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Welcome to the Website of Dr. -Ing. Venkata Sai Kiran Chakravadhanula
Transmission Electron Microscopy and Spectroscopy of Al-rich Ti-Al alloys. Initiation of new projects, collaborarations and establishment of electron tomography technique for the institute.
Synthesis and characterization of swift heavy ion (SHI) beam irradition of metal-polymer and metal-oxide based nanocomposites for optical applications.
Education
PhD / Doctoral Degree (Dr. -Ing.)
Institute for Materials Science, Christian Albrechts University (CAU), Kiel, Germany - April
2011
Vapor Phase Deposition of Functional Nanocomposites and their Modification by Ion Beam Irradiation
Masters Degree in Materials Science and Engineering
Technical Faculty, Christian Albrechts Universität Kiel, Germany - 2003 - 2005
Masters Thesis: Synthesis and Characterization of 2D and 3D Au/Ag Polymer Nanocomposites for Optical Applications
Bachelors Degree in Metallurgy and Materials Technology (B.Tech)
Mahatma Gandhi Institute of Technology (MGIT), Jawaharlal Nehru Technological University (JNTU), Hyderabad, 1999 - 2003
Bachelor Thesis: Synthesis of Amorphous Carbon and Densification by Chemical Vapor Infiltration, carried out at Bhabha Atomic Research Centre (BARC), Mumbai, India
ABAP Gold Medal for Advanced Research in Nanoscience and Technology
2017
Outstanding Scientist of the Helmholtz Institute Ulm (HIU), Karlsruhe Institute of Technology (KIT)
2016
Outstanding International Student Award - Deutscher Akademischer Austauschdienst e.V. (DAAD)
2008
Memberships
Supporting the promotion of the development and acceptance in the field
Elected member of the First Convent of the Scientists at the Karlsruhe Institute of Technology 10/2015 - 11/2017
Member of European Microscopy Society (EMS)
Member of Deutschen Gesellschaft für Elektronenmikroskopie e.V. (DGE)
Life Member - Indian Institute of Metals (IIM)
Life Member - Electron Microscopy Society of India (EMSI)
Life Member - Materials Research Society of India (MRSI)
Life Member - Powder Metallurgy Assiciation of India (PMAI)
Life Member - Magnetic Society of India (MSI)
Patents
Stimulating and promoting research in the field
International Patent, “Omni-directional Transparent Conducting Metal based Plasmonic Nanocomposite”: DE 10 2010 050 110.7.
Grants
Government Grants are through government agencies to projects that benefit the public through peer-reviewed selection process to researchers or organisations
Deutsche Forschungsgemeinschaft/German Research Foundation (DFG) Grant - FOR 2093 : Principal Investigator for “Nanostructure of Materials for Memristive Switching Processes - In situ (S)-TEM”. # CH 1492/1-1.
Software / Hardware Expertise
Computer hardware and software are additinal tools that support us in daily R&D activities
Advanced Diploma in Software technology from Computer Management Corporation (C.M.C.) of India Pvt. Ltd, India 2000-2003.
Extensive knowledge in C, C++, Windows 95, XP, 7,8, Mac OSX, Windows-Server and associated Software-Installations, Visual Studio, Unix, Java, Oracle, SQL, etc.
Extensive experience in Server and Firewall - maintenance (Windows Server, Synology, Pfsense), Literature searching and Management software(Courses also offered).
Design and maintenance of Internet-site: http://www.cvskiran.com.
Office programs & Graphical programs (CorelDraw, Digital Micrograph, Titan imaging and analysis - TIA, ImageJ, JEMS, CRISP, Calidris, Diamond).
Research
Pursuing research questions of scientific significance cuts across and combines two, three, or multiple areas. In this process, following areas are the research areas in which work has been carried out.
In situ Electron Microscopy is the emerging field of electron microscopy involving electron microscopy under dynamic conditions with various stimuli. Based on these stimuli used, a variety of techniques/method are divided and are termed as in situ TEM techniques. Research and Developmental activities in these fields are gaining increasing importance, as the demands from the synthesis and fabrication groups increase, requiring the dynamics of materials modifications during their processes, understanding the basics of the process, therby leading towards an efficient material, its process and its properties. As an example, the video below depicts in situ TEM in liquids towards understanding the growth of Ag within a AgNO3 solution using an Posseidon single tilt sample holder from Protochips Inc. More information: Link
In situ Transmission Electron Microscopy of Memristive Materials
Memristors are nanoscale resistive switching devices. Memristors have been of huge interest for memory, logic and neuromorphic applications in the recent times. Generally, their switching effects in dielectric-based devices are assumed to be caused by conducting filament formation across the electrodes. But the nature of the filaments, their growth mechanisms and dynamics are in huge debate, which demand in situ high spatial resolution characterization techniques. In situ transmission electron microscopy with its imaging, structural and compositional analysis at the nanoscale is an optimum technique to understand the growth mechanisms and dynamics. Through systematic ex situ and in situ TEM studies on nanoscale devices under various programming conditions, the underlying mechanisms can be identified. The results obtained through deserve particular attention for continued device optimization.
Transmission Electron Microscopy of Battery Materials
Research in the field of energy storage systems has gained huge importance in all sectors of life. Batteries contribute towards the major systems of Energy strorage systems. Improving the cycling capabilities, energy storage capacities, safety and security are the primary aspects which need a deeper understanding of the individual components of the battery i.e., Electrodes and Electrolytes. Presently there is exploding research towards development of new battery chemistries, new nanostructures of the individual components towards meeting the energy storage demands of the world. Therby leading to huge demand for high spatial resolution characterization of such components not only in the as-prepared state but also during various stages of cycling or even after cycling. In all the aforementioned cases, TEM offers a good choice, towards acheiving high spatial resolution. But the expectations of the researchers towards TEM has also been increasing with the advances of in situ electron microscopy, towards understanding the morphological, structural and compositional changes during the process of charging and discharging. For this purpose, the effective dose of the individual components of the battery are pivotal, ignoring which leads to the analysis of electron beam modified components as components of the battery. Thus modifying the complete electrochemistry of the battery. Analysis of individual components of the battery, their beam stability and the critical electron dose under varying imaging techniques become the key parameter. Hence understanding the radiation damage (either Radiolysis, Knock-on-damage or sputtering and heating) leading to either crystallization, amorphization or removal of material remains pivotal. Understanding this thereby leads towards "Better Materials for a Bettery Battery thereby Better Energy Storage System for a Better Tomorrow".
In situ Transmission Electron Microscopy of Battery Materials
Research in the field of in situ energy storage systems has gained huge importance in the present decade where batteries, besides being pivotal, also needs improving in their cycling capabilities, energy storage capacities, safety and security which need a deeper understanding of the interfaces of the battery i.e., Anode-Electrolyte and Cathode-Electrolyte. Many research groups around the world try to understand this towards the development of new battery chemistries, new nanostructures of the individual components towards meeting the energy storage demands of the world. TEM, being a high spatial resolution characterization tool enables the understanding of the variations or modifications at the nano-scale. Together with in situ sample holders with continous imaging during any experiment, high spatial resolution involves higher electron doses, increasing the effective dose applied on the system that might lead to radiation damage. Towards understanding the morphological, structural and compositional changes during the process of charging and discharging during an in situ TEM electrochemical cycling experiments, electron microscopists might be misled towards studying the electron beam modified materials and their electrochemical cycling. Effectively the calculation of the critical dose of the individual components of the battery in separate experiments are pivotal. Ignoring this might leads to the analysis of electron beam modified components as components of the battery, thereby studying the electrochemistry of the electron beam modified battery. More information: Link
Characterization of Traditional Indian Materials
Indian rich traditions have a variety of cultural heritage. Traditionally there have been a healthy era of non-processed (traditionally-processed) materials, used in day to day activities. Many of these materials have been used even today in villages, because of the knowledge given by the ancestors. Unfortunately less scientific evidence exists. An effort is here made to correlate the known functionality or the properties with a scientific understanding by studying the morphology, structure and chemical compositon of the corresponding materials.
Indexing, Mapping and Evaluating the Indian Electron Microscopy Facilities
Based on the understanding of various EM facilities around the world and the experience gained in establishing collaborations, I myself initiated a project on the evaluation of EM characterization facilities in India in a view to enhance the future perspective and dream of establishing a network in addition towards establishing state-of-the-art characterization facility for India. This report will be published and would aid towards this dream. In the google map above you find all the FEI TEM's-Blue Color, JEOL TEM's-Green Color and Hitachi TEM's-Brown Color. The EMSI zonal headquarters are also available, but one has to open the flap out and select EM Soceities and unselect the TEM.
Transmission Electron Microscopy of Biological Materials
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Nanoscale Characterization of Ayurvedic Bhasmas
Ayurvedic medicines are nano-/micro- materials made by all-green technologies and are the Traditional Indian Medicine. Actual prepration strategies and recepies are mentioned in the vedas. This alternate medicine has proved to be very helpful in treating diseases. But characterization of such materials involves high resolution techniques in addition to bulk characterization techniques. Morphology, Structure and Compositional analysis is pivotal towards the establishment of standards for the Ayurvedic medicines or "Bhasmas".
Lorentz Transmission Electron Microscopy of Magnetic Materials
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Transmission Electron Microscopy of Nanomaterials
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Transmission Electron Microscopy of Ti36Al62Nb2
Al-rich Ti-Al alloys attracted some attention during the past years due to the possibility of their application as light-weight, high-performance materials at elevated temperatures. The effect of the addition of Nb to Al-rich Ti-Al alloys has been studied for Ti36Al62Nb2 by a combined approach of transmission electron microscopy (TEM) techniques for unraveling the structure and composition at the nanoscale. Structural analyses on as-cast ternary alloys revealed the presence of h-TiAl2-, Ti3Al5- and ?-TiAl-type phases. After heat treatment, phase transformations like the replacement of the metastable h-TiAl2-type by the stable r-TiAl2-type were identified. Additionally, changes of the microstructural features like the formation of interfaces with different orientation relationships are apparent. The orientation and interfacial relationships involved are compared to those of binary Ti-Al alloys rich in Al. More information: Link
In situ Thermal Transmission Electron Microscopy
A study involving the in situ heating of the TiO2 based nanocomposites in the TEM confirms the absence of the formation of TiO unlike the SHI irradiation. Changes of the microstructure of the nanocomposite film upon annealing allowed demonstrating the absence of the formation of TiO but rather only the crystallization of the TiO2.
Electron Tomography of Nanocomposite Materials
Unlike the case of polymers, in the case of Ag nanoparticles on TiO2, segregation of the clusters on the surface also provides a fast pathway for Ostwald ripening without any restrictions by elastic distortions at least for those clusters which are in direct contact with the surface. 3D electron tomography was employed on the TiO2 based nanocomposite thin films to explain the two step model for the particle size distribution. First step involved the formation of small nanoparticles during vacuum phase deposition or on the growing surface. Second step after the deposition process involved the formation of larger particles through particle coarsening by Ostwald ripening and surface segregation. More information: Link
Irradiation of Materials and their Characterization: Materials' response to extreme Environment
Tuning the optical properties of nanocomposites can be achieved by using swift heavy ion irradiation (SHI) of the nanocomposites. The SHI beamlines from both the Hahn Meitner Institute in Berlin, Germany and the Inter University Accelerator Center in New-Delhi, India, were employed in this work. The TiO phase formation on SHI irradiation with increasing fluence was understood by the interaction of two different counteracting mechanisms, where at lower ?uences, the tendency towards the formation of TiO existed with the larger unaffected areas and at higher fluences, the destruction of the evolved TiO phase into fragments was evident. This served as an evidence for the counter play between "hit" and "no hit", "single hit" and "multiple hits" processes. More information: Link
Synthesis and Characterization of Nanocomposite Thin Films
Nanocomposite thin film coatings with a wide range of metal volume fractions were prepared by co-sputtering of TiO2/Teflon and Ag/Au/Cu from two different magnetron sources simultaneously in a home made deposition chamber under high vacuum conditions. Two different types of host materials a polymeric (PTFE) and a ceramic (TiO2) were studied in this work. Morphology, optical and antibacterial properties of these nanocomposites were examined. The formation of metallic nanoparticles upon vapor phase co–deposition of a metal and a dielectric matrix component can be understood in terms of the high cohesive energy of the metal and the low metal-matrix interaction energy which lead to high metal atom mobility on the growing composite surface and metal aggregation whenever metal atoms encounter each other or a metal cluster. In addition, efforts towards tuning of the double plasmon resonances by tailoring the dielectric separation were carried out. Bimetallic nanocomposites based on sandwich geometry in polymer system, the changes in the particle plasmon spectra of sandwiched Au nanoclusters as a result of the presence of Ag nanoclusters in their vicinity and vice versa was studied. Also, the optimum dielectric barrier thickness for the observation of equal intensity double plasmon resonance was reported. Functionality of the nanocomposites in terms of the antibacterial properties was studied. Cultures of B.megaterium, S.aureus, S.epidermidis and E.coli were used to study the effect on the Ag-TiO2 nanocomposites. Additionally, silver ion release studies were carried out at dfferent MVFs by using X-ray photoelectron and UV-Vis/NIR spectroscopies. More Information: Link
Links
Links form an important part of the network towards a huge timely resource.
