Crystalline neodymium carbonates were prepared by treating the amorphous precipitate formed from the reaction between neodymium chloride and ammonium bicarbonate under hydrothermal condition. Their composition, morpho...Crystalline neodymium carbonates were prepared by treating the amorphous precipitate formed from the reaction between neodymium chloride and ammonium bicarbonate under hydrothermal condition. Their composition, morphology and crystal phase were identified by means of elemental analysis, SEM and XRD. It was found that Nd2(CO3)3·2.5H2O with tengerite-type structure and sheet morphology was obtained when the feed molar ratio(FMR=n(NH4)2CO3/ NdCl3)was 2 or 1.8 and hydrothermally treated at 150 ℃ for 12h. However, orthogonal NdOHCO3 particles agglomerated with long rod crystals were formed when lowering FMR to 1.5 under the same hydrothermal condition. Phase transformation from tengerite-type Nd2(CO3)3·2.5H2O to orthogonal NdOHCO3 was occurred when increasing hydrothermal temperature or prolonging hydrothermal time, which is beneficial to the preparation of neodymium hydroxyl-carbonate with neodymium oxide content higher than 70%.展开更多
Amorphous Neodymium carbonate was prepared by the precipitation reaction of neodymium chloride with ammonium bicarbonate in solution, and then aged at 60 ℃ to form crystalline neodymium carbonate. The feed molar rati...Amorphous Neodymium carbonate was prepared by the precipitation reaction of neodymium chloride with ammonium bicarbonate in solution, and then aged at 60 ℃ to form crystalline neodymium carbonate. The feed molar ratio of nNH4HCO3/nNdCl3 was 2.5, and the precipitation was carried out with or without addition of polyglyceryl fatty acid ester (PGFAE). The phase type and morphology of crystalline neodymium carbonates were examined by XRD and SEM, and the effect of PGFAE on the crystallization speed was investigated by volume change in deposit layer and in situ pH determination. The content of neodymium and chloride in crystals was analyzed, and the crystallization reaction or crystal growth characteristics were discussed. It was found that all the crystalline neodymium carbonates were tengerite type, and contained less crystalline water and chloride than that of lanthanite type neodymium carbonate crystallized at room temperature, which is beneficial to the production of neodymium carbonate with higher neodymium and lower chloride content. The addition of PGFAE not only could eliminate the foam formed during precipitation, but also could shorten crystallization time, and form large radiative-like shape conglomeration by the irregulative linkage of one dimension needle crystals. It is also suggested that the morphology and the chloride content of neodymium carbonate were dependent on the structure and crystal growth characteristics.展开更多
文摘Crystalline neodymium carbonates were prepared by treating the amorphous precipitate formed from the reaction between neodymium chloride and ammonium bicarbonate under hydrothermal condition. Their composition, morphology and crystal phase were identified by means of elemental analysis, SEM and XRD. It was found that Nd2(CO3)3·2.5H2O with tengerite-type structure and sheet morphology was obtained when the feed molar ratio(FMR=n(NH4)2CO3/ NdCl3)was 2 or 1.8 and hydrothermally treated at 150 ℃ for 12h. However, orthogonal NdOHCO3 particles agglomerated with long rod crystals were formed when lowering FMR to 1.5 under the same hydrothermal condition. Phase transformation from tengerite-type Nd2(CO3)3·2.5H2O to orthogonal NdOHCO3 was occurred when increasing hydrothermal temperature or prolonging hydrothermal time, which is beneficial to the preparation of neodymium hydroxyl-carbonate with neodymium oxide content higher than 70%.
文摘Amorphous Neodymium carbonate was prepared by the precipitation reaction of neodymium chloride with ammonium bicarbonate in solution, and then aged at 60 ℃ to form crystalline neodymium carbonate. The feed molar ratio of nNH4HCO3/nNdCl3 was 2.5, and the precipitation was carried out with or without addition of polyglyceryl fatty acid ester (PGFAE). The phase type and morphology of crystalline neodymium carbonates were examined by XRD and SEM, and the effect of PGFAE on the crystallization speed was investigated by volume change in deposit layer and in situ pH determination. The content of neodymium and chloride in crystals was analyzed, and the crystallization reaction or crystal growth characteristics were discussed. It was found that all the crystalline neodymium carbonates were tengerite type, and contained less crystalline water and chloride than that of lanthanite type neodymium carbonate crystallized at room temperature, which is beneficial to the production of neodymium carbonate with higher neodymium and lower chloride content. The addition of PGFAE not only could eliminate the foam formed during precipitation, but also could shorten crystallization time, and form large radiative-like shape conglomeration by the irregulative linkage of one dimension needle crystals. It is also suggested that the morphology and the chloride content of neodymium carbonate were dependent on the structure and crystal growth characteristics.
