New Approaches to Waterproofing of Space Shuttle Insulating Materials

Future reusable space vehicles will be in service much more frequently than current space shuttles. Therefore, rapid reconditioning of spacecraft will be required. Currently, the waterproofing of space shuttles after each re-entry takes 72 hours and requires substantial labor. In addition, the currently used waterproofing reagent, DiMethylEthoxySilane (DMES), is considered toxic, and ethanol fumes are released during its hydrolytic activation. Consequently, a long time period, which is not acceptable for future operations, is needed to ensure that 0 the excess volatile compounds are removed before further maintenance of the space vehicle can be performed. The objective of this project was to assist NASA Ames in finding improved waterproofing systems by identifying suitable waterproofing agents that can be applied by vapor phase deposition and will be less toxic, bond more rapidly to the insulation material surface, and potentially have higher thermal stability than the DMES system. Several approaches to achieve faster waterproofing with less toxicity were assessed using the following alternatives: Reactive volatile compounds that are rapidly deposited by chemical bonding at the surface and leave no toxic volatiles. Reactive reagents that are the least toxic. Nonvolatile reagents that are very reactive and bond strongly to the insulating material surface. Three specific types of potential reagents were chosen for evaluation in this project: 1. Volatile reagents with Si-Cl functional groups for vapor deposition 2. Volatile reagents with Si-H functional groups for vapor deposition 3. Nonvolatile oligomeric or polymeric reactive siloxanes that are assumed to have higher thermal stability and/or strong bonding to the insulating material. The chemistry involved in the project was targeted at the generation of intermediates having reactive Si-OH bonds for the formation of either volatile species or polymeric species that bond rapidly to the surface and also cure rapidly. We focused on two chemical reactions@-hydrolysis of Si-Cl bonds and catalytic dehydrocoupling of Si-H bonds

Novel polysiloxane and polycarbosilane aerogels via hydrosilylation of preceramic polymers

We report new polysiloxane and polycarbosilane aerogels, which have been obtained by crosslinking Si–H-containing polymers with a CC-containing crosslinker via hydrosilylation reactions. The crosslinking reaction has been carried out in a highly diluted solution using up to 97 vol% of solvent. The obtained aerogels have a colloidal structure with meso- and macropores. Density as low as 0.17 g cm−3 has been reached, which implies a porosity of ca. 84 vol%

The Standard Model from a New Phase Transition on the Lattice

Several years ago it was conjectured in the so-called Roma Approach, that gauge fixing is an essential ingredient in the lattice formulation of chiral gauge theories. In this paper we discuss in detail how the gauge-fixing approach may be realized. As in the usual (gauge invariant) lattice formulation, the continuum limit corresponds to a gaussian fixed point, that now controls both the transversal and the longitudinal modes of the gauge field. A key role is played by a new phase transition separating a conventional Higgs or Higgs-confinement phase, from a phase with broken rotational invariance. In the continuum limit we expect to find a scaling region, where the lattice correlators reproduce the euclidean correlation functions of the target (chiral) gauge theory, in the corresponding continuum gauge.Comment: 16 pages, revtex, one figure. Clarifications made, mainly in sections 3 and 6 that deal with the fermion action, to appear in Phys Rev

A silicate weathering mechanism linking increases in marine 87Sr/ 86Sr with global glaciation

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155795/1/Blum_Erel_1995_Silicate_weathering.pd

Rb-Sr isotope systematics of a granitic soil chronosequence: The importance of biotite weathering

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155801/1/Blum_et_al_1997_Rb-Sr_isotope.pd

The coupled release of REE and Pb to the soil labile pool with time by weathering of accessory phases, Wind River Mountains, WY

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155685/1/Harlavan_et_al_2009_Coupled_release.pd

Lead isotope systematics of granitoid weathering

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155787/1/Erel_et_al_1994_Lead_isotope.pd

87Sr/86Sr ratios of sierra Nevada stream waters: Implications for relative mineral weathering rates

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155786/1/Blum_et_al_1994_87Sr_86Sr_ratios.pd

Systematic Changes in Lead Isotopic Composition with Soil Age in Glacial Granitic Terrains

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155812/1/Harlavan_et_al_1998_Systematic_changes.pd

Lead and strontium isotopes as monitors of experimental granitoid mineral dissolution

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155852/1/Erel_et_al_2004_Lead_and_strontium.pd