Novel adhesion promotion of aluminium for aerospace environments

This study focuses on analysing the durability of adhesive bonds formed in samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063 using epoxy adhesive Weicon A. Two types of studies are performed, first, samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063, are bonded by an epoxy adhesive Weicon A. Second, the samples are bonded by the adhesive with reinforcement of Ca₂SiO₄ nanoparticles in different proportions. The samples are examined using the scanning electron microscopy to study the morphology of the coating. A lap shear test is performed to determine the strength of the adhesive after the specimens were subjected to harsh chemical environments. A thermogravimetric analysis is performed on the adhesive to understand the effect of nanoparticles in the thermal stability in the Weicon A. It is understood from the tests that the titanium nitride coated Al 6063 samples bonded with Weicon A exhibited greater bond strength and also retained the strength when exposed to harsh environments. The inclusion of calcium silicate nano-particles showcased a considerable reduction in the bond strength. The thermal stability of Weicon A seems to be unaffected by the inclusion of calcium silicate nanoparticles.     

Surface modification of HDPE and PP by mechanical polishing and DC glow discharge and their adhesive joining to steel

To improve the strengths of the adhesive joints of high density polyethylene (HDPE) and polypropylene (PP) to steel, the surfaces of HDPE and PP sheets have been treated by DC glow discharge to increase the polar component of surface energy significantly. Present study investigates the effect of mechanical polishing prior to surface modification of substrates of HDPE and PP sheets by exposure to DC glow discharge, on the surface energy and their adhesive joint strength to steel. The mechanical polishing has been carried out by abrading with 120, 220, 400, 600, 800, and 1000 grade emery paper of grit sizes 8.33, 4.54, 2.5, 1.67, 1.2, and 1 micron, respectively. The surface energy of a given surface has been evaluated by measuring contact angles of sessile drops of two test liquids of known surface tension components, such as deionized water and formamide. It is observed that 800‐grade emery paper of grit size 1.2 micron has been found most effective in terms of their reduction in contact angles and enhancement of their surface energies. The change in surface energy due to surface modification has also been evaluated by measuring the surface energies of unpolished sheets exposed to DC glow discharge. The surface modification of the polymers by glow discharge for 120 s at a power level of 13 W decreases the contact angle more on mechanically polished specimens than that observed on unpolished sheets. Due to glow discharge treatment, the polar component of surface energy increases significantly in HDPE and PP, especially when they are mechanically polished (800 grade) prior to glow discharge. However, in case of the HDPE sheets, the effect of glow discharge on the polar component of surface energy is significantly higher compared to that for dispersion component of surface energy, whereas the polar component of surface energy of the PP sheet is lower than the dispersion component of surface energy. But in both the cases, mechanical polishing prior to glow discharge appears to affect the polar component of surface energy. Mechanical polishing of the HDPE and PP sheets by abrading with 800‐grade emery paper prior to glow discharge treatment, increases the adhesive joint strengths over those observed in case of unpolished polymers exposed to glow discharge. However, the use of prior mechanical polishing increases the joint strength only by a little more than 10% compared to a five to seven times increase in strength observed as a consequence of exposure to glow discharge of as received samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1140–1149, 2001     

Triptycene‐based fluorescent polymers with pendant alkyl chains: interaction with fullerenes and morphology of thin films

We report unique triptycene‐based alternating copolymers bearing long alkyl chains as pendants. Syntheses utilized 2,6‐diethynyltriptycene and appropriate alkyloxyarene monomers polymerized via Sonogashira cross‐coupling reaction to yield triptycene‐based poly(phenylene ethynylene)s. Resulting polymers are soluble in organic solvents and were characterized using various techniques. Experimental results suggest the polymers are thermally stable and fluorescent. The fluorescence emission is quenched in the presence of fullerenes (C₆₀ and C₇₀) suggesting strong host–guest interactions. The magnitude of the binding constant between the polymers and these fullerenes was determined to be of the order of 10⁵ mol L^?1. The effects of chain length on the morphology and wettability of the polymers on silicon substrates were studied using atomic force microscopy. Three distinct dewetting patterns, i.e. spherical domains, fractal structures and ring structures, were observed with variation in the pendant chain length. This ability to control the thin‐film morphology of the polymers may have potential technological applications, which include but are not limited to sensors, fluorescent coatings and organic electronics. © 2018 Society of Chemical Industry     

Performance of a constructed wetland with a sulfur/limestone denitrification section for wastewater nitrogen removal

The effectiveness of a nonvegetated lab-scale subsurface flow constructed wetland for wastewater treatment had been evaluated with the feed ammonium concentration of approximately 20-40 mg of NH4(+)-N L(-1) and a hydraulic retention time of approximately 10 d. The present system had a nitrification zone plus a sulfur/limestone (S/L) autotrophic denitrification zone followed by an anaerobic polishing zone and was operated with and without aeration. The wetland had only 80% organics removal and no net nitrogen removal when there was no artificial aeration. However, almost 100% organics removal and approximately 81-90% total inorganic nitrogen (TIN = NH4(+)-N + NO2(-0-N + NO3(-)-N) removal were achieved when the oxic zone of the system was aerated with compressed air. S/L autotrophic denitrification contributed 21-49% of total NO3(-)-N removal across the whole wetland and 50-95% across the S/L column. TIN and NH4(+)-N in the effluent were always < 5.5 and < 0.7 mg L(-1), respectively, when the feed had NH4(+)-N < or = 35 mg L(-1). Sulfate removal of approximately 53-69% was achieved in the anaerobic polishing zone. The position of the S/L column was changed (1.78, 2.24, and 2.69 m from the inlet), and no remarkable difference in nitrogen removal was observed. However, without the S/L column, TIN removal decreased to approximately 74%, and the effluent NO3(-)-N increased about two times (9.13 mg of N L(-1)). The present study has demonstrated the possible use of S/L autotrophic denitrification for nitrate removal in a constructed wetland.     

Grain size dependent magnetization, electrical resistivity and magnetoresistance in mechanically milled La0.67Sr0.33MnO3

We have studied magnetization, ac susceptibility, resistivity and magnetoresistance in mechanically milled La_0.67Sr_0.33MnO₃. The material with grain size micron to nanometer scale has stabilized in rhombohedral crystal structure with space group R3C. We have found various grain size effects, e.g., decrease of ferromagnetic moment, increase of surface spin disorder, and appearance of insulator/semiconductor type resistivity. In addition to these conventional features, we have identified a magnetic anomaly at 45 K in bulk sample. Ferromagnetic to paramagnetic transition temperature (T_C) is above room temperature for all samples. The samples are typical soft ferromagnet that transformed from multi-domain state to single domain state in nanocrystalline samples. The remarkable observation is that low temperature freezing of ferromagnetic domains/clusters does not follow the conventional spin glass features. Experimental results clearly showed the enhancement of high field magnetoresistance in nanocrystalline samples below 200 K, whereas low field magnetoresistance gradually decreases above 200 K and almost absent at 300 K. We have discussed few more magnetic and electrical changes, highly relevant to the progress of nanomaterial research in ferromagnetic manganites.     

Pharmacophore mapping of arylbenzothiophene derivatives for MCF cell inhibition using classical and 3D space modeling approaches

Considering the worth of developing non-steroidal estrogen analogs, the present study explores the pharmacophore features of arylbenzothiophene derivatives for inhibitory activity to MCF-7 cells using classical QSAR and 3D space modeling approaches. The analysis shows that presence of phenolic hydroxyl group and ketonic linkage in the basic side chain of 2-arylbenzothiophene core of raloxifene derivatives are crucial. Additionally piperidine ring connected through ether linkage is favorable for inhibition of breast cancer cell line. These features for inhibitory activity are also highlighted through 3D space modeling approach that explored importance of critical inter features distance among HB-acceptor lipid, hydrophobic and HB-donor features in the arylbenzothiophene scaffold for activity.     

Ferromagnetism in lead graphite-pencils and magnetic composite with CoFe2O4 particles

This work has been initiated with a curiosity to investigate the elemental composition and magnetic response of different grades of lead pencils (6B, 2B, HB, 2H, 5H) that people use in daily life. Interestingly, experimental results landed with a great achievement of observing soft magnetism in lead pencils, indicating a wide scope of magnetic tuning for room temperature applications. A novel magnetic composite has been synthesized by mixing different concentration of CoFe₂O₄ (CF) nanoparticles in 5H and 6B pencils for studying the magnetic tailoring aspects using pencils. Our results showed different possibilities of controlling disorder induced ferromagnetic parameters and a simple approach of producing sufficiently high coercive magnetic composite using pencils.     

Synthesis and characterization of poly(pyridinium salt)s derived from various aromatic diamines

Several poly(pyridinium salt)s containing various aromatic diamine moieties and tosylate counterions were prepared by the ring-transmutation polymerization reaction of bis(pyrylium tosylate) with aromatic diamines in dimethyl sulfoxide at 130?135 °C for 48 h and their tosylate counterions were exchanged to triflimide polymers by a metatheses reaction in an organic solvent. Their chemical structures were established by using various spectroscopic techniques. Their number-average molecular weights (M_n) were in the range of 38–46 kg/mol and polydispersities in the range of 1.13–1.43 as determined by gel permeation chromatography. They showed excellent thermal stabilities in nitrogen in the range of 326–477 °C. They exhibited lyotropic liquid-crystalline phase in polar aprotic and protic organic solvents above their critical concentrations depending on their microstructures and counterions. Their optical properties were examined by using UV–Vis and photoluminescent spectroscopy, which revealed that some polymers emitted UV light, some emitted blue light, and some emitted green light (both in solutions and solid states) depending on their microstructures, counterions, and on solvent polarity of organic solvents.     

Performance prediction of 60 kWp PV power plant in an educational institute

Due to government initiatives, many solar photovoltaic (PV) power plants of different sizes will be set up in India in the near future. In this context, the performance of a 60?kW_p PV power plant is discussed in this paper which is installed at National Institute of Technology (a centrally funded institute of Government of India), Agartala, located in a small state (Tripura) of North East India where supply of grid electricity is a critical issue. This article examines the various parameters for performance prediction of this solar power plant.     

Assessing compressive strengths of mortar and concrete from digital images by machine learning techniques

Compressive strength is the most important metric of concrete quality. Various nondestructive and semi-destructive tests can be used to evaluate the compressive strength of concrete. In the present study, a new image-based machine learning method is used to predict concrete compressive strength, including evaluation of six different models. These include support-vector machine model and various deep convolutional neural network models, namely AlexNet, GoogleNet, VGG19, ResNet, and Inception-ResNet-V2. In the present investigation, cement mortar samples were prepared using each of the cement:sand ratios of 1:3, 1:4, and 1:5, and using the water:cement ratios of 0.35 and 0.55. Cement concrete was prepared using the cement:sand:coarse aggregate ratios of 1:5:10, 1:3:6, 1:2:4, 1:1.5:3 and 1:1:2, using the water:cement ratio of 0.5 for all samples. The samples were cut, and several images of the cut surfaces were captured at various zoom levels using a digital microscope. All samples were then tested destructively for compressive strength. The images and corresponding compressive strength were then used to train machine learning models to allow them to predict compressive strength based upon the image data. The Inception-ResNet-V2 models exhibited the best predictions of compressive strength among the models tested. Overall, the present findings validated the use of machine learning models as an efficient means of estimating cement mortar and concrete compressive strengths based on digital microscopic images, as an alternative nondestructive/semi-destructive test method that could be applied at relatively less expense.