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Microstructure and residual stress evolution in nanocrystalline Cu-Zr thin films
No full textGrazing incidence X-ray diffraction (GIXRD) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) were employed to study the microstructure evolution and stress development in the nanocrystalline Cu100-X-Zr-X (2.5 at% <= x <= 5.5 at%) alloy thin films. Small Zr additions to Cu led to significant lattice parameter anisotropy in the as-deposited Cu-Zr thin films both due to macroscopic lattice strain and stacking faults in the Cu matrix. Strain free lattice parameters obtained after the XRD stress analysis of Cu-Zr thin films confirmed formation of a supersaturated substitutional Cu-Zr solid solution. For the first time, the study of film microstructure by XRD line profile analysis (XLPA) confirmed progressive generation of dislocations and planar faults with increasing Zr composition in Cu-Zr alloy films. These microstructural changes led to the generation of tensile stresses in the thin films along with considerable stress gradients across the films thicknesses which are quantified by the traditional d(Psi)(hkl) - Sin(2)Psi and GIXRD stress measurement methods. The origin of tensile stresses and stress gradients in the Cu-Zr film are discussed on the basis of film growth and heterogeneous microstructure with changing Zr composition. (C) 2021 Published by Elsevier B.V
Biodegradation Study of Potato Starch-Based Bioplastic
No full textBackground: Plastics are indispensable for our society. The extensive use of petroleumbased plastic and dumping of the same in soil and water body greatly affects our environment and biodiversity. However, biodegradable plastics can reduce the volume of waste in packaging materials. Therefore, biomass-derived polymers are promising alternatives to the petroleum-based non-degradable polymer to address the environmental issues.
Objective: A large number of reports on the synthesis and characterization of starch-based bioplastic are available in the literature. However, a detailed biodegradation study of the starchbased bioplastic is rarely reported. We have prepared potato starch-based bioplastic with the combination of various plasticizers (glycerol, sorbitol, and xylitol) through hydrogel formation and carried out their biodegradation study.
Methods: Present study investigated the biodegradation of potato starch-based bioplastic in the natural environment, in cultured bacteria, and with fungal α-amylase.
Results: Starch-based plastic is completely degraded in the natural environment within two months. Bacteria culture in solid media resulted in various types of bacterial colonies. Among the various bacterial colonies, the white circular colony was the major bacteria that degrade starchbased plastic. Furthermore, we screened the starch-based plastic degrading bacteria and isolated the pure culture through the streak plate method.
Conclusion: In the presence of cultured bacteria and with fungal α-amylase, starch-based plastic is completely degraded within 96 h and 48 h, respectively
Study on the flotation of sillimanite using Plant-based collector
Get PDFThe coastal lines of India are rich in placer deposits of valuable heavy minerals such as ilmenite, garnet, rutile, zircon and sillimanite. The conducting and magnetic minerals are separated first, leaving behind the non-conducting and non-magnetic sillimanite along with quartz in the processing of heavies in beach sand. Sillimanite, an important mineral for refractory application is mainly recovered by flotation technique from its associated major gangue mineral, quartz by imparting selective surface hydrophobicity on sillimanite using a suitable collector. A placer sample after the removal of heavies from eastern coast of India was studied for beneficiation using froth flotation technique. Detailed characterization studies of the feed sample and the types of collectors used for this study have been carried out using XRD and FTIR analyses. Sillimanite feed sample assaying 55.4% sillimanite along with 33.9% quartz, 1.7% magnetics, 1.4% rutile, 2.4% zircon, 5.6% kynite was subjected to beneficiation using flotation technique for enriching the sillimanite content using oleic acid and a plant-based reagent SFA as collector. The effect of variation of input parameters such as pH, depressant and collectors were evaluated and flotation process optimization was carried out. Based on the results, it was found that flotation performance of the natural source based collector has better selectivity and improved recovery as compared to that of oleic acid as collector. Weight recovery of 67.8% with 85.1% sillimanite was obtained using the plant-based collector while a weight recovery of 55.5% with 84.9% sillimanite was obtained using oleic acid. The improved sillimanite recovery by using the plant-based collector than that of the conventional oleic acid would be more economical in industrial scale sillimanite recovery in beach sand processing industries
Exploratory studies on beneficiation of low-grade Banded Iron ore Formations (BIF) of Karnataka, India
Get PDFIron ore is the basic raw material for production of metallic iron. With depletion of high-grade resources and fine dissemination of valuable minerals in the abundantly available low-grade banded iron ore formations (BIF), liberation is achieved at finer sizes. Hence, it necessitated all beneficiation techniques to be operated at this finer size. However, physical separation techniques have limitations in separation efficiency. A combination of pre-concentration technique such as magnetic separation followed by flotation of magnetic fraction proved to be promising in achieving the respectable grade. A low-grade iron ore sample (BIF) of Karnataka, India was subjected to high intensity magnetic separation followed by flotation for enhancing its grade and recovery. Laboratory scale studies on this ore assaying 39.80 Fe%, 39.62 SiO2% and 1.73 Al2O3% indicated that it could be improved to 63.78 Fe%, 3.10 SiO2% and 1.01 Al2O3% at an overall iron recovery of 24% only. However, attempts are being made to further improve the iron recovery
Conservation of Resources by Processing of Waste Dumped Iron Ore Fines
Get PDFThe dumped iron ore sample having 49.62% Fe, 6.96% SiO2, 9.94% Al2O3, and 7.65% LOI was used for the present investigation. Characterization studies of the as-received sample reveal that major iron-bearing minerals present in the ore are hematite and goethite. The magnetite/ martitized magnetite is observed in minor traces. The major gangue minerals are clay and gibbsite followed by quartz. The present study aims to enrich the iron values of dumped iron ore fines to produce a value-added product. The iron values present in the feed sample were enriched by removing silica and alumina. The deslimed feed was subjected to a Floatex Density Separator. A statistical factorial design matrix was followed for conducting the tests using the process variables as, teeter water flowrate, bed pressure, and pulp density. The underflow obtained from FDS content is 58.2% Fe and the product yield is 64.4%. For further enrichment of the Fe-grade of the U/F, it was ground to 150μm for better liberation. After desliming the ground product of U/F, Fe-grade could be improved to 60%, and further subjecting the deslimed product to magnetic separation enhances the Fe-grade to 62% with mass recovery of 44.5%. The final product produced from the dumped iron ore fines could be used
for pellet feed
Microstructural Effect of Iron In Titanium Zirconium Alloys
No full textThe report starts with an introduction of basic concepts of some metals are titanium, zirconium, iron, molybdenum etc, which exhibit excellent physical, chemical and mechanical properties after alloying. Design and implementation of these kind of alloys possible by metallurgical development for different compositions required.
Many reactive metals are difficult to prepare in pure form without complex procedures. Alloy development is the key factor for development of better materials for engineering applications.
To maintain the superior biocompatibility, corrosion resistance etc of some alloy elements especially in biomedical implants and consumer applications like eye glasses, wrist watches are becoming major attaraction for human kind in the present days due to excess skin allergies caused by metal ions reactions of biomedical implants
Further, the most important characteristic property before alloying has to be considered is corrosion resistance. As no metal, or alloy, is entirely inert to corrosion, it is important to understand the characteristics before using it in any applications.
The result indicates that addition of iron in Zirconium improves the effect of β-phase stability and improves the properties of titanium zirconium alloys for many applications. Hence we proposed to study the phase behaviour of the Zr-Ti-Fe alloy along with characterization of the alloys.
Hence in this MTech thesis we focus on the effect of iron on (Zr-Ti) alloy and microstructural and mechanical properties. In this study, alloys are to be fabricated by arc melting followed by polishing and etching treatments to achieve observe optical microstructural effect of the alloys. Further alloys will be characterised by X-ray diffraction, SEM micro hardness and TEM
Microbial Processing of Waste Shredded PCBs for Copper Extraction Cum Separation—Comparing the Efficacy of Bacterial and Fungal Leaching Kinetics and Yields
Get PDFThe recycling of electronic scrap is an important subject not only from an environmental
aspect but also for recovering metal resources such as copper. In this work, the microbial extraction
of copper and other metals (Cu, Ni, Co, Fe and Al) present in the depopulated and shredded printed
circuit board (PCB) is elaborated. Bacterial strains of A. ferrooxidans, A. thiooxidans and a fungal
strain, A. niger are used for copper extraction along with other metals from shredded PCBs. An
optimum metal recovery of 93% Cu was obtained at 308 K, pH 2 using 8% pulp density in 10 days
by a mixed culture of A. ferrooxidans and A. thiooxidans. Whereas using A. niger, a metal recovery of
66% Cu was reported using similar experimental conditions. The results show the higher potential
ability of bacteria as compared to fungus to bioleach copper. Additionally, the kinetics and mechanism of copper bioleaching from this e-waste by the chemolithotrophs and heterotrophs were evaluated. The leach liquor obtained from the optimized leaching process was subjected to separation
and purification of copper as >99% pure copper sulfate using Acorga M5640 by solvent extraction
Corrosion performance of hot-dip galvanized zinc-aluminum coated steel rebars in comparison to the conventional pure zinc coated rebars in concrete environment
No full textIn this investigation zinc was alloyed with aluminum in order to improve the corrosion resistance of hot-dip galvanized coated steel rebars in contact with chloride-contaminated concrete. To rapidly assess the role of aluminum alloying in zinc, test panels in sheet form containing 10%, 15%, 20%, and 30% aluminum in zinc were prepared and evaluated in terms of their corrosion resistance via salt spray exposure tests. It was found that 10%Al-90%Zn (10AZ) provided the best results. Mild steel rebars were galvanized in 90% Zn-10%Al and 100%Zn (100Z) baths and their corrosion resistance performances when they were exposed to simulated concrete pore solution and embedded in mortars were examined. The10AZ-coated rebar showed superior corrosion resistance performance to the 100Z-coated rebar. Electrochemical impedance spectroscopy, DC polarization, scanning electron microscopy, Raman spectroscopy, and X-ray diffraction techniques were used to study the kinetics and corrosion mechanism of the coated rebars. (C) 2020 Elsevier Ltd. All rights reserved
Microstructural investigation of rolling contact fatigue (RCF) on a failed planetary gear of a windmill gearbox
No full textA systematic investigation of failed planetary gear in a windmill gearbox was carried out. The damaged teeth were investigated in order to determine the damage mechanisms that contributed to the failure. During the visual examination, few representative gear teeth were selected with signatures of spalling, micro pitting, cracks following the elliptical path along with fractured surfaces for further investigation. Subsequently, the SEM fractography showed beach marks indicating the fatigue as a operative mechanism for crack propagation. In addition to this, the surface residual stress analysis by x-ray method showed the tensile nature at the tip, while being compressive at the root for damaged gear teeth. Furthermore, the detailed microstructural investigation of damaged gear teeth at a cross-sectional region revealed the nucleation of microcracks at interphase boundaries, dark etch bands along with severe plastic deformation at the core that further transmitted to the elliptical crack path. Finally, it has been established that the failure was initiated due to micropitting, which aggravated the subsurface microcracks leading to spalling, macro crack growth in the elliptical path across the gear teeth leading to final fracture due to the operation of rolling contact fatigue (RCF)
Creep Deformation Behavior of Inconel 617 Alloy in the Temperature Range of 650 degrees C to 800 degrees C
No full textCreep behavior of the Inconel 617 alloy has been investigated through tests carried out in the temperature range of 650 degrees C to 800 degrees C under 95 to 350 MPa. Creep curves obtained from tests on the alloy exhibit a non-classical nature, with the primary creep rate decreasing to a minimum value, followed by a typical increase, which is either continuous at temperatures 5 has been rationalized by considering the existence of threshold stress, which like n has been found to decrease sharply with temperature beyond 700 degrees C. Investigation of the post-creep microstructures by transmission electron microscope has revealed the formation of gamma ' and M23C6 precipitates, which obstruct dislocation motion during the primary stage. Microstructures of the samples creep-tested at >= 750 degrees C have exhibited relatively smaller amounts of gamma '. The existence of threshold stress and the steady-state regime in the tertiary creep stage has been ascribed to obstruction of dislocation motion by M23C6 and gamma ' precipitates