Hamid J. Jaffer

Bio: Hamid J. Jaffer is an academic researcher from University of Baghdad. The author has contributed to research in topics: Thermal decomposition & Eutectic system. The author has an hindex of 1, co-authored 2 publications receiving 10 citations.

Solid-state reactions between alkali persulfates and oxides of corundum structure

Abstract: The effects of three corundum structure oxides, α-Al 2 O 3 , α-Cr 2 O 3 , and α-Fe 2 O 3 , on the thermal decomposition of sodium and potassium peroxodisulfates (persulfates) under non-isothermal static air conditions and using various oxide/persulfate molar ratios, have been thermoanalytically investigated Compounds such as Na 3 Al(SO 4 ) 3 , K 3 Al(SO 4 ) 3 , Cr 2 (SO 4 ) 3 , K 3 Cr(SO 4 3 , and Na 3 Fe(SO 4 ) 3 are identified by X-ray diffractometry and conventional chemical analysis The molar ratios as well as temperatures of the stoichiometric formation for these compounds have been established At higher temperatures, α-Al 2 O 3 acts as a promoter catalyst for the decomposition of pyrosulfate to sulfate, whereas α-Cr 2 O 3 behaves as a retarder for the decomposition of persulfate A eutectic mixture is formed between K 3 Al(SO 4 ) and K 2 SO 4 at 675°C Also, K 3 Fe(SO 4 ) 3 is identified as two crystalline phases

Thermoanalytical behavior of cadmium(II) oxide—alkali persulfate binary systems

Abstract: The non-isothermal behavior of two binary CdO—persulfate systems has been investigated. The molar ratios and T i — T f are established. The temperatures for the α- to β-Na 2 SO 4 phase transition, as well as for α- to β- to γ-CdSO 4 of the CdONa 2 S 2 O 8 system have been fixed. No evidence for the occurrence of the β- to γ-CdSO 4 polymorphic trans-formation has been obtained from the reaction of the CdOK 2 S 2 O 8 system. This is because of the formation of a CdSO 4 /K 2 SO 4 eutectic mixture which melts at 653°C, i.e., before the β- to γ-phase change transition, which usually occurs later. No basic cadmium sulfate has been identified. The excess cadmium oxide acts as a p -type semiconductor which accelerates the thermal decomposition of pyrosulfates.

Evidence of corrosion on metallic surfaces at 500 °C and 560 °C by metal-potassium trisulphate formation in oxy-co-combustion

Abstract: This work explores potassium pyrosulphate (K2S2O7) reactivity with iron, chromium and nickel oxides as simulation of the corrosion risk caused by alkaline deposits in the oxy-fuel co-firing of coal with high KCl biomass. TGA studies confirm the formation of metallic trisulphates (K3Fe(SO4)3, K3Cr(SO4)3 and K2Ni2(SO4)3) at 500 °C and 560 °C. Selected steels and alloys (P91, 409, 304, 347, 310, I800HT and I617) were pre-oxidised in 5% O2/CO2 for 200 h and the oxidation scales were treated with K2S2O7 to study the mechanism of oxide dissolution by Fe, Cr and Ni trisulphates, and inner sulphidation.

Reactions of manganese oxides with K2S2O7

Abstract: The course of reactions of potassium disul- phate(VI) with manganese oxides: MnO, Mn2O3 and MnO2 was studied in solid phase. In the reactions all the man- ganese oxides were reduced to Mn 2? which then became a component of one of the reaction products namely K2Mn2(SO4)3. A classification scheme of the reaction path has been proposed.

On the non-isothermal behaviour of ZrO2 and HfO2Na2/K2/S2O8 binary systems

Abstract: The non-isothermal solid-state derivatographic behaviour of HfO 2 and ZrO 2 and four systems of HfO 2 and ZrO 2 Na 2 /K 2 /S 2 O 8 of various molar ratios have been investigated in a static air atmosphere from ambient temperature to 1050°C. HfO 2 gradually loses oxygen at higher temperatures yielding Hf(II)O which reoxidises to HfO 2 on cooling. No weight loss or change of valence state was observed in the case of ZrO 2 . The 1:1 ::HfO 2 (ZrO 2 ):Na 2 /K 2 /S 2 O 8 ratios were found to be stoichiometric. Accordingly, four different thermally stable basic double salts have been identified, namely, Na 2 HfO(SO 4 ) 2 , K 2 HfO(SO 4 ) 2 , Na 2 ZrO(SO 4 ) 2 and K 2 ZrO(SO 4 ) 2 . Based on the DTA curves, a mechanism for the thermal degradation of these basic salts has been proposed which shows the liability of Hf(IV) to form unstable Hf(II) at higher temperatures. All systems tend to form melting eutectic mixtures. X-ray diffractometery has been employed to identify intermediate and final products.

TG, DTG and DTA studies of PdONa2/K2/S2O8 binary reactions

Abstract: TG, DTG and DTA investigations for PdO alone and binary PdONa 2 /K 2 /S 2 O 8 mixtures of various molar ratios have been carried out derivatographically; the stoichiometric ratios have been found to be 1:1. PdO has catalytically lowered T i values of decomposition of either Na 2 S 2 O 8 or K 2 S 2 O 8 by about 20°C. In the absence of moisture PdO reacts with Na 2 S 2 O 8 at about 80°C to form brittle masses whose formula can be tentatively written as Na 4 [PdO(SO 4 )] 2 which is stable up to 155°C. Such a complex has not been detected with the PdOK 2 /S 2 O 8 system. At elevated temperatures, pyrosulfates of sodium and potassium react with PdO in the solid state yielding PdSO 4 (thermal stability 490–540°C) which subsequently decomposes into PdO and SO 3 . The eutectics (PdSO 4 + K 2 S 2 O 7 ) and (PdSO 4 + Na 2 S 2 O 7 ) have been identified. In the presence of excess Pd, partial decomposition of melting of Na 2 SO 4 occurs with the formation of Na 2 PdO 2 and SO 2 . X-ray diffractometry and IR spectrophotometry have been employed to identify intermediate and final products.