Showing posts with label sol-gel. Show all posts
Showing posts with label sol-gel. Show all posts

Thursday, November 30, 2017

Abstract-Creation of 3D terahertz photonic crystals by the direct writing technique with a TiO2 sol-gel ink



Rong Wang, Weiyi Yang, Pengfei Zhu, Shuang Gao, Bo Li, Qi Li

http://onlinelibrary.wiley.com/doi/10.1111/jace.15347/abstract

Three-dimensional TiO2 woodpile terahertz photonic crystals with feature size less than 100 μm were created by the direct writing technique with a TiO2 sol-gel ink. With proper heat treatment, the rheological properties of the TiO2 sol-gel ink were modulated to meet the requirement to construct 3D-TPCs with feature size less than 100 μm by the direct writing technique. Well-crystallized rutile TiO2 3D-TPCs were obtained by the calcination process to provide the required high refractive indices, while the lattice periods of these TiO2 3D-TPCs could be changed to tune their terahertz properties. With the increase of the lattice period, a shift of their THz photonic band gap peaks towards the lower frequency was observed in both the simulated and experimental investigations.
This article is protected by copyright. All rights reserved.

Monday, May 15, 2017

OT-SBIR-STTR-Success: Luna Innovations



https://www.sbir.gov/node/1215983

A Virginia-based company is better positioned for long-term growth because of its work on a coating technology for the Department of Defense.
Luna Innovations has filed for patents for the general coating formulation and signed a licensing agreement with partner UltraTech International for production and marketing. Under the trade name Gentoo, the coating is providing royalties to Luna while being evaluated for wider global use by dozens of companies in various industries such as glass, automotive and biomedical.
Originally developed for pilots who faced a hazard with water pooling on aircraft canopies and windshields, the coating is designed to quickly shed water off transparent surfaces for improved visibility during inclement weather.
Through the Air Force Small Business Innovation Research/Small Business Technology Transfer (SBIR/STTR) Program, Luna has been part of an ongoing development program at Hill Air Force Base in Utah for F-16 canopy coatings and currently is going through qualification testing in collaboration with the canopy manufacturer.
Initial SBIR funding through the Navy was used to develop a formulation that combines fluid repellency and abrasion resistance. Follow-on funding through the Air Force SBIR/STTR Commercialization Readiness Program is allowing Luna’s team to optimize the formulation for improved adhesion during severe environmental conditions on jet aircraft, such as sand abrasion and impact damage from rain erosion at more than 500 knots.
An additional benefit that may emerge from this SBIR effort is a new process to estimate performance on a rain erosion test, according to Tim Lucas, a mechanical engineer for the 416th Supply Chain Management Squadron, which supports the F-16.
The ability to perform rain erosion testing – required to certify a coating like Luna’s – is limited by the availability of an expensive testing facility. Lucas said Luna is working toward a way that readily-available equipment could be used to provide an estimate, which would allow future coating developers to determine if they are heading in the right direction before going through the trouble of scheduling an official test at one of those facilities.
BEHIND THE TECHNOLOGY
There have been many academic and commercial efforts focused on the development of coatings – known as hydrophobic and superhydrophobic – that quickly shed water off surfaces. A large number of those have demonstrated the primary goal of achieving water shedding properties, but lacked durability or have been too difficult or too expensive to apply.
Luna’s chemists used their expertise in polymeric structures to modify a sol-gel (silica-based polymer) to incorporate very hydrophobic structures. This provides for the hydrophobic nature of the coating’s surface which causes water to bead and roll off.
Luna’s rain-repellent coating is a simple treatment solution that can be applied by the manufacturer to polycarbonate or acrylic-based canopies, polyurethane, metals and glass. This thin, hard coating is more than 99 percent transparent across the visible spectrum with less than 0.5 percent haze.
SBIR SUPPORT WAS CRITICAL
“Selling the product commercially provided (Luna with) additional funding to work in parallel to support the SBIR programs, thus providing the technology to the government economically and mitigating the risk that is inherent in a new product development,” said Bryan Koene, director of advanced materials for Luna. “We have also transitioned the coating to other government agencies by demonstrating improved corrosion resistance on metal substrates.”
Luna currently has five separate SBIR programs focused on the development of the base chemistry of this coating for different Department of Defense applications.

Wednesday, July 22, 2015

Abstract-Refractive indices and birefringence of hybrid liquid crystal - nanoparticles composite materials in the terahertz region




We show that a hybrid LC-ferroelectric nanoparticle suspension of liquid crystal E7 doped with BaTiO nanoparticles leads to 10% increase in birefringence in the THz region of spectrum as compared to pure E7. Doped liquid crystals can be used to increase performance of THz modulators and waveplates. BaTiO nanoparticles used in the mixture were synthesised with the sol gel technique, and their refractive index has been measured in THz in powder form and in solution.

Thursday, May 1, 2014

Abstract-Photoinduced active terahertz metamaterials with nanostructured vanadium dioxide film deposited by sol-gel method



Yaxin Zhang, Shen Qiao, Linlin Sun, Qi Wu Shi, Wanxia Huang, Ling Li, and Ziqiang Yang  »View Author Affiliations

Optics Express, Vol. 22, Issue 9, pp. 11070-11078 (2014)
http://dx.doi.org/10.1364/OE.22.011070

Applying the photoexcitation characteristics of vanadium dioxide (VO2), a dynamic resonant terahertz (THz) functional device with the combination of VO2 film and dual-resonance metamaterial was suggested to realize the ultrafast external spatial THz wave active manipulation. The designed metamaterial realizes a pass band at 0.28–0.36 THz between the dual-resonant frequencies, and the VO2 film is applied to control the transmittance of the spatial THz wave. More than an 80% modulation depth has been observed in the statics experiment, and the dynamic experimental results illustrate that this active metamaterial realizes up to a 1 MHz amplitude modulation signal loaded on a 0.34 THz carrier wave without any low noise amplified devices. The electromagnetic properties and photoinduced dynamic characteristics of this structure may have many potential applications in THz functional components, including modulators, intelligent switches, and sensors.
© 2014 Optical Society of America

Tuesday, September 4, 2012

Abstract-Synthesis and terahertz transmission properties of nano-porous vanadium dioxide films



Vanadium dioxide (VO2) films were prepared by the sol–gel method on high-purity silicon substrates, in which cetyltrimethyl ammonium bromide (CTAB) was used as a functional additive to form nano-porous structure in the VO2 films. The morphology, crystalline structure and stoichiometry of the films were investigated by field emission scanning electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. Furthermore, the effects of nano-scaled grain size and pores on the THz transmission properties across the phase transition in the VO2 films were studied. The results indicated that the film modified with CTAB can form a nano-porous VO2 structure with a uniform grain size of about 30 nm. The nano-porous VO2 film exhibited significantly broader hysteresis loops and a slight decrease in THz transmission reduction across the phase transition, compared with the common film without a nano-porous structure. A tentative interpretation is given for these phenomena.