My degree paper topic is defined as the multi-scale thermal transport modeling for nanostructured electrodes. The major work is inspired by the process of my literature review of  nano material and the paper Combined Microstructure and Heat Conduction Modeling of Heterogeneous Interfaces and Materials . The content is listed below:

1. Relate the micro structure to the transport properties for nano electrode. Understanding how specific nano structure like coating, core-shell, hierarchical will change the thermal transport.
2. Choose appropriate parameter transmission framework (network, HMM and others) for micro to meso and macro. Now the candidate model is multi-scale network method.   
3. Using macro scale simulation (COMSOL) to analyze how the micro and mesoscopic geo parameter will affect the whole battery performance.

Research Memos

1.    Multi-scale informatics

With the emerging of nano science, scientist collected a lot of interesting information from micro structures, which is  . However, the engineering paradigm is still macro modeling. How to accommodate the new information became a critical issue. I am building up the "multi-scale informatics" thinking.  my idea about material transport properties while doing senior design. I am trying to link the nano structure material transport properties to macro properties. But I just started and looking forward to discover more topics to talk about. 


2.   Complex system and design optimization Also , I am interested in thinking about engineering from complex system and using data analysis . Complexity is one of the major characteristics for the future technology development. Using data tools to facilitate science exploration and engineering design is my prospective for the future. As a consequence, I am reading about graph theories and applied them into a complex network analysis.  You may find it out on my web http://www.letianwang.me/network-analysis.html. I also came up with an idea using data to facilitate the electrode research for Lithium-ion battery: http://www.letianwang.me/engineering-design-for-nano-electrode.html

Four-month Summary
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 In the past four month, I have been absorbing and integrating knowledge and methods in the microscale transport especially in thermal transport and lithium-ion battery.
Recently, I have been getting the fundamental understanding of the design science and social network. This will probably help me to understand the complex social-technical world. 



Lectures and Seminars​
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Jan, 2014
Lecture:      Nanowire Devices for High-Performance Energy Storage
Lecturer:     Liqiang Mai, Professor, WUT-Harvard Joint Nano Key Lab


Dec, 2013
Lecture 1:    Multiscale Simulations and Ultrafast Characterization for Nanoscale Heat Conduction
Lecture 2:    Phase-Change Heat Transfer at Micro/Nanoscale: from Fundamentals to Manufacturable Devices
Lecturer:     Ronggui Yang, Associate Professor, Mechnical Engineering, University of Colorado, Boulder


Nov, 2013
Seminar:     Interfacial Science and Technology in Energy Industry
Lecturer:    Qingxia (Chad) Liu, Professor, Chemical and Materials Engineering, University of Alberta

Oct, 2013
Lecture:      Simulation of thermal and thermoelectric properties of carbon nanomaterials
Lecturer:     S.Watanabe, Department of Material Engineering, The University of Tokyo​




 

No.5 Updates

1. I discussed the transport modeling of Lithium-ion Battery with Dr. Yonghuang Ye in NUS, Singapore. He answered my questions concerning the macro mathematical model of transport in Lithium-ion battery. He thinks there are limited research linking microscale structure and transport.
2. I am doing intern on Innovative Metrics Development in SUTD with the supervision of Prof. Katja Otto. It will deepen my understanding of  how innovative a technology is, thus facilitate my ability to innovate.  My idea to develop an innovation matrix for the nano scale electrode design gained the interest and support from Prof. Jianxi Luo. We will discuss it later.
3. Our team has completed Network Analysis  towards 2014 ICM. It is a challenging problem since none of us had knowledge on network analysis and we need to solve the problem in 4 days in a report. But I found learning new knowledge is not that challenging and understanding the challenge is much more important. It's exciting that Prof. Jianxi Luo working on network analysis are impressed by our solutions and interested in our finding. You can find our more on my site: http://www.letianwang.me/network-analysis.html

Update No.4

1. MCM/ICM contest preparation
2. Thermal Transport Review Paper
3. Nanostructured Electrode Transport

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•  I have been working on the MCM/ ICM (The Mathematical Contest in Modeling and Interdisciplinary Contest in Modeling) held by COMAP in US. Taking part in this contest, I am trying to review and further improve my mathematics at the end of my college life. In another aspect, I am challenging a new topic.
  

•  I noticed the newly released paper Nanoscale thermal transport. II. 2003–2012 by several renowned researchers in thermal transport field.It is a great guidepoint for me to further walk into this field. It had reviewed the interfacial transport, the phonon transport and nano material effects on it, and lastly the experimental advancement. The authors focused on the interfacial transport and offered me a better understanding of how this topic evolved. But unfortunately, I could not master the detailed information, so there is much more to prepare.
  

•  I have  been keep searching detailed research topics for my senior design. I found the paper Combined Microstructure and Heat Conduction Modeling of Heterogeneous Interfaces and Materials by Prof. Fisher gives a good modeling connecting the microstructure and continum theories of transport, which could help me on reserching transport in electrodes. Also, I found what I have learnt in Purdue , the Effective Medium Theories has been used again in this work. Everything is so wonderful!

HIghlights

1. Si-C anodes for high capacity lithium-ion batteries.
   
2. Engineering design and electrode material
   
3. Transport and battery
   

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• Understanding: Si-C is a good starting point to have some understanding of nano fabrication as well as nano transport.
  

1. Silicon has unique semiconductor properties with various applications. Also, silicon fabrication has received benefit from massive production in circuits.
2. Carbon nano materials has great potential to be connecting, supporting and even functional application in nanoscale devices.

• Understanding:  I had some attention put on the supercapacitors. By reading the new released paper on CDI capacitive deionization for water desalination by Prof. Santiago in Stanford. The ion transport method could be borrowed from it. In situ spatially and temporally resolved measurements of salt concentration between charging porous electrodes for desalination by capacitive deionization

• Idea: Electrode material innovation bases on design concepts
  

1. An idea matrix and innovative operator method is described in paper : IDEA MATRIX AND CREATIVITY OPERATOR, Victor Tang, Jianxi Luo, ICED 2013.
2. Silicon-carbon anode geometries follows a matrix + operator pattern.
1. Material Matrix: Si NW, C NW, Si NP, C NP, Si Nanosheet, C Nanosheet.
2. Operator: Addition, subtraction, hierarchical, encapsulation

• Idea: Transport research as well as systematic research in lithium-ion is rare. Two possible topics could be done.
  

1. If we use lithiumnation-delithiumnation model by material science researcher plus transport theories in thermal science, there will be theoretical explanation to the lithium-ion batteries performance.
2. Thermal transport in nanoscale material is not well understood, which is critical for systematical modeling the battery thermal stability.

Outline for this update (Issue 2):

A basic physics concepts and principles in nanoscale solid transport.

B  my senior design topic choice

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A. Physics on Nanoscale Thermal Transports

Content:

1. The online course Thermal Energy at the Nanoscale offered by Prof. Tim Fisher. I am half way in Week 2 lectures.
1. Lecture 1: Lattice Structure, Phonons, and Electron
1. Lattice vibration and phonon (acoustic and optical phonon, intro)
2. Free electron and band theorem (intro)
2. Lecture 2: Carrier Statistics
1. Phonon and electron density of states ( intro)

1. Statistical physics ( Thermodynamics and statistical mehcanics by Wlater Greiner Springer; Introduction to Statistical Physics, Kerson Huang, 2ed)
1. Phase space and entropy
2. Fermi, Bose and Boltzmann system and distribution (classical description, most probable distribution aspect)
3. Ensemble: phase space density and Liouville theorem, the difference of different ensembles.

1. Solid state physics (Chinese-Kun Huang, English-Charles Kittel)
1. Lattice geometry and reciprocal lattice
2. Atomic binding and Crystal

Comments:

1. I found the introduction given by Prof. Fisher is highly condensed. Therefore I have to dilute it by reading several other books. Originally, I planned to took them next term, but now, I need to learn by myself.  Mult-dimensional vacancy on physics is hard, however, since I have such experience working on two projects, I believe it would work out better later.
2.  Apparently, I am still at the entry of the nanoscale thermal transport, where I need to use the combination of quantum mechanics and classical mechanics to understand the transition. I found it interesting to study the evolution of people scientific understanding towards a specific topic. Boltzmann is great but he also has failed hypothesis like ergodic hypothesis.

B. Senior Design on Lithium-Ion Battery Nanostructures:

I reviewed the cathode and anode research progress . In order to be coherent with our lab's work in solar cell, my current focus is on Si-C anodes. The silicon has good lithiation storage ten times of current graphite anode capacity, however it suffers from pulverization caused by its 400% volume change. Carbon material has excellent mechanical flexibility that could support silicon. Also carbon served electron transport pathway to improve the conductivity. Now I am researching on basic fabrication process of current Si-C structure. A more detailed presentation is in preparation.

There are two points that I would love to note.

1. It is good to find out there are research groups in Tsinghua working on silicon and carbon anodes too, which reminds me that searching for possible cooperation is really important especially in the era of  interdisciplinary research. From most innovative researchers experiences, I believe communication and mutation would help to develop unforeseeable solutions to current challenges.
2. This piece of research may not be explorative or deep in theoretic. But considering my previous simulation and modeling work, basic experimental operation and first hand understanding of nanoscale materials would be beneficial to my future research. Also in a long term, it could help me to shorten the bridge of research and technology.  

Here is my recent updates for the past 2-3 weeks.

•  I glad I did finished the graduate school applications before 2014.

• In the long term I would love to understand the microscale transport, and both liquid and solid transport are vital. Due to my department and lab's origin, the focus mainly spin around heat and mass transport. 
  

• Fluid: For me, I had some preparation basing on my undergraduate study. Recently, my interest mainly falls on interfacail phenomena of nanostrucutures. I had read about the papers on following topics:
  

1. Intermolecular forces, which is about the contact angle properties is one factor which comes into heat transfer researcher's view recently due to the emergency of hydrophobic surfaces. I read about the adhesion force of nanostructured surface and droplets with different properties by group in Alberta. It might offer insights on droplet and superhydrophobic surface separation.
2. But for the heat transfer, fluid transport is also important in addition to the intermolecular forces, as Prof. Ronggui Yang's recent discoveries indicated. He found only the combination study of  fluid replenish and intermolecular forces could account for the influence of nanostructure on phase change. He is trying to study droplet spreading on nanostructured surfaces to combine both of two factors. His preliminary work indicates that there are monotonic relationship between the spreading spead and heat flux.
3. A design approach for sustaining vapor phase for a immersed superhydrophobic surface has been reported by Prof. Patankar in Northwestern. This work brings the contact angle research into the more realistic heat transfer application.
4. CNT has hydrophobic properties that transport liquid through its body without frictions, which is studied some time ago by Berkeley. Researchers has demonstrated the  application on water purification and medical injector now. Is
5. Problem A: The importance of active wetting in cooling system. I am not aware of where could the necessity of active on-spot cooling will beat the extra cost it brings.
6. Problem B: The cooling challenge of wearable and flexible electronics devices. The fluid transport as well as interface material are two challenges in my view.

• Solid: I am aware of my lack in higher-level physics. Therefore, my first priority work would be knowledge replenishment.
  

1. I  joined the online course of Thermal Energy at the Nanoscale provided by Prof. Fisher in Purdue. It offered the most important concepts within short 5 weeks.
2. I find using LAMMPS and Material Studio to simulate conduction is not hard, but a higher mastery of statistic mechanics is necessary, and I selected a course next term. 
3. One of my goal is to achieve the device-level demonstration of the cooling for nanoscale hot spot with the integration of both the carbon nano materials and nanoscale fluid transport. There are emerging novel phenomena on nanoscale thermal properties.  But  I do not have a clear roadmap yet. 

• With the discussion of my mentor, my senior project is determined as Silicon-CNT hybrid anodes for Lithium-ion Batteries. It mainly originates from our group's transition to nano scale transport and energy conversion. I expect research training on nano fabrication as well as ion diffusion and system analysis.