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Microstructure evolution and mechanical property of cu-15Ni-8Sn-0.2Nb alloy during aging treatment

Journal of Materials Science & Technology 2021年第27期86卷 227-236页

作者： Nan Wang Yidi Shen Qi An Kolan Madhav reddy Mingjiang Jin Rajamallu Karre Xiaodong Wang State Key Laboratory of Metal Matrix composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200240China chemical and Materials Engineering Department University of NevadaRenoNVUSA Institute of Phase Transformation and complex Microstructure School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200240China

Aging treatment of cu-based alloys is essential to enhance their strength that is desirable for their extensive engineering applications in electrical industry,whereas the underlying mechanism of strengthening is essential for massive manufacturing of these ***,the microstructure evolution of a supersaturated solid solution cu-15Ni-8Sn-0.2Nb alloy aged at 400℃for different time was characterized at atomic scale using state-of-the-art transmission electron microscopy(TEM)and the corresponding mechanical property was also *** results reveal that the modulated structure,DO_(22)/L1_(2)ordering,and discontinuous precipitation(DP)appeared in the advances of aging *** the early stage of aging treatment,component modulation waves and satellite spots appeared from spinodal decomposition and the modulation wavelength was identified in the range of 1-7 *** the modulated structures formed-poor-rich solute regions,of which DO22ordering was present in the Ni-poor region while L1_(2)ordering appeared in the Ni-rich *** sequence of ordering precipitates was further verified by density functional theory(DFT)***,orientation relationships and interfacial structures between DO_(22),L1_(2)phases and the parent matrix were *** measured hardness of alloy reached a maximum value of 335 HV after aging for 120 min due to the coherence between the two ordering phases and *** results illustrated the importance of aging on structural evolution and mechanical property of cu-15Ni-8Sn alloy at various heat treatment stages,which could potentially help in manufacturing promising alloys for their extensive engineering applications.

关键词： cu-alloy Aging Precipitates Transmission electron microscopy Density functional theory

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Kinetic features of xylan de-polymerization in production of xylose monomer and furfural during acid pretreatment for kenaf,forage sorghums and sunn hemp feedstocks

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International Journal of Agricultural and Biological Engineering 2014年第4期7卷 86-98页

作者： Srinivas reddy Kamireddy Evguenii I.Kozliak Melvin Tucker Yun Ji Department of chemical Engineering University of North DakotaGrand ForksND 58202USA Department of chemistry University of North DakotaGrand ForksND 58202USA National Bioenergy center National Renewable Energy LaboratoryGoldenCO 80401USA

A kinetic study of acid pretreatment was conducted for sorghum non-brown mid rib(SNBMR)(Sorghum bicolor L Moench),sorghum-brown mid rib(SBMR),sunn hemp(crotalaria juncea L)and kenaf(Gossypiumhirsutum L),focusing on rates of xylose monomer and furfural *** kinetics was investigated using two independent variables,reaction temperature(150°c and 160°c)and acid concentration(1 and 2 wt%),with a constant dry biomass loading of 10 wt%and a treatment time up to 20 min while sampling the mixture every 2 *** experimental data were fitted using a two-step kinetic model based on irreversible pseudo first order kinetics at each *** kinetic orders on the acid concentration,ranging from 0.2 to>3,were observed for both xylose and furfural formation,the values depending on the *** crystallinity index of raw biomass was shown to be a major factor influencing the rate of both xylose and furfural formation.A positive correlation was observed between the activation energy and biomass crystallinity index for xylose formation.

关键词： acid pretreatment sunn hemp sorghum brown-mid rib(BMR) sorghum non brown-mid rib(SNBMR) kenaf reaction kinetics activation energy reaction order

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Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing-An experimental study and analytical approach

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Defence Technology（防务技术） 2016年第1期12卷 25-31页

作者： I.SUDHAKAR G.MADHUSUDHAN reddy K.SRINIVASA RAO department of mechanical engineering mvgrceVizianagaramIndia defence metallurgical research laboratory HyderabadIndia department of metallurgical engineering andhra universityVisakhapatnamIndia

High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir *** performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was

关键词： AA7075 aluminium alloy Friction stir processing(FSP) Surface metal matrix composite(SMMc) Boron carbide(B4c) Ballistic performance Target

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Expeditious method for the synthesis of novel 2,3,5,6-tetrahydrobenzo[g] [1,3,5]oxadiazocine-4-thiones linked with isoxazole

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chinese chemical Letters 2008年第12期19卷 1415-1418页

作者： E.Rajanarendar A.Siva Rami reddy M.Srinivas Department of chemistry Kakatiya UniversityWarangal 506009India

Synthesis of novel 3-aryl-5-（3,5-dimethylisoxazol-4-yl）-2,3,5,6-tetrahydrobenzo[g][1,3,5],oxadiazocine-4-thiones 5 has been accomplished from 3,5-dimethylisoxazol-4-amine 1 by condensation with salicylaldehydes, followed by reduction, treatment with aryl isothiocyanates and subsequent smooth ring closure via acetal formation in the presence of formaldehyde.

关键词： Isoxazolyl-2,3,5,6-tetrahydrobenzo[g]oxadiazocine-4-thiones Ring closure New methodology

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Enhanced resistive switching properties of HfAlOx/ZrO2- based RRAM devices

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Progress in Natural Science:Materials International 2022年第5期32卷 602-607页

作者： P.R.Sekhar reddy Venkata Raveendra Nallagatla Yedluri Anil Kumar G.Murali School of Material Science and Engineering Pusan National University Department of Physics and Oxide Research centre Memory and Catalyst Research Center Hankuk University of Foreign Studies Materials center Leoben Forschung GmbH Department of Physics United Arab Emirates University Department of Polymer Science and Engineering Department of IT-Energy Convergence (BK21 FOUR) Chemical Industry Institute Korea National University of Transportation

Resistive Random-Access Memory(RRAM) devices are recognized as potential candidates for next-generation memory devices, due to their smallest cell size, high write/erase speed, and endurance. Particularly, the resistive switching(RS) characteristics in oxide materials have offered new opportunities for developing cMOScompatible high-density RRAM devices. In this study, the RS behavior of HfAlOx/ZrO2thin films sandwiched structure between TiN bottom electrode and Au top electrodes were investigated. It was found that Au/HfAlOx/ZrO2/TiN stacks were superior in terms of RS performance when compare to Au/HfAlOx/TiN memory stacks. The devices demonstrated a good resistance ratio of high resistance state and low resistance state ～103 for Au/HfAlOx/TiN and ～105 for Au/HfAlOx/ZrO2/TiN stacks, respectively. Both stacks showed good retention characteristics(>104s) and endurance(>103cycles). The experimental current-voltage characteristics fitted with different conducting mechanisms, the linear lower bias region is dominated by ohmic conductivity, whereas the non-linear higher bias region was dominated by space-charge limited current conduction mechanism.

关键词： Nonvolatile memory RRAM Resistive switching mechanism Atomic layer deposition current conduction mechanism

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Perturbations in Earth's Atmosphere over An Indian Region during the Total Solar Eclipse on 22 July 2009

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Journal of Meteorological Research 2019年第4期33卷 784-796页

作者： S.B.Surendra PRASAD Vinay KUMAR K.Krishna reddy S.K.DHAKA Shristy MALIK M.Venkatarami reddy U.Murali KRISHNA Semi-arid-zone Atmospheric Research centre SARc Department of Physics Yogi Vemana University Radio and Atmospheric Physics Lab Rajdhani College University of Delhi Department of Applied Physics Delhi Technical University

During a total solar eclipse(TSE) on 22 July 2009, atmospheric perturbations were monitored from the surface to thermosphere to understand TSE’s impact on the meteorological(temperature, relative humidity, wind speed, and wind direction) and chemical(O3and NOx) parameters around Kadapa(14.28°N, 78.42°E), a tropical semi-arid region of India. For this purpose, an experiment was conducted at Yogi Vemana University campus, Kadapa, India, to measure the temperature, wind speed, wind direction, and concentrations of ozone(O3), NO, NO2, and NOxby using the automatic weather station(AWS) and O3analyzer. On the eclipse day(22 July 2009), the surface observations at Kadapa showed a reduction in temperature(about 1.1°c) because of the solar insulation. comparison of the thermal,dynamical(wind), and chemical parameters on the TSE day with control days [preceding(21 July 2009) and succeeding(23 July 2009) the TSE] illustrated the influence of solar eclipse. During the eclipse period, the O3mixing ratio decreased, while NO2and NOxincreased; however, NO remained unchanged. In addition, radio occultation(RO)temperature profiles from constellation Observing System for Meteorology, Ionosphere, and climate(cOSMIc)/Formosat Satellite Mission(FORMOSAT-3) and Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics(TIMED) satellites were utilized to understand the impact of TSE on dynamics of the middle and upper atmosphere from tropopause to the thermosphere. High vertical resolution cOSMIc observations revealed that during the solar eclipse, tropopause was cooler with twin peaks(double tropopause). The lower thermosphere between 110 and 130 km became warmer during the TSE, which might be caused by the dynamical response of the atmosphere in this region to the solar eclipse. The experimental data have provided very fine-scale variations of the atmospheric parameters both in time and height and also constituted a new set of results on TSE for further research.

关键词： total solar eclipse(TSE) atmospheric perturbations tropopause dynamics cOSMIc/FORMOSAT-3 satellite radio occultation(RO) observations

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The Efficacy of Debridement, Fusion and Anterior Stabilization for Spinal Tuberculosis

The Efficacy of Debridement, Fusion and Anterior Stabilizati...

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作者： Madhukar reddy Mosali 苏州大学

学位级别：硕士

STUDY DESIGN:A retrospective study to analyze the clinical outcome of spinal tuberculosis （TB） treated with anterior debridement and spinal fusion. OBJEcTIVE:To evaluate the efficacy of treatment results in patients with anterior surgical treatment of spinal TB at thoracic and lumbar region. METHODS:21cases of active tuberculosis of the spine were diagnosed and treated between January2006and June2011. Among them,11were males and10females with the mean age56.6（range23to81）, of which13patients were diagnosed with L-TB,7with T-TB and1with TL-TB. All the patients received a short course of anti-TB combination drug therapy for a minimum of2weeks pre-operatively and underwent anterior radical debridement/+auto grafting （with or without titanium mesh cage）+internal fixations. Patients were evaluated both before and after based on radiological findings, blood parameters, kyphotic angles and Frankel grading system. RESULTS:All the patients had obvious relief of the pain and hematological parameter ESR became normal from42.4±27.5mm/hr pre-operatively to17.5±11.8mm/hr within3.2months after surgery. Pre-operative kyphotic angle was16.8°±11.2which was corrected to13.2°±9.9after the surgery and to the recent follow-up14.7°±9.8.14patients were included in Frankel grading B, c and D, of which13patients improved by1or2grades. Solid bony fusion was seen in all cases at8-12months. No reoccurrence of the infection, graft related problems, neurological deterioration, progression of kyphosis and wound infections were encountered. cONcLUSION:Our results demonstrate that anterior radical debridement, auto graft and anterior instrumentation is an effective technique for the treatment of spinal tuberculosis.

关键词：脊柱结核临床效果前路病灶融合治疗疗效评价

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Improvement of Microstructure and Mechanical Behavior of Gas Tungsten Arc Weldments of Alloy c-276 by current Pulsing

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Acta Metallurgica Sinica(English Letters) 2015年第2期28卷 208-215页

作者： M.Manikandan N.Arivazhagan M.Nageswara Rao G.Madhusudhan reddy School of Mechanical and Building Sciences VIT University Defence Metallurgical and Research Laboratory

Superalloy c-276 is known to be prone to hot cracking during fusion welding by Gas Tungsten Arc method. Microsegregation occurring during cooling of fusion zone with consequent appearance of topologically close-packed phases P and IX has been held responsible for the observed hot cracking. The present work investigated the possibility of suppressing the microsegregation in weldments by resorting to current pulse. Weldments were made by continuous current gas tungsten arc welding and pulsed current gas tungsten arc welding using ERNicrMo-4 filler wire. The weld joints were studied with respect to microstructure, microsegregation, and mechanical properties. Optical microscopy and scanning electron microscopy were employed to study the microstructure. Energy-Dispersive X-ray Spectroscopy was carried out to evaluate the extent of microsegregation. Tensile testing was carried out to determine the strength and ductility. The results show that the joints fabricated with pulsed current gave rise to narrower welds with practically no heat affected zone, a refined microstructure in the fusion zone, reduced microsegregation, and superior combination of mechanical properties.

关键词： Alloy c-276 Pulsed current gas tungsten arc welding Microsegregation

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Liver transplantation for metastatic neuroendocrine tumor: A case report and review of the literature

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World Journal of Gastroenterology 2005年第48期11卷 7676-7683页

作者： Wojciech c Blonski K Rajender reddy Abraham Shaked Evan Siegelman David c Metz Department of Gastroenterology and Hepatology Division of Gastroenterology Department of Surgery Department of Magnetic Resonance Imaging Division

Neuroendocrine tumors are divided into gastrointestinal carcinoids and pancreatic neuroendocrine tumors. The WHO has updated the classification of these lesions and has abandoned the term ＂carcinoid＂. Both types of tumors are divided into functional and non-functional tumors. They are characterized by slow growth and frequent metastasis to the liver and may be limited to the liver for long periods. The therapeutic approach to hepatic metastases should consider the number and distribution of the liver metastases as well as the severity of symptoms related to hormone production and tumor bulk. Surgery is generally considered as the first line therapy. In patients with unresectable liver metastases, alternative treatments are dependent on the type and the growth rate. Initial treatments consist of long acting somatostatin analogs and/or interferon. Streptozocin-based chemotherapy is usually reserved for symptomatic patients with rapidly advancing disease, but generally the therapy is poorly tolerated and its effects are short-lived. Locoregional therapy directed such as hepatic-artery embolization and chemoembolization, radiofrequency thermal ablation and cryosurgery, is often used instead of systemic therapy, if the disease is limited to the liver. However, liver transplantation should be considered in patients with neuroendocrine metastases to the liver that are not accessible to curative or cytoreductive surgery and if medical or Iocoregional treatment has failed and if there are life threatening hormonal symptoms. We report a case of liver transplantation for metastatic neuroendocrine tumor of unknown primary source and provide a detailed review of the world literature on this controversial topic.

关键词： Liver metastases, Neuroendocrine tumors Liver transplantation

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Gas tungsten arc welding of ZrB_2-Sic based ultra high temperature ceramic composites

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Defence Technology（防务技术） 2015年第3期11卷 188-196页

作者： R.V.KRISHNARAO G.MADHUSUDHAN reddy Defence Metallurgical Research Laboratory

The difficulty in fabricating the large size or complex shape limits the application of ZrB2-Sic composites. Joining them by fusion welding without or with preheating, controlled cooling under protective gas shield leads to thermal shock failure or porosity at the weld interface. In the present work, a filler material of(ZrB2-Sic-B4c-YAG) composite with oxidation resistance and thermal shock resistance was produced in the form of welding wire. Using the filler, gas tungsten arc welding(GTAW) was performed without employing preheating, post controlled cooling and extraneous protective gas shield to join hot pressed ZrB2-Sic(ZS), and pressureless sintered ZrB2-Sic-B4c-YAG(ZSBY) composites to themselves. The fusion welding resulted in cracking and non-uniform joining without any filler material. The weld interfaces of the composites were very clean and coherent. The Vickers micro-hardness across the weld interface was found to increase due to the increase in the volume % of both Sic and B4c in the filler material. The shear strength of the weld was about 50% of the flextural strength of the parent composite.

关键词：陶瓷基复合材料焊接界面钨极氩弧焊气体保护超高温填充材料 ZrB2 形状复杂

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