Thermal degradation of poly(acrylic acid) containing metal nitrates and the formation of YBa₂Cu₃O_7−x

Abstract

The use of polymers containing metal salts as ceramic high‐temperature superconductor (HTSC) precursors may provide a relatively simple and rapid method for producing materials that can take advantage of advanced polymer processing and then be pyrolyzed to HTSCs. The mechanisms of thermal degradation in these precursors, which have not been characterized, can be used to optimize the pyrolysis conditions for HTSC production. This article describes the degradation of a precursor based on poly(acrylic acid) (PAAc) containing yttrium, barium, and copper nitrates in the proportions needed for the formation of the HTSC YBa2Cu3O7−x (YBCO). This article also describes the effects of the pyrolysis process on the resulting materials. The degradation of the precursor is a complex, multistage process. The presence of the metal ions and HNO3 reduces the thermal stability of PAAc and increases the degradation rate. The results indicate that the initial stages of the pyrolysis should be conducted in argon or nitrogen to inhibit BaCO3 formation and that the final stages should be conducted in air/oxygen to enhance oxidation. Optimization of the pyrolysis conditions produces a YBCO film with minimal contamination. © 2005 Wiley Periodicals, Inc. J PolymSci Part B: Polym Phys 43: 1168–1176, 2005

Thermal behavior of hydrophobically modified hydrogels using TGA/FTIR/MS analysis technique

“…The presence of CO + (m/z = 28) and CH 2 ¼C¼CH + (m/z = 39) in the MS spectrum at 454 C confirmed the anhydrides decomposition and PAA chain scission in short fragments. These observations are in good agreement with thermal degradation studies on PAA-based materials given in literature [27,[31][32][33][34].…”

Nanostructured Materials Preparation via Condensation Ways

“…Thermolysis of a mixture of yttrium, barium and copper nitrates (atomic ratio 1:2:3) is known [483] to include five key stages: (1) dehydration (in the temperature range of 298-459 K with an exothermic peak at 400 K); (2) dehydration with copper denitration (in the temperature range of 459-517 K with a temperature maximum at 548 K), (3) completion of copper denitration and yttrium denitration (517-585 K), (4) final yttrium denitration (585-773 K with a maximum at 648 K) and (5) barium melting and denitration (above 773 K with an endothermic peak at 848 K). The denitration of the material reaches a maximum at 913 K, and the residual weight at 1,273 K is 41.6 %, which corresponds to the composition YBa 2 Cu 3 O 6.5 ( Fig.…”

Roles of Calcium, Zinc, Copper and Titanium Compounds on the Degradation of Polymers

“…The effects of CuN on thermal degradation of polymer have also been confirmed by Dubinsky et al [121] , who have critically investigated the thermal properties of poly(acrylic acid) (PAAc) in the presence of CuN. The weight ratio of PAAc to CuN was fixed at 2:1 and two measurements (TGA and DTA) have been adopted to study the thermal properties of composites.…”

“…As for P(AN-VA)/CuN composites, it was reported that the minima for carbonization and cyclization were almost disappeared for composite with 10 wt.% of CuN and completely disappeared for the composites with 25 and 50 wt.% of CuN. Besides, the temperature for the initiation of thermooxidative degradation has potentially been reduced when the content of CuN increased [121] . This implies that the CuN incorporated has altered the degradation mechanisms and thus enhanced the thermooxidative degradation of P(AN-VA) blends.…”

“…Degradation mechanism of PAAc: (a) Main chain scission, (b) Side group scission, which leads to the formation of CuCO 3 and CuO, and (c) Further reaction between low molecular radicals and CuO[121] …”