An interfacial chemistry study of methylene diphenyl diisocyanate and tantalum for heat exchanger applications

Abstract

The interactions between oxidised tantalum and methylene diphenyl diisocyanate (MDI) have been investigated by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Thin (approximately 2 nm) and thick layers of polymeric MDI were deposited on tantalum; one set was cured at 200 C, the other dried at ambient temperature (20 C). The thick layers serve as a characteristic pMDI layer, and thin layers contain information relating to the nature of interfacial bonding. By careful fitting of the N1s region contributions relating to interfacial bonding have been established. All spectra show an N δ+ contribution indicative of acid-base bonding; in the case of the thick films, this is of an intermolecular nature whereas in the thin films, the more intense contribution is a result of such forces between pMDI and substrate. This is confirmed by ToF-SIMS. A lower binding energy component at ca 396 eV on the air-dried thin layer of pMDI is the result of a formal reaction between pMDI and tantalum yielding a nitride-like species in the N1s spectrum.

Interfacial Chemistry Investigation of Initial Fouling Conditions in Isocyanate Production: The Antifouling Performance of AISI 316L Stainless Steel

“…The N δ+ component is indicative of a combination of intermolecular forces between nitrogen-containing groups within the pMDI mixture and/or interfacial interactions between pMDI and the metal surface. Such interactions between MDI and metal surfaces have been identified previously. , …”

“…Such interactions between MDI and metal surfaces have been identified previously. 13,16 Chlorine is present across all samples at concentrations in the range of 0.7−3.8 atom %. Chloride and bound organic chlorine atoms have a large difference in binding energy (approximately 2 eV) and can be easily distinguished from one another.…”

Precise Fabrication and Manipulation of Individual Polymer Nanofibers

“…Little formation of the N–H bending feature in the range of 1580–1650 cm –1 indicates the lack of primary amine, suggesting the formation of a secondary-amine-rich polyurea structure. In addition, N 1s XPS reveals an additional feature formed with a lower binding energy upon the water treatment (Figure S11), indicating formation of amine groups within the polymerized sample. , These observations confirm an effective polymerization process and a greater formation of polyurea structures upon treatment of solidified oligomers with water. Similar results were consistently obtained across multiple samples with analysis of water-treated polymerized samples (Figure S11).…”

Niobium Carbide and Tantalum Carbide as Nitrogen Reduction Electrocatalysts: Catalytic Activity, Carbophilicity, and the Importance of Intermediate Oxidation States

“…Binding energy scales for NbC were calibrated by setting the C 1s binding energy for the carbidic feature at 282.7 eV. , For TaC, the corresponding C 1s carbide feature was set at 282.9 eV. , The spin–orbit doublet components of Nb 3d core level spectra (3d 5/2 and 3d 3/2 ) were separated by 2.75 eV. , Spectral deconvolution was carried out with a constraint of 3:2 on the 5/2:3/2 peak intensities, , with Nb 3d 7/2 binding energies as described in the literature , though allowed to vary slightly (<0.2 eV) for goodness of fit. A carbide phase C 1s binding energy of 282.9 eV was used to calibrate all the binding energies for TaC films. , The spin orbit doublet (4f 7/2 and 4f 5/2 ) of Ta 4f spectra was separated by 1.9 eV. − Spectral deconvolution was set with a constraint of 4:3 on the 7/2:5/2 peak intensities . Shirely background subtraction was applied to remove the background effect. , …”