Influence of Thermal Treatment on Kankara Kaolinite

In this work, the influence of thermal treatment on the structure of Kankara kaolinite was studied for the first time, using X-ray diffractogram (XRD), EDX, NanoSEM, FTIR-Attenuated Total Reflectance, DTA/TGA and BET surface area measurements. The treatment temperatures applied represents the peak of the transformation stages. The results show that surface area decreases with increase in temperature of treatment, while its crystal structure was transformed from the native kaolinite structure via the amorphous metakaolin to the typical mullite/crystobalite structure though with some unidentifiable peaks. The morphological studies showed that Kankara kaolinite is composed of nano-platelets of about 30nm thickness and in bundles of between 1 – 3 µm thicknesses with some marked variations/reductions as the treatment temperatures increases. The DTA/TGA result shows that the kaolinite undergoes dehydroxylation at 528.560C while been converted to metakaolin with a weight loss of about 14.4%. The presence of the characteristic OH, Al-OH, Si-OH and Si-O-Al bands were confirmed with the ATR studies which also showed the disappearance and subsequent appearance of new bands as the treatment temperature increased, this also affected the surface area and pore sizes of the transformation products

Self-Healing Nanocomposites—Advancements and Aerospace Applications

Self-healing polymers and nanocomposites form an important class of responsive materials. These materials have the capability to reversibly heal their damage. For aerospace applications, thermosets and thermoplastic polymers have been reinforced with nanocarbon nanoparticles for self-healing of structural damage. This review comprehends the use of self-healing nanocomposites in the aerospace sector. The self-healing behavior of the nanocomposites depends on factors such as microphase separation, matrix–nanofiller interactions and inter-diffusion of polymer–nanofiller. Moreover, self-healing can be achieved through healing agents such as nanocapsules and nanocarbon nanoparticles. The mechanism of self-healing has been found to operate via physical or chemical interactions. Self-healing nanocomposites have been used to design structural components, panels, laminates, membranes, coatings, etc., to recover the damage to space materials. Future research must emphasize the design of new high-performance self-healing polymeric nanocomposites for aerospace structures

Structural, optical and electrical properties of electron beam evaporated TiOxNy films as selective solar absorber coatings

Titanium oxinitride (TiOxNy) solar absorber coatings were deposited at different oxygen partial pressures onto Cu, Si and glass substrates using electron beam evaporation technique. XRD diffraction patterns evidenced (111), (200) and (220) orientation of TiNx phase. The preferred orientation of the films changed with oxygen partial pressure. XPS revealed the intensity of both Ti 2P3/2 and Ti 2P1/2 increases as a function of oxygen flow, and also shifted towards higher binding energy, indicating more oxidized state of Ti species than that of TiO2 due to incorporation of nitrogen atoms. Formation of uniformly distributed spherical like particles and an increase in surface roughness of the TiOxNy films were observed as a function of oxygen partial pressure as depicted from SEM and AFM, respectively. Ellipsometric and resistivity measurements showed a shift from metallic to semiconductor behaviour of the TiOxNy films as oxygen flow changed. A solar absorptance value of 0.94 in the solar spectrum region and a low thermal emittance value of 0.05 were achieved for the TiOxNy solar absorber coatings prepared at the oxygen partial pressure of 7.5x10-5 Torr due to both interference and intrinsic absorption. This study confirmed that a single layer of TiOxNy film can be a good candidate as selective solar absorber

Cutting-Edge Green Polymer/Nanocarbon Nanocomposite for Supercapacitor—State-of-the-Art

Supercapacitors have attained a special stance among energy storage devices such as capacitors, batteries, fuel cell, and so forth. In this state-of-the-art overview on green synthesis approaches and green materials for supercapacitors, the cutting-edge green polymer/nanocarbon nanocomposite systems were explored by focusing on the design and related essential features. In this regard, various polymers were reconnoitered including conjugated polymers, thermosetting matrices, and green-cellulose-based matrices. Nanocarbon nanomaterials have also expanded research thoughtfulness for green-technology-based energy storage devices. Consequently, green polymer/nanocarbon nanocomposites have publicized fine electron conduction pathways to promote the charge storage, specific capacitance, energy density, and other essential features of supercapacitors. Future research directions must focus on the design of novel high performance green nanocomposites for energy storage applications

Polymer/Fullerene Nanocomposite for Optoelectronics—Moving toward Green Technology

Optoelectronic devices have been developed using the polymer/fullerene nanocomposite, as focused in this review. The polymer/fullerene nanocomposite shows significant structural, electronics, optical, and useful physical properties in optoelectronics. Non-conducting and conducting polymeric nanocomposites have been applied in optoelectronics, such as light-emitting diodes, solar cells, and sensors. Inclusion of fullerene has further broadened the methodological application of the polymer/fullerene nanocomposite. The polymeric matrices and fullerene may have covalent or physical interactions for charge or electron transportation and superior optical features. Green systems have also been explored in optoelectronic devices; however, due to limited efforts, further design innovations are desirable in green optoelectronics. Nevertheless, the advantages and challenges of the green polymer/fullerene nanocomposite in optoelectronic devices yet need to be explored

Radiation hazard in soil from Ajaokuta North-central Nigeria

Background: Measurement of the radia�on dose distribu�on is important in assessing the health risk a popula�on and serve as reference in documen�ng changes to environmental radioac�vity in soil due to man-made ac�vi�es. Materials and Methods: The ac�vity concentra�on of 238U, 232Th and 40K in soil samples obtained from different loca�ons in Ajaokuta Local Government area was measured using Hyper Pure germanium Detec�on System (HPGe). Results: The calculated average concentra�on of the radionuclides ranged from 12 ± 1 Bqkg-1 to 59 ± 2 Bqkg-1 for 238U, 14 ± 1 Bqkg-1 to 78 ± 5 Bqkg-1 for 232Th and 49 ± 2 Bqkg-1 to 1272 ± 23 Bqkg-1 for 40K. In order to evaluate the radiological hazards due to natural radionuclides within Ajaokuta, the absorbed dose rate, gamma index, radium equivalent and excess life�me cancer risk were es�mated. According to measured data from the top soil (0-10 cm), the es�mated radium equivalent (Raeq) ranges from 55.7 Bqkg-1 at Steel Complex to 253.3 Bqkg-1 obtained from Forest samples. Conclusion: The mean absorbed dose rate, annual effec�ve dose and gamma radia�on index evaluated were 66.2 nGyh-1, 81.2 μSvy-1 and 1.05 respec�vely which are higher than the recommended limit for normal background radia�on. Thus, we conclude that people living in these loca�ons may be exposed to higher radia�on

Linear and nonlinear optical absorption characterization of natural laccaic acid dye

We report on the optical performances of laccaic acid dye in solution at different concentrations and dye–poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index (n) and extinction coefficient (k), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β eff (or β 2), the imaginary third-order susceptibility (Im[χ (3)]) and the imaginary part of second-order hyperpolarizability (γ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10−10, 10−11 and 10−32 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application

Nonlinear photonics properties of porphyrins nanocomposites and self-assembled porphyrins

Two major reasons limit porphyrins photonic applications: (i) the difficulty of handling them in liquid solutions and (ii) their degradation with long exposure to light. This necessitates the use of appropriate solid matrices to host the porphyrin compounds such as Nafion (117), a stable and inert ion exchange polymer. The first part of this publication confirms such a possibility. In addition to their effective NLO properties, an enhancement of the Soret and Q-bands absorbance width have been observed by blending three different porphyrin molecules in the Nafion column matrix membrane. This is an important development towards achieving efficient photon-harvesting medium for possible application in photonic devices. The second part of this contribution reports on the self-assembly/molecular recognition of a specific class of porphyrins giving rise to tubular nano-systems with potential THG nonlinear properties

The International Research and Educational Programs of Clark Atlanta University's Center for Functional Nanoscale Materials

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Microstructure characterization of onion (A.cepa) peels and thin films for dye sensitized solar cells

A.cepa peels are obtained from mature onion bulbs. Because of the continuous need for energy, alternative avenues for producing energy are gaining importance. The motivation for this work is based on an urgent need to source energy from readily available waste materials like domestic onion peels. Dye sensitized solar cells (DSSCs) fabricated via doctor blade method and high temperature sintering from waste (onion peels) are investigated for their ability to convert solar to electrical energy. The charge carriers were revealed under phytochemical screening. Functional groups of compounds present in A.cepa peel were analyzed with Fourier transform in infrared (FTIR). The influence of different electrolyte sensitizer is observed on the DSSCs under standard air mass conditions of 1.5 AM. The microstructure properties of these A.cepa DSSCs were explored using scanning electron microscope with energy dispersive spectroscopy (SEM/EDS), x-ray diffraction and Fluorecence spectroscopy (XRF). The interfacial boundary between A.cepa dye, TiO2 framework of TiO2 and indium doped tin oxide (ITO) reveals several prominent anatase and rutile peaks. Photoelectric results, revealed dye-sensitized solar cells with a maximum power output of 126 W and incident photon to conversion energy (IPCE) of 0.13%.This work has established that A.cepa peels can be used as a source of micro-energy generatio