期刊文献+
共找到2篇文章
< 1 >
每页显示 20 50 100
Effects of Fe doping on ac susceptibility of Pr_(0.75)Na_(0.25)MnO_3
1
作者 李玉 程倩 +4 位作者 戚大伟 王继亮 张晶 王爽 关晶 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第11期487-492,共6页
Ac susceptibility at low temperatures of Pro.75Nao.25MnO3-xFexO3 (0 ≤ x ≤0.30) is investigated. The peak value of the real component of ac susceptibility X' at the freezing temperature Tf is suppressed with the i... Ac susceptibility at low temperatures of Pro.75Nao.25MnO3-xFexO3 (0 ≤ x ≤0.30) is investigated. The peak value of the real component of ac susceptibility X' at the freezing temperature Tf is suppressed with the increasing frequency. The peak value of X' shows a linear relation between Tf and the logarithm of the frequency ω. The normalized slope P = △Tf/Tf△lgco, which is much lower than canonical insulating spin glass systems in which 0.06 ≤ P ≤ 0,08. The peak value of the imaginary component of the ac susceptibility X" at Tf for the x= 0, 0.02, 0.30 samples increases with increasing frequency, suggesting a cluster glass ground state with a coexistence of charge-ordered phase and correlated ferromagnetic clusters in spin glass matrix. The peak value ofx" at Tf for the x = 0.10 sample decreases with increasing frequency, suggesting a phase separation ground state. The peak value of X"at Tf for the x = 0.05 sample decreases with increasing frequency for ω ≤52 Hz and increases subsequently till 701 Hz, and then decreases with further increasing frequency for ω ≥ 1501 Hz. This complex behaviour is ascribed to the competition between the effects of large and little ferromagnetic clusters in the sample. The ground state of x = 0.05 sample is a transition state from cluster glass to phase separation. 展开更多
关键词 MAGNETIZATION ac susceptibility phase separation CLUSTER-GLASS
下载PDF
Controlled/living ring-opening polymerization of ε-caprolactone catalyzed by phosphoric acid
2
作者 CHEN ChunXia XU Rong LI Bin 《Science China Chemistry》 SCIE EI CAS 2012年第7期1257-1262,共6页
The bulk ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted. 1, 1'-bi-2-Naphthol (BINOL)-based phosphoric acid was found... The bulk ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted. 1, 1'-bi-2-Naphthol (BINOL)-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃. The overall conversion to poly(ε-caprolactone) was more than 96% and poly(ε-caprolactone) with Mw of 8400 and polydispersity index of 1.13 was obtained. IH NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent. The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio. In addition, the present protocol provided an easy-to-handle, inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications. 展开更多
关键词 POLYESTER ORGANOCATALYSIS phosphoric acid controlled/living ring-opening polymerization Ε-CAPROLACTONE
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部