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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.

A ternary reduced graphene oxide loaded InVO4-g-C3N4 nanocomposite was prepared by the wet impregnation method. The formation of InVO4-g-C3N4 heterojunction and loading of rGO was corroborated by XRD, FTIR, UV–vis, TEM and XPS studies. Incorporation of both InVO4 and rGO in g-C3N4 substantially increased the absorption edge of the photocatalyst from 451 nm (2.75eV) of g-C3N4 to 546 nm (2.27 eV) due to the formation of heterojunction. Interestingly, among the different weight % of both InVO4 and rGO loaded g-C3N4, 3.0 wt% of rGO and 30 wt% of InVO4 loaded g-C3N4 has shown a superior hydrogen production of 7449 μmol g−1h−1, a 45 times enhancement in comparison to g-C3N4. This can be related to the synergetic boosting of charge carrier separation at InVO4-g-C3N4 heterojunction and transportation through rGO support as revealed by photoluminescence and photocurrent studies. Moreover, the hydrogen production rate obtained in the present binary nanocomposite was almost 8 times higher than the previously reported hydrogen production rate using the same binary InVO4-g-C3N4 nanocomposites without rGO support.

Initially, three samples of carbon nanotubes (SWCNTs) were synthesized from neem tree material. Afterward, these samples were coated with hexagonal boron nitride (h-BN) to form h-BN and CNT composite (h-BN-CNT). The essence of using h-BN (being a perfect insulator) with armchair SWCNT (being a conductor) is to create an interface between an insulator and conductor. The samples were treated under three different transition metal nanoparticles, silver, iron, and nickel. Thermogravimetric (TGA) analysis reveals that h-BN/CNT is thermally more stable with silver than iron and nickel nanoparticles. TGA profile showed resistance to mass loss at the beginning due to the higher thermal resistivity by the impurity compounds. The DFT calculation, generalized gradient approximation (GGA), and Perdew–Burke–Ernzerhof (PBE) analysis found engineered bandgap energy of 3.4 eV for the synthesized h-BN-CNT heterostructure. Because of its unique structural and electronic properties such as tunable bandgaps, the h-BN-CNT heterostructure may open new ways for manipulating excitons in the CNTs, and thus can be explored to develop various new electronic devices.

A novel UV–visible light active oxynitride photocatalyst, ZnO:InN, has been demostrated to exhibit efficient hydrogen evolution from water as compared to some conventional photocatalysts. A reduction in bandgap (2.82 eV), as estimated from diffuse reflectance spectra, is explained using Valence band XPS studies and attributed to the upshift in valence band maximum. Photocatalytic activity of the samples has been demonstrated by organic dye degradation, where 92% decay was observed in 180 min under direct sunlight. Photoelectrochemical studies under visible light showed significant photoresponse with a photocurrent density of ∼8 μA/cm2. This study, as per our knowledge, is first of its kind where ZnO:InN oxynitride has been explored as a UV–visible light active photocatalyst with significant H2 generation of ∼48 μmol/g by UV–visible light water splitting using methanol scavenger. The results show the promising future applications of ZnO:InN oxynitride as a sunlight active photocatalyst for hydrogen production.

A solar light responsive Z-scheme AgI/rGO/BiVO4 ternary nanocomposite was designed by ultrasonic assisted hydrothermal and wet impregnation methods. XPS spectra showed a gradual positive peak shift in the binding energy of Bi, after rGO and AgI incorporation, indicating chemical bonding and electrons migration pathway from BiVO4 to AgI through the rGO layer. Furthermore, Raman analysis revealed a red shift in the characteristic Raman band of BiVO4, suggesting local structural changes upon rGO and AgI loading. In addition, the band gap of the nanocomposite for bare BiVO4 was found to be shifted to 2.24 eV from 2.36 eV, therefore, increasing the overall visible light absorption. Photocurrent measurements indicated the presence of significantly high surface charge trap states in bare BiVO4. However, the detrapping process was not observed suggesting fast recombination of trapped charges on the surface of bare BiVO4. After AgI and rGO loading, the surface charge trap states of BiVO4 disappeared, which reveals the quick shuttling of charge carriers via close interface bonding in the nanocomposites. The photocatalytic performance of the nanocomposites was tested with Tetracycline (TC), a common antibiotic and RhB dye, as model pollutants. The AgI/rGO/BiVO4 nanocomposite displayed nearly 84% and 99% photocatalytic degradation for TC and RhB, respectively under direct solar light irradiation in 25 min. The Total Organic Carbon (TOC) analysis revealed more than 35% and 25% mineralization efficiency for both TC and RhB under 2 h of reaction. The AgI/rGO/BiVO4 nanocomposite exhibited not only enhanced photocatalytic activity but also high stability because of the strong chemical bonding among AgI, BiVO4, and rGO, which largely circumvented the electron-hole recombination. Based on XPS, Mott-Schottky, and reactive radical trapping experiments, a Z-scheme charge carrier separation and migration pathway in the nanocomposite is proposed.

Graphitic carbon nitride, a 2 D layered photocatalyst coupled with transition metal oxides often shows promising photocatalytic hydrogen evolution activity. However, low surface area and poor charge separation greatly hinder its photocatalytic efficiency. A Ni+x (x=2, 3)/O-g-C3 N4 photocatalyst with a very high specific surface area (199 m2 g-1 ) has been prepared by thermal condensation and wet-impregnation methods. The oxygen-functionalized and Ni+x (x=2, 3)-coordinated g-C3 N4 produced 1664 μmol g-1 of hydrogen evolution from water under direct solar light irradiation in 4 h, which is 23 times higher than that over O-g-C3 N4 . This significant enhancement results from the combined effects of large surface area, the formation of long-life deep-trap states, effective charge carrier separation, and extended visible light absorption. The separation and transport behavior of the charge carriers are investigated by photoluminescence, time-resolved photoluminescence, photocurrent and Mott-Schottky measurements. Additionally, the interaction between Ni+x (x=2, 3) and O-g-C3 N4 is studied by X-ray photoelectron spectroscopy, X-ray diffraction, and FTIR spectroscopy. The Ni+x (x=2, 3)/O-g-C3 N4 photocatalyst shows remarkable reusability over a period of two months (six cycles). This study may provide a pathway to simultaneously overcome the challenges of low surface area and poor charge separation in g-C3 N4 -based photocatalysts.

Herein, a ternary nanocomposite, comprising metal oxide (InVO4 and TiO2) photocatalysts supported on rGO sheets was prepared via the hydrothermal method in the presence and absence of ultrasound irradiation. The photocatalytic performance of the prepared rGO/InVO4-TiO2 nanocomposites was evaluated for H2 evolution activity from water splitting with glycerol as a sacrificial agent. Interestingly, a synergistic effect (6-fold) was observed with rGO/InVO4-TiO2 nanocomposite prepared with the help of ultrasound compared to the samples prepared without ultrasound. The optimized nanocomposite (rGO/InVO4-TiO2) exhibited a maximum H2 evolution of 1669 μmol h−1, a ∼13-fold enhancement compared to the bare TiO2. This remarkable enhancement is mainly due to the synergistic effect induced by ultrasonic irradiation along with the shifting of the optical band gap of TiO2 from 3.20 eV to 2.80 eV by loading of InVO4 and rGO and also strong chemical bonding between metal (Ti) and C through Ti–C bond formation, as identified by UV–vis DRS spectra and XPS spectra, respectively. Moreover, a significant quenching of PL emission intensity and smaller radius arc of the Nyquist plot in the EIS were observed when the rGO and InVO4 were loaded in TiO2, indicating the efficient charge carriers separation and transfer in the presence of rGO sheet, resulting in enhanced photocatalytic activity. Thus, application of ultrasound has played significant and important roles in substantially enhancing hydrogen evolution along with rGO and InVO4 acting as support and co-catalyst, respectively.

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.

Novel multiwalled carbon nanotubes-graphene-TiO2 (CNT-GR-TiO2) composite materials without noble metal co-catalysts are designed for photocatalytic decomposition of water using solar light. The CNT-GR-TiO2 nanocomposite shows the highest H2 production rate of 29 mmol h−1g−1 under the full spectrum of solar light irradiation. The rate of H2 production is 8-fold higher than the commercial TiO2 (Degussa P25) and the estimated solar energy conversion efficiency is 14.6%. Spectroscopic and photocatalytic studies reveal that graphene acts as an electron reservoir through which interfacial charge transfer occurs for water splitting. The UV–vis-DRS study shows that the absorption peak maximum for anatase TiO2 occurs at ∼315 nm, which is shifted to ∼355 nm and 380 nm for GR-TiO2 and CNT-GR-TiO2 composites, respectively. The EPR spectra of GR-TiO2 and CNT-GR-TiO2 composites indicate that graphene and multiwalled carbon nanotubes in the composites promote the generation of Ti3+ and oxygen vacancies and in turn reduce the band gap of anatase TiO2 from 3.32 eV to 2.79 eV. This is corroborated by XPS and photoluminescence analyses of the samples. The role of CNTs is to prevent the restacking of graphene nanosheets and provide additional electron transport channels thereby suppressing the recombination rate of electron-hole pairs in the CNT-GR-TiO2 composite. The combination of all these factors results in increasing the hydrogen production rate from 19 mmol h−1 g−1 (anatase TiO2) to 22 mmol h−1 g−1 (GR-TiO2) to 29 mmol h−1 g−1 (CNT-GR-TiO2).

In this research, nanocomposites comprising M-type strontium hexaferrites (SrM) SrFe12−xCsxO19 (x = 0.0, 0.05, 0.10), calcium copper titanate (CCTO) CaCu3Ti4−yAlyO12 (y = 0.0, 0.1, 0.2) and reduced graphene oxide (rGO) have been prepared. XRD patterns shows the presence of single phase nanocrystalline SrM and CCTO which is further supported by Raman spectroscopy and FTIR analysis. The presence of secondary phase such as α-Fe2O3, CaTiO3, and CuO has not been observed. Characteristics absorption bands of Cs-substituted SrM and Al-substituted CCTO were observed at 446, 551 and 605 cm−1, these peaks gives the idea of the formation of SrM and CCTO phase. The D and G bands of GO were observed at 1358 and 1604 cm−1 respectively, while that of the rGO were respectively observed at 1351 and 1595 cm−1. FESEM micrograph show the incorporated SrM nanoparticles, CCTO nanoparticles and rGO sheets, reduction in surface energy and magnetic dipolar interaction prompt the SrM nanoparticles to surround the CCTO nanoparticles and decorate the surface of the rGO sheets. The non-magnetic CCTO phase in the nanocomposites causes the tuning of the magnetic properties. The band gap obtained from UV–vis NIR spectroscopy is within the range of UV-blue LED application. The sample SCR3 shows a maximum reflection loss of − 16.0 dB at 18.0 GHz and matching thickness of 2 mm. The obtained reflection loss is attributed to multiple absorption mechanism as a result of improved impedance matching between the dielectric and magnetic loss absorbents.

Herein, a magnetically separable reduced graphene oxide (rGO)-supported CoFe2O4–TiO2 photocatalyst was developed by a simple ultrasound-assisted wet impregnation method for efficient photocatalytic H2 production. Integration of CoFe2O4 with TiO2 induced the formation of Ti3+ sites that remarkably reduced the optical band gap of TiO2 to 2.80 eV from 3.20 eV. Moreover, the addition of rGO improved the charge carrier separation by forming Ti–C bonds. Importantly, the CoFe2O4–TiO2/rGO photocatalyst demonstrated significantly enhanced photocatalytic H2 production compared to that from its individual counterparts such as TiO2 and CoFe2O4–TiO2, respectably. A maximum H2 production rate of 76 559 μmol g–1 h–1 was achieved with a 20 wt % CoFe2O4- and 1 wt % rGO-loaded TiO2 photocatalyst, which was approximately 14-fold enhancement when compared with the bare TiO2. An apparent quantum yield of 12.97% at 400 nm was observed for the CoFe2O4–TiO2/rGO photocatalyst under optimized reaction conditions. This remarkable enhancement can be attributed to synergistically improved charge carrier separation through Ti3+ sites and rGO support, viz., Ti–C bonds. The recyclability of the photocatalyst was ascertained over four consecutive cycles, indicating the stability of the photocatalyst. In addition, it is worth mentioning that the photocatalyst could be easily separated after the reaction using a simple magnet. Thus, we believe that this study may open a new way to prepare low-cost, noble-metal-free magnetic materials with TiO2 for sustainable photocatalytic H2 production.

In this research, we investigated the influence of Al-Mn substitution on the structural, dielectric and magnetic properties of M-type strontium hexagonal ferrites nanoparticles with chemical composition Sr1-xAlxFe11.4Mn0.6O19 (x=0.0, 0.1, 0.2), prepared by sol-gel auto-combustion technique and sintered at 950°C for 5 hours. XRD patterns show the formation of crystalline M-type hexagonal ferrites with traces of α -Fe2O3. FTIR gives the idea of the formation of M-type hexagonal ferrites by showing the presence of characteristics peaks at 438.94 cm-1 and 600.17 cm-1. FESEM shows that the sample exhibit platelet-like structure. The dielectric analysis was carried out in the frequency range 1 KHz to 5 MHz and explained on the basis of Koop’s phenomenological theory and Maxwell Wagner theory. The sample without doping exhibits the highest dielectric constant (1410). Low dielectric loss (0.829) was observed in the sample with x=0.1. The magnetic parameters such as coercivity, remnant and saturation magnetization increases with increase in Al-Mn concentration. High value of coercivity (Hc) (4597.58 Oe) was observed in the sample with x=0.2. The material may be useful for high frequency application.

The motion of a system consisting of three coupled oscillators of three masses attached together by four springs is studied analytically. The system is used as a model to describe the interactions between atoms in a one dimensional crystal with spring-like forces under white noise excitations. Two different cases are considered and the frequencies of oscillations are obtained as well as the equations of motion. The equations of motions are used to determine the power flow in the systems. The power flow determined is used to describe the effects of substitution impurities in a crystal. The power flow of the two systems studied decreases exponentially with increase in frequency to an asymptotic value.

In this article we will derive the basic equations of motion for viscous flows. It is worth noting that there are two main physical principles involved: (i) conservation of mass and (ii) Newton's second law of motion, the latter leading to a system of equations expressing the balance of momentum. In addition, we will utilize Newton's law of viscosity in the guise of what will be termed a “constitute relation” and, of course, all this will be done within the confines of the continuum hypothesis. We should also note that Newton's second law of motion is formally applied to point masses, i.e., discrete particles, its application to fluid flow seems difficult at best. But we will see that because we can define fluid particles (via the continuum hypothesis), the difficulties are not actually so great. We will begin with a brief discussion of the two types of reference frame widely used in the study of fluid motion, and provide a mathematical operator that relates them. We then review some additional mathematical constructs that will be needed in subsequent derivations. Once this groundwork has been laid, we will derive the “continuity equation” which expresses the law of conservation of mass for a moving fluid, and we will consider some of its practical consequences. We then provide a similar analysis leading to the momentum equations, thus arriving at the complete set of equations known as the Navier–Stokes (NS) equations. These equations are believed to represent all the fluid motion within the confines of the continuum hypothesis. There are many ways to derive the equation of motion of a fluid; we can use the approach which requires solving a set of partial differential equations. There is another way, called the control volume approach, and in any case, Newton's second law is applied.

Reduced graphene oxide supported CuFe2O4-TiO2 p-n heterojunction nanocomposite was prepared via ultrasound assisted simple wet impregnation method. The nanocomposites were characterized, by XRD, FTIR, Raman Spectra, FE-SEM, HR-TEM, UV- vis, DRS Spectra, and PL Spectra. The optical band gap of rGO/CuFe2O4-TiO2 nanocomposite was found to be red shifted to 1.51 eV from 3.20 eV for pristine TiO2 nanoparticles (NPs). The photocatalytic activity of the as-prepared rGO/CuFe2O4-TiO2 nanocomposite was determined via photocatalytic water-splitting in the presence of glycerol as hole scavenger under UV–vis light irradiation. A peak hydrogen production rate of 35981 μmolg−1 h−1 was obtained, which is ∼8 and 3 times higher than that of bare TiO2 (4640 μmolg−1 h−1) and CuFe2O4-TiO2 photocatalysts (14719 μmolg−1 h−1), respectively. This remarkable improvement in the photocatalytic activity can be attributed to the enhanced visible light absorption and efficient charge carrier separation at the interface of rGO/CuFe2O4-TiO2 nanocomposites. A significant quenching of photoluminescence intensity of the rGO/CuFe2O4-TiO2 nanocomposite further confirmed the effective separation and transportation of photogenerated charge carriers in the presence of rGO sheet. A double charge separation and transportation mechanism is proposed for the enhanced photocatalytic activity.

A UV and visible light responsive binary phase TiO2 coupled NiTiO3 nanocomposites were prepared by a facile co-precipitation method followed by calcination at elevated temperatures. The phase structure, morphology and optical properties of the nanocomposite were characterized by XRD, FE-SEM, HRTEM, UV–vis DRS, EIS and Raman spectra. XRD and Raman spectrum shows that between 650 °C and 850 °C, a phase transition takes place. FE-SEM and TEM analysis revealed that during the synthesis, growth of cylindrical shaped amorphous NiTiO3 took place and upon calcinations; it transforms into highly crystalline interlinked chain type morphology. A noticeable three distinct optical transitions corresponding to 3.1, 2.5 and 2.27 eV were observed by UV–vis diffuse reflection spectroscopy (DRS). The TiO2/NiTiO3 nanocomposite was used for Tetracycline and RhB photodegradation, and photocatalytic water splitting activity under UV–vis light irradiation. The results of this study showed that the nanocomposites calcined at 750 °C exhibit significantly higher photocatalytic degradation and water splitting activity. Based on the experimental results, an n-n heterojunction charge carrier transfer and separation mechanism is proposed.

Reduced graphene oxide (rGO) supported g-C3N4-TiO2 ternary hybrid layered photocatalyst was prepared via ultrasound assisted simple wet impregnation method with different mass ratios of g-C3N4 to TiO2. The synthesized composite was investigated by various characterization techniques, such as XRD, FTIR, Raman Spectra, FE-SEM, HR-TEM, UV vis DRS Spectra, XPS Spectra and PL Spectra. The optical band gap of g-C3N4-TiO2/rGO nanocomposite was found to be red shifted to 2.56 eV from 2.70 eV for bare g-C3N4. It was found that g-C3N4 and TiO2 in a mass ratio of 70:30 in the g-C3N4-TiO2/rGO nanocomposite, exhibits the highest hydrogen production activity of 23,143 μmol g−1h−1 through photocatalytic water splitting. The observed hydrogen production rate from glycerol-water mixture using g-C3N4-TiO2/rGO was found to be 78 and 2.5 times higher than g-C3N4 (296 μmol g−1 h−1) and TiO2 (11,954 μmol g−1 h−1), respectively. A direct contact between TiO2 and rGO in the g-C3N4-TiO2/rGO nanocomposite produces an additional 10,500 μmol g−1h−1 of hydrogen in 4 h of photocatalytic reaction than the direct contact between g-C3N4 and rGO. The enhanced photocatalytic hydrogen production activity of the resultant nanocomposite can be ascribed to the increased visible light absorption and an effective separation of photogenerated electron-hole pairs at the interface of g-C3N4-TiO2/rGO nanocomposite. The effective separation and transportation of photogenerated charge carriers in the presence of rGO sheet was further confirmed by a significant quenching of photoluminescence intensity of the g-C3N4-TiO2/rGO nanocomposite. The photocatalytic hydrogen production rate reported in this work is significantly higher than the previously reported work on g-C3N4 and TiO2 based photocatalysts.

α-Fe2O3/Cu2O mixed oxide photocatalysts were prepared by one step facile hydrothermal method. During the synthesis, the growth of phase pure and highly crystalline polyhedral Cu2O crystals occurred and simultaneously a heterojunction formed between α-Fe2O3 and Cu2O particles. The optical band gap of bare Cu2O was found to be 1.8 eV which was less than the reported values and incorporation of 5 wt% α-Fe2O3 further reduced the band gap of Cu2O to 1.75 eV, indicating an enhanced absorption of visible light by the binary photocatalysts. More importantly, the loading of α-Fe2O3 on Cu2O augmented the charge carriers separation and transfer at the interface, which was evident by the reduced photoluminescence intensity of α-Fe2O3/Cu2O photocatalysts. The influence of different loading amounts of iron oxide (1–10 wt%) on Cu2O was evaluated. Among them, 5 wt% α-Fe2O3 loaded Cu2O showed the enhanced photodegradation activity due to the formation of an effective p-n heterojunction and exhibited nearly 30% and 95% increase in the photodegradation rate of methyl orange (MO) compare to bare Cu2O and α-Fe2O3, respectively. The photo generated superoxide radicals were found to be the main reactive species responsible for the degradation of MO. The excellent photodegradation activity of α-Fe2O3/Cu2O photocatalyst is mainly attributed to the enhanced visible light absorption, efficient charge carriers separation and transfer. Based on the experimental results, a double charge transfer mechanism was proposed for the separation and transfer of photogenerated charge carriers in the photocatalysts.

Graphitic carbon nitride, a 2 D layered photocatalyst coupled with transition metal oxides often shows promising photocatalytic hydrogen evolution activity. However, low surface area and poor charge separation greatly hinder its photocatalytic efficiency. A Ni

This research investigates the effect of Pr3+–Co2+ substitution on the structural, optical, and electromagnetic interferrence (EMI) shielding properties of M-type strontium hexagonal ferrites with chemical composition Sr1−xPrxFe12−yCoyO19 (x = 0.0, 0.2, 0.4 and y = 0.00, 0.15, 0.35). The sample was prepared by sol–gel auto-combustion technique, pre-sintered at 400 °C for 4 h and sintered at 950 °C for 5 h. XRD analysis shows that the sample exhibits pure crystalline phase with no presence of impurity such as α-Fe2O3. The presence of three prominent peaks at 434, 543, and 586 cm−1 in FTIR spectra indicates the formation of hexaferrite phase. FESEM micrographs depict nanoparticles with hexagonal plate-like structure of hexaferrites which is vital for microwaves absorption, whereas EDX spectra show the host and substituted ions. The observed band gap was found to decrease with increase in Pr3+–Co2+ concentration. The maximum EMI shielding effectiveness of 27.40 dB at 18 GHz was obtained for the sample S2 which is above the commercial level of 20 dB.

The low surface area and photogenerated charge carrier recombination rate severely affects the usability of a photocatalysts. In this work, a visible light active AgI/BiVO4 photocatalyst was fabricated via a low temperature one step hydrothermal method. Low temperature preparation results in a porous and very high surface area (114 m2/g) BiVO4 photocatalysts. XRD, FTIR, Raman and BET surface area analysis revealed that AgI is bonded as well as embedded in the porous structure of BiVO4, which causes shrinking of the BiVO4 lattice. Compare to bare BiVO4, the AgI/BiVO4 photocatalyst shows nearly 1.7 times higher photocurrent response and 43% higher photocatalytic activity. The significantly high photocatalytic activity ascribed to the very high surface area, and the effective charge separation at the AgI/BiVO4 p-n heterojunction. Further, based on UV-DRS and Mott-Schottky measurements, a plausible charge transfer mechanism is proposed.

In this article, we considered the dependence of the rate of energy transition on various parameters and how the energy-transition -rate changes as a function of radius R. We observed that with increasing radius R, the energy-flip-rate decreases, which is perfectly consistent with a system approaching ferromagnetic order. Also the energy-transition-rate for different choices of the amplitude of the impurities, for a purely static potential scatter, no energy transition occurs, but for magnetic impurities, we observed a high peak in the energy-transition-rate for one particular amplitude of order 5  . Different profiles of energy-transition-rate (ETR) against frequencies and amplitude are drawn respectively, for angle , θ , with µBB0=0.5 and     x = R2 = 100 and different values of frequencies and amplitude.

In this analytical approach we fabricate and characterized a Titanium Dioxide Dye sensitized solar cell using Doctor-Blade Technique. The samples were given annealing treatment at various time of 20, 30 and 40 minutes respectivelyat constant annealing temperature of 450oC. The device under test (DUT) were tested using a Kiethley 2400, source meter under A.M 1.5 (1000W/m2) illumination from a Newport class A solar simulator.The results shows that at the miscellaneous annealing time, the open circuit voltagesVoc= 0.28V, 0.30V and 0.29V, the short circuit current density Jsc=95.5µAcm-2 , 104.1µAcm-2and 105µAcm-2, the fill factor FF= 0.411, 0.448 and 0.525 and the energy conversion efficiency, η = 0.011, 0.014 and 0.016 respectively.With best results of open circuit voltage Voc=0.30, short circuit current density Jsc= 105mAcm-2, fill factor FF= 0.525 and energy conversion efficiency η= 0.016 was achieved.It was observed that the power density, Fill Factor and efficiency increases with increasewith increase in annealing time.

Sol-gel autocombustion technique was used to synthesized composites of barium hexaferrites (BaM) and calcium copper titanate (CCTO) with chemical composition Ba1−xCoxFe12−x−yDyxLayO19 (x = 0.0, 0.1, 0.2, 0.3 and y = 0.0, 0.4, 0.5, 0.6) and Ca1-xErxCu3Ti4−yMnyO12 (x = 0.0, 0.1, 0.2, 0.3 and y = 0.0, 0.4, 0.5, 0.6) respectively. The BaM/CCTO composites exhibit a single crystalline phases of both BaM and CCTO, this observation is supported by Raman spectroscopy. Characteristics peaks of both BaM and CCTO were observed at 439 and 592 cm−1; these peaks give a hint on the formation of both BaM and CCTO phase in the composites. Morphology analysis show that the grains of the BaM nanoparticles exhibit uneven distribution with morphology close to hexagonal structure while the CCTO microparticles shows cubic-like grains with homogenous distribution and the stoichiometry of the prepared composites was also observed. Lattice fringes of BaM nanoparticles and CCTO microparticles with sizes of 0.2629 and 0.2613 nm corresponding to (1 1 4) and (2 2 0) hkl planes respectively have been observed. The observed band-gap increases with increase in crystallite size. The coercivity increases as a result of the presence of CCTO phase. BaMCCTO4 composite shows maximum reflection loss (RL) of −27.9 dB (99.83% absorption) at 16.5 GHz and matching thickness of 3 mm with effective absorption (RL 20 dB) bandwidth of 4.2 GHz. Keywords: Permittivity, Permeability, Reflection loss, Shielding effectiveness, Band gap

Sr0.7Al0.3Fe11.4Mn0.6O19 was synthesized by sol-gel technique and sintered at varying temperatures 750 °C, 850 °C, 950 °C and 1050 °C for 5 hours. We investigate the role of heat-treatment on the structural, magnetic and optical properties of Al-Mn doped strontium hexaferrite. XRD analysis indicates the formation of M-type hexaferrites with some traces of α-Fe2O3. The presence of two prominent peaks between 400 cm-1 and 600 cm-1 in the spectra of FTIR gives the possibility of the emergence of M-type hexagonal ferrites. FESEM micrograph shows that the grains of the prepared sample possess Plate-like hexagonal structure. EDX spectra confirmed the stoichiometry of the prepared sample. Recrystallization of the synthesized sample and formation temperature of 650 °C is observed in TGA analysis. Variation of the sintering temperature results in decrease of the band gap. Magnetic parameters were calculated from the M-H loop obtained from vibrating sample magnetometer (VSM). High value of coercivity (6750 Oe) is observed at 850 °C. Remanent and saturation magnetization decreases with increase heat-treatment temperature. The synthesized sample may be useful in perpendicular recording medium (PRM) and high frequency application.

An organic solar cell device or organic photovoltaic cell (OPV) is a class of solar cell that uses conductive organic polymers or small organic molecules for light absorption and charge transport. In this study, we fabricate and characterize an organic photovoltaic cell device and estimated important parameters of the device such as Open Circuit Voltage Voc of 0.28V, Short-Circuit Current Isc of 4.0 × 10-5 A, Maximum Power Pmax of 2.4 × 10-6 W, Fill Factor of 0.214 and the energy conversion efficiency of η=0.00239% were tested using Keithley 2400,source meter under A.M 1.5 (1000/m2) illumination from a Newport Class A solar simulator. Also the I-V characteristics for OPV were drawn.

In this article, the behavior of a half spin particle is studied. Specifically an electron with mass me, when passing through a magnetic field with fixed strength Bo is examined. A magnetic impurity is considered as a scatterer of a half spin particle in one dimension. This corresponds for example to a defect in the local magnetic structure inducing a magnetic field, e.g. as a result of strong spin-orbit coupling. From this set-up, the spin-flipping scattering processes are observed. Different profiles of Spin-Flip-Rate (SFR) against frequencies ω and amplitudes U are drawn respectively, for angle φ0=0, θ = π 2 and different values of, μBB0, and radius R.

Water is necessity to human and other life, human uses water for drinking, agricultural activities, domestic activities and so on. Therefore, it become necessary to study the level of radiation in our drinking water, because it poses many biological risks to human and other life when exceeded the maximum contamination level. This study examined the level of radioactivity of drinking water collected from local hand-dug wells and boreholes in Dutse town of Jigawa State. A total of 24 samples were collected and analyzed using MPC-2000, a Low Background alpha and beta counter. The equipment is a gasless proportional counter with ultra-thin window. The results showed that the alpha activity ranges from 0.006 to 0.485 Bq/l with a geometric mean of 0.060 Bq/l for borehole water samples and 0.003 to 1.08 Bq/l with a geometric mean of 0.094 Bq/l for well water samples and that of beta activity ranges from 0.009 to 84.68 Bq/l with a geometric mean of 5.288 Bq/l for borehole water samples and 6.830 to 6284.50 Bq/l with a geometric mean of 29.70 Bq/l for well water samples. Most of the sampling areas were above the maximum recommended level set by World Health Organization (WHO) of 0.5 Bq/l for alpha and 1.0 Bq/l for beta and United State Environmental Protection Agency (USEPA) of 0.55 Bq/l for alpha and 1.85 Bq/l for beta activity. An attempt has been done to examine the correlation between the alpha and beta activity and a very poor correlation was obtained. It was further observed that well water samples recorded higher activity compared to borehole water samples. The lower activity in the borehole water samples may be due to the absorption of the activity in the pipes unlike the well water samples that was drawn directly from it source. The overall results showed that many of the sampling areas are not suitable for drinking, agriculture and other domestic activities. It is therefore, recommended that more studies should be carried out to ensure the safety of the general public in these locations.