Using Atomic Force Microscopy to Evaluate Microstructure for Direct Metal Laser Melted Titanium

Additive Manufacturing (AM) is a relatively new technology that could potentially revolutionize industrial manufacturing. Currently, papers have studied the mechanical properties and microstructure of AM materials without the use of Atomic Force Microscopy (AFM). This paper utilizes AFM to analyze the Widmanstätten microstructure and porosity of Direct Metal Laser Melted (DMLM) titanium samples. The mechanical properties of the titanium samples were collected, and the samples exhibited favorable yield and tensile strengths, but suboptimal ductile properties. The DMLM titanium seemed to have an increase in yield and tensile strength while the ductility seemed to decrease as a result of the fast cooling rate utilized in the DMLM process. AFM was used when analyzing the Widmanstätten microstructure which had an average surface roughness of 142 nm and the pore depth of one sample was 3.3 μm. The substantial depth of the pores could potentially be related to the decrease in ductility and it could increase the potential of future premature fractures. AFM provided a lot of useful information for this study and could provide even more information within the metallurgical field when studying the microstructure and porosity of metals, especially for AM materials.

Noise Reduction Effect of Porous Asphalt Pavement Based on Acoustic-Structure Coupling Model

Nowadays, the traffic noise problem is becoming increasingly prominent. In order to study the influence of porosity and pore depth on the noise reduction performance of asphalt pavement, this paper used the software COMSOL Multiphysics to establish acoustic-structure coupling models, and simulated the sound absorption and noise reduction effect of asphalt pavement under 10%, 15%, 20%, 25%, and 30% porosity; moreover, under the condition of unchanged asphalt pavement porosity, the sound absorption and noise reduction effect of asphalt pavement under 3cm, 4cm, 5cm, 6cm, and 7cm pore depth was studied as well. The research results reveal that, with the increase of porosity and pore depth, the sound absorption and noise reduction effect of asphalt pavement gets better.

Factors affecting the compactness of filter cake for diaphragm wall slurry

Purpose The purpose of this paper is to explore the factors that affect the compactness of the mud filter cake, so as to prepare diaphragm wall slurry with good uniformity, small filtration loss and excellent recycling performance. Design/methodology/approach In this paper, the thickness, filtration loss and slurry viscosity of the filter cake are used as the characterization methods. The effects of pore depth, slurry specific gravity, intercalated metal ions, bridging polymer and water-soluble polymer on the compactness of the filter cake were studied. Findings The experimental results showed that the slurry's own pressure (pore depth) and specific gravity have little influence on the compactness of the filter cake and K+ can be considered as an auxiliary filtration loss reduction factor. Both the sulfonate copolymer and the potassium polyacrylate particle can significantly reduce the filtration loss of the slurry, which can effectively improve the filter cake compactness. Moreover, the composite application of potassium polyacrylate particles in the sizes of 80–100 and 150–200 meshes can exhibit a better filter cake compaction effect. Originality/value It solves the problems of high pulping cost, serious pollution of the environment, poor quality of filter cake formation and large filtration loss during the construction of the diaphragm wall, which improved the construction quality of the diaphragm wall.

Analytical and Numerical Modelling of Liquid Penetration in a Closed Capillary

The chapter explores the dynamics of liquid penetration in a closed end vertical capillary. This model is very important for impedance spectroscopy methodology where oxidized porous silicon provides an in vitro medium, and one important criteria of this methodology is the liquid penetration depth inside the silicon pores as the impedance is greatly affected by this penetration depth. This problem is also important in order to understand how the presence of entrapped air inside a micro pore can influence the dynamics of capillary flow. For this purpose, the model is studied both analytically and numerically. In this study, different pore size (500 nm and 2 µm diameter) with equal pore depth (~10 µm) have been used. Finally, the analytical solution is compared with the numerical results. In addition, the linearization of the system is also investigated and found the critical viscosity of which demarcates the over-damped and under-damped regimes. Further, this study is extended by incorporating the dynamic contact angle effects on the meniscus dynamics.

Preparation of ordered mesoporous and macroporous thermoplastic polyurethane surfaces for potential medical applications

Thermoplastic polyurethanes are widely used in medical devices. In order to limit some of their shortfalls, like microbial attachment, surfaces modifications can be required. In this work, a two-step replication method was used to create ordered macroporous and mesoporous thermoplastic polyurethane surfaces using anodic aluminum oxide as master template. The intermediate mould materials that were tested were polystyrene and a polyacrylate resin with inorganic filler. All obtained surfaces were characterized by scanning electron microscopy. The initial anodic aluminum oxide surfaces possessed macro or mesopores, function of anodization conditions. The intermediate mould structure correctly replicated the pattern, but the polystyrene surface structures (pillars) were less resistant than the polyacrylate resin ones. The thermoplastic polyurethane pattern possessed macropores or mesopores of about 130 nm or 46 nm diameter and of about 300 nm or 99 nm interpore distances, respectively, in accordance with the initial pattern. Thermoplastic polyurethanes pore depth was however less than initial anodic aluminum oxide pore depth, linked to an incomplete replication during intermediate mould preparation (60 to 90% depth replication). The correct replication of the original pattern confirms that this novel fabrication method is a promising route for surface patterning of thermoplastic polyurethanes that could be used for medical applications.

Advanced In Situ I-V Measurements Used in the Study of Porous Structures Growth on Silicon

The rate of oxide formation during growth of pores structures on silicon was investigated by in situ I-V measurements. The measurements were designed to get two I-V curves in a short time (total time for the two measurements was 300 seconds) taking into account the gap (in mA/cm2) for each corresponding voltage. The in situ I-V measurements were made at different pore depth/time, at the electrolyte-pore tip interface, while etching takes place based on p-type Si. The results showed increasing, decreasing, and constant I-V gap in time, for macropores, nanopores, and electropolishing regimes, respectively. This was related to the expected diffusion limitation of oxide forming (H2O) molecules reaching the electrolyte-pore tip and the anodizing current, while etching takes place. The method can be developed further and has the potential to be applied in other electrochemically etched porous semiconductor materials.