Dr. Babu Madavali

Dr. Babu Madavali

Kongju National University

H-index: 13

Asia-South Korea

About Dr. Babu Madavali

Dr. Babu Madavali, With an exceptional h-index of 13 and a recent h-index of 11 (since 2020), a distinguished researcher at Kongju National University, specializes in the field of Thermoelectric materials, Spin Caloritronics, Magnetic Materials, Energy harvesting.

His recent articles reflect a diverse array of research interests and contributions to the field:

Realizing high thermoelectric properties through the development of bimodal microstructures using water atomized p-type Bi0. 5Sb1. 5Te3 alloys

Effect of Si alloying on the structural, thermal expansion, and magnetic properties of FeCoNiAlSix high-entropy alloys

Advancement of thermoelectric performances through the dispersion of expanded graphene on p-type BiSbTe alloys

Complex microstructure induced high thermoelectric performances of p-type Bi–Sb–Te alloys

Enhancement of magnetic properties in spark plasma sintered Nd-Fe-B magnets via controlled microstructure of melt-spun ribbons

Investigation of anisotropy in microstructure and thermoelectric properties of large-scaled p-type Bi–Sb–Te sintered body made by hot pressing

Enhancing the thermoelectric properties through hierarchical structured materials fabricated through successive arrangement of different microstructure

Enhancing the thermoelectric properties of powder metallurgically produced BiSbTe alloy through feasible electroless surface coating method

Dr. Babu Madavali Information

University

Kongju National University

Position

___

Citations(all)

560

Citations(since 2020)

442

Cited By

268

hIndex(all)

13

hIndex(since 2020)

11

i10Index(all)

16

i10Index(since 2020)

11

Email

University Profile Page

Kongju National University

Dr. Babu Madavali Skills & Research Interests

Thermoelectric materials

Spin Caloritronics

Magnetic Materials

Energy harvesting

Top articles of Dr. Babu Madavali

Realizing high thermoelectric properties through the development of bimodal microstructures using water atomized p-type Bi0. 5Sb1. 5Te3 alloys

Authors

Jin-Gu Kwon,Babu Madavali,Ye-Eun Lee,Sung-Jae Jo,Min-woo Shin,Jun-Woo Song,Ji-Woon Lee,Soon-Jik Hong

Journal

Materials Research Bulletin

Published Date

2024/4/5

In this work, we fabricated bimodal structured high performance p-type BiSbTe alloys by combining coarse and sub-micron scale water atomized powders, followed by spark plasma sintering. The bulk fracture analysis revealed a dense and inhomogeneous distribution of mixed grains on the surface, while the texture analysis using EBSD revealed that the bulk specimens had a bimodal microstructure with random grain alignment due to the distribution of initial powder sizes. The coarse grain specimen exhibited high electrical conductivity of 1257 Ω− 1 cm− 1 because of its high carrier mobility and carrier concentration. A high Seebeck coefficient (214 μV/K) and low thermal conductivity (0.95 W/mK) were observed for the bimodal structured specimens because scattering of carriers and phonons was higher compared with the coarse specimen. The maximum thermoelectric figure of merit, ZT of 1.2, and Z T Avg of 1.14 …

Effect of Si alloying on the structural, thermal expansion, and magnetic properties of FeCoNiAlSix high-entropy alloys

Authors

Cheenepalli Nagarjuna,Sheetal Kumar Dewangan,Hansung Lee,Babu Madavali,Byungmin Ahn

Journal

Journal of Materials Science

Published Date

2024/3

In this study, a series of FeCoNiAlSix (x= 0, 0.2, 0.4, and 0.6) high-entropy alloys (HEAs) were prepared by mechanical alloying and spark plasma sintering. The effects of Si alloying on the structural, thermal expansion, and magnetic properties of HEAs were investigated. The X-ray diffraction and microscopic results reveal that the crystal structure changes from FCC+ BCC to single BCC phase with increasing Si content. By increasing Si content, the coefficient of thermal expansion decreases, especially at high temperatures, indicating that Si has a greater effect on improving the dimensional stability. In addition, the developed HEAs exhibit good saturation magnetization~ 86.23 emu/g, low coercivity~ 18.4 Oe, and high electrical resistivity~ 84 µΩ. cm, indicating the present HEA can be used in soft magnetic applications. Furthermore, the hardness of HEAs increased from 510±10 to 730±10 HV with an increasing Si …

Advancement of thermoelectric performances through the dispersion of expanded graphene on p-type BiSbTe alloys

Authors

Eun-Ha Go,Rathinam Vasudevan,Babu Madavali,Peyala Dharmaiah,Min-Woo Shin,Sung Ho Song,Soon-Jik Hong

Journal

Powder Metallurgy

Published Date

2023/12

We demonstrated the systematic investigation of the graphene addition on the microstructural behaviour and concurrent thermoelectric properties of water-atomized p-type BiSbTe (BST)- based alloy using mechanical ball milling, and followed through the spark plasma sintering to fabricate a bulk compact specimen. X-ray diffraction results confirm the single phase of BST. The fracture surface of both specimen exhibits the homogenous distribution of grains with irregular shapes in a random alignment. The graphene in the BST provides an extra carrier transport leading to an increment in the carrier concentration (n) resulting in higher electrical conductivity (σ) for the BST + Graphene composite. The interface between two-dimensional (2D) graphene and bulk BST provides a larger degree of phonon scattering leading to a maximum reduced thermal conductivity (к) of 0.8 W m−1K−1 compared to pristine- BST (0.9 …

Complex microstructure induced high thermoelectric performances of p-type Bi–Sb–Te alloys

Authors

Eun-Ha Go,Babu Madavali,Min-Woo Shin,Sung Ho Song,Soon-Jik Hong

Journal

Materials Chemistry and Physics

Published Date

2023/10/1

In this research, we have fabricated the complex microstructure features along with the high density of twin boundaries using the combination of magnetic pulse compaction (MPC) and spark plasma sintering (SPS), which are exclusively improved the thermoelectric transport properties of p-type Bi0.5Sb1.5Te3 alloys via effective scattering of carriers and phonons at the grain boundary interfaces. The texture analysis confirmed the formation of bimodal (mixed grains) microstructural features in MPC + SPS specimens sintered at 350 °C, and 400 °C respectively due to the adhesion of fine grains (grain growth) and initiation of recrystallization at high temperatures. In addition to high density of twin structure, high-angle grain boundaries have also been identified. The power factor of 3.53 mW/m.K2 was obtained for the MPC + SPS at 400 °C due to increased Seebeck coefficient and larger electrical conductivity values …

Enhancement of magnetic properties in spark plasma sintered Nd-Fe-B magnets via controlled microstructure of melt-spun ribbons

Authors

Taek-soo Kim,Babu Madavali,Sung Jae Jo,Jin Gyu Lee,Gian Song,Soon-jik Hong

Journal

Journal of Magnetism and Magnetic Materials

Published Date

2023/9/15

In this work, we investigated the formation of columnar grain microstructure of melt - spun Nd28.5Fe66.5Dy4B1 (wt.%) (Nd-Fe-B) alloy and concurrently, studied their effect on the magnetic properties of the spark plasma sintered (SPS) Nd-Fe-B bulk. The melt spinning was performed at different wheel speeds in the range of 15 to 30 m/s. The formation of columnar grains perpendicular to the plane of the ribbons were examined through SEM and the XRD result reveals the strong (00 l) crystal texture. The mechanism behind the formation of columnar grains in melt-spun ribbon and the magnetic properties of the sintered Nd-Fe-B bulks were deeply discussed. The obtained Nd-Fe-B magnet realizes enhanced magnetic properties through the controlled microstructure of melt-spun ribbons including columnar grain regions along with equiaxed grain regions. Eventually, it shows an improved coercivity of 17.3 kOe and …

Investigation of anisotropy in microstructure and thermoelectric properties of large-scaled p-type Bi–Sb–Te sintered body made by hot pressing

Authors

Babu Madavali,Van Dao Nguyen,Sung Jae Jo,Chul-hee Lee,Soon-Jik Hong

Journal

Journal of Materials Science

Published Date

2022/10

In this work, a large-sized pellet of about 200 g (Ф40 × 23 mm) of p-type polycrystalline based Bi–Sb–Te was prepared using gas atomization and hot pressing processes. A systematic investigation was conducted on the microstructural behavior along parallel and perpendicular planes, and the anisotropic behavior of the thermoelectric and mechanical properties was subsequently studied. The X-ray diffraction studies revealed a slight orientation in grains along the perpendicular direction. The electron back scattered diffraction (EBSD) analysis revealed that the grains in both samples were uniformly disseminated throughout the matrix in random directions with an average grain sizes of 4.30, and 4.83 μm, respectively, for the parallel and perpendicular directions. The electrical conductivity and thermal conductivity had higher values along the perpendicular direction compared with the parallel direction, which was …

Enhancing the thermoelectric properties through hierarchical structured materials fabricated through successive arrangement of different microstructure

Authors

Pathan Sharief,Peyala Dharmaiah,Babu Madavali,Jun Woo Song,Jin Kyu Lee,Jong Hyeon Lee,Soon-Jik Hong

Journal

Journal of Alloys and Compounds

Published Date

2022/7/25

The importance of ZT in thermoelectric (TE) materials is critical for green power generation and cooling applications. Therefore, tremendous efforts were underway to improve ZT, in which we proposed a layer structured approach by successively arranging of coarse Bi0.5Sb1.5Te3 (BST) and fine BST/0.07Cu microstructure materials and investigated their transportation mechanism. The dual bulk microstructure was well-bonded and confirmed by analyzing the microstructure through scanning electron microscope (SEM), electron backscatter diffraction analysis (EBSD) and simulated the electrical potential and temperature distribution during spark plasma sintering with COMSOL software. The results indicate that the highest power factor of 3.8 mW/m-K2 was attained in the layer structured sample, which is significantly higher than other samples due to its synergistically optimized electrical conductivity and Seebeck …

Enhancing the thermoelectric properties of powder metallurgically produced BiSbTe alloy through feasible electroless surface coating method

Authors

Pathan Sharief,Babu Madavali,Peyala Dharmaiah,Jun Woo Song,Youhan Sohn,Jun Hyun Han,Sung Ho Song,Soon-Jik Hong

Journal

Journal of the European Ceramic Society

Published Date

2022/7/1

The powder metallurgical techniques capable of powder mass production but lacks in achieving high zT. Therefore, to improve zT, electroless surface coating was performed on water atomized Bi0.5Sb1.5Te3 (BST) powder and stimulated their conducting nature. Surface chemical composition studies displays fine elemental coating on the BST powders and remarkably, the Seebeck coefficient increased till 450 K. The surface coated bulk sample shows greatly improved power factor about ~45% higher than uncoated sample. Indeed, at high temperature we obtained reduced lattice thermal conductivity which confirms the remarkable suppression of bipolar thermal conductivity. Consequently, a maximum zT of 1.16 at 400 K achieved by coated samples which is ~102% enhancement compared to original BST. Also, we attained high average zT of ~0.99 which helps in employing thermoelectric devices across wide …

Fabrication of ultrafine powder using processing control agent, and investigation of its effect on microstructure and thermoelectric properties of p-type (Bi, Sb) 2Te3 alloys

Authors

Babu Madavali,Pathan Sharief,Jun-woo Song,Ki Buem Kim,C Suryanarayana,Sung Ho Song,Soon-Jik Hong

Journal

Advanced Powder Technology

Published Date

2022/2/1

Low-dimensional materials can significantly enhance the efficiency of thermoelectric devices for power generation and cooling applications. In the present work, ultra-fine powders of p-type (Bi, Sb)2Te3 alloys are fabricated through high energy ball milling using stearic acid as a process control agent (PCA). The influence of the PCA addition on powder characteristics, microstructure and thermoelectric transport properties are studied. Further, the ultra-fine powder is subjected to calcination (Cal-PCA) and subsequently consolidated all powders using spark plasma sintering (SPS). The PCA, Cal-PCA, and non-PCA powder morphological effects on the microstructure and thermoelectric properties are systematically investigated and elucidated thoroughly. The electron beam scattering diffraction (EBSD) results confirmed that the PCA sample exhibited very fine grains (average grain size of ∼800 nm) compared to the …

Investigation of homogeneity in microstructure and thermoelectric properties at various positions in high-thickness sintered bulks of p-type 20% Bi2Te3–80% Sb2Te3 alloys

Authors

Babu Madavali,Chul-Hee Lee,Jin-Gu Han,Dong Hwan Kim,Jong Tae Kim,Gian Song,Jin Kyu Lee,Soon-Jik Hong

Journal

Journal of Materials Science: Materials in Electronics

Published Date

2021/6

Thermoelectric devices are environmentally friendly renewable energy sources that use waste heat to generate electricity. So far, p-type Bi–Sb–Te-based alloys with high thermoelectric properties were fabricated using low-dimensional and single growth methods as small-scale, laboratory-grown samples. However, large-scale fabrication processes are required for commercial applications of thermoelectric devices. In this work, large amounts (2–3 kg) of p-type 20%Bi2Te3–80%Sb2Te3 alloy powders were fabricated using the gas atomization (GA) process under an inert gas atmosphere. Subsequently, a large-scale sample, 64 mm thick and 25 mm in diameter, was consolidated from the as-fabricated GA powders using spark plasma sintering at 673 K. The homogeneity of the microstructure, density, thermoelectric properties, and mechanical properties of the high-thickness sintered bulk were systematically …

Worn surface and subsurface layer structure formation behavior on wear mechanism of CoCrFeMnNi high entropy alloy in different sliding conditions

Authors

Cheenepalli Nagarjuna,Hyeon-Jeong You,Suseong Ahn,Jun-Woo Song,Kwang-Yong Jeong,Babu Madavali,Gian Song,Young-Sang Na,Jong Woo Won,Hyoung-Seop Kim,Soon-Jik Hong

Journal

Applied Surface Science

Published Date

2021/5/30

In this study, equiatomic CoCrFeMnNi high entropy alloy (HEA) was fabricated by induction melting and subsequent thermomechanical treatments were carried out to achieve single FCC phase with equiaxed grains. The friction and wear behavior of HEA was investigated using ball-on-disc configuration in dry and ambient conditions under different sliding time, normal load and velocity. The detailed microscopic characterizations were invested to examine the worn surface and subsurface deformation mechanisms to identify the kinds of wear involved during dry sliding process. Results revealed the hardness of deformed layer showed 63% higher than matrix owing to grain refinement induced by sliding friction. The friction coefficient stabilized at longer sliding time due to oxidized wear debris acting as as lubricant behavior during sliding. While wear rate significantly decreased with increasing sliding time due to …

Reduction of thermal conductivity through complex microstructure by dispersion of carbon nanofiber in p-Type Bi0. 5Sb1. 5Te3 alloys

Authors

P Sharief,B Madavali,Y Sohn,JH Han,G Song,SJ Hong

Journal

Archives of Metallurgy and Materials

Published Date

2021

The influence of nano dispersion on the thermoelectric properties of Bi2Te3 was actively investigating to wide-spread thermoelectric applications. Herein this report, we have systematically controlled the microstructure of Bi0.5Sb1.5Te3 (BST) alloys through the incorporation of carbon nanofiber (CNF), and studied their effect on thermoelectric properties, and mechanical properties. The BST/x-CNF (x-0, 0.05, 0.1, 0.2 wt.%) composites powder was fabricated using high energy ball milling, and subsequently consolidated the powder using spark plasma sintering. The identification of CNF in bulk composites was analyzed in Raman spectroscopy and corresponding CNF peaks were recognized. The BST matrix grain size was greatly reduced with CNF dispersion and consistently decreased along CNF percentage. The electrical conductivity was reduced and Seebeck coefficient varied in small-scale by embedding CNF. The thermal conductivity was progressively diminished, obtained lattice thermal conductivity was lowest compared to bare sample due to induced phonon scattering at interfaces of secondary phases as well as highly dense fine grain boundaries. The peak ZT of 0.95 achieved for 0.1 wt.% dispersed BST/CNF composites. The Vickers hardness value of 101.8 Hv was obtained for the BST/CNF composites.

Development of high-performance thermoelectric materials by microstructure control of p-type BiSbTe based alloys fabricated by water atomization

Authors

Babu Madavali,Pathan Sharief,Kyoung-Tae Park,Gian Song,Song-Yi Back,Jong-Soo Rhyee,Soon-Jik Hong

Journal

Materials

Published Date

2021/8/27

Developing inexpensive and rapid fabrication methods for high efficiency thermoelectric alloys is a crucial challenge for the thermoelectric industry, especially for energy conversion applications. Here, we fabricated large amounts of p-type Cu0.07Bi0.5Sb1.5Te3 alloys, using water atomization to control its microstructure and improve thermoelectric performance by optimizing its initial powder size. All the water atomized powders were sieved with different aperture sizes, of 32–75 μm, 75–125 μm, 125–200 μm, and <200 μm, and subsequently consolidated using hot pressing at 490 °C. The grain sizes were found to increase with increasing powder particle size, which also increased carrier mobility due to improved carrier transport. The maximum electrical conductivity of 1457.33 Ω−1 cm−1 was obtained for the 125–200 μm samples due to their large grain sizes and subsequent high mobility. The Seebeck coefficient slightly increased with decreasing particle size due to scattering of carriers at fine grain boundaries. The higher power factor values of 4.20, 4.22 × 10−3 W/mk2 were, respectively, obtained for large powder specimens, such as 125–200 μm and 75–125 μm, due to their higher electrical conductivity. In addition, thermal conductivity increased with increasing particle size due to the improvement in carriers and phonons transport. The 75–125 μm powder specimen exhibited a relatively high thermoelectric figure of merit, ZT of 1.257 due to this higher electric conductivity.

Investigation of graphene dispersion on thermoelectric, magnetic, and mechanical properties of p-type Bi0. 5Sb1. 5Te3 alloys

Authors

Pathan Sharief,Babu Madavali,Sung Ho Song,Jin Kyu Lee,Ki Buem Kim,Jong Tae Kim,Dong Hwan Kim,Jun-Hyun Han,Soon-Jik Hong

Journal

Materials Chemistry and Physics

Published Date

2021/7/1

In this research, polycrystalline p-type Bi0.5Sb1.5Te3 (BST)/x-wt% graphene (x = 0, 0.05, 0.1 and 0.2 wt%) composite bulks were fabricated to systematically investigate the effect of graphene content on thermoelectric, as well as magnetic and mechanical properties. The peaks corresponding to the D, G and 2D bands of graphene were clearly identified with Raman spectroscopy, and revealed that graphene was well dispersed in the BST matrix. The bulk fracture surfaces displayed randomly distributed grains and a progressive decrease in grain size, with increasing graphene content in the composite samples. A dramatic reduction in thermal conductivity of about 10%, and 12% was achieved for the 0.1, and 0.2 wt% graphene dispersed Bi0.5Sb1.5Te3 samples, respectively, due to the strong scattering of phonons at interfaces and fine grain boundaries. Thanks to the adequate power factor and the reduction in …

Fabrication of large-scale p-type 75% Sb2Te3-25% Bi2Te3 thermoelectric materials by gas atomization and hot isostatic pressing

Authors

Sang Min Yoon,Babu Madavali,Chul-Hee Lee,Olu Emmanuel Femi,Jong-Hyeon Lee,Sung Ho Song,Soon-Jik Hong

Journal

Materials Research Bulletin

Published Date

2020/10/1

For economic viability of thermoelectric modules, issues of scalability and sturdiness to drive down production and manufacturing cost must be adequately addressed. In this study, we report a large-scale production of 3 Kg/batch of 75%Sb2Te3-25%Bi2Te3 powder by gas atomization. The as-produced large-scale atomized powder was subsequently sintered by hot isostatic pressing (HIP) at two different temperatures. The microstructure of the HIPed fracture surface reveals a transgranular mode of fracture in the basal plane of the grains perpendicular to the contact surface. The texture analysis showed that grains were randomly distributed and indicating no preferred alignment in any direction. The sample HIPed at 450 °C shows the highest electrical conductivity of 1350 Ω−1 cm−1 at room temperature due to their high carrier mobility. The highest ZT of 1.15 at 375 K was observed for the sample HIPed at 450 °C …

Investigation of the magnetic properties and fracture behavior of Nd–Fe–B alloy powders during high-energy ball milling

Authors

Dong-won Shin,Babu Madavali,Dong-soo Kim,Jin-Young Lee,Min-chul Kang,Cheol-woong Yang,C Suryanarayana,Soon-jik Hong

Journal

Materials Research Express

Published Date

2020/9/9

In this work, Nd–Fe–B alloy powders are fabricated via high energy ball milling and their fracture behavior and magnetic properties are investigated at different milling times. The powder characteristics (particle shape, size, size distribution, and microstructure) and magnetic properties of the Nd–Fe–B alloys are systematically analyzed. The initial spherical Nd–Fe–B powder is cracked/crushed even after a short period of milling (30 s) due to the high impact energy generated during high energy ball milling. These randomly cracked polygonal-shaped powders are fragmented after 5 min of milling and converted to fine powders. Interestingly, the fine particles after milling for 5 min are conducive to agglomeration at longer milling times (20–60 min) and formed spherically-shaped agglomerated powder. Additionally, the sphericity of the powder increased to 92% by re-pulverization and agglomeration at 60 min. The milled …

Preparation and thermoelectric performance of nano rare-earth oxides dispersed p-type BiSbTe alloys by mechanical milling and spark plasma sintering

Authors

Babu Madavali,Dong-won Shin,Sung Ho Song,Dong-soo Kim,Jin Kyu Lee,Soon-Jik Hong

Journal

Materials Chemistry and Physics

Published Date

2020/10/1

Simultaneously, the enhancement of power factor and reduction in thermal conductivity is a critical issue to improve the thermoelectric performance of a certain material. In the present work, the rare earth oxide, Pr6O11 was added to the Bi-Sb-Te material and the corresponding thermoelectric properties have been systematically investigated. The Seebeck coefficient was slightly improved due to the increase in effective mass by addition of rare earth oxides in BiSbTe matrix. The electrical conductivity was decreased with increasing rare earth oxide content due to the decreasing mobility owing to the carrier scattering at grain boundaries. The thermal conductivity was reduced of 8% for Pr6O11/BiSbTe composites in which the 4 wt% added Pr6O11 particles, act as a scattering center for middle to higher wavelength phonons and induce the phonon scattering. As a result, the maximum thermoelectric figure of merit, ZT of …

See List of Professors in Dr. Babu Madavali University(Kongju National University)

Dr. Babu Madavali FAQs

What is Dr. Babu Madavali's h-index at Kongju National University?

The h-index of Dr. Babu Madavali has been 11 since 2020 and 13 in total.

What are Dr. Babu Madavali's top articles?

The articles with the titles of

Realizing high thermoelectric properties through the development of bimodal microstructures using water atomized p-type Bi0. 5Sb1. 5Te3 alloys

Effect of Si alloying on the structural, thermal expansion, and magnetic properties of FeCoNiAlSix high-entropy alloys

Advancement of thermoelectric performances through the dispersion of expanded graphene on p-type BiSbTe alloys

Complex microstructure induced high thermoelectric performances of p-type Bi–Sb–Te alloys

Enhancement of magnetic properties in spark plasma sintered Nd-Fe-B magnets via controlled microstructure of melt-spun ribbons

Investigation of anisotropy in microstructure and thermoelectric properties of large-scaled p-type Bi–Sb–Te sintered body made by hot pressing

Enhancing the thermoelectric properties through hierarchical structured materials fabricated through successive arrangement of different microstructure

Enhancing the thermoelectric properties of powder metallurgically produced BiSbTe alloy through feasible electroless surface coating method

...

are the top articles of Dr. Babu Madavali at Kongju National University.

What are Dr. Babu Madavali's research interests?

The research interests of Dr. Babu Madavali are: Thermoelectric materials, Spin Caloritronics, Magnetic Materials, Energy harvesting

What is Dr. Babu Madavali's total number of citations?

Dr. Babu Madavali has 560 citations in total.

What are the co-authors of Dr. Babu Madavali?

The co-authors of Dr. Babu Madavali are C Suryanarayana, 홍순직, Dr. Peyala Dharmaiah.

    Co-Authors

    H-index: 61
    C Suryanarayana

    C Suryanarayana

    University of Central Florida

    H-index: 36
    홍순직

    홍순직

    Kongju National University

    H-index: 13
    Dr. Peyala Dharmaiah

    Dr. Peyala Dharmaiah

    Kongju National University

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