The molecular and crystalline structure of a new type of nanomaterial were presented. The method consisting of two stages - physical vapor deposition from the gas phase and thermal oxidation - contains layers with CuxO nanostructures especially CuO nanorods. High-resolution electron transmission microscopy and infrared spectroscopy measurements allowed for the determination of the crystalline and molecular structure of examined films. HRTEM research shows that nanorods are made of CuO, while infrared spectroscopy studies confirm the existence of CuO and Cu2O phase layers in the structure. The obtained material is widely used in various fields of science, including electronics, photovoltaics, sensors and biomedical engineering
CuO films compose of copper oxide nanorods and nanograins with fcc type of structure have been prepared by multistep PVD / thermal oxidation method at different temperatures of annealing (400, 500and 600 °C). Ni-C nanocatalyst films was the factor lowering temperature and duration time of thermal oxidation (in comparison with literature data for similar methods) in which nanorods have been obtained. Obtained nanostructural films (composed of 1D and 2D objects) were characterized with XRD, SEM, EDX and Raman spectroscopy. All applied methods proved that the CuO nanostructural film is formed due to thermal oxidation of prepared multilayer film.
In this paper, we present the results studies of CuO layers obtained in different thermal condition. The samples were prepared with composed PVD and thermal oxidation processes. Due to PVD process C-Ni layer on Cu, plate was prepared and such layer was annealed in thermal oxidation process at the temperatures 400 and 500 °C. These two kind of sensors showed different electrical responses on hydrogen and ammonia gases what was connected to different topography of the layers. The adsorption desorption mechanism of reacting gases with developed surface of CuO layer influences on the electrical response.
CuO nanorods with the breadth of 60÷120 nm and the length up to 10 µm were synthesized using PVD method and thermal oxidation process. After PVD process a thick film composed from small nickel nanoparticles embedded in carbonaceous matrix was formed on the pure Cu surface. During the next step, the obtained film was heated with rising temperature under the air and annealed at different temperatures for 30 minutes. As a result a surface layer with a complex structure was formed. Microscopic examination revealed the complexity of the investigated structure. SEM, TEM, EDX and XRD investigations were performed. High resolution TEM studies revealed the subtle structure of CuO nanowires that was grown of the granular surface of CuO layer. CuO nanowires characterized by varied length and diameter.
Carbon nanotube (CNT) films deposited on different porous silica substrates were studied by Scanning Electron Microscopy (SEM) and Raman Spectroscopy (RS). The films samples were prepared by a two-step method consisting of PVD and CVD processes. In the first step the nanocomposite Ni-C film was obtained by evaporation in dynamic vacuum from two separated sources of fullerenes and nickel acetate. Those films were deposited on porous silica and DLC/porous silica substrates. Analysis of SEM imaging showed that the obtained film are composed of carbon nanotubes, the distribution, size and quality of which depend on the type of substrate. The CNT films were studied by RS method to determine the influence of the substrate type on disordering of carbonaceous structure and quality of CNT in deposited films.
In this work molecular and crystalline structure of new type of nanocomposite films were investigated. These films compose of CNT decorated with palladium nanograins. They were prepared on a base of C-Ni films modified in CVD process. C-Ni nanocomposite films were obtained by PVD process and their modification by CVD leads to a growth of CNT film. CNTs-Ni or C-Ni films were treated with additional PVD process with palladium.
Nickel and palladium acetate and fulleren C60 are precursors of films in PVD process. FTIR spectroscopy was used to studied the molecular structure of film in every stage of preparation . The crystalline structure of these films was studied by X-ray diffraction. SEM (scanning electron microscopy) was applied to investigate film’s surface topography.
The thermal stability of two types of C-Pd films prepared in PVD process were studied. These films are composed of Pd nanograins embedded in a multiphase carbonaceous matrix. These films were distinguished by Pd content. These films were annealed in a range of temperatures 50÷1000°C. The structural, topographical and molecular changes were studied by scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods. The results show that investigated films are thermally stable up to 200°C.
The properties of nanocomposite palladium-nickel-multi-walled (Pd-Ni-MWCNT) films deposited on aluminum oxide (Al2O3) substrate have been prepared and investigated. These films were obtained by 3 step process consisted of PVD/CVD/PVD methods.
The morphology and structure of the obtained films were characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques at various stages of the film formation. EDX spectrometer was used to measurements of elements segregation in the obtained film. TEM and STEM (Scanning Transmission Electron Microscopy) observations showed MWCNTs decorated with palladium nanoparticles in the film obtained in the last step of film formation (final PVD process). The average size of the palladium nanoparticles observed both on MWCNTs and carbonaceous matrix does not exceed 5 nm. The research was conducted on the use of the obtained films as potential sensors of gases (e.g. H2, NH3, CO2) and bio-sensors or optical sensors.
A luminescent lamp with field emission cathode was constructed and tested. Phosphor excited by electrons from field emission cathode is the source of light. The cathode is covered with nickel-carbon film containing multilayer carbon nanotubes that enhance electron emission from the cathode. Results of luminance stability measurements are presented. Luminance of elaborated luminance lamp is high enough for lighting application. Long term stability (1000 hours) is satisfactory for mass lamp application. Initial short time decrease of luminance is still too high and it needs reduction.
The carbon nanotubes films on various type of porous Si substrate were prepared. Three methods of porous Si preparation electrolysis, wet etching with silver nitrate and with potassium hydroxide were used. CNTs films were obtained by two step method containing PVD and CVD process. These yield of field emission depended on the type of film. I-U characteristics and F-N plots are discussed for these films. The short-term stability of emission measurements results are also presented. Depending on technological parameters of Si etching the topography of samples is different and it affects on the emission currents intensity and the electric threshold field.
A series of test titanium electrodes, intended for a new generation of hydrogen and hydrogen compounds sensors was prepared. This new generation of hydrogen sensors is expected to operate in above normative conditions. In order to investigate the influence of temperature and moisture on titanium electrodes a series of experiments was conducted. Test samples were exposed to elevated levels of temperature (up to 165°C) and moisture (relative humidity up to 80%). These test allowed to measure resistivity as a function of temperature and to determine the long-term stability of electrical parameters of electrodes. Results of this studies will be used in fabrication of reliable electrodes for a new generation of hydrogen sensors.
C-Pd films were obtained by a two steps’ PVD/CVD method (Physical Vapor Deposition/Chemical Vapor Deposition). Investigations of Pd nanograins structure and carbon matrix structure were performed. Many types of substrates (Si, Si covered with DLC layer, Al2O3 plate and AAO membrane) with various developing specific surface area (SSA) were applied and the influence on this surface on obtained films C-Pd was studied. We present the results of Scanning Electron Microscopy (SEM) studies with SE (Secondary Electrons) and LABE (Low Angle Backscattered Electrons) modes. Depending on the substrate type it was possible to obtain many different films and structures with various structural features.
In this paper different structures of CNT layer cathode showing different electron emission characteristics depending on Ni concentration are presented. The cathode’s layers were obtained by PVD/CVD method. Nanocomposite C-Ni layer were prepared in PVD step. This C-Ni layer was precursor layer for CNT layer growth in CVD process. Prepared CNT layers were studied with SEM and TEM. Their emissive properties were investigated in means F-N theory. It was found that the threshold field for these emitters varies from 1,7 V/μm to 20 V/μm. For some types of CNT cathodes it is possible to obtain the emission current intensity 55μA at the electric field ~3 V/μm.
KEYWORDS: Nickel, Chemical vapor deposition, Carbon nanotubes, Scanning electron microscopy, Transmission electron microscopy, Carbon, Nanoparticles, Silicon, Electron microscopy, Quartz
SEM and TEM use in an investigation of CNT-Ni layers different properties is shown. We present the possibilities of
using different SEM modes (SE - secondary electrons, LABE - low angle backscattered electrons) for studies of C-Ni
and CNT-Ni layers topography, morphology and cross-sectional investigations (adhesion, pores size and shape,
uniformity). Correlation between concentration of Ni in studied layers and technological parameters as well as in a case
of CNT-Ni films correlations of Ni concentration and a diameter of carbon nanotubes are discussed.
TEM studies concentrate on structure of Ni nanograins in C-Ni layers and CNT-Ni layers, CNT structure and
defects, nanoonion structure. We present methods of determination of graphite plane number in MWCNTs, distance
between these planes, role of catalyst position in CNT growth and interaction between catalyst and substrate. EDS
method for qualitative analysis of Ni catalyst in these layers was also presented.
Field emission from carbon nanotubes films prepared on etched silicon is presented. The etched Si surface has hillockslike
form. CNTs films were obtained in two-step method consisting of physical vapor deposition and chemical vapor
deposition. For some samples CNTs growth mainly on the top of the hillocks. Field emission from these structures were
observed and emission current (at 25 V/μm ) was 0.01-0.03mA.
The current – voltage characteristics and an interpretation of observed emission were performed on base of Fowler-
Nordheim theory. The short-term stability measurement of emission were also performed.
The short range order around Pd atoms in nanometer-size grains embedded in carbonaceous films deposited with two-step
process: physical vapor deposition (PVD) followed by chemical vapour deposition (CVD) was studied. The Pd K-edge
X-ray Absorption Fine Structure Spectroscopy was applied. We have found that grains obtained in a sole PVD process
contained metallic fcc palladium or amorphous palladium oxide dependently on Pd concentration and duration time of
process. In the oxide fraction a short range order around Pd atoms was strongly reduced as compared to a reference PdO
powder. Subsequent CVD resulted in pure Pd fcc crystallites. The accompanying annealing was found to predominantly
determine the content and structure of formed Pd grains.
KEYWORDS: Microsoft Foundation Class Library, Carbon, Scanning electron microscopy, Palladium, Raman spectroscopy, Bacteria, Nanostructures, Neodymium, Electrons, Metals
In the studies presented we proposed a new application for nanocomposite carbon films (C-Pd). These films were
evaluated as an anode material for Microbial Fuel Cells (MFCs) used for electrical current generation. The results of
characterization of C-Pd films composed of carbon and palladium nanograins were obtained using the Physical Vapor
Deposition (PVD) method. The film obtained by this method exhibits a multiphase structure composed of fullerene
nanograins, amorphous carbon and palladium nanocrystals. Raman Spectroscopy (RS) and scanning electron microscopy
(SEM) are used to characterize the chemical composition, morphology and topography of these films.
We observed, for MFC with C-Pd anode, the highest electrochemical activity and maximal voltage density - 458 mV
(20,8 mV/cm2) for Proteus mirabilis, 426 mV (19,4 mV/cm2) for Pseudomonas aeruginosa and 652 mV (29,6 mV/cm2)
for sewage bacteria as the microbial catalyst.
We present results of Raman studies of CNT-Ni films obtained in two steps method. In the first step an initial
nanocomposite Ni-C film (produced by PVD method) was prepared. This initial film has multiphase composite-like
structure with nanograins of fullerenes, amorphous carbon and nickel. In the second step CNTs were obtained by CVD
method. In this process the initial films were placed in a quartz tube reactor where pyrolysis process were performed in
xylene. Decomposition of xylene at 650°C was occurred. Products of this CVD decomposition process take part in
nanotubes growth on Ni nanograins. These nanograins play a role of a catalyser of the growth process. SEM
observations showed that form of nanotubes obtained with the various CVD process parameters is similar.
Raman studies of initial films (obtained PVD process) confirm the presence of fullerenes C60 in and some forms of
graphite–like objects in the samples. Raman spectra of MWCNTs films contained: bands characteristic for carbon
nanotube’s vibrations.
KEYWORDS: Palladium, Hydrogen, Chemical vapor deposition, Scanning electron microscopy, Resistance, Sensors, Transmission electron microscopy, Carbon, Temperature metrology, Nanostructures
Structural, topographical and morphological changes of carbonaceous-palladium (C-Pd) films obtained by physical
vapor deposition /chemical vapor deposition (PVD/CVD) method were studied. Effect of changes in these properties
under the influence of CVD process temperature on the hydrogen sensitivity of these films is discussed. Scanning
electron microscopy (SEM) observations were used to investigate the topography and morphology of an initial
(PVD) film and the film modified in CVD process (PVD/CVD film) at different temperatures. The changes of film’s
morphology after modification performed at various temperatures (500, 550, 600, 650, 700 and 750°C) caused
changes in their resistance. The electrical measurements carried out in the presence of gas containing 1vol % of
hydrogen showed different sensing characteristics for various films. The highest hydrogen sensitivity and the fastest
response were observed for films modified at the temperature of 500°C and 550°C. In SEM images on surface of
these films palladium nanograins with different sizes were observed. For films modified at the temperatures higher
than 600°C Pd nanograins placed under superficial very thin carbonaceous layer were found.
Structural and field emission investigation results of carbonaceous films containing Ni nanocrystllities are presented. These films were prepared by Physical Vapor Deposition (PVD) method in which C60 and nickel acetate were evaporated from two separate sources and under with different technological conditions. Scanning Electron Microscope (SEM) was applied to study their morphology and topography of films. SEM images in low angel backscattered electrons (LABE) and secondary electrons (SE) mode were analyze to obtain information on a composition of observed objects. Many different types of films were studied by SEM and a field emission was measured for them. Field emission was studied in a vacuum chamber where film was a cathode and anode was flat metallic element.
The characterization NiN nanocrystals (N- number of atoms in a nanocrystal) embedded in carbonaceous matrices is presented. The physical vapor deposition method was used to prepare nanocrystals. Transmission electron microscopy (TEM), atomic force microscopy (AFM), chemical analysis methods and optical absorption spectroscopy have been used to study samples properties. A hypothetical structure of nanocrystals NiN (13
Irena Simkiene, Julija Sabataityte, Jurgis Babonas, Alfonsas Reza, Rita Szymczak, Henryk Szymczak, Marek Baran, Miroslaw Kozlowski, Stanislaw Gierlotka
The iron-containing silica films on Si substrates were prepared by sol-gel technique from precursors composed of
tetraethoxysilane (TEOS) solution in ethanol and FeCl3 water solution. The colloid solutions were deposited by spinning
on cleaned Si substrates and annealed in air, Ar, or H2 atmosphere. The samples were characterized by optical parameters
determined using spectroscopic ellipsometry (1-5 eV) and magnetic properties by measuring the temperature (4-300 K)
and field (up to 50 kOe) dependences of magnetic moment. The physical properties were correlated with sample
structure, which has been examined by atomic force microscope (AFM) and scanning electron microscope (SEM).
Using special thermogravimetry and sorptometry methods physicochemical properties of carbon nanotube surfaces were investigated. A numerical and analytical procedure for the evaluation of total heterogeneous properties on the basis of liquid thermodesorption from the sample surfaces under the quasi-equilibrium conditions are presented. The desorption energy distribution was derived from the mass loss Q-TG and the differential mass loss Q-DTG curves of thermodesorption of pre-adsorbed polar and apolar liquid films. It is shown that the samples are highly sensitive to benzene vapor because the mechanism of liquid adsorption depends largely on the active surface centers and molecular interactions. For the first time, the evaluation of the fractal dimensions of nanotubes using the sorptometry and thermogravimetry data is presented.
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