Hongtao Liu

Biomimetic fabrication of robust self-assembly superhydrophobic surfaces with corrosion resistance properties on stainless steel substrate

A reed leaf-like superhydrophobic stainless surface is obtained by nanosecond laser direct writing. Through investigating the coupling interaction between the laser fluence and the overlapping rate, we fabricate biomimetic reed leaf-like structures on the stainless steel. This biomimetic structures reveal excellent superhydrophobicity with a water contact angle of 157 ± 1° and a sliding angle of 1 ± 0.5° after FAS-17 (1H,1H,2H,2H-perfluorodecyltriisopropoxysilane) modification. The superhydrophobicity of the as-prepared surface results from its biomimetic hierarchical micro-nanostructure and the grafted low-surface-energy fluorosilane. The superhydrophobic surface exhibits high microhardness and excellent mechanical abrasion resistance. It can maintain superhydrophobicity after sandpaper abrasion against 260 grit Al2O3 sandpaper for 2.5 m at the applied pressure of 12.5 kPa. Moreover, the superhydrophobic surface has good chemical stability in both acidic and alkaline environments. The Tafel polarization curves show that the as-prepared superhydrophobic surface has better corrosion resistance than the bare stainless steel surface. It is believed that this stainless superhydrophobic surface may have important significance in the practical application.

Preparation and properties of a new cutting pick of coal shearers

Abstract Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers. Tool bit separation, blade breaking, severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks. We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance. The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance. In addition, the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions. The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization.

Fast and low-cost method to fabricate large-area superhydrophobic surface on steel substrate with anticorrosion and anti-icing properties

A facile and quick fabrication method was proposed to prepare superhydrophobic surfaces on iron substrate by chemical immersion and subsequent stearic acid modification. The association between wettability and surface morphology was studied through altering the copper ion concentration and immersion time. Surface tension instrument, scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and electrochemical workstation were used to characterize the wettability, physical morphology, chemical composition, and corrosion resistance ability of the prepared film. Results showed that both the rough micro/nanostructures and low surface energy material play critical roles in surface wettability. The superhydrophobic film achieved a better anticorrosion property compared to barrier iron by analysis of open circuit potential, potentiodynamic polarization curves, and Nyquist plots. In addition, the superhydrophobic surface showed excellent performance of acid and alkali resistance, anti-ici...

Contact damage failure analyses of fretting wear behavior of the metal stem titanium alloy–bone cement interface

Although cemented titanium alloy is not favored currently in the Western world for its poor clinical and radiography outcomes, its lower modulus of elasticity and good biocompatibility are instrumental for its ability supporting and transforming physical load, and it is more suitable for usage in Chinese and Japanese populations due to their lower body weights and unique femoral characteristics. Through various friction tests of different cycles, loads and conditions and by examining fretting hysteresis loops, fatigue process curves and wear surfaces, the current study investigated fretting wear characteristics and wear mechanism of titanium alloy stem-bone cement interface. It was found that the combination of loads and displacement affected the wear quantity. Friction coefficient, which was in an inverse relationship to load under the same amplitude, was proportional to amplitudes under the same load. Additionally, calf serum was found to both lubricate and erode the wear interface. Moreover, cement fatigue contact areas appeared black/oxidative in dry and gruel in 25% calf serum. Fatigue scratches were detected within contact areas, and wear scars were found on cement and titanium surfaces, which were concave-shaped and ring concave/ convex-shaped, respectively. The coupling of thermoplastic effect and minimal torque damage has been proposed to be the major reason of contact damage. These data will be important for further studies analyzing metal-cement interface failure performance and solving interface friction and wear debris production issues.

Water transport control on a patterned superhydrophobic surface via laser direct writing

A simple method for fabricating line patterns on a superhydrophobic surface is demonstrated using nanosecond laser direct writing. A laser-induced superhydrophobic surfaces exhibit the excellent superhydrophobicity with a contact angle of 158° and a sliding angle of less than 5°. By changing the superhydrophilic linewidth and line intervals, the authors investigated the anisotropic wetting and adhesive properties on the as-prepared line-patterned superhydrophobic surface. The experimental results showed that the linewidth and line intervals have an important influence in anisotropic wetting, including contact angles and sliding angles in both parallel and perpendicular directions. This data allow control of adhesion by having droplets slide off at designated tilting angles on the patterned superhydrophobic surface. The water droplet array can be easily separated into any configuration, such as an upper triangular array. The as-prepared patterned superhydrophobic surface can transfer different microliter-s...

Experiment investigation on fretting wear and wear debris performance for the stem-cement interface

After the interface debonding, the body protein fluid is subsequently pumped into stem-cement fretting wear interface, serving as the lubricant. On the stem surface, whether there is the influence of protein absorption on fretting wear or not is considered in this study. The biotribological properties at the stem-cement interface were investigated by SEM. The result of hysteresis loops shows that elasticity and plasticity performance of the frictional interface materials can be damaged by fretting fatigue and material energy dissipation will increase periodically. The wear quantity of cement is mainly influenced by load and displacement. The maximum wear loss of bone cement could reach 1.997 mg. Bone cement and titanium alloy wear debris, whose size distributions are widely spread from 1 to 110 µm and 5 to 150 µm, respectively, are shaped like tuber, tear, sheet, strip, and sphere, which will induce the osteocyte damage.

Bond strength analysis of the bone cement- stem interface of hip arthroplasties

OBJECTIVEnTo study and establish the preliminary linear and modified models for the interface shear mechanics performance between implant and bone cement and to explore its damage significance.nnnMETHODnThe loosening research between artificial hip joint prosthesis stem and bone cement interface performance can be evaluated by the push-in test. Based on the debonding performance test, the analytical expressions of the average load and displacement from the debonding failure and splitting failure process were deduced and determined. The correlations of the expressions of the average load-displacement and statistical experimental data were analyzed.nnnRESULTSnIt demonstrated that the interface debonding failure mechanical model could be characterized as interface bond strength mechanical performance. Based on analysis of models and experimental data by the three statistical analysis methods, the results indicated the modified model could be better represented by the interfacial debonding strength properties. The bond stress τ and relative sliding s distribution along the embedment regional were coupling affected by both pressure arch effect and shear lag effect in bone cement. Two stress peaks of implant have been found at the distance from 0.175La loading tip to 0.325La free tip, which also verified the early loosening clinical reports for the proximal and latter region. As the bone cement arch effect, the bond stress peak tend to move to the free tip when the debonding failure would be changed into the splitting failure, which presents a preliminary study on the mechanism of early debonding failure for the stem-cement interface.nnnCONCLUSIONSnFunctional models of the stem-bone cement interfacial debonding failure are developed to analyze the relevant mechanism. The different locational titanium alloy stress, and the interfacial bond stress and the relative slides are evaluated to acquire a guide of the different positions of interfacial damage. The coupling effect which is original from the pressure arch and the interfacial shear hysteresis cumulative effect has influence on the interfacial debonding and damage process.

The underwater superoleophobic natural pomelo peel fibers powders coatings for efficiently oil/water separation

ABSTRACT The natural pomelo peel fibers powders coating was obtained by spraying method, and this coating was underwater superoleophobic and could be applied in oil/water separation. The pre-wetted sample’s separation efficiency was up to 97.0% for light or heavy oils/water mixture only in gravity-driven mass flow. And the pomelo peel powders coatings could still retain more than 98.0% separation efficiency water/soybean oil mixtures after 50 separation cycles. In this article, separation efficiency of natural pomelo peel powders coated mesh was over 97.0% in different pH water/soybean oil mixtures. All these features have shown that the natural and environment-friendly pomelo peel powders coating have enough potential applications in the field of oil/water separation.

The fabrication of superhydrophobic PTFE/UHMWPE composite surface by hot-pressing and texturing process

In this paper, we focus on improving the durability and repairability of superhydrophobic polytetrafluoroethylene (PTFE)/ultra-high-molecular-weight polyethylene (UHMWPE) composite coating via hot-press and followed texture treatment by weight and sandpaper. The hydrophobic properties were characterized by water contact angle measurement. A scanning electron microscope and step device were used to analyze the surface appearance. The anti-icing performance was characterized by a steam-freezing test in an environmental test chamber. The high-speed camera was used to analyze water droplet bouncing process and low adhesion property. The results show that the PTFE/UHMWPE superhydrophobic surface can be successfully fabricated by the hot-press and texture treatment with a contact angle of 150xa0±xa00.5°. Both the anti-icing performance and low adhesion property show an excellent level. Moreover, the total energy just consumed about 30%, as the water droplet in the process of falling and contacting was at a 10xa0mm height.