NMR study of ammonium magnesium langbeinite.
نویسندگان
چکیده
Recent studies have shown that ammonium langbeinites have low-temperature phase transitions uncharacteristic of the rest of the langbeinite family. In this study, proton NMR spin-lattice relaxation times Ti and spin-spin relaxation times T2 for powder samples of (NH4)2Mg2(S04)s are reported in the temperature range from 77 to 373 K. The ammonium ions occupy two different kinds of sites in the crystal. The measured barrier to thermally activated ammonium reorientations is found to be 2.0 and 3.3 kcal/mol for the two sites, respectively. Additionally, there is no observable discontinuity in Tz at the reported phase transition at 161 K, in agreement with heat-capacity studies, suggesting that the transition mechanism may be dig'erent from those of most langbeinites.
منابع مشابه
Investigation of the effect of phosphate agent type on setting time, flowability, hydration and dehydration of magnesium phosphate cement.
Magnesium phosphate cements (MPC) are the most developed kind of chemically bonded ceramics which form through the reaction of magnesium oxide and soluble phosphate salts. Therefore, study of different magnesium phosphate cement systems is considered important according to the type of phosphate agent used. In this study, effect of mono-ammonium phosphate (MAP), di-ammonium phosphate (DAP), and ...
متن کاملEffect of Amino Acids on Magnesium Ammonium Phosphate Hexahydrate (Struvite) Crystallization
متن کامل
Evidence for struvite in poultry litter: effect of storage and drying.
The use of spectroscopic techniques (especially phosphorus-31 nuclear magnetic resonance [(31)P-NMR] and X-ray absorption near edge structure spectroscopy) has recently advanced the analysis of the speciation of P in poultry litter (PL) and greatly enhanced our understanding of changes in P pools in PL that receive alum (aluminum sulfate) to reduce water-soluble P and control ammonia emissions ...
متن کاملImproving methodology for the preparation of highly substituted imidazoles using nano-MgAl2O4 as catalyst under microwave irradiation
An efficient synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by one-step condensation of an aldehyde, benzil, ammonium acetate and primary amine in the presence of nanocrystalline magnesium aluminate under microwave irradiation is described. The advantages of this catalyst are including simple work-up, low cost and reusability. Compared with conventional methods, the ...
متن کاملImproving methodology for the preparation of highly substituted imidazoles using nano-MgAl2O4 as catalyst under microwave irradiation
An efficient synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by one-step condensation of an aldehyde, benzil, ammonium acetate and primary amine in the presence of nanocrystalline magnesium aluminate under microwave irradiation is described. The advantages of this catalyst are including simple work-up, low cost and reusability. Compared with conventional methods, the ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Physical review. B, Condensed matter
دوره 51 17 شماره
صفحات -
تاریخ انتشار 1995