; ...

2016-03-21

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2Ti 2O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20–30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarse-grained counterparts, indicating anmore » enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2Ti 2O 7, was further examined by performing ion irradiation at an elevated temperature range of 480–600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2Ti 2O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2Ti 2O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics calculations find that cation antisite defects are less energetically costly to form near surfaces than in the bulk, suggesting that the nanocrystalline form of these materials is generally less susceptible to amorphization than coarse-grained counterparts at low temperatures where defect kinetics are negligible. In contrast, at high temperatures, the annealing efficiency of antisite defects by cation interstitials is significantly reduced due to the sink properties of the surfaces in the nanocrystalline pyrochlore, which contributes to the observed higher amorphization temperature in the nano-grained phase than in coarse-grained counterpart. Altogether, these

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuxin; Cheng, Guang; Tay, See Leng

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

DOE PAGES

Wang, Yuxin; Cheng, Guang; Tay, See Leng; ...

2017-08-10

Here in this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomicmore » percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Lastly, results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.« less

Influence of coating on nanocrystalline magnetic properties during high temperature thermal ageing

NASA Astrophysics Data System (ADS)

Lekdim, Atef; Morel, Laurent; Raulet, Marie-Ange

2017-05-01

Since their birth or mergence the late 1980s, the nanocrystalline ultrasoft magnetic materials are taking a great importance in power electronic systems conception. One of the main advantages that make them more attractive nowadays is their ability to be packaged since the reduction of the magnetostrictive constant to almost zero. In aircraft applications, due to the high component compactness and to their location (for example near the jet engine), the operating temperature increases and may reach easily 200 °C and more. Consequently, the magnetic thermal ageing may occur but is, unfortunately, weakly studied. This paper focuses on the influence of the coating (packaging type) on the magnetic nanocrystalline performances during a thermal ageing. This study is based on monitoring the magnetic characteristics of two types of nanocrystalline cores (naked and coated) during a thermal activated ageing (100, 150 and 200 °C). Based on a dedicated monitoring protocol, a large magnetic characterization has been done and analyzed. Elsewhere, X-Ray Diffraction and magnetostriction measurements were carried out to support the study of the anisotropy energies evolution with ageing. This latter is discussed in this paper to explain and give hypothesis about the ageing phenomena.

Study on the corrosion properties of nanocrystalline nickel electrodepositied by reverse pulse current

NASA Astrophysics Data System (ADS)

Cheng, Wen; Ge, Wen; Yang, Qian; Qu, Xinxin

2013-07-01

Nanocrystalline nickel coatings were produced by the method of reverse pulse electrodepositing on the surface of steel sheets. The crystallite size of nanocrystalline nickel coatings was determined by X-ray diffraction (XRD). The effect of saccharin concentration on the crystallite size of the coatings was studied. The average crystallite sizes were diminished as a result of increasing saccharin concentration. CHI660C electrochemical workstation was used to determine the Tafel polarization curves and electrochemical impedance spectroscopy (EIS) of the coatings. The value of corrosion potential, natural corrosion current density, polarizaiton resistance and impedance was calculated, the results suggested that smaller grain size led to higher polarization resistance. EIS gave the charge transfer resistance Rct and pore resistance Rpo variation trend from beginning to 30 min. Scanning electron microscopy (SEM) examination showed the surface morphology of the nickel coatings after the neutral salt spray (NSS) test or bathing in 10% HCl. The images indicated that the corrosion behavior of nanocrystalline nickel coatings was pitting corrosion, the mechanism was also discussed.

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

NASA Astrophysics Data System (ADS)

Mayabadi, A. H.; Waman, V. S.; Kamble, M. M.; Ghosh, S. S.; Gabhale, B. B.; Rondiya, S. R.; Rokade, A. V.; Khadtare, S. S.; Sathe, V. G.; Pathan, H. M.; Gosavi, S. W.; Jadkar, S. R.

2014-02-01

Nanocrystalline thin films of TiO2 were prepared on glass substrates from an aqueous solution of TiCl3 and NH4OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO2 transition from a mixed anatase-rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO2 thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29-3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.

New twinning route in face-centered cubic nanocrystalline metals.

PubMed

Wang, Lihua; Guan, Pengfei; Teng, Jiao; Liu, Pan; Chen, Dengke; Xie, Weiyu; Kong, Deli; Zhang, Shengbai; Zhu, Ting; Zhang, Ze; Ma, Evan; Chen, Mingwei; Han, Xiaodong

2017-12-15

Twin nucleation in a face-centered cubic crystal is believed to be accomplished through the formation of twinning partial dislocations on consecutive atomic planes. Twinning should thus be highly unfavorable in face-centered cubic metals with high twin-fault energy barriers, such as Al, Ni, and Pt, but instead is often observed. Here, we report an in situ atomic-scale observation of twin nucleation in nanocrystalline Pt. Unlike the classical twinning route, deformation twinning initiated through the formation of two stacking faults separated by a single atomic layer, and proceeded with the emission of a partial dislocation in between these two stacking faults. Through this route, a three-layer twin was nucleated without a mandatory layer-by-layer twinning process. This route is facilitated by grain boundaries, abundant in nanocrystalline metals, that promote the nucleation of separated but closely spaced partial dislocations, thus enabling an effective bypassing of the high twin-fault energy barrier.

Visualizing decoupling in nanocrystalline alloys: A FORC-temperature analysis

NASA Astrophysics Data System (ADS)

Rivas, M.; Martínez-García, J. C.; Gorria, P.

2016-02-01

Devitrifying ferromagnetic amorphous precursors in the adequate conditions may give rise to disordered assemblies of densely packed nanocrystals with extraordinary magnetic softness well explained by the exchange coupling among multiple crystallites. Whether the magnetic exchange interaction is produced by direct contact or mediated by the intergranular amorphous matrix has a strong influence on the behaviour of the system above room temperature. Multi-phase amorphous-nanocrystalline systems dramatically harden when approaching the amorphous Curie temperature (TC) due to the hard grains decoupling. The study of the thermally induced decoupling of nanosized crystallites embedded in an amorphous matrix has been performed in this work by the first-order reversal curves (FORCs) analysis. We selected a Fe-rich amorphous alloy with TC = 330 K, in order to follow the evolution of the FORC diagrams obtained below and above such temperature in samples with different percentages of nanocrystalline phase. The existence of up to four regions exhibiting unlike magnetic behaviours is unambiguously determined from the temperature evolution of the FORC.

Effect of slurry composition on the chemical mechanical polishing of thin diamond films

PubMed Central

Werrell, Jessica M.; Mandal, Soumen; Thomas, Evan L. H.; Brousseau, Emmanuel B.; Lewis, Ryan; Borri, Paola; Davies, Philip R.; Williams, Oliver A.

2017-01-01

Nanocrystalline diamond (NCD) thin films grown by chemical vapour deposition have an intrinsic surface roughness, which hinders the development and performance of the films’ various applications. Traditional methods of diamond polishing are not effective on NCD thin films. Films either shatter due to the combination of wafer bow and high mechanical pressures or produce uneven surfaces, which has led to the adaptation of the chemical mechanical polishing (CMP) technique for NCD films. This process is poorly understood and in need of optimisation. To compare the effect of slurry composition and pH upon polishing rates, a series of NCD thin films have been polished for three hours using a Logitech Ltd. Tribo CMP System in conjunction with a polyester/polyurethane polishing cloth and six different slurries. The reduction in surface roughness was measured hourly using an atomic force microscope. The final surface chemistry was examined using X-ray photoelectron spectroscopy and a scanning electron microscope. It was found that of all the various properties of the slurries, including pH and composition, the particle size was the determining factor for the polishing rate. The smaller particles polishing at a greater rate than the larger ones. PMID:29057022

Effect of slurry composition on the chemical mechanical polishing of thin diamond films

NASA Astrophysics Data System (ADS)

Werrell, Jessica M.; Mandal, Soumen; Thomas, Evan L. H.; Brousseau, Emmanuel B.; Lewis, Ryan; Borri, Paola; Davies, Philip R.; Williams, Oliver A.

2017-12-01

Nanocrystalline diamond (NCD) thin films grown by chemical vapour deposition have an intrinsic surface roughness, which hinders the development and performance of the films' various applications. Traditional methods of diamond polishing are not effective on NCD thin films. Films either shatter due to the combination of wafer bow and high mechanical pressures or produce uneven surfaces, which has led to the adaptation of the chemical mechanical polishing (CMP) technique for NCD films. This process is poorly understood and in need of optimisation. To compare the effect of slurry composition and pH upon polishing rates, a series of NCD thin films have been polished for three hours using a Logitech Ltd. Tribo CMP System in conjunction with a polyester/polyurethane polishing cloth and six different slurries. The reduction in surface roughness was measured hourly using an atomic force microscope. The final surface chemistry was examined using X-ray photoelectron spectroscopy and a scanning electron microscope. It was found that of all the various properties of the slurries, including pH and composition, the particle size was the determining factor for the polishing rate. The smaller particles polishing at a greater rate than the larger ones.

Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang

Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

PubMed

Deka, Sasanka; Joy, P A

2008-08-01

Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

DOE PAGES

Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang; ...

2018-09-06

Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mehmood, S. K.; Mansoor, M.; Asim, M. M.

2014-06-01

PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.

Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films.

PubMed

Ciesielski, Richard; Schäfer, Frank; Hartmann, Nicolai F; Giesbrecht, Nadja; Bein, Thomas; Docampo, Pablo; Hartschuh, Achim

2018-03-07

Micro- and nanocrystalline methylammonium lead iodide (MAPI)-based thin-film solar cells today reach power conversion efficiencies of over 20%. We investigate the impact of grain boundaries on charge carrier transport in large crystal MAPI thin films using time-resolved photoluminescence (PL) microscopy and numerical model calculations. Crystal sizes in the range of several tens of micrometers allow for the spatially and time resolved study of boundary effects. Whereas long-ranged diffusive charge carrier transport is observed within single crystals, no detectable diffusive transport occurs across grain boundaries. The observed PL transients are found to crucially depend on the microscopic geometry of the crystal and the point of observation. In particular, spatially restricted diffusion of charge carriers leads to slower PL decay near crystal edges as compared to the crystal center. In contrast to many reports in the literature, our experimental results show no quenching or additional loss channels due to grain boundaries for the studied material, which thus do not negatively affect the performance of the derived thin-film devices.

Nanocrystallinity effects on osteoblast and osteoclast response to silicon substituted hydroxyapatite.

PubMed

Casarrubios, Laura; Matesanz, María Concepción; Sánchez-Salcedo, Sandra; Arcos, Daniel; Vallet-Regí, María; Portolés, María Teresa

2016-11-15

Silicon substituted hydroxyapatites (SiHA) are highly crystalline bioceramics treated at high temperatures (about 1200°C) which have been approved for clinical use with spinal, orthopedic, periodontal, oral and craniomaxillofacial applications. The preparation of SiHA with lower temperature methods (about 700°C) provides nanocrystalline SiHA (nano-SiHA) with enhanced bioreactivity due to higher surface area and smaller crystal size. The aim of this study has been to know the nanocrystallinity effects on the response of both osteoblasts and osteoclasts (the two main cell types involved in bone remodelling) to silicon substituted hydroxyapatite. Saos-2 osteoblasts and osteoclast-like cells (differentiated from RAW-264.7 macrophages) have been cultured on the surface of nano-SiHA and SiHA disks and different cell parameters have been evaluated: cell adhesion, proliferation, viability, intracellular content of reactive oxygen species, cell cycle phases, apoptosis, cell morphology, osteoclast-like cell differentiation and resorptive activity. This comparative in vitro study evidences that nanocrystallinity of SiHA affects the cell/biomaterial interface inducing bone cell apoptosis by loss of cell anchorage (anoikis), delaying osteoclast-like cell differentiation and decreasing the resorptive activity of this cell type. These results suggest the potential use of nano-SiHA biomaterial for preventing bone resorption in treatment of osteoporotic bone. Copyright © 2016 Elsevier Inc. All rights reserved.

Wear behavior of Cu-Zn alloy by ultrasonic nanocrystalline surface modification.

PubMed

Cho, In Shik; Amanov, Auezhan; Ahn, Deok Gi; Shin, Keesam; Lee, Chang Soon; Pyoun, Young-Shik; Park, In-Gyu

2011-07-01

The ultrasonic nanocrystalline surface modification (UNSM) was applied to disk specimens made of Cu-Zn alloy in order to investigate the UNSM effects under five various conditions on wear of deformation twinning. In this paper, ball-on-disk test was conducted, and the results of UNSM-treated specimens showed that surface layer dislocation density and multi-directional twins were abruptly increased, and the grain size was altered into nano scale. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. The UNSM technology creates nanocrystalline and deformation twinning on the workpiece surface. One of the main concepts of this study is that defined phenomena of the UNSM technology, and the results revealed that nanocrystalline and deformation twinning depth might be controlled by means of impact energy of UNSM technology. EBSD and TEM analyses showed that deformation layer was increased up to 268 microm, and initial twin density was 0.001 x 10(6) cm(-2) and increased up to 0.343 x 10(6) cm(-2). Wear volume loss was also decreased from 703 x 10(3) mm3 to 387 x 10(3) mm3. Wear behavior according to deformation depth was observed under three different combinations. This is related to deformation depth which was created by UNSM technology.

Qualitative and quantitative differentiation of gases using ZnO thin film gas sensors and pattern recognition analysis.

PubMed

Pati, Sumati; Maity, A; Banerji, P; Majumder, S B

2014-04-07

In the present work we have grown highly textured, ultra-thin, nano-crystalline zinc oxide thin films using a metal organic chemical vapor deposition technique and addressed their selectivity towards hydrogen, carbon dioxide and methane gas sensing. Structural and microstructural characteristics of the synthesized films were investigated utilizing X-ray diffraction and electron microscopy techniques respectively. Using a dynamic flow gas sensing measurement set up, the sensing characteristics of these films were investigated as a function of gas concentration (10-1660 ppm) and operating temperature (250-380 °C). ZnO thin film sensing elements were found to be sensitive to all of these gases. Thus at a sensor operating temperature of ~300 °C, the response% of the ZnO thin films were ~68, 59, and 52% for hydrogen, carbon monoxide and methane gases respectively. The data matrices extracted from first Fourier transform analyses (FFT) of the conductance transients were used as input parameters in a linear unsupervised principal component analysis (PCA) pattern recognition technique. We have demonstrated that FFT combined with PCA is an excellent tool for the differentiation of these reducing gases.

Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration.

PubMed

Subramanian, Munisamy; Tanemura, Masaki; Hihara, Takehiko; Soga, Tetsuo; Jimbo, Takashi

2011-04-01

The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

Analysis of a nanocrystalline polymer dispersion of ebselen using solid-state NMR, Raman microscopy, and powder X-ray diffraction.

PubMed

Vogt, Frederick G; Williams, Glenn R

2012-07-01

Nanocrystalline drug-polymer dispersions are of significant interest in pharmaceutical delivery. The purpose of this work is to demonstrate the applicability of methods based on two-dimensional (2D) and multinuclear solid-state NMR (SSNMR) to a novel nanocrystalline pharmaceutical dispersion of ebselen with polyvinylpyrrolidone-vinyl acetate (PVP-VA), after initial characterization with other techniques. A nanocrystalline dispersion of ebselen with PVP-VA was prepared and characterized by powder X-ray diffraction (PXRD), confocal Raman microscopy and mapping, and differential scanning calorimetry (DSC), and then subjected to detailed 1D and 2D SSNMR analysis involving ¹H, ¹³C, and ⁷⁷Se isotopes and ¹H spin diffusion. PXRD was used to show that dispersion contains nanocrystalline ebselen in the 35-60 nm size range. Confocal Raman microscopy and spectral mapping were able to detect regions where short-range interactions may occur between ebselen and PVP-VA. Spin diffusion effects were analyzed using 2D SSNMR experiments and are able to directly detect interactions between ebselen and the surrounding PVP-VA. The methods used here, particularly the 2D SSNMR methods based on spin diffusion, provided detailed structural information about a nanocrystalline polymer dispersion of ebselen, and should be useful in other studies of these types of materials.

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice

Effect of Annealing Temperature on Structural and Optical Properties of Sol-Gel-Derived ZnO Thin Films

NASA Astrophysics Data System (ADS)

Arif, Mohd.; Sanger, Amit; Vilarinho, Paula M.; Singh, Arun

2018-04-01

Nanocrystalline ZnO thin films were deposited on glass substrate via sol-gel dip-coating technique then annealed at 300°C, 400°C, and 500°C for 1 h. Their optical, structural, and morphological properties were studied using ultraviolet-visible (UV-Vis) spectrophotometry, x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). XRD diffraction revealed that the crystalline nature of the thin films increased with increasing annealing temperature. The c-axis orientation improved, and the grain size increased, as indicated by increased intensity of the (002) plane peak at 2θ = 34.42° corresponding to hexagonal ZnO crystal. The average crystallite size of the thin films ranged from 13 nm to 23 nm. Increasing the annealing temperature resulted in larger crystallite size and higher crystallinity with increased surface roughness. The grain size according to SEM analysis was in good agreement with the x-ray diffraction data. The optical bandgap of the thin films narrowed with increasing annealing temperature, lying in the range of 3.14 eV to 3.02 eV. The transmission of the thin films was as high as 94% within the visible region. The thickness of the thin films was 400 nm, as measured by ellipsometry, after annealing at the different temperatures of 300°C, 400°C, and 500°C.

Hydrothermal synthesis of mesoporous rod-like nanocrystalline vanadium oxide hydrate V{sub 3}O{sub 7}·H{sub 2}O from hydroquinone and V{sub 2}O{sub 5}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mjejri, I.; Etteyeb, N.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn

2013-09-01

Graphical abstract: - Highlights: • Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has heen synthesized hydrothermally. • Molar ratio is key factor for structure and morphology. • Electrochemical properties were also studied. • CV has revealed reversible redox behavior with charge–discharge cycling. - Abstract: Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has been synthesized hydrothermally via a simple and elegant route. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials.more » The as-prepared V{sub 3}O{sub 7}·H{sub 2}O nanorods are up to several of micrometers in length, about 130 nm in width and about 70 nm in thickness in average, respectively. Cyclic voltammetric characterization of thin films of V{sub 3}O{sub 7}·H{sub 2}O nanorods has revealed reversible redox behavior with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation.« less

Piezoelectric actuated micro-resonators based on the growth of diamond on aluminum nitride thin films.

PubMed

Hees, J; Heidrich, N; Pletschen, W; Sah, R E; Wolfer, M; Williams, O A; Lebedev, V; Nebel, C E; Ambacher, O

2013-01-18

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

Thermal Stability of Nanocrystalline Copper for Potential Use in Printed Wiring Board Applications

NASA Astrophysics Data System (ADS)

Woo, Patrick Kai Fai

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultra-fine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25-230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40?C to 400?C. During isothermal annealing experiments samples were annealed at 23?C, 100?C and 300?C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of

Structural and morphological study of chemically synthesized CdSe thin films

NASA Astrophysics Data System (ADS)

Agrawal, P.; Singh, Randhir; Sharma, Jeewan; Sachdeva, M.; Singh, Anupinder; Bhargava, A.

2018-05-01

Nanocrystalline CdSe thin films were prepared by Chemical Bath Deposition (CBD) method using potassium nitrilo-triacetic acid cadmium complex and sodium selenosulphite. The as deposited films were red in color, uniform and well adherent to the glass substrate. These films were strongly dependent on the deposition parameters such as bath composition, deposition temperature and time. Films were annealed at 350 °C for four hours. The morphological, structural and optical properties were studied using X-ray diffraction (XRD), UV-VIS spectrophotometer measurements, scanning electron microscopy and atomic force microscopy. The XRD analysis confirmed that films are predominantly in hexagonal phase. Scanning electron micrograph shows that the grains are uniformly spread all over the film and each grain contains many nanocrystals with spherical shapes.

Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

DOE PAGES

Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; ...

2014-12-21

In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K -1 m -1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constantsmore » were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K -1 m -1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.« less

Superhard Nanocrystalline Homometallic Stainless Steel on Steel for Seamless Coatings

NASA Technical Reports Server (NTRS)

Tobin, Eric J.; Hafley, R. (Technical Monitor)

2002-01-01

The objective of this work is to deposit nanocrystalline stainless steel onto steel substrates (homometallic) for enhanced wear and corrosion resistance. Homometallic coatings provide superior adhesion, and it has been shown that ultrafine-grained materials exhibit the increased hardness and decreased permeability desired for protective coatings. Nanocrystals will be produced by controlling nucleation and growth and use of an ion beam during deposition by e-beam evaporation or sputtering. Phase I is depositing 31 6L nanocrystalline stainless steel onto 31 6L stainless steel substrates. These coatings exhibit hardnesses comparable to those normally obtained for ceramic coatings such ZrO2, and possess the superior adhesion of seamless, homometallic coatings. Hardening the surface with a similar material also enhances adhesion, by avoiding problems associated with thermal and lattice mismatch. So far we have deposited nanocrystalline homometallic 316L stainless steel coatings by varying the ions and the current density of the ion beams. For all deposition conditions we have produced smooth, uniform, superhard coatings. All coatings exhibit hardness of at least 200% harder than that of bulk materials. Our measurements indicate that there is a direct relationship between nanohardness and the current density of the ion beam. Stress measurements indicate that stress in the films is increasingly proportional to current density of the ion beam. TEM, XPS, and XRD results indicate that the coated layers consist of FCC structure nanocrystallites with a dimension of about 10 to 20 nm. The Ni and Mo concentration of these coating are lower than those of bulk 316L but the concentration of Cr is higher.

Nanocrystalline Nb-Al-Ge mixtures fabricated using wet mechanical milling

NASA Astrophysics Data System (ADS)

Pusceddu, E.; Charlton, S.; Hampshire, D. P.

2008-02-01

An investigation into Nb-Al-Ge mixtures is presented with special attention to the superconducting compounds Nb3(Al1-xGex) with x = 0, 0.3 and 1, which are reported to provide the highest upper critical field values for Nb-based compounds. Wet mechanical milling using copper milling media and distilled water as a process control agent (PCA) was used with the intention of improving the yield, properties and the performance of these materials. Very high yields of nanocrystalline material were achieved but significant copper contamination occurred - confirmed using inductively-coupled-plasma atomic-emission-spectroscopy. Simultaneous thermogravimetric measurements and differential scanning calorimetry were performed on powders milled for up to 20 h with different PCA content, to quantify the work done on the powders. A typical grain size of a few nm was obtained for the Nb-Al-Ge mixtures after several hours milling. Powder ground for 20 h with 5% PCA was processed using a hot isostatic press (HIP) operating at 2000 atm and temperatures up to 750 °C. The room temperature resistivity decreased as the temperature of the HIPing increased. Unfortunately, despite the nanocrystalline microstructure of the powders and the high HIP temperatures, if superconducting material was formed it was below the detection level of resistivity, Ac. susceptibility and SQUID measurements. We conclude that during milling there was widespread contamination of the powders by the PCA so that milling with distilled water as a PCA is not to be recommended for fabricating nanocrystalline Nb3(Al1-xGex) A15 superconducting compounds.

Impact of differently modified nanocrystalline diamond on the growth of neuroblastoma cells.

PubMed

Vaitkuviene, Aida; McDonald, Matthew; Vahidpour, Farnoosh; Noben, Jean-Paul; Sanen, Kathleen; Ameloot, Marcel; Ratautaite, Vilma; Kaseta, Vytautas; Biziuleviciene, Gene; Ramanaviciene, Almira; Nesladek, Milos; Ramanavicius, Arunas

2015-01-25

The aim of this study was to assess the impact of nanocrystalline diamond (NCD) thin coatings on neural cell adhesion and proliferation. NCD was fabricated on fused silica substrates by microwave plasma chemical vapor deposition (MPCVD) method. Different surface terminations were performed through exposure to reactive hydrogen and by UV induced oxidation during ozone treatment. Boron doped NCD coatings were also prepared and investigated. NCD surface wettability was determined by contact angle measurement. To assess biocompatibility of the NCD coatings, the neuroblastoma SH-SY5Y cell line was used. Cells were plated directly onto diamond surfaces and cultured in medium with or without fetal bovine serum (FBS), in order to evaluate the ability of cells to adhere and to proliferate. The obtained results showed that these cells adhered and proliferated better on NCD surfaces than on the bare fused silica. The cell proliferation on NCD in medium with and without FBS after 48h from plating was on average, respectively, 20 and 58% higher than that on fused silica, irrespective of NCD surface modification. Our results showed that the hydrogenated, oxygenated and boron-doped NCD coatings can be used for biomedical purposes, especially where good optical transparency is required. Copyright © 2014 Elsevier B.V. All rights reserved.

Study on the growth mechanism and optical properties of sputtered lead selenide thin films

NASA Astrophysics Data System (ADS)

Sun, Xigui; Gao, Kewei; Pang, Xiaolu; Yang, Huisheng; Volinsky, Alex A.

2015-11-01

Lead selenide thin films with different microstructure were deposited on Si (1 0 0) substrates using magnetron sputtering at 50 °C, 150 °C and 250 °C, respectively. The crystal structure of the sputtered PbSe thin films varies from amorphous crystalline to columnar grain, and then to double-layer (nano-crystalline layer and columnar grain layer) structure as the deposition temperature increases, which is due to the dominating growth mode of the thin films changes from Frank-van der Merwe (or layer-by-layer) growth mode at 50 °C to Volmer-Weber (or 3D island) growth mode at 150 °C, and then to Stranski-Krastanow (or 3D island-on-wetting-layer) growth mode at 250 °C. The growth mechanism of the sputtered PbSe thin films is mainly dominated by the surface and strain energy contributions. Moreover, the strain energy contribution is more prominent when the deposition temperature is less than 180 °C, while, the surface energy contribution is more prominent when the deposition temperature is higher than 180 °C. The absorption spectra of the sputtered PbSe thin films are in 3.1-5 μm range. Besides, the sputtered PbSe thin film prepared at 250 °C has two different optical band gaps due to its unique double-layer structure. According to the theoretical calculation results, the variation of the band gap with the deposition temperature is determined by the shift of the valence band maximum with the lattice constant.

Nano-enabled tribological thin film coatings: global patent scenario.

PubMed

Sivudu, Kurva S; Mahajan, Yashwant R; Joshi, Shrikant V

2014-01-01

The aim of this paper is to present current status and future prospects of nano-enabled tribological thin film coatings based on worldwide patent landscape analysis. The study also presents an overview of technological trends by carrying out state-of-the-art literature analysis, including survey of corporate websites. Nanostructured tribological coatings encompass a wide spectrum of nanoscale microstructures, including nanocrystalline, nanolayered, nano-multilayered, nanocomposite, nanogradient structures or their unique combinations, which are composed of single or multi-component phases. The distinct microstructural features of the coatings impart outstanding tribological properties combined with multifunctional attributes to the coated components. Their unique combination of remarkable properties make them ideal candidates for a wide range of applications in diverse fields such as cutting and metalworking tools, biomedical devices, automotive engine components, wear parts, hard disc drives etc. The patent landscape analysis has revealed that nano-enabled tribological thin film coatings have significant potential for commercial applications in view of the lion's share of corporate industry in patenting activity. The largest patent portfolio is held by Japan followed by USA, Germany, Sweden and China. The prominent players involved in this field are Mitsubishi Materials Corp., Sandvik Aktiebolag, Hitachi Ltd., Sumitomo Electric Industries Ltd., OC Oerlikon Corp., and so on. The outstanding potential of nanostructured thin film tribological coatings is yet to be fully unravelled and, therefore, immense opportunities are available in future for microstructurally engineered novel coatings to enhance their performance and functionality by many folds.

Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

NASA Astrophysics Data System (ADS)

Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

2015-06-01

Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takashiri, Masayuki, E-mail: takashiri@tokai-u.jp; Kurita, Kensuke; Hagino, Harutoshi

2015-08-14

A two-step method that combines homogeneous electron beam (EB) irradiation and thermal annealing has been developed to enhance the thermoelectric properties of nanocrystalline bismuth selenium telluride thin films. The thin films, prepared using a flash evaporation method, were treated with EB irradiation in a N{sub 2} atmosphere at room temperature and an acceleration voltage of 0.17 MeV. Thermal annealing was performed under Ar/H{sub 2} (5%) at 300 °C for 60 min. X-ray diffraction was used to determine that compositional phase separation between bismuth telluride and bismuth selenium telluride developed in the thin films exposed to higher EB doses and thermal annealing. We proposemore » that the phase separation was induced by fluctuations in the distribution of selenium atoms after EB irradiation, followed by the migration of selenium atoms to more stable sites during thermal annealing. As a result, thin film crystallinity improved and mobility was significantly enhanced. This indicates that the phase separation resulting from the two-step method enhanced, rather than disturbed, the electron transport. Both the electrical conductivity and the Seebeck coefficient were improved following the two-step method. Consequently, the power factor of thin films that underwent the two-step method was enhanced to 20 times (from 0.96 to 21.0 μW/(cm K{sup 2}) that of the thin films treated with EB irradiation alone.« less

A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jambure, S.B.; Patil, S.J.; Deshpande, A.R.

2014-01-01

Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z{sub 1}) and nanograins by SILAR (Z{sub 2}). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. Themore » X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10{sup 2} Ω cm) is lower than that of SILAR deposited films (10{sup 5} Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method.« less

Anisotropic nanocrystalline MnBi with high coercivity at high temperature

NASA Astrophysics Data System (ADS)

Yang, J. B.; Yang, Y. B.; Chen, X. G.; Ma, X. B.; Han, J. Z.; Yang, Y. C.; Guo, S.; Yan, A. R.; Huang, Q. Z.; Wu, M. M.; Chen, D. F.

2011-08-01

Magnetic hard nanocrystalline MnBi has been prepared by melt spinning and subsequent low temperature annealing. A coercivity of 2.5 T can be achieved at 540 K for MnBi with an average grain size of about 20-30 nm. The coercivity iHc, mainly controlled by the coherent magnetization rotation, shows a strong dependence on the time of grinding and exhibits a positive temperature coefficient from 100 up to 540 K. The unique temperature dependent behavior of the coercivity (magnetocrystalline anisotropy) has a relationship with the variations in the crystal lattice ratio of c/a with temperatures. In addition, discontinuity can not be found in the lattice parameters of a, c, and c/a ratio at the magnetostructural transition temperature. The nanocrystalline MnBi powder fixed in an epoxy resin and under an applied magnetic field of 24 kOe shows a maximum energy product of 7.1 MGOe at room temperature and shows anisotropic characteristics with high Mr/Ms ratio up to 560 K.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-06-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Performance characteristics of nanocrystalline diamond vacuum field emission transistor array

NASA Astrophysics Data System (ADS)

Hsu, S. H.; Kang, W. P.; Davidson, J. L.; Huang, J. H.; Kerns, D. V.

2012-05-01

Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. The experimental results obtained for the ac voltage gain are found to agree with the theoretical model. A higher ac voltage gain is attainable by using a better test setup to eliminate the associated parasitic capacitances. The paper reveals the amplifier characteristics of the ND-VFET for potential applications in vacuum microelectronics.

Production of hydrogen using nanocrystalline protein-templated catalysts on m13 phage.

PubMed

Neltner, Brian; Peddie, Brian; Xu, Alex; Doenlen, William; Durand, Keith; Yun, Dong Soo; Speakman, Scott; Peterson, Andrew; Belcher, Angela

2010-06-22

For decades, ethanol has been in use as a fuel for the storage of solar energy in an energy-dense, liquid form. Over the past decade, the ability to reform ethanol into hydrogen gas suitable for a fuel cell has drawn interest as a way to increase the efficiency of both vehicles and stand-alone power generators. Here we report the use of extremely small nanocrystalline materials to enhance the performance of 1% Rh/10% Ni@CeO(2) catalysts in the oxidative steam reforming of ethanol with a ratio of 1.7:1:10:11 (air/EtOH/water/argon) into hydrogen gas, achieving 100% conversion of ethanol at only 300 degrees C with 60% H(2) in the product stream and less than 0.5% CO. Additionally, nanocrystalline 10% Ni@CeO(2) was shown to achieve 100% conversion of ethanol at 400 degrees C with 73% H(2), 2% CO, and 2% CH(4) in the product stream. Finally, we demonstrate the use of biological templating on M13 to improve the resistance of this catalyst to deactivation over 52 h tests at high flow rates (120 000 h(-1) GHSV) at 450 degrees C. This study suggests that the use of highly nanocrystalline, biotemplated catalysts to improve activity and stability is a promising route to significant gains over traditional catalyst manufacture methods.

Enhanced properties of tungsten thin films deposited with a novel HiPIMS approach

NASA Astrophysics Data System (ADS)

Velicu, Ioana-Laura; Tiron, Vasile; Porosnicu, Corneliu; Burducea, Ion; Lupu, Nicoleta; Stoian, George; Popa, Gheorghe; Munteanu, Daniel

2017-12-01

Despite the tremendous potential for industrial use of tungsten (W), very few studies have been reported so far on controlling and tailoring the properties of W thin films obtained by physical vapor deposition techniques and, even less, for those deposited by High Power Impulse Magnetron Sputtering (HiPIMS). This study presents results on the deposition process and properties characterization of nanocrystalline W thin films deposited on silicon and molybdenum substrates (100 W average sputtering power) by conventional dc magnetron sputtering (dcMS) and HiPIMS techniques. Topological, structural, mechanical and tribological properties of the deposited thin films were investigated. It was found that in HiPIMS, both deposition process and coatings properties may be optimized by using an appropriate magnetic field configuration and pulsing design. Compared to the other deposited samples, the W films grown in multi-pulse (5 × 3 μs) HiPIMS assisted by an additional magnetic field, created with a toroidal-shaped permanent magnet placed in front of the magnetron cathode, show significantly enhanced properties, such as: smoother surfaces, higher homogeneity and denser microstructure, higher hardness and Young's modulus values, better adhesion to the silicon substrate and lower coefficient of friction. Mechanical behaviour and structural changes are discussed based on plasma diagnostics results.

Nano-Crystalline Thermally Evaporated Bi2Se3 Thin Films Synthesized from Mechanically Milled Powder

NASA Astrophysics Data System (ADS)

Amara, A.; Abdennouri, N.; Drici, A.; Abdelkader, D.; Bououdina, M.; Chaffar Akkari, F.; Khemiri, N.; Kanzari, M.; Bernède, J. C.

2017-08-01

Bi2Se3 powder has been successfully synthesized via mechanical ball milling of bismuth and selenium as starting materials. X-ray diffraction characterization revealed the formation of the rhombohedral and orthorhombic phases of Bi2Se3 material belonging to systems with space groups R\\bar{3}m and Pbnm, respectively. The advantageous last finding is confirmed by the Rietveld refinement of the x-ray diffraction data. Furthermore, the analysis of the x-ray data of thermally deposited thin films revealed that both orthorhombic and rhombohedral phases are coexisting in the layer. The morphology of the ball milled powder was studied by scanning electron microscopy. The phase formation of the material is confirmed by Raman spectroscopy. M-H (Magnetization versus Magnetic field) curve indicates that Bi2Se3 powder has a ferromagnetic behavior. Additionally, absorbance and transmittance measurements were carried out on the obtained thermally evaporated thin films and yielded a band gap of 1.33 eV supporting the potential application of the heterogeneous rhombohedral/orthorhombic Bi2Se3 material in photovoltaics.

Effect of swift heavy ion irradiation on structural and opto-electrical properties of bi-layer CdS-Bi2S3 thin films prepared by solution growth technique at room temperature

NASA Astrophysics Data System (ADS)

Shaikh, Shaheed U.; Siddiqui, Farha Y.; Desale, Deepali J.; Ghule, Anil V.; Singh, Fouran; Kulriya, Pawan K.; Sharma, Ramphal

2015-01-01

CdS-Bi2S3 bi-layer thin films have been deposited by chemical bath deposition method on Indium Tin Oxide glass substrate at room temperature. The as-deposited thin films were annealed at 250 °C in an air atmosphere for 1 h. An air annealed thin film was irradiated using Au9+ ions with the energy of 120 MeV at fluence 5×1012 ions/cm2 using tandem pelletron accelerator. The irradiation induced modifications were studied using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Raman spectroscopy, UV spectroscopy and I-V characteristics. XRD study reveals that the as-deposited thin films were nanocrystalline in nature. The decrease in crystallite size, increase in energy band gap and resistivity were observed after irradiation. Results are explained on the basis of energy deposited by the electronic loss after irradiation. The comparative results of as-deposited, air annealed and irradiated CdS-Bi2S3 bi-layer thin films are presented.

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

DOE PAGES

Barr, Christopher M.; Li, Nan; Boyce, Brad L.; ...

2018-05-01

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

Examining the influence of grain size on radiation tolerance in the nanocrystalline regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barr, Christopher M.; Li, Nan; Boyce, Brad L.

Here, nanocrystalline materials have been proposed as superior radiation tolerant materials in comparison to coarse grain counterparts. However, there is still a limited understanding whether a particular nanocrystalline grain size is required to obtain significant improvements in key deleterious effects resulting from energetic irradiation. This work employs the use of in-situ heavy ion irradiation transmission electron microscopy experiments coupled with quantitative defect characterization and precession electron diffraction to explore the sensitivity of defect size and density within the nanocrystalline regime in platinum. Under the explored experimental conditions, no significant change in either the defect size or density between grain sizesmore » of 20 and 100 nm was observed. Furthermore, the in-situ transmission electron microscopy irradiations illustrate stable sessile defect clusters of 1–3 nm adjacent to most grain boundaries, which are traditionally treated as strong defect sinks. The stability of these sessile defects observed in-situ in small, 20–40 nm, grains is the proposed primary mechanism for a lack of defect density trends. Lastly, this scaling breakdown in radiation improvement with decreasing grain size has practical importance on nanoscale grain boundary engineering approaches for proposed radiation tolerant alloys.« less

The impact of diamond nanocrystallinity on osteoblast functions.

PubMed

Yang, Lei; Sheldon, Brian W; Webster, Thomas J

2009-07-01

Nanocrystalline diamond has been proposed as an anti-abrasive film on orthopedic implants. In this study, osteoblast (bone forming cells) functions including adhesion (up to 4h), proliferation (up to 5 days) and differentiation (up to 21 days) on different diamond film topographies were systematically investigated. In order to exclude interferences from changes in surface chemistry and wettability (energy), diamond films with nanometer and micron scale topographies were fabricated through microwave plasma enhanced chemical-vapor-deposition and hydrogen plasma treatment. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and water contact angle measurements verified the similar surface chemistry and wettability but varied topographies for all of the diamond films prepared on silicon in this study. Cytocompatibility assays demonstrated enhanced osteoblast functions (including adhesion, proliferation, intracellular protein synthesis, alkaline phosphatase activity and extracellular calcium deposition) on nanocrystalline diamond compared to submicron diamond grain size films for all time periods tested up to 21 days. An SEM study of osteoblast attachment helped to explain the topographical impact diamond had on osteoblast functions by showing altered filopodia extensions on the different diamond topographies. In summary, these results provided insights into understanding the role diamond nanotopography had on osteoblast interactions and more importantly, the application of diamond films to improve orthopedic implant lifetimes.

Change of magnetic properties of nanocrystalline alloys under influence of external factors

NASA Astrophysics Data System (ADS)

Sitek, Jozef; Holková, Dominika; Dekan, Julius; Novák, Patrik

2016-10-01

Nanocrystalline (Fe3Ni1)81Nb7B12 alloys were irradiated using different types of radiation and subsequently studied by Mössbauer spectroscopy. External magnetic field of 0.5 T, electron-beam irradiation up to 4 MGy, neutron irradiation up to 1017 neutrons/cm2 and irradiation with Cu ions were applied on the samples. All types of external factors had an influence on the magnetic microstructure manifested as a change in the direction of the net magnetic moment, intensity of the internal magnetic field and volumetric fraction of the constituent phases. The direction of the net magnetic moment was the most sensitive parameter. Changes of the microscopic magnetic parameters were compared after different external influence and results of nanocrystalline samples were compared with their amorphous precursors.

Defect structure in electrodeposited nanocrystalline Ni layers with different Mo concentrations

NASA Astrophysics Data System (ADS)

Kapoor, Garima; Péter, László; Fekete, Éva; Gubicza, Jenő

2018-05-01

The effect of molybdenum (Mo) alloying on the lattice defect structure in electrodeposited nanocrystalline nickel (Ni) films was studied. The electrodeposited layers were prepared on copper substrate at room temperature, with a constant current density and pH value. The chemical composition of these layers was determined by EDS. In addition, X-ray diffraction line profile analysis was carried out to study the microstructural parameters such as the crystallite size, the dislocation density and the stacking fault probability. It was found that the higher Mo content yielded more than one order of magnitude larger dislocation density while the crystallite size was only slightly smaller. In addition, the twin boundary formation activity during deposition increased with increasing Mo concentration. The results obtained on electrodeposited layers were compared with previous research carried out on bulk nanocrystalline Ni-Mo materials with similar compositions but processed by severe plastic deformation.

Ultrahigh hardness and high electrical resistivity in nano-twinned, nanocrystalline high-entropy alloy films

NASA Astrophysics Data System (ADS)

Huo, Wenyi; Liu, Xiaodong; Tan, Shuyong; Fang, Feng; Xie, Zonghan; Shang, Jianku; Jiang, Jianqing

2018-05-01

Nano-twinned, nanocrystalline CoCrFeNi high-entropy alloy films were produced by magnetron sputtering. The films exhibit a high hardness of 8.5 GPa, the elastic modulus of 161.9 GPa and the resistivity as high as 135.1 μΩ·cm. The outstanding mechanical properties were found to result from the resistance of deformation created by nanocrystalline grains and nano-twins, while the electrical resistivity was attributed to the strong blockage effect induced by grain boundaries and lattice distortions. The results lay a solid foundation for the development of advanced films with structural and functional properties combined in micro-/nano-electronic devices.

Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

PubMed

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

2016-06-20

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet

PubMed Central

Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

2016-01-01

We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd–Fe–B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd–Fe–B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd–Fe–B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

From amorphous to nanocrystalline: the effect of nanograins in amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films

DOE PAGES

Kearney, B. T.; Jugdersuren, B.; Queen, D. R.; ...

2017-12-28

Here, we have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R=H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fractionmore » increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few um deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering between silicon nanocrystals and the amorphous matrix.« less

From amorphous to nanocrystalline: the effect of nanograins in amorphous matrix on the thermal conductivity of hot-wire chemical-vapor deposited silicon films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kearney, B. T.; Jugdersuren, B.; Queen, D. R.

Here, we have measured the thermal conductivity of amorphous and nanocrystalline silicon films with varying crystalline content from 85K to room temperature. The films were prepared by the hot-wire chemical-vapor deposition, where the crystalline volume fraction is determined by the hydrogen (H2) dilution ratio to the processing silane gas (SiH4), R=H2/SiH4. We varied R from 1 to 10, where the films transform from amorphous for R < 3 to mostly nanocrystalline for larger R. Structural analyses show that the nanograins, averaging from 2 to 9nm in sizes with increasing R, are dispersed in the amorphous matrix. The crystalline volume fractionmore » increases from 0 to 65% as R increases from 1 to 10. The thermal conductivities of the two amorphous silicon films are similar and consistent with the most previous reports with thicknesses no larger than a few um deposited by a variety of techniques. The thermal conductivities of the three nanocrystalline silicon films are also similar, but are about 50-70% higher than those of their amorphous counterparts. The heat conduction in nanocrystalline silicon films can be understood as the combined contribution in both amorphous and nanocrystalline phases, where increased conduction through improved nanocrystalline percolation path outweighs increased interface scattering between silicon nanocrystals and the amorphous matrix.« less

A simple and low temperature process for super-hydrophilic rutile TiO 2 thin films growth

NASA Astrophysics Data System (ADS)

Mane, R. S.; Joo, Oh-Shim; Min, Sun-Ki; Lokhande, C. D.; Han, Sung-Hwan

2006-11-01

We investigate an environmentally friendly aqueous solution system for rutile TiO2 violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO2 with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO2 films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

Shock-induced microstructural response of mono- and nanocrystalline SiC ceramics

NASA Astrophysics Data System (ADS)

Branicio, Paulo S.; Zhang, Jingyun; Rino, José P.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya

2018-04-01

The dynamic behavior of mono- and nanocrystalline SiC ceramics under plane shock loading is revealed using molecular-dynamics simulations. The generation of shock-induced elastic compression, plastic deformation, and structural phase transformation is characterized at different crystallographic directions as well as on a 5-nm grain size nanostructure at 10 K and 300 K. Shock profiles are calculated in a wide range of particle velocities 0.1-6.0 km/s. The predicted Hugoniot agree well with experimental data. Results indicate the generation of elastic waves for particle velocities below 0.8-1.9 km/s, depending on the crystallographic direction. In the intermediate range of particle velocities between 2 and 5 km/s, the shock wave splits into an elastic precursor and a zinc blende-to-rock salt structural transformation wave, which is triggered by shock pressure over the ˜90 GPa threshold value. A plastic wave, with a strong deformation twinning component, is generated ahead of the transformation wave for shocks in the velocity range between 1.5 and 3 km/s. For particle velocities greater than 5-6 km/s, a single overdriven transformation wave is generated. Surprisingly, shocks on the nanocrystalline sample reveal the absence of wave splitting, and elastic, plastic, and transformation wave components are seamlessly connected as the shock strength is continuously increased. The calculated strengths 15.2, 31.4, and 30.9 GPa for ⟨001⟩, ⟨111⟩, and ⟨110⟩ directions and 12.3 GPa for the nanocrystalline sample at the Hugoniot elastic limit are in excellent agreement with experimental data.

High surface area nanocrystalline hausmannite synthesized by a solvent-free route

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrera-Miranda, Daniel; Ponrouch, Alexandre; Pons, Josefina

Highlights: ► High surface area Mn{sub 3}O{sub 4} nanoparticles obtained by a solvent-free low temperature route. ► 3,6,9-Trioxadecanoic acid allows to obtain nanocrystalline hausmannite. ► Tape casted electrodes show up to 300 mAh g{sup −1} capacity after more than 40 cycles at a C/3 rate. ► Upper cut off voltage strongly influences capacity retention upon cycling at high C rates. -- Abstract: Nanocrystalline high surface area Mn{sub 3}O{sub 4} powder was obtained at low temperature by a solvent-free route. The precursor was a mixture of manganese (II) acetate, 3,6,9-trioxadecanoic acid (TODA) and ammonium acetate that were intimately mixed by groundingmore » in an agate mortar. Nanocrystalline Mn{sub 3}O{sub 4} was obtained by thermal treatment at 120 °C. Powder X-ray diffraction, selected area electron diffraction, high resolution transmission electron microscopy, and Fourier transformed infrared characterization confirmed the formation of the hausmannite phase. The as-prepared mesoporous material has high specific surface area (120 m{sup 2} g{sup −1}). The performances of tape casted Mn{sub 3}O{sub 4} nanopowder electrodes were investigated as anode material for lithium ion batteries. High capacity values were achieved at diverse C rates. Capacity fading was found to be dependent on the upper cut off voltage, the presence of a plateau at 2.25 V vs. Li{sup +}/Li being detrimental for long term cyclability.« less

Exploring biosensor applications with cotton cellulose nanocrystalline protein and peptide conjugates

USDA-ARS?s Scientific Manuscript database

Sensor I: Nano-crystalline preparations were produced through acid hydrolysis and mechanical breakage of the cotton fibers from a scoured and bleached cotton fabric and a scoured and bleached, mercerized fabric, which was shown to produce cellulose I (NCI) and cellulose II (NCII) crystals respective...

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE PAGES

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman; ...

2018-02-13

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

CP/MAS ¹³C NMR study of pulp hornification using nanocrystalline cellulose as a model system.

PubMed

Idström, Alexander; Brelid, Harald; Nydén, Magnus; Nordstierna, Lars

2013-01-30

The hornification process of paper pulp was investigated using solid-state (13)C NMR spectroscopy. Nanocrystalline cellulose was used to serve as a model system of the crystalline parts of the fibrils in pulp fibers. Characterization of the nanocrystalline cellulose dimensions was carried out using scanning electron microscopy. The samples were treated by drying and wetting cycles prior to NMR analysis where the hornification phenomenon was recorded by spectral changes of the cellulose C-4 carbon signals. An increase of the crystalline signal and a decrease of the signals corresponding to the accessible amorphous domains were found for both paper pulp and nanocrystalline cellulose. These spectral changes grew stronger with repeating drying and wetting cycles. The results show that cellulose co-crystallization contribute to hornification. Another conclusion is that the surfaces of higher hydrophobicity in cellulose fibrils have an increased preference for aggregation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Rapid Polyol-Assisted Microwave Synthesis of Nanocrystalline LiFePO4/C Cathode for Lithium-Ion Batteries.

PubMed

Paul, Baboo Joseph; Gim, Jihyeon; Baek, Sora; Kang, Jungwon; Song, Jinju; Kim, Sungjin; Kim, Jaekook

2015-08-01

Nanocrystalline LiFePO4/C has been synthesized under a very short period of time (90 sec) using a polyol-assisted microwave heating synthesis technique. The X-ray diffraction (XRD) data indicates that the rapidly synthesized materials correspond to phase pure olivine. Post-annealing of the as-prepared sample at 600 °C in argon atmosphere yields highly crystalline LiFePO4/C. The morphology of the samples studied using scanning electron microscopy (SEM) reveals the presence of secondary particles formed from aggregation of primary particles in the range of 30-50 nm. Transmission electron microscopy (TEM) images reveal a thin carbon layer coating on the surface of the primary particle. The charge/discharge studies indicate that the as-prepared and annealed LiFePO4/C samples delivered initial discharge capacities of 126 and 160 mA h g-1, respectively, with good capacity retentions at 0.05 mA cm-2 current densities. The post-annealing process indeed improves the crystallinity of the LiFePO4 nanocrystals, which enhances the electrode performance of LiFePO4/C.

Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions

NASA Astrophysics Data System (ADS)

Taylor, Sean; Samokhvalov, Alexander

2017-03-01

Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3 is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3 at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3 was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3 is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.

Atomistic modeling of La 3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia

DOE PAGES

Zhang, Shenli; Sha, Haoyan; Castro, Ricardo H. R.; ...

2018-01-01

The effect of La 3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations.

Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

PubMed Central

Im, Owen; Li, Jian; Wang, Mian; Zhang, Lijie Grace; Keidar, Michael

2012-01-01

Background Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT), biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan). Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels. Methods Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells) using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT) and without a magnetic field (N-SWCNT) for improving bone regeneration. Results Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment. Conclusion This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite promising for further exploration for bone regeneration. PMID:22619545

Study of magnetic and electrical properties of nanocrystalline Mn doped NiO.

PubMed

Raja, S Philip; Venkateswaran, C

2011-03-01

Diluted Magnetic Semiconductors (DMS) are intensively explored in recent years for its applications in spintronics, which is expected to revolutionize the present day information technology. Nanocrystalline Mn doped NiO samples were prepared using chemical co-precipitation method with an aim to realize room temperature ferromagnetism. Phase formation of the samples was studied using X-ray diffraction-Rietveld analysis. Scanning electron microscopy and Energy dispersive X-ray analysis results reveal the nanocrystalline nature of the samples, agglomeration of the particles, considerable particle size distribution and the near stoichiometry. Thermomagnetic curves confirm the single-phase formation of the samples up to 1% doping of Mn. Vibrating Sample Magnetometer measurements indicate the absence of ferromagnetism at room temperature. This may be due to the low concentration of Mn2+ ions having weak indirect coupling with Ni2+ ions. The lack of free carriers is also expected to be the reason for the absence of ferromagnetism, which is in agreement with the results of resistivity measurements using impedance spectroscopy. Arrhenius plot shows the presence of two thermally activated regions and the activation energy for the nanocrystalline Mn doped sample was found to be greater than that of undoped NiO. This is attributed to the doping effect of Mn. However, the dielectric constant of the samples was found to be of the same order of magnitude very much comparable with that of undoped NiO.

Thermal desorption spectroscopy of high fluence irradiated ultrafine and nanocrystalline tungsten: helium trapping and desorption correlated with morphology

NASA Astrophysics Data System (ADS)

El-Atwani, O.; Taylor, C. N.; Frishkoff, J.; Harlow, W.; Esquivel, E.; Maloy, S. A.; Taheri, M. L.

2018-01-01

Microstructural changes due to displacement damage and helium desorption are two phenomena that occur in tungsten plasma facing materials in fusion reactors. Nanocrystalline metals are being investigated as radiation tolerant materials that can mitigate these microstructural changes and better trap helium along their grain boundaries. Here, we investigate the performance of three tungsten grades (nanocrystalline, ultrafine and ITER grade tungsten), exposed to a high fluence of 4 keV helium at both RT and 773 K, during a thermal desorption spectroscopy (TDS) experiment. An investigation of the microstructure in pre-and post-TDS sample sets was performed. The amount of desorbed helium was shown to be highest in the ITER grade tungsten and lowest in the nanocrystalline tungsten. Correlating the desorption spectra and the microstructure (grain boundaries decorated with nanopores and crack formation) and comparing with previous literature on coarse grained tungsten samples at similar irradiation and TDS conditions, revealed the importance of grain boundaries in trapping helium and limiting helium desorption up to a high temperature of 1350 K in agreement with transmission electron microscopy studies on helium irradiated tungsten which showed preferential and large facetted bubble formation along the grain boundaries in the nanocrystalline tungsten grade.

Thermal desorption spectroscopy of high fluence irradiated ultrafine and nanocrystalline tungsten: helium trapping and desorption correlated with morphology

DOE PAGES

El-Atwani, Osman; Taylor, Chase N.; Frishkoff, James; ...

2017-11-09

Here, microstructural changes due to displacement damage and helium desorption are two phenomena that occur in tungsten plasma facing materials in fusion reactors. Nanocrystalline metals are being investigated as radiation tolerant materials that can mitigate these microstructural changes and better trap helium along their grain boundaries. Here, we investigate the performance of three tungsten grades (nanocrystalline, ultrafine and ITER grade tungsten), exposed to a high fluence of 4 keV helium at both RT and 773 K, during a thermal desorption spectroscopy (TDS) experiment. An investigation of the microstructure in pre-and post-TDS sample sets was performed. The amount of desorbed heliummore » was shown to be highest in the ITER grade tungsten and lowest in the nanocrystalline tungsten. Correlating the desorption spectra and the microstructure (grain boundaries decorated with nanopores and crack formation) and comparing with previous literature on coarse grained tungsten samples at similar irradiation and TDS conditions, revealed the importance of grain boundaries in trapping helium and limiting helium desorption up to a high temperature of 1350 K in agreement with transmission electron microscopy studies on helium irradiated tungsten which showed preferential and large facetted bubble formation along the grain boundaries in the nanocrystalline tungsten grade.« less

Alternating current transport and dielectric relaxation of nanocrystalline graphene oxide

NASA Astrophysics Data System (ADS)

Zedan, I. T.; El-Menyawy, E. M.

2018-07-01

Graphene oxide (GO) has been synthesized from natural graphite using modified Hummer's method and is subjected to sonication for 1 h. X-ray diffraction (XRD) showed that the prepared GO has nanocrystalline structure with particle size of about 5 nm and high-resolution transmission electron microscope showed that it had a layered structure. The nanocrystalline GO powder was pressed as a disk and the alternating current (AC) electrical conductivity, σAC, and dielectric properties have been investigated in the frequency range 50Hz-5 MHz and temperature range 298-523K using parallel plate spectroscopic technique. Analysis of σ AC as a function of frequency shows that the relation follows Jonscher's universal law with frequency exponent decreases with increasing temperature in which the correlated barrier hopping model is applicable to describe the behavior. The dielectric constant and dielectric loss are studied as functions of frequency and temperature. The dielectric modulus formalism is used for describing the relaxation process in which the relaxation time and its activation energy were evaluated.

Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

New atom probe approaches to studying segregation in nanocrystalline materials.

PubMed

Samudrala, S K; Felfer, P J; Araullo-Peters, V J; Cao, Y; Liao, X Z; Cairney, J M

2013-09-01

Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. Copyright © 2013 Elsevier B.V. All rights reserved.

Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, F. B.; Jing, B.; Cui, Y.

2015-04-15

The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond filmmore » are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.« less

Structural analysis of nanocrystalline ZnTe alloys synthesized by melt quenching technique

NASA Astrophysics Data System (ADS)

Singh, Harinder; Singh, Tejbir; Thakur, Anup; Sharma, Jeewan

2018-05-01

Nanocrystalline ZnxTe100-x (x=0, 5, 20, 30, 40, 50) alloys have been synthesized using melt quenching technique. Energy-dispersive X-Ray spectroscopy (EDS) has been used to verify the elemental composition of samples. Various absorption modes are recorded from Fourier transform infrared spectroscopy (FTIR) confirming the formation of ZnTe. The structural study has been performed using X-Ray Diffraction (XRD) method. All synthesized samples have been found to be nanocrystalline in nature with average crystallite size in the range from 49.3 nm to 77.1 nm. Results have shown that Zn0Te100 exhibits hexagonal phase that transforms into a cubic ZnTe phase as the amount of zinc is increased. Pure ZnTe phase has been obtained for x = 50. The texture coefficient (Tc) has been calculated to find the prominent orientations of different planes.

Controllable nonlinear refraction characteristics in hydrogenated nanocrystalline silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, D. Q.; Ye, Q. H.; Shen, W. Z., E-mail: wzshen@sjtu.edu.cn

2014-02-07

Nonlinear refraction (NLR) of hydrogenated nanocrystalline silicon (nc-Si:H) has been investigated through the close aperture Z-scan method. We demonstrate a significant NLR and a unique feature of controllable NLR characteristics between saturable and Kerr NLR with the incident photon energy. We numerically evaluate the proportion of these two mechanisms in different wavelengths by a modified NLR equation. The band tail of nc-Si:H appears to play a crucial role in such NLR responses.

Nanocrystalline SiC film thermistors for cryogenic applications

NASA Astrophysics Data System (ADS)

Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

2018-02-01

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

Ordered mesoporous MFe(2)O(4) (M = Co, Cu, Mg, Ni, Zn) thin films with nanocrystalline walls, uniform 16 nm diameter pores and high thermal stability: template-directed synthesis and characterization of redox active trevorite.

PubMed

Haetge, Jan; Suchomski, Christian; Brezesinski, Torsten

2010-12-20

In this paper, we report on ordered mesoporous NiFe(2)O(4) thin films synthesized via co-assembly of hydrated ferric nitrate and nickel chloride with an amphiphilic diblock copolymer, referred to as KLE. We establish that the NiFe(2)O(4) samples are highly crystalline after calcination at 600 °C, and that the conversion of the amorphous inorganic framework comes at little cost to the ordering of the high quality cubic network of pores averaging 16 nm in diameter. We further show that the synthesis method employed in this work can be readily extended to other ferrites, such as CoFe(2)O(4), CuFe(2)O(4), MgFe(2)O(4), and ZnFe(2)O(4), which could pave the way for innovative device design. While this article focuses on the self-assembly and characterization of these materials using various state-of-the-art techniques, including electron microscopy, grazing incidence small-angle X-ray scattering (GISAXS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), as well as UV-vis and Raman spectroscopy, we also examine the electrochemical properties and show the benefits of combining a continuous mesoporosity with nanocrystalline films. KLE-templated NiFe(2)O(4) electrodes exhibit reasonable levels of lithium ion storage at short charging times which stem from facile pseudocapacitance.

Rapid fabrication of mesoporous TiO2 thin films by pulsed fibre laser for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hadi, Aseel; Alhabradi, Mansour; Chen, Qian; Liu, Hong; Guo, Wei; Curioni, Michele; Cernik, Robert; Liu, Zhu

2018-01-01

In this paper we demonstrate for the first time that a fibre laser with a wavelength of 1070 nm and a pulse width of milliseconds can be applied to generate mesoporous nanocrystalline (nc) TiO2 thin films on ITO coated glass in ambient atmosphere, by complete vaporisation of organic binder and inter-connection of TiO2 nanoparticles, without thermally damaging the ITO layer and the glass substrate. The fabrication of the mesoporous TiO2 thin films was achieved by stationary laser beam irradiation of 1 min. The dye sensitized solar cell (DSSC) with the laser-sintered TiO2 photoanode reached higher power conversion efficiency (PCE) of 3.20% for the TiO2 film thickness of 6 μm compared with 2.99% for the furnace-sintered. Electrochemical impedance spectroscopy studies revealed that the laser sintering under the optimised condition effectively decreased charge transfer resistance and increased electron lifetime of the TiO2 thin films. The use of the fibre laser with over 40% wall-plug efficiency offers an economically-feasible, industrial viable solution to the major challenge of rapid fabrication of large scale, mass production of mesoporous metal oxide thin film based solar energy systems, potentially for perovskite and monolithic tandem solar cells, in the future.

Fabrication and characterization of nanowalls CdS/dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Abdulelah, Haider; Ali, Basil; Mahdi, M. A.; Hassan, J. J.; Al-Taay, H. F.; Jennings, P.

2017-06-01

A microwave assisted chemical bath deposition (MA-CBD) was adopted to fabricate nanowalls CdS nanocrystalline thin film. Nanomaterials (such as nanowalls structure) have attracted significant attention due to their fascinating properties and unique applications, especially in optoelectronic nanodevices. Here we describe the fabrication of dye sensitized solar cells (DSSCs) based nanowalls cadmium sulfide (CdS) nanocrystalline thin films. The surface morphology, crystalline structure, and optical properties of the prepared nanocrystalline thin films are investigated. Rhodamine B, Malachite green, Eosin methylene blue, and Cresyl violet perchlorate dyes are used to fabricate the DSSCS devices. Current-voltage (I-V) characteristics show that the nanowall CdS/Eosin methylene blue device is the highest conversion efficiency of 0.89% under 100 mW/cm2. However, heat treatment of the fabricated solar cells causes significant enhancement in the output of all devices.

The role of nanocrystalline binder metallic coating into WC after additive manufacturing

NASA Astrophysics Data System (ADS)

Cavaleiro, A. J.; Fernandes, C. M.; Farinha, A. R.; Gestel, C. V.; Jhabvala, J.; Boillat, E.; Senos, A. M. R.; Vieira, M. T.

2018-01-01

Tungsten carbide with microsized particle powders are commonly used embedded in a tough binder metal. The application of these composites is not limited to cutting tools, WC based material has been increasingly used in gaskets and other mechanical parts with complex geometries. Consequently, additive manufacturing processes as Selective Laser Sintering (SLS) might be the solution to overcome some of the manufacturing problems. However, the use of SLS leads to resolve the problems resulting from difference of physical properties between tungsten carbide and the metallic binder, such as laser absorbance and thermal conductivity. In this work, an original approach of powder surface modification was considered to prepare WC-metal composite powders and overcome these constraints, consisting on the sputter-coating of the WC particle surfaces with a nanocrystalline thin film of metallic binder material (stainless steel). The coating improves the thermal behavior and rheology of the WC particles and, at the same time, ensures a binder homogenous distribution. The feasibility of the SLS technology as manufacturing process for WC powder sputter-coated with 13 wt% stainless steel AISI 304L was explored with different laser power and scanning speed parameters. The SLS layers were characterized regarding elemental distribution, phase composition and morphology, and the results are discussed emphasizing the role of the coating on the consolidation process.

Synthesis of nanocrystalline CdS thin film by SILAR and their characterization

NASA Astrophysics Data System (ADS)

Mukherjee, A.; Satpati, B.; Bhattacharyya, S. R.; Ghosh, R.; Mitra, P.

2015-01-01

Cadmium sulphide (CdS) thin film was prepared by successive ion layer adsorption and reaction (SILAR) technique using ammonium sulphide as anionic precursor. Characterization techniques of XRD, SEM, TEM, FTIR and EDX were utilized to study the microstructure of the films. Structural characterization by x-ray diffraction reveals the polycrystalline nature of the films. Cubic structure is revealed from X-ray diffraction and selected area diffraction (SAD) patterns. The particle size estimated using X-ray line broadening method is approximately 7 nm. Instrumental broadening was taken into account while particle size estimation. TEM shows CdS nanoparticles in the range 5-15 nm. Elemental mapping using EFTEM reveals good stoichiometric composition of CdS. Characteristic stretching vibration mode of CdS was observed in the absorption band of FTIR spectrum. Optical absorption study exhibits a distinct blue shift in band gap energy value of about 2.56 eV which confirms the size quantization.

Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

NASA Astrophysics Data System (ADS)

Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

2011-11-01

The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

Field electron emission enhancement in lithium implanted and annealed nitrogen-incorporated nanocrystalline diamond films

NASA Astrophysics Data System (ADS)

Sankaran, K. J.; Srinivasu, K.; Yeh, C. J.; Thomas, J. P.; Drijkoningen, S.; Pobedinskas, P.; Sundaravel, B.; Leou, K. C.; Leung, K. T.; Van Bael, M. K.; Schreck, M.; Lin, I. N.; Haenen, K.

2017-06-01

The field electron emission (FEE) properties of nitrogen-incorporated nanocrystalline diamond films were enhanced due to Li-ion implantation/annealing processes. Li-ion implantation mainly induced the formation of electron trap centers inside diamond grains, whereas post-annealing healed the defects and converted the a-C phase into nanographite, forming conduction channels for effective transport of electrons. This resulted in a high electrical conductivity of 11.0 S/cm and enhanced FEE performance with a low turn-on field of 10.6 V/μm, a high current density of 25.5 mA/cm2 (at 23.2 V/μm), and a high lifetime stability of 1,090 min for nitrogen incorporated nanocrystalline diamond films.

Analysis of Short and Long Range Atomic Order in Nanocrystalline Diamonds with Application of Powder Diffractometry

NASA Technical Reports Server (NTRS)

Palosz, B.; Grzanka, E.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Neuefiend, J.; Weber, H.-P.; Proffen, T.; VonDreele, R.; Palosz, W.;

Production of biofuel from waste cooking palm oil using nanocrystalline zeolite as catalyst: process optimization studies.

PubMed

Taufiqurrahmi, Niken; Mohamed, Abdul Rahman; Bhatia, Subhash

2011-11-01

The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 °C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 °C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%. Copyright © 2011 Elsevier Ltd. All rights reserved.

Acanthite–argentite transformation in nanocrystalline silver sulfide and the Ag{sub 2}S/Ag nanoheterostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gusev, A. I., E-mail: gusev@ihim.uran.ru; Sadovnikov, S. I.

Nanocrystalline acanthite-structured silver sulfide of the monoclinic structure and a Ag{sub 2}S/Ag nanoheterostructure are produced. The high-temperature X-ray diffraction technique is applied to the in situ study of the (acanthite α-Ag{sub 2}S)–(argentite β-Ag{sub 2}S) phase transformation in nanocrystalline silver sulfide. The crystal structure of argentite is refined, and it is found that the content of vacant sites in the metal sublattice of argentite exceeds 92%. A model of a resistive switch, whose operation is based on the reversible acanthite–argentite transformation in a Ag{sub 2}S/Ag heterostructure, is considered.

Oxidation resistant nanocrystalline MCrAl(Y) coatings and methods of forming such coatings

DOEpatents

Cheruvu, Narayana S.; Wei, Ronghua

2014-07-29

The present disclosure relates to an oxidation resistant nanocrystalline coating and a method of forming an oxidation resistant nanocrystalline coating. An oxidation resistant coating comprising an MCrAl(Y) alloy may be deposited on a substrate, wherein M, includes iron, nickel, cobalt, or combinations thereof present greater than 50 wt % of the MCrAl(Y) alloy, chromium is present in the range of 15 wt % to 30 wt % of the MCrAl(Y) alloy, aluminum is present in the range of 6 wt % to 12 wt % of the MCrAl(Y) alloy and yttrium, is optionally present in the range of 0.1 wt % to 0.5 wt % of the MCrAl(Y) alloy. In addition, the coating may exhibit a grain size of 200 nm or less as deposited.

On the thermal stability of physical vapor deposited oxide-hardened nanocrystalline gold thin films

DOE PAGES

Argibay, Nicolas; Mogonye, J. E.; Michael, Joseph R.; ...

2015-04-08

We describe a correlation between electrical resistivity and grain size for PVD synthesized polycrystalline oxide-hardened metal-matrix thin films in oxide-dilute (<5 vol. % oxide phase) compositions. The correlation is based on the Mayadas-Shatzkes (M-S) electron scattering model, predictive of grain size evolution as a function of composition in the oxide-dilute regime for 2 μm thick Au-ZnO films. We describe a technique to investigate grain boundary (GB) mobility and the thermal stability of GBs based on in situelectrical resistivity measurements during annealing experiments, interpreted using a combination of the M-S model and the Michels et al. model describing solute drag stabilizedmore » grain growth kinetics. Using this technique, activation energy and pre-exponential Arrhenius parameter values of E a = 21.6 kJ/mol and A o = 2.3 × 10 -17 m 2/s for Au-1 vol. % ZnO and E a =12.7 kJ/mol and A o = 3.1 × 10 -18 m 2/s for Au-2 vol.% ZnO were determined. In the oxide-dilute regime, the grain size reduction of the Au matrix yielded a maximum hardness of 2.6 GPa for 5 vol. % ZnO. A combined model including percolation behavior and grain refinement is presented that accurately describes the composition dependent change in electrical resistivity throughout the entire composition range for Au-ZnO thin films. As a result, the proposed correlations are supported by microstructural characterization using transmission electron microscopy and electron diffraction mapping for grain size determination.« less

Water-soluble nanocrystalline cellulose films with highly transparent and oxygen barrier properties

NASA Astrophysics Data System (ADS)

Cheng, Shaoling; Zhang, Yapei; Cha, Ruitao; Yang, Jinliang; Jiang, Xingyu

2015-12-01

By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food.By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07647a

Surface grafting of reduced graphene oxide using nanocrystalline cellulose via click reaction

NASA Astrophysics Data System (ADS)

Kabiri, Roya; Namazi, Hassan

2014-07-01

Reduced graphene oxide (RGO) sheet was functionalized with nanocrystalline cellulose (NCC) via click coupling between azide-functionalized graphene oxide (GO-N3) and terminal propargyl-functionalized nanocrystalline cellulose (PG-NCC). First, the reactive azide groups were introduced on the surface of GO with azidation of 2-chloroethyl isocyanate-treated graphene oxide (GO-Cl). Then, the resulted compounds were reacted with PG-NCC utilizing copper-catalyzed azide-alkyne cycloaddition. During the click reaction, GO was simultaneously reduced to graphene. The coupling was confirmed by Fourier transform infrared, Raman, DEPT135, and 13C NMR spectroscopy, and the complete exfoliation of graphene in the NCC matrix was confirmed with X-ray diffraction measurement. The degree of functionalization from the gradual mass loss of RGO-NCC suggests that around 23 mass % has been functionalized covalently. The size of both NCC and GO was found to be in nanometric range, which decreased after click reaction.

Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing.

PubMed

Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

2016-08-19

We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson-Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm(-1) K(-2)), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance.

Smectic C liquid crystal growth through surface orientation by ZnxCd1-xSe thin films

NASA Astrophysics Data System (ADS)

Katranchev, B.; Petrov, M.; Bineva, I.; Levi, Z.; Mineva, M.

2012-12-01

A smectic C liquid crystal (LC) texture, consisting of distinct local single crystals (DLSCs) was grown using predefined orientation of ternary nanocrystalline thin films of ZnxCd1-xSe. The surface morphology and orientation features of the ZnxCd1-xSe films were investigated by AFM measurements and micro-texture polarization analysis. The ZnxCd1-xSe surface causes a substantial enlargement of the smectic C DLSCs and induction of a surface bistable state. The specific character of the morphology of this coating leads to the decrease of the corresponding anchoring energy. Two new chiral states, not typical for this LC were indicated. The physical mechanism providing these new effects is presented.

Pulse I-V characterization of a nano-crystalline oxide device with sub-gap density of states

NASA Astrophysics Data System (ADS)

Kim, Taeho; Hur, Ji-Hyun; Jeon, Sanghun

2016-05-01

Understanding the charge trapping nature of nano-crystalline oxide semiconductor thin film transistors (TFTs) is one of the most important requirements for their successful application. In our investigation, we employed a fast-pulsed I-V technique for understanding the charge trapping phenomenon and for characterizing the intrinsic device performance of an amorphous/nano-crystalline indium-hafnium-zinc-oxide semiconductor TFT with varying density of states in the bulk. Because of the negligible transient charging effect with a very short pulse, the source-to-drain current obtained with the fast-pulsed I-V measurement was higher than that measured by the direct-current characterization method. This is because the fast-pulsed I-V technique provides a charge-trap free environment, suggesting that it is a representative device characterization methodology of TFTs. In addition, a pulsed source-to-drain current versus time plot was used to quantify the dynamic trapping behavior. We found that the charge trapping phenomenon in amorphous/nano-crystalline indium-hafnium-zinc-oxide TFTs is attributable to the charging/discharging of sub-gap density of states in the bulk and is dictated by multiple trap-to-trap processes.

Pulse I-V characterization of a nano-crystalline oxide device with sub-gap density of states.

PubMed

Kim, Taeho; Hur, Ji-Hyun; Jeon, Sanghun

2016-05-27

Understanding the charge trapping nature of nano-crystalline oxide semiconductor thin film transistors (TFTs) is one of the most important requirements for their successful application. In our investigation, we employed a fast-pulsed I-V technique for understanding the charge trapping phenomenon and for characterizing the intrinsic device performance of an amorphous/nano-crystalline indium-hafnium-zinc-oxide semiconductor TFT with varying density of states in the bulk. Because of the negligible transient charging effect with a very short pulse, the source-to-drain current obtained with the fast-pulsed I-V measurement was higher than that measured by the direct-current characterization method. This is because the fast-pulsed I-V technique provides a charge-trap free environment, suggesting that it is a representative device characterization methodology of TFTs. In addition, a pulsed source-to-drain current versus time plot was used to quantify the dynamic trapping behavior. We found that the charge trapping phenomenon in amorphous/nano-crystalline indium-hafnium-zinc-oxide TFTs is attributable to the charging/discharging of sub-gap density of states in the bulk and is dictated by multiple trap-to-trap processes.

Properties of Hydrogen Sulfide Sensors Based on Thin Films of Tin Dioxide and Tungsten Trioxide

NASA Astrophysics Data System (ADS)

Sevastianov, E. Yu.; Maksimova, N. K.; Chernikov, E. V.; Sergeichenko, N. V.; Rudov, F. V.

2016-12-01

The effect of hydrogen sulfide in the concentration range of 0-100 ppm on the characteristics of thin films of tin dioxide and tungsten trioxide obtained by the methods of magnetron deposition and modified with gold in the bulk and on the surface is studied. The impurities of antimony and nickel have been additionally introduced into the SnO2 bulk. An optimal operating temperature of sensors 350°C was determined, at which there is a satisfactory correlation between the values of the response to H2S and the response time. Degradation of the sensor characteristics is investigated in the long-term ( 0.5-1.5 years) tests at operating temperature and periodic exposure to hydrogen sulfide, as well as after conservation of samples in the laboratory air. It is shown that for the fabrication of H2S sensors, the most promising are thin nanocrystalline Au/WO3:Au films characterized by a linear concentration dependence of the response and high stability of parameters during exploitation.

Deposition of Nanostructured CdS Thin Films by Thermal Evaporation Method: Effect of Substrate Temperature

PubMed Central

Memarian, Nafiseh; Rozati, Seyeed Mohammad; Concina, Isabella

2017-01-01

Nanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10−5 Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11–2.2 × 104 Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application. PMID:28773133

Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Saber, Mostafa

Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth

Transparent nanocrystalline diamond coatings and devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sumant, Anirudha V.; Khan, Adam

2017-08-22

A method for coating a substrate comprises producing a plasma ball using a microwave plasma source in the presence of a mixture of gases. The plasma ball has a diameter. The plasma ball is disposed at a first distance from the substrate and the substrate is maintained at a first temperature. The plasma ball is maintained at the first distance from the substrate, and a diamond coating is deposited on the substrate. The diamond coating has a thickness. Furthermore, the diamond coating has an optical transparency of greater than about 80%. The diamond coating can include nanocrystalline diamond. The microwavemore » plasma source can have a frequency of about 915 MHz.« less

Room Temperature Tunable Multiferroic Properties in Sol-Gel-Derived Nanocrystalline Sr(Ti1−xFex)O3−δ Thin Films

PubMed Central

Wang, Yi-Guang; Liu, Qiu-Xiang; Jiang, Yan-Ping; Jiang, Li-Li

2017-01-01

Sr(Ti1−xFex)O3−δ (0 ≤ x ≤ 0.2) thin films were grown on Si(100) substrates with LaNiO3 buffer-layer by a sol-gel process. Influence of Fe substitution concentration on the structural, ferroelectric, and magnetic properties, as well as the leakage current behaviors of the Sr(Ti1−xFex)O3−δ thin films, were investigated by using the X-ray diffractometer (XRD), atomic force microscopy (AFM), the ferroelectric test system, and the vibrating sample magnetometer (VSM). After substituting a small amount of Ti ion with Fe, highly enhanced ferroelectric properties were obtained successfully in SrTi0.9Ti0.1O3−δ thin films, with a double remanent polarization (2Pr) of 1.56, 1.95, and 9.14 μC·cm−2, respectively, for the samples were annealed in air, oxygen, and nitrogen atmospheres. The leakage current densities of the Fe-doped SrTiO3 thin films are about 10−6–10−5 A·cm−2 at an applied electric field of 100 kV·cm−1, and the conduction mechanism of the thin film capacitors with various Fe concentrations has been analyzed. The ferromagnetic properties of the Sr(Ti1−xFex)O3−δ thin films have been investigated, which can be correlated to the mixed valence ions and the effects of the grain boundary. The present results revealed the multiferroic nature of the Sr(Ti1−xFex)O3−δ thin films. The effect of the annealing environment on the room temperature magnetic and ferroelectric properties of Sr(Ti0.9Fe0.1)O3−δ thin films were also discussed in detail. PMID:28885579

Biomimetic nanocrystalline apatites: Emerging perspectives in cancer diagnosis and treatment.

PubMed

Al-Kattan, Ahmed; Girod-Fullana, Sophie; Charvillat, Cédric; Ternet-Fontebasso, Hélène; Dufour, Pascal; Dexpert-Ghys, Jeannette; Santran, Véronique; Bordère, Julie; Pipy, Bernard; Bernad, José; Drouet, Christophe

2012-02-14

Nanocrystalline calcium phosphate apatites constitute the mineral part of hard tissues, and the synthesis of biomimetic analogs is now well-mastered at the lab-scale. Recent advances in the fine physico-chemical characterization of these phases enable one to envision original applications in the medical field along with a better understanding of the underlying chemistry and related pharmacological features. In this contribution, we specifically focused on applications of biomimetic apatites in the field of cancer diagnosis or treatment. We first report on the production and first biological evaluations (cytotoxicity, pro-inflammatory potential, internalization by ZR-75-1 breast cancer cells) of individualized luminescent nanoparticles based on Eu-doped apatites, eventually associated with folic acid, for medical imaging purposes. We then detail, in a first approach, the preparation of tridimensional constructs associating nanocrystalline apatite aqueous gels and drug-loaded pectin microspheres. Sustained releases of a fluorescein analog (erythrosin) used as model molecule were obtained over 7 days, in comparison with the ceramic or microsphere reference compounds. Such systems could constitute original bone-filling materials for in situ delivery of anticancer drugs. Copyright © 2011 Elsevier B.V. All rights reserved.

High oxygen nanocomposite barrier films based on xylan and nanocrystalline cellulose

Treesearch

Amit Saxena; Thomas J. Elder; Jeffrey Kenvin; Arthur J. Ragauskas

2010-01-01

The goal of this work is to produce nanocomposite film with low oxygen permeability by casting an aqueous solution containing xylan, sorbitol and nanocrystalline cellulose. The morphology of the resulting nanocomposite films was examined by scanning electron microscopy and atomic force microscopy which showed that control films containing xylan and sorbitol had a more...

Nanodimensional and Nanocrystalline Apatites and Other Calcium Orthophosphates in Biomedical Engineering, Biology and Medicine

PubMed Central

Dorozhkin, Sergey V.

2009-01-01

Recent developments in biomineralization have already demonstrated that nanosized particles play an important role in the formation of hard tissues of animals. Namely, the basic inorganic building blocks of bones and teeth of mammals are nanodimensional and nanocrystalline calcium orthophosphates (in the form of apatites) of a biological origin. In mammals, tens to hundreds nanocrystals of a biological apatite were found to be combined into self-assembled structures under the control of various bioorganic matrixes. In addition, the structures of both dental enamel and bones could be mimicked by an oriented aggregation of nanosized calcium orthophosphates, determined by the biomolecules. The application and prospective use of nanodimensional and nanocrystalline calcium orthophosphates for a clinical repair of damaged bones and teeth are also known. For example, a greater viability and a better proliferation of various types of cells were detected on smaller crystals of calcium orthophosphates. Thus, the nanodimensional and nanocrystalline forms of calcium orthophosphates have a great potential to revolutionize the field of hard tissue engineering starting from bone repair and augmentation to the controlled drug delivery devices. This paper reviews current state of knowledge and recent developments of this subject starting from the synthesis and characterization to biomedical and clinical applications. More to the point, this review provides possible directions of future research and development.

Photocatalytic degradation of Orange G dye under solar light using nanocrystalline semiconductor metal oxide.

PubMed

Thennarasu, G; Kavithaa, S; Sivasamy, A

2011-08-01

The photocatalytic degradation of Orange G (OG) dye has been investigated using synthesised nanocrystalline ZnO as a photocatalyst and sunlight as the irradiation source. The formation of ZnO prepared from its precursor was confirmed through FT-IR and powder X-ray diffraction analyses. Surface morphology was characterised by scanning electron microscope and transmission electron microscope analysis. Band gap energy of synthesised nanocrystalline ZnO was calculated using diffuse reflectance spectroscopy (DRS). Different experimental parameters such as effects of pH, dye concentrations and mass of catalyst were standardised in order to achieve complete degradation of the dye molecules under solar light irradiation. The kinetics of oxidation of OG was also studied. The complete degradation of OG was evident after 90 min of irradiation at an initial pH of 6.86. The degradation of OG was confirmed by UV-Visible spectrophotometer, high-pressure liquid chromatography, ESI-Mass and chemical oxygen demand analyses. The adsorption of dye onto catalytic surface was analysed employing model equations such as Langmuir and Freundlich isotherms, and it was found that the Langmuir isotherm model best fitted the adsorption data. The solar photodegradation of OG followed pseudo-first-order kinetics. HPLC and ESI-Mass analyses of the degraded samples suggested that the dye molecules were readily degraded under solar irradiation with nanocrystalline ZnO.

Influence of temperature on AC conductivity of nanocrystalline CuAlO2

NASA Astrophysics Data System (ADS)

Prakash, T.

2012-07-01

Nanocrystalline CuAlO2 was synthesized by mechanical alloying of Cu2O and α-Al2O3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies ( f co ). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

Synthesis of nanocrystalline TiO 2 in toluene by a solvothermal route

NASA Astrophysics Data System (ADS)

Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Tae Chung, Su; Son, Se-Mo

2003-07-01

A solvothermal synthetic method to TiO 2 nanoparticles has been investigated in toluene solutions with titanium isopropoxide (TIP) as precursor. Weight ratios of precursor to solvent prepared in the mixture are 5/100, 10/100, 20/100, 30/100 and 40/100. At the weight ratio of 10/100, 20/100 and 30/100, TiO 2 nanocrystalline particles were obtained after synthesis at 250°C for 3 h in an autoclave. X-ray diffraction and tranmission electron microscopy shows that the product has uniform anatase structure with average particle size below 20 nm. As the composition of TIP in the solution increases, the particle size of TiO 2 powder tends to increase. At 5/100 and 40/100, however, pale yellow colloidal solution is obtained after synthesis and crystalline phase of TiO 2 is not produced. The specific surface area of the TiO 2 nanocrystalline powder was also investigated using BET surface area analyzer.

Host-Sensitized and Tunable Luminescence of GdNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Tm3+) Nanocrystalline Phosphors with Abundant Color.

PubMed

Liu, Xiaoming; Chen, Chen; Li, Shuailong; Dai, Yuhua; Guo, Huiqin; Tang, Xinghua; Xie, Yu; Yan, Liushui

2016-10-17

Up to now, GdNbO 4 has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO 4 nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors were synthesized by a Pechini-type sol-gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO 4 nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO 4 :Ln 3+ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f-f transitions of the doping Eu 3+ , Tb 3+ , and Tm 3+ ions. The luminescence color of GdNbO 4 :Ln 3+ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO 4 host lattice. A single-phase white-light-emission has been realized in Eu 3+ /Tb 3+ /Tm 3+ triply doped GdNbO 4 nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) are updated.

Towards lightweight and flexible high performance nanocrystalline silicon solar cells through light trapping and transport layers

NASA Astrophysics Data System (ADS)

Gray, Zachary R.

This thesis investigates ways to enhance the efficiency of thin film solar cells through the application of both novel nano-element array light trapping architectures and nickel oxide hole transport/electron blocking layers. Experimental results independently demonstrate a 22% enhancement in short circuit current density (JSC) resulting from a nano-element array light trapping architecture and a ˜23% enhancement in fill factor (FF) and ˜16% enhancement in open circuit voltage (VOC) resulting from a nickel oxide transport layer. In each case, the overall efficiency of the device employing the light trapping or transport layer was superior to that of the corresponding control device. Since the efficiency of a solar cell scales with the product of JSC, FF, and VOC, it follows that the results of this thesis suggest high performance thin film solar cells can be realized in the event light trapping architectures and transport layers can be simultaneously optimized. The realizations of these performance enhancements stem from extensive process optimization for numerous light trapping and transport layer fabrication approaches. These approaches were guided by numerical modeling techniques which will also be discussed. Key developments in this thesis include (1) the fabrication of nano-element topographies conducive to light trapping using various fabrication approaches, (2) the deposition of defect free nc-Si:H onto structured topographies by switching from SiH4 to SiF 4 PECVD gas chemistry, and (3) the development of the atomic layer deposition (ALD) growth conditions for NiO. Keywords: light trapping, nano-element array, hole transport layer, electron blocking layer, nickel oxide, nanocrystalline silicon, aluminum doped zinc oxide, atomic layer deposition, plasma enhanced chemical vapor deposition, electron beam lithography, ANSYS HFSS.

TiCN thin films grown by reactive crossed beam pulsed laser deposition

NASA Astrophysics Data System (ADS)

Escobar-Alarcón, L.; Camps, E.; Romero, S.; Muhl, S.; Camps, I.; Haro-Poniatowski, E.

2010-12-01

In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration, titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium and graphite targets in an Ar/N2 atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa. With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence on the carbon target.

Nature of Dielectric Properties, Electric Modulus and AC Electrical Conductivity of Nanocrystalline ZnIn2Se4 Thin Films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.

2018-02-01

The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.

Nanocrystalline zirconia can be amorphized by ion irradiation.

PubMed

Meldrum, A; Boatner, L A; Ewing, R C

2002-01-14

Nanocrystalline composites are finding applications in high-radiation environments due to their excellent mechanical and electronic properties. We show, however, that at the smallest particle sizes, radiation damage effects can be so strongly enhanced that under the right conditions, materials that have never been made amorphous can become highly susceptible to irradiation-induced amorphization. Because light-weight, high-strength nanocomposites are potential materials for spacecraft shielding and sensor systems, these fundamental results have significant implications for the design and selection of materials to be used in environments where a large ion flux will be encountered.

Effect of tungsten (W) on structural and magnetic properties of electroplated NiFe thin films for MEMS applications

NASA Astrophysics Data System (ADS)

Kannan, R.; Devaki, P.; Premkumar, P. S.; Selvambikai, M.

2018-04-01

Electrodeposition of nanocrystalline NiFe and NiFeW thin films were carried out from ammonium citrate bath at a constant current density and controlled pH of 8 by varying the bath temperature from 40 °C to 70 °C. The surface morphology and chemical composition of the electrodeposited NiFe and NiFeW soft magnetic thin films were studied by using SEM and EDAX. The SEM micrographs of the films coated at higher electrodeposited bath temperature have no micro cracks and also the films have more uniform surface morphology. The existence of crystalline nature of the coated films were analysed by XRD. The presence of predominant peaks in x-ray diffraction pattern (compared with JCPDS data) reveal that the average crystalline size was in the order of few tens of nano meters. The magnetic properties such as coercivity, saturation magnetization and magnetic flux density have been calculated from vibrating sample magnetometer analysis. The VSM result shows that the NiFeW thin film synthesised at 70 °C exhibit the lower coercivity with higher saturation magnetization. The hardness and adhesion of the electroplated films have been investigated. Reasons for variation in magnetic properties and structural characteristics are also discussed. The electroplated NiFe and NiFeW thin films can be used for Micro Electro Mechanical System (MEMS) applications due to their excellent soft magnetic behaviour.

Performance analyses of Schottky diodes with Au/Pd contacts on n-ZnO thin films as UV detectors

NASA Astrophysics Data System (ADS)

Varma, Tarun; Periasamy, C.; Boolchandani, Dharmendar

2017-12-01

In this paper, we report fabrication and performance analyses of UV detectors based on ZnO thin film Schottky diodes with Au and Pd contacts. RF magnetron sputtering technique has been used to deposit the nano-crystalline ZnO thin film, at room temperature. Characterization techniques such as XRD, AFM and SEM provided valuable information related to the micro-structural & optical properties of the thin film. The results show that the prepared thin film has good crystalline orientation and minimal surface roughness, with an optical bandgap of 3.1 eV. I-V and C-V characteristics were evaluated that indicate non-linear behaviour of the diodes with rectification ratios (IF/IR) of 19 and 427, at ± 4 V, for Au/ZnO and Pd/ZnO Schottky diodes, respectively. The fabricated Schottky diodes when exposed to a UV light of 365 nm wavelength, at an applied bias of -2 V, exhibited responsivity of 10.16 and 22.7 A/W, for Au and Pd Schottky contacts, respectively. The Pd based Schottky photo-detectors were found to exhibit better performance with superior values of detectivity and photoconductive gain of 1.95 × 1010 cm Hz0.5/W & 77.18, over those obtained for the Au based detectors which were observed to be 1.23 × 1010 cm Hz0.5/W & 34.5, respectively.

Effects of grain size on the properties of bulk nanocrystalline Co-Ni alloys

NASA Astrophysics Data System (ADS)

Qiao, Gui-Ying; Xiao, Fu-Ren

2017-08-01

Bulk nanocrystalline Co78Ni22 alloys with grain size ranging from 5 nm to 35 nm were prepared by high-speed jet electrodeposition (HSJED) and annealing. Microhardness and magnetic properties of these alloys were investigated by microhardness tester and vibrating sample magnetometer. Effects of grain size on these characteristics were also discussed. Results show that the microhardness of nanocrystalline Co78Ni22 alloys increases following a d -1/2-power law with decreasing grain size d. This phenomenon fits the Hall-Petch law when the grain size ranges from 5 nm to 35 nm. However, coercivity H c increases following a 1/d-power law with increasing grain size when the grain size ranges from 5 nm to 15.9 nm. Coercivity H c decreases again for grain sizes above 16.6 nm according to the d 6-power law.

The inverse hall-petch relation in nanocrystalline metals: A discrete dislocation dynamics analysis

NASA Astrophysics Data System (ADS)

Quek, Siu Sin; Chooi, Zheng Hoe; Wu, Zhaoxuan; Zhang, Yong Wei; Srolovitz, David J.

2016-03-01

When the grain size in polycrystalline materials is reduced to the nanometer length scale (nanocrystallinity), observations from experiments and atomistic simulations suggest that the yield strength decreases (softening) as the grain size is decreased. This is in contrast to the Hall-Petch relation observed in larger sized grains. We incorporated grain boundary (GB) sliding and dislocation emission from GB junctions into the classical DDD framework, and recovered the smaller is weaker relationship observed in nanocrystalline materials. This current model shows that the inverse Hall-Petch behavior can be obtained through a relief of stress buildup at GB junctions from GB sliding by emitting dislocations from the junctions. The yield stress is shown to vary with grain size, d, by a d 1 / 2 relationship when grain sizes are very small. However, pure GB sliding alone without further plastic accomodation by dislocation emission is grain size independent.

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

NASA Astrophysics Data System (ADS)

Paul, Susmita; Choudhury, Amarjyoti

2014-10-01

Mixed phase nanocrystalline titania are prepared by simple sol-gel method. The physico-chemical characteristics of the prepared nanoparticles are studied with X-ray diffraction, high-resolution transmission electron microscopy, RAMAN, BET, UV-Vis, steady state and time resolved photoluminescence. X-ray diffraction and Raman spectra clearly demarcate the anatase and rutile phase as both the phases give different diffraction patterns and Raman peaks. A comparison in the band gap indicates that pure anatase and rutile phase have band gap in the UV region, whereas a mixture of these phases has lower band gap and corresponds to the visible region. Steady state and time resolved photoluminescence are employed to understand the emissivity and carrier lifetime. The photocatalytic activity is evaluated by monitoring the degradation of phenol under visible light illumination. Due to the synergistic effect of mixed anatase and rutile phases, mixed phase nanocrystalline titania exhibit superior photocatalytic activity.

Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors.

PubMed

Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

2016-02-25

In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al₂O₃ and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value.

Electroformed Nanocrystalline Coatings: An Advanced Alternative to Hard Chrome Electroplating

DTIC Science & Technology

2003-11-21

hypo/ phosphorous acid was included in the estimate. The cost analysis is given in Table 2-3. The relative consumable cost for the nanocrystalline...concentrations and phosphorous acid concentrations. While the internal stress of the Co- P deposit was affected by changes in the above-mentioned...may be occurring which consumes the phosphorous acid in solution (see Section 2.2). Table 5-1 Hardness at distance from deposit/substrate

Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

NASA Astrophysics Data System (ADS)

Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

2014-02-01

A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

PubMed

Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

2010-06-15

In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

Synthesis and properties of nanocrystalline Bi-Te based thermoelectric materials for energy application

NASA Astrophysics Data System (ADS)

Almohaimeed, Sulaiman

Thermoelectric phenomenon is the science associated with converting thermal energy into electricity based on the Seebeck effect. Bismuth telluride Bi 2Te3 is currently considered to be the state-of-the art thermoelectric material with high efficiency for low temperature applications and is therefore attractive for energy harvesting processes. Nanostructures thermoelectric materials provide a novel way to enhance thermoelectric properties and are considered to be the efficient building blocks for thermoelectric devices. In this work, n- and p-type bulk nanocrystalline Bismuth telluride thermoelectric materials were prepared by mechanical alloying / ball milling technique. The produced nano-crystalline powder were then consolidated using hot compaction under inert atmosphere. The novel processing of these materials maintained the nanostructure in both n- and p-type. Structural properties of the n- and p-types were characterized using X ray diffraction, scanning electron microscopy and transmission electron microscope. These techniques proved that the average grian size of the milled thermoelectric materials was about 20 nm. Accordingly, a Significant improvement in the figure of merit (ZT) is achieved through significant lattice thermal conductivity reduction and Seebeck coefficient improvement. The maximum ZT value for the n-type nanocrystalline thermoelectric was 1.67 at 373 K while the maximum ZT value for the p-type was 1.78 at the same temperature. These values are considered to be the highest values reported for similar materials. Evaluation of the mechanical properties was also performed through microhardness measurement using Vickers micro-hardness test, which shows an enhancement in mechanical properties for the produced materials.

Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gareso, P. L., E-mail: pgareso@gmail.com; Rauf, N., E-mail: pgareso@gmail.com; Juarlin, E., E-mail: pgareso@gmail.com

2014-09-25

Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes.more » The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.« less

Microwave plasma chemical synthesis of nanocrystalline carbon film structures and study their properties

NASA Astrophysics Data System (ADS)

Bushuev, N.; Yafarov, R.; Timoshenkov, V.; Orlov, S.; Starykh, D.

2015-08-01

The self-organization effect of diamond nanocrystals in polymer-graphite and carbon films is detected. The carbon materials deposition was carried from ethanol vapors out at low pressure using a highly non-equilibrium microwave plasma. Deposition processes of carbon film structures (diamond, graphite, graphene) is defined. Deposition processes of nanocrystalline structures containing diamond and graphite phases in different volume ratios is identified. The solid film was obtained under different conditions of microwave plasma chemical synthesis. We investigated the electrical properties of the nanocrystalline carbon films and identified it's from various factors. Influence of diamond-graphite film deposition mode in non-equilibrium microwave plasma at low pressure on emission characteristics was established. This effect is justified using the cluster model of the structure of amorphous carbon. It was shown that the reduction of bound hydrogen in carbon structures leads to a decrease in the threshold electric field of emission from 20-30 V/m to 5 V/m. Reducing the operating voltage field emission can improve mechanical stability of the synthesized film diamond-graphite emitters. Current density emission at least 20 A/cm2 was obtained. Nanocrystalline carbon film materials can be used to create a variety of functional elements in micro- and nanoelectronics and photonics such as cold electron source for emission in vacuum devices, photonic devices, cathodoluminescent flat display, highly efficient white light sources. The obtained graphene carbon net structure (with a net size about 6 μm) may be used for the manufacture of large-area transparent electrode for solar cells and cathodoluminescent light sources

Sn 1-x VxOy thin films deposited by pulsed laser ablation for gas sensing devices

NASA Astrophysics Data System (ADS)

Duhalde, Stella; Vignolo, M. F.; Quintana, G.; Mercader, R.; Lamagna, Antonino

2000-02-01

Polycrystalline pure and V-doped SnO2 thin films have been prepare by pulsed laser deposition (PLD) on Si substrates, with a Si3Ni4 buffered layer. PLD technique, under proper conditions, has probed to produce nanocrystalline-structured materials, which are suitable for gas sensing. In this work we analyze the role of V doping in the structural properties and in the electrical conductivity of the films. The deposition temperature was fixed at 600 degrees C and the films were grown in oxygen atmosphere. The films resulted nanocrystalline with 50 to 120 nm average grain size connected by necks with high surface areas. The microstructural and electronic properties of all the films were analyzed using scanning-electron microscopy, x-ray diffraction and conversion electron Moessbauer spectroscopy. Electrical conductance in a dynamic regime in dry synthetic air has been evaluated as a function of temperature. Moessbauer spectra reveal the presence of 15 percent of Sn2+ in the 5at. percent V-doped films. At about 340 degrees C, a strong increase in the conductivity of the films occurs. Possible explanations are that thermal energy could excite electrons from the vanadium ions into the crystal's conduction band or promotes the diffusion of surface oxygen vacancies towards the bulk, increasing strongly the conductivity of the film.

[Effect of temperature on the structure of CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramics studied by Raman spectroscopy].

PubMed

Li, Bao-Wei; Ouyang, Shun-Li; Zhang, Xue-Feng; Jia, Xiao-Lin; Deng, Lei-Bo; Liu, Fang

2014-07-01

In the present paper, nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system was produced by melting method. The CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramic was measured by Raman spectroscopy in the temperature range from -190 to 310 degrees C in order to study the effect of temperature on the structure of this system nanocrystalline glass-ceramics. The results showed that different non-bridge oxygen bond silicon-oxygen tetrahedron structural unit changes are not consistent with rising temperature. Further analyses indicated that: the SiO4 tetrahedron with 2 non-bridged oxygen (Q2), the SiO4 tetrahedron with 3 non-bridged oxygen (Q(1)), which are situated at the edge of the 3-D SiO4 tetrahedrons network, and the SiO4 tetrahedron with 4 non-bridged oxygen (Q(0)), which is situated outside the 3-D network all suffered a significant influence by the temperature change, which has been expressed as: shifts towards the high wave-number, increased bond force constants, and shortened bond lengths. This paper studied the influence of temperature on CMAS system nanocrystalline glass-ceramics using variable temperature Raman technology. It provides experiment basis to the research on external environment influence on CMAS system nanocrystalline glass-ceramics materials in terms of structure and performance. In addition, the research provides experimental basis for controlling the expansion coefficient of nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system.

Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

NASA Astrophysics Data System (ADS)

Li, Bin; Zhang, Qin-Jian; Shi, Yan-Chao; Li, Jia-Jun; Li, Hong; Lu, Fan-Xiu; Chen, Guang-Chao

2014-08-01

A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

Characterization of doped hydrogenated nanocrystalline silicon films prepared by plasma enhanced chemical vapour deposition

NASA Astrophysics Data System (ADS)

Wang, Jin-Liang; Wu, Er-Xing

2007-03-01

The B- and P-doped hydrogenated nanocrystalline silicon films (nc-Si:H) are prepared by plasma-enhanced chemical vapour deposition (PECVD). The microstructures of doped nc-Si:H films are carefully and systematically characterized by using high resolution electron microscopy (HREM), Raman scattering, x-ray diffraction (XRD), Auger electron spectroscopy (AES), and resonant nucleus reaction (RNR). The results show that as the doping concentration of PH3 increases, the average grain size (d) tends to decrease and the crystalline volume percentage (Xc) increases simultaneously. For the B-doped samples, as the doping concentration of B2H6 increases, no obvious change in the value of d is observed, but the value of Xc is found to decrease. This is especially apparent in the case of heavy B2H6 doped samples, where the films change from nanocrystalline to amorphous.

Nanocrystalline (U0.5Ce0.5)O2±x solid solutions through citrate gel-combustion

NASA Astrophysics Data System (ADS)

Maji, D.; Ananthasivan, K.; Venkata Krishnan, R.; Balakrishnan, S.; Amirthapandian, S.; Joseph, Kitheri; Dasgupta, Arup

2018-04-01

Nanocrystalline powders of (U0.5Ce0.5)O2±x solid solutions were synthesized in bulk (100-200 g) through the citrate gel combustion. The fuel (citric acid) to oxidant (nitrate) mole ratio (R) was varied from 0.1 to 1.0. Two independent lots of the products obtained through the gel-combustion were calcined at 973 K in air and in a mixture of argon containing 8% H2 respectively. All these powders were characterized for their bulk density, X-ray crystallite size, specific surface area, size distribution of the particles, porosity as well as residual carbon. The morphology and microstructures of these powders were studied by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Nanocrystalline single phase fluorite solid solutions having a typical crystallite size of about (7-15 nm) were obtained. These powders were highly porous comprising cuboidal flaky agglomerates. The combustion mixture with an 'R' value of 0.25 was found to undergo volume combustion and was found to yield a product that was distinctly different. The systematic investigation on synthesis and characterization of nanocrystalline UCeO2 is reported for the first time.

Quantifying the influence of twin boundaries on the deformation of nanocrystalline copper using atomistic simulations

DOE PAGES

Tucker, Garritt J.; Foiles, Stephen Martin

2014-09-22

Over the past decade, numerous efforts have sought to understand the influence of twin boundaries on the behavior of polycrystalline materials. Early results suggested that twin boundaries within nanocrystalline face-centered cubic metals have a considerable effect on material behavior by altering the activated deformation mechanisms. In this work, we employ molecular dynamics simulations to elucidate the role of twin boundaries on the deformation of <100> columnar nanocrystalline copper at room temperature under uniaxial strain. We leverage non-local kinematic metrics, formulated from continuum mechanics theory, to compute atomically-resolved rotational and strain fields during plastic deformation. These results are then utilized tomore » compute the distribution of various nanoscale mechanisms during straining, and quantitatively resolve their contribution to the total strain accommodation within the microstructure, highlighting the fundamental role of twin boundaries. Our results show that nanoscale twins influence nanocrystalline copper by altering the cooperation of fundamental deformation mechanisms and their contributed role in strain accommodation, and we present new methods for extracting useful information from atomistic simulations. The simulation results suggest a tension–compression asymmetry in the distribution of deformation mechanisms and strain accommodation by either dislocations or twin boundary mechanisms. In highly twinned microstructures, twin boundary migration can become a significant deformation mode, in comparison to lattice dislocation plasticity in non-twinned columnar microstructures, especially during compression.« less

Ag implantation-induced modification of Ni-Ti shape memory alloy thin films

NASA Astrophysics Data System (ADS)

Kumar, V.; Singhal, R.; Vishnoi, R.; Banerjee, M. K.; Sharma, M. C.; Asokan, K.; Kumar, M.

2017-08-01

Nanocrystalline thin films of Ni-Ti shape memory alloy are deposited on an Si substrate by the DC-magnetron co-sputtering technique and 120 keV Ag ions are implanted at different fluences. The thickness and composition of the pristine films are determined by Rutherford Backscattering Spectrometry (RBS). X-Ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe resistivity methods have been used to study the structural, morphological and electrical transport properties. XRD analysis has revealed the existence of martensitic and austenite phases in the pristine film and also evidenced the structural changes in Ag-implanted Ni-Ti films at different fluences. AFM studies have revealed that surface roughness and grain size of Ni-Ti films have decreased with an increase in ion fluence. The modifications in the mechanical behaviour of implanted Ni-Ti films w.r.t pristine film is determined by using a Nano-indentation tester at room temperature. Higher hardness and the ratio of higher hardness (H) to elastic modulus (Er) are observed for the film implanted at an optimized fluence of 9 × 1015 ions/cm2. This improvement in mechanical behaviour could be understood in terms of grain refinement and dislocation induced by the Ag ion implantation in the Ni-Ti thin films.

Annealing induced low coercivity, nanocrystalline Co-Fe-Si thin films exhibiting inverse cosine angular variation

NASA Astrophysics Data System (ADS)

Hysen, T.; Al-Harthi, Salim; Al-Omari, I. A.; Geetha, P.; Lisha, R.; Ramanujan, R. V.; Sakthikumar, D.; Anantharaman, M. R.

2013-09-01

Co-Fe-Si based films exhibit high magnetic moments and are highly sought after for applications like soft under layers in perpendicular recording media to magneto-electro-mechanical sensor applications. In this work the effect of annealing on structural, morphological and magnetic properties of Co-Fe-Si thin films was investigated. Compositional analysis using X-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a native oxide surface layer consisting of oxides of Co, Fe and Si on the surface. The morphology of the as deposited films shows mound like structures conforming to the Volmer-Weber growth model. Nanocrystallisation of amorphous films upon annealing was observed by glancing angle X-ray diffraction and transmission electron microscopy. The evolution of magnetic properties with annealing is explained using the Herzer model. Vibrating sample magnetometry measurements carried out at various angles from 0° to 90° to the applied magnetic field were employed to study the angular variation of coercivity. The angular variation fits the modified Kondorsky model. Interestingly, the coercivity evolution with annealing deduced from magneto-optical Kerr effect studies indicates a reverse trend compared to magetisation observed in the bulk. This can be attributed to a domain wall pinning at native oxide layer on the surface of thin films. The evolution of surface magnetic properties is correlated with morphology evolution probed using atomic force microscopy. The morphology as well as the presence of the native oxide layer dictates the surface magnetic properties and this is corroborated by the apparent difference in the bulk and surface magnetic properties.

Physical properties of sago starch biocomposite filled with Nanocrystalline Cellulose (NCC) from rattan biomass: the effect of filler loading and co-plasticizer addition

NASA Astrophysics Data System (ADS)

Nasution, H.; Harahap, H.; Fath, M. T. Al; Afandy, Y.

2018-02-01

Rattan biomass is an abundant bioresources from processing industry of rattan which contains 37.6% cellulose. The high cellulose contents of rattan biomass make it a source of nanocrystalline cellulose as a filler in biocomposites. Isolation of alpha cellulose from rattan biomass was being prepared by using three stages: delignification, alkalization, and bleaching. It was delignificated with 3.5% HNO3 and NaNO2, precipitated with 17.5% NaOH, bleaching process with 10% H2O2. Nanocrystal obtained through the hydrolysis of alpha cellulose using 45% H2SO4 and followed by mechanical steps of ultrasonication, centrifugation, and filtration with a dialysis membrane. Biocomposite was being prepared by using a solution casting method, which includes 1-4 wt% nanocrystalline cellulose from rattan biomass as fillers, 10-40 wt% acetic acid as co-plasticizer and 30 wt% glycerol as plasticizer. The biocomposite characteristic consists of density, water absorption, and water vapors transmission rate. The results showed the highest density values was 0.266 gram/cm3 obtained at an additional of 3 wt% nanocrystalline cellulose from rattan biomass and 30 wt% acetic acid. The lowest water absorption was 9.37% at an additional of 3 wt% nanocrystalline cellulose from rattan biomass and 10 wt% acetic acid. It was observed by the addition of nanocrystalline cellulose might also decrease the rate of water vapor transmission that compared to the non-filler biocomposite.

Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} as a gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinde, Tukaram J., E-mail: pshindetj@yahoo.co.in; Gadkari, Ashok B.; Jadhav, Sarjerao R.

2015-06-24

Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl{sub 2}, LPG and C{sub 2}H{sub 5}OH. It was observed that NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Cavity evolution at grain boundaries as a function of radiation damage and thermal conditions in nanocrystalline nickel

DOE PAGES

Muntifering, Brittany; Blair, Sarah Jane; Gong, Cajer; ...

2015-12-30

Enhanced radiation tolerance of nanostructured metals is attributed to the high density of interfaces that can absorb radiation-induced defects. Here, cavity evolution mechanisms during cascade damage, helium implantation, and annealing of nanocrystalline nickel are characterized via in situ transmission electron microscopy (TEM). Films subjected to self-ion irradiation followed by helium implantation developed evenly distributed cavity structures, whereas films exposed in the reversed order developed cavities preferentially distributed along grain boundaries. Post-irradiation annealing and orientation mapping demonstrated uniform cavity growth in the nanocrystalline structure, and cavities spanning multiple grains. Furthermore, these mechanisms suggest limited ability to reduce swelling, despite the stabilitymore » of the nanostructure.« less

A novel route for synthesis of nanocrystalline hydroxyapatite from eggshell waste.

PubMed

Siva Rama Krishna, D; Siddharthan, A; Seshadri, S K; Sampath Kumar, T S

2007-09-01

The eggshell waste has been value engineered to a nanocrystalline hydroxyapatite (HA) by microwave processing. To highlight the advantages of eggshell as calcium precursor in the synthesis of HA (OHA), synthetic calcium hydroxide was also used to form HA (SHA) following similar procedure and were compared with a commercially available pure HA (CHA). All the HAs were characterized by X-ray powder diffraction (XRD) method, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and specific surface area measurements. Nanocrystalline nature of OHA is revealed through characteristic broad peaks in XRD patterns, platelets of length 33-50 nm and width 8-14 nm in TEM micrograph and size calculations from specific surface area measurements. FT-IR spectra showed characteristic bands of HA and additionally peaks of carbonate ions. The cell parameter calculations suggest the formation of carbonated HA of B-type. The OHA exhibits superior sinterability in terms of hardness and density than both SHA and CHA may be due to larger surface area of its spherulite structure. The in vitro dissolution study shows longer stability in phosphate buffer and cell culture test using osteoblast cells establishes biocompatibility of OHA.

Synthesis and properties of nickel-doped nanocrystalline barium hexaferrite ceramic materials

NASA Astrophysics Data System (ADS)

Waqar, Moaz; Rafiq, Muhammad Asif; Mirza, Talha Ahmed; Khalid, Fazal Ahmad; Khaliq, Abdul; Anwar, Muhammad Sabieh; Saleem, Murtaza

2018-04-01

M-type barium hexaferrite ceramics have emerged as important materials both for technological and commercial applications. However, limited work has been reported regarding the investigation of nanocrystalline Ni-doped barium hexaferrites. In this study, nanocrystalline barium hexaferrite ceramics with the composition BaFe12- x Ni x O19 (where x = 0, 0.3 and 0.5) were synthesized by sol-gel method and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and precision impedance analyzer. All the synthesized samples had single magnetoplumbite phase having space group P63/mmc showing the successful substitution of Ni in BaFe12O19 without the formation of any impurity phase. Average grain size of undoped samples was around 120 nm which increased slightly with the addition of Ni. Saturation magnetization ( M s) and remnant magnetization ( M r) increased with the addition of Ni, however, coercivity ( H c) decreased with the increase in Ni from x = 0 to x = 0.5. Real and imaginary parts of permittivity decreased with the increasing frequency and increased with Ni content. Dielectric loss and conductivity showed slight variation with the increase in Ni concentration.

Synthesis of nanocrystalline Ni/Ce-YSZ powder via a polymerization route

NASA Astrophysics Data System (ADS)

Abolghasemi, Z.; Tamizifar, M.; Arzani, K.; Nemati, A.; Khanfekr, A.; Bolandi, M.

2013-08-01

Pechini process was used for preparation of three kinds of nanocrystalline powders of yttria-stabilized zirconia (YSZ): doped with 1.5 mol% nickel oxide, doped with 15 mol% ceria, and doped with 1.5 mol% nickel oxide plus 15 mol% ceria. Zirconium chloride, yttrium nitrate, cerium nitrate, nickel nitrate, citric acid and ethylene glycol were polymerized at 80 °C to produce a gel. XRD, SEM and TEM analyses were used to investigate the crystalline phases and microstructures of obtained compounds. The results of XRD revealed the formation of nanocrystalline powder at 900 °C. Morphology of the powder calcined at 900 °C, examined with a scanning electron microscope, showed that the presence of nickel and cerium inhibited the grain growth in the system. The average crystallite size of the material doped with nickel oxide (9.33 nm) was bigger than the one doped with cerium oxide (9.29 nm), while the YSZ doping with the two oxides simultaneously promoted the grain growth with crystallite size of 11.37 nm. Yttria-stabilized zirconia powder with a mean crystallite size of 9.997 nm was prepared successfully by this method.

Hyperfine Fields in Nanocrystalline Fe0.48Al0.52

NASA Astrophysics Data System (ADS)

Szymański, K.; Satuła, D.; Dobrzyński, L.; Voronina, E.; Yelsukov, E. P.

2004-12-01

Mössbauer measurements with circularly polarized radiation were performed on a nanocrystalline, disordered Fe48Al52 alloy. The analysis of the data for various polarization states resulted in the characterization of the hyperfine magnetic field distribution and the dependence of the average z-component of hyperfine field on the chemical environment. An increasing number of Al in the first coordination shell causes not only a decrease of magnetic moments but also introduces noncollinearity.

The Role of Grain Size on Neutron Irradiation Response of Nanocrystalline Copper

PubMed Central

Mohamed, Walid; Miller, Brandon; Porter, Douglas; Murty, Korukonda

2016-01-01

The role of grain size on the developed microstructure and mechanical properties of neutron irradiated nanocrystalline copper was investigated by comparing the radiation response of material to the conventional micrograined counterpart. Nanocrystalline (nc) and micrograined (MG) copper samples were subjected to a range of neutron exposure levels from 0.0034 to 2 dpa. At all damage levels, the response of MG-copper was governed by radiation hardening manifested by an increase in strength with accompanying ductility loss. Conversely, the response of nc-copper to neutron irradiation exhibited a dependence on the damage level. At low damage levels, grain growth was the primary response, with radiation hardening and embrittlement becoming the dominant responses with increasing damage levels. Annealing experiments revealed that grain growth in nc-copper is composed of both thermally-activated and irradiation-induced components. Tensile tests revealed minimal change in the source hardening component of the yield stress in MG-copper, while the source hardening component was found to decrease with increasing radiation exposure in nc-copper. PMID:28773270

Structural and optical studies of 100 MeV Au irradiated thin films of tin oxide

NASA Astrophysics Data System (ADS)

Jaiswal, Manoj Kumar; Kanjilal, D.; Kumar, Rajesh

2013-11-01

Thin films of tin(IV) oxide (SnO2) of 100 nm thickness were grown on silicon (1 0 0) matrices by electron beam evaporation deposition technique under high vacuum. The thicknesses of these films were monitored by piezo-sensor attached to the deposition chamber. Nanocrystallinity is achieved in these thin films by 100 MeV Au8+ using 1 pnA current at normal incidence with ion fluences varying from 1 × 1011 ions/cm2 to 5 × 1013 ions/cm2. Swift Heavy Ion beam irradiation was carried out by using 15 UD Pelletron Accelerator at IUAC, New Delhi, India. Optical studies of pristine and ion irradiated thin films were characterized by UV-Visible spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. Prominent peak at 610 cm-1 in FTIR spectrum confirmed the O-Sn-O bonding of tin(IV) oxide. For Surface topographical studies and grain size calculations, these films were characterized by Atomic Force Microscope (AFM) using Nanoscope III-A. Crystallinity and phase transformation due to irradiation of pristine and irradiated films were characterized by Glancing Angle X-ray Diffraction (GAXRD) using Brucker-D8 advance model. GAXRD results show improvement in crystallinity and phase transformation due to swift heavy ion irradiation. Grain size distribution was verified by AFM and GAXRD results. Swift heavy ion induced modifications in thin films of SnO2 were confirmed by the presence of prominent peaks at 2θ values of 30.65°, 32.045°, 43.94°, 44.96° and 52.36° in GAXRD spectrum.

Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

NASA Astrophysics Data System (ADS)

Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

2014-07-01

BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

Synthesis of porous nanocrystalline NiO with hexagonal sheet-like morphology by homogeneous precipitation method

NASA Astrophysics Data System (ADS)

Sharma, Ravi Kant; Ghose, Ranjana

2015-04-01

Porous nanocrystalline NiO has been synthesized by a simple homogeneous precipitation method in short time at low calcination temperature without using any surfactant, chelating or gelating agents. The porous nanocrystalline NiO with a hexagonal sheet-like morphology were obtained by calcination of Ni(OH)2 nanoflakes at 500 °C. The calcination temperature strongly influences the morphology, crystallite size, specific surface area, pore volume and optical band gap of the samples. The samples were characterized using powder X-ray diffraction, thermal gravimetric analysis, FT-IR spectroscopy, UV-Visible diffuse reflectance spectroscopy, surface area measurements, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy. The chemical activity of the samples was tested by catalytic reduction of 4-nitrophenol with NaBH4.

Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

NASA Astrophysics Data System (ADS)

Tran, Tien Bich

As the main inorganic component of bone, hydroxyapatite (HA, Ca 10(PO4)6(OH)2) should be an ideal candidate in biomaterials selection. When grain sizes are in the nanometric regime, protein adsorption and cell adhesion are enhanced, while strength, hardness, and wear resistance are improved. Unfortunately, low phase stability, poor sinterability, and a tendency towards exaggerated grain coarsening challenge full densification of nanocrystalline hydroxyapatite by conventional sintering methods. The field-assisted sintering technique (FAST) has successfully consolidated a variety of nanocrystalline metals and ceramics in dramatically reduced times. The sintering enhancements observed during FAST can be attributed to thermal and athermal effects. The rapid heating rates (up to ˜1000ºC/min) afforded by FAST contribute a significant thermal effect. Since fast heating rates reduce powder exposure to sub-sintering temperatures, non-densifying surface diffusion is limited. The athermal effects of FAST are less well understood and can include plasma generation, dielectric breakdown, particle surface cleaning, grain boundary pinning, and space charge effects. Applying the field-assisted sintering technique to nanocrystalline hydroxyapatite yielded surprising results. Deviations from conventional densification behavior were observed, with dehydroxylation identified as the most deleterious process to densification as well as mechanical and biological performance. Since hydroxyapatite is not a stable phase at high temperatures and low water partial pressure atmospheres, desintering due to dehydroxylation-related pore formation became apparent during Stage III sintering. In fact, the degree of desintering and pore formation increased with the extent of Stage III sintering and grain growth. The atomic rearrangements taking place during grain boundary migration are believed to favor the formation of more-stable oxyapatite through hydroxyapatite dehydroxylation. This behavior was

Application Potential of Nanocrystalline Ribbons Still Pending

NASA Astrophysics Data System (ADS)

Butvin, Pavol; Butvinová, Beata; Švec, Peter; Sitek, Jozef

2010-09-01

Nanocrystalline soft-magnetic ribbons promised a wide-spread practical use when introduced at the beginning of nineties. After 20 years of extensive research there are still unclear material problems which are thought to be the principal reason why these materials show but marginal use. Poorly controllable magnetic anisotropy due to spontaneous intrinsic macroscopic stress that comes from an inevitable heterogeneity of the ribbon materials is pointed to in this work. Certain stress-based mechanisms are shown to induce the unintended anisotropy in the already familiar Finemets as well as in the newer Hitperms. Hysteresis loops, domain structure and power loss is used to reveal the anisotropy consequences and particular connected but still unanswered questions are pinpointed.

Local crystal/chemical structures at iron sites in amorphous, magnetic, and nanocrystalline materials

NASA Astrophysics Data System (ADS)

Clark, Ted Michael

Order-disorder phenomena have been examined by means of Mossbauer spectroscopy in a variety of materials, including (a) tektites and other silicate glasses, (b) magnetic materials such as natural and synthetic magnetoplumbite, M-type hexagonal ferrites and magnetite, and (c) nanocrystalline zinc ferrite. A methodology has been established for the analysis of the local crystal/chemical structures of iron in tektites and its application has reconfirmed a low ferric/ferrous ratio of approximately 0.10 for tektites. Additionally, a greater degree of submirocscopic heterogeneity has been established for Muong Nong tektites in comparison with splash form tektites. The dynamics of the 2b site in hexagonal ferrites has been studied above and below the Curie temperature for magnetoplumbite and its synthetic analogs, and also for polycrystalline and oriented single-crystals of MeFesb{12}Osb{19} (Me=Ba, Sr, Pb). Cation ordering on this site is shown to be dependent on the thermal history of the material, while the dynamic disorder of the 2b site for the end-member hexagonal ferrites is shown to be influenced by the divalent heavy metal species, Me. The influence of chemical composition on the morphology of magnetite has been shown to depend on the site preference of impurity cations: Substitutional impurities with tetrahedral site preferences are postulated to result in the seldom-observed cubic habit. Based on the cation distributions of bulk and nanocrystalline material it is held that the enhanced magnetic moments and susceptibilities of nanocrystalline zinc ferrite are shown to be consistent with surface phenomena, independent of synthesis methodology, and contrary to claims of special effects resulting from a particular synthesis methodology.

Characterization of synthetic nanocrystalline mackinawite: crystal structure, particle size, and specific surface area

PubMed Central

Jeong, Hoon Y.; Lee, Jun H.; Hayes, Kim F.

2010-01-01

Iron sulfide was synthesized by reacting aqueous solutions of sodium sulfide and ferrous chloride for 3 days. By X-ray powder diffraction (XRPD), the resultant phase was determined to be primarily nanocrystalline mackinawite (space group: P4/nmm) with unit cell parameters a = b = 3.67 Å and c = 5.20 Å. Iron K-edge XAS analysis also indicated the dominance of mackinawite. Lattice expansion of synthetic mackinawite was observed along the c-axis relative to well-crystalline mackinawite. Compared with relatively short-aged phase, the mackinawite prepared here was composed of larger crystallites with less elongated lattice spacings. The direct observation of lattice fringes by HR-TEM verified the applicability of Bragg diffraction in determining the lattice parameters of nanocrystalline mackinawite from XRPD patterns. Estimated particle size and external specific surface area (SSAext) of nanocrystalline mackinawite varied significantly with the methods used. The use of Scherrer equation for measuring crystallite size based on XRPD patterns is limited by uncertainty of the Scherrer constant (K) due to the presence of polydisperse particles. The presence of polycrystalline particles may also lead to inaccurate particle size estimation by Scherrer equation, given that crystallite and particle sizes are not equivalent. The TEM observation yielded the smallest SSAext of 103 m2/g. This measurement was not representative of dispersed particles due to particle aggregation from drying during sample preparation. In contrast, EGME method and PCS measurement yielded higher SSAext (276–345 m2/g by EGME and 424 ± 130 m2/g by PCS). These were in reasonable agreement with those previously measured by the methods insensitive to particle aggregation. PMID:21085620

Photoelectrochemical (PEC) studies on Cu2SnS3 (CTS) thin films deposited by chemical bath deposition method.

PubMed

Shelke, H D; Lokhande, A C; Kim, J H; Lokhande, C D

2017-11-15

Cu 2 SnS 3 (CTS) thin films have been successfully deposited on a cost-effective stainless steel substrate by simple and inexpensive chemical bath deposition (CBD) method. The films are deliberated in provisos of their structural, morphological, optical and photoelectrochemical (PEC) properties before and after annealing treatment, using various physico-chemical techniques. The XRD studies showed the formation of triclinic phase of CTS films with nanocrystalline structure. Also, the crystallinity is enhanced with annealing and the secondary phase of Cu 2 S observed. Raman analysis confirmed the formation of CTS compound with secondary Cu 2 S phase. The SEM images also discovered mostly tiny spherical grains and significant progress in the size of grains after annealing. The films possess direct transitions with band gap energies of 1.35eV and 1.31eV before and after annealing, respectively. The improved photoconversion efficiency of CTS thin film based PEC cell is explained with the help of theoretical modeling of energy band diagram and correspondent circuit model of the impedance spectra. Copyright © 2017 Elsevier Inc. All rights reserved.

Structural Inheritance and Redox Performance of Nanoporous Electrodes from Nanocrystalline Fe85.2B10-14P0-4Cu0.8 Alloys

PubMed Central

Fu, Chaoqun; Xu, Lijun; Dan, Zhenhua; Makino, Akihiro; Hara, Nobuyoshi; Qin, Fengxiang; Chang, Hui

2017-01-01

Nanoporous electrodes have been fabricated by selectively dissolving the less noble α-Fe crystalline phase from nanocrystalline Fe85.2B14–xPxCu0.8 alloys (x= 0, 2, 4 at.%). The preferential dissolution is triggered by the weaker electrochemical stability of α-Fe nanocrystals than amorphous phase. The final nanoporous structure is mainly composed of amorphous residual phase and minor undissolved α-Fe crystals and can be predicted from initial microstructure of nanocrystalline precursor alloys. The structural inheritance is proved by the similarity of the size and outlines between nanopores formed after dealloying in 0.1 M H2SO4 and α-Fe nanocrystals precipitated after annealing of amorphous Fe85.2B14−xPxCu0.8 (x = 0, 2, 4 at.%) alloys. The Redox peak current density of the nanoporous electrodes obtained from nanocrystalline Fe85.2B10P4Cu0.8 alloys is more than one order higher than those of Fe plate electrode and its counterpart nanocrystalline alloys due to the large surface area and nearly-amorphous nature of ligaments. PMID:28594378

Sinus Floor Elevation and Augmentation Using Synthetic Nanocrystalline and Nanoporous Hydroxyapatite Bone Substitute Materials: Preliminary Histologic Results.

PubMed

Belouka, Sofia-Maria; Strietzel, Frank Peter

To compare the tissue composition of augmented sites after using two different synthetic bone substitute materials, nanocrystalline and nanoporous hydroxyapatite (HA), for sinus floor elevation and augmentation. Forty-four patients received 88 titanium screw implants (Camlog Promote plus) of 4.3-mm diameter and 11- or 13-mm length, placed simultaneously during sinus floor elevation and augmentation. Nanocrystalline (Ostim) or nanoporous (NanoBone) HA were used exclusively. Bone substitute materials and implant lengths were allocated by randomization. Bone biopsy specimens were obtained from the former area of the lateral access window at implant exposure during healing abutment placement after 6 months. Biopsy specimens were prepared and examined histologically and histomorphometrically. All implants were osseointegrated at the time of exposure. Clinically and histologically, no signs of inflammation in the augmented sites were present. The histomorphometric analysis of 44 biopsy specimens revealed 31.8% ± 11.6% newly formed bone for sites augmented with nanocrystalline HA and 34.6% ± 9.2% for nanoporous HA (P = .467). The proportion of remaining bone substitute material was 28.4% ± 18.6% and 30% ± 13%, respectively (P = .453). The proportion of soft tissue within the biopsy specimens was 39.9% ± 11.1% and 35.4% ± 6.8%, respectively (P = .064). No significant differences were found between the area fractions of bone, bone substitute material, and soft tissue concerning the bone substitute material utilized. Within the present study, both synthetic bone substitute materials, nanocrystalline and nanoporous HA, were found to support bone formation in sinus floor elevation and augmentation procedures by osteoconductivity. They were not completely resorbed after 6 months. The amounts of newly formed bone, soft tissue, and bone substitute material remnants were found to be similar, indicating that both materials are likewise suitable for sinus floor elevation and

Stress effects in ferroelectric perovskite thin-films

NASA Astrophysics Data System (ADS)

Zednik, Ricardo Johann

The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution

Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors

PubMed Central

Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

2016-01-01

In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al2O3 and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value. PMID:28344296

Synthesis of nanocrystalline rare earth oxides by glycothermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosokawa, Saburo; Iwamoto, Shinji; Inoue, Masashi

2008-11-03

The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 deg. C yielded a product containing acetate groups and glycol moieties. From this product, Y{sub 2}O{sub 3} was directly crystallized at 400 deg. C without the formation of a carbonate oxide phase. The thus-obtained Y{sub 2}O{sub 3} samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m{sup 2}/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.

The role of the domain size and titanium dopant in nanocrystalline hematite thin films for water photolysis

DOE PAGES

Yan, Danhua; Tao, Jing; Kisslinger, Kim; ...

2015-10-13

Here we develop a novel technique for preparing high quality Ti-doped hematite thin films for photoelectrochemical (PEC) water splitting, through sputtering deposition of metallic iron films from an iron target embedded with titanium (dopants) pellets, followed by a thermal oxidation step that turns the metal films into doped hematite. It is found that the hematite domain size can be tuned from ~10 nm to over 100 nm by adjusting the sputtering atmosphere from more oxidative to mostly inert. The better crystallinity at a larger domain size ensures excellent PEC water splitting performance, leading to record high photocurrent from pure planarmore » hematite thin films on FTO substrates. Titanium doping further enhances the PEC performance of hematite photoanodes. The photocurrent is improved by 50%, with a titanium dopant concentration as low as 0.5 atom%. As a result, it is also found that the role of the titanium dopant in improving the PEC performance is not apparently related to the films’ electrical conductivity which had been widely believed, but is more likely due to the passivation of surface defects by the titanium dopants.« less

Preparation of Nanocrystalline Powders of ZrO2, Stabilized by Y2O3 Dobs for Ceramics

NASA Astrophysics Data System (ADS)

Petrunin, V. F.; Korovin, S. A.

The purpose of this study was to develop a synthesis conditions and produce samples of nanocrystalline zirconia powder in a high-temperature phase state. To increase the stability of this state at room temperature, Y2O3 was used as a dop in the two-stages chemical method including coprecipitation mixture of the corresponding hydroxides and air drying. To reduce agglomeration of nanoparticles during heat treatment of precursors the microwave oven instead of a muffle was used. Different characterisation methods have been used to determine that the obtained powders are nano-scale corresponds to a high-temperature tetragonal phase of ZrO2. It is shown that such nanocrystalline powders may be used to produce highly-dense nanoceramics.

Accumulated destructive effect of nanosecond repetitive voltage pulses on the insulated coatings of Fe-based nanocrystalline ribbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yu; Liu, Jinliang

2013-03-11

Fe-based nanocrystalline ribbon is widely employed in pulsed power devices and accelerators. A temperature accumulation model is put forward to explain the accumulated destructive effect of discharge plasma bombardment on the TiO{sub 2} coatings of nanocrystalline ribbon under 50 Hz/100 ns voltage pulses. Experimental results revealed that the plasma channel expansion caused by air breakdown in the coating crack heated the coating repetitively, and the coating temperature was increased and accumulated around the crack. The fact that repetitive voltage pulses were more destructive than a single pulse with the same amplitude was caused by the intensified coating ablation under themore » temperature accumulation effect.« less

Magnetic ageing study of high and medium permeability nanocrystalline FeSiCuNbB alloys

NASA Astrophysics Data System (ADS)

Lekdim, Atef; Morel, Laurent; Raulet, Marie-Ange

2017-04-01

increasing the energy efficiency is one of the most important issues in modern power electronic systems. In aircraft applications, the energy efficiency must be associated with a maximum reduction of mass and volume, so a high components compactness. A consequence from this compactness is the increase of operating temperature. Thus, the magnetic materials used in these applications, have to work at high temperature. It raises the question of the thermal ageing problem. The reliability of these components operating at this condition becomes a real problem which deserves serious interest. Our work takes part in this context by studying the magnetic material thermal ageing. The nanocrystalline materials are getting more and more used in power electronic applications. Main advantages of nanocrystalline materials compared to ferrite are: high saturation flux density of almost 1.25 T and low dynamic losses for low and medium frequencies. The nanocrystalline Fe73.5Cu1Nb3Si15.5B7 alloys have been chosen in our aging study. This study is based on monitoring the magnetic characteristics for several continuous thermal ageing (100, 150, 200 and 240 °C). An important experimental work of magnetic characterization is being done following a specific monitoring protocol. Elsewhere, X-Ray Diffraction and magnetostriction measurements were carried out to support the study of the anisotropy energies evolution with ageing. This latter is discussed in this paper to explain and give hypothesis about the ageing phenomena.

Influence of Cu-Ti thin film surface properties on antimicrobial activity and viability of living cells.

PubMed

Wojcieszak, Damian; Kaczmarek, Danuta; Antosiak, Aleksandra; Mazur, Michal; Rybak, Zbigniew; Rusak, Agnieszka; Osekowska, Malgorzata; Poniedzialek, Agata; Gamian, Andrzej; Szponar, Bogumila

2015-11-01

The paper describes properties of thin-film coatings based on copper and titanium. Thin films were prepared by co-sputtering of Cu and Ti targets in argon plasma. Deposited coatings consist of 90at.% of Cu and 10at.% of Ti. Characterization of the film was made on the basis of investigations of microstructure and physicochemical properties of the surface. Methods such as scanning electron microscopy, x-ray microanalysis, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, optical profilometry and wettability measurements were used to assess the properties of deposited thin films. An impact of Cu-Ti coating on the growth of selected bacteria and viability of the living cells (line L929, NCTC clone 929) was described in relation to the structure, surface state and wettability of the film. It was found that as-deposited films were amorphous. However, in such surroundings the nanocrystalline grains of 10-15nm and 25-35nm size were present. High surface active area with a roughness of 8.9nm, had an effect on receiving relatively high water contact angle value (74.1°). Such wettability may promote cell adhesion and result in an increase of the probability of copper ion transfer from the film surface into the cell. Thin films revealed bactericidal and fungicidal effects even in short term-contact. High activity of prepared films was directly related to high amount (ca. 51 %) of copper ions at 1+ state as x-ray photoelectron spectroscopy results have shown. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrical relaxation, optical and magnetic studies of nanocrystalline lithium ferrite synthesized by different chemical routes

NASA Astrophysics Data System (ADS)

Cheruku, Rajesh; Govindaraj, G.; Vijayan, Lakshmi

2017-12-01

The nanocrystalline lithium ferrite was synthesized by wet chemical methods such as solution combustion technique, sol-gel, and hydrothermal for a comparative study. Different characterization techniques like x-ray powder diffraction and thermal analysis were employed to confirm the structure and phase. Temperature-dependent Raman analysis was employed to classify the phonon modes associated with precise atomic motions existing in the synthesized materials. Morphology of sample surface was explored by scanning electron microscopy, and elemental analysis was done by energy dispersive spectroscopy analysis. The nanocrystalline nature of the materials was confirmed through transmission electron microscopy. Magnetic properties of these samples were explored through a vibrating sample magnetometer. Ac electrical impedance spectroscopy data were investigated using two Cole-Cole functions, and activation energies were calculated for all materials. Among them, solution combustion prepared lithium ferrite shows the highest conductivity and lowest activation energy.

Development of Nano-crystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Hai; Dong, Junhang; Lin, Jerry

2012-03-01

This is a final technical report for the first project year from July 1, 2005 to Jan 31, 2012 for DoE/NETL funded project DE-FC26-05NT42439: Development of Nanocrystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases. This report summarizes the technical progresses and achievements towards the development of novel nanocrystalline doped ceramic material-enabled optical fiber sensors for in situ and real time monitoring the gas composition of flue or hot gas streams involved in fossil-fuel based power generation and hydrogen production.

Spectroscopic Ellipsometry Studies of Thin Film a-Si:H/nc-Si:H Micromorph Solar Cell Fabrication in the p-i-n Superstrate Configuration

NASA Astrophysics Data System (ADS)

Huang, Zhiquan

Spectroscopic ellipsometry (SE) is a non-invasive optical probe that is capable of accurately and precisely measuring the structure of thin films, such as their thicknesses and void volume fractions, and in addition their optical properties, typically defined by the index of refraction and extinction coefficient spectra. Because multichannel detection systems integrated into SE instrumentation have been available for some time now, the data acquisition time possible for complete SE spectra has been reduced significantly. As a result, real time spectroscopic ellipsometry (RTSE) has become feasible for monitoring thin film nucleation and growth during the deposition of thin films as well as during their removal in processes of thin film etching. Also because of the reduced acquisition time, mapping SE is possible by mounting an SE instrument with a multichannel detector onto a mechanical translation stage. Such an SE system is capable of mapping the thin film structure and its optical properties over the substrate area, and thereby evaluating the spatial uniformity of the component layers. In thin film photovoltaics, such structural and optical property measurements mapped over the substrate area can be applied to guide device optimization by correlating small area device performance with the associated local properties. In this thesis, a detailed ex-situ SE study of hydrogenated amorphous silicon (a-Si:H) thin films and solar cells prepared by plasma enhanced chemical vapor deposition (PECVD) has been presented. An SE analysis procedure with step-by-step error minimization has been applied to obtain accurate measures of the structural and optical properties of the component layers of the solar cells. Growth evolution diagrams were developed as functions of the deposition parameters in PECVD for both p-type and n-type layers to characterize the regimes of accumulated thickness over which a-Si:H, hydrogenated nanocrystalline silicon (nc-Si:H) and mixed phase (a

Ferromagnetism appears in nitrogen implanted nanocrystalline diamond films

NASA Astrophysics Data System (ADS)

Remes, Zdenek; Sun, Shih-Jye; Varga, Marian; Chou, Hsiung; Hsu, Hua-Shu; Kromka, Alexander; Horak, Pavel

2015-11-01

The nanocrystalline diamond films turn to be ferromagnetic after implanting various nitrogen doses on them. Through this research, we confirm that the room-temperature ferromagnetism of the implanted samples is derived from the measurements of magnetic circular dichroism (MCD) and superconducting quantum interference device (SQUID). Samples with larger crystalline grains as well as higher implanted doses present more robust ferromagnetic signals at room temperature. Raman spectra indicate that the small grain-sized samples are much more disordered than the large grain-sized ones. We propose that a slightly large saturated ferromagnetism could be observed at low temperature, because the increased localization effects have a significant impact on more disordered structure.

Plasma metallurgical production of nanocrystalline borides and carbides

NASA Astrophysics Data System (ADS)

Galevsky, G. V.; Rudneva, V. V.; Cherepanov, A. N.; Galevsky, S. G.; Efimova, K. A.

2016-09-01

he experience in production and study of properties of nanocrystalline borides and chromium carbides, titanium, silicon was summarized. The design and features of the vertical three-jet once-through reactor with power 150 kW, used in the plasma metallurgical production, was described. The technological, thermotechnical and resource characteristics of the reactor were identified. The parameters of borides and carbides synthesis, their main characteristics in the nanodispersed state and equipment-technological scheme of production were provided. Evaluation of engineering-and-economical performance of the laboratory and industrial levels of borides and carbides production and the state corresponding to the segment of the world market was carried out.

Non-toxic novel route synthesis and characterization of nanocrystalline ZnS{sub x}Se{sub 1−x} thin films with tunable band gap characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agawane, G.L., E-mail: agawaneganesh@gmail.com; Shin, Seung Wook; Vanalakar, S.A.

2014-07-01

Highlights: • A simple, inexpensive, and non-toxic CBD route is used to deposit ZnS thin films. • The ZnS{sub x}Se{sub 1−x} thin films formation takes place via annealing of ZnS thin films in Se atmosphere. • S/(S + Se) ratio found to be temperature dependent and easy tuning of band gap has been done by Se atom deposition. - Abstract: An environmentally benign chemical bath deposition (CBD) route was employed to deposit zinc sulfide (ZnS) thin films. The CBD-ZnS thin films were further selenized in a furnace at various temperatures viz. 200, 300, 400, and 500 °C and the S/(Smore » + Se) ratio was found to be dependent on the annealing temperature. The effects of S/(S + Se) ratio on the structural, compositional and optical properties of the ZnS{sub x}Se{sub 1−x} (ZnSSe) thin films were investigated. EDS analysis showed that the S/(S + Se) ratio decreased from 0.8 to 0.6 when the film annealing temperature increased from 200 to 500 °C. The field emission scanning electron microscopy and atomic force microscopy studies showed that all the films were uniform, pin hole free, smooth, and adhered well to the glass substrate. The X-ray diffraction study on the ZnSSe thin films showed the formation of the cubic phase, except for the unannealed ZnSSe thin film, which showed an amorphous phase. The X-ray photoelectron spectroscopy revealed Zn-S, Zn-Se, and insignificant Zn-OH bonds formation from the Zn 2p{sub 3/2}, S 2p, Se 3d{sub 5/2}, and O 1s atomic states, respectively. The ultraviolet–visible spectroscopy study showed ∼80% transmittance in the visible region for all the ZnSSe thin films having various absorption edges. The tuning of the band gap energy of the ZnSSe thin films was carried out by selenizing CBD-ZnS thin films, and as the S/(S + Se) ratio decreased from 0.8 to 0.6, the band gap energy decreased from 3.20 to 3.12 eV.« less

Nano-crystalline thin and nano-particulate thick TiO{sub 2} layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, P.; Sengupta, D.; CSIR-Central Mechanical Engineering Research Institute, Academy of Scientific and Innovative Research

Highlights: • Thin TiO{sub 2} layer is deposited on conducting substrate using sol–gel based dip coating. • TiO{sub 2} nano-particles are synthesized using hydrothermal route. • Thick TiO{sub 2} particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO{sub 2} passivation layer is introduced between the mesoporous TiO{sub 2} nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effectmore » of passivation layer, other two DSSCs are also developed separately using TiO{sub 2} nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO{sub 2} compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO{sub 2} layer in between the mesoporous TiO{sub 2} nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons.« less

On the Formation of Lightweight Nanocrystalline Aluminum Alloys by Electrodeposition

DOE PAGES

Hilty, Robert D.; Masur, Lawrence J.

2017-08-08

New nanocrystalline aluminum alloys have been fabricated by electrodeposition. These are thermodynamically stable alloys of Al-Mn and Al-Zr with grain sizes < 100nm. Al-Mn and Al-Zr alloys are characterized here showing high strength (up to 1350 MPa) and hardness (up to 450 HVN) while maintaining the specific gravity of Al. Smooth and dense deposits plated from ionic liquids, such as EMIM:Cl (1-Ethyl-3-methylimidazolium chloride), can develop to thicknesses of 1mm or more.

Effect of ultrasonic treatment and temperature on nanocrystalline TiO 2

NASA Astrophysics Data System (ADS)

Kim, D. H.; Ryu, H. W.; Moon, J. H.; Kim, J.

Nanocrystalline TiO 2 particles were precipitated from the ethanol solution of titanium isopropoxide (Ti(O- iPr) 4) and H 2O 2 by refluxing at 80 °C for 48 h. The obtained particles were filtered and dried at 100 °C for 12 h. The dried powder itself, the sample with heating at 400 °C, and the sample with ultrasonically treating were prepared to investigate the effects of post treatments on materials characteristics and electrochemical properties of nanocrystalline TiO 2. The X-ray diffraction patterns of all of the samples were fitted well to the anatase phase. The field emission-TEM image of as-prepared sample shows a uniform spherical morphology with 5 nm particle size and the sample heated at 400 °C shows slightly increased particle size of about 10 nm while maintaining spherical shape. The sample treated with ultrasonic for 5 h or more at room temperature shows high aspect ratio particle shape with an average diameter of 5 nm and a length of 20 nm. According to the results of the electrochemical testing, as-prepared sample, the sample heated at 400 °C for 3 h, and the sample treated with ultrasonic show initial capacities of 270, 310 and 340 mAh g -1, respectively.

Immobilization of lysozyme-cellulose amide-linked conjugates on cellulose I and II cotton nanocrystalline preparations

USDA-ARS?s Scientific Manuscript database

Lysozyme was attached through an amide linkage between protein aspartate and glutamate residues to amino-glycine-cellulose (AGC), which was prepared by esterification of glycine to preparations of cotton nanocrystals (CNC). The nanocrystalline preparations were produced through acid hydrolysis and ...

Microstructure and optical properties of nanocrystalline Cu2O thin films prepared by electrodeposition.

PubMed

Jiang, Xishun; Zhang, Miao; Shi, Shiwei; He, Gang; Song, Xueping; Sun, Zhaoqi

2014-01-01

Cuprous oxide (Cu2O) thin films were prepared by using electrodeposition technique at different applied potentials (-0.1, -0.3, -0.5, -0.7, and -0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV-vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission.

Effect of phase composition on crystal texture formation in hot deformed nanocrystalline SmCo5 magnets

NASA Astrophysics Data System (ADS)

Ma, Qiang; Yue, Ming; Xu, Xiaochang; Zhang, Hongguo; Zhang, Dongtao; Zhang, Xuefeng; Zhang, Jiuxing

2018-05-01

In the present study, bulk anisotropic nanocrystalline SmCo5 magnets were prepared by hot press and subsequent hot deformation method. Effect of phase composition on texture and magnetic properties are presented, based on which the mechanism of plastic deformation and texture formation during the hot deformation process is discussed. The SmCo5 magnets were prepared by hot deformation, excessive Sm of 2.5 wt% and 10 wt% was added to compensate the weight loss due to Sm evaporation. Our analyses reveal that the phase composition is one of the most important parameters that determine the texture of SmCo5 magnets. It is therefore suggested that the existence of 2:17 phase and its phase transformation undermined the crystal texture formation as well as the magnetic properties of nanocrystalline SmCo5 magnets.

Structural Evolution during Milling, Annealing, and Rapid Consolidation of Nanocrystalline Fe–10Cr–3Al Powder

PubMed Central

Kumar, Rajiv; Bakshi, S. R.; Joardar, Joydip; Parida, S.; Raja, V. S.; Singh Raman, R. K.

2017-01-01

Structural changes during the deformation-induced synthesis of nanocrystalline Fe–10Cr–3Al alloy powder via high-energy ball milling followed by annealing and rapid consolidation by spark plasma sintering were investigated. Reduction in crystallite size was observed during the synthesis, which was associated with the lattice expansion and rise in dislocation density, reflecting the generation of the excess grain boundary interfacial energy and the excess free volume. Subsequent annealing led to the exponential growth of the crystallites with a concomitant drop in the dislocation density. The rapid consolidation of the as-synthesized nanocrystalline alloy powder by the spark plasma sintering, on the other hand, showed only a limited grain growth due to the reduction of processing time for the consolidation by about 95% when compared to annealing at the same temperature. PMID:28772633

Magnetic properties of FeCuNbSiB nanocrystalline alloy powder cores using ball-milled powder

NASA Astrophysics Data System (ADS)

Kim, G. H.; Noh, T. H.; Choi, G. B.; Kim, K. Y.

2003-05-01

Cold-pressed nanocrystalline powder cores were fabricated using powders of nanocrystalline ribbons which were ball milled for short time. Their magnetic properties at high frequency were measured. The powder size ranges from 20 to 850 μm and the contents of the glass binder are between 1 and 8 wt %. For cores composed of large particles of 300-850 μm with 5 wt % glass binder, we obtained a stable permeability of 100 up to 800 kHz, a maximum level 31 of quality factor at frequency of 50 kHz, and 320 mW/cm3 core loss at f=50 kHz and Bm=0.1 T. This is mainly due to the good soft magnetic properties of the powders and the higher insulation of powder cores which cause low eddy current losses.

Simultaneous determination of epinephrene and paracetamol at copper-cobalt oxide spinel decorated nanocrystalline zeolite modified electrodes.

PubMed

Samanta, Subhajyoti; Srivastava, Rajendra

2016-08-01

In this study, CuCo2O4 and CuCo2O4 decorated nanocrystalline ZSM-5 materials were prepared. For comparative study, a series of MCo2O4 spinels were also prepared. Materials were characterized by the complementary combination of X-ray diffraction, N2-adsorption, UV-visible, and electron microscopic techniques. A simple and rapid method for the simultaneous determination of paracetamol and epinephrine at MCo2O4 spinels modified electrodes is presented in this manuscript. Among the materials investigated in this study, CuCo2O4 decorated nanocrystalline ZSM-5 exhibited the highest electrocatalytic activity with excellent stability, sensitivity, and selectivity. Analytical performance of the sensor was demonstrated in the determination of epinephrine and paracetamol in the commercial pharmaceutical samples. Copyright © 2016 Elsevier Inc. All rights reserved.

Osteoblast adhesion, migration, and proliferation variations on chemically patterned nanocrystalline diamond films evaluated by live-cell imaging.

PubMed

Broz, Antonin; Ukraintsev, Egor; Kromka, Alexander; Rezek, Bohuslav; Hubalek Kalbacova, Marie

2017-05-01

Cell fate modulation by adapting the surface of a biocompatible material is nowadays a challenge in implantology, tissue engineering as well as in construction of biosensors. Nanocrystalline diamond (NCD) thin films are considered promising in these fields due to their extraordinary physical and chemical properties and diverse ways in which they can be modified structurally and chemically. The initial cell distribution, the rate of cell adhesion, distance of cell migration and also the cell proliferation are influenced by the NCD surface termination. Here, we use real-time live-cell imaging to investigate the above-mentioned processes on oxidized NCD (NCD-O) and hydrogenated NCD (NCD-H) to elucidate cell preference to the NCD-O especially on surfaces with microscopic surface termination patterns. Cells adhere more slowly and migrate farther on NCD-H than on NCD-O. Cells seeded with a fetal bovine serum (FBS) supplement in the medium move across the surface prior to adhesion. In the absence of FBS, the cells adhere immediately, but still exhibit different migration and proliferation on NCD-O/H regions. We discuss the impact of these effects on the formation of cell arrays on micropatterned NCD. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1469-1478, 2017. © 2017 Wiley Periodicals, Inc.

Rare-earth doped gadolinia based phosphors for potential multicolor and white light emitting deep UV LEDs.

PubMed

Bedekar, Vinila; Dutta, Dimple P; Mohapatra, M; Godbole, S V; Ghildiyal, R; Tyagi, A K

2009-03-25

Gadolinium oxide host and europium/dysprosium/terbium doped gadolinium oxide nanoparticles were synthesized using the sonochemical technique. Gadolinium oxide nanocrystals were also co-doped with total 2 mol% of Eu(3+)/Dy(3+),Eu(3+)/Tb(3+),Dy(3+)/Tb(3+), and also Eu(3+)/Dy(3+)/Tb(3+) ions, by the same method. The nanoparticles obtained were characterized using powder x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. The size of the particles ranged from 15 to 30 nm. The triple doped samples showed multicolor emission on single wavelength excitation. The photoluminescence results were correlated with the lifetime data to get an insight into the luminescence and energy transfer processes taking place in the system. On excitation at 247 nm, the novel nanocrystalline Gd(2)O(3):RE (RE = Dy, Tb) phosphor resulted in having very impressive CIE chromaticity coordinates of x = 0.315 and y = 0.316, and a correlated color temperature of 6508 K, which is very close to standard daylight.

Doping of vanadium to nanocrystalline diamond films by hot filament chemical vapor deposition

PubMed Central

2012-01-01

Doping an impure element with a larger atomic volume into crystalline structure of buck crystals is normally blocked because the rigid crystalline structure could not tolerate a larger distortion. However, this difficulty may be weakened for nanocrystalline structures. Diamonds, as well as many semiconductors, have a difficulty in effective doping. Theoretical calculations carried out by DFT indicate that vanadium (V) is a dopant element for the n-type diamond semiconductor, and their several donor state levels are distributed between the conduction band and middle bandgap position in the V-doped band structure of diamond. Experimental investigation of doping vanadium into nanocrystalline diamond films (NDFs) was first attempted by hot filament chemical vapor deposition technique. Acetone/H2 gas mixtures and vanadium oxytripropoxide (VO(OCH2CH2CH3)3) solutions of acetone with V and C elemental ratios of 1:5,000, 1:2,000, and 1:1,000 were used as carbon and vanadium sources, respectively. The resistivity of the V-doped NDFs decreased two orders with the increasing V/C ratios. PMID:22873631

Phase fields of nickel silicides obtained by mechanical alloying in the nanocrystalline state

NASA Astrophysics Data System (ADS)

Datta, M. K.; Pabi, S. K.; Murty, B. S.

2000-06-01

Solid state reactions induced by mechanical alloying (MA) of elemental blends of Ni and Si have been studied over the entire composition range of the Ni-Si system. A monotonous increase of the lattice parameter of the Ni rich solid solution, Ni(Si), is observed with refinement of crystallite size. Nanocrystalline phase/phase mixtures of Ni(Si), Ni(Si)+Ni31Si12, Ni31Si12+Ni2Si, Ni2Si+NiSi and NiSi+Si, have been obtained during MA, over the composition ranges of 0-10, 10-28, 28-33, 33-50, and >50 at. % Si, respectively. The results clearly suggest that only congruent melting phases, Ni31Si12, Ni2Si, and NiSi form, while the formation of noncongruent melting phases, Ni3Si, Ni3Si2, and NiSi2, is bypassed in the nanocrystalline state. The phase formation during MA has been discussed based on thermodynamic arguments. The predicted phase fields obtained from effective free energy calculations are quite consistent with those obtained during MA.

Transport, electronic, and structural properties of nanocrystalline CuAlO2 delafossites

NASA Astrophysics Data System (ADS)

Durá, O. J.; Boada, R.; Rivera-Calzada, A.; León, C.; Bauer, E.; de la Torre, M. A. López; Chaboy, J.

2011-01-01

This work reports on the effect of grain size on the electrical, thermal, and structural properties of CuAlO2 samples obtained by solid-state reaction combined with ball milling. Electrical characterization made in microcrystalline and nanocrystalline samples shows that the electrical conductivity decreases several orders of magnitude for the nanocrystalline samples, and, in addition, there is a large discrepancy between the activation energies associated to thermoelectric power ES. The study of the Cu K-edge x-ray absorption spectra of the CuAlO2 samples shows that the local structure around Cu is preserved after the sintering process, indicating that the observed behavior of the electrical conductivity is of intrinsic origin. Complex conductivity measurements as a function of frequency allow us to discard grain-boundaries effects on the electrical transport. Thus, the changes in σ(T) and S(T) are interpreted in terms of charge localization in the framework of small polarons. This is in agreement with the analysis of the near-edge region of the absorption spectra, which indicates that sintering favors the Cu-O hybridization. As a consequence, oxygen atoms progressively lose their capability of trapping holes, and the electrical conductivity is also enhanced.

Phase-field model with plastic flow for grain growth in nanocrystalline material

NASA Astrophysics Data System (ADS)

Steinbach, Ingo; Song, Xiaoyan; Hartmaier, Alexander

2010-01-01

A phase-field model is presented which considers the accumulation of structural defects in grain boundaries by an isotropic eigenstrain associated with the grain boundaries. It is demonstrated that the elastic energy caused by dilatation of the grain boundary with respect to the bulk crystal contributes largely to the grain boundary energy. The sign of this contribution can be both positive and negative dependent on the local stress state in the grain boundary. Self-diffusion of atoms is taken into account to relax the stress caused by the dilatation of the grain boundary. Application of the model to discontinuous grain growth in pure nanocrystalline cobalt material is presented. Linear grain growth is found in the nanocrystalline state, which is explained by the interpretation of grain boundary motion as a diffusive process defining an upper limit of the grain boundary velocity independent of the grain boundary curvature but dependent on temperature. The transition to regular grain growth at a critical temperature, as observed experimentally, is explained by the drop of theoretical grain boundary velocity due to its mean curvature during coarsening of the nanograin structure below the maximum velocity.

Size dependence of nanoscale wear of silicon carbide

Treesearch

Chaiyapat Tangpatjaroen; David Grierson; Steve Shannon; Joseph E. Jakes; Izabela Szlufarska

2017-01-01

Nanoscale, single-asperity wear of single-crystal silicon carbide (sc- SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native...

Immobilization of lysozyme-cellulose amide-linked conjugates on cellulose i and ii cotton nanocrystalline preparations

USDA-ARS?s Scientific Manuscript database

Lysozyme was attached through an amide linkage between some of the protein’s aspartate and glutamate residues to amino-glycine-cellulose (AGC), which was prepared by esterification of glycine to preparations of cotton nanocrystals (CNC). The nanocrystalline preparations were produced through acid h...

Room temperature aerobic oxidation of amines by a nanocrystalline ruthenium oxide pyrochlore nafion composite catalyst.

PubMed

Venkatesan, Shanmuganathan; Kumar, Annamalai Senthil; Lee, Jyh-Fu; Chan, Ting-Shan; Zen, Jyh-Myng

2012-05-14

The aerobic oxidation of primary amines to their respective nitriles has been carried out at room temperature using a highly reusable nanocrystalline ruthenium oxide pyrochlore Nafion composite catalyst (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water-soluble nanocrystalline cellulose films with highly transparent and oxygen barrier properties.

PubMed

Cheng, Shaoling; Zhang, Yapei; Cha, Ruitao; Yang, Jinliang; Jiang, Xingyu

2016-01-14

By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food.

Analysis of Distribution of Polyvinyl Alcohol Hydrogel Nanocrystalline by using SAXS Synchrotron

NASA Astrophysics Data System (ADS)

Sunaryono; Taufiq, A.; Mufti, N.; Hidayat, N.; Rugmai, S.; Soontaranon, S.; Putra, E. G. R.; Darminto

2017-05-01

Polyvinyl alcohol (PVA) hydrogel has been successfully synthesized through freezing-thawing (F-T) process by using time-variation. This work is aimed to investigate the distribution of nanocrystalline from the hydrogel. Fourier Transform Infrared (FTIR) Spectroscopy, Differential Thermal Analysis/Thermogravimetric (DTA/TG), and Synchrotron Small-Angle X-ray Scattering (SAXS) were used as the instruments in characterizing the PVA hydrogel, respectively to observe the frequency of absorption, thermal degradation, and structural dimensions. The functional groups which represent the PVA polymer chains were verified on the wavenumber of 1450-1480 cm-1 and 850-870 cm-1 which is in accordance with the stretching of -CH2 vibration mode. The absorption band of PVA polymer chains was also found on the wavenumber of 1090-1150 cm-1 which is in accordance with the stretching of carboxyl vibration mode (CO), and this wavenumber gave a contribution towards the crystallinity of PVA polymer. Furthermore, the PVA polymer only interacted with the distilled water in the sample of PVA hydrogel without experiencing any chemical interactions between the PVA polymer and other substances. Meanwhile, the graphic of PVA hydrogel thermal degradation shows three thermal decompositions which are indicated by three areas in which there was sample weight loss. The second decomposition with sample weight loss was equivalent to 61.62%-73.04% occurred at the temperature of 282-376 °C which became the highest sample weight loss due to polymer chain degradation. Teubner-Strey and Beaucage models were used to analyze the characterization of structural dimension and distribution of PVA Hydrogel nanocrystalline with SAXS Synchrotron. With a high compatibility between the model data and the experiment, the average structural dimension of PVA hydrogel nanocrystalline is the equivalent of 3.96 nm, with an inter-crystalline average distance of 16.9 nm. These results indicate that PVA hydrogel is very

Low-Temperature Synthesis of Superconducting Nanocrystalline MgB 2

DOE PAGES

Lu, Jun; Xiao, Zhili; Lin, Qiyin; ...

2010-01-01

Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 ° C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

Toughness and strength of nanocrystalline graphene

DOE PAGES

Shekhawat, Ashivni; Ritchie, Robert O.

2016-01-28

Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects—grain boundaries and grain-boundary triple junctions—that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with ‘weakest-link’ statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidatemore » the nanoscale origins of the grain-size dependence of its strength and toughness. Lastly, our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials.« less

Controlling Directional Liquid Motion on Micro- and Nanocrystalline Diamond/β-SiC Composite Gradient Films.

PubMed

Wang, Tao; Handschuh-Wang, Stephan; Huang, Lei; Zhang, Lei; Jiang, Xin; Kong, Tiantian; Zhang, Wenjun; Lee, Chun-Sing; Zhou, Xuechang; Tang, Yongbing

2018-01-30

In this Article, we report the synthesis of micro- and nanocrystalline diamond/β-SiC composite gradient films, using a hot filament chemical vapor deposition (HFCVD) technique and its application as a robust and chemically inert means to actuate water and hazardous liquids. As revealed by scanning electron microscopy, the composition of the surface changed gradually from pure nanocrystalline diamond (hydrophobic) to a nanocrystalline β-SiC surface (hydrophilic). Transmission electron microscopy and Raman spectroscopy were employed to determine the presence of diamond, graphite, and β-SiC phases. The as-prepared gradient films were evaluated for their ability to actuate water. Indeed, water was transported via the gradient from the hydrophobic (hydrogen-terminated diamond) to the hydrophilic side (hydroxyl-terminated β-SiC) of the gradient surface. The driving distance and velocity of water is pivotally influenced by the surface roughness. The nanogradient surface showed significant promise as the lower roughness combined with the longer gradient yields in transport distances of up to 3.7 mm, with a maximum droplet velocity of nearly 250 mm/s measured by a high-speed camera. As diamond and β-SiC are chemically inert, the gradient surfaces can be used to drive hazardous liquids and reactive mixtures, which was signified by the actuation of hydrochloric acid and sodium hydroxide solution. We envision that the diamond/β-SiC gradient surface has high potential as an actuator for water transport in microfluidic devices, DNA sensors, and implants, which induce guided cell growth.

Novel development of nanocrystalline kesterite Cu2ZnSnS4 thin film with high photocatalytic activity under visible light illumination

NASA Astrophysics Data System (ADS)

Apostolopoulou, Andigoni; Mahajan, Sandip; Sharma, Ramphal; Stathatos, Elias

2018-01-01

Cu2ZnSnS4 (CZTS) represents a promising p-type direct band gap semiconductor with large absorption coefficient in the visible region of solar light. In the present study, a kesterite CZTS nanocrystalline film, with high purity, was successfully synthesized via the combination of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) technique. The morphology and structural properties of the CZTS films were characterized by FE-SEM microscopy, porosimetry in terms of Brunauer-Emmett-Teller (BET) technique, X-ray diffraction and Raman spectroscopy. The as-prepared films under mild heat treatment at 250 °C in the presence of sulfur atmosphere exhibited fine nanostructure with 35 nm average particle size, high specific surface area of 53 m2/g and 9 nm pore diameter. The photocatalytic activity of the films was examined to the degradation of Basic Blue 41 (BB-41) and Acid Orange 8 (AO-8) organic azo dyes under visible light irradiation, demonstrating 97.5% and 70% discoloration for BB-41 and AO-8 respectively. Reusability of the CZTS films was also tested proving good stability over several repetitions. The reduction of photocatalyst's efficiency after three successive repetitions didn't exceed 5.6% and 8.5% for BB-41 and AO-8 respectively.

Nanocrystalline Cobalt-Phosphorous Electroplating as an Alternative to Hard Chromium Electroplating

DTIC Science & Technology

2012-08-01

Validate pulsed electrodeposition of Nanocrystalline Cobalt-Phosphorous (nCoP) alloy coatings as a Hard Chrome electroplating alternative for DoD...limits Cr+6  Cathode Efficiency Cr Plating *Co PEL is 20 µg/m3  ≈5X faster than Chrome plating  Increased throughput  One nCo-P tank can...replace several hard chrome tanks  Bath is Stable nCoP Plating Approaches 100% Efficiency  Process Comparison CoP Technical Approach

Nanocrystalline diamond coatings for mechanical seals applications.

PubMed

Santos, J A; Neto, V F; Ruch, D; Grácio, J

2012-08-01

A mechanical seal is a type of seal used in rotating equipment, such as pumps and compressors. It consists of a mechanism that assists the connection of the rotating shaft to the housings of the equipments, preventing leakage or avoiding contamination. A common cause of failure of these devices is end face wear out, thus the use of a hard, smooth and wear resistant coating such as nanocrystalline diamond would be of great importance to improve their working performance and increase their lifetime. In this paper, different diamond coatings were deposited by the HFCVD process, using different deposition conditions. Additionally, the as-grown films were characterized for, quality, morphology and microstructure using scanning electron microscopy (SEM) and Raman spectroscopy. The topography and the roughness of the films were characterized by atomic force microscopy (AFM).

Limitation of biocompatibility of hydrated nanocrystalline hydroxyapatite

NASA Astrophysics Data System (ADS)

Minaychev, V. V.; Teleshev, A. T.; Gorshenev, V. N.; Yakovleva, M. A.; Fomichev, V. A.; Pankratov, A. S.; Menshikh, K. A.; Fadeev, R. S.; Fadeeva, I. S.; Senotov, A. S.; Kobyakova, M. I.; Yurasova, Yu B.; Akatov, V. S.

2018-04-01

Nanostructured hydroxyapatite (HA) in the form of hydrated paste is considered to be a promising material for a minor-invasive surgical curing of bone tissue injure. However questions about adhesion of cells on this material and its biocompatibility still remain. In this study biocompatibility of paste-formed nanosized HA (nano-HA) by in vitro methods is investigated. Nano-HA (particles sized about 20 nm) was synthesized under conditions of mechano-acoustic activation of an aqueous reaction mixture of ammonium hydrophosphate and calcium nitrate. It was ascertained that nanocrystalline paste was not cytotoxic although limitation of adhesion, spreading and growth of the cells on its surface was revealed. The results obtained point on the need of modification of hydrated nano-HA in the aims of increasing its biocompatibility and osteoplastic potential.

Recoil-free Fraction in Amorphous and Nanocrystalline Aluminium Based Alloys

NASA Astrophysics Data System (ADS)

Sitek, Jozef

2008-10-01

Aluminium based rapidly quenched alloys of nominal composition Al90Fe7Nb3 and Al94Fe2V4 were studied by Mössbauer spectroscopy. We have measured the recoil-free fraction and thermal shift at room and liquid nitrogen temperature. The frequency modes of atomic vibrations were determined and consequently the characteristic Debye temperature was derived. Characteristic temperature calculated from f-factor was lower than those fitted from second order Doppler shift. This indicates the presence of different frequency modes for amorphous and nanocrystalline states.

Mechanically Driven Grain Boundary Relaxation: A Mechanism for Cyclic Hardening in Nanocrystalline Ni

DTIC Science & Technology

2012-01-01

enforce a minimum separation distance (25% of the simulation cell length) between grain nucleation sites, giving more equiaxed grains and a tighter...de d by [ M as sa ch us et ts I ns tit ut e of T ec hn ol og y] a t 1 5: 36 1 2 Fe br ua ry 2 01 2 electrodeposited nanocrystalline Ni with

Nanocrystalline cellulose as an eco-friendly reinforcing additive to polyurethane coating for augmented anticorrosive behavior.

PubMed

Abd El-Fattah, M; Hasan, Abdulraheim M A; Keshawy, Mohamed; El Saeed, Ashraf M; Aboelenien, Ossama M

2018-03-01

Nanocrystalline cellulose (NCC) and micro-powdered cellulose (MPC) were extracted from rice straw by mechanical and alkali treatment methods, then characterized via infrared spectroscopy and dynamic light scattering. A series of polyurethane nanocrystalline cellulose composite (PNCCC) and polyurethane micro-powdered cellulose composite (PMPCC) coatings were prepared with various loading levels of NCC and MPC from 0.5 to 2.0 wt.%, and the coatings were applied onto the pretreated mild steel substrate at room temperature. The results showed that the NCC and MPC influenced positively the studied properties of the polyurethane coating; furthermore the most pronounced anticorrosive properties were obtained at 1 wt.% NCC and MPC, as confirmed by open circuit potential (OCP) study, electrochemical impedance spectroscopy (EIS) study and salt spray test. However, the optimum enhancement of mechanical properties was found at 1.5 wt.% loading level, after which further loading of NCC and MPC led to the reduction in the mechanical properties. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evaluation of structural, morphological and magnetic properties of CuZnNi (CuxZn0.5-xNi0.5Fe2O4) nanocrystalline ferrites for core, switching and MLCI's applications

NASA Astrophysics Data System (ADS)

Akhtar, Majid Niaz; Khan, Muhammad Azhar; Ahmad, Mukhtar; Nazir, M. S.; Imran, M.; Ali, A.; Sattar, A.; Murtaza, G.

2017-01-01

The influence of Cu substitution on the structural and morphological characteristics of Ni-Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni-Zn nanoferrites. The nanocrystalline ferrites of Cu substituted CuxZn0.5-xNi0.5Fe2O4 ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni-Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu-Zn-Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35-46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M-H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni-Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni-Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI's due to variety of the soft magnetic characteristics.

Silicon thin-film transistor backplanes on flexible substrates

NASA Astrophysics Data System (ADS)

Kattamis, Alexis Z.

Flexible large area electronics, especially for displays, is a rapidly growing field. Since hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) have become the industry standard for liquid crystal displays, it makes sense that they be used in any transition from glass substrates to flexible substrates. The goal of this thesis work was to implement a-Si:H backplane technology on stainless steel and clear plastic substrates, with minimal recipe changes to ensure high device quality. When fabricating TFTs on flexible substrates many new issues arise, from thin-film fracture to overlay alignment errors. Our approach was to maintain elevated deposition temperatures (˜300°C) and engineer methods to minimize these problems, rather than reducing deposition temperatures. The resulting TFTs exhibit more stable operation than their low temperature counterparts and are therefore similar to the TFTs produced on glass. Two display projects using a-Si:H TFTs will be discussed in detail. They are an active-matrix organic light emitting display (AMOLED) on stainless steel and an active-matrix electrophoretic display (AMEPD) on clear plastic, with TFTs deposited at 250°C-280°C. Achieving quality a-Si:H TFTs on these substrates required addressing a host of technical challenges, including surface roughness and feature misalignment. Nanocrystalline silicon (nc-Si) was also implemented on a clear plastic substrate as a possible alternative to a-Si:H. nc-Si:H TFTs can be deposited using the same techniques as a-Si:H but yield carrier mobilities one order of magnitude greater. Their large mobilities could enable high resolution OLED displays and system-on-panel electronics.

Challenges in quantitative crystallographic characterization of 3D thin films by ACOM-TEM.

PubMed

Kobler, A; Kübel, C

2017-02-01

Automated crystal orientation mapping for transmission electron microscopy (ACOM-TEM) has become an easy to use method for the investigation of crystalline materials and complements other TEM methods by adding local crystallographic information over large areas. It fills the gap between high resolution electron microscopy and electron back scatter diffraction in terms of spatial resolution. Recent investigations showed that spot diffraction ACOM-TEM is a quantitative method with respect to sample parameters like grain size, twin density, orientation density and others. It can even be used in combination with in-situ tensile or thermal testing. However, there are limitations of the current method. In this paper we discuss some of the challenges and discuss solutions, e.g. we present an ambiguity filter that reduces the number of pixels with a '180° ambiguity problem'. For that an ACOM-TEM tilt series of nanocrystalline Pd thin films with overlapping crystallites was acquired and analyzed. Copyright © 2017. Published by Elsevier B.V.

Formation of 4H-closely packed structure in thin films of metastable nanocrystalline Co 13Cu 87 alloy

NASA Astrophysics Data System (ADS)

Khalyapin, D. L.; Kim, J.; Stolyar, S. V.; Turpanov, I. A.; Kim, P. D.; Kim, I.

2003-11-01

The crystal structure of the thin films of metastable Co 13Cu 87 alloy prepared by magnetron sputtering was investigated by transmission electron microscope. As-deposited films have a nanocrystal structure with an fcc lattice. As a result of the prolonged ion polishing with a beam of Ar ions with the energy of 4.7 keV, the four-layer 4H dhcp structure was formed.

Enhanced growth and osteogenic differentiation of human osteoblast-like cells on boron-doped nanocrystalline diamond thin films.

PubMed

Grausova, Lubica; Kromka, Alexander; Burdikova, Zuzana; Eckhardt, Adam; Rezek, Bohuslav; Vacik, Jiri; Haenen, Ken; Lisa, Vera; Bacakova, Lucie

2011-01-01

Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH(4):H(2) gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000 ± 14,000 and 152,000 ± 10,000 cells/cm(2), respectively, compared to 113,000 ± 10,000 cells/cm(2) on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells.

Enhanced Growth and Osteogenic Differentiation of Human Osteoblast-Like Cells on Boron-Doped Nanocrystalline Diamond Thin Films

PubMed Central

Grausova, Lubica; Kromka, Alexander; Burdikova, Zuzana; Eckhardt, Adam; Rezek, Bohuslav; Vacik, Jiri; Haenen, Ken; Lisa, Vera; Bacakova, Lucie

2011-01-01

Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH4:H2 gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000±14,000 and 152,000±10,000 cells/cm2, respectively, compared to 113,000±10,000 cells/cm2 on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells. PMID:21695172

Deformation Twins in Nanocrystalline Body-Centered Cubic Mo as Predicted by Molecular Dynamics Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Tonks; Bulent biner; Yongfeng Zhang

2012-10-01

This work studies deformation twins in nanocrystalline body-centered cubic Mo, including the nucleation and growth mechanisms as well as their effects on ductility, through molecular dynamics simulations. The deformation processes of nanocrystalline Mo are simulated using a columnar grain model with three different orientations. The deformation mechanisms identified, including dislocation slip, grain-boundary-mediated plasticity, deformation twins and martensitic transformation, are in agreement with previous studies. In (1 1 0) columnar grains, the deformation is dominated by twinning, which nucleates primarily from the grain boundaries by successive emission of twinning partials and thickens by jog nucleation in the grain interiors. Upon arrestmore » by a grain boundary, the twin may either produce continuous plastic strain across the grain boundary by activating compatible twinning/slip systems or result in intergranular failure in the absence of compatible twinning/slip systems in the neighboring grain. Multiple twinning systems can be activated in the same grain, and the competition between them favors those capable of producing continuous deformation across the grain boundary.« less

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

PubMed Central

Proust, Gwénaëlle; Trimby, Patrick; Piazolo, Sandra; Retraint, Delphine

2017-01-01

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized. PMID:28447998

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction.

PubMed

Proust, Gwénaëlle; Trimby, Patrick; Piazolo, Sandra; Retraint, Delphine

2017-04-01

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

Highly ordered, accessible and nanocrystalline mesoporous TiO₂ thin films on transparent conductive substrates.

PubMed

Violi, Ianina L; Perez, M Dolores; Fuertes, M Cecilia; Soler-Illia, Galo J A A

2012-08-01

Highly porous (V(mesopore) = 25-50%) and ordered mesoporous titania thin films (MTTF) were prepared on ITO (indium tin oxide)-covered glass by a fast two-step method. The effects of substrate surface modification and thermal treatment on pore order, accessibility and crystallinity of the MTTF were systematically studied for MTTF deposited onto bare and titania-modified ITO. MTTF exposed briefly to 550 °C resulted in highly ordered films with grid-like structures, enlarged pore size, and increased accessible pore volume when prepared onto the modified ITO substrate. Mesostructure collapse and no significant change in pore volume were observed for MTTF deposited on bare ITO substrates. Highly crystalline anatase was obtained for MTTF prepared on the modified-ITO treated at high temperatures, establishing the relationship between grid-like structures and titania crystallization. Photocatalytic activity was maximized for samples with increased crystallization and high accessible pore volume. In this manner, a simple way of designing materials with optimized characteristics for optoelectronic applications was achieved through the modification of the ITO surface and a controlled thermal treatment.

Excitation of luminescence of the nanoporous bioactive nanocrystalline carbonate-substituted hydroxyapatite for early tooth disease detection

NASA Astrophysics Data System (ADS)

Goloshchapov, D. L.; Minakov, D. A.; Domashevskaya, E. P.; Seredin, P. V.

This paper deals with the luminescence characteristics of an analogue of the mineral component of dental enamel of the nanocrystalline B-type carbonate-substituted hydroxyapatite (CHAP) with 3D defects (i.e. nanopores of ∼2-5 nm) on the nanocrystalline surface. The laser-induced luminescence (LIL) of the synthesized CHAP samples was in the range of ∼515 nm (∼2.4 eV) and is due to CO3 groups replacing the PO4 group. It was found that the intensity of the luminescence of the CHAP is caused by structurally incorporated CO3 groups in the HAP structure. Furthermore, the intensity of the luminescence also decreases as the number of the above intracentre defects (CO3) in the apatite structure declines. These results are potentially promising for developing the foundations for precise methods for the early detection of caries in human solid dental tissue.

Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization.

PubMed

Sinha, Godhuli; Ganguli, Dibyendu; Chaudhuri, Subhadra

2008-03-01

Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.

Osteoblastic cells trigger gate currents on nanocrystalline diamond transistor.

PubMed

Izak, Tibor; Krátká, Marie; Kromka, Alexander; Rezek, Bohuslav

2015-05-01

We show the influence of osteoblastic SAOS-2 cells on the transfer characteristics of nanocrystalline diamond solution-gated field-effect transistors (SGFET) prepared on glass substrates. Channels of these fully transparent SGFETs are realized by hydrogen termination of undoped diamond film. After cell cultivation, the transistors exhibit about 100× increased leakage currents (up to 10nA). During and after the cell delamination, the transistors return to original gate currents. We propose a mechanism where this triggering effect is attributed to ions released from adhered cells, which depends on the cell adhesion morphology, and could be used for cell culture monitoring. Copyright © 2015 Elsevier B.V. All rights reserved.

Bulk and nanocrystalline electron doped Gd0.15Ca0.85MnO3: Synthesis and magnetic characterization

NASA Astrophysics Data System (ADS)

Dhal, Lakshman; Chattarpal; Nirmala, R.; Santhosh, P. N.; Kumary, T. Geetha; Nigam, A. K.

2014-09-01

Polycrystalline Gd0.15Ca0.85MnO3 sample was prepared by solid state reaction method and nanocrystalline samples of different grain sizes of the same were prepared by sol-gel method. Phase purity and composition were verified by room temperature X-ray diffraction and SEM-EDAX analysis. Magnetization data of bulk Gd0.15Ca0.85MnO3 in 5 kOe field shows a peak at 119 K (TN) suggesting an antiferromagnetic transition. Nanocrystalline Gd0.15Ca0.85MnO3 sample ( 54 nm size) also shows a cusp at 107 K and a broad thermal hysteresis between field cooled cooling (FCC) and field cooled warming (FCW) data around this temperature. This thermal hysteresis suggests possible crystal structural transition. Field variation of magnetization of bulk Gd0.15Ca0.85MnO3 at 5 K shows a tendency to saturate, but yields a magnetic moment value of only 1.12 μB/f.u. in 70 kOe. The value of magnetization of nanocrystalline sample at 5 K in 70 kOe field is slightly larger and is 1.38 μB/f.u. which is probably due to the surface moments of the nanoparticle samples. Both the samples show Curie-Weiss-like behaviour in their paramagnetic state.

The effect of ultrasonic nanocrystalline surface modification on the high-frequency fretting wear behavior of AISI304 steel.

PubMed

Cho, In-Shik; Lee, Chang-Soon; Amanov, Auezhan; Pyoun, Young-Shik; Park, In-Gyu

2011-01-01

The fact that one of fundamental characteristics of fretting is the very small sliding amplitude dictates the unique feature of wear mechanism. Ultrasonic Nanocrystalline Surface Modification (UNSM) technology was applied in order to investigate its effect on the high-frequency fretting wear behavior of AISI304 steel. Its influence on the fretting wear is also reported in this paper with these treated and untreated samples. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. UNSM creates homogenous nanocrystalline structures as well on the surface. UNSM process is expected to eliminate or significantly retard the formation of fretting wear. Nanocrystalline structure generation after UNSM has been reported to produce its unique structure and to offer a variety of beneficial properties compared to conventionally treated materials. A deformed layer of 220 microm exhibits high dislocation density, where top layer transformed to a nanostructure of the grain size in 23 nm and mechanical twins were observed. Deformation-induced martensite was observed to form at the intersections of mechanical twins, whose volume fraction has increased up to 38.4% and wear loss rate at 800,000 cycles has decreased by 40%. In this paper, experimental results are discussed to elucidate potential mechanism of high-frequency fretting wear.

Method for producing nanocrystalline multicomponent and multiphase materials

DOEpatents

Eastman, Jeffrey A.; Rittner, Mindy N.; Youngdahl, Carl J.; Weertman, Julia R.

1998-01-01

A process for producing multi-component and multiphase nanophase materials is provided wherein a plurality of elements are vaporized in a controlled atmosphere, so as to facilitate thorough mixing, and then condensing and consolidating the elements. The invention also provides for a multicomponent and multiphase nanocrystalline material of specified elemental and phase composition having component grain sizes of between approximately 1 nm and 100 nm. This material is a single element in combination with a binary compound. In more specific embodiments, the single element in this material can be a transition metal element, a non-transition metal element, a semiconductor, or a semi-metal, and the binary compound in this material can be an intermetallic, an oxide, a nitride, a hydride, a chloride, or other compound.

Structure and properties of electrodeposited nanocrystalline Ni and Ni-Fe alloy continuous foils

NASA Astrophysics Data System (ADS)

Giallonardo, Jason Derek

This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or "growth faults", which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young's modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young's modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in

Influence of grain size on the mechanical properties of nano-crystalline copper; insights from molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Rida, A.; Makke, A.; Rouhaud, E.; Micoulaut, M.

2017-10-01

We use molecular dynamics simulations to study the mechanical properties of a columnar nanocrystalline copper with a mean grain size between 8.91 nm and 24 nm. The used samples were generated by using a melting cooling method. These samples were submitted to uniaxial tensile test. The results reveal the presence of a critical mean grain size between 16 and 20 nm, where there is an inversion in the conventional Hall-Petch tendency. This inversion is illustrated by the increase of flow stress with the increase of the mean grain size. This transition is caused by shifting of the deformation mechanism from dislocations to a combination of grain boundaries sliding and dislocations. Moreover, the effect of temperature on the mechanical properties of nanocrystalline copper has been investigated. The results show a decrease of the flow stress and Young's modulus when the temperature increases.

Micro and nanocrystalline diamond formation on reticulated vitreous carbon substrate

NASA Astrophysics Data System (ADS)

Diniz, A. V.; Trava-Airoldi, V. J.; Corat, E. J.; Ferreira, N. G.

2005-10-01

High diamond nucleation and a three-dimensional growth on reticulated vitreous carbon substrate are obtained by chemical vapor deposition. Scanning electron microscopy images show continuous films covering the whole substrate including the center of 3.5 mm thick porous samples. It is evident the nanocrystalline diamond (NCD) film formation on deeper substrate regions. The grain size can vary from nano to micro scale for deposition time of 20 h. Raman spectra of sample regions closer to filaments exhibit well-defined diamond line. For central regions of sample (depth between 1.0 and 2.0 mm) Raman spectra also confirm NCD film.