Cavitation Exposure Research Articles

High-entropy carbides designed to resist cavitation erosion-corrosion in an acidic environment: Surface engineering guided by first-principles calculations and experiments

In this study, the influence of chemical composition on phase stability, mechanical and electronic properties of (TixZr0.2Nb0.2Ta0.2Mo0.4-x)C (x = 0.3, 0.2, 0.1) high entropy carbide ceramics (HECCs) were first explored by first-principles calculations. The results showed that the composition (Ti0.3Zr0.2Nb0.2Ta0.2Mo0.1)C has higher values of electron work function (EWF) value and theoretical hardness than that of the other HECCs with lower Ti concentrations. Following this investigation, a (Ti0.3Zr0.2Nb0.2Ta0.2Mo0.1)C HECC coating was deposited onto a commercially pure titanium substrate by a reactive-sputtering method. The as-prepared HECC coating had a uniform thickness of ∼17 μm and consisted of equiaxed nanocrystals with a mean diameter of ∼7 nm. The cavitation erosion-corrosion behavior of the HECC coating was studied by combining electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) measurements in a 0.05 M H2SO4 solution. The EIS results revealed that with increasing time of cavitation exposure, the resistance value of the HECC coating was an order of magnitude larger than that for uncoated CP-Ti for a given cavitation time. EN analysis indicated that under cavitation conditions, uncoated CP-Ti was more vulnerable to localized corrosive attack than the HECC coating in an acidic environment.

Kinetics of fibrin clots destruction under ultrasonic cavitation

We studied the kinetic features of fibrin clot destruction in vitro under the action of ultrasonic cavitation generated by low-frequency (36 kHz) ultrasound (US) with the intensity I0 of 4.4–51.2 W/cm2, using a flexible waveguide concentrator. It was established that the rate of US destruction of clots immersed in saline at the initial stage of the process is proportional to I0 in the range of 12–51 W/cm2, corresponds to first-order kinetics, and is determined by the erosive processes without the formation of D-dimers and other fibrinolysis products at a minimum contribution of sonochemical reactions. The clot destruction rate is maximum at the initial time moment and decreases with increasing the US exposure duration (by 35 % in 1 min and by 72 % by the end of the second minute at I0 = 51.2 W/cm2). It was shown that in order to increase the completeness of clot destruction at a minimum administered US dose, it is advisable to minimize the US exposure time when using the highest values of the US intensity limited by the level of safe cavitation exposure to the vascular wall, hemostasis, and blood cells.

Increasing the Efficiency of Taxifolin Encapsulation in Saccharomyces cerevisiae Yeast Cells Based on Ultrasonic Microstructuring

The aim of the present study was to investigate the possibility of encapsulating the plant antioxidant taxifolin in the living cells of the yeast Saccharomyces cerevisiae. Taxifolin is an unstable substance prone to oxidative degradation and actively enters into chemical reactions with a decrease or loss of bioactive properties. To minimize these problems, the use of encapsulation technology has been proposed. The cells of the yeast Saccharomyces cerevisiae have been chosen as a protective material for taxifolin. The encapsulation process was carried out using simple diffusion methods in living Saccharomyces cerevisiae cells in a thermostatically controlled shaker for 24 h. The aim of the study was to evaluate the effect of preliminary microstructuring of taxifolin on the efficiency of its encapsulation in yeast cells. The microstructuring process was carried out using low-frequency ultrasonic cavitation exposure for 7 min with a frequency of 22 ± 1.6 kHz and a power of 600 W/100 mL. The studies confirmed the feasibility of the proposed approach. It was found that microstructuring changes the dispersed composition of taxifolin particles and their morphology in solution and also increases the value of the antioxidant activity. Preliminary microstructuring of taxifolin increases the efficiency of its encapsulation in Saccharomyces cerevisiae yeast cells by 1.42 times compared to the initial form. A positive dependence of the growth of the encapsulation efficiency on the duration of the process was also established. Thus, the conducted studies confirmed the advantage of encapsulation of taxifolin in living cells of the yeast Saccharomyces cerevisiae in microstructured form.

High-frequency acoustic cavitation in the technology of producing milk and dairy products

The article tells us about the issue of the influence of high-frequency acoustic cavitation on the quality characteristics of raw milk and white cheese produced with its use. It is shown that with the duration of milk processing for 30 minutes and the impact power of 45 kHz, the number of bacteria of the Escherichia coli group decreases by 40% and native calcium is preserved, which is subsequently necessary for the formation of a high-quality cheese layer. The effect of high-frequency acoustic cavitation on the components of milk, such as fat and protein, has been studied. It is established that during the initial period of exposure to high-frequency cavitation, there is a crushing of fat particles - homogenization with subsequent agglomeration, and then the release of free (destabilized) fat. It is worth noting that acoustic cavitation does not have a negative effect on the protein component of milk. Thus, whey proteins, which are most susceptible to denaturation (precipitation) during heat treatment, remain in the native state during cavitation exposure. The authors concluded that high-frequency acoustic exposure is technologically feasible in the production of high-protein products, in particular, in the production of white cheese. The results of histological analysis indicate that calcium in this type of processing in cheese has a structured appearance and larger associations in size compared to cheese obtained from unprocessed milk, which has a positive effect on the quality of the protein matrix of the product.

Using the developed cavitation test to evaluate erosion resistance of cermet thermal sprayed coatings

Many machinery parts working in contact with a fast-flowing fluid flow (e.g. turbine blades of hydroelectric power plants, valves, pump impeller blades, ship propellers, cooling systems for various units, etc.) are subjected to such type of wear as cavitation erosion. An important objective is to eliminate or reduce cavitation erosion so as to achieve a considerable economic effect. This research uses a patented technique developed to evaluate the cavitation erosion resistance of cermet thermal spray coatings (WC–10Co4Cr and WC–20CrC–7Ni). These coatings were prepared using high velocity air fuel thermal spraying (HVAF). The aim of this study is to test a new technique for evaluating coating cavitation resistance, which differs from the standard one by specimen positioning relative to the testing liquid. In addition, scanning electron microscopy (SEM) was used to analyze the initial structure of the coatings prepared and study their behavior after cavitation exposure. The material volume loss criterion during the cavitation test was used to evaluate the coating resistance. The results of cavitation tests showed that the WC–20CrC–7Ni coating has a somewhat higher cavitation resistance than that of WC–10Co4Cr despite its slightly lower average hardness (850±90 HV0.5 versus 950±60 HV0.5). The study of coating surfaces and cross-sections showed that they feature by different erosion mechanisms. It can be concluded that the presence of defects (pores) in the coating structure is the main reason for reducing their cavitation erosion resistance. Therefore, the developed technique proved effective in obtaining experimental data to analyze cermet thermal spray coatings for cavitation wear.

Microstructural and Cavitation Erosion Behavior of the CuAlNi Shape Memory Alloy

Microstructural and cavitation erosion testing was carried out on Cu-12.8Al-4.1Ni (wt. %) shape memory alloy (SMA) samples produced by continuous casting followed by heat treatment consisting of solution annealing at 885 °C for 60 min and, later, water quenching. Cavitation resistance testing was applied using a standard ultrasonic vibratory cavitation set up with stationary specimen. Surface changes during the cavitation were monitored by metallographic analysis using an optical microscope (OM), atomic force microscope (AFM), and scanning electron microscope (SEM) as well as by weight measurements. The results revealed a martensite microstructure after both casting and quenching. Microhardness value was higher after water quenching than in the as-cast state. After 420 min of cavitation exposure, a negligible mass loss was noticed for both samples. Based on the obtained results, both samples showed excellent cavitation resistance. Mass loss and morphological analysis of the formed pits indicated better cavitation resistance for the as-cast state (L).

Formation of structure of disperse systems in non-equilibrium state under conditions of combination of two types of cavitation effects

The description of the existing method for producing invert syrup in stages in a large volume under the conditions of using one type of energy flow is given. The purpose of this work is to develop the principles of transition from macrostatic equilibrium to the development of each microstatic volume of liquid dispersed systems in the process of their production in a non-equilibrium state created by the combination of two types of cavitation effects: hydrodynamic and acoustic effects. The properties of dispersed systems are described and the object of research is invert syrup with the amount of dry 80% and reducing 79-80% substances. Invert syrup with 100% inversion of sucrose to glucose and fructose is widely used in the production of flour confectionery and a number of pastille and marmalade products. The principles of formation of aggregates from sucrose molecules at the stage of sugar dissolution, the formation of voids and the nucleation of gas phase bubbles are established. The conditions for creating a non-equilibrium state of syrup under the conditions of using two types of energy flows, by combining hydrodynamic and acoustic cavitation, are considered. The character of the transformation of the state of bubbles under conditions of changing the flow geometry of gas-liquid systems and the excitation of sound vibrations in them is shown. The mechanism of structure formation of a gas-liquid system under the influence of acoustic vibrations on the structure is described. The character of transformation of highly concentrated gas-liquid systems after the collapse of gas phase bubbles is shown, which was the determining factor in the formation of new types of materials. The practical output of this work was the creation of invert syrup with 100% fructose and glucose content in dry substances. Preparation of an emulsion for flour confectionery products and marmalade based on fresh fruits and vegetables. The effectiveness of combining two types of cavitation exposure opens up the prospect of creating new types of confectionery products with fundamentally new properties, while preserving native vitamins and nutrients.

How do neuroglial cells respond to ultrasound induced cavitation?

Reactive astrocytes are known to play a vital role in the overall response of the brain during a traumatic brain injury (TBI). Modern studies have speculated the existence of cavitation in the skull during a TBI, which has alarming potential to cause detrimental damage. Previous studies have confirmed the upregulation of various harmful genes in neurodegenerative diseases. Studying the longitudinal presence of these harmful genes in response to cavitation allows for optimized understanding of and treatment methods for cavitation exposure. We seek to characterize the longitudinal genetic expression levels that astrocytes exhibit after exposure to cavitation and further elucidate the startling presence of cranial cavitation. We have designed a system to induce cavitation on targeted microbubbles. Astrocytic expression levels of various common genes, like TNFα, IL-1β, and NOS1, that have been documented in TBI studies are our target of interest. Results summarize specific gene trends from 1 h to 48 h after cavitation. Our data conclude that maximum expression is not consistently exhibited immediately after cavitation exposure and most genes have individualized genetic trends. IL-1β shows a decreasing expression over 48 h, and TNFα shows upregulation until the 6 h time point but then begins to decrease in expression. The upregulation of NOS1 has been documented in neurodegenerative diseases, like Alzheimer’s and Parkinson’s disease. This study has shown a consistent upregulation in NOS1 expression from 0 h to 48 h. These results postulate a possible linkage between cavitation damage and neurodegenerative diseases. This analysis also provides novelty in optimizing treatments for the astrocytic function after TBI and legitimizing the concern of cranial cavitation existence.

Local Carpet Bombardment of Immobilized Cancer Cells With Hydrodynamic Cavitation

This study presents a method based on carpet bombardment of immobilized cells with cavitating flows. For this, immobilized cancer cell lines are exposed to micro scale cavitating flows from the tip of a micro nozzle under the effect of cavitation microbubbles. The deformation as a result of cavitation bubbles on exposed cells differs from one cell type to another. Therefore, the difference in cell deformation upon cavitation exposure (carpet bombardment) acts as a valuable indicator for cancer diagnosis. The developed system is tested on HCT-116 (Human Colorectal Carcinoma), MDA-MB-231 (Breast Adenocarcinoma), ONCO-DG-1 (Ovarian Adenocarcinoma) cell lines due to their clinical importance. The mechanical effects of cavitation are examined by considering the single-cell lysis effect (the cell membrane is ruptured, and the cell is destroyed) with the help of the Scanning Electron Microscopy (SEM) technique. Our study proposes a promising label-free method for the potential use in cancer diagnosis with cavitation bubble collapse, where microbubbles could be precisely controlled and directed to the desired locations, as well as the characterization of the biophysical properties of cancer cells. The proposed approach tool has the advantages of label-free approach, simple structure and low cost and is a substantial alternative for the existing tools.

A Scoping Review of Excessive Prenatal Ultrasonography as a Potential Risk Factor for Autism

For the past several decades, abdominal/pelvic prenatal ultrasonography (P-USG) has been the most significant technology used in obstetrics. There has been a tremendous increase in use throughout the world and there have been many improvements in the technology used. However, there are aspects of the technology such as frequency, exposure time, thermal and cavitation exposure indices, and increased acoustic output of the ultrasonic waves that possibly could be harmful to the embryo/fetus. In particular, prolonged exposure may increase susceptibility to Autism Spectrum Disorder (ASD). Along with the increasing use of P-USG, there has been a similar increase in the incidence of ASD. The diagnosis of ASD has been found to be more common in geographic areas with a more affluent ethnicity, high socioeconomic status, and high parental education. These are also areas where prenatal ultrasonography is readily available and affordable. Given that there are biophysical risks from P-USG, especially in non-medical settings, P-USG may emerge as a possible risk factor for ASD. The past history of radiography provides a historical perspective: the predominant past opinion years ago was that exposure to X-rays during pregnancy caused no significant risk to a fetus. However, the association between X-ray exposure and childhood leukemia was only established 40 years after X-ray use began. This review focuses on the literature which supports the generation of the hypothesis that excessive P-USG usage may be a factor in the etiology of ASD.

Evaluation of synergistic effect and failure characterization for Ni-based nanostructured coatings and 17-4PH SS under cavitation exposure in 3.5 wt % NaCl solution

The Ni/SiC nanocomposite and Ni nanocrystalline coatings were electrodeposited on a 17-4 precipitation hardening stainless steel substrate. The failure characterization of specimens as well as synergistic effect of cavitation and corrosion, and the influence of the mechanical, electrochemical, and microstructural attributions of the Ni-based nanostructured and 17-4 PH stainless steel substrate on their cavitation resistance were investigated. The surface morphology of 17-4PH stainless demonstrated the quasi-cleavage failure mechanism, and both coatings had the dimpled rupture morphology after the cavitation deterioration in both mediums. The results also represented that the synergism contribution of cavitation and corrosion was 29.5, 22.6, and 6.3% for 17-4 PH stainless steel substrate, Ni nanocrystalline, and Ni/SiC nanocomposite coatings, correspondingly.

Method and means of cavitation erosion tests under abnormal conditions

The monitoring method for erosion resistance of metals and protective coatings under cavitation exposure in abnormal operating conditions is proposed. This method extends the scope of the standard ASTM G32-10 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus. The specialized ultrasonic device has been developed for the study of cavitation destruction of materials and coatings at high pressures, temperatures up to 1000 °C and in liquid media with various properties (including aggressive ones) for implementing the monitoring method. The control system based on continuous monitoring of electric parameters of piezoelectric vibratory system was used to providing the necessary vibration amplitude in the process of cavitation under all changes of liquids parameters. The control system (based on changes monitoring of liquid active resistance) was used for equal efficiency of cavitation process on the surface. Practical recommendations for testing of cavitation erosion of metals and protective coatings in abnormal conditions are given.

Damage mechanisms in cavitation erosion of nitrogen-containing austenitic steels in 3.5% NaCl solution

Interruptions of the passive layer of stainless steels by cavitation erosion expose the bare metal surface to the environment and can lead to cavitation-erosion-corrosion damage and synergistic effects. However, the probability for pitting corrosion is decreased during cavitation exposure of stainless steels in chloride solutions because mechanical passive film removal shifts corrosion potentials to lower cathodic values. In this study, the impact of 3.5 wt% NaCl in water on mass loss and damage features of two austenitic stainless N-containing steels is investigated to amend the understanding of cavitation erosion of passivating steels. Ultrasonic cavitation tests were carried out on steels 316LVM and CNMo0.95 in distilled water and 3.5% NaCl solution. Exposed surfaces were characterized qualitatively by light- and electron-microscopy and quantitatively by confocal microscopy. Damage mechanisms vary between the two steels but not with NaCl content in the solution. 316LVM also displayed the same mass loss in both solutions. CNMo0.95 possesses twice the strength as 316LVM, resulting in lower intensities of ductile damage mechanisms and slower damage progression. Mass loss of CNMo0.95 was lower in 3.5% NaCl solution compared to distilled water, which was primarily assigned to the effect of the salt content in the water on cavitation bubble formation.

Cavitation Erosion Resistance of Laser Beam Nitride Layers of X5CrNi18-10 Stainless Steel

The use of nitration in technical applications, as thermochemical treatment, regardless of the used method (ionic, gas or laser beam nitration) is realized to obtain a nitrogen rich layer, which increase the resistance to shock or abrasion, as a result of the high hardness obtained. All the previous cavitation researches showed that hardness is an important mechanical properties, for cavitation erosion resistance increase. The present paper show some results regarding the cavitation erosion behavior of laser beam nitrated layers. As basic material was used the austenitic stainless steel X5CrNi18-10. This material is frequently used for manufacturing details subjected to cavitation, such as valves, drawers of hydraulic distribution and regulation devices, or the retaining ring for butterfly valves. There were used three power regimes of the laser beams: 120 W, 180 W and 240 W. To obtain cavitation erosion was used the standard device with piezo-ceramic crystals of Timisoara Polytechnic University Cavitation Laboratory. The cavitation erosion comparisons, both with the basic material subjected only to the common thermochemical treatments and with the laboratory cavitation standard steel (OH12NDL), show that the nitrated surfaces presents increased cavitation erosion behavior, the principal factor being the important hardness increase of the nitrated layer. We mention also, that for higher laser beam powers the thickness of the nitrated layer increases. All the images obtained at the end of tests show that the cavitation exposure was stopped before overtaking the nitrated layer. So, all our results concern only the hardened layers.

Recommended Procedures to Test the Resistance of Materials to Cavitation Erosion

Abstract Predicting cavitation erosion under full-scale operating conditions is difficult and relies on laboratory testing using accelerated methods such as ASTM G32-09, Standard Test Method for Cavitation Erosion Using Vibratory Apparatus, and ASTM G134-95, Standard Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet. The main difficulty is that full-scale cavitation intensity is often unknown, and correlating cavitation field characteristics of the accelerated method and the full scale is not obvious. The problem is more acute for compliant polymeric coatings, used for protection or repair of parts subject to cavitation. Extensive testing of such materials shows that, unlike metallic surfaces, they are highly resistant to low-intensity cavitation but fail catastrophically when the intensity exceeds a certain threshold. Such behavior creates the risk of accepting a candidate coating for its resistance to cavitation if the coating was tested at a low cavitation intensity not representative of the application field conditions. This highlights the need to conduct tests with a range of cavitation intensities rather than a single intensity. This article uses results from extensive tests under various forms of cavitation to propose a generalized definition of cavitation intensity. It then presents data on the response of both metals and polymeric coatings to various levels of accelerated cavitation. A new method to test the coatings at varying cavitation intensities is then presented. Such tests provide maps of material resistance to different levels of cavitation and are helpful to make an informed decision. The tests also show that during cavitation exposure, the coatings are subjected not only to mechanical stress but also to significant heating, which dynamically modifies their properties during the exposure. Temperature rise in the coating when exposed to cavitation is directly connected to the cavitation intensity to which it is exposed, and this interaction needs to be considered.

Roughness Parameters during Cavitation Exposure of Nodular Cast Iron with Ferrite-Pearlite Microstructure

The cavitation erosion resistance of EN-GJS-400-15 nodular cast iron was tested in the laboratory according to ASTM G32- 2010 standard. The erosion average penetration depth values, MDE, were correlated with the roughness parameters and the microstructure of the samples subjected to volume heat treatments consisting from stress relieving and for softening, annealing, normalization and quenching followed by tempering. The results obtained showed that the changes in the surface roughness of the samples tested at cavitation can be used to predict the resistance of the material to this wear phenomenon.

Evaluation of a Three Hydrophones Method for 2-Dimensional Cavitation Localization.

Cavitation is a critical parameter in various therapeutic applications involving ultrasound (US) such as histotrispy, lithothripsy, drug delivery, and cavitation-enhanced hyperthermia. A cavitation exposure outside the region of interest may lead to suboptimal treatment efficacy or in a worse case, to safety issues. Current methods of localizing cavitation are based on imaging approaches, such as beamforming the cavitation signals received passively by a US imager. These methods, although efficient, require expensive equipment, which may discourage potential future developments. We propose a threehydrophone method to localize the cavitation cloud source. Firstly, the delays between the three receptors are measured by detecting the maximum of their inter-correlations. Then, the position of the source is calculated by either minimizing a cost function or solving hyperbolic equations. After a numerical validation, the method was assessed experimentally. This method was able to track a source displacement with accuracy similar to the size of the cavitation cloud (2-4 millimeters). This light and versatile method provides interesting perspectives since localization can be executed in real time and the extension to three-dimensional localization seems straightforward.

Ultrasound-mediated cavitation does not decrease the activity of small molecule, antibody or viral-based medicines.

The treatment of cancer using nanomedicines is limited by the poor penetration of these potentially powerful agents into and throughout solid tumors. Externally controlled mechanical stimuli, such as the generation of cavitation-induced microstreaming using ultrasound (US), can provide a means of improving nanomedicine delivery. Notably, it has been demonstrated that by focusing, monitoring and controlling the US exposure, delivery can be achieved without damage to surrounding tissue or vasculature. However, there is a risk that such stimuli may disrupt the structure and thereby diminish the activity of the delivered drugs, especially complex antibody and viral-based nanomedicines. In this study, we characterize the impact of cavitation on four different agents, doxorubicin (Dox), cetuximab, adenovirus (Ad) and vaccinia virus (VV), representing a scale of sophistication from a simple small-molecule drug to complex biological agents. To achieve tight regulation of the level and duration of cavitation exposure, a “cavitation test rig” was designed and built. The activity of each agent was assessed with and without exposure to a defined cavitation regime which has previously been shown to provide effective and safe delivery of agents to tumors in preclinical studies. The fluorescence profile of Dox remained unchanged after exposure to cavitation, and the efficacy of this drug in killing a cancer cell line remained the same. Similarly, the ability of cetuximab to bind its epidermal growth factor receptor target was not diminished following exposure to cavitation. The encoding of the reporter gene luciferase within the Ad and VV constructs tested here allowed the infectivity of these viruses to be easily quantified. Exposure to cavitation did not impact on the activity of either virus. These data provide compelling evidence that the US parameters used to safely and successfully delivery nanomedicines to tumors in preclinical models do not detrimentally impact on the structure or activity of these nanomedicines.

Impact of time on ultrasonic cavitation peening via detection of surface plastic deformation

During ultrasonic cavitation peening, bubbles repeatedly form and collapse, which leads to high impact loads on the treated surface. At the initial stage of ultrasonic cavitation peening, the most obvious change is plastic deformation instead of mass loss on the treated specimen surface. Meanwhile the plastic deformation is beneficial for mechanical surface properties. As the cavitation exposure time increases, erosion and damage are inflicted on the metal surface due to the increase in the number of collapse events. In this respect, the treatment time is a key parameter to improve the specimen surface properties during this manufacturing process. However, the influence of treatment time on the surface properties has not yet been thoroughly investigated. In this paper, it is the first time to utilize the plastic deformation to evaluate the optimal treatment time at different input power. The plastic deformation can be deduced by the mass loss and the volume change on the treated specimen surface. Using plastic deformation, the modification of surface hardness and roughness are investigated at different cavitation exposure intervals and vibration amplitudes. It is found that significant improvement of the microhardness on the treated surface occurs at the end of incubation period. Higher vibration amplitudes of the horn tip lead to shorter incubation period and higher microhardness.

Research of erosion resistance of superficial layers of steels under cavitation

Fracture resistance of low-alloy steels 15KH1M1F, 25KH1MF, 25KH1M1F, 20KH1M1FTR and steels 20KH13, 15KH11MF, 15KH12VNMF without and with thermomechanical treatment under intense cavitation on the sample surface was investigated. Cavitation was generated by exponential-profile ultrasound emitter. The emitter end surface varies with the frequency of 20 kHz and amplitude of 30±2 microns. Erosion measurements of samples were conducted by gravimetric method. Measurement accuracy was ±0,015 mg. According to the measurements, the dependences of the erosion on the cavitation exposure time were constructed. For quasi-linear plots of kinetic curves, the destruction rate of the samples was calculated and their cavitation resistance was determined. The interrelation of resistance ( ) with microhardness (Н m ) for low-alloy steels in the form of ~С when measuring Н m in GPa was revealed. For more alloyed steels, the exponent is reduced to 2. Nitriding, hardening of coatings increase the resistance of the samples. When applying a vacuum arc coating on the heat-treated surface of the sample, its cavitation resistance is reduced by the value that depends on the coating formation process parameters.