Thermal Decomposition in Systems of Acid Zn(II), Co(II), and Ni(II) Maleates with the Formation of Metallic Nanoparticles

Resumo

Conditions of synthesis are optimized and XRD and thermoanalytical studies are performed for normal maleate [Zn(H₂O)₂(C₄H₂O₄)] and acid maleate [Zn(H₂O)₄(C₄H₃O₄)₂], along with acid Co(II)–Zn(II), Ni(II)–Zn(II) maleates. It is shown that when solid solutions thermally decompose in acidic maleate systems, the kinetically less stable component causes the temperature of decomposition of the more stable component to fall. It is established that the solid residue of Zn(II) maleate after heating to 500°C in a He atmosphere is a composite containing Zn oxide whose reduction to metal begins at 675°C. The decomposition of [(Co_0.1Zn_0.9)(H₂O)₄(С₄H₃O₄)₂] leads to the oozing of metallic cobalt atoms embedded in the channels of the ZnO structure that act as a catalyst for the spontaneous growth of uniform carbon nanotubes on the surface of the composite. After thermal decomposition of the samples in a system of acid Ni(II) maleate–acid Zn(II) maleate, only the bimetallic phase is observed in the composites, and there is no zinc oxide.