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Atomistic characterization of multi nano-crystal formation process in Fe-Cr-Ni alloy during directional solidification: Perspective to the additive manufacturing
No full textThe directional solidification phenomenon has been observed in conventional castings and state-of-the-art manufacturing processes like additive manufacturing of steel. Precise control of temperature gradient during directional solidification in the additive manufactured components is essential to get growth and evolution of various crystalline structures, which enhance the properties. In this study, we have used molecular dynamics simulation to investigate the directional solidification of Fe-Cr-Ni steel under a wide range of temperature gradients. It is observed that multiple crystal morphology such as single crystal, nano-grains, multiple stacking faults, twins etc. Form during directional solidification depending on the temperature gradient. Evolution of various crystalline structures characterized by adaptive common neighbour analysis, surface area, volume and corresponding dimensionless aspect ratio. The current investigation adds to the pedagogical understanding of the effects of thermal gradients on the evolution characteristics of crystal morphology evolved during modern additive manufacturing processes
Thermo-mechanical property enhancement of rigid polyurethane foam using silica and alumina as hybrid fillers over single filler
No full textSilica and alumina particles were loaded in the rigid polyurethane foam composite as hybrid fillers. After the successful addition of silica and alumina as fillers, various properties of the foam composite were enhanced up to a particular weight percentage (7.5 wt% of silica and alumina each) with respect to alumina loaded foams. Hard urea domains are well distributed in the urethane matrix which indicates the absence of the peak representing H-bonded urea in the Fourier-transform infrared spectroscopy results. The addition of hybrid fillers into the rigid polyurethane foam matrix improved the compressive strength of the foam composite by 14% in comparison to alumina loaded foams due to the synergistic effect of the hybrid fillers. The foam composite at 7.5 wt% loading of hybrid fillers was successful in decreasing the thermal conductivity by 9% with respect to the thermal conductivity of the unloaded foam. There was a reduction in the gross calorific value up to 7% in the hybrid filler loaded foam composite when compared with that of the alumina loaded composite. Hence, hybrid fillers should be added to enhance the composite's properties by a greater extent
Synthesis of TiO2 from the Low-Grade Ilmenite Using the Mechanical Activation and Reductive Pressure Leaching in Low-Concentration H2SO4
No full textThe synthesis of TiO2 from the low-grade Indian ilmenite feedstock using the reductive pressure leaching process route has been presented in this work. Results show that the Ti and Fe dissolution efficiency has improved from 50% each to 74% and 78%, respectively, with the addition of 10 g center dot L-1 urea in 7.5 mol center dot L-1 H2SO4 at optimized leaching conditions. After the mechanical activation of ilmenite ore for 45 min, the Fe and Ti dissolution increased further to 93% and 90%, respectively. The leaching kinetics of both Fe and Ti are controlled by the solid-liquid chemical reaction mechanism in the presence and absence of reductant. XRD and SEM-EDX results show that an amorphous anatase grade TiO2 with 95% purity is obtained as the final product after crystallization, hydrolysis, and calcination steps. The total extraction efficiency of TiO2 is found to be 85%
Experimental investigation on microstructure and mechanical property of wire arc additively manufactured SS308L built part
No full textWire arc additive manufacturing (WAAM) is a class of arc-based metal additive manufacturing (AM) under the category of direct energy deposition. As compared to other metal-based AM techniques, WAAM is capable of fabricating medium-to-large sized parts (having a low level of design complexity) with a nearly fully dense structure. Ease of near-net shaping with a high material utilization rate has made the process economic in various industrial applications starting from prototype to customized product fabrication. The quality of the built part is strongly affected by the feedstock wire composition, welding parameters, and deposition strategy. Due to its complicated thermal history, the WAAMed part suffers from considerable anisotropy in microstructure as well as mechanical properties. The present work attempts to fabricate a 3D slab by layer-wise deposition of molten SS308L-T1 feedstock wire through a CMT + MIG-based WAAM process. Initially, a few pilot experiments (by depositing single-track bead-on-plate welds and stacked weld specimens) are performed to determine values of the appropriate process parameters for the WAAM of the SS308L part. The appropriate setting of parameters which includes current, voltage, gas flow rate, nozzle-to-plate distance, start/end current percentage, degree of overlap, and deposition strategy (applicable for stacked specimens), etc. are obtained based on visual inspection of the built quality and measurable features of bead geometry. Finally, a 3D wall is successfully fabricated having approximate dimensions 150 x 25 x 30 mm(3). The microstructure evolution and mechanical property characterization of the as-built part are carried out. It is experienced that the microstructure and mechanical properties of WAAMed SS308L are location-dependent. The as-built microstructure contains d ferrite (skeletal, vermicular, and lathy morphologies) which is deposited at grain boundaries of? austenite. The middle zone of the fabricated slab appears to be relatively softer than the top and bottom zones; the middle zone corresponds to the lowest tensile strength along the horizontal direction (similar to 541 MPa) but the highest fracture strain (elongation percent similar to 38%). The average tensile strength along the horizontal direction is obtained as similar to 548 MPa. Fractographic results of failed tensile specimens evidence ductile fracture mode characterized by dimples along with the presence of second-phase spherical particles. The average microhardness of the as-built SS308L obtained is 171 HV0.1
Phase stability and role of mechanical activation in the chemical beneficiation of red mud
No full textThis paper focuses on the carbothermic reduction of red mud in the presence of sodium carbonate. The emphasis is on the reduction step in the 'Elgai process' which is central to the chemical beneficiation and carried out in the temperature range where fusing of roasting mass is avoided. The research, aimed at developing a fundamental understanding of the roasting has three different facets: (a) calculation of phase equilibrium in Fe2O3-Al2O3-Na2CO3-C and related systems for the relevant compositions and temperature range (650-950 & DEG;C); (b) simultaneous thermal analysis (TG/DTA) studies based on phase stability; and (c) roasting and leaching of red mud-soda-carbon pellets. Red mud was used in the as-received condition and after mechanical activation in an attrition mill. Red mud and roasted products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) with X-ray microanalysis (EDS). The reduction temperature and carbon requirement were found to depend on the Al2O3 content of red mud, notably the occurrence of aluminogoethite. The interdependence of the decomposition of sodium carbonate, metallization of red mud, sodium aluminate formation, and alumina recovery are elucidated. Mechanical activation improves the degree of metallization and alumina recovery. The significance of Ca(OH)(2) addition as a way forward to reduce the decomposition temperature of sodium carbonate and the consequent reduction in the roasting temperature is highlighted
Enhanced structural integrity of Laser Powder Bed Fusion based AlSi10Mg parts by attaining defect-free melt pool formations
No full textThis research aims to fabricate AlSi10Mg parts using Laser Powder Bed Fusion technique with enhanced structural integrity. The prime novelty of this research work is eliminating the balling and sparring effects, keyhole and cavity formation by attaining effective melt pool formation. Modeling of the Laser Powder Bed Fusion process parameters such as Laser power, scanning speed, layer thickness, and hatch spacing is carried out through the Complex Proportional Assessment technique to optimize the parts' surface attributes and to overcome the defects based on the output responses such as surface roughness on scanning and building side, hardness and porosity. The laser power of 350 W, layer thickness of 30 mu m, scan speed of 1133 mm/s, and hatch spacing of 0.1 mm produces significantly desirable results to achieve maximum hardness and minimum surface roughness and holding the porosity of < 1%. The obtained optimal setting from this research improves the structural integrity of the printed AlSi10Mg parts
A R&D productivity model to achieve self-sustainability for public funded/CSIR R&D laboratories, India
Get PDFPurpose – The paper develops a model for enhancing R&D productivity for Indian public funded
laboratories. The paper utilizes the productivity data of five Council of Scientific and Industrial Research (CSIR)
laboratories for analysis and to form the constructs of the model.
Design/methodology/approach – The weighted average method was employed for analyzing the rankings
of survey respondents pertaining to the significant measures enhancing R&D involvement of researchers and
significant non-R&D jobs. The authors have proposed a model of productivity. Various individual, organizational
and environmental constructs related to the researchers working in the CSIR laboratories have been outlined that
can enhance R&D productivity of researchers in Indian R&D laboratories. Partial Least Squares-Structural
Equation Modeling (PLS-SEM) was used to find the predictability of the productivity model.
Findings – The organizational factors have a crucial role in enhancing the R&D outputs of CSIR laboratories.
The R&D productivity of researchers can be improved through implementing the constructs of the proposed
model of productivity.
Research limitations/implications – The R&D productivity model can be adapted by the R&D
laboratories to enhance researchers’ R&D involvement, increased R&D outputs and achieving self-sustenance
in long run.
Practical implications – The R&D laboratories can initiate exercises to explore the most relevant factors
and measures to enhance R&D productivity of their researchers. The constructs of the model can function as a
guideline to introduce the most preferable research policies in the laboratory for overall mutual growth of
laboratory and the researchers.
Originality/value – Hardly any studies have been found that have focused on finding the measures of
enhancing R&D involvement of researchers and the influence of significant time-intensive jobs on researchers’
productivity.
Keywords R&D productivity model, CSIR, Mandays-involvement, Non –R&D jobs
Paper type Research pape
In Retrospect: Some Peculiarities Observed in the Mechanical Activation of Ground-Granulated Blast Furnace Slag and Fly Ash
No full textThe focus of this paper is on the mechanical activation of aluminosilicate wastes, namely ground-granulated blast furnace slag (GGBFS) and fly ash (FA). The subject is of relevance to the development of improved blended cement and geopolymers. The presence of large quantities of amorphous phases in these materials makes them unique and challenging from the point of view of characterization. Interesting findings, some of which were first-time discoveries, are reviewed with emphasis on the role of the milling device (mill type, milling energy, and environment), characterization challenges, and the manifestation of mechanically induced reactivity. The relative importance of mechanical activation vis-a-vis reaction temperature is highlighted based on calorimetric maps for the geopolymerisation of fly ash
The utilisation of coconut shell ash in production of hybrid composite: Microstructural characterisation and performance analysis
No full textAgriculture waste-reinforced hybrid metal matrix composites (HMMCs) have developed as a potentially green, productive, economical, and ideal replacement for particle-reinforced composites. A number of industries, including aerospace, automotive, and packaging, have demonstrated a keen interest in the development of new and innovative composites in a sustainable manner, is bio-waste particulate reinforced composite. The effect of reinforcements is investigated in the current research work, which employs the ultrasonic stir casting method with SiC (ranging from 3 to 9% by weight) and coconut shell ash (5% by weight in equal proportion) as rein-forcement along with the aluminium matrix. With the two-stage ultrasonic stir casting process, the distribution of reinforcement in the aluminium matrix is ensured to be uniform. The microstructure evolution, mechanical and tribological behaviours were also evaluated to ascertain the integrity of fabricated composites. The XRD analysis confirms the reinforcements and oxide layer formed on the specimen surface. Currently, the fabricated composite improves monolithic alloy in terms of hardness and tensile strength approximately by 60% and 66%, respec-tively, while reducing wear rate by 51%. The nanoindentation investigation implies that the composites that have been developed have improved nanomechanical properties. Overall, using CSA along with SiC in HMMCs could be a potential product to reduce the usage of synthetic fiber and application design for economical products
Flotation of Low-Grade Graphite Ore Using Collector Derived from Low-Density Polyethylene Waste
No full textThe increasing wide range of applications of graphite for electrode, lubricants, refractory applications especially the recent surging electric automobile industry results in significant need of graphite in future. Graphite demand in the energy storage industry is expected to grow 15 times faster than today's demand by 2030. Due to depleting high-grade ore, utilization of low-grade ore by beneficiation becomes utmost importance for sustainable development and resource management. In this work, low-grade graphite ore from Tamil Nadu, India, with 86.84% ash was beneficiated by flotation technique for recovering graphite with lower ash content. Flotation, a surface phenomenon, based on the surface hydrophobicity of the mineral surface to be separated and since graphite is naturally flotation mineral, this technique is adopted for beneficiation. The most commonly used collector in graphite flotation is diesel. In view of continuous cost escalation of diesel, an alternate collector was developed utilizing the low-density polyethylene (LDPE) waste paving way for plastic waste utilization. The flotation efficacy of this new collector (Collector PE) derived from LDPE waste was compared with that of diesel in graphite flotation. The run-of-mine graphite ore was initially size reduced for liberation of values from its associated impurities, followed by flotation. The mesh-of-grind, dosages of collector (diesel and PE), and frother (Methyl Isobutyl Carbinol, MIBC) were optimized for better process efficiency for increasing the surface hydrophobicity of graphite particles leading to better separation efficacy. The ore characterization by X-ray diffraction revealed that graphite was accompanied predominantly by quartz with minor fractions of pyrites and several other phyllosilicates such as kaolinite and muscovite. Exfoliated morphology of graphite with thick layers were observed from SEM images. Flotation reagents such as diesel, collector PE, and MIBC were characterized by FTIR to analyze their functional groups that enhance the efficiency of the separation process. A graphite float (rougher concentrate) with 15.2% weight recovery and 17.7% ash content was obtained after 10 min of grinding (d80: 240.5 µm) with 0.85 kg/t of collector (diesel) and 0.07 kg/t of frother (MIBC) dosages and on two-stage cleaning, a final concentrate with 12.66% weight recovery and 8.70% ash content was obtained. A graphite final concentrate with 13.04% weight recovery and 8.90% ash was achieved with two-stage cleaning, when treated with 0.57 kg/t of collector PE and 0.07 kg/t of MIBC. These results indicate that the flotation efficiency of the collector PE derived from LDPE wastes is comparable with that of diesel and would be economical when used in large-scale industrial graphite flotation