@article{stano_faraji_yildiz_akyildiz_bradford_jur_2017, title={Strong and resilient alumina nanotube and CNT/alumina hybrid foams with tuneable elastic properties}, volume={7}, ISSN={["2046-2069"]}, DOI={10.1039/c7ra02452e}, abstractNote={Alumina foams from anisotropic structured carbon nanotube structures are studied for their unique mechanical and thermal performance characteristics.}, number={45}, journal={RSC ADVANCES}, author={Stano, Kelly L. and Faraji, Shaghayegh and Yildiz, Ozkan and Akyildiz, Halil and Bradford, Philip D. and Jur, Jesse S.}, year={2017}, pages={27923–27931} } @inproceedings{nagavalli_hummel_akyildiz_morton-aslanis_barker_2016, title={Advanced layering system and design for the increased thermal protection of wildland fire shelters}, volume={1593}, DOI={10.1520/stp159320160014}, booktitle={American society for testing and materials special technical}, author={Nagavalli, A. and Hummel, A. and Akyildiz, H. I. and Morton-Aslanis, J. and Barker, R.}, year={2016}, pages={102–116} } @article{akyildiz_stano_roberts_everitt_jur_2016, title={Photoluminescence Mechanism and Photocatalytic Activity of Organic-Inorganic Hybrid Materials Formed by Sequential Vapor Infiltration}, volume={32}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.6b00285}, abstractNote={Organic-inorganic hybrid materials formed by sequential vapor infiltration (SVI) of trimethylaluminum into polyester fibers are demonstrated, and the photoluminescence of the fibers is evaluated using a combined UV-vis and photoluminescence excitation (PLE) spectroscopy approach. The optical activity of the modified fibers depends on infiltration thermal processing conditions and is attributed to the reaction mechanisms taking place at different temperatures. At low temperatures a single excitation band and dual emission bands are observed, while, at high temperatures, two distinct absorption bands and one emission band are observed, suggesting that the physical and chemical structure of the resulting hybrid material depends on the SVI temperature. Along with enhancing the photoluminescence intensity of the PET fibers, the internal quantum efficiency also increased to 5-fold from ∼4-5% to ∼24%. SVI processing also improved the photocatalytic activity of the fibers, as demonstrated by photodeposition of Ag and Au metal particles out of an aqueous metal salt solution onto fiber surfaces via UVA light exposure. Toward applications in flexible electronics, well-defined patterning of the metallic materials is achieved by using light masking and focused laser rastering approaches.}, number={17}, journal={LANGMUIR}, author={Akyildiz, Halil I. and Stano, Kelly L. and Roberts, Adam T. and Everitt, Henry O. and Jur, Jesse S.}, year={2016}, month={May}, pages={4289–4296} } @article{stano_faraji_hodges_yildiz_wells_akyildiz_zhao_jur_bradford_2016, title={Ultralight Interconnected Metal Oxide Nanotube Networks}, volume={12}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201503267}, abstractNote={Record-breaking ultralow density aluminum oxide structures are prepared using a novel templating technique. The alumina structures are unique in that they are comprised by highly aligned and interconnected nanotubes yielding anisotropic behavior. Large-scale network structures with complex form-factors can easily be made using this technique. The application of the low density networks as humidity sensing materials as well as thermal insulation is demonstrated.}, number={18}, journal={SMALL}, author={Stano, Kelly L. and Faraji, Shaghayegh and Hodges, Ryan and Yildiz, Ozkan and Wells, Brian and Akyildiz, Halil I. and Zhao, Junjie and Jur, Jesse and Bradford, Philip D.}, year={2016}, month={May}, pages={2432–2438} } @article{akyildiz_mousa_jur_2015, title={Atmospheric pressure synthesis of photoluminescent hybrid materials by sequential organometallic vapor infiltration into polyethylene terephthalate fibers}, volume={117}, ISSN={["1089-7550"]}, DOI={10.1063/1.4906406}, abstractNote={Exposing a polymer to sequential organometallic vapor infiltration (SVI) under low pressure conditions can significantly modify the polymer's chemical, mechanical, and optical properties. We demonstrate that SVI of trimethylaluminum into polyethylene terephthalate (PET) can also proceed readily at atmospheric pressure, and at 60 °C the extent of reaction determined by mass uptake is independent of pressure between 2.5 Torr and 760 Torr. At 120 °C, however, the mass gain is 50% larger at 2.5 Torr relative to that at 760 Torr, indicating that the precursor diffusion in the chamber and fiber matrix decreases at higher source pressure. Mass gain decreases, in general, as the SVI process temperature increases both at 2.5 Torr and 760 Torr attributed to the faster reaction kinetics forming a barrier layer, which prevents further diffusion of the reactive species. The resulting PET/Al-Ox product shows high photoluminescence compared to untreated fibers. A physical mask on the polymer during infiltration at 760 Torr is replicated in the underlying polymer, producing an image in the polymer that is visible under UV illumination. Because of the reduced precursor diffusivity during exposure at 760 Torr, the image shows improved resolution compared to SVI performed under typical 2.5 Torr conditions.}, number={4}, journal={JOURNAL OF APPLIED PHYSICS}, author={Akyildiz, Halil I. and Mousa, Moataz Bellah M. and Jur, Jesse S.}, year={2015}, month={Jan} } @article{marcott_lo_dillon_akyildiz_jur_2015, title={Depth profiling trimethylaluminum-modified PET fibers by nanoscale infrared spectroscopy}, volume={47}, number={2}, journal={American Laboratory}, author={Marcott, C. and Lo, M. and Dillon, E. and Akyildiz, H. I. and Jur, J. S.}, year={2015}, pages={12–14} } @article{akyildiz_jur_2015, title={Organometallic exposure dependence on organic-inorganic hybrid material formation in polyethylene terephthalate and polyamide 6 polymer fibers}, volume={33}, ISSN={["1520-8559"]}, DOI={10.1116/1.4907563}, abstractNote={The effect of exposure conditions and surface area on hybrid material formation during sequential vapor infiltrations of trimethylaluminum (TMA) into polyamide 6 (PA6) and polyethylene terephthalate (PET) fibers is investigated. Mass gain of the fabric samples after infiltration was examined to elucidate the reaction extent with increasing number of sequential TMA single exposures, defined as the times for a TMA dose and a hold period. An interdependent relationship between dosing time and holding time on the hybrid material formation is observed for TMA exposure PET, exhibited as a linear trend between the mass gain and total exposure (dose time × hold time × number of sequential exposures). Deviation from this linear relationship is only observed under very long dose or hold times. In comparison, amount of hybrid material formed during sequential exposures to PA6 fibers is found to be highly dependent on amount of TMA dosed. Increasing the surface area of the fiber by altering its cross-sectional dimension is shown to have little on the reaction behavior but does allow for improved diffusion of the TMA into the fiber. This work allows for the projection of exposure parameters necessary for future high-throughput hybrid modifications to polymer materials.}, number={2}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Akyildiz, Halil I. and Jur, Jesse S.}, year={2015}, month={Mar} } @article{akyildiz_lo_dillon_roberts_everitt_jur_2014, title={Formation of novel photoluminescent hybrid materials by sequential vapor infiltration into polyethylene terephthalate fibers}, volume={29}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2014.333}, abstractNote={Abstract}, number={23}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Akyildiz, Halil I. and Lo, Michael and Dillon, Eoghan and Roberts, Adam T. and Everitt, Henry O. and Jur, Jesse S.}, year={2014}, month={Dec}, pages={2817–2826} } @article{akyildiz_michielsen_2013, title={Improving water solubility of poly(acrylic acid-co-styrene) copolymers by adding styrene sulfonic acid as a termonomer}, volume={129}, ISSN={["0021-8995"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000319275700064&KeyUID=WOS:000319275700064}, DOI={10.1002/app.38933}, abstractNote={AbstractAcrylic acid is often used to make water‐soluble polymers while styrene is often modified to add special functions to polymers. However, when styrene and acrylic acid are copolymerized, the resulting polymer is much less water soluble. To regain water solubility, the effect of styrene sulfonic acid on solubility of poly(acrylic acid‐co‐styrene) copolymers was investigated. Even though acrylic acid polymers are known for their water solubility, the presence of styrene units within acrylic acid copolymers reduces the solubility of the copolymer substantially at the natural pH of the solutions. By adding styrene sulfonic acid as a termonomer, polymers that are water soluble at the natural pH of the polymerization could be obtained. The solubility of the polymer after removal of the solvent and by redissolving at different concentrations and pH levels is also reported. Solubility increases at higher pH especially with low styrene concentration in the copolymer. It was found that incorporation of as little as 5 mol % of styrene into poly(acrylic acid) reduced the aqueous solubility to less than 0.5 g dL−1 at pH 7. Upon adding 7 mol % styrene sulfonic acid as a termonomer, the water solubility increased to 5 g dL−1 at pH 7. At higher levels of styrene, more styrene sulfonic acid was needed, especially at low pH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013}, number={4}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Akyildiz, Halil I. and Michielsen, Stephen}, year={2013}, month={Aug}, pages={2208–2215} } @article{sun_padbury_akyildiz_goertz_palmer_jur_2013, title={Influence of Subsurface Hybrid Material Growth on the Mechanical Properties of Atomic Layer Deposited Thin Films on Polymers}, volume={19}, ISSN={["1521-3862"]}, DOI={10.1002/cvde.201207042}, abstractNote={AbstractThe mechanical properties of atomic layer deposition (ALD) coatings play a key role in their long‐term use as encapsulation barriers for organic‐based, flexible, electronic devices. Nano‐indentation characteristics and flexure testing of nanometer‐scale alumina on polyamide 6 (PA6) films are investigated to determine the influence of a sub‐surface hybrid layer formed during the ALD process. This hybrid layer is observed to affect the mechanical performance of the thin films, in particular at lower processing temperatures. This work has important consequences on how ALD materials need to be applied and evaluated on polymers for application as encapsulation barrier layers.}, number={4-6}, journal={CHEMICAL VAPOR DEPOSITION}, author={Sun, Yujie and Padbury, Richard P. and Akyildiz, Halil I. and Goertz, Matthew P. and Palmer, Jeremy A. and Jur, Jesse S.}, year={2013}, month={Jun}, pages={134–141} } @article{akyildiz_padbury_parsons_jur_2012, title={Temperature and Exposure Dependence of Hybrid Organic-Inorganic Layer Formation by Sequential Vapor Infiltration into Polymer Fibers}, volume={28}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000310664300032&KeyUID=WOS:000310664300032}, DOI={10.1021/la302991c}, abstractNote={The characteristic processing behavior for growth of a conformal nanoscale hybrid organic-inorganic modification to polyamide 6 (PA6) by sequential vapor infiltration (SVI) is demonstrated. The SVI process is a materials growth technique by which exposure of organometallic vapors to a polymeric material promotes the formation of a hybrid organic-inorganic modification at the near surface region of the polymer. This work investigates the SVI exposure temperature and cycling times of sequential exposures of trimethylaluminum (TMA) on PA6 fiber mats. The result of TMA exposure is the preferential subsurface organic-inorganic growth by diffusion into the polymer and reaction with the carbonyl in PA6. Mass gain, infrared spectroscopy, and transmission electron microscopy analysis indicate enhanced materials growth and uniformity at lower processing temperatures. The inverse relationship between mass gain and exposure temperature is explained by the formation of a hybrid layer that prevents the diffusion of TMA into the polymer to react with the PA6 upon subsequent exposure cycles. As few as 10 SVI exposure cycles are observed to saturate the growth, yielding a modified thickness of ∼75 nm and mass increase of ∼14 wt %. Removal of the inherent PA6 moisture content reduces the mass gain by ∼4 wt % at low temperature exposures. The ability to understand the characteristic growth process is critical for the development of the hybrid materials fabrication and modification techniques.}, number={44}, journal={LANGMUIR}, author={Akyildiz, Halil I. and Padbury, Richard P. and Parsons, Gregory N. and Jur, Jesse S.}, year={2012}, month={Nov}, pages={15697–15704} }