Photocatalytic degradation of VOCs from air stream using Mo:TiO2/GAC nanocomposites

Modification of TiO2 is one of the techniques used to enhance its photodegradation efficiency and to make it visible-light-active. In this study, Mo-doped TiO2 nanoparticles were synthesized using a fast sol-gel technique, and then coated on granular activated carbon (GAC) as both substrate and adsorbent to obtain Mo:TiO2/GAC composite. The fabricated composite was characterized using powder XRD, SEM, EDAX, FTIR, and BET analysis. Then the composite was applied to photodegrade volatile organic compounds (VOCs) under both UV and visible light irradiation. The characterization results showed high crystallinity and purity. Mo:TiO2/GAC composite had higher photodegradation efficiency compared with bare TiO2 and bare GAC. Moreover, studying operational parameters showed that the optimum condition for photodegradation efficiency of VOCs was at flowrate of 1 l/min, VOCs concentration of 20 ppm, and light intensity of 400 and 600 W/m2 for UV and visible light respectively. The results suggest that Mo:TiO2/GAC is a visible-light-active composite and can be acceptably used to decompose VOCs under visible light with adequate efficiency and without the generation of harmful by-products such as O3 as compared with UV.

Structural and Dielectric Progression of 5 % Gd Doped BiFeO3 Nanoparticles Through Cr (2-8%) Doping

This study reports the structural modifications in undoped multiferroic BiFeO3 (bismuth ferrite or BFO) nanoparticles caused by doping at both the A-site (by 5% Gd) and B-site (by 2-8% Cr) and the resulting improvements in dielectric characteristics. Both un-doped and doped BFO nanoparticles were synthesized using the sol-gel technique and annealed at 600°C for crystallization. X-ray diffractometry (XRD) reveals a phase transition from rhombic (R3c) to orthorhombic (Pn21a). Field Emission Scanning Electron Microscopy (FESEM) study shows the production of nanoparticles with sizes ranging from 80 to 130 nm. Impedance analyzer experiments (100 Hz-10 MHz) show that the dielectric characteristics of doubly doped BFO are very stable over a wide frequency range. The dielectric permittivity of co-doped BFO decreases with Cr doping concentration up to x = 0.06 before reversing. The conductivity drops dramatically as the Cr content rises. Journal of Engineering Science 12(3), 2021, 101-110

Characterization of physical properties of bismuth-titanium coatings on 316L stainless steel

The 316 L steel is a type of stainless steel widely used in the medical industry, which in recent years has been studied for different uses in society. Being an engineering material, it is imperative to know its performance based on its physical and mechanical properties that allow identifying the response of this steel in addition to thin films as coatings. Bismuth and titanium have been recently used to improve the properties of 316 L steel, so they were used in this study. The sol-gel technique was used as the film forming method. The response of physical and mechanical properties was evaluated from the analysis of microhardness and coefficient of friction reported for the different types of steel-coating systems. Higher microhardness values were found for films with higher proportion of titanium. The coefficient of friction values is influenced by the system used, with higher values obtained for samples with a single coating layer.

Sol-gel zinc oxide nanoparticles: advances in synthesis and applications

Zinc oxide nanoparticles (ZnO) exhibit numerous characteristics such as biocompatibility, UV protection, antibacterial activity, high thermal conductivity, binding energy, and high refractive index that make them ideal candidates to be applied in a variety of products like solar cells, rubber, cosmetics, as well as medical and pharmaceutical products. Different strategies for ZnO nanoparticles’ preparation have been applied: sol-gel method, co-precipitation method, etc. The sol-gel method is an economic and efficient chemical technique for nanoparticle (NPs) generation that has the ability to adjust the structural and optical features of the NPs. Nanostructures are generated from an aqueous solution including metallic precursors, chemicals for modifying pH using either a gel or a sol as a yield. Among the various approaches, the sol-gel technique was revealed to be one of the desirable techniques for the synthesis of ZnO nanoparticles. In this review, we explain some novel investigations about the synthesis of zinc oxide nanoparticles via sol-gel technique and applications of sol-gel zinc oxide nanoparticles. Furthermore, we study recent sol-gel ZnO nanoparticles, their significant characteristics, and their applications in biomedical applications, antimicrobial packaging, drug delivery, semiconductors, biosensors, catalysts, photoelectron devices, and textiles.

Insight into Structural and Optical Properties of Pristine and Sr2+ Doped La2NiMnO6

Double perovskites oxide (DPO) multiferroics La2-xSrxNiMnO6(x=0.0, 0.1, 0.2, 0.4, 0.6) are synthesized by sol-gel technique. The structural, optical and electrical (both DC and AC) properties of La2-xSrxNiMnO6 have been investigated by XRD and FTIR spectroscopy and two-probe resistivity and dielectric measurements as a function of temperature, respectively. The effect of doping of Strontium at A-site in double perovskites is discussed. XRD has revealed the formation of monoclinic structure of La2-xSrxNiMnO6 with space group P21 / n for x=0.0 and P21 for x=0.1, 0.2, 0.4, 0.6. The average crystallite size has been calculated to be in the range 31 to 46 nm as determined by Debye Scherrer equation. Infrared active optical phonons observed from reflectivity spectra have been analysed fitting the theoretical oscillators using Lorentz oscillator model. We have observed several well-resolved phonon modes in La2-xSrxNiMnO6 with increasing dopant concentration. Activation energy calculated using Arrhenius Plot is in the range of 0.31 to 0.18 eV, confirming the semiconducting nature of all samples. The dielectric constant and tangent loss as a function of temperature and frequency are also discussed for these multiferroics.

The Role of Different Lanthanoid and Transition Metals in Perovskite Gas Sensors

Beginning with LaFeO3, a prominent perovskite-structured material used in the field of gas sensing, various perovskite-structured materials were prepared using sol–gel technique. The composition was systematically modified by replacing La with Sm and Gd, or Fe with Cr, Mn, Co, and Ni. The materials synthesized are comparable in grain size and morphology. DC resistance measurements performed on gas sensors reveal Fe-based compounds solely demonstrated effective sensing performance of acetylene and ethylene. Operando diffuse reflectance infrared Fourier transform spectroscopy shows the sensing mechanism is dependent on semiconductor properties of such materials, and that surface reactivity plays a key role in the sensing response. The replacement of A-site with various lanthanoid elements conserves surface reactivity of AFeO3, while changes at the B-site of LaBO3 lead to alterations in sensor surface chemistry.

GROWTH OF COPPER SULPHIDE CRYSTAL IN GEL AND ITS THERMAL SPECTROSCOPIC SEMICONDUCTING CHARACTERISATIONS WITH KINETIC PARAMETERS

Copper sulphides crystals are grown using simple gel technique at ambient temperature. The various lattice parameters, gel aging time, gel setting time, Effect of pH observed, Different characterization like gel aging, pH of gel ,setting of gel with their analysis and Thermal behavior of grown crystal like Thermo gravimetric Analysis TGA are Discussed. The chemical analysis confirmed contents in grown crystal of copper sulphides

Synthesis of Silica-Based Materials Using Bio-Residues through the Sol-Gel Technique

This study focused on the use of citrus bio-waste and obtention of silica-based materials through the sol-gel technique for promoting a greener and more sustainable catalysis. The sol-gel method is a versatile synthesis route characterized by the low temperatures the materials are synthesized in, which allows the incorporation of organic components. This method is carried out by acid or alkali hydrolysis combined with bio-waste, such as orange and lemon peels, generated as co-products in the food processing industry. The main objective was to obtain silica-based materials from the precursor TEOS with different catalysts—acetic, citric and hydro-chloric acids and ammonium hydroxide—adding different percentages of lemon and orange peels in order to find the influence of bio-waste on acids/alkali precursor hydrolysis. This was to partially replace these catalysts for orange or lemon peels. The solids obtained were characterized with different techniques, such as SEM, FT₋IR, potentiometric titration and XRD. SEM images were compared with pure silica obtained to contrast the morphology of the acidic and alkali hydrolysis. However, until now, few attempts have been made to highlight the renewability of reagents used in the synthesis or to incorporate bio-based catalytic processes on larger scales.