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Deep scientific drilling results from Koyna and Killari earthquake regions reveal why Indian shield lithosphere is unusual, thin and warm

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Geoscience Frontiers 2016年第5期7卷 851-858页

作者： o.p.pandey CSIR-National Geophysical Research Institute Uppal Road Hyderabad 500007 India

The nature of crustal and lithospheric mantle evolution of the Archean shields as well as their subsequent deformation due to recent plate motions and sustained intraplate geodynamic activity, has been a subject of considerable interest. In view of this, about three decades ago, a new idea was put forward suggesting that out of all shield terrains, the Indian shield has an extremely thin lithosphere（w100 km,compared to 250e350 km, elsewhere）, apart from being warm, non-rigid, sheared and deformed. As expected, it met with scepticism by heat flow and the emerging seismic tomographic study groups, who on the contrary suggested that the Indian shield has a cool crust, besides a coherent and thick lithosphere（as much as 300e400 km） like any other shield. However, recently obtained integrated geological and geophysical findings from deep scientific drillings in 1993 Killari（M w： 6.3） and 1967 Koyna（M w： 6.3）earthquake zones, as well as newly acquired geophysical data over other parts of Indian shield terrain,have provided a totally new insight to this debate. Beneath Killari, the basement was found consisting of high density, high velocity mid crustal amphibolite to granulite facies rocks due to exhumation of the deeper crustal layers and sustained granitic upper crustal erosion. Similar type of basement appears to be present in Koyna region too, which is characterized by considerably high upper crustal ***, such type of crust is depleted in radiogenic elements, it resulted into lowering of heat flow at the surface, increase in heat flow contribution from the mantle, and upwarping of the lithosphereasthenosphere boundary. Consequently, the Indian shield lithosphere has become unusually thin and warm. This study highlights the need of an integrated geological, geochemical and geophysical approach in order to accurately determine deep crust-mantle thermal regime in continental areas.

关键词： Indian lithosphere Killari seismic zone Deep drilling results Mafic crust Geodynamics Heat flow

Effect of electroslag remelting and homogenization on hydrogen flaking in AMS-4340 ultra-high-strength steels

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International Journal of Minerals,Metallurgy and Materials 2019年第5期26卷 611-621页

作者： Shivraj Singh Kasana o.p.pandey School of physics and Materials Science Thapar Institute of Engineering and Technology Star Wire (India) Ltd.Ballabgarh

Hydrogen flakes and elemental segregation are the main causes of steel rejection. To eliminate hydrogen flaking, the present study focuses on the manufacture of AMS-4340 ultra-high-strength steel through an alternate route. AMS-4340 was prepared using three different processing routes. The primary processing route consisted of melting in an electric arc furnace, refining in a ladle refining furnace, and vacuum degassing. After primary processing, the heat processes(D1, D2, and D3) were cast into cylindrical electrodes. For secondary processing, electroslag remelting(ESR) was carried out on the primary heats to obtain four secondary heats: E1, E2, E3, and E4. Homogenization of ingots E1, E2, E3, and E4 was carried out at 1220°C for 14, 12, 12, and 30 h, respectively, followed by an antiflaking treatment at 680°C and air cooling. In addition, the semi-finished ESR ingot E4 was again homogenized at 1220°C for 6–8 h and a second antiflaking treatment was performed at 680°C for 130 h followed by air cooling. The chemical segregation of each heat was monitored through a spectroscopy technique. The least segregation was observed for heat E4. Macrostructure examination revealed the presence of hydrogen flakes in heats E1, E2, and E3, whereas no hydrogen flakes were observed in heat E4. Ultrasonic testing revealed no internal defects in heat E4, whereas internal defects were observed in the other heats. A grain size investigation revealed a finer grain size for E4 compared with those for the other heats. Steel produced in heat E4 also exhibited superior mechanical properties. Therefore, the processing route used for heat E4 can be used to manufacture an AMS-4340 ultra-high-strength steel with superior properties compared with those of AMS-4340 prepared by the other investigated routes.

关键词： AMS-4340 steel segregation and homogenization antiflaking treatment electroslag remelting

Comparison of wear behaviour of LM13 Al−Si alloy based composites reinforced with synthetic(B_(4)C)and natural(ilmenite)ceramic particles

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Transactions of Nonferrous Metals Society of China 2021年第12期31卷 3613-3625页

作者： Rahul GUpTA Tarun NANDA o.p.pandey Mechanical Engineering Department Thapar Institute of Engineering and TechnologyPatiala 147004PunjabIndia School of physics and Materials Science Thapar Institute of Engineering and TechnologyPatiala 147004PunjabIndia

Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was *** different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).optical micrographs showed uniform dispersion of reinforced particles in the matrix *** particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of *** reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial *** sliding wear behaviour of composites was significantly improved as compared to base *** low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in *** the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of ***,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very ***,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.

关键词： aluminium matrix composites ilmenite boron carbide particle-reinforcement wear test tribolayer XRD analysis SEM−EDS

Influence of Metal oxides on the Arc Erosion Behaviour of Silver Metal oxides Electrical Contact Materials

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Journal of Materials Science & Technology 2004年第1期20卷 49-52页

作者： p.Verma o.p.pandey A.Verma School of physics and Material Science Thapar Institute of Engineering and Technology Patiala-147004 IndiaSchool of Physics and Material Science Thapar Institute of Engineering and Technology Patiala-147004 IndiaMaterials Science and Technology Division Thapar Centre for Industrial Research and Development Patiala-147004 India

In the present work investigations have been made to see the role of metal oxides on the performance of the silver metal oxides electrical contact materials. Silver metal oxide materials of three different compositions Ag-10Cdo, Ag-7.6Sno2-2.3ln2o3 and Ag-10Zno were prepared by internal oxidation process under identical processing conditions. These materials were tested for electrical conductivity, hardness, and erosion loss. performing an accelerated test on the actual contactor assessed the electrical performance, involving erosion loss and temperature rise of the processed materials. The arc-eroded surface was characterized under scanning electron microscope. The study of the eroded surfaces of contacts indicates that the thermal stability of metal oxides depends on nature of silver-metal oxide interface and their mode of erosion. An attempt is made to correlate the surface features of the eroded contacts with the thermal stability of metal oxides.

关键词： Contact material Microstructure Erosion rate

one Step Synthesis and Growth Mechanism of Carbon Nanotubes

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Journal of Materials Science & Technology 2014年第2期30卷 112-116页

作者： Akshay Kumar K.Singh o.p.pandey Sri Guru Granth Sahib World University School of physics and Materials Science Thapar University

A simple one step, reproducible, synthesis route for carbon nanotubes was proposed. No external catalyst was used for the synthesis. These nanotubes were obtained after decomposition of acetone at 650 ℃ in a specially designed autoclave. The pressure generated due to decomposition of acetone played a vital role in the synthesis. The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3-14 nm. The thermo gravimetric analysis showed 3% weight loss below 500 ℃; the content of amorphous carbon is very less. The growth mechanism of CNTs was also proposed in the present paper.

关键词： Nanostructures Chemical synthesis Electron diffraction Raman spectroscopy Defects

First observation of microspherule from the infratrappean Gondwana sediments below Killari region of Deccan LIp,Maharashtra(India) and possible implications

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Geoscience Frontiers 2019年第6期10卷 2281-2285页

作者： G.parthasarathy o.p.pandey B.Sreedhar Mukund Sharma priyanka Tripathi Nimisha Vedanti CSIR-National Geophysical Research Institute Hyderabad500007India National Institute of Advance Studies School of Natural Sciences and EngineeringIndian Institute of Science CampusBengaluru560012India CSIR-Indian Institute of Chemical Technology Hyderabad500007India Birbal Sahni Institute of palaeosciences 53 University RoadLucknow226007India presently at Banaras Hindu University VaranasiIndia Geological Survey of India BandalagudaHyderabad50068India

A rare occurrence of a microspherule has been found in the infratrappean sediments,encountered below338 m thick Deccan volcanic cover in KLR-1 scientific borehole,drilled in the epicentral zone of the 1993 Killari earthquake(Maharashtra,India).palynological studies of the sediments indicate their age as Early permian(Asselian,298-295 Ma) for *** electron microscope studies reveal that the spherule from the infratrappeans,is having a similar composition to that of the Neoarchean amphibolite to granulite facies mid crustal *** spherule is non-spherical in nature,containing mostly Feo(10.70±0.20 wt.%),Cao(13.8±0.5 wt.%),Al203(7.78±0.30 wt.%),Mgo(6.47±0.3 wt.%),Si02(47,46±0.50 wt.%),Ti02(2.47±0.3 wt.%).K20(1.89±0.20 wt.%).and Cl(0.33±0.05 wt.%).Since the Fe composition of the spherule is almost same as the basement rock(10.5 wt.%),and the chlorine content is also in the same range as the basement(0.04-0.24 wt.%),it would suggest possibility of an extraterrestrial impact over the Indian terrain during the erstwhile Gondwana sedimentation period that may be associated with the permian-Triassic mass extinction,the most severe one in the Earth's history.

关键词： Deccan trap Killari borehole Microspherules Condwana sediments Tectonics p-T impact

Thermodynamic Analysis of Ag_3Ge phase Formation

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Journal of Materials Science & Technology 1997年第6期13卷 524-526页

作者： o.p.pandey(School of Basic and Applied Sciences, Thapar Institute of Engineering and Technology patiala-147 001, India )S.N.ojha and S.Lele(Dept. of Metallurgical Engineering, Banaras Hindu University, Varanasi-221 005, India) School of Basic and Applied Sciences Thapar Institute of Engineering and Technology Patiala-147 001 India Dept. of Metallurgical Engineering Banaras Hindu University Varanasi-221 005 India

In the present work a thermodynamic model is presented for the nucleation of metastable Ag3Ge phase from the undercooled melt in Ag-Ge alloy system. It is shown that under kinetically induced favourable condition, nucleation of a single phase compound with an approximate stoichiometry Ag3Ge has greater affinity for nucleation over Ag and Ge based phases requiring diffusion in the liquid.

关键词： Ag AIME Ge

Multi-wavelength nanowire micro-LEDs for future high speed optical communication

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opto-Electronic Advances 2024年第3期7卷 1-3页

作者： Ayush pandey Zetian Mi Department of Electrical Engineering and Computer Science University of MichiganAnn ArborMI 48109USA

The future of optoelectronics is directed towards small-area light sources,foremost being ***,their use has been inhibited so far primarily due to fabrication and integration challenges,which impair efficiency and ***,bottom-up nanostructures grown using selective area epitaxy have garnered attention as a solution to the aforementioned *** Fu *** used this technique to demonstrate uniform p-i-n core-shell InGaAs/Inp nanowire array light emitting *** devices are capable of voltage and geometry-controlled multi-wavelength and high-speed *** publication accentuates the wide capabilities of bottom-up nanostructures to resolve the difficulties of nanoscale optoelectronics.

关键词： communication high operations

Understanding poromechanical response of a biogenic coalbed methane reservoir

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International Journal of Coal Science & Technology 2024年第3期11卷 32-50页

作者： Rohit pandey Satya Harpalani Virginia Tech BlacksburgUSA Southern Illinois University CarbondaleUSA

Biogenic coalbed methane(BCBM)reservoirs aim to produce methane from in situ coal deposits following microbial conversion of *** of BCBM reservoirs requires economic methane production within an acceptable *** work reported here quantifies the findings of previously published qualitative work,where it was found that bioconversion induces strains in the pore,matrix and bulk *** imaging and dynamic strain monitoring techniques,the bioconversion induced strain is quantified *** understand the effect of these strains from a reservoir geomechanics perspective,a corresponding poromechanical model is ***,findings of imaging experiments are validated using core-flooding flow ***,expected field-scale behavior of the permeability response of a BCBM operation is modeled and *** results of the study indicated that,for Illinois coals,bioconversion induced strains result in a decrease in fracture porosity,resulting in a detrimental permeability drop in excess of 60%during bioconversion,which festers itself exponentially throughout its producing *** indicate that reservoirs with high initial permeability that will support higher Darcian flowrates,would be better suited for coal bioconversion,thereby providing a site-selection criteria for BCBM operations.

关键词： Coal bioconversion poromechanical model Reservoir response Bioconversion induced strain