Effect of Magnesium Addition on the Cell Structure of Foams Produced From Re-melted Aluminum Alloy Scrap

Closed-cell foams were produced from re-melted aluminum alloy scrap that contained 0.13 wt pct Mg magnesium in the as-received state and higher levels after adding 1, 2, or 5 wt pct Mg. The excess Mg gave rise to the fragmentation of long oxide filaments present in the scrap alloy into smaller filaments and improved its distribution and wetting by the Al matrix. Foaming the re-melted scrap alloy containing 1, 2, and 5 wt pct Mg excess showed stability and good expansion in comparison to the scrap alloy containing 0.13 wt pct Mg only, but the cells became non-equiaxed when the Mg concentration was high (≥2 wt pct excess) due to cell wall rupture during solidification. Compressibility and energy absorption behavior were studied for scrap alloy foams containing 1 wt pct Mg excess, which is the optimum level to obtain good expansion, stability, and uniform cell size. Foams with densities in the range of 0.2 to 0.4 g cm−1 produced by holding at the foaming temperature for different times were used for the investigation. A uniform cell structure led to flatter stress plateaus, higher energy absorption efficiencies, and reduced “knockdown” in strength compared with commercial foams made by gas bubbling. The mechanical performance found is comparable to that of commercial foams made by a similar method but the expected costs are lower

Remarkable acid strength of ammonium ions in zeolites: FTIR study of low-temperature CO adsorption on NH4FER

FTIR spectra of CO adsorbed at 100 K reveal remarkable acid strength of the free NH groups of tridentate ammonium ions in NH4FER zeolite.</p

An advanced approach for measuring acidity of hydroxyls in confined space: a FTIR study of low-temperature CO and 15 N 2 adsorption on MOF samples from the MIL-53(Al) series

Accessed by 10/2015International audienc

Adsorption of CO2 on MIL-53(Al): FTIR evidence of the formation of dimeric CO2 species

FTIR spectra of 12CO2 and 12CO2 + 13CO2 mixtures adsorbed on MIL-53(Al) reveal the formation of highly symmetric dimeric (CO2)2 species connected to two structural OH groups

Adsorption of CO\u3csub\u3e2\u3c/sub\u3e on MIL-53(Al):FTIR evidence of the formation of dimeric CO\u3csub\u3e2\u3c/sub\u3e species

\u3cp\u3eFTIR spectra of \u3csup\u3e12\u3c/sup\u3eCO\u3csub\u3e2\u3c/sub\u3e and \u3csup\u3e12\u3c/sup\u3eCO\u3csub\u3e2\u3c/sub\u3e + \u3csup\u3e13\u3c/sup\u3eCO\u3csub\u3e2\u3c/sub\u3e mixtures adsorbed on MIL-53(Al) reveal the formation of highly symmetric dimeric (CO\u3csub\u3e2\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e species connected to two structural OH groups.\u3c/p\u3

Adsorption Forms of CO₂ on MIL-53(Al) and NH₂-MIL-53(Al) As Revealed by FTIR Spectroscopy

Adsorption of CO2 on MIL-53(Al) and NH2-MIL-53(Al) has been studied by Fourier transform infrared (FTIR) spectroscopy at different temperatures and equilibrium pressures. For better interpretation of the spectra 13CO2 was also utilized. It is established that with both samples at low coverages CO2 forms O-bonded complexes with the structural OH groups (OH⋯O12CO). These species are characterized by μ3(12CO2) at 2337-2338 cm-1 and two μ2(12CO2) modes around 662 and 650 cm-1. Simultaneously, the μ(OH) modes of the hydroxyl groups are red-shifted, while the δ(OH) modes are blue-shifted. At higher coverages (OH⋯O12CO)2 dimeric species are formed and this leads to a decrease of the μ3(CO2) frequency by 2-4 cm-1. This change is due to vibrational interaction as proven by the observation that the frequency remains practically unaffected for (OH⋯O12CO) (OH⋯O13CO) dimeric species. Interaction between dimers leads to additional slight decrease of the value of μ3(CO2). In parallel with the CO2 adsorption a partial transformation of the material from large-pore to narrow-pore form occurs. Far before CO2 interacts with all hydroxyl groups, polymeric CO2 species are produced within the MIL-53(Al) sample. They are characterized by a split μ3(CO2) mode with a pronounced component at 2340 cm-1. The formation of these species involves some of the dimers and is accompanied by a reopening of the MIL-53 structure. Analysis of the shift of the OH modes led to the conclusion that the polymeric moiety interacts strongly with one OH group and more weakly with several other hydroxyls. No polymeric species were observed with the NH2-MIL-53(Al) sample which is associated with the more stable narrow-pore structure of this material. However, evidence of interaction between CO2 and the hydroxyls H-bonded to amino groups was found.ChemE/Catalysis Engineerin