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This work proposes a new spatial reconstruction scheme in finite volume frameworks. Different from long-lasting reconstruction processes which employ high order polynomials enforced with some carefully designed limiting projections to seek stable solutions around discontinuities, the current discretized scheme employs THINC (Tangent of Hyperbola for INterface Capturing) functions with adaptive sharpness to solve both smooth and discontinuous solutions. Due to the essentially monotone and bounded properties of THINC function, difficulties to solve sharp discontinuous solutions and complexities associated with designing limiting projections can be prevented. A new simplified BVD (Boundary Variations Diminishing) algorithm, so-called adaptive THINC-BVD, is devised to reduce numerical dissipations through minimizing the total boundary variations for each cell. Verified through numerical tests, the present method is able to capture both smooth and discontinuous solutions in Euler equations for compressible gas dynamics with excellent solution quality competitive to other existing schemes. More profoundly, it provides an accurate and reliable solver for a class of reactive compressible gas flows with stiff source terms, such as the gaseous detonation waves, which are quite challenging to other high-resolution schemes. The stiff C-J detonation benchmark test reveals that the adaptive THINC-BVD scheme can accurately capture the reacting front of the gaseous detonation, while the WENO scheme with the same grid resolution generates unacceptable results. Owing also to its algorithmic simplicity, the proposed method can become as a practical and promising numerical solver for compressible gas dynamics, particularly for simulations involving strong discontinuities and reacting fronts with stiff source term.

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Copper was etched from a silicon surface using the chelator hexafluoroacetylacetone (hfacH) dissolved in supercritical carbon dioxide (scCO 2 ) at 40-60 °C and 100-250 atm. Copper was deposited on Si(100) using doped HF solutions in the form of 10-90 nm Cu islands, as shown by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) indicated the islands were composed of Cu(I) 2 O due to air exposure before etching was attempted. Oxidation of the Cu(I) was performed using aqueous 30% H 2 O 2 or a UV-Cl 2 gas phase, forming shells of Cu(II)O or Cu(II)Cl 2 , respectively, surrounding cores of Cu(I) 2 O. SEM images showed that the Cu(II)O had a flake morphology. The Cu(II) shells were removed selectively to the Cu(I) 2 O cores by processing with pure scCO 2 and rapidly releasing the system pressure (300 atm/min). Mechanical failure of the Cu(II)O and Cu(II)Cl 2 when CO 2 in stress corrosion cracks quickly expanded delaminated these layers, leaving only Cu(I) 2 O on the surface. Etching of both Cu(II) and Cu(I) was achieved when oxidized samples were processed in scCO 2 containing approximately 120 ppm of hfacH for 2 min. Nucleophilic attack of Cu(II) centers by hfacH formed copper(bis-hexafluoroacetylacetonate), Cu(hfac) 2 and water, or the monohydrate Cu(hfac) 2 ‚H 2 O, which was soluble in scCO 2 . The Cu(hfac) 2 ‚H 2 O byproduct is proposed to oxidize Cu(I) 2 O to Cu(II), allowing attack and etching by hfacH.

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