Benvenuti nell'Anagrafe della Ricerca d'Ateneo
La valutazione delle attività di ricerca che si svolgono nelle università ha assunto un'importanza rilevante sia per l'intero sistema universitario sia all'interno di ogni singolo ateneo. Roma Tre si è quindi dotata di idonei strumenti informativi in grado di supportare al meglio le azioni di monitoraggio e di valutazione delle attività di ricerca svolte nei propri dipartimentied ha realizzato una Anagrafe della Ricerca di Ateneo.
EnglishAmphiboles were hydrothermally synthesized at 500 degreesC and 4 kbar in the system Li2O-Na2O-FeO-Fe2O3-SiO2-H2O, with nominal compositions along the riebeckite [rectangleNa(2)Fe(3)(2+)Fe(2)(3+)Si(8)O(22)(OH)(2)]-ferri-clinoferroholmquistite [rectangleLi(2)Fe(3)(2+)Fe(3)(2+)Si(8)O(22)(OH)(2)] join, where the exchange vector is NaLi-1 at the B-site. Experimental products were characterized by powder XRD and SEM-EDAX, confirming very high amphibole yield along the join (>95%, plus minor quartz). The XRD patterns can be indexed in C2/m, and the refined cell parameters show linear variation as a function of composition. For the Li-B end-member, the IR spectrum shows a single sharp main band centered at 3614 cm(-1), which is assigned to the FeFeFe-OH-(Lambda)rectangle configuration. With increasing Na-B in the mineral, this band broadens and shifts 4 cm(-1) to higher frequencies. This effect can be attributed to the change in M4 site occupancy. Minor Na-A (partial solid-solution toward arfvedsonite) is also observed with increasing sodium in the system. Mossbauer spectroscopy confirms the cation distribution provided by IR data, and shows that a small, but significant amount of Fe2+ occurs at M4 along the join. Infrared spectroscopy shows that the Li end-member has a very ordered structure, whereas intermediate compositions show local heterogeneities associated with the presence of two different B sites occupied by Na or Li.
IEZZI, G., DELLA VENTURA G, CAMARA, F., PEDRAZZI, et al. (2003). The BNa- BLi exchange in A-site vacant amphiboles: synthesis and cation ordering along the ferri-clinoferroholmquistite – riebeckite join. AMERICAN MINERALOGIST, 88, 955-961.
| Titolo: | The BNa- BLi exchange in A-site vacant amphiboles: synthesis and cation ordering along the ferri-clinoferroholmquistite – riebeckite join |
| Autori: | |
| Data di pubblicazione: | 2003 |
| Rivista: | |
| Citazione: | IEZZI, G., DELLA VENTURA G, CAMARA, F., PEDRAZZI, et al. (2003). The BNa- BLi exchange in A-site vacant amphiboles: synthesis and cation ordering along the ferri-clinoferroholmquistite – riebeckite join. AMERICAN MINERALOGIST, 88, 955-961. |
| Abstract: | Amphiboles were hydrothermally synthesized at 500 degreesC and 4 kbar in the system Li2O-Na2O-FeO-Fe2O3-SiO2-H2O, with nominal compositions along the riebeckite [rectangleNa(2)Fe(3)(2+)Fe(2)(3+)Si(8)O(22)(OH)(2)]-ferri-clinoferroholmquistite [rectangleLi(2)Fe(3)(2+)Fe(3)(2+)Si(8)O(22)(OH)(2)] join, where the exchange vector is NaLi-1 at the B-site. Experimental products were characterized by powder XRD and SEM-EDAX, confirming very high amphibole yield along the join (>95%, plus minor quartz). The XRD patterns can be indexed in C2/m, and the refined cell parameters show linear variation as a function of composition. For the Li-B end-member, the IR spectrum shows a single sharp main band centered at 3614 cm(-1), which is assigned to the FeFeFe-OH-(Lambda)rectangle configuration. With increasing Na-B in the mineral, this band broadens and shifts 4 cm(-1) to higher frequencies. This effect can be attributed to the change in M4 site occupancy. Minor Na-A (partial solid-solution toward arfvedsonite) is also observed with increasing sodium in the system. Mossbauer spectroscopy confirms the cation distribution provided by IR data, and shows that a small, but significant amount of Fe2+ occurs at M4 along the join. Infrared spectroscopy shows that the Li end-member has a very ordered structure, whereas intermediate compositions show local heterogeneities associated with the presence of two different B sites occupied by Na or Li. |
| Handle: | http://hdl.handle.net/11590/134431 |
| Appare nelle tipologie: | 1.1 Articolo in rivista |
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