用固体核磁共振技术研究了CeO2-γ-Al2O3混合体系中CeO2和γ-Al2O3两相间的相互作用.在混合物的27Al MAS NMR中,除了四配位和六配位的Al位外,有一个尖锐的位于37处的峰,这个峰在高场处有一宽的肩峰.实验证实:位于高场的宽峰来自于γ-Al...用固体核磁共振技术研究了CeO2-γ-Al2O3混合体系中CeO2和γ-Al2O3两相间的相互作用.在混合物的27Al MAS NMR中,除了四配位和六配位的Al位外,有一个尖锐的位于37处的峰,这个峰在高场处有一宽的肩峰.实验证实:位于高场的宽峰来自于γ-Al2O3中的五配位Al ,而位于37处的尖峰则是由CeO2和γ-Al2O3两相间的相互作用产生的,即Al取代了CeO2晶格中八配位的Ce .定量研究表明,这种Al取代的量是极其有限的,整个CeO2晶格只有1 %的Ce能被Al取代.展开更多
^27Al,^29Si MAS NMR studies of kaolinite and its thermal transformation products show that in the kaolinite-mullite reaction series there is an extensive segregation of Al2O3 and SiO2 and the reaction of Al2O3 with Si...^27Al,^29Si MAS NMR studies of kaolinite and its thermal transformation products show that in the kaolinite-mullite reaction series there is an extensive segregation of Al2O3 and SiO2 and the reaction of Al2O3 with SiO2 to form mullite is the main path of mullite formation.At about 850°C,the peak intensity of Al(V) reaches its maximum and with the further rise of temperature the Al(V)signal completely disappears.At about 950°C,γ-Al2O3 accounts for about 71%of the material phases containing Al atoms.In the series there is no obvious presence of Al-Si spinel.The ^27Al and ^29Si MAS NMR spectra show that there is an obvious difference between the temperature points for Al-O2(OH)4 octahedral sheet collapsing and Si-O4 tetrahedral sheet breaking down.展开更多
文摘^27Al,^29Si MAS NMR studies of kaolinite and its thermal transformation products show that in the kaolinite-mullite reaction series there is an extensive segregation of Al2O3 and SiO2 and the reaction of Al2O3 with SiO2 to form mullite is the main path of mullite formation.At about 850°C,the peak intensity of Al(V) reaches its maximum and with the further rise of temperature the Al(V)signal completely disappears.At about 950°C,γ-Al2O3 accounts for about 71%of the material phases containing Al atoms.In the series there is no obvious presence of Al-Si spinel.The ^27Al and ^29Si MAS NMR spectra show that there is an obvious difference between the temperature points for Al-O2(OH)4 octahedral sheet collapsing and Si-O4 tetrahedral sheet breaking down.
