Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

In the current investigation, a new series of Ce doped gahnites of the formula ZnAl2-xCexO4 (x = 0–0.04), Fe doped gahnites of the formula ZnAl2-yFeyO4 (y = 0–0.5) and Ce and Fe co-doped gahnites of the formula ZnAl2-x-yCexFeyO4 (x = 0–0.04; y = 0–0.5) with high near infrared (NIR) reflectance were fabricated to mitigate the heat island effect. All the designed pigments were characterized by powder X-ray diffraction (PXRD), Fourier transformed infra red spectroscopy (FT-IR), Ultraviolet-Diffuse reflectance spectroscopy (UV-DRS). Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM) and CIE-L*a*b* colour values. Band gap of the white gahnite of the formula ZnAl2O4 (Eg = 3.8 eV) shifted to 2.70 eV and 2.15 eV for the pigments ZnAl1.96Ce0.04O4 and ZnAl1.5Fe0.5O4 respectively. Ce doped gahnites broadened the absorption centre from 250 nm to 350 nm in the UV spectrum and resulted in yellow colour. Whereas Fe doping introduced additional electronic transition between 440 nm and 490 nm and exhibited reddish yellow colour. NIR reflectance of ZnAl1.96Ce0.04O4, ZnAl1.5Fe0.5O4 and ZnAl1.78Fe0.2Ce0.02O4 was found to be 86%, 65%, 80% respectively between 700 and 2500 nm regions. Good thermal and chemical stability along with high NIR reflectance made the prepared pigments as a potential candidate to design cool roofing materials. © 2019 Elsevier B.V.

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Journal of Alloys and Compounds

Ce and Fe doped gahnite: Cost effective solar reflective pigment for cool coating applications

A new sequence of novel yellow pigments Sr1-xCexMoO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) was prepared by following low temperature hydrothermal method. The bandgap of the materials was decreased from 3.95 eV to 3.48 eV with an increase in the Ce3+ substitution. SrMoO4 rhomboids have turned into spherical balls as the Ce3+ substitution increased. Substitution of Ce3+ in Sr2+ lattice altered white SrMoO4 (b* = −2.46) into yellow (b* = 30.34). With 75% of solar reflectance, Sr0.6Ce0.4MoO4 could serve as a cool pigment and an excellent alternative for toxic pigments. © 2019 Elsevier B.V.

Materials Letters

Low-temperature synthesis of environment-friendly cool yellow pigment: Ce substituted SrMoO4

Nickel doped Mn2P2O7 pigments of the formula NixMn2-xP2O7 (x = 0.0.5, 1.0, 1.5, 2.0) were prepared by precipitation and hydrothermal methods and characterized by PXRD, FT-IR, UV-DRS and SEM - EDX. The colour parameters were studied using CIE-LAB parameters. It is noteworthy that when x = 0 reddish pink colour was observed in precipitation method whereas in hydrothermal method pale pink colour was noticed. The colour hue change from pink to yellow was observed when x value is increased from 0 to 2.0. Well defined morphology was obtained in hydrothermal method, whereas precipitation method leads to the formation of irregular morphology. NIR Solar reflectance (R*) was found to be 79% for x = 0 prepared by hydrothermal method but by precipitation method it was reduced to 65%. Increased lightness (L*) value (less intense) was noticed for the all samples prepared by hydrothermal method compared to precipitation method (more intense). A yellow pigment which is free of chromium, cadmium and lead was obtained. © 2018 Elsevier B.V.

Effect of preparation methodology on the colour and the NIR reflectance of nickel doped manganese pyrophosphate

Nickel aluminate (NiAl2O4) and doped nickel aluminate (Ni1-xMxAl2O4; M = Mg, Zn, Cu; x = 0.1) were prepared by sol-gel method using citric acid. The synthesized compounds were analyzed by various techniques such as powder XRD, FTIR, SEM-EDAX and UV-DRS. The lattice parameter was found to increase with the copper, zinc and magnesium doping in nickel aluminate. The band gap was decreased from 3.0 eV (NiAl2O4) to 2.9 (zinc doped), 2.7 eV (magnesium doped) and increased to 3.1 eV in the case of copper doping. The catalytic study was carried out for a cationic (methylene blue) and an anionic dye (methyl orange). The percentage degradation of methyl orange using Zn0.1Ni0.9Al2O4 and Mg0.1Ni0.9Al2O4 was found to be 92% (180 min) and 96% (90 min). 93% (120 min) and 97% (120 min) degradation of methylene blue was observed using zinc doped and magnesium doped nickel aluminate respectively. These results are comparatively higher than its parent analogue (94% (180 min) degradation against methyl orange and 91% (120 min) against methylene blue). Whereas the percentage degradation was found to be less in the case of Cu0.1Ni0.9Al2O4 (83% (180 min) against methyl orange and 90% (120 min) against methylene blue). © 2018 Elsevier Masson SAS