Investigation of dimensional accuracy of metal droplet deposition under repulsion using a lattice Boltzmann approach

Purpose This paper aims to investigate the influence of droplet infiltration and sliding on the deposition size and make a uniform deposition by controlling the interaction between droplets, using the three-dimensional lattice Boltzmann method (LBM) based on the actual working condition. Design/methodology/approach D3Q19 Shan-Chen LB approach is developed and optimized based on the metal droplet deposition. The Carnahan-Starling equation of state and transition layers are introduced to maintain the greater stability and low pseudo velocities. In addition, an additional collision term is adopted to implement immersed moving boundary scheme to deal with no-slip boundaries on the front of the phase change. Findings The numerical results show that the new¬ incoming droplet wet and slide off the solidified surface and the rejection between droplets are the reasons for the deviation of the actual deposition length. The total length of the longitudinal section negatively correlates with the deposition distance. To improve the dimensional accuracy, the deposition distance and repulsion rate need to be guaranteed. The optimal deposition distance is found to have a negative linear correlation with wettability. Originality/value The numerical model developed in this paper will help predict the continuous metal droplet deposition and provide guidance for the selection of deposition distance.

Structure and phase composition of hydroxyapatite plasma coating

Changes in the structure, phase composition of the hydroxyapatite (HA) plasma coating were established during deposition at an initial 20 °C and 550 °C temperature of the titanium substrate and a spraying distance of 95 and 150 mm. The structure of HA coatings was analyzed by SEM and optical microscopy. DSC analysis established the transition temperatures of HA coatings to the equilibrium state. When deposited on a substrate with an initial temperature of 20 °C at a deposition distance of 95 mm, a nanostructure with a crystallite size of 21 nm is fixed in the HA coating. With an increase in the deposition distance to 150 mm, the non-equilibrium phase composition increases, the crystallite size decreases to 12 nm, the HA content decreases from 72 to 61 %, TTCP from 10 to 5 %, and the α-TCP content increases from 17 to 30 %. A non-equilibrium nano-structural state passes into a more equilibrium state with the release of heat at temperatures of 615 – 727 °C in DSC studies. The high-temperature α-TCP phase is not fixed when the coating is deposited onto a substrate with an initial temperature of 550 °C at a spraying distance of 95 mm, the content of TTCP increases by 2 times, the size of the HA phase crystallites reaches 36 nm and their size in the sprayed powder is 75 nm. The HA coating has a dendritic microstructure and does not have a thermal effect during DSC heating at an initial substrate temperature of 550 °C.

Flame Temperature Distribution and SiO2 Particles Distribution in Oxyhydrogen Flame

In the production process of synthetic silica glass, SiCl4 as precursor is imported in oxyhydrogen flame, SiO2 particles generate and distribute with different states along the flame. The flame temperature and the distance above the burner are important factors to affect the particle diameters and morphologies. The 2D distribution of flame temperature was measured using sodium line-reversal method. The diameters and morphologies of SiO2 particles were analyzed by transmission electron microscopy (TEM) at 50mm, 100mm, 200mm, and 300mm above the burner. The results show that the flame temperature ranges from 2130°C to 2320°C, and the average diameter of SiO2 spherical particles increases from 50nm to 105nm as the distance increasing from 50mm to 200mm. The optimum deposition distance was discussed.

Research on Deposition Characteristics of the Double-Nozzle in Near-Field Electrospinning

With the double-nozzle NFES process, the uncertainty is more suitable to investigate than the multi-nozzle NFES and also meet higher liquid throughput requirement than conventional electrospinning. Moreover, the key point is to control the deposition characteristics of double-nozzle NFES under the interaction of the nozzles. This paper simulates the change in electric field intensity with the change of nozzle length and voltage. The experiment shows that the deposition distance becomes smaller when needle length increases, however, the influence of voltage is opposite in certain range. According to the study above, the results could be the guidance of the multi-nozzles NEFS in manufacturing process, and also can illustrate the force distribution of the jet with further modification.