Papers by Keyword: Nb₂O₅

Abstract: The effect of small additions of niobium pentoxide (Nb₂O₅) from 0 to 0.7 wt% on the zirconia toughened alumina (ZTA) ceramics sintered at 1600 °C was studied. Based on the results, the small addition of Nb₂O₅ was discovered to be able to significantly influence on phase, microstructure, and mechanical properties of ZTA ceramics. The presence of the secondary phase of Nb₂Zr₆O₁₇ as a square-shaped particle is confirmed by SEM and FESEM-EDX up to 0.5 weight percent (wt.%) of Nb₂O₅ additions. The addition of 0.3 wt.% resulted in the highest Vickers hardness value of 1500 Vickers hardness (HV). However, it was found that adding Nb₂O₅ more than 0.3 wt% causes ZTA's hardness and indentation fracture resistance (K_IFR) values to decline from 1500 HV to 1438 HV and 4.88 MPa.√m to 4.18 MPa.√m, respectively. Additionally, it was found that when the amount of Nb₂O₅ added increased, the value for bulk density climbed while porosity reduced.

Abstract: The Y₃Al_5-xNb_xO₁₂ (0 ≤ x ≤ 0.06) garnet ceramics were prepared by solid-state reaction method. The effects of Nb⁵⁺ substitution on the phase composition, microstructure and microwave dielectric properties were investigated. All samples retained the yttrium-aluminum garnet solid solution form until x up to 0.06 at which YNbO₄ secondary phase precipitated. The doping of Nb₂O₅ improved the grain development and enhanced the physical properties of the ceramics under the sintering condition of 8 h at 1700 °C. Specifically, with the substitution of Nb⁵⁺, the degree of micromorphology improvement and quality factor first increased and then decreased, with a maximum value at x = 0.015. Finally, the best combination of microwave dielectric properties was obtained, i.e., ε_r = 10.79, Q×f = 165,478 GHz, τ_f = -31.7 ppm/°C. This study provides a theoretical basis for the further expansion and application of yttrium aluminum garnet in the microwave field. Keywords: Yttrium Aluminum Garnet ceramics, Nb₂O₅, microwave dielectric properties.

Abstract: Nb₂O₅ has recently been considered as one of the oxides thin films that attracts a noticeable attraction by scientific prospective aspects. Its usefulness in a wide practical applications range such as in optoelectronic devices, optical coatings, catalysis, gas sensors, photocell, electrochromics, photoelectrodes, Ec devices, microelectronics and in the medical field paid researchers attention to synthesize it by various methods like sol.gel, electrodeposition, chemical vapor deposition etc. Among those, Pulsed laser deposition technique has achieved an effective improvements. In this paper, we aim to revise increasing significance of Nb₂O₅ supported by previous applications and a further possible future outlook.

Abstract: It is estimated that 130 million people will suffer from osteoarthritis by 2050 which require patient to undergo a surgical procedure known as total hip replacement which has lifespan of 20 years and failure rates of ~1%. This research would highlight the effects of doping Niobium Oxide (Nb₂O₅) between 0 vol % to 0.8 vol % into Zirconia-Toughened Alumina (ZTA) composites which is the main biomaterials used to manufacture total hip arthroplasty. The samples were sintered using two-stage sintering (TSS) between 1400°C and 1550°C for first-stage sintering temperature at heating rate of 20°C/min. At second stage, the samples were sintered at 1350°C and hold for 12 hours. It was found that TSS combined with addition of Nb₂O₅ as dopants were beneficial in producing fine-grained ZTA composites with improved mechanical properties compared to undoped ZTA composites produced via TSS. Compared to undoped ZTA composites, samples doped with Nb₂O₅ and sintered at T₁ ≥1400°C were fully densed (>98%), achieved Vickers hardness more than 20 GPa and Young’s modulus higher than 410 GPa and at the same time fracture toughness of more than 8 MPam^1/2. Based on the findings, production of ZTA composites with enhanced mechanical properties with longer lifespan is possible which is beneficial in ensuring the well-being of osteoarthritis patients.

Abstract: In this work, the Nb₂O₅ nanostructure has been deposited using Q-switched Nd: YAG laser in the vacuum pressure of 0 bar pressure on quartz substrates. Physical properties of the prepared films at different substrate temperatures (300, 400, and 500) °C were characterized. The obtained results reflect the formation of good quality monoclinic Nb2O5 thin film. A clear blow shift was also obtained where the optical band gap increase from (to) with temperature. Finally, AFM results revealed the increase the surface roughness with substrate temperatures.

Abstract: Conventionally, palm oil mill effluent (POME) was treated using open ponding system, which nevertheless long retention times and large treatment areas were required. In this report, heterogeneous photocatalysis was used to degrade the POME and simultaneously assessed the biogas formation. Characterization of the chemically prepared hierarchical porous ZnO microspheres showed that wurtzite was the predominant crystalline phase with a band gap energy of 3.22 eV. Moreover, the as-prepared ZnO were assembled by large numbers of interleaving nanosheets and formed an open porous structure. Under UV irradiation, the as-prepared ZnO demonstrated photocatalytic property on POME degradation. The WO₃ and Nb₂O₅ decorated ZnO photocatalysts (WO₃/ZnO and Nb₂O₅/ZnO) with improved photocatalytic performances were also prepared using a simple and rapid way. Significantly, in the presence of WO₃/ZnO and Nb₂O₅/ZnO composites, the degradation of POME achieved 68.3% and 91.7%, respectively after 240 min irradiation. Interestingly, the assessment of the biogas formation showed that the photocatalytic reactions over Nb₂O₅/ZnO and WO₃/ZnO composites generated higher amount of biogas products (CH₄ + CO₂) compared to that of ZnO. The photocatalytic enhancement was attributed to the high separation efficiency of photogenerated electron–hole pairs based on the formation of heterojunction structures between the WO₃/Nb₂O₅ and ZnO. The observed findings also revealed that the photocatalytic technology using hierarchical WO₃/ZnO and Nb₂O₅/ZnO composites had the potential to efficiently treat wastewater.

Abstract: The aims of this research is to identify the effect of Nb₂O₅ addition on the electrical properties of Fe₂TiO₅ ceramics-based NTC thermistor.The concentration of Fe₂O₃ and TiO₂ was proportional to Fe₂TiO₅, whereas the concentration value of Nb₂O₅ were 0, 0.5 and 1.0 mole %, respectively. Within two hours, the mixed powder was pressed at 4 ton/cm² to form pellets and sintered at 1300 °C in air. It can perceived from the XRD data that the sintered ceramics had single phase of Fe₂TiO₅, pseudobrookite. From SEM data, it is found that addition of Nb₂O₅ decreases the grain size. The addition of Nb₂O₅ increases thermistor constant, activation energy and electrical resistance of Fe₂TiO₅ ceramics. The values of thermistor constant of Nb₂O₅ added-Fe₂TiO₅ ceramics were relatively large, indicated that the ceramics were aplicable as the NTC thermistor.

Abstract: The mechanical properties and creep resistance of the Al₂O₃ have been improved with the use of other oxide ceramics, among these the Y₃Al₅O₁₂ (YAG - "yttrium aluminum garnet"), to obtain the Al₂O₃-YAG composite. The aim of this work is to study the effect of addition of Nb₂O₅ at low sintering temperatures of the composite, starting from the eutectic composition Al₂O₃-Y₂O₃. In this work, the compositions were produced by powder mixtures of Al₂O₃-Y₂O₃ and Al₂O₃-Y₂O₃-Nb₂O₅ using high energy ball milling. The green bodies were pressed at 70 MPa and sintered at 1000, 1100, 1200 and 1300°C for 2 h. The materials were characterized by shrinkage and X-Ray Diffraction (XRD) using the Rietveld method. The presence of Nb₂O₅ does not show any improve neither for the YAG phase formation nor for the shrinkage of the sintered samples in the temperature range studied.

Abstract: The influence of Nb2O5 and La2O3 on the phase and microstructure evaluation and mechanical properties of composite ceramics sintered with 2.45 GHz microwave energy was investigated. The results showed that Nb2O5 could densify the pure alumina with a lower sintering temperature and a short sintering time. Nb2O5 reacted with Al2O3 to form AlNbO4 completely and the amount of AlNbO4 increased with the increasing content of Nb2O5, distributing at the Al2O3 grain boundaries. The specimen doped with 10 Vol.% Nb2O5 sintered at 1500 °C exhibited plenty of columnar grains with draw ratio about 1:3. La2O3 reacted with Al2O3 to form LaAl11O18 completely, the specimen doped with 10 Vol.% and 15 Vol.% La2O3 sintered at 1500 °C exhibited plenty of columnar grains with draw ratio about 1:4. The existence of columnar grains enhanced the microhardness and fracture toughness of composite ceramics.

Abstract: An approach for making functional films of polymer – nanocomposites under the framework of nanotechnology is presented. In this methodology, nanowires of an inorganic functional material are dispersed in a functional polymeric medium and the resultant solution is developed into solid films by electrospinning technique. The final structure is a nanofibrous film – each nanofiber contains a percolating network of inorganic nanowires. The nanowires reduce the percolation threshold compared to those nanoparticles and maintain the flexibility and/or light weight of the polymers and nanomaterials. This methodology has been tested for a number of material architectures for electronic and energy devices.