Search Results

11 - 20 of 213 items :

Clear All
Preparation and characterization of catalyst mix Fe-Co/MgO for carbon nanotubes growth

., Jeong, G.H., Hirata, T., Hatakeyama, R., Tohji, K., Motomiya, K. (2003). Single-walled carbon nanotubes produced by plasma-enhanced chemical vapor deposition. Chem.Phys.Lett. 381, 422-426. DOI: 10.1016/j.cplett.2003.10.007. Li, Y., Mann, D., Rolandi, M., Kim, W., Ural, A., Hung, S., Javey, A., Cao, J., Wang, D., Yenilmez, E., Wang, Q., Gibbons, J.F., Nishi, Y. & Dai, H. (2004). Preferential Growth of Semiconducting Single-Walled Carbon Nanotubes by a Plasma Enhanced CVD Method. Nano Lett. 4, 317-321. DOI: 10.1021/n1035097c

Open access
Synthesis of carbon nanotubes via chemical vapor deposition by using rareearth metals as catalysts

. (2008). Modifying CVD synthesized carbon nanotubes via the carbon feed rate. Physica E. 40, 2227-2230 DOI:10.1016/j.physe.2007.10.105. Steplewska, A., Jedrzejewski, R. & Borowiak-Palen, E. (2008). Preperation and characterization of catalyst mix FeCo/MgO for carbon nanotubes growth. Polish Journal of Chemical Technology. 10, 3-3. DOI: 10.2478/v10026-008-0028-0. Suh, W. H., Suslick, K. S., Stucky, G. D. & Suh, Y. H. (2009). Nanotechnology, nanotoxicology, and neuroscience. Progress in Neurobiology. 87(3), 133-70. DOI

Open access
Influence of substrate material on spectral properties and thermal quenching of photoluminescence of silicon vacancy colour centres in diamond thin films

-Vacancy Defects”, Advanced Materials vol. 21, no. 7 (2009), pp. 808-812. [7] R. J. Narayan, R. D. Boehm and A. V. Sumant, “Medical applications of diamond particles & surfaces”, Materials Today vol. 14, no. 4 (2011), pp. 154-163. [8] L. Yang, L. Zhang, T. J. Webster, “ and Nanobiomaterials,”Nanobiomaterials: State of the Art and Future Trends”, Advanced Engineering Materials vol. 13, no. 6 (2011), pp. B197-B217. [9] K. Iakoubovskii and G. J. Adriaenssens, “Optical detection of defect centers CVD diamond”, Diamond and Related Materials vol. 9, no. 7

Open access
Association of the Apolipoprotein A-I gene polymorphisms with cardiovascular disease risk factors and atherogenic indices in patients from assam, Northeast India

Introduction Cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity worldwide. In 2012, an estimated 17.5 million people died of CVDs, representing about 31.0% of all global deaths [ 1 ]. Atherosclerosis, which refers to the progressive hardening of arteries and narrowing of lumen due to fibro-fatty changes in the vessel wall, is the major pathophysiological process underlying CVDs [ 2 ]. The risk factors for atherosclerosis and CVDs are many, such as altered serum lipid levels (also called dyslipidemia), smoking, alcohol, obesity

Open access
CVD diamond layers for electrochemistry

Abstract

Diamond electrodes of different morphologies and qualities were manufactured by hot filament chemical deposition (HF CVD) techniques by changing the parameters of diamond growth process. The estimation of diamond quality and identification of different carbon phases was performed by Raman spectroscopy measurements. The effect of diamond quality and amorphous carbon phase content on the electrochemical response of an obtained diamond electrode in 0.5 M H2SO4 as supporting electrolyte was investigated by cyclic voltammetry with [Fe(CN)6]4−/3− as a redox probe. The kinetic parameters such as catalytic reaction rate constant k0 and electron transfer coefficient α were determined. The obtained results show that the analytical performance of undoped diamond electrodes can be implemented just by the change of diamond layers quality.

Open access
Studies of field emission process influence on changes in CNT films with different CNT superficial density

Abstract

Field emission from materials at high electric fields can be associated with unfavorable or even destructive effect on the surface of the investigated cathode. The impact of high voltage electric power supply causes locally very strong electric fields focusing on the cathode surface. It causes a number of phenomena, which can adversely affect the morphology and the structure of the cathode material. Such a phenomenon is, for example, peeling of an emissive layer from the substrate or its burnout. It results in tearing of the layer and a decrease or loss of its ability to electrons emission. The cold cathodes in a form of CNT films with various CNTs superficial distribution are obtained by physical vapor deposition followed by chemical vapor deposition. CNTs are catalyzed in pyrolytic process with xylene (CVD), by Ni in a form of nanograins (few nm in size) placed in carbonaceous matrix. These films are built of emissive CNTs - carbonaceous film deposited on different substrates. In this work, the morphology and topography of superficial changes resulting from external electric field in such films were investigated.

Open access
Chemically vapor deposited diamond films as dosimetric material for potential clinical applications

Abstract

Thermally stimulated luminescence (TL), cathodoluminescence (CL) and Raman spectroscopy of CVD diamond films grown on silicon substrates have been studied in order to obtain information on defects created during the growth, which induce the levels within the gap. TL between 300 K and 700 K, and CL from 200 nm to 1200 nm have been teasured. The glow curves show a peak located around 610 K with different intensities, depending on the sample thickness, associated with a trap of energy, equal to 0.83 eV and with attempt-to-escape-time of the order of 108 s-1. Broad CL bands observed at 428±1 nm (2.90 ±0.01 eV) and 500±1 nm (2.47±0.004 eV) are attributed to closely spaced and widely separated donor-acceptor (D-A) pairs, respectively. The TL and CL results were correlated with diamond quality estimated from Raman spectroscopy measurements.

Open access
CVD synthesis of graphene nanoplates on MgO support

Abstract

Synthesis of graphene directly on MgO has been carried out and the structural properties of the obtained material have been investigated. Few-layered graphene was produced by simple thermal decomposition of methane over MgO powder at 950 °C in a CVD reactor. The samples were purified by 10 N HNO3 treatment, and studied by TEM, Raman spectroscopy, EDAX and SEM. TEM clearly indicated the formation of graphene. EDAX showed that the purified sample contained only carbon and no traces of MgO. The characteristic Raman features of graphene were also seen as D-band at 1316 cm−1, G-band at 1602 cm−1, and a small 2D-band at 2700 cm−1 in the Raman spectra. The strong D-band suggests that the graphene possess large number of boundary defects. The small 2D-band indicates the formation of few-layered graphene.

Open access
Electron emission from nitrogen-doped polycrystalline diamond/Si heterostructures

Abstract

The field electron emission from polycrystalline diamond/silicon and nitrogen-doped polycrystalline diamond/silicon structures obtained by HF CVD deposition method has been investigated. Electron emission currents from the samples were measured in a chamber at the pressure equal to 2·10−6 Pa in sphere-to-plane diode configuration with the 5 μm distance between electrodes. As expected, the results confirm the relation between the structure of diamond films and their emission properties. The type of silicon substrate also influences the value of emission currents and the diamond/n-Si heterostructures exhibit better electron emission than diamond/p-Si ones. The nitrogen doping significantly enhances the electron emission from the heterostructures and their emission parameters. The values of the threshold field between 2 V/μm and 3 V/μm were registered, the values of emission current close to 1 mA/cm2 at 5 V/μm for the nitrogen-doped films were obtained. The shape of current-voltage characteristics for nitrogen-doped polycrystalline films may be interpreted in terms of stochastic distribution of diameters of conducting channels which form the emission centers.

Open access
Graphene growth by transfer-free chemical vapour deposition on a cobalt layer

. 8, no. 2, 2009, pp. 135-138. [4] M. Othman, R. Ritikos, S. M. Hafiz, N. Khanis, N. A. Rashid and S. A. Rahman, ”Low-Temperature Plasma-Enhanced Che- mical Vapour Deposition of Transfer-Free Graphene Thin Films” Materials Letters vol. 158, 2015, pp. 436-438. [5] T. Kato and R. Hatakeyama, ”Direct Growth of Doping -Den- sity-Controlled Hexagonal Graphene on SiO2 Substrate by Rapid-Heating Plasma CVD”, ASC Nano, vol. 6, no. 10, 2012, pp. 8508-8515. [6] T. H. Bointon, M. D. Barnes, S. Russo and M. F. Craciun, ”High

Open access