► Impact of micro-jets mechanically breaks the oxide film on the Ti–6Al–4V surface at numerous tiny locations. ► Solid Ti–6Al–4V is excessively dissolved into liquid Al–Si under the effects of hot ...spots and ultrasonic stir. ► Different intermetallic compounds (TiAl3 and Ti7Al5Si12) form at different positions of pits. ► Accelerated effect of acoustic streaming on elements diffusion in liquid makes the TiAl3 transform to Ti7Al5Si12.
Power ultrasonic vibration (20kHz, 6μm) was applied to assist the interaction between a liquid Al–Si alloy and solid Ti–6Al–4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti–6Al–4V surface, chemical dissolution of solid Ti–6Al–4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2–20μm diameter-sized pits formed on the Ti–6Al–4V surface. Propagation of ultrasonic waves in the liquid Al–Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti–6Al–4V substrate, excessive chemical dissolution of solid Ti–6Al–4V into liquid Al–Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al–Si and Ti–6Al–4V can be produced by ultrasonic-assisted brazing in air.
•Ultrasonic shot peening produces surface nanostructure in short duration.•Surface nanostructure promotes viability of human mesenchymal stem cells.•Surface nanostructure enhances corrosion ...resistance in SBF.
Surface mechanical attrition treatment (SMAT) of metallic biomaterials has gained significant importance due to its ability to develop nano structure in the surface region. In the present study, the microstructural changes and corrosion behavior of the commercially pure titanium (cp-Ti), following different durations of ultrasonic shot peening (USSP) has been investigated. cp-Ti was shot peened for different durations from 0 to 120 s and the treated samples were examined for microstructural changes in the surface region, cell viability and corrosion behavior. Cell viability was considerably increased after USSP for 60–120 s, exhibiting maximum for the 90 s of USSP. The passivation tendency was also improved with peening duration up to 90 s, however, it declined for longer duration of USSP. The beneficial effects of USSP may be attributed to nano structuring in the surface region and development of higher positive potentials at the USSP treated surface. Transmission Electron Microscope (TEM) examination of the USSPed surface revealed dislocation entanglement and substructure. Also, higher surface volta potential was observed over the USSPed sample exhibiting better cell proliferation. The present work is corollary to previous work of the group and mainly discusses the role of USSP duration, as a process parameter, on the cell viability and corrosion resistance of cp-Ti.
•Decoupling of the ultrasonic velocity and the thermal expansion contributions to the mean scatterer spacing of the medium.•A quadratic model of thermal expansion was proposed and it better fits the ...mean scatterer spacing than the linear model in the temperature range where the ultrasonic speed exhibits a linear behavior.•The quadratic model applied in ultrasonic thermometry exhibits higher precision than the linear model.
Previous works have shown the feasibility of temperature estimation during ultrasonic therapy using pulse-echo diagnostic ultrasound. These methods are based on the measurement of thermally induced changes in backscattered RF echoes due to thermal expansion and changes in ultrasonic velocity. They assume a joint contribution of these two parameters and a linear dependence with temperature. In this work, the contributions of velocity changes and thermal expansion to the evolution of the mean scatterer spacing of ex vivo bovine skeletal muscle tissue samples were decoupled. This was achieved by employing an experimental setup which allows measuring the absolute velocity value, using the through-transmission technique in a direct transmission configuration. The mean-scatterer spacing was estimated from spectral analysis of the backscattered signals obtained in pulse-echo mode. We propose a quadratic model of the thermal expansion coefficient to fit the evolution of the mean-scatterer spacing with temperature. The temperature increase estimated by the linear model, in the range of 29.5–47 °C, presents a percentage error (mean square error) of 11 %, while for the quadratic model the error is 4.8 %.
In this report, we have attempted to experimentally and theoretically reveal a new piezo-photocatalyst Bi
O
CO
for efficient removal of ciprofloxacin (CIP) from water. Bi
O
CO
nanoplates were ...synthesized to evaluate their photocatalytic (irradiation source: simulated-sunlight), piezocatalytic (irradiation source: ultrasonic) and piezo-photocatalytic (irradiation source: simulated-sunlight and ultrasonic) performances for CIP elimination. Under the condition C
= 10 mg/L and C
= 1 g/L, the piezo-photodegradation rate constant is obtained as k
= 0.07811 min
, which surpasses that of photocatalysis (k
= 0.04686 min
) and piezocatalysis (k
= 0.01233 min
); this phenomenon manifests an obvious piezo-enhanced photocatalytic behavior in terms of the "1 + 1 > 2" principle. The ultrasonic-induced piezoelectric behavior in Bi
O
CO
nanoplates and involved piezo-photocatalytic mechanism were theoretically elucidated by density functional theory (DFT) and finite-element method (FEM) studies. Additionally, the effects of various factors on the CIP degradation, decomposition mechanism of CIP and toxicity of the decomposition intermediates were also analyzed.
Purpose:
Knee joint is one of the largest and most complex joints of the body. Knee joint diseases are common, and current clinical imaging technologies such as x-ray computed tomography, magnetic ...resonance imaging, and ultrasound imaging have limitations in the diagnosis of knee joint diseases. Emerging imaging technologies such as diffuse optical tomography and photoacoustic imaging (PAI) have been applied to the detection of osteoarthritis (OA). However, they are limited to small joints such as the finger and difficult to be used for large joints such as the knee. Thermoacoustic imaging (TAI), also an emerging modality, provides high contrast and deep tissue penetration. Here, the authors apply TAI to the knee joint and demonstrate the potential of TAI for imaging large joints.
Methods:
Adult New Zealand male rabbits (average weight = 2 kg) were chosen for this study. In a TAI experiment, a rabbit was placed in a holder to keep in a genuflex position after being injected with pentobarbital through its ear margin intravenous (30 mg/kg). The holder and the rabbit were then positioned under the horn antenna of the TAI system for signal acquisition and image reconstruction. After the experiment, the imaged knee joint was dissected and photographed. Identical procedures were performed for several rabbits (n = 4). Finally, detailed comparative analyses between TAI images and anatomical pictures of the knee joint were conducted.
Results:
There were high similarities between the reconstructed TAI images and anatomical pictures of the knee joint, in terms of the shape and size of various knee joint tissues. TAI could clearly image ligament, fat pad, and other joint tissues. The differences in appearance of TAI images due to motion effect of the knee joint were also discussed.
Conclusions:
TAI could reveal details of rabbit knee joint in high resolution. As the recovered TAI images represent the dielectric property distributions of joint tissues, TAI may offer a new tool for noninvasive detection of joint diseases such as OA.
•As the first of its kind, a nanocomposite-inspired in-situ broadband ultrasonic sensor.•Responsive to broadband acousto-ultrasonic waves, from static to 400kHz.•Validated effective for ...acousto-ultrasonics-based damage identification and structural health monitoring.•Demonstrated applications to impact localization and quantitative damage evaluation.•Proven comparable with commercial strain gauges and PZT transducers, but with a higher gauge factor and greater flexibility.•Lightweight and small, coatable to structural surfaces and networkable to render rich information.
A novel nanocomposite-inspired in-situ broadband ultrasonic sensor previously developed, with carbon black as the nanofiller and polyvinylidene fluoride as the matrix, was networked for acousto-ultrasonic wave-based passive and active structural health monitoring (SHM). Being lightweight and small, this kind of sensor was proven to be capable of perceiving strain perturbation in virtue of the tunneling effect in the formed nanofiller conductive network when acousto-ultrasonic waves traverse the sensor. Proof-of-concept validation was implemented, to examine the sensor performance in responding to acousto-ultrasonic waves in a broad frequency regime: from acoustic emission (AE) of lower frequencies to guided ultrasonic waves (GUWs) of higher frequencies. Results have demonstrated the high fidelity, ultrafast response and high sensitivity of the sensor to acousto-ultrasonic waves up to 400kHz yet with an ultra-low magnitude (of the order of micro-strain). The sensor is proven to possess sensitivity and accuracy comparable with commercial piezoelectric ultrasonic transducers, whereas with greater flexibility in accommodating curved structural surfaces. Application paradigms of using the sensor for damage evaluation have spotlighted the capability of the sensor in compromising “sensing cost” with “sensing effectiveness” for passive AE- or active GUW-based SHM.
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•Sonocatalysis is an effective option for the remediation of metribuzin.•ZnFe LDH was doped with lanthanum to improve its sonocatalytic properties.•Ultrasound/La-doped ZnFe ...LDH/Peroxydisulfate has a high synergistic effect.•SO4•− radicals played a major role in the sonocatalytic degradation of metribuzin.
Metribuzin is an herbicide that easily contaminates ground and surface water. Herein, La-doped ZnFe layered double hydroxide (LDH) was synthesized for the first time and used for the degradation of metribuzin via ultrasonic (US) assisted peroxydisulfate (PDS) activation. The synthesized LDH had a lamellar structure, an average thickness of 26 nm, and showed mesoporous characteristics, including specific surface area 110.93 m2 g−1, pore volume 0.27 cm3 g−1, and pore diameter 9.67 nm. The degradation efficiency of the US/La-doped ZnFe LDH/PDS process (79.1 %) was much greater than those of the sole processes, and the synergy factor was calculated as 3.73. The impact of the reactive species on the sonocatalytic process was evaluated using different scavengers. After four consecutive cycles, 10.8 % loss occurred in the sonocatalytic activity of the La-doped LDH. Moreover, the efficiency of the US/La-doped LDH/PDS process was studied with respect to the degradation of metribuzin in a wastewater matrix. According to GC–MS analysis, six by-products were detected during the degradation of metribuzin. Our results indicate that the US/La-doped ZnFe LDH/PDS process has great potential for efficient degradation of metribuzin-contaminated water and wastewater.
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•Flammulina velutipes polysaccharide (FVP) was degraded by ultrasound.•Kinetics models of FVP ultrasonic degradation were established.•Ultrasound increased the thermal stability and ...crystallinity of FVP.•Viscosity and gel strength of FVP were decreased by ultrasound.•Ultrasound effectively improved the prebiotic activity of FVP.
The controllable ultrasonic modification was hindered due to the uncertainty of the relationship between ultrasonic parameters and polysaccharide quality. In this study, the ultrasonic degradation process was established with kinetics. The physicochemical properties and prebiotic activity of ultrasonic degraded Flammulina velutipes polysaccharides (U-FVPs) were investigated. The results showed that the ultrasonic degradation kinetic models were fitted to 1/Mt-1/M0 = kt. When the ultrasonic intensity increased from 531 to 3185 W/cm2, the degradation proceeded faster. The decrease of polysaccharide concentration contributed to the degradation of FVP, and the fastest degradation rate was at 60 °C. Ultrasound changed the solution conformation of FVP, and partially destroyed the stability of the triple helix structure of FVP. Additionally, the viscosity and gel strength of FVP decreased, but its thermal stability was improved by ultrasound. Higher ultrasonic intensity led to larger variations in physicochemical properties. Compared with FVP, U-FVPs could be more easily utilized by gut microbiota. U-FVPs displayed better prebiotic activity by promoting the growth of Bifidobacterium and Brautella and inhibiting the growth of harmful bacteria. Ultrasound could be effectively applied to the degradation of FVP to improve its physicochemical properties and bioactivities.
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