Central Metallurgical Research and Development Institute

In the present era of scarcity of water resources, effective treatment of wastewater is a major prerequisite for growing economy. It is critical to develop and implement advanced wastewater treatment technologies with high efficiency and low capital requirement. Among various treatments, recent advanced processes in nano-material sciences have been attracting the attention of scientists. However, limited collective knowledge is available in this context. The present manuscript reviews the potential developments in nanotechnology with respect to wastewater treatment. The article reviewed and discussed utilization of various classes of nano-materials for wastewater treatment processes. This includes four main classes; First, nano-adsorbents such as activated carbon, carbon nanotubes, grapheme, manganese oxide, zinc oxide, titanium oxide, magnesium oxide and ferric oxides that are usually applied for removal of heavy metals from the wastewater. Second, nano-catalysts such as photocatalyst, electrocatalyst, Fenton based catalyst, and chemical oxidant have been shown the potential for removing both organic and inorganic contaminants. Third, nano-membranes have been used for effective removal of dyes, heavy metals and foulants using carbon nanotube membranes, electrospun nanofibers and hybrid nano-membranes. Finally, the integration of nanotechnology with biological processes such as algal membrane bioreactor, anaerobic digestion and microbial fuel cell is discussed with respect to its potential for wastewater purification. Keywords: Nano-adsorbents, Nano-catalysts, Nano-membranes, Biomaterials, Wastewater, Treatment

Abstract Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g −1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe 2 O 4 , MMoO 4 and MCo 2 O 4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo 2 S 4 , display a high specific capacitance of 1269 F g −1 , which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g −1 . This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

The Williamson-Hall (W-H) equation, which has been used to obtain relative crystallite sizes and strains between samples since 1962, is revisited. A modified W-H equation is derived which takes into account the Scherrer equation, first published in 1918, (which traditionally gives more absolute crystallite size prediction) and strain prediction from Raman spectra. It is found that W-H crystallite sizes are on average 2.11 ± 0.01 times smaller than the sizes from Scherrer equation. Furthermore the strain from the W-H plots when compared to strain obtained from Raman spectral red-shifts yield factors whose values depend on the phases in the materials – whether anatase, rutile or brookite. Two main phases are identified in the annealing temperatures (350 °C–700 °C) chosen herein – anatase and brookite. A transition temperature of 550 °C has been found for nano-TiO2 to irreversibly transform from brookite to anatase by plotting the Raman peak shifts against the annealing temperatures. The W-H underestimation on the strain in the brookite phase gives W-H/Raman factor of 3.10 ± 0.05 whereas for the anatase phase, one gets 2.46 ± 0.03. The new βtot2cos2θ-sinθ plot and when fitted with a polynomial yield less strain but much better matching with experimental TEM crystallite sizes and the agglomerates than both the traditional Williamson-Hall and the Scherrer methods. There is greater improvement in the model when linearized – that is the βtotcos2θ-sinθ plot rather than the βtot2cos2θ-sinθ plot.

Titanium dioxide is a very important semiconductor with a high potential for applications in photocatalysis, solar cells, photochromism, sensoring, and various other areas of nanotechnology. Increasing attention has recently been focused on the simultaneous achievement of high bulk crystallinity and the formation of ordered mesoporous TiO2 frameworks with high thermal stability. Mesoporous TiO2 has continued to be highly active in photocatalytic applications because it is beneficial for promoting the diffusion of reactants and products, as well as for enhancing the photocatalytic activity by facilitating access to the reactive sites on the surface of photocatalyst. This steady progress has demonstrated that mesoporous TiO2 nanoparticles are playing and will continue to play an important role in the protection of the environment and in the search for renewable and clean energy technologies. This review focuses on the preparation and characterisation of mesoporous titania, noble metals nanoparticles, transition metal ions, non-metal/doped mesoporous titania networks. The photocatalytic activity of mesoporous titania materials upon visible and UV illumination will be reviewed, summarized and discussed, in particular, concerning the influence of preparation and solid-state properties of the materials. Reaction mechanisms that are being discussed to explain these effects will be presented and critically evaluated.

Pyrolysis based biorefineries have great potential to convert wastes such as plastic and biomass waste into energy and other valuable products to achieve maximum economic and environmental benefits. In this study, the catalytic pyrolysis of different types of plastics waste (PS, PE, PP, and PET) as single or mixed in different ratios in the presence of modified natural zeolite (NZ) catalysts in a small pilot scale pyrolysis reactor was carried out. The NZ was modified by thermal activation (TA-NZ) at 550°C and acid activation (AA-NZ) with HNO3 to enhance its catalytic properties. The catalytic pyrolysis of PS produced the highest liquid oil (70 and 60%) than PP (40 and 54%) and PE (40 and 42%) using TA-NZ and AA-NZ catalysts respectively. The gas chromatography-mass spectrometry (GC-MS) analysis of oil showed a mixture of aromatics, aliphatic and other hydrocarbon compounds. The TA-NZ and AA-NZ catalysts showed a different effect on the wt.% of catalytic pyrolysis products and liquid oil chemical composition, with AA-NZ showing higher catalytic activity than TA-NZ. FT-IR results showed clear peaks of aromatic compounds in all liquid oil samples with some peaks of alkanes that further confirmed the GC-MS results. The liquid oil has higher heating values (HHV) range of 41.7-44.2 MJ/kg, close to conventional diesel. Therefore, it has the potential to be used as an alternative source of energy and as transportation fuel after refining/ blending with conventional fuels.

Multifunctional dual-compartment Janus mesoporous silica nanocomposites of UCNP@SiO2@mSiO2&PMO (UCNP = upconversion nanoparticle, PMO = periodic mesoporous organosilica) containing core@shell@shell structured UCNP@SiO2@mSiO2 nanospheres and PMO single-crystal nanocubes have been successfully synthesized via a novel anisotropic island nucleation and growth approach with the ordered mesostructure. The asymmetric Janus nanocomposites show a very uniform size of ~300 nm and high surface area of ~1290 m(2)/g. Most importantly, the Janus nanocomposites possess the unique dual independent mesopores with different pore sizes (2.1 nm and 3.5-5.5 nm) and hydrophobicity/hydrophilicity for loading of multiple guests. The distinct chemical properties of the silica sources and the different mesostructures of the dual-compartments are the necessary prerequisites for the formation of the Janus nanostructure. With the assistance of the near-infrared (NIR) to ultraviolet/visible (UV-vis) optical properties of UCNPs and heat-sensitive phase change materials, the dual-compartment Janus mesoporous silica nanocomposites can be further applied into nanobiomedicine for heat and NIR light bimodal-triggered dual-drugs controllable release. It realizes significantly higher efficiency for cancer cell killing (more than 50%) compared to that of the single-triggered drugs delivery system (~25%).

With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in catalysis, energy storage, sensing, and biomedicine are presented.

Oxidative stress and a series of excessive inflammatory responses are major obstacles for neurological functional recovery after ischemic stroke. Effective noninvasive anti-inflammatory therapies are urgently needed. However, unsatisfactory therapeutic efficacy of current drugs and inadequate drug delivery to the damaged brain are major problems. Nanozymes with robust anti-inflammatory and antioxidative stress properties possess therapeutic possibility for ischemic stroke. However, insufficiency of nanozyme accumulation in the ischemic brain by noninvasive administration hindered their application. Herein, we report a neutrophil-like cell-membrane-coated mesoporous Prussian blue nanozyme (MPBzyme@NCM) to realize noninvasive active-targeting therapy for ischemic stroke by improving the delivery of a nanozyme to the damaged brain based on the innate connection between inflamed brain microvascular endothelial cells and neutrophils after stroke. The long-term in vivo therapeutic efficacy of MPBzyme@NCM for ischemic stroke was illustrated in detail after being delivered into the damaged brain and uptake by microglia. Moreover, the detailed mechanism of ischemic stroke therapy via MPBzyme@NCM uptake by microglia was further studied, including microglia polarization toward M2, reduced recruitment of neutrophils, decreased apoptosis of neurons, and proliferation of neural stem cells, neuronal precursors, and neurons. This strategy may provide an applicative perspective for nanozyme therapy in brain diseases.

Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.

In this work, we have successfully developed a novel multifunctional near-infrared (NIR)-stimulus controlled drug release system based on gold nanocages as photothermal cores, mesoporous silica shells as supporters to increase the anticancer drug loading and thermally responsive poly(N-isopropylacrylamide) (PNIPAM) as NIR-stimuli gatekeepers (Au-nanocage@mSiO2@ PNIPAM). The unique Au-nanocage@mSiO2 nanocarrier was elaborately fabricated by utilizing yolk-shell Ag-nanocube@mSiO2 nanostructure as a template by means of spatially confined galvanic replacement. The Au nanocage cores can effectively absorb and convert light to heat upon irradiation with a NIR laser, resulting in the collapse of the PNIPAM shell covering the exterior of mesoporous silica, and exposes the pores of mesoporous silica shell, realizing the triggered release of entrapped DOX drugs. The in vitro studies have clearly demonstrated the feasibility and advantage of the novel nanocarriers for remote-controlled drug release systems.

Since first introduced by Zwilling and co-workers in 1999, titania nanotube arrays (TNTAs) fabricated by simple electrochemical anodization method have attracted great interest due to their outstanding photoelectrochemical properties which render them the most promising candidate for many solar energy harvesting applications. In this contribution, the fabrication, properties, and applications of TiO2 nanotube arrays have been reviewed, with special focus on synthesis by anodization in fluoride-containing electrolytes. The effect of anodization process parameters such as electric potential, pH, anodization duration and electrolyte composition on the size, and morphology of TNTAs has been discussed in detail. Electronic property modification strategies of the wide band gap TNTAs to enhance the material responsiveness to visible light irradiation have also been reviewed. Modification strategies include nonmetal doping such as nitrogen, carbon, boron and sulfur; metal ion doping such as Fe, Zn, Zr and Cr; surface decoration with precious metal nanoparticles such as Pt, Ag, Au; and sensitization with CdS nanoparticles.

Carbon based or containing refractories has been attracting great attention because of their unique properties e.g. high thermal conductivity, low thermal expansion, high resistance to thermal shock and chemical inertness to the slag. They are classified into two groups; carbon/bricks/blocks and carbon containing materials. Carbon containing materials are further classified into carbon containing basic refractories and non-basic refractories. Manufacturing processes are considered. The properties e.g. physical, thermal, mechanical and chemical are reviewed. Antioxidant and bonding materials for these types of the refractory products are reviewed. Their applications are also considered.

Graphene-based nanocomposites possess excellent mechanical, electrical, thermal, optical, and chemical properties. These materials have potential applications in high-performance transistors, biomedical systems, sensors, and solar cells. This paper presents a critical review of the recent developments in graphene-based nanocomposite research, exploring synthesis methods, characterizations, mechanical properties, and thermal properties. Emphasis is placed on characterization techniques and mechanical properties with detailed examples from recent literature. The importance of characterization techniques including Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) for the characterization of graphene flakes and their composites were thoroughly discussed. Finally, the effect of graphene even at very low loadings on the mechanical properties of the composite matrix was extensively reviewed.

Toxicity and chemical instability issues of halide perovskites based on organic–inorganic lead-containing materials still remain as the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with nontoxic Cu metal for lead-free PSCs, and investigate their potential toward solar cell applications based on experimental and theoretical studies. The formation of (CH3NH3)2CuX4 [(CH3NH3)2CuCl4, (CH3NH3)2CuCl2I2, and (CH3NH3)2CuCl2Br2] was discussed in details. Furthermore, it was found that chlorine (Cl–) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials showed attractive absorbance features extended to the near-infrared range, with appropriate band gaps. Green photoluminescence of these materials was obtained because of Cu+ ions. The power conversion efficiency was measured experimentally and estimated theoretically for different architectures of solar cell devices.

Coated silver nanoparticles (AgNPs) have recently become a topic of interest due to the fact that they have several applications such as in electronic, antimicrobial, industrial, optical, and medical fields as biosensors and drug delivery systems. However, the use of AgNPs in medical fields remains somewhat limited due to their probable cytotoxic effect. Researchers have succeeded in reducing the toxicity of silver particles by coating them with different substances. Generally, the coating of AgNPs leads to change in their properties depending on the type of the coating material as well as the layer thickness. This review covers the state-of-the-art technologies behind (a) the synthesis of coated AgNPs including coating methods and coating materials, (b) the cytotoxicity of coated AgNPs and (c) the optical properties of coated AgNPs.

Various morphologies of CuO nanostructures (oval, cluster, leaves, small rod, porus nanosheets) have been synthesized by novel simple method using microwave radiation. The produced CuO nanostructures were characterized by X-ray diffraction analysis technique (XRD), transmission electron microscopy (TEM), surface area analyzer (BET) and energy dispersive spectroscopy (EDS). The ability of CuO nanostructures as adsorbent was investigated for adsorptive removal of Pb(II) ions from aqueous solutions. Various physico–chemical parameters such as pH, initial metal ion concentration, and equilibrium contact time were studied. The optimum solution pH for adsorption of Pb(II) from aqueous solutions was found to be 6.5 and the optimum contact time was found to be 4 h. The adsorption isotherms were obtained using concentrations of the metal ions ranging from 100 to 300 mg/l. The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and Freundlich adsorption isotherms. The maximum capacity of oval, cluster, leaves, small rod and porus nanosheets CuO nanostructures for Pb2+ are 125, 116, 117, 120 and 115 mg/g. This study revealed that CuO nano structures was an effective adsorbent for removal of Pb(II) ions from aqueous solutions.

Asymmetric single-hole mesoporous silica nanocages, which are eccentric hollow structured spheres and consist of mesoporous shell with an open hole on their surface, with uniform particle size (100-240 nm), have successfully been synthesized via a novel anisotropic encapsulation of the mesoporous silica. In this unique nanocarrier, the eccentric hollow cavity and big hole (∼25 nm) can serve as a storage space and passage for large guest molecules. Meanwhile, the uniform mesopores (2-10 nm) with a high surface area (∼500 m(2)/g) in the silica shells of the nanocages can provide storage space for small guest molecules. The obtained single-hole mesoporous nanocages can be endowed upconversion luminescence. The obtained upconversion nanoparticles functionalized eccentric single-hole nanorattles were used to codeliver bovine serum albumin and doxorubicin dual-sized guests. The release of the dual-sized guests can be well controlled independently by heat and near-infrared (NIR) light with the assistance of NIR to ultraviolet/visible (UV/vis) optical properties of upconversion nanoparticles and heat-sensitive phase change materials.

Purpose Additive manufacturing raw material cost has been recently confirmed as a significant obstacle to widespread deployment of these technologies in industry. Aiming at reducing the cost of the selective laser melting (SLM) process, the purpose of this paper is to evaluate the different properties of products fabricated by SLM using low‐cost ($10/Kg) feedstock 304L stainless steel powders. The entire process cost was also evaluated. Design/methodology/approach Using an experimental approach, 24 samples with different shapes and sizes were fabricated with layer thickness of 30, 50 and 70 μm and laser scanning speed set at 70 and 90 mm/s. Part geometry, dimensional tolerance, surface quality, density, mechanical properties and microstructure were evaluated. Findings Results confirmed that the SLM of low‐cost 304L powder was successful and could produce functional parts with fine details and small wall thickness. Using small layer thickness and low scanning speed improved the properties by more than 20 per cent. At a layer thickness of 30 μm and speed of 70 mm/s, density was 92 per cent and hardness was 190 HV. At layer thickness of 70 μm porosity increases and cracks started to form which decreased strength and ductility. The steel remained austenitic with no carbide films at grain boundaries due to the high melting and cooling cycles. Research limitations/implications This research was limited to 304L powders. Future work should be done on different materials and should include the effect of post processing heat treatment on improving the mechanical properties and microstructure. Practical implications The cost of the SLM process using feedstock powders was less than 10per cent of the cost of using the special powders from a machine manufacturer with almost no effect on product quality. Originality/value The paper describes how cost reduction in the SLM process was achieved by using 304L powder.

Pre-shaped mesoporous amorphous rice husk ash (RHA) and MCM-41 derived from RHA as a silica source were transformed into MFI-type zeolites using two different structure-directing agents. Tetrapropylammonium hydroxide (TPAOH) was utilized as an alkali source for silica dissolution and structure control during the direct transformation of RHA into zeolite. A monopropylamine (PA)-containing alkaline solution (NaOH) was used for the pseudomorphic transformation of RHA or MCM-41 into zeolite. The hydrothermal conversion of RHA or MCM-41 into MFI-type zeolites was investigated as a function of reaction time at 175 °C. With PA as template, the crystallization took place inside and on the outer surface of RHA or MCM-41 without losing the original shape of the initial silica sources, while TPAOH led to the formation of conventional MFI-type zeolite crystals due to the complete dissolution of RHA. The final products were characterized by X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and optical emission spectroscopy.

TiO2 nanopigments in two pure crystallographic forms (anatase and rutile) have been synthesized successfully by two methods; hydrothermal and hydrolysis. The produced pigments from the two methods were investigated physicochemically by several analyses tools. Then they were applied in paper coating mixtures and their influence on coated paper properties was systematically investigated. XRD and FTIR investigations showed that the prepared pigments using hydrothermal method at 100 and 120 °C were a mixture of anatase and brookite and pure anatase, respectively, whereas hydrolysis method produced pure rutile phase pigment. TEM investigation showed that the crystallite size of anatase, mixture of anatase and brookite and rutile samples are 6.2, 11.7, and 9.2 nm, respectively. BET studies proved that anatase pigment has 140.74 m2/g, 0.237 cc/g and 18.33 Å, whereas rutile has 60.621 m2/g, 0.122 cc/g and 14.669 Å, surface area, pore volume and pore diameter, respectively. UV–Vis absorption and PL emission characteristics of the prepared pigments showed that the energy gaps for anatase, mixture of anatase and brookite and rutile are 3.36, 3.30 and 3.37 eV, respectively. The addition of the prepared nanopigments in conjugation with clay in coating mixture increased both brightness and opacity of the coated papers. The greatest effect was obtained upon using rutile nanopigment. Also there was a significant decrease in coated paper roughness while the air permeance started to decrease then increased at 50 % addition levels. In all coated paper, rutile pigment showed the highest enhancement effect on coated paper properties.