A study on structural, optical, and electrical characteristics of perovskite CsPbBr3 QD/2D-TiSe2 nanosheet based nanocomposites for optoelectronic applications.

Lead halide perovskite (CsPbBr3) quantum dots (QDs) and two-dimensional (2D) layered transition metal dichalcogenides have a significant application in solution-processed optoelectronic devices. Here, we report the oleylamine-assisted exfoliation of TiSe2 nanosheets (NSs) in dichlorobenzene with high concentration and stable dispersion. The functionalized TiSe2 NSs were used to synthesize the solution-processed perovskite CsPbBr3 QD/TiSe2 NS-based nanocomposite. The perovskite QDs and TiSe2 NSs were characterized by different techniques. The strong photoluminescence (PL) quenching and decreased lifetime decay of the nanocomposite indicates efficient charge transfer from photo-excited CsPbBr3 to TiSe2 NSs. The calculated charge-transfer rate constant (KET) from photo-excited CsPbBr3 to TiSe2 NSs increased from 1.50 × 108 to 2.79 × 108 s-1 in different concentrations of TiSe2 NSs (5 to 20 µg mL-1), respectively. Furthermore, the photo-currents of CsPbBr3 QD/TiSe2 NS nanocomposite devices were dramatically enhanced ∼2 times compared to pristine CsPbBr3 QD based devices, which supports the charge transfer and charge separation in nanocomposite devices.

A study on chemical exfoliation and structural and optical properties of two-dimensional layered titanium diselenide.

Titanium diselenide (TiSe2) is the least studied member of the transition metal dichalcogenide family due to a lack of available synthesis methodology, controlled bandgap engineering, and rapid characterization of layers. In this paper, we report the chemical exfoliation of TiSe2 platelets synthesized by the chemical vapor transport route in ortho-dichlorobenzene (o-DCB) functionalized with oleylamine (OLA), for the first time to the best of our knowledge. It is found that the addition of OLA supports the formation of a stable dispersion of a large area of the TiSe2 sheets due to surface capping with the OLA molecules indicating the importance of the ligand in dispersion behavior. The X-ray diffraction pattern confirms the hexagonal structure of the TiSe2 platelets with the space group P3[combining macron]m1 while Raman spectroscopy reveals that two modes of vibration i.e. A1g and E2g exist with layered structures having dimensions in micrometers as confirmed by scanning electron microscopy. Fourier transform infrared spectroscopy confirms the successful functionalization of chemically exfoliated TiSe2 nanosheets. Field-emission scanning electron microscopy reveals that exfoliated TiSe2 has a thickness of 15-55 nm whereas high-resolution transmission electron microscopy indicates thicker sheets for ligand-free exfoliated TiSe2 which are crystalline. Atomic force microscopy confirms the formation of nanosheets. UV-Visible, photoluminescence, and time-resolved PL spectroscopy showed an enhanced effect and better average lifetime of excitation for the exfoliated sheets with OLA than those without OLA. The C-V studies reveal that with increasing scan rate, the corresponding current also increases. The present study offers the possibility of their utilization in optoelectronics, advanced low-power electronics, voltage-controlled oscillators, ultra-fast electronics, and electrochemical devices.

Corrosion performance of various deformed surfaces of implant steel for coronary stent applications: Effect of protein concentration.

This work was done to systematically elucidate the corrosion behavior of austenitic stainless steel subjected to various degree of cold deformation (10 %, 20 % & 30 %). The experiments were performed in phosphate buffer saline (PBS) solution having different concentrations of bovine serum albumin (0.2, 0.5, 1.0, 2.0, 4.0 g L-1). Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) analysis were performed to obtain the corrosion parameters. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface morphologies and chemical compositions of the surface films. Contact angle analysis was also used to detect the hydrophilic character of sample surfaces. The BSA had a considerable effect of inhibition on the corrosion of SSs in annealed as well as in deformed state due to its adsorption on surface of steel. For annealed samples, at 4.0 g L-1BSA concentration, the corrosion resistance was drastically decreased but interestingly not for sample with more than 10 % deformation and the concentration effect of BSA is also not very significant after 0.5 g L-1 for deformed surfaces. The breakdown potential for 30 % deformed sample is quite higher in presence of BSA even at 4.0 g L-1 while it is lowest for annealed samples in the same condition. The variation in contact angle with deformation is very less after adsorption of BSA. On the basis of the obtained results, mechanism aspect for corrosion of steel in presence of protein is also deliberated.

Fluidized bed combustion bottom ash: A better and alternative geo-material resource for construction.

Though the majority of research on fly ash has proved its worth as a construction material, the utility of bottom ash is yet questionable due to its generation during the pulverized combustion process. The bottom ash produced during the fluidized bed combustion (FBC) process is attracting more attention due to the novelty of coal combustion technology. But, to establish its suitability as construction material, it is necessary to characterize it thoroughly with respect to the geotechnical as well as mineralogical points of view. For fulfilling these objectives, the present study mainly aims at characterizing the FBC bottom ash and its comparison with pulverized coal combustion (PCC) bottom ash, collected from the same origin of coal. Suitability of FBC bottom ash as a dike filter material in contrast to PCC bottom ash in replacing traditional filter material such as sand was also studied. The suitability criteria for utilization of both bottom ash and river sand as filter material on pond ash as a base material were evaluated, and both river sand and FBC bottom ash were found to be satisfactory. The study shows that FBC bottom ash is a better geo-material than PCC bottom ash, and it could be highly recommended as an alternative suitable filter material for constructing ash dikes in place of conventional sand.

Production of thermal insulation blocks from bottom ash of fluidized bed combustion system.

The issues of disposal and environmental problems are increased by the generation of bottom ash from the thermal power plants day by day; hence, its recycling is required. The present study aimed to make thermal insulation blocks using as raw material bottom ash and iron ore slime as a binder and to characterize their engineering properties. Two different fineness values of bottom ash were considered with varying amounts of iron ore slime (0-10%) to make the blocks. Blocks were dried followed by firing at 1000, 1100 and 1200°C, respectively. Cold crushing strength, density and thermal conductivity of these fired blocks showed increasing behaviour with firing temperature, fineness of bottom ash and iron ore slime content. In contrast, a reverse trend was observed in the case of porosity. With increasing firing temperature, the formation of lower melting phases like iron silicate followed by iron aluminium silicate was observed, which imparts the strength inside the blocks. The coarser particles of bottom ash increase the interparticle spaces, which enhances the apparent porosity, resulting in higher thermal insulation property in the blocks. Blocks having better thermal insulation property could be possible to make effectively from coarse bottom ash by adding iron ore slime as a binder.

Effect of nitrogen and cold working on structural and mechanical behavior of Ni-free nitrogen containing austenitic stainless steels for biomedical applications.

This investigation deals with the evaluation of structural and mechanical behavior of deformed (10% and 20% cold work) and annealed (at 1050°C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs). The microstructure was observed by optical micrograph and the mechanical properties were determined by macrohardness and tensile tests. Both stress strain behavior and work hardening behavior were evaluated. HNSs have smaller grain size as compared to low nitrogen steels and no formation of martensite was observed after 20% cold working. Further, it was found that hardness; yield strength and ultimate tensile strength of the steels linearly increases and elongation decreased with nitrogen content and degree of cold working. The strength coefficient was observed to be higher for the high nitrogen steels; it decreased to some extent with degree of cold working. The work hardening exponent was also observed to decrease with degree of cold working. Influence of nitrogen on mechanical properties was mainly related to its effect on solid solution strengthening. X-ray diffraction analysis of annealed as well as deformed alloys further confirmed no evidence for formation of martensite or any other secondary phases. SEM fractography of the annealed and deformed samples after tensile tests indicates predominantly ductile fracture in all specimens.

In-vitro long term and electrochemical corrosion resistance of cold deformed nitrogen containing austenitic stainless steels in simulated body fluid.

This work was focused on the evaluation of the corrosion behavior of deformed (10% and 20% cold work) and annealed (at 1050 °C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs) in simulated body fluid at 37°C using weight loss method (long term), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Scanning electron microscopy (SEM) was used to understand the surface morphology of the alloys after polarization test. It has been observed that cold working had a significant influence on the corrosion resistant properties of these alloys. The weight loss and corrosion rates were observed to decrease with increasing degree of cold working and nitrogen content in the alloy. The corrosion resistance of the material is directly related to the resistance of the passive oxide film formed on its surface which was enhanced with cold working and nitrogen content. It was also observed that corrosion current densities were decreased and corrosion potentials were shifted to more positive values. By seeing pit morphology under SEM, shallower and smaller pits were associated with HNSs and cold worked samples, indicating that corrosion resistance increases with increasing nitrogen content and degree of cold deformation. X-ray diffraction profiles of annealed as well as deformed alloys were revealed and there is no evidence for formation of martensite or any other secondary phases.

Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line.

The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation.

A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications.

The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels.