Girish Joshi - Academia.edu (original) (raw)
Papers by Girish Joshi
Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-... more Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals
Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 ... more Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 into the polymer matrix using solution blending. The modified blends were characterized by X-ray diffraction, Thermogravimetric analysis, and Scanning electron microscopy. The crystalline to amorphous phase variation was confirmed by XRD with increase in the interplanar distance (d). TGA results indicate that the thermal stability of the modified blend was significantly improved as a function of alumina loading which may be due to interfacial interaction between the alumina particles and the polymers. Scanning electron microscopy studies reveal the presence of alumina particles resulting in plane surface morphology. The modified blends show very high dielectric constant value (10 5 –10 7) as a function of frequency (in the range 50 Hz–35 MHz) and temperature in the range (40–150 °C). The modified polymer blend demonstrate consistent polarization across the frequency band 50 Hz–10 kHz. The neutral aggregates formation due to higher concentration of alumina loading demonstrated an influence on AC conductivity. This investigation can be feasible for electronic and electrical engineering application as the dielectric medium.
Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 ... more Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 into the polymer matrix using solution blending. The modified blends were characterized by X-ray diffraction, Thermogravimetric analysis, and Scanning electron microscopy. The crystalline to amorphous phase variation was confirmed by XRD with increase in the interplanar distance (d). TGA results indicate that the thermal stability of the modified blend was significantly improved as a function of alumina loading which may be due to interfacial interaction between the alumina particles and the polymers. Scanning electron microscopy studies reveal the presence of alumina particles resulting in plane surface morphology. The modified blends show very high dielectric constant value (10 5 –10 7) as a function of frequency (in the range 50 Hz–35 MHz) and temperature in the range (40–150 °C). The modified polymer blend demonstrate consistent polarization across the frequency band 50 Hz–10 kHz. The neutral aggregates formation due to higher concentration of alumina loading demonstrated an influence on AC conductivity. This investigation can be feasible for electronic and electrical engineering application as the dielectric medium.
We demonstrated the modification of Isophthalic polyester (IP) resin/styrene in situ blends by di... more We demonstrated the modification of Isophthalic polyester (IP) resin/styrene in situ blends by dispersion of nano perovskite strontium titanate nanoparticles (STONP). The thermal stability of prepared sample was examined by differential scanning calorimetry. The variation of glass transition temperature of IP resin on styrene and filler content reflects the elastic network of the polymer chain, miscibility of polystyrene and IP resin and phase separation between filler and polymer matrix. The phase separation and morphology of the blend was confirmed by scanning electron microscope and energy dispersive X-ray spectroscopy as a function of STONP loading. The dielectric property of IP resin/styrene/STONP was analyzed as a function of frequency (50 Hz-10 MHz) and temperature (40-150°C). Two relaxation process was clearly identified namely Maxwell-Wagner-Siller effect corresponds to low frequency polarization and a-relaxation corresponds to glass transition effect followed by Vogel-Fulcher-Tamman equation (VTF equation). We disclosed the improvement of dielectric properties as a function of STONP loading. This investigation is highly useful in the electronics domain.
Composite Interfaces, 2014
Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mech... more Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mechanical and thermal properties of polyvinyl alcohol (PVA) nanocomposites, Composite Interfaces, 21:6, 487-506, Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an 'anion-π' type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-mgraphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/ SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.
In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical t... more In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical treatment of natural graphite flakes. In this process, the graphite expands almost 300 – 350 times of its original volume and takes the shape of worms. These worms can be pressed or rolled into any desired shape without any binder. The exfoliated graphite sheets show excellent electrical properties i.e. high dielectric constant (0 3 B 5 = 6.374x107) and comparatively low dielectric loss (tan 0 3 B 4 = 138) across the frequency in the range 50 Hz to 30 MHz and temperature in the range 40-300oC. The products developed from exfoliated graphite can have very good sealing applications in industrial areas, especially for gaskets in the automobile industries.
Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution... more Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were
prepared by solution blending. The homogeneity of GO dispersion with PVC
was confirmed by an optical microscope. Quality factor (Q-factor) as a function
of temperature (40–150 C) was measured within a broadband frequency
range of 50–35 MHz. The controlled GO loading demonstrates a crucial impact
on the optimization of the Q-factor, resonance frequency (f0) and wide bandwidth.
This nanocomposite may be well suited for electronic applications. The
further development of GO-reinforced polymer nanocomposites based on an
optimized Q-factor may result in a material for electromagnetic frequency
radiation shields for radar and communication towers/devices.
Polymer-Plastics Technology and Engineering, 2015
Materials Research Bulletin, 2013
Journal of Polymer Research, 2014
The synthesis of nickel chloride (NiCl2)-mixed with polyvinyl alcohol films of 15–20 μm in thickn... more The synthesis of nickel chloride (NiCl2)-mixed
with polyvinyl alcohol films of 15–20 μm in thickness has
been carried by solution blending technique. The dielectric
properties of the films have been measured in the frequency
range of 20 Hz to 1 MHz under a positive bias potential in
the range from 0 to 40 V. Improved electric characterization
was demonstrated due to ionic incorporation of NiCl2. The
low-frequency polarization was based on the Maxwell–
Wagner interfacial model. Hence, this composite film may
suggest as suitable electronic polar medium for versatile
low-frequency applications.
Polyvinyl alcohol (PVA) composed with polymethyl methacrylate (PMMA) polymer hydrogel was prepare... more Polyvinyl alcohol (PVA) composed with polymethyl
methacrylate (PMMA) polymer hydrogel was prepared by
using boric acid as a cross-linking agent. The semicrystalline
phase of composite gel was detected by X-ray diffraction tool.
The occupied polymer PMMA morphology exhibits crosslinked
alignment shown by scanning electron microscopy
(SEM). The two-polymer system demonstrates an excellent
dielectric property (with values, ε =590 for composite gel versus
400 compare to virgin PVA). The nonfluid media exhibit
the impulse DC bias polarization. The basic principle of this
work is to understand and control the electrical parameters
under external stimuli (field) response by Impedance tool. In
the biomedical field, this gel may be an excellent supporting
media for sonographic as one of the best polar medium.
Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO3) were prepared. ... more Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO3) were prepared.
Dopant incorporated and DC bias induced electrical parameters were disclosed with respect to pure PVA
film. The results demonstrate dielectric polarization is not only directly proportional to PbTiO3% of
dopant but also external DC bias potential at 30 C based on Maxwell Wagner theory. Hence these
properties highly applicable as super-capacitor film and humidity sensor applications.
Plastic and Reconstructive Surgery, 2014
The benefits of optimal pain management are well recognized. Nevertheless, treatment of postopera... more The benefits of optimal pain management are well recognized. Nevertheless, treatment of postoperative pain continues to be a major challenge, and inadequate postoperative pain relief remains disturbingly high. One of the reasons for suboptimal pain management may be related to inadequate or improper application of available analgesic therapies. Use of patient-specific and procedure-specific pain management strategies should improve pain control and consequently improve perioperative outcome, including early ambulation, ability to perform rehabilitation activities, and return to activities of daily living. This article discusses the current evidence that should allow improved postoperative pain control with emphasis on the use of procedure-specific pain management.
Ultramicroscopy, 2014
Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) have been applied to the char... more Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) have been applied to the characterization of composite samples formed by SrTiO 3 (STO) nanoparticles (NPs) and polyvinyl alcohol (PVA). The morphological features of the STO NPs were much better resolved using UFM than contactmode AFM topography. For high STO concentrations the individual STO NPs formed nanoclusters, which gathered in microaggregates. The STO aggregates, covered by PVA, exhibited no AFM frictional contrast, but were clearly distinguished from the PVA matrix using UFM. Similar aggregation was observed for NPs in the composite samples and for NPs deposited on top of a flat silicon substrate from milliQ water solution in the absence of polymer. In the hybrid films, most STO nanoparticles typically presented a lower UFM contrast than the PVA matrix, even though stiffer sample regions such as STO should give rise to a higher UFM contrast. STO NPs with intermediate contrast were characterized by an UFM halo of lower contrast at the PVA/STO interface. The results may be explained by considering that ultrasound is effectively damped on the nanometer scale at PVA/STO interfaces. According to our data, the nanoscale ultrasonic response at the PVA/STO interface plays a fundamental role in the UFM image contrast.
Journal of Electronic Materials, 2014
ABSTRACT Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by... more ABSTRACT Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution blending. The homogeneity of GO dispersion with PVC was confirmed by an optical microscope. Quality factor ( Q-factor) as a function of temperature (40-150 °C) was measured within a broadband frequency range of 50-35 MHz. The controlled GO loading demonstrates a crucial impact on the optimization of the Q-factor, resonance frequency ( f 0) and wide bandwidth. This nanocomposite may be well suited for electronic applications. The further development of GO-reinforced polymer nanocomposites based on an optimized Q-factor may result in a material for electromagnetic frequency radiation shields for radar and communication towers/devices.
Journal of Applied Polymer Science, 2006
Impedance analysis is the best technique to reveal the microstructural details of the polymeric m... more Impedance analysis is the best technique to reveal the microstructural details of the polymeric material. The dielectric polarization not only depends on physical and chemical properties, but also on the degree of polymerization (DP) of the polymeric material. In the present study, to understand the polarizing mechanism, two different molecular weights of polyvinyl alcohol (PVA) films were used for impedance analysis. Dielectric polarization of PVA film measured at normal temperature and pressure (NTP) condition by using LCR-4282A Impedance analyzer, within the frequency range 20 Hz to 1 MHz. The importance of inves-tigation is to know the simultaneous application of DC bias potential from 0 to 40 V with AC signal for measurement of over all electrical parameters. The result shows higher magnitude of dielectric constant for low-molecular weight (LMW) of PVA film in comparison to higher molecular weight (HMW), which is based on Maxwell-Wagner (M-W) theory.
Composite Interfaces, 2014
Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mech... more Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mechanical and thermal properties of polyvinyl alcohol (PVA) nanocomposites, Composite Interfaces, 21:6, 487-506, Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an 'anion-π' type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-mgraphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/ SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.
Current Applied Physics, 2011
Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO 3 ) were prepared... more Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO 3 ) were prepared. Dopant incorporated and DC bias induced electrical parameters were disclosed with respect to pure PVA film. The results demonstrate dielectric polarization is not only directly proportional to PbTiO 3 % of dopant but also external DC bias potential at 30 C based on Maxwell Wagner theory. Hence these properties highly applicable as super-capacitor film and humidity sensor applications.
Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-... more Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals
Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 ... more Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 into the polymer matrix using solution blending. The modified blends were characterized by X-ray diffraction, Thermogravimetric analysis, and Scanning electron microscopy. The crystalline to amorphous phase variation was confirmed by XRD with increase in the interplanar distance (d). TGA results indicate that the thermal stability of the modified blend was significantly improved as a function of alumina loading which may be due to interfacial interaction between the alumina particles and the polymers. Scanning electron microscopy studies reveal the presence of alumina particles resulting in plane surface morphology. The modified blends show very high dielectric constant value (10 5 –10 7) as a function of frequency (in the range 50 Hz–35 MHz) and temperature in the range (40–150 °C). The modified polymer blend demonstrate consistent polarization across the frequency band 50 Hz–10 kHz. The neutral aggregates formation due to higher concentration of alumina loading demonstrated an influence on AC conductivity. This investigation can be feasible for electronic and electrical engineering application as the dielectric medium.
Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 ... more Polycarbonate (PC) and Poly (methyl methacrylate) blends were prepared by incorporating Al 2 O 3 into the polymer matrix using solution blending. The modified blends were characterized by X-ray diffraction, Thermogravimetric analysis, and Scanning electron microscopy. The crystalline to amorphous phase variation was confirmed by XRD with increase in the interplanar distance (d). TGA results indicate that the thermal stability of the modified blend was significantly improved as a function of alumina loading which may be due to interfacial interaction between the alumina particles and the polymers. Scanning electron microscopy studies reveal the presence of alumina particles resulting in plane surface morphology. The modified blends show very high dielectric constant value (10 5 –10 7) as a function of frequency (in the range 50 Hz–35 MHz) and temperature in the range (40–150 °C). The modified polymer blend demonstrate consistent polarization across the frequency band 50 Hz–10 kHz. The neutral aggregates formation due to higher concentration of alumina loading demonstrated an influence on AC conductivity. This investigation can be feasible for electronic and electrical engineering application as the dielectric medium.
We demonstrated the modification of Isophthalic polyester (IP) resin/styrene in situ blends by di... more We demonstrated the modification of Isophthalic polyester (IP) resin/styrene in situ blends by dispersion of nano perovskite strontium titanate nanoparticles (STONP). The thermal stability of prepared sample was examined by differential scanning calorimetry. The variation of glass transition temperature of IP resin on styrene and filler content reflects the elastic network of the polymer chain, miscibility of polystyrene and IP resin and phase separation between filler and polymer matrix. The phase separation and morphology of the blend was confirmed by scanning electron microscope and energy dispersive X-ray spectroscopy as a function of STONP loading. The dielectric property of IP resin/styrene/STONP was analyzed as a function of frequency (50 Hz-10 MHz) and temperature (40-150°C). Two relaxation process was clearly identified namely Maxwell-Wagner-Siller effect corresponds to low frequency polarization and a-relaxation corresponds to glass transition effect followed by Vogel-Fulcher-Tamman equation (VTF equation). We disclosed the improvement of dielectric properties as a function of STONP loading. This investigation is highly useful in the electronics domain.
Composite Interfaces, 2014
Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mech... more Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mechanical and thermal properties of polyvinyl alcohol (PVA) nanocomposites, Composite Interfaces, 21:6, 487-506, Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an 'anion-π' type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-mgraphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/ SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.
In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical t... more In the present investigation, exfoliated graphite sheets were obtained from the thermo-chemical treatment of natural graphite flakes. In this process, the graphite expands almost 300 – 350 times of its original volume and takes the shape of worms. These worms can be pressed or rolled into any desired shape without any binder. The exfoliated graphite sheets show excellent electrical properties i.e. high dielectric constant (0 3 B 5 = 6.374x107) and comparatively low dielectric loss (tan 0 3 B 4 = 138) across the frequency in the range 50 Hz to 30 MHz and temperature in the range 40-300oC. The products developed from exfoliated graphite can have very good sealing applications in industrial areas, especially for gaskets in the automobile industries.
Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution... more Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were
prepared by solution blending. The homogeneity of GO dispersion with PVC
was confirmed by an optical microscope. Quality factor (Q-factor) as a function
of temperature (40–150 C) was measured within a broadband frequency
range of 50–35 MHz. The controlled GO loading demonstrates a crucial impact
on the optimization of the Q-factor, resonance frequency (f0) and wide bandwidth.
This nanocomposite may be well suited for electronic applications. The
further development of GO-reinforced polymer nanocomposites based on an
optimized Q-factor may result in a material for electromagnetic frequency
radiation shields for radar and communication towers/devices.
Polymer-Plastics Technology and Engineering, 2015
Materials Research Bulletin, 2013
Journal of Polymer Research, 2014
The synthesis of nickel chloride (NiCl2)-mixed with polyvinyl alcohol films of 15–20 μm in thickn... more The synthesis of nickel chloride (NiCl2)-mixed
with polyvinyl alcohol films of 15–20 μm in thickness has
been carried by solution blending technique. The dielectric
properties of the films have been measured in the frequency
range of 20 Hz to 1 MHz under a positive bias potential in
the range from 0 to 40 V. Improved electric characterization
was demonstrated due to ionic incorporation of NiCl2. The
low-frequency polarization was based on the Maxwell–
Wagner interfacial model. Hence, this composite film may
suggest as suitable electronic polar medium for versatile
low-frequency applications.
Polyvinyl alcohol (PVA) composed with polymethyl methacrylate (PMMA) polymer hydrogel was prepare... more Polyvinyl alcohol (PVA) composed with polymethyl
methacrylate (PMMA) polymer hydrogel was prepared by
using boric acid as a cross-linking agent. The semicrystalline
phase of composite gel was detected by X-ray diffraction tool.
The occupied polymer PMMA morphology exhibits crosslinked
alignment shown by scanning electron microscopy
(SEM). The two-polymer system demonstrates an excellent
dielectric property (with values, ε =590 for composite gel versus
400 compare to virgin PVA). The nonfluid media exhibit
the impulse DC bias polarization. The basic principle of this
work is to understand and control the electrical parameters
under external stimuli (field) response by Impedance tool. In
the biomedical field, this gel may be an excellent supporting
media for sonographic as one of the best polar medium.
Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO3) were prepared. ... more Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO3) were prepared.
Dopant incorporated and DC bias induced electrical parameters were disclosed with respect to pure PVA
film. The results demonstrate dielectric polarization is not only directly proportional to PbTiO3% of
dopant but also external DC bias potential at 30 C based on Maxwell Wagner theory. Hence these
properties highly applicable as super-capacitor film and humidity sensor applications.
Plastic and Reconstructive Surgery, 2014
The benefits of optimal pain management are well recognized. Nevertheless, treatment of postopera... more The benefits of optimal pain management are well recognized. Nevertheless, treatment of postoperative pain continues to be a major challenge, and inadequate postoperative pain relief remains disturbingly high. One of the reasons for suboptimal pain management may be related to inadequate or improper application of available analgesic therapies. Use of patient-specific and procedure-specific pain management strategies should improve pain control and consequently improve perioperative outcome, including early ambulation, ability to perform rehabilitation activities, and return to activities of daily living. This article discusses the current evidence that should allow improved postoperative pain control with emphasis on the use of procedure-specific pain management.
Ultramicroscopy, 2014
Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) have been applied to the char... more Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) have been applied to the characterization of composite samples formed by SrTiO 3 (STO) nanoparticles (NPs) and polyvinyl alcohol (PVA). The morphological features of the STO NPs were much better resolved using UFM than contactmode AFM topography. For high STO concentrations the individual STO NPs formed nanoclusters, which gathered in microaggregates. The STO aggregates, covered by PVA, exhibited no AFM frictional contrast, but were clearly distinguished from the PVA matrix using UFM. Similar aggregation was observed for NPs in the composite samples and for NPs deposited on top of a flat silicon substrate from milliQ water solution in the absence of polymer. In the hybrid films, most STO nanoparticles typically presented a lower UFM contrast than the PVA matrix, even though stiffer sample regions such as STO should give rise to a higher UFM contrast. STO NPs with intermediate contrast were characterized by an UFM halo of lower contrast at the PVA/STO interface. The results may be explained by considering that ultrasound is effectively damped on the nanometer scale at PVA/STO interfaces. According to our data, the nanoscale ultrasonic response at the PVA/STO interface plays a fundamental role in the UFM image contrast.
Journal of Electronic Materials, 2014
ABSTRACT Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by... more ABSTRACT Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution blending. The homogeneity of GO dispersion with PVC was confirmed by an optical microscope. Quality factor ( Q-factor) as a function of temperature (40-150 °C) was measured within a broadband frequency range of 50-35 MHz. The controlled GO loading demonstrates a crucial impact on the optimization of the Q-factor, resonance frequency ( f 0) and wide bandwidth. This nanocomposite may be well suited for electronic applications. The further development of GO-reinforced polymer nanocomposites based on an optimized Q-factor may result in a material for electromagnetic frequency radiation shields for radar and communication towers/devices.
Journal of Applied Polymer Science, 2006
Impedance analysis is the best technique to reveal the microstructural details of the polymeric m... more Impedance analysis is the best technique to reveal the microstructural details of the polymeric material. The dielectric polarization not only depends on physical and chemical properties, but also on the degree of polymerization (DP) of the polymeric material. In the present study, to understand the polarizing mechanism, two different molecular weights of polyvinyl alcohol (PVA) films were used for impedance analysis. Dielectric polarization of PVA film measured at normal temperature and pressure (NTP) condition by using LCR-4282A Impedance analyzer, within the frequency range 20 Hz to 1 MHz. The importance of inves-tigation is to know the simultaneous application of DC bias potential from 0 to 40 V with AC signal for measurement of over all electrical parameters. The result shows higher magnitude of dielectric constant for low-molecular weight (LMW) of PVA film in comparison to higher molecular weight (HMW), which is based on Maxwell-Wagner (M-W) theory.
Composite Interfaces, 2014
Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mech... more Effect of sodium alginate modification of graphene (by 'anion-π' type of interaction) on the mechanical and thermal properties of polyvinyl alcohol (PVA) nanocomposites, Composite Interfaces, 21:6, 487-506, Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an 'anion-π' type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-mgraphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/ SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.
Current Applied Physics, 2011
Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO 3 ) were prepared... more Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO 3 ) were prepared. Dopant incorporated and DC bias induced electrical parameters were disclosed with respect to pure PVA film. The results demonstrate dielectric polarization is not only directly proportional to PbTiO 3 % of dopant but also external DC bias potential at 30 C based on Maxwell Wagner theory. Hence these properties highly applicable as super-capacitor film and humidity sensor applications.