Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Cerium oxide nanoparticles (CeO2 NPs) are favorable in nanotechnology based on some remarkable properties. In this study, the crystalline CeO2 NPs are successfully prepared by an efficient microwave combustion (MCM) and conventional route sol-gel (CRSGM) methods. The structural morphology of the as-prepared CeO2 NPs was investigated by various spectroscopic and analytical techniques. Moreover, the XRD pattern confirmed the formation of CeO2 NPs as a face centered cubic structure. The magnetometer studies indicated the low saturation magnetization (23.96 emu/g) of CeO2 NPs for weak paramagnetic and high saturation magnetization (32.13 emu/g) of CeO2 NPs for super paramagnetic. After that, the oxidation effect of benzyl alcohol was investigated which reveals good conversion and selectivity. Besides, the CeO2 NPs modified glassy carbon electrode (GCE) used for the detection of nitrite with linear concentration range (0.02–1200 μM), low limit of detection (0.21 μM) and higher sensitivity (1.7238 μAμM−1 cm−2). However, the CeO2 NPs modified electrode has the fast response, high sensitivity and good selectivity. In addition, the fabricated electrode is applied for the determination of nitrite in various water samples. Eventually, the CeO2 NPs can be regarded as an effective way to enhance the catalytic activity towards the benzyl alcohol and nitrite.

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Environmentally friendly synthesis of CeO 2 nanoparticles for the catalytic oxidation of benzyl alcohol to benzaldehyde and selective detection of nitrite

The structure evolution of surface NiAl2O4 spinel phase in NixAl1O2-δ mesoporous catalysts, synthesized by the citric acid sol-gel method, was systematically investigated. Small-size Ni nanoparticles, obtained by partial reduction from NiAl2O4 spinel in NixAl1O2-δ catalysts with low Ni contents at high temperature, can effectively inhibit the carbon formation from kinetics, while the irreducible NiAl2O4 counterpart can participate in elimination of carbon deposition. The constructed structure of Ni0-NiAl2O4 interfaces, produced by exsolution of Ni from NiAl2O4 spinel, is responsible for its high long-term stability and excellent resistance to coking and sintering for dry reforming of methane (DRM) reaction. The structure sensitivity and kinetic compensation effect of CH4 dissociation on Ni0 active sites are observed. DRM reaction proceeds via a Langmuir-Hinshelwood mechanism accompanied by an additional redox mechanism. It is noteworthy that the active oxygen species generated by filling the oxygen vacancies of NiAl2O4 spinel by CO2 provide another rapid redox route to eliminate carbon species.

NixAl1O2-δ mesoporous catalysts for dry reforming of methane: The special role of NiAl2O4 spinel phase and its reaction mechanism

NiAl2O4, CuAl2O4, and ZnAl2O4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine (DEA) as a fuel. The effects of calcination temperature on structure, crystallinity, morphology, and optical properties of MAl2O4 (M = Ni, Cu, Zn) have been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy. The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl2O4, CuAl2O4, and ZnAl2O4 at 1200, 1000, and 600 °C, respectively. The direct band gap of these aluminate spinels, calculated from UV-DRS spectra using the Kubelka-Munk function, is found to increase with calcination temperature. The PL spectra demonstrate that NiAl2O4 gives the highest blue emission intensity, while CuAl2O4 and ZnAl2O4 exhibit a very strong violet emission. During fluorescence process, the ZnAl2O4 emits visible light in only violet and blue regions, while NiAl2O4 and CuAl2O4 emissions extend to the green region. It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.

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Effect of calcination temperature on structural and optical properties of MAl2O4 (M = Ni, Cu, Zn) aluminate spinel nanoparticles

Combustion synthesis, structure, magnetic and optical properties of cobalt aluminate spinel nanocrystals

Comparative investigation of nickel aluminate (NiAl2O4) nano and microstructures for the structural, optical and catalytic properties

An essential tool for describing human emotion is facial expression. From morning tonight, people go through a broad spectrum of emotions that may be caused by their mental or physical health. The six major facial expressions of happy, sorrow, surprise, fear, disgust, and rage are now classified by psychology as six universal emotions, despite the fact that humans experience a broad variety of emotions. Facial muscle movements may be used to determine humane motions. The brow, lips, nose, and eyes are the four primary facial characteristics Facial recognition is a topic that is now the focus of much investigation. Finding a match between the input image and the images to red in the database is the aim of face recognition. Human- computer interaction and the solution to the problem of criminal identification depend on facial recognition. The data in face recognition tasks has a high intrinsic complexity, making the dimensionality reduction strategy essential. Picture space's dimensionality is decreased using PCA. In the domains of computer vision, image processing, pattern recognition and other areas, the modelling of the face using Gabor features has generated a lot of attention. The major justification for using the Gabor filter is its biological significance. Mammal primary visual cortex neurons have an accessible field profile that is oriented toward spatial frequency features. Additionally, Gabor filters may make advantage of well-known visual properties as spatial localization, orientation selectivity and spatial frequency feature. So, we are proposing this computational model approach for the detection of emotional changes using dataset from EMOTIC database by recognition system. In this approach we achieved around 88% accuracy which efficient and better when it's been compared with computer modeling Methodologies.

P. Surendhar

Papers

Comparative investigation of nickel aluminate (NiAl2O4) nano and microstructures for the structural, optical and catalytic properties

Human Computer Interface Application for Emotion Detection Using Facial Recognition