Design Of Surface Modifications Research Articles

Effect of surface modification on friction characteristics of sliding bearings: A review

The purpose of the paper is to investigate the effect of surface modification on the friction characteristics of sliding bearings. This paper reviews the previous studies on the influences of surface texture, coating materials and lubricant additives on the performance of the sliding bearings. Through the theoretical models and simulation experiments between different friction couple, the researchers found that under the condition of fluid lubrication, the surface modification design can significantly improve the friction characteristics of the surface of the friction couple, which has attracted the wide attention of researchers. The development status and latest progress in improving the surface properties of friction couple are introduced mainly from the geometrical characteristics of surface texture, the matrix of surface coating materials and the types of lubricating additives. Among them, the geometric features of texture mainly include texture shape, scale, parameters, position and combination form. The types of coating material substrates mainly include iron-based alloys and aluminum-based alloys. Lubricating oil additives mainly include ionic liquids and nanoparticles. Finally, the existing problems and future development directions of surface modification are pointed out.

Surface modification of hydroxyapatite with enzyme-catalyzed reaction: Computation-supported experimental studies

Surface modification of the selected particles for different uses (chemical, biological or commercial applications) is a frequently adopted method for industrial and scientific purposes. Thus, the molecules determined for the targeted applications can be attached to particles. However, these methods occur in several steps, at high temperatures, and for long periods of time and require the involvement of chemicals. Chemicals used in the environment and under harsh conditions lead to some restrictions (such as monomer variety and application areas) and cause energy and time loss. Presumably, these problems could be largely avoided by using enzymes, which are natural biocatalysts, in the surface modification of particles. Given this presumption, a surface modification design was devised in this study to modify the hydroxyapatite surface with methacrylic acid using the lipase enzyme. The chemical structures of the particles were characterized through Fourier Transform Infrared and Raman spectroscopy, their thermal behaviors were analyzed with thermogravimetric analysis, and simultaneous molecular modeling studies were conducted to corroborate the experimental studies.

Micro/nanoscale surface on enhancing the microchannel flow boiling performance: A Lattice Boltzmann simulation

Microchannel Heat Sink (MCHS) has been widely adopted in thermal engineering fields, such as refrigerators, chip cooling, battery packs, etc. To meet the ever-increasing demand for heat dissipation, surface modification methods adopting micro/nanoscale-modified surfaces have received considerable attention. In this paper, an advanced micro/nanoscale surface modification design is proposed based on a Lattice Boltzmann method (LBM) simulation study. Coupled boundary treatments at the inlet/outlet are developed with better numerical stability. The effects of surface wettability and micropillar on MCHS heat transfer performance are analyzed through bubbles' dynamic behaviors, Nusselt number, heat flux, and pressure drop. Design-based suggestions are proposed, and the enhancement mechanisms are explained. Results show that hydrophobic surface is more preferred for temperature-sensitive devices with low superheat requirement (Ja<0.1115), while the hydrophilic surface is more preferred for devices with a large heat dissipation requirement (Ja≥0.1286). Furthermore, the micropillar surfaces with pillar geometric factor Sp of 7 can yield the optimum heat transfer performance under a wide range of superheat conditions. Finally, an advanced design of a biphilic micropillar surface is proposed with superhydrophobic regions located at the top of the pillars, and other regions remain hydrophilic surfaces. An excellent heat transfer enhancement of 105.8% is achieved even compared with a pure hydrophilic micropillar surface. The enhancement is attributed to the superhydrophobic top regions efficiently blocking the bubbles merging process, which leads to more intense bubbles departure. These results provide a valuable guide for MCHS design and unravel the enhancement mechanism of the flow boiling process.

Tooth Surface Modification for Helical Gear Pairs considering Mesh Misalignment Tolerance

Mesh misalignment in mating the gear tooth surface is common and difficult to be determined accurately because of system deformation and bearing clearances, as well as manufacturing and assembly errors. It is not appropriate to consider the mesh misalignment as a constant value or even completely ignore it in the tooth surface modification design. Aiming to minimize the expectation and variance of static transmission error (STE) fluctuations in consideration of mesh misalignment tolerance, a multiobjective optimization model of tooth surface modification parameters is proposed through coupling the NSGA-II algorithm and an efficient loaded tooth contact analysis (LTCA) model. The modified tooth flank of helical gear pairs is defined using 6 design variables which are related to profile modification, lead modification, and bias modification. The influences of mesh misalignment on time-dependent meshing stiffness (TDMS) and STE of unmodified and modified helical gear pairs are investigated. Then, the dynamic transmission error (DTE) of modified helical gears in consideration of mesh misalignment is discussed. The results indicate that the designed modified tooth surface shows good robustness to mesh misalignment.

Experimental Design of Surface Modification of Expanded Obsidian and Determination of Water Sorption Capacity

The aim of this paper is to study the possibility of expanded obsidian and its modified product use for oil sorption, in that tetraethoxisilane (TEOS) has been used as a modifier. The optimal concentration of the modifier was determined by 50 per cent weight of expanded obsidian. The expanded obsidian was previously activated with 0,1 M solution of hydrochloric acid. IR spectrometry was used to characterise structural changes in the modified expanded obsidian samples. To determine water sorption capacity a series of experiments has been carried out. The analysis of obtained experimental data showed that after surface modification of expanded obsidian water capacity is reduced 3 times after the surface modification of EO.