Oxygen

Example 4

3D design software and 3D drawing software were used to construct a 3D cylinder model with a diameter of 40 mm and a height of 15 mm, which was converted into an STL file and imported into SLM building software. The model was auto-sliced by the software and imported into an SLM printing system. After heating the substrate to 150° C., the René 104 nickel-based superalloy powder was added to a powder supply tank and then laid. Argon was introduced into the working chamber until the oxygen content was less than 0.1%. Then the printing procedure was carried out, and the steps of laying the powder and scanning the powder by laser were repeated until the printing was completed to obtain a cylinder.

The René 104 nickel-based superalloy powder has a particle size of 15-53 μm, a D₁₀ of 17.5 μm, a D₅₀ of 29.3 μm, and a D₉₀ of 46.9 μm.

The process parameters for SLM are as follows: a laser power of 250 W, a spot diameter of 0.12 mm, a scanning speed of 500 mm/s, a scanning pitch of 0.12 mm, and a thickness of the laid powder layer being 0.03 mm.

The scanning strategy for SLM is a stripe scanning strategy. In the stripe scanning strategy, a layer-by-layer scanning method from bottom to top is adopted, the laser scanning direction is rotated by 67° between adjacent layers, the stripe width is 5 mm, and the overlap between stripes is 0.10 mm. (no contour+solid scanning method is adopted)

The stress relief annealing parameters are as follows: a temperature of 420° C. held for 90 min, and cooling within the furnace.

The SPS parameters are as follows: a graphite mold with a diameter of 40 mm, a heating rate of 60° C./min, a cooling rate of 60° C./min, a sintering pressure of 45 MPa, and a sintering temperature of 1020° C. held for 15 min.

Before and after post-treatments of the fabricated parts, the densities are 98.34% and 99.02%, respectively, and the mechanical properties at room temperature are 987 MPa and 1065 MPa.

Example 5

113 g of sodium metal was melted and brought to 250° C. in an Inconel reactor vessel. The sodium was then stirred using a Cowles blade mixer rotating at 2000-2500 rpm. Powdered hafnium chloride (from Areva) was pulse-fed over approximately 1 hour into the stirred sodium, until 82 g of hafnium chloride had been added, at which point the reaction was halted. At the end of the reaction, the vortex in the sodium had substantially disappeared and the reactor temperature had increased to 301° C.

Once the reaction was completed, the reactor vessel was sealed, transferred to a furnace, and heated to 825° C. for four hours to reduce the surface area of the hafnium metal produced in the reaction. During this process step, unreacted sodium was removed from the hafnium metal to leave a hafnium-sodium chloride composite.

The hafnium and sodium chloride mixture was then transferred to a vacuum furnace and heated under vacuum to 2300° C., held at that temperature for one hour, and then cooled. This removed the sodium chloride and produced a button of solid hafnium.

The hafnium button was analyzed via glow discharge mass spectrometry (GDMS) and found to have 26 ppm oxygen content, 1690 ppm zirconium, and less than 150 ppm total transition metals. The results demonstrate the production of a low oxygen hafnium metal produced directly from hafnium powder consolidation.

Example 1

1 pound PTFE regrind, obtained from CSI Plastic (Millbury, Mass.), was inserted into a chamber. The chamber was heated using annular flow of hot oil at 200° C. for a nominal chamber temperature of 175° C. Oxygen was removed from the chamber using a nitrogen pressure swing inerting method. Gas flow of 20 vol % fluorine and 80% nitrogen was started at 0.4 scfm. The chamber pressure varied between 5 PSIA and 12 PSIA over the course of the experiment. The fluorine gas was fed through the chamber for 4 hours with the direction of gas flow alternated between top to bottom and bottom to top each hour. The amount of fluorine used was 4.99 pounds of fluorine per 1000 pounds of PTFE regrind. At the end of 4 hours, the oil heat was turned off and the chamber was again inerted using a nitrogen pressure swing method. Atmospheric air was fed through the chamber until the chamber temperature dropped below 55° C. The sample was tested for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using EPA method 3452A and EPA method 8321B. The sample was tested both before and after being treated with fluorine gas. The detection limit for PFOA and PFOS was 100 parts per trillion. No PFOS was detected either before or after the sample was treated. The results are shown in Table 1.