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1.
Thermogravimetric analysis is used to determine the amounts of Mg(OH)2 and Mg(CH3COO)2in a mixture thereof. The application and suitability of different analysis methods are discussed. In the first method the
mass losses in the temperature ranges as indicated by the decomposition of the pure compounds were used. Results obtained
using these temperature ranges were unusable. The percentage mass losses due to the decomposition of Mg(OH)2 and Mg(CH3COO)2 were then determined in a second method using the minimum in the derivative mass vs. temperature curves. The results obtained
by this method compared well with the actual values for mixtures containing more than 15% magnesium acetate. The third method
employed the total experimental mass loss of both decomposition reactions. The results obtained using this method compared
well to the actual values, giving a R
2 value of more than 0.99. This method of using the total mass losses can however only be used for binary mixtures that consist
only of magnesium hydroxide and magnesium acetate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
The effect of calcining conditions on the rehydration of dead burnt magnesium oxide using magnesium acetate as a hydrating agent 总被引:1,自引:0,他引:1
C. A. Strydom E. M. van der Merwe M. E. Aphane 《Journal of Thermal Analysis and Calorimetry》2005,80(3):659-662
Summary Magnesium oxide was produced through calcination of magnesite ore. A rehydration percentage of MgO to Mg(OH)2 of higher than 60% is obtained using calcination temperatures of 1000°C and below. At these temperatures medium reactive MgO was formed. The extend to which dead burnt MgO (obtained after calcination at 1200°C and higher) may be rehydrated is dependent on the calcination time, but even after 1 h and using magnesium acetate as a hydrating agent only 40% of the initial product has rehydrated to Mg(OH)2. After 4 and more hours of calcinations at 1200°C, a maximum of approximately 14% of the initial MgO is rehydrated back to Mg(OH)2. Thermogravimetric analysis was performed on the various compounds to determine the amounts of Mg(OH)2 that formed. 相似文献
3.
A. Coetzee M. E. Brown D. J. Eve C. A. Strydom 《Journal of Thermal Analysis and Calorimetry》1994,41(2-3):357-385
Both isothermal and programmed temperature experiments have been used to obtain kinetic parameters for the dehydrations and
the decompositions in nitrogen of the mixed metal oxalates: FeCu(ox)2·3H2O, CoCu(ox)2·3H2O and NiCu(ox)2·3.5H2O, [ox=C2O4]. Results are compared with those reported for the thermal decompositions of the individual metal oxalates, Cuox, Coox·2H2O, Niox·2H2O and Feox·2H2O. X-ray photoelectron spectroscopy (XPS) was also used to examinee the individual and the mixed oxalates.
Dehydrations of the mixed oxalates were mainly deceleratory processes with activation energies (80 to 90 kJ·mol−1), similar to those reported for the individual hydrated oxalates. Temperature ranges for dehydration were broadly similar
for all the hydrates studied here (130 to 180°C).
Decompositions of the mixed oxalates were all complex endothermic processes with no obvious resemblance to the exothermic
reaction of Cuox, or the reactions of physical mixtures of the corresponding individual oxalates.
The order of decreasing stability, as indicated by the temperature ranges giving comparable decomposition rates, was NiCu(ox)2>CoCu(ox)2>FeCu(ox)2, which also corresponds to the order of increasing covalency of the Cu−O bonds as shown by XPS.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献
4.
S. Paschen M. Müller J. Custers M. Kriegisch A. Prokofiev G. Hilscher W. Steiner A. Pikul F. Steglich A.M. Strydom 《Journal of magnetism and magnetic materials》2007
The cage compound Ce3Pd20Si6 has recently been shown to undergo two successive low-temperature phase transitions which are strongly affected by an applied magnetic field. Here we show that, as the lower, probably antiferromagnetic transition is suppressed to zero in a field slightly above 1 T, the electrical resistivity shows a non-Fermi-liquid-like linear-in-T temperature dependence while it follows the usual Fermi liquid T2 temperature dependence both at smaller and larger fields. This suggests that a field-induced quantum critical point exists in Ce3Pd20Si6. 相似文献
5.
A. M. Strydom 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(1):9-18
A variety of physical properties measured on the hexagonal rare-earth intermetallic compound PrCuSi are presented. We provide
compelling evidence for antiferromagnetic ordering at TN = 5.1 K in this compound, in contrast to the former claim of ferromagnetic ordering at 14 K. The antiferromagnetic order
is, however, found to be unstable in applied magnetic fields, becoming ferromagnetic beyond a metamagnetic transition at a
field of 0.7 T at 2 K. It is argued that the magnetism in PrCuSi has the ingredients of a tricritical phase transition at
the intersection of paramagnetism, ferromagnetism, and antiferromagnetism. 相似文献
6.
7.
The rehydration characteristics of a commercially produced hydromagnesite and two basic magnesium carbonates synthetically
produced from Mg(OH)2, are presented. The products were dehydrated and dehydroxylated at 325°C before rehydration was attempted. DTA and FT-IR
were used to follow the structural changes that occurred during the rehydration processes. The results obtained for the commercially
and synthetically produced hydromagnesite products indicated that the original symmetry of the groups was reclaimed during
rehydration. This was not observed for the synthetically produced unidentified basic magnesium carbonate product. This investigation
provides insight into the rehydration characteristics of a select group of basic magnesium carbonates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
9.
Uwaoma R. C. Strydom C. A. Bunt J. R. Okolo G. N. Matjie R. H. 《Journal of Thermal Analysis and Calorimetry》2019,135(5):2723-2732
Journal of Thermal Analysis and Calorimetry - The possible catalytic effect of a 5% loading by mass of crystallized salt from spent Benfield solution (SBFS) was investigated and compared with the... 相似文献
10.
H. GaviB.D. Ngom A.C. BeyeA.M. Strydom V.V. Srinivasu M. ChakerN. Manyala 《Journal of magnetism and magnetic materials》2012,324(6):1172-1176
Low field microwave absorption (LFMA) measurements at 9.4 GHz (X-band), were carried out on pulse laser deposited (PLD) polycrystalline B20 cubic structure FeSi thin film grown on Si (111) substrate. The LFMA properties of the films were investigated as a function of DC field, temperature, microwave power and the orientation of DC field with respect to the film surface. The LFMA signal is very strong when the DC field is parallel to the film surface and vanishes at higher angles. The LFMA signal strength increases as the microwave power is increased. The LFMA signal disappears around 340 K, which can be attributed to the disappearance of ferromagnetic state well above room temperature in these films. We believe that domain structure evolution in low fields, which in turn modifies the low field permeability as well as the anisotropy, could be the origin of the LFMA observed in these films. The observation of LFMA opens the possibility of the FeSi films to be used as low magnetic field sensors in the microwave and rf frequency regions. 相似文献