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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Ultrasonic waves from radial mode excitation of a piezoelectric disc on the surface of an elastic solid

In this work, we discuss the ultrasonic wave propagation characteristics in an isotropic elastic solid due to the radial mode excitation of a piezoelectric disc actuator bonded to its surface. Finite element simulations using coupled electromechanical modeling is employed to investigate the wave propagation behavior. We find that the radial mode vibrations on the surface of the elastic solid generates all the three types of ultrasonic waves: longitudinal, shear, and surface waves. The waves in the solid are comprised of a central lobe and multiple side lobes based on the frequency of the radial mode excitation. The central lobe is predominantly composed of longitudinal waves and the side lobes are composed of shear waves. While the longitudinal waves have a strong central lobe and weak side lobes that are not fully developed, shear waves consists of fully developed side lobes. In addition, we observe that the longitudinal waves have fewer side lobes inside the solid compared to the shear waves. A semi-analytical approach is presented to explain the above observations. The interface traction boundary condition between the piezoelectric disc and the elastic solid is approximated as a truncated 'Bessel' excitation over the area of the piezoelectric disc in contact with the solid. A Fourier–Bessel series expansion technique is used to investigate the wave propagation behavior from the above traction boundary condition. The results obtained explain the observations from the finite element simulations with regard to the number and distribution of side lobes pertaining to the longitudinal and shear waves generated from the radial modes of the piezoelectric disc. The proposed semi-analytical approach is general and can be applied to any arbitrary axisymmetric excitations on the surface of an elastic solid.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Active control of laser beam pointing for the Zettawatt-Equivalent Ultrashort pulse laser System: a proof-of-principle study with 16-inch optics

We present a proof-of-principle study of active beam-pointing control for the Zettawatt-Equivalent Ultrashort pulse laser System (ZEUS) using a piezo-actuated 16-inch mirror. To the best of our knowledge, this is the largest actively controlled mirror reported in a high-power laser system. A simple proportional feedback control was implemented based on a field-programmable gate array, which reduced the standard deviation of beam-pointing fluctuations by 91% to 0.075 μrad in the horizontal direction and by 78% to 0.25 μrad in the vertical direction. We also demonstrated the elimination of long-term pointing jitter caused by temperature drift using the same apparatus.

laser pointing control↗
DOE OSTI2022

Reconfigurable quantum phononic circuits via piezo-acoustomechanical interactions

Abstract We show that piezoelectric strain actuation of acoustomechanical interactions can produce large phase velocity changes in an existing quantum phononic platform: aluminum nitride on suspended silicon. Using finite element analysis, we demonstrate a piezo-acoustomechanical phase shifter waveguide capable of producing ± π phase shifts for GHz frequency phonons in 10s of μm with 10s of volts applied. Then, using the phase shifter as a building block, we demonstrate several phononic integrated circuit elements useful for quantum information processing. In particular, we show how to construct programmable multi-mode interferometers for linear phononic processing and a dynamically reconfigurable phononic memory that can switch between an ultra-long-lifetime state and a state strongly coupled to its bus waveguide. From the master equation for the full open quantum system of the reconfigurable phononic memory, we show that it is possible to perform read and write operations with over 90% quantum state transfer fidelity for an exponentially decaying pulse.

Taylor, Jeffrey C. (ORCID:0000000215982436)↗
DOE OSTI2023

Crosslinked polymers with tunable coefficients of thermal expansion

Curatives and their resulting thermosets and other crosslinked polymers can reduce thermal expansion mismatch between an encapsulant and objects that are encapsulated. This can be accomplished by incorporating a negative CTE moiety into the thermoset resin or polymer backbone. The negative CTE moiety can be a thermal contractile unit that shrinks as a result of thermally induced conversion from a twist-boat to chair or cis/trans isomerization upon heating. Beyond CTE matching, other potential uses for these crosslinked polymers and thermosets include passive energy generation, energy absorption at high strain rates, mechanophores, actuators, and piezoelectric applications.

Redline, Erica Marie↗
DOE OSTI2024

Crosslinked polymers with tunable coefficients of thermal expansion

Curatives and their resulting thermosets and other crosslinked polymers can reduce thermal expansion mismatch between an encapsulant and objects that are encapsulated. This can be accomplished by incorporating a negative CTE moiety into the thermoset resin or polymer backbone. The negative CTE moiety can be a thermal contractile unit that shrinks as a result of thermally induced conversion from a twist-boat to chair or cis/trans isomerization upon heating. Beyond CTE matching, other potential uses for these crosslinked polymers and thermosets include passive energy generation, energy absorption at high strain rates, mechanophores, actuators, and piezoelectric applications.

Redline, Erica M.↗
DOE OSTI2023

Piezoelectric deformable photonic devices

A CMOS-compatible actuator platform for implementing phase, amplitude, and frequency modulation in silicon nitride photonic integrated circuits via piezo-optomechanical coupling using tightly mechanically coupled aluminum nitride actuators is disclosed. The platform, which may be fabricated in a CMOS foundry, enables scalable active photonic integrated circuits for visible wavelengths, and the piezoelectric actuation functions without performance degradation down to cryogenic operating temperatures. A number of devices are possible, including ring modulator devices, phase shifter devices, Mach-Zehnder interferometer devices, directional coupler devices (including tunable directional coupler devices), and acousto-optic modulator and frequency shifter devices, each of which can employ the same AlN actuator platform. As all of these devices can be built on the same AlN actuator platform, numerous optical functions can be implemented on a single die.

Eichenfield, Matt↗
DOE OSTI2020

AFM Microcantilever With a Collocated AlN Sensor-Actuator Pair: Enabling Efficient Q-Control for Dynamic Imaging

This manuscript presents a novel microcantilever with an embedded piezoelectric sensor-actuator pair for dynamic atomic force microscopy (AFM). The transducer pair is constructed from a two-layered AlN stack. Stacking the piezoelectric transducers in this manner leads to a minimal feedthrough from actuation to sense electrode, granting a high dynamic range frequency response for dynamic mode AFM. The cantilever's design allows for dual mode operation at 1 st and 2 nd resonance modes. High resolution tapping mode imaging results are reported, while the cantilever is operated at these modes. A feedback control loop is used to modify quality factor of the 1 st mode of the cantilever, using a positive position feedback (PPF) controller. Here, a faster response time is achieved by reducing the Q-factor, enabling the cantilever to track the topography at a higher scan rate. Results of bimodal AFM imaging are reported, using amplitude changes of the 1 st mode for surface topography, while material properties are encoded in phase changes of the 2 nd mode.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Controlling optical-cavity locking using reinforcement learning

Abstract This study applies an effective methodology based on Reinforcement Learning to a control system. Using the Pound–Drever–Hall locking scheme, we match the wavelength of a controlled laser to the length of a Fabry-Pérot cavity such that the cavity length is an exact integer multiple of the laser wavelength. Typically, long-term drift of the cavity length and laser wavelength exceeds the dynamic range of this control if only the laser’s piezoelectric transducer is actuated, so the same error signal also controls the temperature of the laser crystal. In this work, we instead implement this feedback control grounded on Q-Learning. Our system learns in real-time, eschewing reliance on historical data, and exhibits adaptability to system variations post-training. This adaptive quality ensures continuous updates to the learning agent. This innovative approach maintains lock for eight days on average.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method

A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials’ synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials’ placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Hybrid piezoelectric microresonator

A hybrid ferroelectric/non-ferroelectric piezoelectric microresonator is disclosed. The hybrid microresonator uses a ferroelectric layer as the actuator as ferroelectric materials typically have higher actuation coefficients than non-ferroelectric piezoelectric materials. The hybrid microresonator uses a non-ferroelectric piezoelectric layer as the sensor layer as non-ferroelectric piezoelectric materials typically have higher sensing coefficients than ferroelectric materials. This hybrid microresonator design allows the independent optimization of actuator and sensor materials. This hybrid microresonator design may be used for bulk acoustic wave contour mode resonators, bulk acoustic wave solidly mounted resonators, free-standing bulk acoustic resonators, and piezoelectric transformers.

Griffin, Benjamin↗
DOE OSTI2022

Spatiotemporally resolved measurements of electric field around a piezoelectric transformer using electric-field induced second harmonic (E-FISH) generation

When a piezoelectric transformer (PT) is actuated at its second harmonic frequency by a low input voltage, the generated electric field at the distal end can be sufficient to breakdown the surrounding gas, making them attractive power sources for non-equilibrium plasma generation. Understanding the potential and electric fields produced in the surrounding medium by the PT is important for effectively designing and using PT plasma devices. In this work, the spatiotemporally resolved characteristics of the electric field generated by a PT operating in open air have been investigated using the femtosecond electric field-induced second harmonic generation (E-FISH) method. Here, electric field components were determined by simultaneously conducting E-FISH measurements with the incident laser polarized in two orthogonal directions relative to the PT crystal. Results of this work demonstrate the spatial distribution of electric field around the PT’s output distal end and how it evolves as a function of time. Notably, the strongest electric field appears on the face of the PT’s distal surface, near the top and bottom edges and decreases by approximately 70% over 3 mm. The time delay between the PT’s input voltage and measured electric field indicates that there is an about 0.45 phase difference between the PT’s input voltage and output signal.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

CMOS-fabricated ultraviolet light modulator using low-loss alumina piezo-optomechanical photonics

Ultra-violet (UV) and near-UV wavelengths are necessary for many important optical transitions for quantum technologies and various sensing mechanisms for biological and chemical detection. However, all well-known photonic platforms have excessively high losses in the UV, which has prevented photonic integrated circuits (PICs) being used to address these and other important application spaces. Photonic waveguides using low-loss alumina cores and silicon dioxide cladding have emerged as a promising solution because of alumina’s large optical bandgap and the high quality of films enabled by atomic layer deposition. These properties allow passive, low-loss waveguide operation down to at least 266 nm using multimode widths. However, to the best of our knowledge, active alumina PICs have only been realized using thermo-optic tuning, which precludes switching speeds shorter than approximately 100 microseconds, high circuit densities, and cryogenically compatible operation. Here, we introduce a CMOS-fabricated, piezo-optomechanical PIC platform using alumina waveguides and piezoelectric aluminum nitride strain actuators. The platform allows for sub-microsecond switching times, high circuit densities, and cryogenic operation which is desired in many UV PIC applications. We demonstrate a high-performance, reconfigurable optical filter operating at wavelengths as low as 320 nm. The filter has a 6-nanosecond switching time, a loaded linewidth of 3.3 GHz, tuning rate of 28 V/linewidth, and a hold power of less than 20 nW at one linewidth detuning. This work establishes the foundations for a new class of CMOS-fabricated, rapidly reconfigurable, and low-power UV photonic circuits compatible with wavelengths as low as 225 nm.

Castillo, Zachary A. [Sandia National Laboratories↗
DOE OSTI2020

Coupling of electroelastic dynamics and direct contact ultrasonic drying formulation for annular piezoelectric bimorph transducers

A newly developed technique for drying clothes without thermal energy has been developed through the utilization of ultrasonic vibrations from piezoelectric transducers. The novel technique incorporates the actuation of a thin stainless steel disk in contact with wet fabric via annular piezoelectric rings, where water in the liquid form is atomized, transported through microchannels in the disk, and ejected as a mist. In such a system, resonance matching between the actuation portion of the transducer and the portion contacting fabric must be realized, with theoretical results from the developed electromechanical model showing a reduction in energy consumption by 50% when resonance matching is achieved. The electrically coupled distributed parameter model for an annular bimorph piezoelectric transducer is developed for optimization of ultrasonic drying technology. The thickness mode vibrations are shown to dominate the behavior of the system, where the analytically developed model can be optimized to increase the output acceleration of the transducer, thus increasing drying performance. Here, the electromechanical equation developed will be connected to the drying rates of fabrics in contact with said vibrations, where the novelty of the coupled equations and its description of the physics of ultrasonic drying will be discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unlocking Electrostrain in Plastically Deformed Barium Titanate

Achieving substantial electrostrain alongside a large effective piezoelectric strain coefficient (d 33 *) in piezoelectric materials remains a formidable challenge for advanced actuator applications. Here, in this work, a straightforward approach to enhance these properties by strategically designing the domain structure and controlling the domain switching through the introduction of arrays of ordered {100}<100> dislocations is proposed. This dislocation engineering yields an intrinsic lock-in steady–state electrostrain of 0.69% at a low field of 10 kV cm -1 without external stress and an output strain energy density of 5.24 J cm -3 in single-crystal BaTiO 3 , outperforming the benchmark piezoceramics and relaxor ferroelectric single-crystals. Additionally, applying a compression stress of 6 MPa fully unlocks electrostrains exceeding 1%, yielding a remarkable d 33 * value over 10 000 pm V -1 and achieving a record-high strain energy density of 11.67 J cm -3 . Optical and transmission electron microscopy, paired with laboratory and synchrotron X-ray diffraction, is employed to rationalize the observed electrostrain. Phase-field simulations further elucidate the impact of charged dislocations on domain nucleation and domain switching. These findings present an effective and sustainable strategy for developing high-performance, lead-free piezoelectric materials without the need for additional chemical elements, offering immense potential for actuator technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Giant piezoelectricity in oxide thin films with nanopillar structure

High-performance piezoelectric materials are critical components for electromechanical sensors and actuators. For more than 60 years, the main strategy for obtaining large piezoelectric response has been to construct multiphase boundaries, where nanoscale domains with local structural and polar heterogeneity are formed, by tuning complex chemical compositions. We used a different strategy to emulate such local heterogeneity by forming nanopillar regions in perovskite oxide thin films. We obtained a giant effective piezoelectric coefficient d 33 , f * of ~1098 picometers per volt with a high Curie temperature of ~450°C. Our lead-free composition of sodium-deficient sodium niobate contains only three elements (Na, Nb, and O). The formation of local heterogeneity with nanopillars in the perovskite structure could be the basis for a general approach to designing and optimizing various functional materials.

Science & Technology - Other Topics↗
DOE OSTI2020

Phase Switching as the Origin of Large Piezoelectric Response in Organic-Inorganic Perovskites: A First-Principles Study

Piezoelectrics are critical functional components of many practical applications such as sensors, ultrasonic transducers, actuators, medical imaging, telecommunications. So far, the best performing piezoelectrics are ferroelectric ceramics, many of which are toxic, heavy, hard, and cost-ineffective. Recently, a groundbreaking discovery of extraordinarily large piezoelectric coefficients in the family of organic-inorganic perovskites gave a hope for a cheaper, environmentally friendly, inexpensive, light-weight and flexible alternative. However, the origin of such response in organic-inorganic ferroelectrics whose spontaneous polarization is an order of magnitude smaller than for inorganic counterparts remains unclear. In this study we employ first-principles simulations to predict that the mechanism associated with large piezoelectric constants is of extrinsic origin and associated with switching between the stable phase and previously overlooked energetically competitive metastable phase that can be stabilized by the external stress. Here, the phase switching changes the polarization direction and, therefore, gives origin to large piezoelectric response, similar to PbZr$_{1-x}$Ti$_x$O$_3$ near morphotropic phase boundary. Existence of such metastable phases is likely to manifest as the dynamical molecular disorder above the Curie temperature and, therefore, could be intrinsic to the entire family of organic-inorganic ferroelectrics with such disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Fatigue-Crack Detection and Monitoring through the Scattered-Wave Two-Dimensional Cross-Correlation Imaging Method Using Piezoelectric Transducers

Piezoelectric transducers are convenient enablers for generating and receiving Lamb waves for damage detection. Fatigue cracks are one of the most common causes for the failure of metallic structures. Increasing emphasis on the integrity of critical structures creates an urgent need to monitor structures and to detect cracks at an early stage to prevent catastrophic failures. This paper presents a two-dimensional (2D) cross-correlation imaging technique that can not only detect a fatigue crack but can also precisely image the fatigue cracks in metallic structures. The imaging method was based on the cross-correlation algorithm that uses incident waves and the crack-scattered waves of all directions to generate the crack image. Fatigue testing for crack generation was then conducted in both an aluminum plate and a stainless-steel plate. Piezoelectric wafer transducer was used to actuate the interrogating Lamb wave. To obtain the scattered waves as well as the incident waves, a scanning laser Doppler vibrometer was adopted for acquiring time-space multidimensional wavefield, followed with frequency-wavenumber processing. The proof-of-concept study was conducted in an aluminum plate with a hairline fatigue crack. A frequency-wavenumber filtering method was used to obtain the incident wave and the scattered wave wavefields for the cross-correlation imaging. After this, the imaging method was applied to evaluate cracks on a stainless-steel plate generated during fatigue loading tests. The presented imaging method showed successful inspection and quantification results of the crack and its growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗