Research On Non-boiling Evaporation Behavior of Fixed Droplets On Aluminum Plate Surface

In this paper, the non-boiling evaporation (30 -70?) of the fixed droplets on the Aluminum plate surface was investigated by the experiment. The effect of the plate temperature and initial volume on the contact angle, contact diameter and evaporation time were considered. The results showed that the temperature and initial volume were important for the droplets evaporation. As the heating plate temperature increased, the evaporation rate increased and the initial contact angle decreased. At the same heating plate temperature, the evaporation rate and the initial contact angle decreased with the increase of the droplets initial volume. At the constant temperature hydrophilic surface, the droplet evaporation is performed in two modes: Constant contact radius mode (CCR mode) and mix mode. The CCR mode were about 90% of the time at the droplets evaporation process and the droplet contact diameters kept constant with the increase of the evaporation time. For the mix mode, the contact angle and contact diameter decreased with the increase of the evaporation time.

Effect of Glow-Discharge Plasma Treatment on Contact Angle and Micromorphology of Bamboo Green Surface

The inner and outer surfaces of bamboo stems are usually removed prior to the manufacture of bamboo panels because the surfaces are hydrophobic and difficult to bond with glue. Hence, the recovery and utilization ratio of bamboo during processing is low. This study focused on using glow-discharge plasma to treat green bamboo surfaces to make them less hydrophobic. The effects of plasma treatment on green bamboo stems were examined using contact goniometry (wettability), non-contact confocal profilometry and scanning electron microscopy (SEM). Confocal profilometry and SEM revealed that the morphology of green bamboo surfaces varied between 3 different stems. Plasma was able to etch bamboo green surfaces, and make them rougher and more powdery. Plasma treatment was effective at converting green bamboo surfaces from hydrophobic (initial contact angle >110°) to hydrophilic (contact angle <20°). However, this effect was temporary and contact angle increased with time and recovered approximately 30% of its original value after 24 h. Based on our findings, we conclude that plasma treatment can alter parameters such as surface energy and roughness that could improve glue bonding of green bamboo, but delays between plasma treatment and further processing would need to be minimized.

Limiting speeds of high-speed ball bearings considering prevention of skidding and overheating conditions

Based on quasi-dynamic and moving heat source methods, this article presents a new model to investigate skidding and overheating in ball bearings considering dynamic-thermal coupling effect. Using this model and finite element method, the critical minimum loads for prevention of skidding and the critical maximum loads for prevention of overheating are obtained by the developed software. The limiting speeds of high-speed ball bearings are defined considering prevention of skidding and overheating conditions. Results show that a smaller initial contact angle, oil lubrication, and hybrid ceramic bearing can enlarge the limiting speeds of angular contact ball bearings. Experiments prove the reliability of the method in this article.

Controlling the contact angle of biological sessile drops for study of their desiccated cracking patterns

Controlling the initial contact angle of biological sessile drops to advance the study and applications of their desiccated cracking patterns.

Investigation of Optimizing Arrangement Forms for Combined Angular Contact Ball Bearings

The combined angular contact bearings are widely used in numerous rotating machinery system, but few research works on the combined angular contact ball bearings have been reported. To solve the problem about inconsistency fatigue life of the bearings in the combined bearings with asymmetric arrangement, this paper proposed a special combined bearings arrangement form in which the bearings with different contact angles are used simultaneously for the bearing combination. In order to validate the effectiveness of the proposed method, a mathematical model is proposed to analyze the load distribution, life and stiffness of the combined bearings, and the combined bearings with three different arrangements are comparatively calculated and analyzed. The results show that the whole life of combined bearings is mainly depend on the life of the bearing under heavy load, and the new arrangement form in which the initial contact angle of the bearing under heavy load is increased that can improve the whole life of combined bearings.

Noncovalent Spiropyran Coatings for Photoinduced Wettability Switching

The noncovalent binding of spiropyran to candle-soot-covered surfaces is investigated for wettability switching using a coating procedure realized with a drop casting process of using 0.001 mol/L spiropyran in a 5 : 1 toluene-acetone mixture. Scanning electron microscopy images reveal a resulting surface with spiropyran flakes in the candle soot. A reversible switching with UV light and blue or green light is achieved, starting from an initial contact angle of 130° ± 9.68°. The highest contact angle difference is 41° and reversibility has been shown for several switching cycles. Hence, our methods provide an easy-to-use strategy to generate surfaces with switchable wettability.