Red emitting Mn4+ doped oxides are a promising class of materials to improve the colour rendering and luminous efficacy of phosphor-converted light-emitting diodes (pcLEDs). For pcLEDs, the optical properties are crucial w.r.t commercial acceptance. In this work, luminescence spectra and decay curves of Sr2YNbO6, Sr2YTaO6 and Sr2LaNbO6 have been recorded, other Mn4+ doped phosphors show that quenching occurs through thermally activated crossover between the 4T2 excited state and 4A2 ground state. The quenching temperature can be optimized by designing the host lattice in which Mn4+ has a high 4T2 state energy. The main target is to study the influence of the above-mentioned host materials on the emission spectra, PL quenching, and quantum yield of the deep red Mn4+ ion. The present study provides detailed insights into temperature and concentration quenching of Mn4+ emission and can be used to realize superior narrow-band red Mn4+ phosphors for horticultural lighting.
Organic acid doped polyaniline (PANI), hybrid with silica gel (SiG) and composites with metal primer have been prepared by chemical oxidative polymerization of double-distilled aniline in an acidic medium at 0-5 °C in an ice bath using ammonium persulphate as oxidant and p-toluene sulphonic acid (p-TSA) as the dopant. The anticorrosive property of PANI coatings containing alkyd primer, zinc chromate and silica gel was investigated. The coatings were characterized by FTIR spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy. The corrosion studies were carried out in a 3.5 wt% NaCl solution. On introduction of SiG, PANI, and PANI-SiG hybrid, the corrosion current decreased from 0.03626 μA to 0.007856 μA, 0.02042 μA, and 0.011 μA, respectively. The penetration rates calculated in mm/yr. for the composites: SiG/Primer, PANI/Primer and PANI-SiG/Primer were 0.430× 10-4, 1.110× 10-4, and 0.599 × 10-4, respectively and that of neat primer was 1.977 × 10-4. The corrosion protection efficiency of the primer was improved up to 7% on introduction of the PANI-based fillers. The 5 wt% of 1:1 PANI-SiG/primer composite, which contains 2.5wt% of PANI, showed better results than that of 5wt% PANI in Primer and these results are very close to that of 5wt% SiG/Primer composites.
Polyetheretherketone (PEEK) is a semicrystalline thermoplastic polymer with high chemical resistance, thermal stability and excellent mechanical properties. In the present work, neat PEEK and 3% bioactive glass/PEEK composites were annealed at various temperatures (100 °C, 200 °C and 300 °C) for (30 and 60) min and characterized with mechanical and density tests, differential scanning calorimetery and Fourier transform infrared spectroscopy. Results manifested bioactive glass powder enhanced the properties of the PEEK matrix. Thermal annealing at (200 and 300 °C) had a positive influence on the mechanical properties and density owing to increase in the level of crystallinity, whereas annealing at (100 °C) had not effect on the properties.
Most of the recent reduced graphene oxide (rGO) based sensors shows gas sensitivity above 50o to 150°C. The present investigation deals with the gas sensing at 50°C temperature. In the present research work, thick film sensors of rGO were developed on glass substrate by using standard screen-printing technique. The silver paste of rGO was used to make electrodes for contact on thick films for the electrical and gas sensing system. The electrical properties of rGO thick films such as resistivity, activation energy and temperature coefficient were studied. The resistivity of rGO thick films was found to be 84.84 Ω/m. The morphological, elemental and structural properties of rGO thick films were analyzed by SEM, EDS and XRD techniques respectively. The crystallite size of rGO thick films was found as 28.42 nm by using Scherer’s formula. The rGO thick films were prepared and exposed to Ethanol, NH3, NO2 and LPG gases to determine sensitivity and selectivity. The sensitivity of NO2 has been found to be maximum among other exposed gases. The maximum sensitivity of NO2 gas was 92.55 % at 50 °C found with fast response (~ 11 sec) and recovery (~ 19 sec) time.
Ancient archaeological sites contain numerous pottery objects that suffered from different deterioration factors. This study aims to use different analytical methods to study the chemical and mineralogical composition and identification of deterioration aspects of some ancient Egyptian pottery jars from Saqqara excavation. Thus, to explain the deterioration factors' mechanisms and apply the proper conservation methods to the deteriorated pottery jars. AutoCAD, digital microscope, scanning electron microscope (SEM-EDX), and x-ray diffraction (XRD) were used to clarify the preservation states of pottery jars. The results of the investigation revealed that the selected jars suffered from different cracks, salts crystallization, some surface black spots, separation of the slip layer, and heterogeneity in the grains size. XRD analysis revealed that quartz, diopside, illite, muscovite, orthoclase, anorthite, and hematite are the main components of the jars. SEM-EDX analysis showed high concentrations of chlorides and sulfate salts, besides the presence of manganese oxide. Different treatments were performed for the pottery jars include mechanical and chemical cleaning. Additionally, the completion process was done by using a mixture of dental gypsum with grog. Moreover, the consolidation process was achieved by using paraloid B-72.
Characterization of electrical parameters of Copper Phthalocyanine dye has been done in the present work. In the context of electrical parameters, the Schottky barrier and ideality factor of the organic device has been measured and the effects of fullerene nanoparticles on these parameters have been studied. Analysis of electrical parameters has been done by the current-voltage characteristics of the device. The influence of fullerene nanoparticles lessens the Schottky barrier to 0.71 eV from 0.75 eV. The current flow is assumed to be injection limited as the Schottky barrier is greater than 0.3 eV - 0.4 eV. The Schottky barrier is also estimated by the Norde method. Norde's method shows lessening of barrier height from 0.70 eV to 0.65 eV under the influence of fullerene nanoparticles. The measured ideality factor value reduces from 3.787 to 1.495 in presence of fullerene nanoparticles. The charge injection mechanism at metal-organic contact gets influenced by the interfacial Schottky barrier height. Decrease in both Schottky barrier and ideality factor attribute to the increase in charge flow and it allows a reduction in the device’s transition voltage from 2.5 V to 1.0 V.
The design of the optimal shape of patch with a good compromise between mechanical performances and manufacturing aspects can be sought in order to get the maximum structural safety-cost ratio. In this work an analysis has been conducted for development of a finite element methodology to circumvent the thermal effect problem in the bonded repair. Physical and geometrical parameters of the repair material were assumed to be variables, this method are based on two approaches: The first, have modified the patch shape by removing the two isosceles notches (h varied) for minimisation the heating size in the direction of loading. For the second step of the study, the same surface previously deduced are compensate in the other direction with varied the property module for the adhesive layer, for inducing a larger the area covering of crack tip and reduce the thermal stress. The values of thermal stresses obtained from the variation of these two parameters were found to be low compared to the obtained values for initial shape.
The present numerical work, based on the finite volume method, deals with the characterization of natural convective flow and thermal fields inside differentially vertical heated square cavities filled with a nanofluid as well as the quantification of the convective exchanges. The investigation is devoted to study the influence of the hybrid nanofluid (Al2O3-Cu / water) on the flow’s general structure with a particular attention to the Nusselt number. An exhaustive parametric study is conducted considering different combinations of Al2O3 and Cu nanoparticles (NPs) dispersed in water for a range of Rayleigh numbers (Ra) and total volume fractions An appropriate agreement with experimental data was observed for the estimation of the hybrid nanofluid thermal conductivity. From the results, it is observed that the heat transfer intensifies by increasing the Ra number and the nanoparticles volume fraction. The hybrid nanofluid seems to be the most efficient nanofluid in comparison with a base fluid and a single nanofluid. This heat transfer enhancement becomes more convincing with the increase of the Cu NPs content (% in volume).
In this paper, the flexural strength of concrete using alccofine and nano-silica was investigated experimentally and analytically. 15% alccofine and 3% nano-silica by weight of cement was used as a binary and ternary blend in three concrete grades M40, M50, and M60. Compressive strength and flexural strength were obtained experimentally by curing the specimens in water for 28 days. The empirical equation between compressive strength and flexural strength in the form of fr =bfc’n was obtained using regression analysis. The proposed empirical relation was compared with relations given by a code of practices and the relations reported by other researchers for predicting flexural strength using the compressive strength of concrete. The accuracy of the proposed empirical relation was validated using various statistical equations. From the experimental results, it was found that the cubic compressive strength and flexural strength of ternary blended concrete mixes using alccofine and nano-silica was 20 to 29% and 32 to 39 % higher compared to the control mixes. From the values of statistical equations, the proposed relation was found accurate. It showed less error compared to other relations and can be used to determine flexural strength results based on compressive strength data.
Grinding aids to increase grinding efficiency in cement production are materials that can produce large amounts of high-quality cement in a short time by reducing surface energy by preventing particle agglomeration and improving fluidity. In the paper, a grinding aid using glycerol-waste antifreeze(GAP) is prepared and its effect on the grinding properties of clinker is investigated in contrast to that without the grinding aid. The results are as follows: The angle of repose of the cement powder added with GAP decreases as the grinding time increases (decreases by 3.8° when the grinding time is 60 minutes), indicating that it increases the flowability of the powder. On the contrary, the residual amount of 45µm sieve is also significantly reduced (4.6% decrease) and the specific surface area increases (30.5m2/kg), which results in an increase in the grinding efficiency. In the size range of 3 to 32µm, it increases the particle content, makes the particle size distribution uniform, the 7d and 28d activity index of the powder is improved by 5% and 6%, respectively, and increases the compressive strength of the cement. In addition, it is confirmed that the performance of the TEA grinding aid and the grinding aid are similar, and are very effective in terms of economy.