What is believed to be a new phenomenon - plasma-based thermally-induced optical reflection of sound (P-THORS) - overcomes the limitations of traditional THORS (e.g. need for line-of-sight, concentration dependence, and variations in efficiency at distance) by using a laser to generate a shaped plasma for the formation of highly-efficient, variable geometry, free-space acoustic reflector/barrier. These reflectors allow for the focusing and steering of acoustic waves without the need of a continuous barrier or engineered materials. This work demonstrates for the first time the generation of P-THORS barriers with highly efficient reflection efficiencies, exceeding those of traditional THORS barrier (i.e. > 70%) as well as the ability to transiently shape the barrier into various geometries to steer the acoustic wave to specific locations. P-THORS barriers are shown to reflect near 100% of incident ultrasonic signals and maintain that reflectivity for 5 ms post-plasma formation. Furthermore, by shaping the plasma it was possible to selectively direct the ultrasonic and/or acoustic waves to a desired location with efficiencies of 30% or greater, depending on the geometry of the shaped plasma.

Hydroxyapatites are important and major component of the body and play a vital role in the development of bones and teeth. Although bone regeneration involves various complex biological processes, calcium silicates and phosphates have been proven as important components for bone regenerative properties. The aim of the present study is to study the effect of manganese and gallium doping on the electrical properties in the silicate and phosphate bone materials which can affect the regenerative properties. Source materials were compacted in the form of pellets and processed at 600 °C for sintering and grain growth with and without selenium flux. Processing at 600 °C produced metastable grains transitioning from crystalline to glassy phase and hence and hence easier to merge in existing grains in presence of selenium. Silica rich material showed crystalline bones, and phosphorous rich phases facilitated the glassy behavior. Thermogravimetric analysis (TGA) showed stability up to 350 °C and continuous decomposition at high temperature. We observed that dielectric constant and resistivity for the frequency range of 100 Hz to 100,000 Hz at bias voltage 50 mV to 1000mV did not change, which indicates that breakdown of the ceramic material did not occur despite lower resistivity.

This paper explores the development of innovative materials for the dielectric energy storage for space components. The CaCu3Ti4O12 or CCTO belonging to perovskite family is of interest due to its colossal dielectric constant. It was demonstrated that materials synthesized at low temperature show nonequilibrium state and exhibit differences in the dielectric and resistivity values. The goal is to obtain high dielectric constant along with high resistivity values for achieving enhanced breakdown voltage. By using other members of the perovskite structures, it was demonstrated that similar colossal dielectric constant is observed and is dependent on processing methods. We have used heterovalent and dissimilar sized atom to replace Ca+2 ion. Accordingly, we replaced Ca+2 ion with heavy Ga+3 ion and developed gallium-based material system, Ga2/3 Cu3Ti4O12. Following successful synthesis, we measured its dielectric constant and resistivity and compared with CCTO material system. Results of five sets of samples showed that lower temperature processing demonstrated mechanism of grain growth, but due to copper flow in high temperature processed samples dielectric constant and resistivity values were different.

Significance: The glassy and crystalline hydroxyapatites that affect the metabolic processes such as tissue growth and healing are affected by the electrical, electrochemical, and optical properties investigated in this study. Aim: The aim of the present study is to determine effects of high-energy radiation and impurities on the electrical and optical properties of hydroxyapatites responsible for tissue growth and tendency of glass forming ability. Approach: The approach of the study involves synthesis using carbonates, oxides, silicates, phosphates, and borates of parent materials using elevated temperature and low-temperature flux process. High-energy radiation effects were studied by exposing hydroxyapatites with 5 mu Ci Cs-137 gamma-ray source. Morphology was studied to determine dissolution and glass formation of additives such as titanium, gallium, and selenium. Results: Irradiation of silicate bio glasses showed huge effects on the electrical characteristics, such as dielectric constant (hence polarity) and resistivity of the materials while optical properties showed insignificant changes. Morphological studies showed transition of faceted to nonfaceted structure. Conclusion: Exposure for the bias voltage of 50 to 1000 mV in the range of 100 to 100000 Hz frequency range showed a large decrease in the dielectric constant and increase in resistivity. The IR and Raman spectra for irradiated glasses exposed for 24 h showed a small change. Morphological results showed that substitution of gallium, magnesium, and /or titanium affects the transition to the glass formation. The addition of selenium showed enormous potential to improve the mixing and glass formation without titanium and gallium precipitates in the matrix. (c) 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)

Hydroxyapatites have been investigated since past six decades as laser host materials. Because of their important roles in bone and teeth, these have been subjects of recent investigations. Gallium and titanium have great potential for decreasing the depletion of calcium and reducing osteoporosis. The electrical properties and polarity play important roles in regeneration of the bones. We observed growth of grains in selenium-doped gallium and titanium containing silicate hydroxyapatites. Observed morphology showed non-facetted microstructures and it helped in achieving larger grains. For the material processed for the period of longer than 70 h, we did not observe any difference in the dielectric constant and resistivity of the selenium-doped materials. For irradiating the materials, a Cs-137 gamma-radiation with 5 mu m curie dose was used up to 100 h. We observed that the dielectric constant and resistivity at different frequencies ranging from 100 to 100 000 Hz were affected by the high energy radiation. However, bias voltage in the range of 50-1 000 mV did no alter the dielectric constant or resistivity. This indicated that the breakdown of the material did not occur for this bias range.

Binary and ternary selenide crystals have been proven as multifunctional for optical sensors and laser applications. The aim of this study was to evaluate reactive flux growth process of the doped zinc selenide crystals and compared with bulk physical vapor transport (PVT) grown large single crystals. The experimental process of synthesis involved PVP (Polyvinyl Pyrrolidone) flux dissolved in DI water which was heated at 65 degrees C, stirred until all PVP dissolved. We added Se powder dissolved in ethanol and heated again for few minutes. We added ZnCl2 solution in ethanol/Se mixture and heated at well below 100 degrees C. Water and ethanol solvent was separated and placed at 200C. The residue material was doped with transition metal. This material was characterized for the luminescence and compared with the results of bulk crystals grown by PVD process.

Considerable efforts have been devoted since the past three decades for the development of low cost ferroelectric and clean energy storage multifunctional materials. Modification in design and production of a low cost material with well proven process provides pathway for high energy density dielectric energy storage. We studied fluorine doped a commercially well-established material system barium strontium titanate with two different concentrations of dopants and studied the morphological transition and its effect on properties. It was observed that sample with higher concentration transitioned much faster into glassy state, followed by growth of fibers which turned into a self-arranged bird nest type shape. The sample with lower concentration changed slowly into glassy state and only few fibers were farmed. Dielectric was highly dependent on processing methods and shows variation with crystallinity of material, temperature, and cooling conditions during processing. In the higher concentration range, we observed nano-scale interface breakdown very similar to that of solid-liquid interface breakdown during crystal growth.

We have synthesized calcium oxide and calcium oxalate based kidney stones and investigated remelting to understand the process of dissolution. The dissolution morphology and remelting process in water was observed for the pure and intensely impurity doped oxalateurate stones grown at lower pH to study effect of acidity, and pH near actual pH of the stomach. Direct observation showed different melting morphologies. We observed needles, plates, dendrites, and lamella depending on the pH level and impurities. Remelting studies indicated that during breaking of large polycrystalline bunched stones grown at lower pH break into faceted small crystals which dissolve into the solvent depending on the acidity pH and impurities. High purity stones grown near stomach pH (6.4-7.5) tends to grow in needles morphology which dissolve slowly and fragment into smaller needles. A comparison was made with real kidney stones observed at Herring laboratory and similarity was observed with impurity doped stones. There was significant difference in decomposition of pure and impurity doped stones. Thermal analysis (DTA) showed that sugar doped oxides decompose continuously.

In this work, we describe the phenomenon, Thermally-induced Optical Reflection of Sound (THORS), and how it can be used to optically steer acoustic waves around a 90 degree corner of a physical obstruction, where observed acoustic amplitudes are increased by a factor of 30. In addition, we discuss the introduction of ultrasonic waves to the THORS phenomenon, and preliminary results for THORS barriers generated in ambient air, using a 5.3-5.7 μm CO laser source.The manipulation and guiding of sound waves have typically required the use of physical barriers for the reflection of an incident pressure wave. With the manipulation of acoustic waves being critical for many applications in scientific and engineering fields, including subsurface tissue imaging, photoacoustic sensing, secure communications, acoustic stealth technology, and acoustic design engineering; the requirement for physical barriers often represents a significant limitation. The recently discovered phenomenon THermally-induced Optical Reflection of Sound (THORS), provides the ability to generate acoustically reflective barriers, in air, by exciting media in the path of an IR laser beam, causing abrupt changes in compressibility between the excited and surrounding media. In this work, we demonstrate the ability to efficiently reflect sound waves around physical obstructions using a laser. Additionally, this work demonstrates the ability to also manipulate ultrasonic waves via THORS barriers, where the reflection and suppression of ultrasonic pulses in the frequency range of 120-300 kHz are shown. Finally, preliminary results demonstrating the ability to employ THORS in ambient air using water vapor as the absorbing media and a 5.5 μm CO laser beam for excitation.

Using the recently discovered THermally-induced Optical Reflection of Sound (THORS) phenomenon, it is possible to generate optically induced, local density barriers in air by the absorption of intense, modulated laser light (the THORS phenomenon), which results in abrupt differences in compressibility of the air at these barriers that can efficiently reflect incident acoustic waves. In this note, we demonstrate the ability to optically manipulate and reflect acoustic waves in air as well as optimize the functional parameters (optical modulation and acoustic frequency) and characterize the effects of common physical parameters, including localized thermal gradients and incident angle of reflection on the efficiency of the resulting acoustic reflection. Finally, the ability to efficiently steer acoustic waves around a physical obstruction using THORS is also demonstrated.

Superhydrophobic polymer films are a material of interest for aircraft deicing fluids to achieve the selfcleaning lotus effect. Hydrophobic polymer films were obtained by a solvent selective method composed of hydrophilic polymethylmethacrylate (PMMA) and hydrophobic polystyrene (PS) and hydrophilic titania nanoparticles. The addition of titania nanoparticles changed the surface of the thin films from an anisotropic morphology to a spherical isotropic surface due to hydrophobic and hydrophilic repulsion. Irradiation of UV responsive titania nanoparticles retained the same surface morphology. Water contact angle measurements will be completed to determine the hydrophobic nature of the polymer films.

An experimental study on the absorption, emission, crystal quality, and morphological characteristics of the transition metal doped zinc selenide (ZnSe) crystals is performed. This study focuses on the effect of dopant and thermal convection on crystal characteristics. Two ZnSe crystals, one doped with Fe2+ and the other with Cr2+, are grown using the physical vapor transport method. The bulk crystal samples are further divided into localized zones and overall crystallinity is evaluated using optical transparency, scanning electron microscopy, and X-ray diffraction analyses. Gross defects, such as large precipitates, inclusions and voids, are not observed. The radial segregation and its effect on morphology and optical fluorescence and emission are studied for both doped crystals using different spots along the radius for both crystals. The absorption and emission properties are investigated and the results are discussed in terms of the energy levels from which the optical transitions occur.

The ability to precisely control and manipulate acoustic waves can be highly limiting in applications and environments where placement of physical barriers for acoustic steering cannot be employed (e.g. tissues, air, etc.) In this work, we describe the ability to generate acoustic waveguides via thermally-induced optical reflection of sound (THORS) for the manipulation of acoustic waves in free space (i.e., air). Abrupt, density barriers are formed by photothermally depleting the sample in a laser beam’s path via photothermal processes, resulting in sharp differences in compressibility and significant acoustic reflection (greater than 30%). Optical waveguiding of sound can be achieved by generating THORS channels with a cylindrical (ring shaped) laser beam. By containing the acoustic waves inside a THORS cylindrical channel, a dramatically reduced acoustic decay profile of 1/r0.6 with distance is achieved. Additionally, we describe the effects that optical modulation frequency of the THORS channel has on the efficiency of acoustic waveguiding. We also show how external acoustic waves, incident to a THORS channel are suppressed, increasing the signal-to-background ratio of the internally waveguided acoustic signals. Optical waveguiding of acoustic waves offers a new paradigm in the manipulation of sound over extended distances, providing potentially significant improvements to photoacoustic sensing, secure communications, and many other applications.

Recent studies on multinary oxides for applications as laser hosts and high dielectric capacitors have shown that processing at high temperature provides glassy or crystalline materials based on thermal treatments and cooling rates. Since hydroxyapatites are now subject of great interests due to their bioactivity, interest in producing soft and hard materials with glassy and crystalline nature by processing parameters has become very important. Crystalline materials by using Bridgman, Czochralski and flux growth methods are costly and require huge investment. We have observed that even low temperature solidification in organic flux produced oriented fibers. This organic treated material has different characteristics than in situ oxide materials prepared by sintering and grain growth. Examples of phosphate and silicate-based systems will be presented to demonstrate soft and hard materials. Effect of TiO2 and other hardening elements will be also reported.