@article{garcia_kim_vinod_kim_fang_jiang_2023, title={A Bi-In-Sn eutectic multi-layer high temperature ultrasound transmitter with candle-soot nanoparticles for improved photoacoustic efficiency}, volume={12487}, ISBN={["978-1-5106-6081-6"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2658480}, abstractNote={There is a growing need for non-invasive structural health monitoring in extreme environments. For nuclear power plants, pressure and temperature sensing under hazardous environment plays an important role for coolant system safety and stability management. Current sensing methods are intrusive, and suffer from degradation in the plant environment, limited life cycle, and complicated repair and replacement procedures. In this paper, we present an advanced Bi-In-Sn liquid metal (LM) transducer with the addition of candle-soot nanoparticles (CSNP) for improved photoacoustic efficiency and a metallic stencil for control of the liquid metal layer thickness. The sensitivity of the liquid metal candle-soot nanoparticle (LM-CSNP) ultrasound transmitter was characterized under 2 mJ/cm2 at 65 °C, and 6 mJ/cm2 at 100 °C —300 °C. Compared with existing LM transmitter, the newly presented transmitter showed a sensitivity 6.6 times stronger than previously reported LM only transmitter.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, CIVIL INFRASTRUCTURE, AND TRANSPORTATION XVII}, author={Garcia, Nicholas and Kim, Ho-Wuk and Vinod, Kaushik and Kim, Taeyang and Fang, Tiegang and Jiang, Xiaoning}, year={2023} }
 @article{kim_kim_jiang_2021, title={Laser ultrasonic defect localization using an omni-arrayed candle soot nanoparticle patch}, volume={60}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac2012}, abstractNote={The generation of ultrasonic surface waves with lasers has become a useful noncontact NDT&E tool. This laser ultrasound technique provides a very flexible and simple method for noncontact and remote generation of ultrasonic surface waves, and has the advantage that various wave shapes can be easily produced by changing the shape of the beam that is illuminating the target. In this work, a laser ultrasound NDT&E method is proposed for defect localization by incorporating an omni-arrayed patterned candle soot nanoparticles-polydimethylsiloxane (CSNP-PDMS) patch. The omni-arrayed CSNP-PDMS patch generates a surface wave with a selective range of frequency, and an omni-directional signal with high amplitude, which surpasses the limitation of the line-arrayed patch. Further, the arrival time algorithm was adopted to validate the effectiveness of the omni-directional patch for 2D damage detection, which in turn the maximum magnitude of contour mapping from calculation agrees well with the true defect location.}, number={10}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Kim, Taeyang and Kim, Howuk and Jiang, Xiaoning}, year={2021}, month={Oct} }
 @misc{kim_kim_jiang_kim_2021, title={Static Force Measurement Using Piezoelectric Sensors}, volume={2021}, ISBN={1687-7268}, DOI={10.1155/2021/6664200}, abstractNote={In force measurement applications, a piezoelectric force sensor is one of the most popular sensors due to its advantages of low cost, linear response, and high sensitivity. Piezoelectric sensors effectively convert dynamic forces to electrical signals by the direct piezoelectric effect, but their use has been limited in measuring static forces due to the easily neutralized surface charge. To overcome this shortcoming, several static (either pure static or quasistatic) force sensing techniques using piezoelectric materials have been developed utilizing several unique parameters rather than just the surface charge produced by an applied force. The parameters for static force measurement include the resonance frequency, electrical impedance, decay time constant, and capacitance. In this review, we discuss the detailed mechanism of these piezoelectric-type, static force sensing methods that use more than the direct piezoelectric effect. We also highlight the challenges and potentials of each method for static force sensing applications.}, journal={JOURNAL OF SENSORS}, author={Kim, Kyungrim and Kim, Jinwook and Jiang, Xiaoning and Kim, Taeyang}, year={2021} }
 @article{kim_kim_kim_jiang_2020, title={A Face-Shear Mode Piezoelectric Array Sensor for Elasticity and Force Measurement}, volume={20}, ISSN={["1424-8220"]}, DOI={10.3390/s20030604}, abstractNote={We present the development of a 6 × 6 piezoelectric array sensor for measuring elasticity and force. The proposed sensor employs an impedance measurement technique, sensing the acoustic load impedance of a target by measuring the electrical impedance shift of face-shear mode PMN–PT (lead magnesium niobate–lead titanate) single crystal elements. Among various modes of PMN–PT single crystals, the face-shear mode was selected due to its especially high sensitivity to acoustic loads. To verify the elasticity sensing performance, gelatin samples with different elastic moduli were prepared and tested. For the force measurement test, different magnitudes of force were loaded to the sensing layer whose acoustic impedance was varied with applied forces. From the experimental results, the fabricated sensor showed an elastic stiffness sensitivity of 23.52 Ohm/MPa with a resolution of 4.25 kPa and contact force sensitivity of 19.27 Ohm/N with a resolution of 5.19 mN. In addition, the mapping experiment of elasticity and force using the sensor array was successfully demonstrated.}, number={3}, journal={SENSORS}, author={Kim, Kyungrim and Kim, Taeyang and Kim, Jinwook and Jiang, Xiaoning}, year={2020}, month={Feb} }
 @article{kim_kim_morrow_jiang_2020, title={Stress Measurement of a Pressurized Vessel Using Ultrasonic Subsurface Longitudinal Wave With 1-3 Composite Transducers}, volume={67}, ISSN={["1525-8955"]}, url={https://doi.org/10.1109/TUFFC.2019.2941133}, DOI={10.1109/TUFFC.2019.2941133}, abstractNote={This article aims to develop a stress-sensing method for a pressurized vessel based on subsurface longitudinal (SSL) waves confined in a specific waveform by using 1–3 composite transducers. Although ultrasonic SSL waves have been commonly utilized for stress sensing, wave excitation under the predefined function using the composite-type transmitter is not well studied. In this article, composite-type transducers having a wide frequency bandwidth (> 60%) and a predominant thickness mode are utilized to enhance the signal intensity of the SSL wave and the accuracy of the sensor by incorporating a specific toneburst waveform. Finite element analysis demonstrates that the signal intensity of the composite-type transducer is up to 45.3% higher than that of a single-phase transducer. Pulse-echo tests reveal that the frequency bandwidth of the developed transducer reaches up to 60.7% and is, therefore, sufficient (> 57.0%) to transmit and receive Hanning-windowed toneburst signals. Results of stress sensing affirm a linear relationship between the time delay of SSL wave and the mechanical stress of a pressurized vessel (0.335 ns/MPa). Accordingly, the regression model is constructed via principal component regression (PCR) under temperature-varying condition. PCR has a less significant degree of error (0.62 MPa) compared to that of a typical least square regression (9.49 MPa).}, number={1}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Kim, Taeyang and Morrow, Daniel and Jiang, Xiaoning}, year={2020}, month={Jan}, pages={158–166} }
 @article{kim_chang_kim_jiang_2019, title={Narrow band photoacoustic lamb wave generation for nondestructive testing using candle soot nanoparticle patches}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5100292}, abstractNote={The generation of ultrasonic surface waves with a photoacoustic-laser-source has become useful for the noncontact nondestructive testing and evaluation (NDT&E) of materials and structures. In this work, a hybrid ultrasound based NDT&E method is proposed based on the photoacoustic-laser-source as a noncontact Lamb wave generator by incorporating a line-arrayed patterned candle soot nanoparticle-polydimethylsiloxane (CSNPs-PDMS) patch as the signal amplifier and with a narrow bandwidth. The CSNP-PDMS composite has been investigated as the functional patch for its laser energy absorption efficiency, fast thermal diffusion, and large thermoelastic expansion capabilities. The signal amplitude (in mW) from the CSNP-PDMS patch exhibits 2.3 times higher amplitude than the no patch condition and a narrower bandwidth than other conditions. Furthermore, improvement in the sensitivity is also achieved through the selection of the aluminum nitride sensing system. The overall combination of the Lamb wave generation and receiver-sensing system in this study is found to be very promising for a broad range of noncontact NDT&E applications.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Taeyang and Chang, Wei-Yi and Kim, Howuk and Jiang, Xiaoning}, year={2019}, month={Sep} }
 @article{kim_chang_kim_huang_jiang_2019, title={Stress Measurement of a Pressurized Vessel Using Candle Soot Nanocomposite Based Photoacoustic Excitation}, volume={10971}, ISSN={["1996-756X"]}, DOI={10.1117/12.2515211}, abstractNote={This article aims to develop a pressure sensing method by utilizing both a contacting active sensor and a non-contacting laser ultrasound transmitter. An overloaded stress in an industrial pressure tank such as a nuclear reactor may cause a catastrophic explosion; thus, it is essential to monitor the mechanical stress in a reliable manner for the structural safety. Among many different types of stress sensing methods, ultrasound sensing has been attractive due to its non-invasive measurement feature. For the recent decades, subsurface longitudinal (SSL) ultrasonic wave has been widely used since it is not only less dependent on the internal medium and the surface condition, but also has the fastest wave speed without wave distortion. In our work, laser source and Aluminum nitride (AlN) wafer are used to generate and to receive SSL ultrasonic waves, respectively. In order to increase the photoacoustic efficacy, a composite of carbon-soot nanoparticles (CSNP) and polydimethylsiloxane (PDMS) was attached onto the intermediate wedge at the transmitter side. The photoacoustic experiment results demonstrate a reasonable linear relationship between the stress level and the time-of-flight variation of the propagated wave signal.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, CIVIL INFRASTRUCTURE, AND TRANSPORTATION XIII}, author={Kim, Ho-Wuk and Chang, Wei-Yi and Kim, Taeyang and Huang, Shujin and Jiang, Xiaoning}, year={2019} }
 @article{chang_chung_luo_kim_yamashita_jones_jiang_2018, title={Dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O-3-0.3 PbTiO3 single crystal poled using alternating current}, volume={6}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2018.1498812}, abstractNote={ABSTRACT In this paper, 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30%PT) single crystal samples were poled using an alternating current (electric field) poling (ACP) method. Compared to the traditional poling method, the piezoelectric coefficient, free and clamped dielectric constants were improved more than 21%. X-ray diffraction result suggests the existence of monoclinic phase (MA) in ACP samples and piezoresponse force microscopy (PFM) result further depicts the finer engineered domain structures. The ACP sample also showed the unique phase transition sequences during the depoling process. Our work could provide a novel domain engineered method to enhance piezoelectric properties of PMN-PT single crystal. GRAPHICAL ABSTRACT IMPACT STATEMENT Piezoelectric and dielectric properties of relaxor-PT single crystals can be significantly enhanced by employing the new alternating current poling method, attributing to the unique heterogenous domain structure containing unprecedented domain wall density.}, number={10}, journal={MATERIALS RESEARCH LETTERS}, author={Chang, Wei-Yi and Chung, Ching-Chang and Luo, Chengtao and Kim, Taeyang and Yamashita, Yohachi and Jones, Jacob L. and Jiang, Xiaoning}, year={2018}, pages={537–544} }
 @article{huang_kim_hou_cann_jones_jiang_2017, title={Flexoelectric characterization of BaTiO3-0.08Bi(Zn1/2Ti1/2)O-3}, volume={110}, number={22}, journal={Applied Physics Letters}, author={Huang, S. J. and Kim, T. and Hou, D. and Cann, D. and Jones, J. L. and Jiang, X. N.}, year={2017} }
 @article{kim_kim_jiang_2017, title={High temperature transducer using aluminum nitride single crystal for laser ultrasound detection}, volume={10169}, ISBN={["978-1-5106-0824-5"]}, ISSN={["0277-786X"]}, DOI={10.1117/12.2259975}, abstractNote={In this work, a new ultrasound nondestructive testing (NDT) method based on laser-generated Lamb wave detection was proposed for high temperature (HT) NDT. Lamb waves were introduced to a stainless steel plate by the Nd:YAG pulsed laser at one point and detected by aluminum nitride (AlN) transducer at a distant position. The fundamental symmetric (S0) and antisymmetric (A0) mode Lamb waves were successfully propagated in the thin stainless steel plate. The time-of- flight (TOF) of the S0 and A0 mode waves proportionally increased with the distance (D) between the laser source and the sensor, and almost no attenuation of the amplitude was observed. For the HT NDT experiment, AlN single crystal was adopted as the ultrasonic sensor material due to its high thermal resistance of the dielectric and piezoelectric constants at the elevated temperature up to 800 °C. The combination of non-contact, portable laser source as a Lamb wave generator and temperature-robust NDT sensor made of AIN has shown its great capability to detect the Lamb waves at elevated temperatures.}, journal={NONDESTRUCTIVE CHARACTERIZATION AND MONITORING OF ADVANCED MATERIALS, AEROSPACE, AND CIVIL INFRASTRUCTURE 2017}, author={Kim, Taeyang and Kim, Jinwook and Jiang, Xiaoning}, year={2017} }
 @article{kim_saini_kim_gopalarathnam_zhu_palmieri_wohl_jiang_2017, title={Piezoelectric Floating Element Shear Stress Sensor for the Wind Tunnel Flow Measurement}, volume={64}, ISSN={["1557-9948"]}, DOI={10.1109/tie.2016.2630670}, abstractNote={A piezoelectric (PE) sensor with a floating element was developed for direct measurement of flow induced shear stress. The PE sensor was designed to detect the pure shear stress while suppressing the effect of normal stress generated from the vortex lift up by applying opposite poling vectors to the PE elements. During the calibration stage, the prototyped sensor showed a high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high PE coefficients (<inline-formula><tex-math notation="LaTeX">$d_{{31}}=- $</tex-math></inline-formula>1330 pC/N) of the constituent 0.67Pb(Mg<inline-formula><tex-math notation="LaTeX">$_{1/3} $</tex-math></inline-formula>Nb<inline-formula> <tex-math notation="LaTeX">$_{2/3} $</tex-math></inline-formula>)O<sub>3</sub>–0.33PbTiO<sub>3</sub> (PMN–33%PT) single crystal. By contrast, the sensor showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the sensing structure. The usable frequency range of the sensor is up to 800 Hz. In subsonic wind tunnel tests, an analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements. For dynamic stress measurements, the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing. The developed PE shear stress sensor was found to have an SNR of 15.8 ± 2.2 dB and a sensitivity of 56.5 ± 4.6 pC/Pa in the turbulent flow.}, number={9}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, author={Kim, Taeyang and Saini, Aditya and Kim, Jinwook and Gopalarathnam, Ashok and Zhu, Yong and Palmieri, Frank L. and Wohl, Christopher J. and Jiang, Xiaoning}, year={2017}, month={Sep}, pages={7304–7312} }
 @article{kim_kim_jiang_2017, title={Transit Time Difference Flowmeter for Intravenous Flow Rate Measurement Using 1-3 Piezoelectric Composite Transducers}, volume={17}, ISSN={["1558-1748"]}, DOI={10.1109/jsen.2017.2727340}, abstractNote={The flow rate of injected medication implemented by intravenous (IV) systems must be accurately monitored and meticulously controlled to prevent medical accidents. In this paper, an ultrasonic flowmeter (UF) with 1–3 piezoelectric composite transducers was designed, fabricated, and tested on a variety of flow rates of mimic medical injections. The transducer wedge for the angled beam propagation and an acoustic impedance matching layer were included in the design for transmission enhancement. To ensure an accurate measurement of flow rate, the effect of the flow distributions inside the IV tube was taken into account. The developed UF exhibited the capability of detecting low flow rates (<0.005 m/s), with 1%–2% discrepancy compared with the reference rate of infusion.}, number={17}, journal={IEEE SENSORS JOURNAL}, author={Kim, Taeyang and Kim, Jinwook and Jiang, Xiaoning}, year={2017}, month={Sep}, pages={5741–5748} }
 @article{kim_saini_kim_gopalarathnam_zhu_palmieri_wohl_jiang_2016, title={A piezoelectric shear stress sensor}, volume={9803}, ISSN={["1996-756X"]}, DOI={10.1117/12.2219185}, abstractNote={In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress, suppressing effects of normal stress components, by applying opposite poling vectors to the piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces where it demonstrated high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high piezoelectric coefficients of 0.67Pb(Mg1∕3Nb2∕3)O3-0.33PbTiO3 (PMN-33%PT, d31=-1330 pC/N). The sensor also exhibited negligible sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is up to 800 Hz.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2016}, author={Kim, Taeyang and Saini, Aditya and Kim, Jinwook and Gopalarathnam, Ashok and Zhu, Yong and Palmieri, Frank L. and Wohl, Christopher J. and Jiang, Xiaoning}, year={2016} }
 @article{kim_huang_huang_jiang_2016, title={Thermal gradient induced flexoelectric effects in bulk Ba0.67Sr0.33TiO3}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4949358}, abstractNote={Flexoelectric effect, denoting electric field gradient induced mechanical strain or mechanical strain gradient induced electric polarization, is a universal phenomenon in all dielectrics. Although research on the topic of flexoelectricity under stress fields and electric fields has advanced significantly, information regarding the phenomenon under thermal fields is rather limited. In this letter, the flexoelectricity field of Ba0.67Sr0.33TiO3 (BST) was investigated by generating temperature gradients along the lengths of samples with symmetric geometry. An electric field gradient induced by a thermal gradient was analyzed based on the temperature-dependent dielectric property of BST. The strain was then experimentally verified due to the electric field gradient. Experimental results suggest converse flexoelectric effect of BST samples with symmetric geometry in a thermal field. This result was not only consistent with the theoretical prediction, but it also followed the scaling effect of flexoelectricity.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Taeyang and Huang, Wenbin and Huang, Shujin and Jiang, Xiaoning}, year={2016}, month={May} }
 @article{kim_kim_dalmau_schlesser_preble_jiang_2015, title={High-Temperature Electromechanical Characterization of AlN Single Crystals}, volume={62}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2015.007252}, abstractNote={Hexagonal AlN is a non-ferroelectric material and does not have any phase transition up to its melting point (>2000°C), which indicates the potential use of AlN for high-temperature sensing. In this work, the elastic, dielectric, and piezoelectric constants of AlN single crystals were investigated at elevated temperatures up to 1000°C by the resonance method. We used resonators of five different modes to obtain a complete set of material constants of AlN single crystals. The electrical resistivity of AlN at elevated temperature (1000°C) was found to be greater than 5 × 1010 Ω · cm. The resonance cm. frequency of the resonators, which was mainly determined by the elastic compliances, decreased linearly with increasing temperature, and was characterized by a relatively low temperature coefficient of frequency, in the range of -20 to -36 ppm/°C. For all the investigated resonator modes, the elastic constants and the electromechanical coupling factors exhibited excellent temperature stability, with small variations over the full temperature range, <;11.2% and <;17%, respectively. Of particular significance is that due to the pyroelectricity of AlN, both the dielectric and the piezoelectric constants had high thermal resistivity even at extreme high temperature (1000°C). Therefore, high electrical resistivity, temperature independence of electromechanical properties, as well as high thermal resistivity of the elastic, dielectric, and piezoelectric properties, suggest that AlN single crystals are a promising candidate for high-temperature piezoelectric sensing applications.}, number={10}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Kim, Taeyang and Kim, Jinwook and Dalmau, Rafael and Schlesser, Raoul and Preble, Edward and Jiang, Xiaoning}, year={2015}, month={Oct}, pages={1880–1887} }