Enhanced microwave absorption of screen-printed multiwalled carbon nanotube/Ca_1−xBa_xBi₂Nb₂O₉ (0≤x≤1) multilayered thick film composites

Phadtare, Varsha D.,Parale, Vinayak G.,Kulkarni, Gopal K.,Park, Hyung-Ho,Puri, Vijaya R. Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.765 No.-

<P><B>Abstract</B></P> <P>Multiwalled carbon nanotube (MWCNT)/Ca<SUB>1−x</SUB>Ba<SUB>x</SUB>Bi<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>9</SUB> (0 ≤ x ≤ 1)-layered thick film microwave-absorbing composites were prepared through the screen-printing method. The multilayered thick film composites were designed to improve their microwave absorption capabilities and the thickness of prepared thick films is around 115 μm. The layered thick film composites were synthesized with functionalized MWCNTs and co-precipitated Ca<SUB>1−x</SUB>Ba<SUB>x</SUB>Bi<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>9</SUB> (0 ≤ x ≤ 1) (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) Aurivillius-type ceramics. The microwave absorption, transmission and reflection properties were investigated in the J, X, and Ku-bands with a frequency range of 6–18 GHz. The multilayered thick film composites showed enhanced microwave absorption properties in the broadband frequency region. The multilayered composite with x = 0.8 had 1.5 times better microwave absorption than the only MWCNT thick film. This work presents a new approach to the fabrication of multilayered composites with enhanced microwave absorbance via simple screen-printing method.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MWCNT/Ca<SUB>1−x</SUB>Ba<SUB>x</SUB>Bi<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>9</SUB> (0 ≤ x ≤ 1) layered thick film composites have been prepared via screen-printing method. </LI> <LI> Enhanced microwave absorption up to 88% was obtained due to the multilayered structure with thickness 115 μm. </LI> <LI> MWCNT/Ca<SUB>1−x</SUB>Ba<SUB>x</SUB>Bi<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>9</SUB> (0 ≤ x ≤ 1) layered thick film composite shows broadband (6–18 GHz) microwave absorption characteristic. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Flexible and lightweight Fe₃O₄/polymer foam composites for microwave-absorption applications

Phadtare, Varsha D.,Parale, Vinayak G.,Lee, Kyu-Yeon,Kim, Taehee,Puri, Vijaya R.,Park, Hyung-Ho Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.805 No.-

<P><B>Abstract</B></P> <P>Lightweight and highly porous magnetic polymer foam (MPF) composites were synthesized using a simple, efficient, and environmentally friendly strategy. Their scaffold structure was well controlled using a surfactant and by varying the amount of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles (NPs) added to the emulsion solution used in their preparation. The three-dimensional (3D) sponge-like MPFs are microwave-absorbing materials, and their structural and microstructural characteristics were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The magnetic properties of the MPF composites were also characterized. The polymer matrix of the composites exhibited excellent thermal stability. The microwave-absorbing properties of the MPF composites with increasing amounts of Fe<SUB>3</SUB>O<SUB>4</SUB> NPs (5 wt%, 10 wt%, and 15 wt%) were systematically studied. The microwave absorption of the polymer foam was enhanced to as high as 82% with the addition of Fe<SUB>3</SUB>O<SUB>4</SUB> NPs. Our results demonstrate that the prepared MPF composites have the potential to be used as lightweight, microwave-absorbing materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Magnetic polymer foam was fabricated by high internal phase emulsion method. </LI> <LI> Fe<SUB>3</SUB>O<SUB>4</SUB> NPs provide magnetic properties without disturbing porous structure. </LI> <LI> The foam exhibited magnetic properties and compressibility. </LI> <LI> Microwave absorption was enhanced with macroporous polymer foam/Fe<SUB>3</SUB>O<SUB>4</SUB> composite. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Microwave dielectric properties of barium substituted screen printed CaBi₂Nb₂O₉ ceramic thick films

Phadtare, Varsha D.,Parale, Vinayak G.,Kulkarni, Gopal K.,Park, Hyung-Ho,Puri, Vijaya R. Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.7

<P><B>Abstract</B></P> <P>In the present study, Aurivillius-structured Ba<SUP>2+</SUP> substituted CaBi<SUB>2</SUB>Nb<SUB>2</SUB>O<SUB>9</SUB> (CBNO) ceramic powder was synthesized by co-precipitation method. The CBNO thick films were delineated by screen printing method on alumina substrates using co-precipitated ceramic powder. The overlay method was adopted to measure the microwave dielectric properties of prepared thick films. Single phase layered perovskite structure of the prepared thick films was confirmed by X-ray Diffraction. The effects of Ba<SUP>2+</SUP> substitution on the surface morphology, bonding, and microwave dielectric properties of thick films were systematically presented. The maximum value of microwave dielectric constant for the CBNO thick films at 11.8GHz is 15.6 for Ba<SUP>2+</SUP>=0.8 substitution. The shift in the stretching vibration modes of the Nb-O bond of NbO<SUB>6</SUB> octahedron in the Raman spectra with a substitution of Ba<SUP>2+</SUP> in CBNO was observed. The substitution of Ba<SUP>2+</SUP> on A-site of CBNO improves the microwave dielectric properties of prepared thick films. This work may provide a new approach to enhance the microwave dielectric performance of Aurivillius-structured ceramic thick films.</P>

Chemically Bonded Thermally Expandable Microsphere-silica Composite Aerogel with Thermal Insulation Property for Industrial Use

이규연,Varsha D. Phadtare,최하령,문승환,김종일,배영광,박형호 한국마이크로전자및패키징학회 2019 마이크로전자 및 패키징학회지 Vol.26 No.2

Thermally expandable microsphere and aerogel composite was prepared by chemical compositization. Microsphere can produce synergies with aerogel, especially an enhancement of mechanical property. Through condensation between sulfonated microsphere and hydrolyzed silica sol, chemically-connected composite aerogel could be prepared. The presence of hydroxyl group on the sulfonated microsphere was observed, which was the prime functional group of reaction with hydrolyzed silica sol. Silica aerogel-coated microsphere was confirmed through microstructure analysis. The presence of silicon-carbon absorption band and peaks from composite aerogel was observed, which proved the chemical bonding between them. A relatively low thermal conductivity value of 0.063 W/m·K was obtained.

Structural, morphological, and magnetic properties of Zn_xCo_1-xFe₂O₄ (0 ≤ x ≤ 1) prepared using a chemical co-precipitation method

Powar, Rohit R.,Phadtare, Varsha D.,Parale, Vinayak G.,Park, Hyung-Ho,Pathak, Sachin,Kamble, Pravin R.,Piste, Pravina B.,Zambare, Dnyanashwar N. Elsevier 2018 Ceramics international Vol.44 No.17

<P><B>Abstract</B></P> <P>In the present study, the chemical co-precipitation technique was adopted to synthesize Zn<SUB>x</SUB>Co<SUB>1-x</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> (ZCF) (0 ≤ x ≤ 1) ferrites. The thermogravimetric-differential thermal analysis results revealed that above 405 °C, the precursor had decomposed and ferrite formation had occurred. The structure and morphology of the prepared ferrite nanoparticles were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy (FE-SEM). The synthesized polycrystalline nanoparticles had a cubic spinel structure and the crystallite size was in the range of 6.09–12.98 nm. The prepared ferrites appeared as nearly spherical nanoparticles with a particle size in between 0.13 and 0.23 µm, as confirmed using FE-SEM. The elemental composition was determined using the energy-dispersive X-ray spectroscopy technique. The influence of the Zn-substituted cobalt ferrites (ZCF) on the structural, morphological, and magnetic properties were studied. The magnetic properties of the ZCF samples such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 0.387–2.065 emu/g, 0.057–1.282 emu/g, and 60–1834 Oe, respectively. It was confirmed from the nature of the hysteresis loops that the given ZCF samples can be considered as a soft magnetic material.</P>

Structural and Magnetic Properties of Cr-Zn Nanoferrites Synthesized by Chemical Co-Precipitation Method

Powar, Rohit R.,Phadtare, Varsha D.,Parale, Vinayak G.,Pathak, Sachin,Piste, Pravina B.,Zambare, Dnyandevo N. The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.5

Chromium-doped zinc ferrite nanoparticles with the general formula Cr_yZnFe_2-yO₄ (y = 0, 0.025, 0.05, 0.075, and 0.1) were synthesized by a surfactant-assisted chemical co-precipitation route using metal nitrate salt precursors. The phase purity and structural parameters were determined by powder X-ray diffraction. The concentration of Cr³⁺ doped into ZnFe₂O₄ (ZF) noticeably affected the crystallite size, which was in the range of 22 nm to 36 nm, and all samples showed a single cubic spinel structure without any secondary phase or impurities. The lattice parameter, X-ray density, and skeletal density increased with an increase in the Cr-doping concentration; on the other hand, a decreasing trend was observed for the particle size and porosity. The influence of Cr³⁺ substitution on ZF magnetic properties were studied under an applied field of 15 kOe. The overall results revealed that the incorporation of a small amount of Cr dopant changed the structural, electrical, and magnetic properties of ZF.

Structural and Magnetic Properties of Cr-Zn Nanoferrites Synthesized by Chemical Co-Precipitation Method

Rohit R. Powar,Varsha D. Phadtare,Vinayak G. Parale,Sachin Pathak,Pravina B. Piste,Dnyandevo N. Zambare 한국세라믹학회 2019 한국세라믹학회지 Vol.56 No.5

Chromium-doped zinc ferrite nanoparticles with the general formula CryZnFe2-yO4 (y = 0, 0.025, 0.05, 0.075, and 0.1) were synthesized by a surfactant-assisted chemical co-precipitation route using metal nitrate salt precursors. The phase purity and structural parameters were determined by powder X-ray diffraction. The concentration of Cr3+ doped into ZnFe2O4 (ZF) noticeably affected the crystallite size, which was in the range of 22 nm to 36 nm, and all samples showed a single cubic spinel structure without any secondary phase or impurities. The lattice parameter, X-ray density, and skeletal density increased with an increase in the Cr-doping concentration; on the other hand, a decreasing trend was observed for the particle size and porosity. The influence of Cr3+ substitution on ZF magnetic properties were studied under an applied field of 15 kOe. The overall results revealed that the incorporation of a small amount of Cr dopant changed the structural, electrical, and magnetic properties of ZF.

Facile synthesis of hydrophobic, thermally stable, and insulative organically modified silica aerogels using co-precursor method

Parale, Vinayak G.,Lee, Kyu-Yeon,Jung, Hae-Noo-Ree,Nah, Ha-Yoon,Choi, Haryeong,Kim, Tae-Hee,Phadtare, Varsha D.,Park, Hyung-Ho Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.4

<P><B>Abstract</B></P> <P>Silica aerogels have low density and high specific surface area, but there are restrictions regarding their durability and commercialization owing to their fragile nature and the strong moisture absorbing behavior of the siloxane network. To overcome these restrictions, this study evaluated hybrid organically modified silica (ORMOSIL) aerogels by employing 3-(trimethoxysilylpropyl) methacrylate (TMSPM) in tetraethyl orthosilicate (TEOS) through a two-step sol-gel co-precursor method. The methacrylate organic groups were incorporated into the silica networks via reactions between the Si-OH moieties in silica aerogels, resulting in ORMOSIL aerogels. The properties of the ORMOSIL aerogels were strongly affected by the amount of TMSPM co-precursor. The highest concentration of TMSPM (30wt%) resulted in ORMOSIL aerogels with improved characteristics when compared with the pristine TEOS-based silica aerogels, such as hardness (0.15GPa), Young's modulus (1.26GPa), low thermal conductivity (0.038W/mK), high water contact angle (140°), and high thermal stability (350°C).</P>