Pulsed laser deposition of KNbO₃ thin films

The laser ablation of stationary KNbO3 single crystal targets induces a Nb enrichment of the target surface. In rotated targets this effect is observed only in those areas irradiated with low laser fluence. The composition of the plasma formed close to the target surface is congruent with the target composition; however, at further distances K-deficient films are formed due to the preferential backscattering of K in the plasma. This loss may be compensated for by using K-rich ceramic targets. Best results so far have been obtained with [K]/[Nb] = 2.85 target composition, and crystalline KNbO3 films are formed when heating the substrates to 650 °C. Films formed on (100)MgO single crystals are usually single phase and oriented with the (110) film plane parallel to the (100) substrate surface. (100)NbO may coexist with KNbO3 on (100)MgO. At substrate temperatures higher than 650 °C, niobium diffuses into MgO forming Mg4Nb2O9 and NbO, leading to K evaporation from the film. Films formed on (001) alpha-Al2O3 (sapphire) show the coexistence of (111), (110), and (001) orientations of KNbO3, and the presence of NbO2 is also observed. KNbO3 films deposited on (001)LiNbO3 crystallize with the (111) plane of the film parallel to the substrate surface. For the latter two substrates the Nb diffusion into the substrate is lower than in MgO and consequently the K concentration retained in the film is comparatively larger

Growth of laser host thin-film optical waveguides by pulsed laser deposition

Optical waveguides of laser gain media are highly desirable because the high intensity-length product and good pump-signal mode overlap, which can be achieved in the waveguide geometry, leads to a reduced threshold pump power as compared to bulk lasers. Pulsed laser deposition (PLD) has emerged as a viable means of depositing epitaxial thin films of the correct composition. We report here the deposition of GGG and YGG thin films on YAG substrates and the deposition of sapphire on sapphire substrates

Exergy analysis of vapor compression refrigeration system using R450A as a replacement of R134a

This paper experimentally investigated exergetic performance analysis of vapor compression refrigeration system using R450a as a replacement for R134a at different evaporator and condenser temperatures within controlled environmental conditions. The exergetic performance analysis of the vapor compression refrigeration system with test parameters including efficiency defects in the components, total irreversibility, and exergy efficiency of the refrigeration system was performed. Findings showed that the total irreversibility and exergy efficiency of the vapor compression refrigeration system using R450A refrigerant were lower and higher than R134a by about 15.25–27.32% and 10.07–130.93%, respectively. However, the efficiency defect in the condenser, compressor, and evaporator of the R450A refrigeration system was lower than R134a by about 16.99–26.08%, 5.03–20.11%, and 1.85– 15.85%, respectively. Conversely, efficiency defect in the capillary tube of the R450A refrigeration system was higher than R134a by about 14.66–78.97% under similar operating conditions. Overall, it was found that the most efficient component was the evaporator, and the least efficient component was the compressor for both refrigerants

Component-wise exergy analysis using adaptive neuro-fuzzy inference system in vapor compression refrigeration system

In this work, the adaptive neuro-fuzzy inference (ANFIS) system as an artificial intelligence method was used to predict the destruction of exergy in components (compressor, condenser, capillary tube and evaporator) of a vapor compression refrigeration system using a mixture of R134a and LPG refrigerant (consisting of R134a and LPG in a ratio of 28:72 by mass fraction). For this purpose, ANFIS models were developed to predict the destruction of exergy in each component using some experimental data recently published in author previous publication, and the remaining data were used to validate the developed models. It was found that the predictions of ANFIS models are in good agreement with the experimental results and give an absolute fraction of variance in range of 0.996–0.999, a root mean square error in range of 0.0296–0.1726 W and mean absolute percentage error in range of 0.108– 0.176%, respectively. The results suggest that the ANFIS models can predict the destruction of exergy in the components of refrigeration system quickly and with high accuracy

Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3

We have fabricated NbSe$_3$ structures with widths comparable to the Fukuyama-Lee-Rice phase-coherence length. For samples already in the 2-dimensional pinning limit, we observe a crossover from 2-dimensional to 1-dimensional collective pinning when the crystal width is less than 1.6 $\mu$m, corresponding to the phase-coherence length in this direction. Our results show that surface pinning is negligible in our samples, and provide a means to probe the dynamics of single domains giving access to a new regime in charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical Review

Laser operation of an Nd:Gd₃Ga₅O₁₂ thin-film optical waveguide fabricated by pulsed laser deposition

We report the laser operation of a thin-film waveguide structure grown by the pulsed laser deposition technique. A 2.7-µm-thick crystalline film of neodymium doped Gd3Ga5O12 (Nd:GGG) lases at a wavelength centered at 1.06µm when pumped by a Ti:sapphire laser at 808 nm

Synthesis of biomedical Ti-25Ni-15Si-10HA alloy by mechanical alloying and spark plasma sintering

In this research approach, a β-phase titanium alloy was produced successfully employing mechanical alloying and consolidated with spark plasma sintering (SPS) process. Herein, Ni, Si and HA powders with varied weight percentage were used to fabricate the Ti alloy. The influence of HA addition on microstructure of the alloy was assessed using optical microscopy route and further amplified using field emission scanning electron microscopy (FESEM). The elemental composition and phase of Ti-alloy was investigated using x-ray diffractometer. Vicker hardness (HV) tester was employed to estimate the micro hardness of the specimen surface. During the FESEM analysis, it was observed that within the sintering process, alloy exhibits complex reactions with HA, which leads to the progress of bioactive compounds (CaO, TiO2, Ca3 (PO4)2, Ti2Ni, CaTiO3 and CaTiSiO5) enhancing the bioactivity of the Ti alloy. The fabricated Ti alloy (Ti-25Ni-15Si-10HA) exhibited superior microhardness (~458HV) at 900°C, comparative to the other alloys of the native category. Based upon the current investigation, Ti-25Ni-15Si-10HA alloy could find applications as bioimplants in dental and orthopedic areas

Synthesis of biomedical Ti-25Ni-15Si-10HA alloy by mechanical alloying and spark plasma sintering

In this research approach, a β-phase titanium alloy was produced successfully employing mechanical alloying and consolidated with spark plasma sintering (SPS) process. Herein, Ni, Si and HA powders with varied weight percentage were used to fabricate the Ti alloy. The influence of HA addition on microstructure of the alloy was assessed using optical microscopy route and further amplified using field emission scanning electron microscopy (FESEM). The elemental composition and phase of Ti-alloy was investigated using x-ray diffractometer. Vicker hardness (HV) tester was employed to estimate the micro hardness of the specimen surface. During the FESEM analysis, it was observed that within the sintering process, alloy exhibits complex reactions with HA, which leads to the progress of bioactive compounds (CaO, TiO2, Ca3 (PO4)2, Ti2Ni, CaTiO3 and CaTiSiO5) enhancing the bioactivity of the Ti alloy. The fabricated Ti alloy (Ti-25Ni-15Si-10HA) exhibited superior microhardness (~458HV) at 900°C, comparative to the other alloys of the native category. Based upon the current investigation, Ti-25Ni-15Si-10HA alloy could find applications as bioimplants in dental and orthopedic areas

Performance of an Iso-Butane Driven Domestic refrigerator infused with various concentrations of Graphene based Nanolubricants

0.2, 0.4 and 0.6 g/L) of graphene based nanolubricants and selected mass charges (40, 50, 60 and 70g) of R600a refrigerant was studied. The steady state energetic performance of the domestic refrigerator was evaluated with test parameters including cabinet temperature, compressor power consumption, power per ton of refrigeration (PPTR) and coefficient of performance (COP). Findings showed that the lowest compressor power consumption and cabinet temperature observed within the system were 65 W and -12oC when infused with either 40g and 0 g/L or 60g and 0.2 g/L nanofluid mixtures. In addition, the utilization of 60 g and 0.2 g/L mixtures gave the highest PPTR value of 5.22 while the maximum COP value of 0.76 was seen with 70 g and 0 g/L respectively. In conclusion, the application of graphene based nanolubricants within the system significantly improved the performance

Experimental Performance of a Domestic Refrigerator with TiO2-Nanoparticles Operating Within Selected Ambient Temperature

This study presents a 40g R600a charge enhanced with various TiO2 nano-lubricant concentrations (0 g/L and 0.2 g/L nano-lubricants) infused into an R12 domestic refrigerator tested within selected ambient temperature conditions (19, 22 and 25 ºC). The performance test parameters including: energy consumption, discharge pressure, power per tonne of refrigeration (PPTR) and coefficient of performance (COP) were evaluated for the system. The results showed that infusing the nanolubricant into the system improved the energetic performance of the system. Overall, the use of 40g at 25ºC gave the best performance within the system. In conclusion, application of nanoparticles in refrigeration systems was found to improve the performances of the system even with the effect of ambient temperature. R600a-TiO2 nano-lubricant mixture works safely and efficiently in the domestic refrigerators but requires adequate optimization