Mo Sheet Research Articles

New unsupported [100]-oriented MoO 3 catalysts : I. Preparation and characterization

In the general frame of the structure-sensitive character of the oxidation reactions of olefins and alcohols on oxide catalysts, a new method of preparation of unsupported, [100]-oriented, MoO 3 catalysts is described. Diffraction techniques and SEM observations showed that the oxidation of Mo sheets leads to MoO 3 oxide plates with a preferential [100]orientation of the crystallites, this feature being most likely in relation with the special texture of the starting material. Moreover, evidence is presented that MoO 3 (100) planes, which are believed to be active in the mild oxidation of olefins, are actually truncated to (110), (120), or (130) surface planes. A structural model indicates that such (1k0) planes should have a dual-site character and the consequences have been discussed in relation with the mechanism of the mild oxidation of propene on MoO 3 catalysts.

Structure, properties and fracture of electron beam welds in RS-PM Al8FeMo

Electron beam welds were produced in rapidly-solidified, powder metallurgy (RS-PM) Al-8wt.%Fe-2wt.%Mo sheet using a range of energy inputs and metallurgically characterized with respect to microstructure, mechanical properties and fracture behavior. A reduction in the electron beam energy input required to produce autogenous, full-penetration welds and the associated increase in weld solidification and cooling rates were found to promote increasingly finer fusion zone microstructures comprising primary intermetallics and dendritic alpha aluminum (zone B type). Welds produced at the lowest energy inputs exhibited fusion zone hardnesses superior to that of the base metal, joint efficiencies exceeding 85% and acceptable ductilities. The use of a minimal energy input also prevented the formation of a structurally-coarsened region near the fusion boundary which served as the weak link in higher energy input weldments. Weld failure in this coarsened region was associated with delamination of the coarse intermetallic-alpha aluminum interfaces.

Relation between the optical and metallurgical properties of polished molybdenum mirrors

A study has been performed to determine the correlation among the microstructure, metallurgical processing, and optical surface finish of commercially available types of molybdenum (Mo) bar and plate and 0.5-mm thick Mo sheet. Specimens of bar and plate stock produced from low-carbon vacuum-arc-cast Mo or powder-metallurgy-processed Mo, as well as TZM (Ti-Zr-Mo) Mo alloy, were in the form of 3.86-cm diam disks. In addition, typical cross-rolled sheet specimens were produced from powder-metallurgy-processed Mo that had a very fine grain structure and a high degree of texture. Specimens were extensively characterized both optically and metallurgically. It was found that well-polished surfaces have surface topographies directly related to the microstructure and hence to the processing of the material. In sheet material having a well-developed texture, the polishability appeared to be independent of texture, and the grain size did not result in a lower scatter surface. It was concluded that the optimum type of Mo to use for smooth low-scatter mirrors is low-carbon vacuum-arc-cast plate or sheet material.

Effects of surface hardening treatments on wear resistance of Mo and TZM sheet

The advantageous mechanical properties of molybdenum and its alloys are sometimes restricted by low resistance at intermediate temperatures. New surface hardening treatments promise a solution to this problem.

Hydrogen embrittlement of molybdenum

Results of tension tests at 279$sup 0$K on fine-grained polycrystalline Mo sheet specimens are reported. It was found that under conditions of simultaneous tension testing and cathodic charging, the hydrogen is present at high fugacity at the tip of a crack or other stress concentrations. Thus hydrogen entry into the lattice in relatively high concentrations is possible at the point where it is most effective in causing fracture, the crack tip. Under these conditions, significant hydrogen embrittlement of molybdenum occurs. (auth)

Die elastische anisotropie von molybdän

The modulus of elasticity and the rigidity were determined for polycristalline Mo as well as for cross rolled Mo sheets showing a clear texture. From these last results and the value of the compressibility as measured by Bridgman the elastic constants for a Mo crystal were calculated; the result is: s 11 = 0,28 · 10 −12; s 12 = − 0,078 · 10 −12 and s 44 = 0,91 · 10 −12. For the ratio of the elastic moduli was found E 111 E 100 = 0,81 ; this is the first metal for which E 111 E 100 is found smaller than 1. For polycristalline Mo the modulus of elasticity was found 3,22 · 10 12 and the rigidity 1,16 · 10 12 dynes · cm −2. For NiFe (48% Ni) was found E 111 E 100 = 2, 17 .