| 1. |
- Mukerji, Joydeb, et al.
(författare)
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Wear of Nitrogen Ceramics and Composites in contact with Bearing Steel under Oscillating Sliding Conditions
- 1998
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Ingår i: Ceramics International. - 0272-8842 .- 1873-3956. ; 24:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- The wear of nitrogen based ceramics in contact with bearing steel balls (SAE 52100) was investigated under reciprocating sliding conditions at a velocity of 0.1 m/s, and 20 N, 40 N and 100 N load. Three types of ceramics were studied: viz. hot pressed silicon nitride (HPSN) sintered with selected liquid in the system yttria-aluminium nitride-silica and composites of HPSN with BN and TiC; SiAlON formulated with different amounts of alumina and silica; and aluminatitanium nitride composite having 60 mol% TiN. Among the HPSN composites, HPSN 15vol% TiC had the lowest average wear factor (K) of 2.0 × 10- 5mm3/m/ N. The SiAlONs, in general, had the highest K and this increased with increasing O concentration. The lowest K value for SiAlON ceramic was 6.9 × 10-5mm3/m/N. The high K value of SiAlON is attributed to O substitution, which promotes adhesive wear resulting in mutual material transfer. The lowest wear of all the ceramics tested was found for the alumina-titanium nitride composite, the wear factor being of the order of 4.4 × 10-7mm3/m/N, which is one order of magnitude lower than the other nitrogen ceramics. In the case of HPSN and alumina-titanium nitride composites, abrasive wear and wear due to microfracture were the main wear mechanisms. Wear of the steel ball was lowest when in contact with HPSN---TiC composites, being almost equal to that of the ceramic, whereas the alumina-titanium nitride composite wore away the steel almost 20 times faster than the ceramic and will thus be unsuitable as a counterface material for 52100 steel.
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| 2. |
- Afroze, Shammya, 1987, et al.
(författare)
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Structure-conductivity relationship of PrBaMnMoO 6-δ through in-situ measurements: A neutron diffraction study
- 2021
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 47:1, s. 541-546
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Tidskriftsartikel (refereegranskat)abstract
- The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm−1 at 700 °C.
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| 3. |
- Aleni, Afshin H., et al.
(författare)
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3D printing of dense and porous TiO2 structures
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 46:10, s. 16725-16732
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Tidskriftsartikel (refereegranskat)abstract
- Direct foam writing allows the fabrication of highly porous and hierarchical ceramic structures with high specific mechanical properties. This manufacturing technique, however, has mainly used stabilized Al2O3 foam inks. In this work, we pressent a novel foam ink based on TiO2. This ink uses polyvinyl alcohol (PVA) as a binder and a small amount of zinc as a frothing agent. We used this ink to produce cylindrical foam samples via direct foam writing. The foams had a porosity of up to 65% and a mean pore size of 180 μm, which is significantly larger than previously reported for direct foam writing with Al2O3. The foams were tested in compression and were found to have an elastic modulus of 0.5 GPa and a compressive strength of 12–18 MPa. These mechanical properties are similar to those of porous ceramics produced by conventional manufacturing routes. Therefore, this work represents a step forward by broadening the direct foam writing process to a wider range of porous ceramics.
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| 4. |
- Ali, Amjad, et al.
(författare)
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A potential electrolyte (Ce1-x CaxO2-delta) for fuel cells:Theoretical andexperimental study
- 2018
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 44:11, s. 12676-12683
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations are performed using density function theory to explore the effects of dopant Ca in ceria (Ce1-x CaxO2-delta). The impact of oxygen vacancy on band gap and density of states is examined in doped ceria using generalized gradient approximations. Vacancy association and vacancy formation energies of the doped ceria are calculated to reveal the effect of dopant on ion conduction. The experimental study of the sample Ce0.875Ca0.125O2-delta) was performed to compare with the theoretical results. The obtained results from theoretical calculation and experimental techniques show that oxygen vacancy increases the volume, lattice constant (5.47315 angstrom) but decrease the band gap (1.72 eV) and bulk modulus. The dopant radius (1.173 angstrom) and lattice constant (5.4718 angstrom) are also calculated by equations which is close to the DFT lattice parameter. The result shows that oxygen vacancy shifts the density of states to lower energy region. Band gap is decreased due to shifting of valence states to conduction band. Vacancy formation shows a significance increase in density of states near the Fermi level. Density of states at Fermi level is proportional to the conductivity, so an increase in density of states near the Fermi level increases the conductivity. The experimental measured ionic conductivity is found to 0.095 S cm(-1) at 600 degrees C. The microstructural studies is also reported in this work.
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| 5. |
- Ali, Sharafat, 1976-, et al.
(författare)
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Issues associated with the development of transparent oxynitride glasses
- 2015
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 41:3, s. 3345-3354
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Tidskriftsartikel (refereegranskat)abstract
- Oxynitride glasses and glass ceramics are increasingly recognized as potential materials in specialist applications in modern industrial sectors. Oxynitride glasses have superior mechanical, rheological and optical properties to their oxide glass counterparts. Properties of these glasses can be tailored by changes in nitrogen content and additions of various alkaline-earth and or rare-earth elements. In contrast to oxide glasses, oxynitride glasses are difficult to prepare which adds to production costs. Furthermore, they contain impurities in the form of elemental silicon and silicides, have poor oxidation resistance in air above their glass transition temperatures and have poor transparency in the visible region. This article reviews the above issues in relation to the potential applications of these glasses.
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| 6. |
- Alsalmah, Hessa A., et al.
(författare)
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Developing polymer nanocomposite films of ZnO/NiFe2O4 nanohybrids, polyvinyl pyrrolidone, and chitosan for flexible electromagnetic
- 2024
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 50:16, s. 28794-28804
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Tidskriftsartikel (refereegranskat)abstract
- The present study used ultra-sonication approach to manufacture ZnO/NiFe2O4 (ZNF) and casting technique to prepare ZnO/NiFe2O4-Cs/PVP nanocomposite films. The successful creation of these nanocomposites with a significant decrease in the % crystallinity of the polymer blend with doping agent was verified by XRD results. ZNF and the Cs/PVP chains interacted in the polymer nanocomposites, as seen by the spectra of the FTIR. To determine the direct and indirect optical band gaps, tauc graphs were studied using data from UV-Vis analysis. The results indicate that while the Urbach energy was found to increase, the optical band gaps decreased as the weight percentage of the nanofiller increased. Using a thermogravimetric approach, the thermal stability of the produced PNCs has been investigated. Conductivity experiments demonstrated that when the nanofiller ZNF content increased to 2.5 wt%, so did AC conductivity, the dielectric loss, and the dielectric constant. The correlation between the mechanism of conduction and the amount of nanoparticles indicates that an increase in the percentage of ZNF in nanocomposites could increase their conductivity, with values ranging from 3.72 x 10-12 for pure blend to 7.72 x 10-8 S/cm for 2.5%ZNF-Cs/PVP at 100 Hz. The dielectric measurements for the nanocomposite films showed an increase in dielectric losses and dielectric constant, which is indicative of the films' enhanced dielectric polarization. The results of characterization point to possible uses of these polymer nanocomposites in flexible optoelectronic and magneto-electronic applications and energy storage devices.
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| 7. |
- Alsalmah, Hessa A., et al.
(författare)
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Optical, conductivity, dielectric, and magnetic properties of polymer nanocomposite based on PAM/cs matrix and ZnFe2O4 NPs for use in magneto-electronic and energy storage capacitor devices
- 2024
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 50:7, s. 12167-12174
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a cast synthesis approach was used to create flexible nanocomposite films made of polyacrylamide (PAM), chitosan (Cs), and zinc ferrite nanoparticles (ZnFe2O4 NPs). XRD analysis was used to examine the composite structure. They demonstrated the effective interaction between ZnFe2O4 NPs and PAM/Cs blend. As the concentration of nanomaterial in the host polymer matrix grew, it was observed that the PAM/Cs matrix's direct and indirect energy band gaps decreased while its absorbance of ultraviolet-visible radiations increased. The nanocomposite's AC conductivity was significantly higher than that of the blend, and 2.5 wt percent of the nanocomposite showed the highest electrical conductivity. It was observed that as frequency raised, the epsilon ' and epsilon '' declined though the concentration of nanoparticles enhanced these characteristics. Because of the high dielectric permittivity of ZnFe2O4, the values of epsilon ' and epsilon '' raised as ZnFe2O4 were higher. The outcome of the vibrating sample magnetometer (VSM) demonstrated the ferromagnetic property of the produced nanocomposites. Furthermore, the VSM study shows that as the nanoparticles content increases, the PAM/Cs/ZnFe2O4 nanocomposites' Ms, Hc, and Mr also increase. These PAM/Cs/ZnFe2O4 films were shown by the experimental results to be promising candidates for bandgap-regulated materials, electromagnetic interference shielders, frequency tunable nanodielectric, and flexible dielectric substrates for future microelectronic, optoelectronic technologies, and capacitive energy storage.
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| 8. |
- Antti, Marta-Lena, et al.
(författare)
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Phase reactions in a hot pressed TiC/Si powder mixture
- 2012
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 38:3, s. 1999-2003
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Tidskriftsartikel (refereegranskat)abstract
- This work investigated the possibility of producing dense Ti3SiC2 by hot pressing TiC/Si powders. A hot press with graphite heating elements was used for densification and the phase reactions of some hot pressed samples were further evaluated by pressureless heating in a dilatometer. The density and phase composition of the heat treated samples were evaluated using Archimedes principle and by x-ray diffractometry respectively. Hot pressing resulted in a low Ti3SiC2 yield; the main phases were TiC and TiSi2 regardless of starting powder composition, temperature, holding time or pressure. A second heating without pressure resulted in Ti3SiC2 formation, but only in samples initially hot pressed at 1300 °C or lower. At higher hot pressing temperatures, thin oxide layers on particle surfaces were locked into the structure. Acting as diffusion barriers, they prevented the Ti3SiC2 forming reaction. In hot pressed samples the density was significantly higher than in samples sintered without pressure.
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| 9. |
- Archana, M. S., et al.
(författare)
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Influence of applied pressure during field-assisted sintering of Ti(C,N)-WC-FeAl based nanocomposite
- 2015
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Ingår i: Ceramics International. - 0272-8842 .- 1873-3956. ; 41:2, s. 1986-1993
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Tidskriftsartikel (refereegranskat)abstract
- Ti(C,N)-WC-FeAl based nanocomposites are processed by field-assisted sintering at 1500 degrees C. The phase and microstructural evolution during the process under the influence of different applied pressures of 30, 50 and 100 MPa are studied using x-ray diffraction and scanning electron microscopy. Lattice parameters of (Ti,W)(C,N) solid solution and binder phases after sintering are found to vary with applied pressure. The nanocomposite grains are observed to possess a core-rim microstructure. Microstructural variations in terms of type, size and fraction of "corerim" structure as a function of applied pressure are investigated. The hardness and indentation fracture toughness values are in the range of 17.6-18.4 GPa and 5.9-6.8 MPa root m, respectively. These values are comparable with those reported for Ti(C,N)-based composites with metal binder. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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| 10. |
- Barick, P., et al.
(författare)
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Effect of concentration and molecular weight of polyethylenimine on zeta potential, isoelectric point of nanocrystalline silicon carbide in aqueous and ethanol medium
- 2015
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Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 41:3, s. 4289-4293
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Tidskriftsartikel (refereegranskat)abstract
- The effect of dispersant concentration and its molecular weight on zeta potential of nanocrystalline silicon carbide in an aqueous medium was investigated. An increase in the concentration of the dispersant, such as polyethylenimine (PEI), in slurry prepared from nanosized silicon carbide, was found to augment the iso-electric point and zeta potential. However, the zeta potential was observed to decline as the pH of the slurry shifts towards the basic region. This aforementioned behavior is attributed to the enhanced mutual repulsion between the polymer chains of the dispersant adsorbed on the surfaces of SiC particles and those approaching the surfaces. The higher ionization potential of polymers in the acidic region compared to the basic region increases the adsorption. The relationship between zeta potential and pH is however, noted to remain virtually unchanged with molecular weight of PEI. Further, it is observed that zeta potential of SiC decreases with the increase in solid content of the slurry. Rheology study reveals that the ethanol based slurry has a lower viscosity than the water based slurry, making ethanol the preferred dispersing medium for colloidal processing of nanometric SiC powder. © 2014 Elsevier Ltd and Techna Group S.r.l.
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