Deyi Jiang

A novel route for preparation of superhydrophobic multi-scale films on stainless steel via etching and electrophoretic deposition process

Abstract Superhydrophobic aluminium films have been successfully fabricated on steel substrate via chemical etching and electrophoretic deposition processes, followed by 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS) modification. The resultant surface is investigated by field emission scanning electron microscope (FESEM), atomic force microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR). The results show a hierarchical multi-scale structure and a grafted FAS film with low surface energy on the resultant sample surface, which confers excellent superhydrophobicity with a water contact angle of 168.9° and a sliding angle of ca. 1.5°. Such a superhydrophobic steel substrate shows an excellent anti-adhesion behaviour and anti-corrosion property against corrosive liquids. Furthermore, it also holds its superhydrophobicity even after a long-time exposure to air. Our work may provide a novel and facile fabrication route to prepare other functional superhydrophobic films on metal substrate for various applications.

Fabrication of mechanically robust superhydrophobic aluminum surface by acid etching and stearic acid modification

Abstract The aluminium surface with multi-scale structure has been fabricated via a facile and rapid solution-phase etching method by HCl/H2O2 etchants. After modification with stearic acid solution, the wettability of the etched aluminum surface turns into superhydrophobicity with an optimal water contact angle of 160° ± 2° and a sliding angle of 4° ± 1°. The processing conditions, such as the etching time, modifier types and the concentration of H2O2 are investigated to determine their effects on the surface morphology and wettability. As a result, the obtained sample shows excellent anti-adhesion property and bouncing phenomenon of water droplet. It can withstand mechanical abrasion for at least 100 cm under 12.3 kPa, or hydrostatic pressure under 24 ± 1 kPa without losing its superhydrophobicity, suggesting superior mechanical durability. Moreover, the surface also remains superhydrophobicity even after contacting corrosive liquids or long-term exposure in air over 100 days. Such a mechanically durable superhydrophobic aluminum surface can provide a promising practical application in various fields.

Comparison of cavern formation in massive salt blocks with single-well and two-well systems

Abstract The authors of this article have conducted a comparison study to investigate the construction characteristics of both single-well and two-well systems; two model experiments were conducted using large-size moulded rock salt specimens. An experimental platform was designed to simulate the process of leaching and a theoretical equation of calculating and predicting the cavern volume was derived. The experimental results illustrate that the variation trend of brine instantaneous concentration for single-well and two-well systems is identical, and an equilibrium state appears at last. Moreover, the equilibrium is reached early, after 5–8 pumping cycles. The construction rate in the two-well system is faster than the single-well system, and this phenomenon is observed mainly in the early periods (1–3 pumping cycles). Besides, the cavern shapes for the two construction methods are also found to be distinctive. The cavern of the single-well system has a circular cross section and an axisymmetric profile while that of the two-well system has an ovular cross section and a non-axisymmetric profile.

A Damage Constitutive Model of Rock Salt Based on Acoustic Emission Characteristics

The acoustic emission (AE) signal observation is a technique to observe the generation of microcracks in rock salt. By monitoring acoustic emission in whole process of stress - strain curve under uniaxial compression tests, the damage characteristic of rock salt is obtained. Damage to the rock salt appears to be mainly a shear failure under the condition of a lower loading strain rate. After shear failure, a lot of small crushed particles spread on the surface of the failure surface. The AE rate-strain curve is able to reflect the damage development process with better consistency which is evident from the stress-strain curve. A damage constitutive model of rock salt is suggested on the basis of acoustic emission characteristics.

Experimental Analysis of Sandstone Under Uniaxial Cyclic Loading Through Acoustic Emission Statistics

The aim of this study is to assess the evolution of acoustic emission (AE) energy distribution and acoustic emission waiting time of sandstone under uniaxial cyclic loading. Experimental study was conducted to collect AE data for this purpose. The uniaxial cyclic loading test results were statistically analyzed to determine the change in the AE energy distribution as the number of loading cycles increases. The outcomes of this study show that the relationship between energy distributions of acoustic emission signals, P(E), and the absolute energy level can be expressed by a power law where its exponent, ε, changes as the number of cycles increases. Close to the failure stage, ε decreases sharply as the number of cycles increases in accordance with the mean field theory. Furthermore, the existence of temporal correlations was studied by the waiting time and it reveals the existence of acoustic emission signals clustering also in power law (characterized by τ). The evolutions of ε and τ identify a way to signal cyclic loading collapse for brittle material before the sudden disaster failure.

Preparation and droplet impact dynamics of superhydrophobic nano-aluminum films on metal substrates

A simple electrophoretic deposition method followed by stearic acid modification was developed to prepare superhydrophobic multiscale nano-aluminum films on a series of metal substrates such as nickel, copper, titanium and stainless steel. The surface morphology and chemical compositions were characterized by a field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscope, Fourier-transform infrared spectrophotometer and white light interferometer. The resultant nano-aluminum films exhibited excellent superhydrophobicity with a water contact angle of 168.5° and a water sliding angle of 2°. Furthermore, the obtained nano-Al films showed the desirable stability and durability after the related testing. In addition, the impact dynamic behaviors of water droplet on the superhydrophobic nano-Al films were described via the corresponding parameters, such as Weber number (We), spreading factor (β), contact time (tc), etc. Based on these characteristics, the superhydrophobic nano-Al films presented excellent water-repellent property. The EPD process is an efficient method to prepare superhydrophobic nano-Al films on common engineering metal materials, which can be applied to various industrial or manufacturing fields, including oil–water separation, anti-icing, self-cleaning, anti-corrosion, microelectronic fabrication and so forth.

Self-healing capacity of damaged rock salt with different initial damage

In order to analyze the healing effectiveness of rock salt cracks affected by the applied stresses and time, we used the ultrasonic technology to monitor the ultrasonic pulse velocity (UPV) variations for different initial stress-damaged rock salts during self-healing experiments. The self-healing experiments were to create different conditions to improve the microcracks closure or recrystallized, which the self-healing effect of damaged salt specimens were analyzed during the recovery period about 30 days. We found that: The ultrasonic pulse velocity of the damaged rock salts increases rapidly during the first 9 days recovery, and the values gradually increase to reach constant values after 30 days. The damaged value and the healed value were identified based on the variation of the wave velocity. The damaged values of the specimens that are subject to higher initial damage stress are still keeping in large after 30 days recovery under the same recovery condition It is interesting that the damage and the healing were not in the linear relationship, and there also existed a damage threshold for salt cracks healing ability. When the damage degree is less than the threshold, the self-healing ratio of rock salt is increased with the increase in damage degree. However, while the damage degree exceeds the threshold, the self-healing ratio is decreased with the increase in damage.