Ultrasonic Vibration Test Research Articles

Fabrication of superamphiphobic micro-reentrant structures by inverted electrochemical deposition

Due to excellent oil resistance and shortened liquid-solid contact time, superamphiphobic surfaces have promising application prospects in oil transportation, and petroleum pollution control. Although superamphiphobic surfaces have been constructed on various substrates, there is still a lack of high-efficient methods for fabricating micro-reentrant structures on engineering metal substrates. This paper proposes a new method combining laser processing and inverted electrochemical deposition techniques to achieve high-efficient and large-scale fabrication of superamphiphobic surfaces on copper substrates. Firstly, micropillar array structures are constructed by laser processing, and the structures exhibit excellent superhydrophobicity after low surface energy modification. Then, inverted electrochemical deposition is performed after polishing the top of the array, and local angle of the gas/liquid interface can be controlled by adjusting the distance between the top of the micropillar and the electrolyte level, thus regulating micro-morphology of the roof structure. The influences of electrochemical deposition parameters on characteristics of the micro-reentrant structures are systematically investigated. Finally, superamphiphobic micro-reentrant structures (roof diameter > 190 μm, micropillar spacing <250 μm) with water and oil contact angles exceeding 150° are prepared after lowering the surface energy of the deposited structures. After anti-fouling, blowing, ultrasonic vibration, and tape adhesion tests, the prepared superamphiphobic micro-reentrant structures maintained good water and oil repellency, showing excellent chemical stability and durability. The research may provide a simple, efficient, and low-cost method for high-efficient constructing superamphiphobic surfaces on engineering metal substrates, enriching the fabrication techniques of micro-reentrant structures and facilitating their practical applications.

Investigation into the Failure Characteristics and Mechanism of Rock with Single Elliptical Defects under Ultrasonic Vibrations

In order to investigate the effects of elliptical defects on rock failure under ultrasonic vibrations, ultrasonic vibration tests and PFC2D numerical simulations were conducted on rocks with single elliptical defects. The research results indicated that the fracture fractal dimension, axial strain, and crack depth of specimens with elliptical defects at 45° and 90° were the smallest and largest, respectively. The corresponding strain and fractal dimension showed a positive linear and logarithmic function relationship with time. The maximum crack depth of 46.50 mm was observed on the specimens with an elliptical defect angle of 90°. Specimens with elliptical defects at 0°, 30°, 75°, and 90° exhibited more dense and frequent acoustic emission events than those with elliptical defects at 15°, 45°, and 60°. During the ultrasonic vibration process, the maximum total energy (87.86 kJ) and energy consumption coefficient (0.963) were observed on specimens with elliptical defect angles of 30° and 45°, respectively. The difference in the stress field led to varying degrees of plastic strain energy in the specimens, resulting in different forms of crack propagation and triggering differential acoustic emission events, ultimately leading to specimen failure with different crack shapes and depths. The fractal dimensions of elliptical defect specimens under ultrasonic vibration have a high degree of consistency with the changes in axial strain and failure depth, and the fractal dimension of defect specimens is positively correlated with the degree of failure of defect specimens.

Study on hydrodynamic properties and physicochemical stability of regular packing coatings for water isotope separation

Water distillation as a mainstream separation process for water isotopes is widely applied in industrial and basic research. Regular packing, a key component of water distillation, has attracted intense research, and its excellent hydrodynamic properties and physicochemical stability can ensure long-lasting separation performance. Frictional and wear tests, ultrasonic vibration tests and hydraulic erosion tests have been proposed to determine the hydrodynamic properties and physicochemical stability of regular packing with different surface coatings. The results of all tests show that there is no significant change in the shedding, hydrophilicity and separation properties of both samples, indicating the excellent hydrodynamic properties and physicochemical stability of the stamped surface coatings. Meanwhile, an effective way is also provided to verify the performance of the regular packing for use in bulk by the mentioned tests.

Characterization of Hydroxyapatite/Chitosan Composite Coating Obtained from Crab Shells on Low-Modulus Ti–25Nb–8Sn Alloy through Hydrothermal Treatment

In this study, hydroxyapatite/chitosan (HA/CS) composite coatings were prepared by hydrothermal treatment on the surface of low-modulus Ti–25Nb–8Sn alloy to improve the surface bioactivity of the alloy. HA, the main mineral composition of the human skeleton, has excellent bioactivity and is often used as a surface coating on biometal implants. CS, a natural polymer with good antibacterial, hydrophilic and non-toxic characteristics, is often used as dermal regeneration templates, hemostatic agents and drug delivery systems. In this experiment, a natural crab shell was used as a raw material to prepare the HA/CS composite coating by alkali treatment and hydrothermal reaction at various temperatures. The microstructure, morphology and phase composition of the coating surfaces were analyzed by XRD, SEM, and FTIR, and the sample coated with HA/CS was soaked in simulated body fluid (SBF) to evaluate its bioactivity. The experimental results showed that the HA/CS composite coatings through hydrothermal treatment at various temperatures can be successfully fabricated on the surface of the Ti alloy. HA on the coating surface exhibited mainly spherical particles and contained A- and B-type carbonate. When the hydrothermal temperature was up to 200 °C, the spherical particles were approximately 20–40 nm. An ultrasonic vibration test was used to evaluate the adhesion of the coatings, showing that the CS exhibited significantly improved adhesion capacity to the substrate. After being soaked in SBF for 7 days, apatite was deposited on the entire surfaces of the HA/CS coatings, indicating that the coating possesses excellent bioactivity.

Cavitation and strain-induced transformation: the austenite phase behavior in a soft martensitic and an austenitic stainless steel * *Preliminary results of this manuscript were presented at 3rd International Conference on Surface Engineering in Material Forming (in the 40 o SENAFOR), October 13-15th 2021, Porto Alegre-RS, Brazil.

In this work the behavior of the austenite phase at the surface of a low-carbon martensitic stainless steel and an austenitic stainless steel subjected to cavitation through ultrasonic vibration tests in liquid phase was studied. Emphasis was given to the behavior of two distinct types of austenite, in the case the reversed austenite of the as-tempered ASTM CA-6NM martensitic stainless steel, and the thermally-stable austenite of the solution-treated AISI 304 austenitic stainless steel. The evolution of phases fraction at the studied surfaces by XRD technique was characterized by two ways. Firstly, cavitation test intercalated with XRD measurements as a function of the test time was carried out. In the sequence, an indirect measurement technique comprising the use of Vickers indentation and controlled material removal by polishing, also intercalated with XRD characterization along the incubation period of both steels was used. This procedure was strong enough to determine the mechanism that precedes the erosive wear defining the incubation-acceleration stages transition and the cavitation-affected depth presenting γ(austenite)→α′(martensite) strain-induced transformation in the material microstructure, measured from the surface of the tested region into the interior of the substrate bulk of each studied steel. Such mechanism covers deformation of the steel matrix and strain-induced transformation of the austenite phase at the surfaces subjected to cavitation, strongly influencing the beginning of the significant mass loss process for both low-carbon stainless steels studied here.

Modeling ultrasonic vibration fatigue with unified mechanics theory

A series of ultrasonic vibration tests are performed on A656 grade steel samples, at a frequency of 20 kHz. A fatigue life model based on the unified mechanics theory is introduced to predict the very high cycle fatigue life of metals. Then, the fatigue life test data results are compared with the unified mechanics theory based model simulation results. It is shown that the physics-based unified mechanics theory can predict very high cycle fatigue life very well, without the need for the traditional empirical curve fitting a fatigue damage evolution function. The model does not require any curve fitting parameters obtained from fatigue test data. However, it does require deriving analytical thermodynamic fundamental equation of the material subjected to ultrasonic vibration fatigue. The thermodynamic fundamental equation of the material formulates the entropy generation mechanisms during the fatigue process. There are more than half a dozen entropy generation mechanisms during fatigue process. Entropy is an additive property, hence, the entropy generation due to all active mechanisms can be added.

Tribological properties and releasing behavior of solid lubricant WS2 in the dimples on cylinder liner surface of diesel engine

Modified WS2 by silane coupling agent were encapsulated in the dimples fabricated on the surface of cylinder liner samples by hot-pressing method. The tribological properties, anti-adhesion performance of the samples as well as the releasing behavior of modified WS2 in the dimples were tested by a reciprocating tribotester. Moreover, the anti-erosion performance of modified WS2 was examined by ultrasonic vibration test. The results indicate that the composite lubrication structure has good anti-friction and anti-adhesion effects. Furthermore, the release rate of WS2 in the dimples is decreased by 102.2% due to the introduction of silane coupling agent. Additionally, the synergistic effect among the dimples, the solid lubricant and the silane coupling agent can explain the anti-friction and sustained release mechanisms.

Robust superhydrophobic 1D Ni3S2 nanorods coating for self-cleaning and anti-scaling

Enormous attention has been attracted by Ni3S2 with various microstructures and excellent properties. In this work, a solvothermal reaction was adopted to fabricate 1D Ni3S2 nanorods coating. Then a superhydrophobic surface was achieved by the followed myristic acid modification. This superhydrophobic coating significantly hindered the infiltration of water. The attached contaminants could be easily carried away by water droplets owing to the low adhesion of the coating surface. In addition, the cooperation of low surface energy and 1D nanorods structure exhibited prominent anti-scaling property that effectively blocked the deposition of calcium carbonate. Moreover, it was confirmed that this superhydrophobic coating displayed outstanding thermostability, UV resistance and durability. In addition, water sand scouring and ultrasonic vibration tests were conducted to examine the mechanical stability, and the tested samples still maintained their superhydrophobicity and integrated nanorods structure. These excellent properties make the Ni3S2 superhydrophobic coating a promising barrier for anti-scaling.

The effect of electrical charge density on the transition behavior between bonding and clogging stages of an electroplated porous surface

A copper plate with a porous layer on its outer surface can significantly enhance heat transfer performance compared with a smooth copper plate. In this work, different from the traditional powder sintering technique, a porous layer consisting of copper powders was prepared by an electroplating method. The bonding mechanism of this electroplated porous surface was analyzed by using scanning electron microscope (SEM) imaging and the X-ray diffraction (XRD) technique. The influences of the electrical charge density adopted in the preparation process on the appearance and oxide phase of the electroplated porous surface were investigated by a 3D optical profiler and energy dispersive spectroscopy (EDS) technique. Moreover, the bonding strength and anti-disturbance ability of the electroplated porous surface were summarized via a thrust test and an ultrasonic vibration test, respectively. Using water droplet spreading and down-absorption tests, the variation of wettability of the prepared porous surface was discussed. With an optimum electrical charge density, it is feasible to securely construct copper powders onto a substrate and form an inter-connective porous layer without compromising its mechanical and porous properties.

Fabrication and Characteristics of Sintered Cutting Stainless Steel Fiber Felt with Internal Channels and an Al₂O₃ Coating.

A novel sintered cutting stainless steel fiber felt with internal channels (SCSSFFC) composed of a stainless-steel fiber skeleton, three-dimensional interconnected porous structure and multiple circular microchannels is developed. SCSSFFC has a jagged and rough surface morphology and possesses a high specific surface area, which is approximately 2.4 times larger than that of the sintered bundle-drawing stainless steel fiber felt with internal channels (SBDSSFFC) and is expected to enhance adhesive strength. The sol-gel and wet impregnation methods are adopted to prepare SCSSFFC with an Al2O3 coating (SCSSFFC/Al2O3). The adhesive strength of SCSSFFC/Al2O3 is investigated using ultrasonic vibration and thermal shock tests. The experimental results indicate that the weight loss rate of the Al2O3 coating has a 4.2% and 8.42% reduction compared with those of SBDSSFFCs based on ultrasonic vibration and thermal shock tests. In addition, the permeability of SCSSFFC/Al2O3 is investigated based on forced liquid flow tests. The experimental results show that the permeability and inertial coefficients of SCSSFFC/Al2O3 are mainly affected by the coating rate, porosity and open ratio; however, the internal microchannel diameter has little influence. It is also found that SCSSFFC/Al2O3 yields superior permeability, as well as inertial coefficients compared with those of other porous materials reported in the literature.

Study on the coating of nano-particle and 3DOM LaCoO3 perovskite-type complex oxide on cordierite monolith and the catalytic performances for soot oxidation: The effect of washcoat materials of alumina, silica and titania

The novel catalysts of LaCoO3/ɤ-Al2O3/cordierite monolith, LaCoO3/SiO2/cordierite monolith, LaCoO3/TiO2/cordierite monolith were prepared by using aluminum oxide, silicon dioxide and titanium dioxide nanoparticles as washcoat and monolithic cordierite as the monolithic ceramic substrate.The obtained samples were characterized by means of XRD, SEM, EDS, BET, and ultrasonic vibration test (Medi II Pselecta). The surface area of the cordierite monolith-supported LaCoO3/ɤ-Al2O3 is larger than those of LaCoO3/SiO2 and LaCoO3/TiO2. The coating of alumina, silica oxide and titania nanoparticles could increase the surface area of monolithic cordierite and also endue the coated layer with engineered structure. The results of thermal treatment experiment indicate that the good thermal stability of the ɤ-Al2O3 coating on the cordierite. The ultrasonic vibration test results showed that the washcoat was adhered to the substrate strongly. The weight loss for the samples LaCoO3/ɤ-Al2O3/cordierite (the most desired preparation protocol in this study) eventually reached about 3%, which was considered as a low weight loss.The LaCoO3/ɤ-Al2O3/cordierite monolith catalysts were successfully prepared by coating ready-made 3DOM LaCoO3 (perovskite-type oxides) catalysts onmonolithic cordierite substrate with a dip-coating method by employing aluminasol for the first time. The catalytic activities of a series of monolithic catalystsLaCoO3/ɤ-Al2O3/cordierite, LaCoO3/ɤ-Al2O3/cordierite (3DOM-catalysts), LaCoO3/SiO2/cordierite, LaCoO3/TiO2/cordierite were evaluated for soot combustion. Thenano LaCoO3/ɤ-Al2O3/cordierite catalysts gave the highest catalytic activity for soot combustion among the studied catalysts. The T10, T50, T90 over the LaCoO3/ɤ-Al2O3/cordierite catalyst were 199.4°C, 340.5°C, 405.3°C, respectively, and sco2m was 99.9%.

Cavitation Erosion Resistance of Silicified Graphite by Liquid Silicon Penetration Technique

This technical brief studied the cavitation erosion behavior of the silicified graphite. The phase constituents, surface microstructure, and chemical compositions of silicified graphite were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively. Cavitation experiments were carried out by using an ultrasonic vibration test system. The experimental results show that the silicified graphite exhibits an excellent cavitation erosion resistance; this can be attributed to the fact that the silicified graphite has the characteristics of both the silicon carbide and the graphite. The SEM morphology studies of the erosion surfaces indicated that the inherent brittleness of SiC ceramic material results in the formation of erosion pits on the surface of silicified graphite.

Enhancement of washcoat adhesion for SCR catalysts to convert nitrogen oxide using powder spray coating of TiO2 on metallic honeycomb substrate

A novel powder spray coating method was applied to form intermediate layers on metallic honeycomb substrates to improve the adhesion property of ceramic-based washcoat layer without any binder addition. Washcoating of SCR catalysts for abatement of nitrogen oxides was performed with different numbers of coating and different amounts of washcoat loading. Metallic monoliths with the intermediate layer showed much better washcoat adhesion property than monoliths without the layer even with high washcoat loading. The surface-modified monoliths had better NO conversion performance than the samples without the intermediate layer after ultrasonic vibration test to measure adhesion property of the washcoat layers.

Ru-coated metal monolith catalyst prepared by novel coating method for hydrogen production via natural gas steam reforming

Ru-coated FeCrAlloy monolith catalysts were prepared by a deposition-precipitation (DP) method with different solution pHs and evaluated the catalytic activity in natural gas steam reforming (NGSR) reaction for H2 production. The characteristics of prepared monolith catalysts as to the crystallite size, surface area, pore size distribution, metal dispersion, and morphology of Ru particles were analyzed by XRD, BET, BJH, CO-chemisorption, and SEM, respectively. The solution pH had a major effect on the precipitation formation and the particle size and dispersion of Ru catalyst coated on the monolith surface. At pH 7, nano-sized Ru particles with high BET surface area (112m2/g) and metal dispersion (23.5%) were formed uniformly on the monolith surface. Among the prepared monolith catalysts, the monolith catalyst prepared at pH 7 showed the highest CH4 conversion in NGSR. Despite the less amount of Ru metal coated on the metal monolith, the monolith catalyst showed a good catalytic performance equivalent to the 2wt% Ru/Al2O3 pellet catalyst due to the high availability of the Ru active metal in NGSR. It was also confirmed that the Ru catalyst layer coated on the FeCrAlloy monolith had good adhesion via ultrasonic vibration test.

An innovative micro-channel catalyst support with a micro-porous surface for hydrogen production via methanol steam reforming

To improve the energy conversion of a micro-channel reactor, an innovative micro-channel catalyst support with a micro-porous surface is proposed and fabricated by a layered powder sintering and dissolution method (LPSDM). The catalyst adhesion strength is analyzed by an ultrasonic vibration test and results show the catalyst has a 7 wt. % loss on the catalyst support with micro-porous surface and a 16 wt. % loss on the non-porous surface. Subsequently, the coated catalyst support is applied to methanol steam reforming for hydrogen production. Results show that the micro-channel catalyst supports with micro-porous and non-porous surfaces respectively have a hydrogen production rate of 18.07 ml/min and 9.65 ml/min at 573 K under the inlet flow rate of 30 μl/min. Compared with the catalyst support with a non-porous surface, the catalyst support with a micro-porous surface shows better catalyst adhesion and obvious advantages in hydrogen production rate and methanol conversion.

Efficient Fischer–Tropsch microreactor with innovative aluminizing pretreatment on stainless steel substrate for Co/Al2O3 catalyst coating

In this paper, a novel aluminizing pretreatment method was developed to enable a strong adhesion of Al2O3 layers on the aluminum-free stainless steel substrate for the application of Fischer–Tropsch microreactor. The Co/Re/W/Al2O3 catalyst coated on a microreactor fabricated with 316L stainless steel was tested for Fischer–Tropsch synthesis and showed a good activity. Ultrasonic vibration test results showed that the average weight loss of the coating on the aluminized substrate was only one-eighth of that on the untreated plate. A high C5+ productivity of 759.2mgC5+/gcath was achieved at 220°C and 20atm under a gas hourly space velocity (GHSV) of 21,000h−1, and C5+ selectivity increased with decreasing CO conversion rate. Product distribution shifted toward short-chain hydrocarbons and hydrogenated products at high operation temperatures. Catalyst coating thickness was also optimized to inhibit CH4 production and adjust the olefin/paraffin ratio.

The Study of Cavitation Erosion Protection Performance of Heavy-Duty Engine Coolants

Ultrasonic vibratory cavitation erosion tests were carried out on studying the cavitation erosion protection performance of different type of heavy-duty engine coolants for cast iron material of wet sleeve cylinder liners. The influence of coolant type, freezing point, corrosion inhibitor content and test duration on anti-cavitation performance were analysed. The experimental results showed that the anti-cavitation erosion performance of organic acid type heavy-duty engine coolants were better than the inorganic salt type heavy-duty engine coolants. For the same formulation coolant, increasing the content of ethylene glycol or corrosion inhibitor can improve the anti-cavitation erosion performance. With the extension of ultrasonic vibration test time, the anti-cavitation erosion protection performance for cast iron was reduced.

A well-dispersed catalyst on porous silicon micro-reformer for enhancing adhesion in the catalyst-coating process

A Cu/Mn/ZnO catalyst slurry was modified with polyvinyl alcohol (PVA) as a dispersant and organic binder. The slurry, which forms a crack-free coating, was injected directly into an open microchannel before anodic bonding with Pyrex glass. To improve adherence, porous silicon (pore size <1 μm) was fabricated in the microchannel. Ultrasonic vibration test (180 W, 20 min) showed good adhesion with only 6 wt.% loss. The thicker catalyst layer, with lower thermal diffusivity (0.98 mm2/s), reduced heat loss during reaction on cratered design and performed better than two other geometric designs (blank, straight). The microchannel with cratered design can be deposited with a catalyst up to 24.4 mg, and has a hydrogen production rate of 0.85 mmol h−1 and 86% methanol conversion at 200 °C under a feed rate of 2SCCM.

Influence of Water Content on Dynamic Elastic Modulus of Concrete

Water content is one of key effect factors on the dynamic elastic modulus, which is an important damage assessment index of concrete structures induced by freeze-thaw cycles, fire and chemical attacks. Through the ultrasonic and bending vibration test, the regularity of dynamic elastic modulus changed with the water content of concrete specimens was analyzed in this paper. The results show that the ultrasonic velocity has a low sensitivity to water content when it is below 1.5%. The bending vibration method can better reflect the effect of water content change on dynamic elastic modulus. The regression equation of dynamic elastic modulus and water content was set up by introducing the index function. The research results offer technical reference for the predicting of actual concrete dynamic elastic modulus in different humidity environment.

Development of novel monolithic catalyst with porous hollow silica nanoparticles for selective hydrogenation reactions

Novel monolithic catalysts were prepared with Pd nano-catalysts on porous hollow silica nanoparticles (PHSNs, the supporting active sites) as washcoat and monolithic cordierite (MC) as the monolithic ceramic substrate. The coating of PHSNs could increase the surface area of MC for more than 10 times and also endue the coated layer with engineered porous hollow structure; therefore, the new monolithic catalysts were expected to keep both the excellent catalytic performance from the nano-washcoat and the fine mechanical properties from the monolithic substrate. The obtained samples were characterized with Scanning Electronic Microscope (SEM), ultrasonic vibration test and X-Ray Diffraction (XRD). SEM images showed that the monolithic catalysts were covered with a PdO/PHSNs washcoat of ∼10μm thickness. Ultrasonic vibration tests indicated that the washcoat was anchored on monolithic substrates firmly. And XRD results demonstrated that the coating layers maintained the mesoporous hollow structure of PHSNs after being coated on MC. Finally, the catalytic properties of the novel Pd-loaded monolithic catalysts were determined by selective hydrogenation of acetylene in excessive ethylene, which showed that the selectivity of Pd-loaded PHSNs-Al2O3/MC catalysts was higher than other Pd supported catalysts, and adding a proper amount of Ag to PdO/PHSNs-Al2O3/MC catalysts could further enhance the catalytic performance.