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Composite Ceramics Based on Nanostructured Refractory Oxide Whiskers
Tatyana Mikhailovna Ulyanova,
Petr Alexandrovich Vitiaz,
Nikolai Pavlovich Krutko,
Luydmila Vasil’evna Ovseenko,
Alexandr Arkad’evich Shevchenok,
Luydmila Viktorovna Titova,
Alexis Romanovich Luchenok
Issue:
Volume 3, Issue 5, October 2014
Pages:
33-37
Received:
14 June 2014
Accepted:
3 July 2014
Published:
10 October 2014
Abstract: In the present work the influences of thermal-baric effect in the process of nanostructured alumina and zirconia powders consolidation on structure and physical-mechanical properties of the composite ceramics have been investigated. The samples of ceramics have been prepared from nanostructured powders (ZrO2 -3 mol. % Y2O3) and Al2O3 in ratio from 100 : 0 to 20 : 80 wt. % in two ways: by static uniaxial pressing and by pulse pressing. Then part blanks were annealed in the temperature region 1560-1670 oC. During pulse process a crystal structure of samples was disordered, and monoclinic ZrO2 lattice was partially deformed. After a heat treatment of a blank the crystal structure of metal oxides was restored. Ceramics of oxide powders with content 100 - 50 wt. % PSZ synthesized at the 1100 oС possessed a higher level of properties than one of active powders prepared at the 900 oC.
Abstract: In the present work the influences of thermal-baric effect in the process of nanostructured alumina and zirconia powders consolidation on structure and physical-mechanical properties of the composite ceramics have been investigated. The samples of ceramics have been prepared from nanostructured powders (ZrO2 -3 mol. % Y2O3) and Al2O3 in ratio from ...
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Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor
Patrick Mwinzi Mwathe,
Robinson Musembi,
Mathew Munji,
Benjamin Odari,
Lawrence Munguti,
Alex Alfred Ntilakigwa,
Julius Mwabora,
Walter Njoroge,
Bernard Aduda,
Boniface Muthoka
Issue:
Volume 3, Issue 5, October 2014
Pages:
38-44
Received:
12 September 2014
Accepted:
27 September 2014
Published:
10 October 2014
Abstract: Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO2 and 3.8014eV for F:SnO2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO2 thin film for Pd:SnO2 while for F:SnO2 has been due to incorporation of F- ions in the crystal lattice of SnO2 which gives rise to donor levels in the SnO2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value. The electrical resistivity was done by measuring the sheet resistance of the SnO2, Pd:SnO2, F:SnO2 and Pd-F:SnO2 thin films. The undoped SnO2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO2 results from substitution incorporation of F- ions in the crystal lattice of SnO2 thin films, instead of O- ions which lead to an increase in free carrier concentration. The Pd-F:SnO2 gas sensor device was tested for CO2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth. This causes a decrement in adsorption properties of CO- and O- species by the annealed Pd-F: SnO2 thin film. The sensitivity of passivated Pd-F: SnO2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO2 thin film was found to be within the range for gas sensing applications.
Abstract: Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples...
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Experimental Investigation on the Effect of Multiwalled Carbon Nanotubes and Nano-SiO2 Addition on Mechanical Properties of Hardened Cement Paste
Anand Hunashyal,
Nagaraj Banapurmath,
Akshay Jain,
Sayed Quadri,
Ashok Shettar
Issue:
Volume 3, Issue 5, October 2014
Pages:
45-51
Received:
5 September 2014
Accepted:
16 September 2014
Published:
30 October 2014
Abstract: This paper investigates the behaviour of hardened cement paste reinforced with multi-walled carbon nano-tubes (MWCNTs) and Nano-SiO2 (NS). In these composites, the percentage of MWCNTs was fixed at 0.75% by weight of cement, while the percentage of NS was fixed at 0.5% by weight of cement. Dispersion of both MWCNTs and NS was carried out using ultrasonic energy method. The novel nano-composite specimens developed were tested for compression and flexure in order to evaluate their mechanical properties such as compressive strength, flexural strength, toughness and ductility. These results were then compared with the results of plain cement control beams. Scanning electron microscopy was conducted to examine the bond between the MWCNTs and the cement matrix.
Abstract: This paper investigates the behaviour of hardened cement paste reinforced with multi-walled carbon nano-tubes (MWCNTs) and Nano-SiO2 (NS). In these composites, the percentage of MWCNTs was fixed at 0.75% by weight of cement, while the percentage of NS was fixed at 0.5% by weight of cement. Dispersion of both MWCNTs and NS was carried out using ultr...
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Synthesis and Characterization of Cobalt Oxide and Composite Thin Films
Ulrika Lagerqvist,
Mikael Ottosson,
Annika Pohl
Issue:
Volume 3, Issue 5, October 2014
Pages:
52-57
Received:
18 February 2014
Accepted:
13 October 2014
Published:
10 November 2014
Abstract: Cobalt oxide and composite thin films were synthesized by spin-coating technique, followed by heating to 500°C in oxidizing, inert, or reducing atmospheres. Methanolic solutions of triethanolamine complexes of cobalt acetates and nitrates were spin-coated at 1000, 2000, and 3000 rpm. The influence of heating parameters and film thickness on the phase content of the films were investigated, using grazing incidence X-ray diffraction, X-ray reflectivity, and scanning electron microscopy. By tuning the synthesis parameters, Co3O4, CoO and Co films were obtained, as well as CoO–Co and Co3O4–CoO composite films of varying phase ratios.
Abstract: Cobalt oxide and composite thin films were synthesized by spin-coating technique, followed by heating to 500°C in oxidizing, inert, or reducing atmospheres. Methanolic solutions of triethanolamine complexes of cobalt acetates and nitrates were spin-coated at 1000, 2000, and 3000 rpm. The influence of heating parameters and film thickness on the pha...
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Improvement of the Properties of Aluminium Alloys
Korostelev V. F.,
Bolshakov A. E.
Issue:
Volume 3, Issue 5, October 2014
Pages:
58-62
Received:
22 August 2014
Accepted:
24 November 2014
Published:
27 November 2014
Abstract: The article describes the improvement of the properties of aluminium alloys under pressure application of up to 400 MPa to a liquid or crystallizing metal. A cybernetic model has been developed. Three phases of the alloy compressibility under pressure were investigated. The results of microstructure studies are indicated, the focus has been made on the non-uniform composition within the limits of dendritic cells. Pressure influence on the formation of crystallization centers and their growth was demonstrated. The relationship between hardness and the content of separate alloy components and of the applied pressure was illustrated.
Abstract: The article describes the improvement of the properties of aluminium alloys under pressure application of up to 400 MPa to a liquid or crystallizing metal. A cybernetic model has been developed. Three phases of the alloy compressibility under pressure were investigated. The results of microstructure studies are indicated, the focus has been made on...
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