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The samples of Y0.2Bi0.2LaxGd2.6-xFe5O12 (x = 0, 0.2 and 0.4) were successfully prepared by sol–gel auto combustion method. X-ray diffraction (XRD) study reveals that garnet phase is dominant in all prepared samples. The crystallite size of the samples is in 33–54 nm range. The crystallite size varies with varying La+3+substitution in the samples. The calculated grain size of the samples is in 0.100 to 0.116 μm range. Energy dispersive X-ray (EDX) mapping confirms the presence of all elements in the formed samples. From Ultraviolet– Visible (UV–VIS) spectroscopy it has been found that the samples have wide band gap (3.7 eV to 3.9 eV) which suggests that such materials can be operated in higher temperature, voltage and frequency. This makes these materials suitable in military application. From vibrating sample magnetometer (VSM) it has been clear that addition of La3+ changes the value of coercivity (Hc) and magnetic saturation (Ms) which make these materials suitable for switching devices and for antenna applications. The value of operating microwave frequency (ωm) suggests the use of such materials in devices operated in Ultra High frequency region.

The influence of Er3+–Mn2+ substitution on the properties of Y-type hexaferrites (chemical composition: Ba2–xErxZn0.6Co0.6Cu0.8Fe12−yMnyO22 (x = 0.0, 0.3, and 0.5 and y = 0.0, 0.4, and 0.6)), which were synthesized by the sol-gel autocombustion method, was investigated. The X-ray diffraction spectra were analyzed by the Rietveld refinement method, and hexaferrite was observed to possess a single-phase crystalline structure, whereas the Fourier-transform infrared spectra clarified the formation of the iron oxide base material. The morphology of the grains revealed that they were hexagonal and without agglomeration. The band gap of the samples decreased as the Er3+–Mn2+ concentration increased. Dielectric and impedance spectroscopies of the prepared samples indicated the role of polarization in the variation in the dielectric and impedance parameters. Particularly, the occurrence of space-charge polarization increased the dielectric constant at lower frequencies. Further, the Cole–Cole plot revealed a semicircle in the lower frequency region, thereby indicating that the grain boundary contributed the most to the dielectric constants. Modulus spectroscopy revealed that the charge mobility increased as the concentration of Er3+–Mn2+ increased. Additionally, the magnetic analysis indicated that Mn2+ preferably replaces Fe3+ at the octahedral site, thereby reducing the magnetization of the prepared samples through a reduced superexchange interaction. Furthermore, increasing the coercivity values thermally stabilized the sample, and this is vital for perpendicular magnetic recording.

Due to presence of external loads, the bolt providing stability to the structure which on failure may create a hazardous situation in case of mining and construction activities. The failure may be due to the failure of bolt itself or the failure of grout (in case of grouted bolt) along the bolt grout interface or the grout rock interface. It is thus necessary to study the effect of variation of a number of factors on the pull-out resistance and hence the failure of bolt. These factors comprise of the kind of bolt used, kind of grout material used, dimensions of bolt used etc. The objective of this research is to simulate the pull-out behaviour of cable bolt using 3DEC software and study the influence of various factors for the cases of grouted and non-grouted bolt. These factors are diameter of the bolt, length of the bolt, rate of extraction of the bolt, confining pressure, thickness of grout material and angle of friction of the grout material.

Ni2+-La3+ substituted CCTO ceramic was fabricated via sol-gel autocombustion method. After calcination at 800 ° C for 6 h, the heat-treatment temperature was varied from 800 ° C to 1000 ° C. The samples were labelled T1, T2, T3 and T4 to represent heat-treatment temperature of 800 ° C, 800/800 ° C, 800/900 ° C, and 800/1000 ° C respectively. The effect of this variation in temperature on the optical, dielectric, morphology, phase as well as crystal structure evolution was studied using various characterization tools. The XRD spectra confirm the presence of secondary phases such as CaTiO3, CuO, and anatase phase of TiO2 in all the samples except the sample with T4. However, Raman spectroscopy shows that the sample with T4 contains some amount of these secondary phases; this contradiction arises because of the better sensitivity of Raman spectroscopy as compared to XRD. The morphology of the prepared Ni2+-La3+ substituted CCTO ceramic tend to evolve with temperature as observed in FESEM micrographs, the known cubic shape of CCTO ceramic evolves with increase in temperature and becomes dominant in the sample with T4. The observed inter planar spacing in the HRTEM support the values observed from XRD analysis whereas the SAED pattern indicate that the Ni2+-La3+ substituted CCTO ceramic is polycrystalline in nature. The plot of band gap against changes in heat-treatment temperature shows a decreasing behaviour with increase in heat-treatment temperature which could be ascribed to changes in the local atomic lattice of the Ni2+-La3+ substituted CCTO ceramic. The dielectric properties were explained according to internal barrier layer capacitance (IBLC) model. Dielectric analysis shows that the sample with T4 exhibits the highest values of dielectric constant (40400) at low frequency which we assumed to be a consequence of space charge polarization.

Paint pigments belong in the daily-uses classification which are required to have a certain set of substantial qualities, such as; it is needed to be corrosion proof, rust proof (which further leads to longer life), thermally stable, should not react with the environment etc. Sol-Gel Auto-combustion and Ultrasonic Assisted Sol-Gel method was employed on to obtain CdO and TiO2 nanopowders respectively and their composite mixture was studied to understand the outcomes of incorporating TiO2 in another metal oxide CdO. The structural and morphological studies of the pure and the blended composition were analysed with the help of XRD, FTIR, Raman Spectroscopy and FESEM while the conductive nature was investigated through Maxwell-Wagner model and Koop’s phenomenological theory. The formation of CdO and anatase TiO2 was confirmed through XRD with the emergence of standard peaks for both the mentioned metal oxides. The characteristic FTIR peaks were acquired for CdO (410.05–678.41 cm−1) and TiO2 (845.45–850.87 cm−1 and 1391.45 cm−1) and the standardised Raman peaks were also obtained for both CdO (144.66–954.01 cm−1) and TiO2 (147.49–634.52 cm−1). The FESEM study showed the structural formation for CdO and TiO2 while the EDX analysis showed the emergence of peaks of Cd, O & Ti for the studied sample cases. The Dielectric Analysis revealed the drop in the conductive graph. The fore-mentioned composite sample can have its consideration for the raw materials used in paints.

Pr Co–substituted calcium copper titanate (CCTO) ceramic with chemical composition Ca1-xPrxCu3-yCoyTi4O12 (x = 0.0, 0.1, 0.2, 0.3 and y = 0.0, 0.4, 0.5, 0.6) was synthesized by the sol-gel method. The X-ray diffraction patterns indicate that all the synthesized samples exhibit a pure phase of CCTO ceramic with absence of secondary phases such as CaTiO3 and CuO. The weight losses observed in the thermogravimetric analysis graph cease to occur at 895 ° C, indicating the formation of the final CCTO product. Field-emission scanning electron microscopy micrographs show dense and closely arranged faceted grains with the absence of agglomeration and liquid oxide phase. Energy-dispersive X-ray spectroscopy spectra confirm the stoichiometry of the synthesized CCTO ceramic, and Raman analysis rules out the presence of secondary phases; hence, the purity of the synthesized CCTO ceramic is further supported by Raman and energy-dispersive X-ray spectroscopy spectra. The optical band gap increased with Pr Co substitution, and a maximum value of 3.88 eV was obtained in the sample with x = 0.0/y = 0.0. The dielectric properties are explained on the basis of a Maxwell-Wagner relaxation process. The sample with x = 0.0/y = 0.0 shows the highest room-temperature dielectric constant (4920) at a frequency of 100 Hz. The lowest value of the room-temperature dielectric loss tangent (0.194) at 100 Hz was observed in the sample with x = 0.1/y = 0.4. The Cole-Cole plot indicates that most of the contribution to the dielectric properties of the synthesized CCTO ceramics originates from grain-boundary resistance.

M-type hexagonal ferrites have found considerable application in electronics industry as a result of tuning the electrical, dielectric and magnetic properties to match with the intended application. M-type hexagonal ferrites with improved dielectric properties are useful in high frequency application. In this research, we studied the effect of heat treatment in M-type barium hexagonal ferrites with chemical composition Ba1-xAlxFe12-yMnyO19 (x=0.6 and y=0.3) synthesized by sol-gel auto-combustion method. The prepared sample was sintered at four different temperatures (T= 750°C, 850°C, 950°C and 1050°C). The synthesized samples were characterized using X-ray diffraction (XRD), field electron scanning electron microscopy (FESEM), impedance analyser and UV-Vis spectroscopy. The band gap of the prepared sample is obtained from UV-Vis spectroscopy data. The dielectric properties were explained on the basis of Koop’s phenomenological theory and Maxwell Wagner model. The prepared sample exhibit high dielectric constant at low frequency which is typical of a ferrite material. The sample calcined at and 750°C has the highest dielectric constant at high and low frequency. Lowest dielectric loss at high frequency is observed in the sample calcinated at 1050°C while that calcinated at 850°C show the lowest loss at high frequency.

We report the effect of dielectric layer and its selection criterion to produce diffuse dielectric barrier discharge plasma at atmospheric pressure. The dielectric barriers over electrodes are used to prevent glow-to-arc transition by limiting growth of discharge current. We have analyzed the dielectric properties such as secondary electron emission, dielectric constant, dielectric thickness etc in order to get better power efficiency at breakdown. It is observed that a thin dielectric layer with high dielectric constant is suitable for lowering the breakdown voltage. During one of our experiments, planar-surface discharge plasma was produced with the use of epoxy resin dielectric-covered stripe electrodes. High-voltage high frequency signal was applied between the electrodes to produce the discharge. It is observed that the discharge remain stable & uniform in our parametric range. However, after prolonged discharge operation, degradation of dielectric layer was observed in the form of powder formation over the dielectric insulation. SEM analysis reveals that the powder contains individual as well as cluster of particles of micrometer size dimension. Such micro-particle formation may be useful for some material and biomedical applications, however in other way degraded dielectric would lead to spark formation in plasma. In this context, theoretical and experimental analysis of our results is presented in this paper.

Construction of tunnels through naturally fragile, weak and sheared rock masses is a challenging task for engineers, planners, designers and geologists. The presence of discontinuities like folds, faults, voids, number of shear zones, highly changing geological conditions with thick vegetative cover and over burden pose threat to construction activities in frail and fragile rock mass. These discontinuities get further separated and more widened as the excavation of tunnels involve drilling and blasting operations and do not allow the rock mass to behave monolithically. Proper grouting of the surrounding rock mass around the opening ensures the monolithic behavior of the rock mass. Contact grouting or back fill is required for filling of spaces between concrete lining or steel lining and shattered surface of the parent rock. Consolidation grouting in tunnels is essential to reduce the co-efficient of permeability and for strengthening the rock mass by filling up the open joint cracks. This paper deals with the proper grouting of the surrounding shattered, sheared and fragile rock mass around the power tunnel lining to ensure its monolithic behavior.

The current work involves the synthesis of MnxCo0.5-xZn0.5Fe2O4 (x = 0.0, 0.1, 0.2, 0.3, and 0.4) by adopting sol-gel auto combustion technique. For all the samples, the single-phase spinel structure with cubic symmetry was assured by the XRD studies. The crystallite size lies in the nanoscale range of 35.4 to 43.6 nm as estimated by utilizing Debye-Scherrer formula. FTIR spectroscopy affirms the formation of spinel structure due to the appearance of characteristic vibrational bands near 400 and 600 cm-1 which corresponds to the octahedral and tetrahedral sites respectively. FESEM micrographs reveal the presence of non-uniform grain growth which was agglomerated, inhomogenous in size and shape, and having porous morphology. VSM study exhibits soft ferromagnetic nature due to the low coercivity value. There is a decrement in the saturation magnetization with increasing Mn2+ concentration which is due to the decrease in the crystallite size and non-magnetic nature of the Mn2+.

The Co2Y-type barium hexaferrite Ba2−2xCrxNixCo2Fe12O22 (x = 0.0, 0.1, 0.15) was synthesized using the sol–gel auto-combustion technique. The formation phase of the Y-type hexaferrites was observed using X-ray diffraction (XRD) analysis. Fourier-transform infrared (FTIR) analysis confirms the formation of Y-type hexaferrites. Field-emission scanning electron microscopy (FESEM) reveals particles with hexagonal plate-like morphologies. The optical band gap of the prepared samples lies between 0.74 and 2.16 eV. The coercivity values of the prepared samples demonstrate their soft-magnetic nature. Dielectric analyses show the influence of the dopant ions on the dielectric parameters of the prepared samples. Impedance spectroscopy using a Nyquist plot shows that most of the dielectric response results from grain-boundary contributions.

Nanocomposite of reduced graphene oxide (rGO) stabilised by biodegradable polymer (chitosan), polyaniline and sol-gel derived calcium copper titanate (CCTO) with chemical composition Ca 1-x Ce x Cu 3 Ti 4-y Ni y O 12 (x=0.0, 0.25, 0.45, and y=0.0, 0.3, 0.5) was synthesized. The role of the chitosan is to ensure that the RGO sheets do not restack into graphite. The characteristics D and G bands of graphene oxide (GO) at 1595 and 1353 cm -1 indicate the formation of GO. Dielectric constant and dielectric loss were calculated from the impedance analyser data. The dielectric properties were explained on the basis of Maxwell-Wagner relaxation model and Koop’s phenomenological theory. The rGO/PANI/CaCu 3 Ti 4 O 12 nanocomposite shows the highest dielectric constant (7244).

Y-type hexaferrites powder samples of Ba1·8Sr0·2Co2Fe12-xTbxO22 (with x = 0.0, 0.1, and 0.2) were prepared by the method of sol-gel auto combustion. XRD and Rietveld refinement analysis shows that the prepared Y-type hexaferrites samples exhibit pure crystalline phase with the absence of impurity. FTIR study gives an idea of the formation of Y-type hexaferrites by the appearance of three characteristics bands at 409, 433, and 552 cm−1. FESEM analysis shows plate-like morphology with the presence of all hosts and substituted elements observed in the EDX spectra and mapping. The grain size decreases with increase in the concentration of Tb3+, the particle size was observed to be in the range 56.48–58.54 nm. Typical dielectric response of ferrites was observed in the dielectric analysis. Cole-Cole plot shows that the contribution of grain is negligible compared to grain boundaries contribution. The multi domain magnetic nature of the prepared Y-type hexaferrite samples resulted in domain wall displacement and consequently influences the values of the coercivity.

The experimental observation of a two-dimensional self-organized square lattice pattern in a planar surface barrier discharge is reported. The discharge was operated near atmospheric pressure in helium gas. The transition from irregular plasma spot pattern to a square lattice pattern is achieved by reducing the discharge driving frequency. On increasing the driving frequency the regular lattice pattern is destroyed and again transforms to an irregular plasma spot pattern. Dielectric degradation and powder formation is also observed after discharge process. Spatio-temporal behavior of observed plasma pattern is presented.

We have synthesized single phase Ni+2-Co+2 substituted bismuth copper titanate (Bi2/3Cu3Ti4O12) electroceramic using the sol-gel autocombustion method. The XRD patterns reveal that the prepared BCTO electroceramic are of single phase without the presence of any other phases such as CuO or TiO2. FESEM micrographs show particles with well-defined cubic shape of bismuth copper titanate ceramics. EDX spectra shows all the chemical elements of the prepared composition, this confirm the stoichiometry and the purity of the synthesized electroceramic. The optical band gap study was carried out using UV–Vis–NIR spectroscopy in the region 225–1000 nm and the highest value of 3.63 eV was observed in the sample having x = 0.1. The dielectric response and impedance spectroscopy of the electroceramic were discussed based on Debye-type relaxation process and Maxwell-Wagner model. The sample having x = 0.0 shows the highest dielectric constant (3800) at room-temperature and a frequency of 42 Hz as compared to x = 0.1 and x = 0.2. The Cole-Cole plots of complex impedance and complex electric modulus indicate that grain-boundary resistance is the major contributor to the dielectric response of the prepared BCTO electroceramic.

Activated bark prepared from Mangifera indica was used for the removal of Cr(VI) from aqueous solution. Activated bark (AB) was characterized by some instrumental techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis (TGA). The effect of different adsorption parameters such as metal ion concentration, adsorbent dosage, contact time, pH, and the temperature was optimized. Langmuir, Freundlich, and Tempkin’s isotherms were studied for the interpretation of experimental data. Langmuir model was found to be best fitted with a maximum adsorption capacity of 78.96 ​mg/g. The kinetic study was described by pseudo-first-order kinetics and Elovich model. Kinetic study indicates that physio-adsorption play major role in Cr(VI) removal from water system. The thermodynamic parameters such as energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were found to be spontaneous, feasible, and endothermic nature.

Co2Y/BCTO/PANI composite was synthesized using mechanical blending method. The XRD analysis shows that the composite exhibit pure phase of Co2Y barium hexaferrite and bismuth copper titanate (BCTO) which is also supported by Raman analysis. Resonance occurs over the whole frequency region in the spectra of Co2Y/BCTO/PANI composite with dielectric losses dominating the lower frequency region due to interfacial polarization and magnetic losses dominating the higher frequency region as a result of eddy current losses, natural and exchange resonance. The observed values of shielding effectiveness for reflection are higher than those of shielding effectiveness for absorption, this indicates that most of the incident EM wave is reflected rather than absorbed. The Co2Y/BCTO/PANI composite shows total shielding effectiveness value above 20 dB with maximum total shielding effectiveness value of 31.97 dB at 10.30 GHz and matching thickness of 2 mm. The high value of total shielding effectiveness is attributed to good impedance matching between the components of the Co2Y/BCTO/PANI composite as well as higher dielectric losses as compared to magnetic loses.

Dy3+-Cr3+ substituted barium hexaferrite was synthesized using sol-gel method. The variation in the saturation and remnant magnetization suggest that the amount of Cr3+ ions occupying 4f2 crystallographic site is greater than those occupying 12k and 2a crystallographic sites thereby resulting in increased saturation and remnant magnetization. The decrease in saturation and remnant magnetization indicate that Cr3+ ions replaces Fe3+ ions at 12k and 2a site because the net magnetic moment of Cr3+ (3 μ B ) is less than that of Fe3+ (5 μ B ). Ligand theory and analysis of Mossbauer parameters also suggest that Cr3+ ions occupy 4f2, 2b, 2a, and 12 k sites. This shows that various proportion of Cr3+ replaces Fe3+ ions at different sites depending on factors such as site preference, magnetic moment of Cr3+ ion, isomer shift, hyperfine splitting, quadruple splitting, relative area as well as anisotropy constant. Raman analysis complements the findings of the magnetic and Mossbauer analysis.