Use of vermicomposting in domestic onsite sewage and biowaste management

Modern lifestyle has increased the amount of solid and liquid waste that humans create. There are issues associated with pollution and disposal. The tried and tested methods of centralised treatment have proven impractical in the long run, given the spread of human population. Moreover, such techniques are unsuitable for the developing and under-developed world due to huge infrastructure costs and lack of technology issues. Adaptation of technologies from the developed world often does not provide the required solutions. This thesis describes an attempt at finding an ecologically and economically sustainable solution for waste management that is appropriate for poorer regions and remote areas. The proposed treatment system is close to natural processes and uses biological waste processing methods that have proven to be sustainable. Available resources and low cost give an edge for such processes to be practical and realistic. The system is based on vermicomposting. Composting worms survive in the harsh environments found in most parts of developing world. A working prototype of the vermicomposting waste management system was designed to utilise the technique of vermicomposting to treat putrescible fraction of domestic solid wastes along with pathogen-rich human excrement wastes (blackwater). Tests with organic solid wastes and liquid pig manure (as a replacement for blackwater) yielded excellent results in terms of reduction in pollutant loading such as suspended solids, turbidity, Biochemical and chemical oxygen demands, faecal coliform and ammonia content. Areas for further research and process optimisation were identified that would pave way for future endeavours towards development of a fully working model. The treatment system is shown to work and achieve the objectives of treating waste to usable products including worms for feed supplement, compost fertiliser and irrigation water

Lightweight and solution processible thin sheets of poly(o-toluidine)-carbon fiber-novolac composite for EMI shielding

An attempt has been made to generate lightweight and processible thin sheets of poly (o-toluidine)-carbon fiber (PoTCF) composite for electromagnetic interference shielding. PoTCF composite synthesized by oxidative emulsion polymerization was physically blended with different weight ratios of novolac resin to prepare a new class of composite material, which was further processed to form thin sheets (thickness of similar to 0.85 mm) by a compression moulding technique. In situ incorporation of carbon fiber into the polymer matrix leads to the formation of composites with improved mechanical, thermal, electrical and shielding properties, which were further optimized by varying the amount of novolac resin in the sheets. Structural and morphological studies were carried out by UV-vis, FTIR, XRD and SEM. PoTCF composite sheets with 50 wt% loading of novolac resin have flexural strength of 36.0 MPa and exhibit a shielding effectiveness of 24 dB in the X-band (8.2-12.4 GHz) at a critical thickness of similar to 2.11 mm, which is more than the limit required for techno-commercial applications. Therefore, indigenously fabricated polymer-based sheets would be potentially useful for making durable enclosures for electronic equipment

Recent advances in MXenes: from fundamentals to applications

The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. In the last couple of years, several breakthroughs have been achieved that boosted the synthesis of novel MAX phases with ordered double transition metals and, consequently, the synthesis of novel MXenes with a higher chemical diversity and structural complexity, rarely seen in other families of two-dimensional (2D) materials. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin$-$orbit coupling, MXenes can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. In addition, owing to their large surface area, hydrophilicity, adsorption ability, and high surface reactivity, MXenes have attracted attention for many applications, e.g., catalysts, ion batteries, gas storage media, and sensors. Given the fast progress of MXene-based science and technology, it is timely to update our current knowledge on various properties and possible applications. Since many theoretical predictions remain to be experimentally proven, here we mainly emphasize the physics and chemistry that can be observed in MXenes and discuss how these properties can be tuned or used for different applications

Revelation of graphene-Au for direct write deposition and characterization

Graphene nanosheets were prepared using a modified Hummer's method, and Au-graphene nanocomposites were fabricated by in situ reduction of a gold salt. The as-produced graphene was characterized by X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM). In particular, the HR-TEM demonstrated the layered crystallites of graphene with fringe spacing of about 0.32 nm in individual sheets and the ultrafine facetted structure of about 20 to 50 nm of Au particles in graphene composite. Scanning helium ion microscopy (HIM) technique was employed to demonstrate direct write deposition on graphene by lettering with gaps down to 7 nm within the chamber of the microscope. Bare graphene and graphene-gold nanocomposites were further characterized in terms of their composition and optical and electrical properties

Development of Graphene Nanoplatelets Reinforced Shape Memory Polyurethane and Their DMA Studies

Shape memory nanocomposites have been synthesized using ether type shape memory polyurethane (SMPU) and graphene nanoplatelets (GNPs). A twin screw co-rotating microcompounder with a back flow channel has been employed to ensure proper dispersion of GNPs in the polymer matrix. Four compositions of GNPs in SMPU have been prepared. Morphology of fractured nanocomposites reveals uniform dispersion of graphene in SMPU. The dynamic-thermo-mechanical properties of nanocomposites at 0.1 and 10 Hz have been studied. Addition of 1 phr GNPs increases storage modulus of SMPU from 2.8 to 3.73 GPa and the value of tan δ peak has been decreased from 0.81 to 0.53. The GNPs in SMPU matrix influence shape recovery which improves with the addition of GNPs with in experimental range

Nanostructured La0.7Sr0.3MnO3 compounds for effective electromagnetic interference shielding in the X-band frequency range

We report a detailed study on the electromagnetic interference (EMI) shielding effectiveness (SE) properties in La0.7Sr0.3MnO3 (LSMO) nanomaterials. The samples were prepared by a solution chemistry (sol-gel) route at different sintering temperatures. The single-phase samples with grain sizes of 22 and 34 nm showed DC electrical conductivity variation from 0.65 to 13 S cm(-1) at room temperature. The application of a high magnetic field resulted in higher conductivity values. The electrical conductivity variation with temperature could be fitted with a variable range hopping mechanism in a limited temperature range. The variation of frequency dependent electromagnetic parameters measured at room temperature within the X-band region is consistent with the electrical conductivity behavior. The complex permittivity and permeability parameters were determined in line with the Nicolson-Ross-Weir algorithm. The LSMO nanomaterial samples showed EMI shielding effectiveness values of up to 19 dB (96.3% attenuation) over the X-band frequency range, making them suitable for microwave radiation shielding in commercial and defense appliances

Encapsulation of gamma-Fe2O3 decorated reduced graphene oxide in polyaniline core-shell tubes as an exceptional tracker for electromagnetic environmental pollution

The ultimate goal of the development of a new material gamma-Fe2O3 decorated reduced graphene oxide (rGO)-polyaniline (PANI) core-shell tubes has been done for absorbing electromagnetic interference (EMI) pollution. Herein, we report on the synthesis and characterization of PANI tubes consisting of rGO decorated with iron oxide nanoparticles (RF). The intercalated RF was synthesized by thermal decomposition of ferric acetyl acetonate in a reducing atmosphere. Furthermore, RF was encapsulated through oxidative polymerization of aniline in the presence of beta-naphthalene sulphonic acid which results in RF-PANI core-shell morphology. Scanning electron microscopy results confirm the formation of tubular core-shell morphology having 5-15 mu m length and 1-5 mu m diameter. The presence of rGO-gamma-Fe2O3 in PANI core enhances the interfacial polarization and the effective anisotropy energy of the composite which contributes to more scattering and leads to high shielding effectiveness (SET similar to 51 dB) at a critical thickness of 2.5 mm. Additionally, the effective complex permeability and permittivity parameters of the composites have been evaluated from the experimental scattering parameters (S-11 & S-21) using theoretical calculations given in Nicholson-Ross and Weir algorithms

Enhancing Light Harvesting by Hierarchical Functionally Graded Transparent Conducting Al-doped ZnO Nano- and Mesoarchitectures

A functionally graded Al-doped ZnO structure is presented which combines conductivity, visible transparency and light scattering with mechanical flexibility. The nano and meso-architecture, constituted by a hierarchical, large surface area, mesoporous tree-like structure evolving in a compact layer, is synthesized at room temperature and is fully compatible with plastic substrates. Light trapping capability is demonstrated by showing up to 100% improvement of light absorption of a low bandgap polymer employed as the active layer.Comment: 21 pages, 6 figures, submitted to Solar Energy Materials and Solar Cell

Facile synthesis and photoluminescence spectroscopy of 3D-triangular GaN nano prism islands

We report a strategy for fabrication of 3D triangular GaN nano prism islands (TGNPI) grown on Ga/Si(553) substrate at tow temperature by N-2(+) ions implantation using a sputtering gun technique. The annealing of Ga/Si(553) (600 degrees C) followed by nitridation (2 key) shows the formation of high quality GaN TGNPI cross-section. TGNPI morphology has been confirmed by atomic force microscopy. Furthermore, these nano prism islands exhibit prominent ultra-violet luminescence peaking at 366 nm upon 325 nm excitation wavelength along with a low intensity yellow luminescence broad peak at 545 nm which characterizes low defects density TGNPI. Furthermore, the time-resolved spectroscopy of luminescent TGNPI in nanoseconds holds promise for its futuristic application in next generation UV-based sensors as well as many portable optoelectronic devices

Synthesis and characterization of Pt/graphene-CNTs electrocatalyst for direct methanol fuel cell

Abstract In the present work we report a facile method for the synthesis of Pt nanoparticles supported reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) nanocomposite by an in-situ chemical reduction. The incorporation of MWCNTs to rGO leads to decrease in agglomeration between rGO sheets due to π -π interactions and higher loading of Pt nanoparticles. In this process, a mixture of exfoliated graphene oxide, CNTs and chloroplatinic acid was treated with a mixture of hydrazine hydrate and ammonium hydroxide at 95° C in an oil bath for 1 h. Pt nanoparticles of 4-6 nm size were homogeneously dispersed on rGO-CNTs nanocomposite as revealed by TEM analysis. Cyclic voltammetry measurements depict an anodic current density of 11.74 mA/cm 2 that could be obtained using Pt/rGO-CNTs catalyst and 6.2 mA/cm 2 using Pt/rGO catalyst during methanol oxidation, indicating that the catalytic activity of Pt/rGO-CNTs catalyst is almost 2 times higher than that of Pt/rGO catalyst. The electrochemical stability of Pt/rGO-CNTs catalyst was also found to be much higher as compared with that of Pt/rGO catalyst. Thus, Pt/rGO-CNTs catalyst has the potential to be used in the preparation of a promising anode material for direct methanol fuel cell