Dale W Schaefer - Academia.edu (original) (raw)

Papers by Dale W Schaefer

Research paper thumbnail of Multiple Size Scale Structures in Silica—Siloxane Composites Studied by Small-Angle Scattering

ACS Symposium Series, 1995

Research paper thumbnail of The Polysiloxanes

Polysiloxanes are the most studied inorganic and semi-inorganic polymers because of their many me... more Polysiloxanes are the most studied inorganic and semi-inorganic polymers because of their many medical and commercial uses. The Si-O backbone endows polysiloxanes with intriguing properties: the strength of the Si-O bond imparts considerable thermal stability, and the nature of the bonding imparts low surface free energy. Prostheses, artificial organs, objects for facial reconstruction, vitreous substitutes in the eyes, and tubing take advantage of the stability and pliability of polysiloxanes. Artificial skin, contact lenses, and drug delivery systems utilize their high permeability. Such biomedical applications have led to biocompatibility studies on the interactions of polysiloxanes with proteins, and there has been interest in modifying these materials to improve their suitability for general biomedical application. Polysiloxanes examines novel aspects of polysiloxane science and engineering, including properties, work in progress, and important unsolved problems. The volume, wi...

Research paper thumbnail of Engineered Porous Materials EXPO ′93

Materials Technology, 1994

any agency thereof, nor any of their employees, nor any of their contractors, subcc,_tractors, or... more any agency thereof, nor any of their employees, nor any of their contractors, subcc,_tractors, or their employees, makes any warranty, expresb or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trad-name, trademark, manufacturer, or otherwise, does not necessarily constitute orimplyits endorsement, recommendation, orfavoring by the United StatesGovernment,any agencythereof or any of their contractors orsubcontractors. The viewsand opinions expressed herein do notnecessarily state or reflect thoseoftheUnitedStates Government, any agencythereof or anyoftheir contractors. Prin_d in the United States of America. This report has been reproduced directly from the best available copy.

Research paper thumbnail of Interface morphology and phase separation in polymer-dispersed liquid crystal composites

Polymer, 2005

It is widely appreciated that electro-optic activity in polymer-dispersed liquid crystals (PDLCs)... more It is widely appreciated that electro-optic activity in polymer-dispersed liquid crystals (PDLCs) depends on separation of the polymer and liquid crystal (LC) phases. Since the phase structure develops in a non-equilibrium system, the morphology of the LC domains depends on the details of the chemical and physical processes active during domain formation. The nature of the interface between the polymer

Research paper thumbnail of Effect of silica nanoparticles on morphology of segmented polyurethanes

Two series of segmented polyurethanes having soft segment concentration of 50 and 70 wt%, and dif... more Two series of segmented polyurethanes having soft segment concentration of 50 and 70 wt%, and different concentrations of nanometerdiameter silica were prepared and tested. Atomic force microscopy revealed a strong effect of nanoparticles on the large-scale spherulitic morphology of the hard domains. Addition of silica suppresses fibril formation in spherulites. Filler particles were evenly distributed in the hard and soft phase. Nano-silica affected the melting point of the hard phase only at loadings .30 wt% silica. A single melting peak was observed at higher filler loadings. There is no clear effect of the filler on the glass transition of soft segments. Wide-angle X-ray diffraction showed decreasing crystallinity of the hard domains with increasing filler concentration in samples with 70 wt% soft segment. Ultra smallangle X-ray scattering confirms the existence of nanometer phase-separated domains in the unfilled sample. These domains are disrupted in the presence of nano-silica. The picture that emerges is that nano-silica suppresses short-scale phase separation of the hard and soft segments. Undoubtedly, the formation of fibrils on larger scales is related to short-scale segment segregation, so when the latter is suppressed by the presence of silica, fibril growth is also impeded.

Research paper thumbnail of Highly dispersed nanosilica–epoxy resins with enhanced mechanical properties

Polymer, 2008

Epoxy-nanocomposite resins filled with 12-nm spherical silica particles were investigated for the... more Epoxy-nanocomposite resins filled with 12-nm spherical silica particles were investigated for their thermal and mechanical properties as a function of silica loading. The nanoparticles were easily dispersed with minimal aggregation for loadings up to 25 wt% as determined using transmission electron microscopy (TEM) and ultra-small-angle X-ray scattering (USAXS). A proportional decrease in cure temperatures and glass transition temperature (for loadings of 10 wt% and above) was observed with increased silica loading. The morphology determined by USAXS is consistent with a zone around the silica particles from which neighboring particles are excluded. The ''exclusion zone'' extends to 10Â the particle diameter. For samples with loadings less than 10 wt%, increases of 25% in tensile modulus and 30% in fracture toughness were obtained. More highly loaded samples continued to increase in modulus, but decreased in strength and fracture toughness. Overall, the addition of nanosilica is shown as a promising method for property enhancement of aerospace epoxy composite resins.

Research paper thumbnail of Polymers, Fractals, and Ceramic Materials

Research paper thumbnail of Hierarchical morphology of carbon single-walled nanotubes during sonication in an aliphatic diamine

Polymer, 2005

Dispersion of single-walled carbon nanotubes (SWNTs) by sonication into diamine curing agents is ... more Dispersion of single-walled carbon nanotubes (SWNTs) by sonication into diamine curing agents is studied as a means to improve the dispersion of SWNTs in cured epoxy. Cured and uncured specimens are analyzed by light microscopy, electron microscopy, light scattering (LS), ultra small-angle X-ray scattering (USAXS), electrical conductivity and Raman spectroscopy. A flexible diamine (D2000) forms a stable SWNT suspension leading

Research paper thumbnail of How Does Surface Modification Aid in the Dispersion of Carbon Nanofibers?

Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nano... more Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nanofibers suspended in water. These data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (small bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. The time evolution of the small-scale bundles is studied by extracting the size distribution from the angle-dependence of the scattered intensity, using the maximum entropy method in conjunction with a simplified tube form factor. The bundles consist of multiple tubes possibly aggregated side-by-side. Acid oxidation has little effect on this bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. T...

Research paper thumbnail of Synthesis and Characterization of Fillers of Controlled Structure Based on Polyhedral Oligomeric Silsesquioxane Cages and Their Use In Reinforcing Siloxane Elastomers

Journal of Polymer Science …, 2003

2Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, 45... more 2Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, 45221-0012 ... 3Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, 45221 ... Received 1 February 2003; revised 14 April 2003; accepted 15 April 2003

Research paper thumbnail of Statistics of light scattered by non-Gaussian fluctuations

In Coherence and Quantum Optics: Proceedings of the Third Rochester Conference on Coherence and Quantum Optics held at the University of Rochester, 1972

In most scattering experiments the scattered light field represents a chaotic superposition of fi... more In most scattering experiments the scattered light field represents a chaotic superposition of fields scattered from a large number of individual scatterers and therefore obeys Gaussian statistics [1]. That is, the amplitude distribution of the fluctuating scattered field is Gaussian. It is the purpose of this paper to investigate the single time-interval statistics of the scattered light when the number of scatterers is not large. Under these conditions the scattered field is not Gaussian.

Research paper thumbnail of Morphological Characterization of Carbon-Nanofiber-Reinforced Epoxy Nanocomposites Using Ultra-Small Angle Scattering

… Materials Science and …, 2005

Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs)... more Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs) can be found throughout the literature.1-5 Electrical, mechanical, viscoelastic, and rheological properties are just a few of the characteristics that have been well discussed.1-5 Although ...

Research paper thumbnail of Light scattering from non-Gaussian concentration fluctuations

Research paper thumbnail of Fractal Geometry of Colloidal Aggregates

Physical Review Letters, 1984

Fractal Geometry of Colloidal Aggregates. Dale W. Schaefer and James E. Martin Sandia National La... more Fractal Geometry of Colloidal Aggregates. Dale W. Schaefer and James E. Martin Sandia National Laboratories, Albuquerque, New Mexico 87185. Pierre Wiltzius and David S. Cannell Department of Physics, University of California, Santa Barbara, California 93106. ...

Research paper thumbnail of Phase behavior of the liquid crystal 8CB in a silica aerogel

Physical review letters, 1992

Light scattering and precision calorimetry show that the nematic ordering of octylcyanobiphenyl (... more Light scattering and precision calorimetry show that the nematic ordering of octylcyanobiphenyl (8CB) filling the connected network of pores of a silica aerogel does not occur via the first-order phase transition characteristic of the bulk. Rather, ordering is ...

Research paper thumbnail of Integrated chemical systems: the simultaneous formation of hybrid nanocomposites of iron oxide and organo silsesquioxanes

Chemistry of …, 2005

Integrated Chemical Systems: the Simultaneous Formation of Hybrid Nanocomposites of Iron Oxide an... more Integrated Chemical Systems: the Simultaneous Formation of Hybrid Nanocomposites of Iron Oxide and Organo Silsesquioxanes A sol-gel approach for the synthesis of hybrid nanocomposites of iron oxide and bridged polysilsesquioxanes has been developed. The hybrid nanocomposites exhibit a uniform dispersion of both components at length scales > 5 nm.

Research paper thumbnail of Challenges and opportunities in complex materials: silica-reinforced elastomers

... b, Bridgestone Firestone Inc, 1200 Firestone Parkway, Arkon, OH 44317-0001, USA. c, Universit... more ... b, Bridgestone Firestone Inc, 1200 Firestone Parkway, Arkon, OH 44317-0001, USA. c, University of Maryland at College Park, College Park, MD 20742, USA. d, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ...

Research paper thumbnail of Preparation and Characterization of Some Unusually Transparent Poly (Dimethylsiloxane) Nanocomposites

Journal of Polymer …, 2003

2Department of Chemical Engineering, Yeungnam University, Gyungsan 712-749, Korea ... 3Department... more 2Department of Chemical Engineering, Yeungnam University, Gyungsan 712-749, Korea ... 3Department of Chemical and Materials Engineering, The University of Cincinnati, Cincinnati, Ohio 45221 ... Received 10 September 2002; revised 28 March 2003; ...

Research paper thumbnail of Schaefer Precursor Chemistry and the Structure of Silica Aerogels

Research paper thumbnail of Effect of impaired twitching motility and biofilm dispersion on performance of Pseudomonas aeruginosa-powered microbial fuel cells

Journal of industrial microbiology & biotechnology, 2018

Pseudomonas aeruginosa is a metabolically voracious bacterium that is easily manipulated genetica... more Pseudomonas aeruginosa is a metabolically voracious bacterium that is easily manipulated genetically. We have previously shown that the organism is also highly electrogenic in microbial fuel cells (MFCs). Polarization studies were performed in MFCs with wild-type strain PAO1 and three mutant strains (pilT, bdlA and pilT bdlA). The pilT mutant was hyperpiliated, while the bdlA mutant was suppressed in biofilm dispersion chemotaxis. The double pilT bdlA mutant was expected to have properties of both mutations. Polarization data indicate that the pilT mutant showed 5.0- and 3.2-fold increases in peak power compared to the wild type and the pilT bdlA mutant, respectively. The performance of the bdlA mutant was surprisingly the lowest, while the pilT bdlA electrogenic performance fell between the pilT mutant and wild-type bacteria. Measurements of biofilm thickness and bacterial viability showed equal viability among the different strains. The thickness of the bdlA mutant, however, was t...

Research paper thumbnail of Multiple Size Scale Structures in Silica—Siloxane Composites Studied by Small-Angle Scattering

ACS Symposium Series, 1995

Research paper thumbnail of The Polysiloxanes

Polysiloxanes are the most studied inorganic and semi-inorganic polymers because of their many me... more Polysiloxanes are the most studied inorganic and semi-inorganic polymers because of their many medical and commercial uses. The Si-O backbone endows polysiloxanes with intriguing properties: the strength of the Si-O bond imparts considerable thermal stability, and the nature of the bonding imparts low surface free energy. Prostheses, artificial organs, objects for facial reconstruction, vitreous substitutes in the eyes, and tubing take advantage of the stability and pliability of polysiloxanes. Artificial skin, contact lenses, and drug delivery systems utilize their high permeability. Such biomedical applications have led to biocompatibility studies on the interactions of polysiloxanes with proteins, and there has been interest in modifying these materials to improve their suitability for general biomedical application. Polysiloxanes examines novel aspects of polysiloxane science and engineering, including properties, work in progress, and important unsolved problems. The volume, wi...

Research paper thumbnail of Engineered Porous Materials EXPO ′93

Materials Technology, 1994

any agency thereof, nor any of their employees, nor any of their contractors, subcc,_tractors, or... more any agency thereof, nor any of their employees, nor any of their contractors, subcc,_tractors, or their employees, makes any warranty, expresb or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trad-name, trademark, manufacturer, or otherwise, does not necessarily constitute orimplyits endorsement, recommendation, orfavoring by the United StatesGovernment,any agencythereof or any of their contractors orsubcontractors. The viewsand opinions expressed herein do notnecessarily state or reflect thoseoftheUnitedStates Government, any agencythereof or anyoftheir contractors. Prin_d in the United States of America. This report has been reproduced directly from the best available copy.

Research paper thumbnail of Interface morphology and phase separation in polymer-dispersed liquid crystal composites

Polymer, 2005

It is widely appreciated that electro-optic activity in polymer-dispersed liquid crystals (PDLCs)... more It is widely appreciated that electro-optic activity in polymer-dispersed liquid crystals (PDLCs) depends on separation of the polymer and liquid crystal (LC) phases. Since the phase structure develops in a non-equilibrium system, the morphology of the LC domains depends on the details of the chemical and physical processes active during domain formation. The nature of the interface between the polymer

Research paper thumbnail of Effect of silica nanoparticles on morphology of segmented polyurethanes

Two series of segmented polyurethanes having soft segment concentration of 50 and 70 wt%, and dif... more Two series of segmented polyurethanes having soft segment concentration of 50 and 70 wt%, and different concentrations of nanometerdiameter silica were prepared and tested. Atomic force microscopy revealed a strong effect of nanoparticles on the large-scale spherulitic morphology of the hard domains. Addition of silica suppresses fibril formation in spherulites. Filler particles were evenly distributed in the hard and soft phase. Nano-silica affected the melting point of the hard phase only at loadings .30 wt% silica. A single melting peak was observed at higher filler loadings. There is no clear effect of the filler on the glass transition of soft segments. Wide-angle X-ray diffraction showed decreasing crystallinity of the hard domains with increasing filler concentration in samples with 70 wt% soft segment. Ultra smallangle X-ray scattering confirms the existence of nanometer phase-separated domains in the unfilled sample. These domains are disrupted in the presence of nano-silica. The picture that emerges is that nano-silica suppresses short-scale phase separation of the hard and soft segments. Undoubtedly, the formation of fibrils on larger scales is related to short-scale segment segregation, so when the latter is suppressed by the presence of silica, fibril growth is also impeded.

Research paper thumbnail of Highly dispersed nanosilica–epoxy resins with enhanced mechanical properties

Polymer, 2008

Epoxy-nanocomposite resins filled with 12-nm spherical silica particles were investigated for the... more Epoxy-nanocomposite resins filled with 12-nm spherical silica particles were investigated for their thermal and mechanical properties as a function of silica loading. The nanoparticles were easily dispersed with minimal aggregation for loadings up to 25 wt% as determined using transmission electron microscopy (TEM) and ultra-small-angle X-ray scattering (USAXS). A proportional decrease in cure temperatures and glass transition temperature (for loadings of 10 wt% and above) was observed with increased silica loading. The morphology determined by USAXS is consistent with a zone around the silica particles from which neighboring particles are excluded. The ''exclusion zone'' extends to 10Â the particle diameter. For samples with loadings less than 10 wt%, increases of 25% in tensile modulus and 30% in fracture toughness were obtained. More highly loaded samples continued to increase in modulus, but decreased in strength and fracture toughness. Overall, the addition of nanosilica is shown as a promising method for property enhancement of aerospace epoxy composite resins.

Research paper thumbnail of Polymers, Fractals, and Ceramic Materials

Research paper thumbnail of Hierarchical morphology of carbon single-walled nanotubes during sonication in an aliphatic diamine

Polymer, 2005

Dispersion of single-walled carbon nanotubes (SWNTs) by sonication into diamine curing agents is ... more Dispersion of single-walled carbon nanotubes (SWNTs) by sonication into diamine curing agents is studied as a means to improve the dispersion of SWNTs in cured epoxy. Cured and uncured specimens are analyzed by light microscopy, electron microscopy, light scattering (LS), ultra small-angle X-ray scattering (USAXS), electrical conductivity and Raman spectroscopy. A flexible diamine (D2000) forms a stable SWNT suspension leading

Research paper thumbnail of How Does Surface Modification Aid in the Dispersion of Carbon Nanofibers?

Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nano... more Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nanofibers suspended in water. These data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (small bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. The time evolution of the small-scale bundles is studied by extracting the size distribution from the angle-dependence of the scattered intensity, using the maximum entropy method in conjunction with a simplified tube form factor. The bundles consist of multiple tubes possibly aggregated side-by-side. Acid oxidation has little effect on this bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. T...

Research paper thumbnail of Synthesis and Characterization of Fillers of Controlled Structure Based on Polyhedral Oligomeric Silsesquioxane Cages and Their Use In Reinforcing Siloxane Elastomers

Journal of Polymer Science …, 2003

2Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, 45... more 2Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, 45221-0012 ... 3Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, 45221 ... Received 1 February 2003; revised 14 April 2003; accepted 15 April 2003

Research paper thumbnail of Statistics of light scattered by non-Gaussian fluctuations

In Coherence and Quantum Optics: Proceedings of the Third Rochester Conference on Coherence and Quantum Optics held at the University of Rochester, 1972

In most scattering experiments the scattered light field represents a chaotic superposition of fi... more In most scattering experiments the scattered light field represents a chaotic superposition of fields scattered from a large number of individual scatterers and therefore obeys Gaussian statistics [1]. That is, the amplitude distribution of the fluctuating scattered field is Gaussian. It is the purpose of this paper to investigate the single time-interval statistics of the scattered light when the number of scatterers is not large. Under these conditions the scattered field is not Gaussian.

Research paper thumbnail of Morphological Characterization of Carbon-Nanofiber-Reinforced Epoxy Nanocomposites Using Ultra-Small Angle Scattering

… Materials Science and …, 2005

Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs)... more Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs) can be found throughout the literature.1-5 Electrical, mechanical, viscoelastic, and rheological properties are just a few of the characteristics that have been well discussed.1-5 Although ...

Research paper thumbnail of Light scattering from non-Gaussian concentration fluctuations

Research paper thumbnail of Fractal Geometry of Colloidal Aggregates

Physical Review Letters, 1984

Fractal Geometry of Colloidal Aggregates. Dale W. Schaefer and James E. Martin Sandia National La... more Fractal Geometry of Colloidal Aggregates. Dale W. Schaefer and James E. Martin Sandia National Laboratories, Albuquerque, New Mexico 87185. Pierre Wiltzius and David S. Cannell Department of Physics, University of California, Santa Barbara, California 93106. ...

Research paper thumbnail of Phase behavior of the liquid crystal 8CB in a silica aerogel

Physical review letters, 1992

Light scattering and precision calorimetry show that the nematic ordering of octylcyanobiphenyl (... more Light scattering and precision calorimetry show that the nematic ordering of octylcyanobiphenyl (8CB) filling the connected network of pores of a silica aerogel does not occur via the first-order phase transition characteristic of the bulk. Rather, ordering is ...

Research paper thumbnail of Integrated chemical systems: the simultaneous formation of hybrid nanocomposites of iron oxide and organo silsesquioxanes

Chemistry of …, 2005

Integrated Chemical Systems: the Simultaneous Formation of Hybrid Nanocomposites of Iron Oxide an... more Integrated Chemical Systems: the Simultaneous Formation of Hybrid Nanocomposites of Iron Oxide and Organo Silsesquioxanes A sol-gel approach for the synthesis of hybrid nanocomposites of iron oxide and bridged polysilsesquioxanes has been developed. The hybrid nanocomposites exhibit a uniform dispersion of both components at length scales > 5 nm.

Research paper thumbnail of Challenges and opportunities in complex materials: silica-reinforced elastomers

... b, Bridgestone Firestone Inc, 1200 Firestone Parkway, Arkon, OH 44317-0001, USA. c, Universit... more ... b, Bridgestone Firestone Inc, 1200 Firestone Parkway, Arkon, OH 44317-0001, USA. c, University of Maryland at College Park, College Park, MD 20742, USA. d, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ...

Research paper thumbnail of Preparation and Characterization of Some Unusually Transparent Poly (Dimethylsiloxane) Nanocomposites

Journal of Polymer …, 2003

2Department of Chemical Engineering, Yeungnam University, Gyungsan 712-749, Korea ... 3Department... more 2Department of Chemical Engineering, Yeungnam University, Gyungsan 712-749, Korea ... 3Department of Chemical and Materials Engineering, The University of Cincinnati, Cincinnati, Ohio 45221 ... Received 10 September 2002; revised 28 March 2003; ...

Research paper thumbnail of Schaefer Precursor Chemistry and the Structure of Silica Aerogels

Research paper thumbnail of Effect of impaired twitching motility and biofilm dispersion on performance of Pseudomonas aeruginosa-powered microbial fuel cells

Journal of industrial microbiology & biotechnology, 2018

Pseudomonas aeruginosa is a metabolically voracious bacterium that is easily manipulated genetica... more Pseudomonas aeruginosa is a metabolically voracious bacterium that is easily manipulated genetically. We have previously shown that the organism is also highly electrogenic in microbial fuel cells (MFCs). Polarization studies were performed in MFCs with wild-type strain PAO1 and three mutant strains (pilT, bdlA and pilT bdlA). The pilT mutant was hyperpiliated, while the bdlA mutant was suppressed in biofilm dispersion chemotaxis. The double pilT bdlA mutant was expected to have properties of both mutations. Polarization data indicate that the pilT mutant showed 5.0- and 3.2-fold increases in peak power compared to the wild type and the pilT bdlA mutant, respectively. The performance of the bdlA mutant was surprisingly the lowest, while the pilT bdlA electrogenic performance fell between the pilT mutant and wild-type bacteria. Measurements of biofilm thickness and bacterial viability showed equal viability among the different strains. The thickness of the bdlA mutant, however, was t...