AVS2013 Session AC-TuP: Actinides and Rare Earths Poster Session

To date, there has been only one synchrotron-radiation-based soft X-ray study of Pu, using un-encapsulated samples. [1-9] Despite the highly radioactive nature of Pu, this study was successfully and safely performed at the Advanced Light Source, using photoelectron spectroscopy and x-ray absorption spectroscopy. Some of the impact of these measurements will be discussed, ranging from resonant photoemission to sample aging to electron correlation to the prospects of Pu clusters.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. This work was supported in part by the DOE Office of Science, Office of Basic Energy Science, Division of Materials Science and Engineering.

Reference

1. J.G. Tobin, B.W. Chung, R. K. Schulze, J. Terry, J. D. Farr, D. K. Shuh, K. Heinzelman, E. Rotenberg, G.D. Waddill, and G. Van der Laan, , Phys. Rev. B 68, 155109 (2003).

2. K.T. Moore, M.A. Wall, A.J. Schwartz, B.W. Chung, D.K. Shuh, R.K. Schulze, and J.G. Tobin, Phys. Rev. Lett. 90, 196404 (2003).

3. G. van der Laan, K.T. Moore, J.G. Tobin, B.W. Chung, M.A. Wall, and A.J. Schwartz, Phys. Rev. Lett. 93, 097401 (2004).

4. J.G. Tobin, K.T. Moore, B.W. Chung, M.A. Wall, A.J. Schwartz, G. van der Laan, and A.L. Kutepov, Phys. Rev. B 72, 085109 (2005).

5. B.W. Chung, A.J. Schwartz, B.B. Ebbinghaus, M.J. Fluss, J.J. Haslam, K.J.M. Blobaum, and J.G. Tobin, J. Phys. Soc. Japan 75, No. 5, 054710 (2005).

6. J.G. Tobin, J. Alloys Cmpds, J. Alloys Cmpds 444-445, 154 (2007).

7. J.G. Tobin, P. S ö derlind, A. Landa, K.T. Moore, A.J. Schwartz, B.W. Chung, M.A. Wall, J.M. Wills, R.G. Haire, and A.L. Kutepov, J. Phys. Cond. Matter 20, 125204 (2008) .

8. S.W. Yu, J.G. Tobin, and P. Söderlind, J. Phys. Cond. Matter 20, 422202 (2008), Fast Track Communication.

9. M.V. Ryzhkov, A. Mirmelstein, S.-W. Yu, B.W. Chung and J.G. Tobin, “Probing Actinide Electronic Structure through Pu Cluster Calculations,” International Journal of Quantum Chemistry, doi: 10.1002/qua.24417 (2013).

* This paper is dedicated to the memory of Dr. S. Eklund, J. Oliver and M. Chemla

In this paper, we present a realistic model for estimation of trivalent actinides and lanthanides ions self diffusion coefficients. We take account hydrolysis phenomena. We use Fuoss theory and Bjerrum approach to calculate K_h the thermodynamic hydrolysis constant using Marcus summarized data for different radius. We suppose that ion structure stills the same in solid state (salt) or in aqueous solution, regarding the water molecules surrounding central ions (M≡ La³⁺ , Ac³⁺). Taking account hydrolysis, experimental self-diffusion coefficient D of ion is equal to the sum of two contributions: free and associated ion.

In our recent paper, we have verified our simplistic calculus method with experimental data for Lanthanum and Gadolinium (first and middle 4f element series).

* D is in 10^-6 cm²s^-1 , λ° is in cm²Seq^-1. Volume of OH^- is (Δv = 102 ų ) R(OH^-) hydrated = 2,9 Å

In this paper we seek to know the performance of coated tools in milling machining in alloys with high content of chromium. When machining materials with these characteristics, the tool is exposed to high temperatures. In this type of situation, the coated tool should support the emergence of thermal cracks due to the continuous cycle of heating and cooling, as well as acting as a diffusion barrier and prevent wear mechanisms such as loss of coatings and chipping.

Super duplex stainless steels are used in components for oil exploration in deep waters, the pre-salt layer, demand for materials with high resistance to hydrogen embrittlement (H₂), carbon dioxide (CO₂) and hydrogen sulfide (H₂S). Thus the use of super-duplex stainless steel is suitable for this application due to the high content of chromium and nickel, which gives the material high resistance to corrosion, suitable property requests imposed by the pre salt.

Due to the high content of chromium and nickel present in these alloys, and it is a two-phase materials, the machinability of the material is made ​​worse, especially for the low thermal conductivity of the material. Aiming at improving the machining process, this research studies the use of three coatings AlCrN, AlCrN based and AlCrN / TiSiN.

Therefore, it was necessary to characterize the tribological behavior of the coatings proposed in this research, determining the values ​​of adhesion of coatings on cemented carbide substrates, analyze the surface topography of carbide tools, before and after the deposition of coatings, determine the coefficient friction between super-duplex steel and cutting tools with and without coatings, analyze the cutting influence, fluid tribological behavior, super duplex steel and cutting tools.

The results were, difficulties in Super-duplex machining, due to the large amount of austenite, low thermal conductivity and high rates of hardening strain, thus hindering the chip formation, resulting in high temperatures. The coating showed better AlCrN based Accession, the pair AlCrN coating and stainless steel super-duplex showed the lowest friction coefficient. With the use of cutting fluid lower levels of coefficient of friction for the tribological pair.

The burr formation during machining mechanical shocks generated in tool wear caused by plastic deformation. It is recommended that the cutting speed is increased in order to obtain a higher temperature in the shear zone chip, thus improving the chip flow in the secondary tool also recommend the use of tools with a cutting edge Positive thus should reduce contact between chip and tool.

The optical constants of uranium oxides are important for many applications including those associated with its nuclear potential. Uranium forms many different oxides compositions and phases. This makes their study difficult. We used reactive DC magnetron sputtering to prepare uranium oxide thin films on silicon wafer over three thickness ranges, namely about 44nm, 114nm and 413nm. The partial pressure of oxygen (in argon) was chosen to be high, 40 to 70%, to prepare totally oxidized, what we thought to be, UO3 films. The x-ray diffraction pattern of the thickest film was somewhat ambiguous. However, both EDX and XPS showed that the ratio of oxygen to uranium in the samples was more than 3 to 1, composition approached 4 to 1. Since all uranium peroxide (UO4) samples to date have had water and in fact are said to contain hydrogen peroxide seeing such ratios in a sputtered film prepared in the absence of water was startling. We undertook additional x-ray diffraction measurements to determine the structure of this material and report the results. We also report our determination of the optical constants of this material via multiangle spectroscopic ellipsometry (Woollam M-2000). The constants of all three films had similar shapes, showing the typical dispersive behavior of a metal oxide with moderate bandgap. The n of the material started at about 1.95 in the IR (1.25 eV), rose to 2.2 at 3.1 eV- the direct band of all films studied- and fell thereafter. The imaginary index, k, which remained low in the IR and over most of the visible, began rising slowly at about 2.5 eV and steeply at 3.0 eV reaching a maximum of 0.55 at about 5.5 eV. The data suggests that the dominant bandgap material is at 2.8 eV, and that it is indirect. It resembles U03 which we previously reported.