GA-g-PAMPS/APT复合高吸水性树脂的合成和溶胀行为

以阿拉伯胶(GA)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、凹凸棒石黏土(APT)为原料,采用微波辐射法,通过接枝共聚合成生物质GA-g-PAMPS/APT高吸水性树脂。利用FTIR、XRD和TG分析了树脂的结构和热稳定性能,探讨了树脂在各种盐溶液和不同p H溶液中的溶胀行为,研究了树脂的溶胀速率和反复吸水性能。结果显示:GA、APT与AMPS之间发生了接枝共聚反应,w(GA)=7.5%、w(APT)=10%时树脂在去离子水和生理盐水中的最大吸水倍率分别为783 g/g和91 g/g。树脂在各种盐溶液和不同p H溶液中表现出良好的响应性和可逆性能。适量引入APT能显著提高树脂的热稳定性、溶胀速率、反复吸水性能和p H稳定性。     

AM-g-CCMC树脂的制备及其吸附性能

以交联羧甲基纤维素(CCMC)、丙烯酰胺(AM)为原料,过硫酸钾为引发剂,N,N'–亚甲基双丙烯酰胺为交联剂,通过微波辐射法制备了吸水性树脂丙烯酰胺接枝交联羧甲基纤维素(AM–g–CCMC)。研究了溶液p H值、盐溶液浓度对AM–g–CCMC树脂吸水倍率的影响;同时考察了染料p H值、吸附时间、染料浓度、吸附剂浓度对树脂吸附量[对碱性品红(BF)和亚甲基蓝(MB)]的影响。结果表明,AM–g–CCMC对去离子水和浓度为0.154 mol/L的Na Cl,Ca Cl2,Fe Cl3溶液的最大吸水倍率分别为1 735,165,82,43 g/g;在20℃,浓度0.25 g/L条件下,AM–g–CCMC对BF和MB的最大吸附量分别为370 mg/g和323.4 mg/g。同时对该树脂的循环利用性能进行了初步研究。结果表明,吸附MB的AM–g–CCMC的再生效果略好于吸附BF的树脂。     

CMS/AMPS/AM水凝胶的制备及其对亚甲基蓝的吸附

采用水溶液聚合法制备出CMS/AMPS/AM水凝胶型吸附剂。采用扫描电子显微镜、傅里叶变换红外光谱仪等对水凝胶的形貌、结构进行表征,并对水凝胶吸附阳离子染料亚甲基蓝(MB)的性能进行了研究。结果表明:CMS/AMPS/AM水凝胶对MB的吸附量随吸附时间、水凝胶加量和初始浓度增加先增加后逐渐达到平衡;吸附量随p H值的升高先增加后降低;共存离子浓度越高,吸附量越低。     

托贝莫来石改性及其对亚甲基蓝的吸附性能

对托贝莫来石(TOB)进行加热与酸化复合改性,成功制备出比表面积为570 m~2/g的酸化改性托贝莫来石(AHTOB),并用X射线衍射、N_2吸附-脱附对改性托贝莫来石进行了结构表征和表面积及孔径分析。通过静态吸附实验探讨了3种吸附剂对亚甲基蓝溶液(MB)的吸附性能,分析改性TOB对MB的吸附机制。考察了不同吸附剂及其加入量、溶液p H值、MB初始浓度、吸附时间及温度对吸附行为的影响,研究了AHTOB对MB溶液吸附的热力学和动力学行为。结果表明:对50 m L,浓度为10 mg/L的MB进行吸附,未改性TOB、热改性HTOB以及酸化改性AHTOB对MB的吸附率分别达到50、53.72%和97.35%。对于不同初始浓度的MB,TOB和HTOB的最大吸附量可达102.36 mg/g和113.80 mg/g,AHTOB的吸附量达到248.01 mg/g,经过加热与酸化复合改性的AHTOB对MB的吸附效率有了明显的提升,得到了吸附MB溶液的最佳外界条件:p H值为5～7,震荡时间为30 min,温度为20～25℃。     

托贝莫来石改性及其对亚甲基蓝的吸附性能EI北大核心CSCD

对托贝莫来石(TOB)进行加热与酸化复合改性,成功制备出比表面积为570 m^(2)/g的酸化改性托贝莫来石(AHTOB),并用X射线衍射、N2吸附-脱附对改性托贝莫来石进行了结构表征和表面积及孔径分析。通过静态吸附实验探讨了3种吸附剂对亚甲基蓝溶液(MB)的吸附性能,分析改性TOB对MB的吸附机制。考察了不同吸附剂及其加入量、溶液p H值、MB初始浓度、吸附时间及温度对吸附行为的影响,研究了AHTOB对MB溶液吸附的热力学和动力学行为。结果表明:对50 m L,浓度为10 mg/L的MB进行吸附,未改性TOB、热改性HTOB以及酸化改性AHTOB对MB的吸附率分别达到50、53.72%和97.35%。对于不同初始浓度的MB,TOB和HTOB的最大吸附量可达102.36 mg/g和113.80 mg/g,AHTOB的吸附量达到248.01 mg/g,经过加热与酸化复合改性的AHTOB对MB的吸附效率有了明显的提升,得到了吸附MB溶液的最佳外界条件:p H值为5~7,震荡时间为30 min,温度为20~25℃。     

VMT/P(AMPS-co-AA)复合高吸水树脂及其对染料吸附性能

研究了溶液p H、盐浓度对辉光放电电解等离子体引发合成的蛭石/聚(2-丙烯酰胺-2-甲基丙磺酸-co-丙烯酸)〔VMT/P(AMPS-co-AA)〕复合高吸水树脂的溶胀行为的影响,考察了染料p H、吸附时间、染料浓度等对树脂吸附量的影响,同时对树脂的吸附-解吸重复利用性能进行了测试。结果表明,VMT/P(AMPS-co-AA)具有高吸水性、p H敏感性、盐敏感性以及高吸附性。该树脂在蒸馏水中的最大溶胀率达到822.4 g/g,对阳离子染料亚甲基蓝(MB)、结晶紫(CV)和孔雀石绿(MG)的吸附量分别可达2 027.8、2 171.8和883.2 mg/g。在p H=6.5和25℃下,其对染料的吸附行为符合动力学准二级模型,该树脂还具有一定的吸附-解吸性能和重复利用性能。     

羧甲基纤维素-单宁基吸附树脂的制备及性能研究

制备了羧甲基纤维素-单宁基吸附树脂,并研究了吸附树脂对亚甲基蓝的吸附性能。羧甲基纤维素与单宁结合,通过羧甲基纤维素羧基与单宁酚羟基的协同作用,能有效提高吸附树脂对亚甲基蓝的吸附性能,最大吸附容量可达1 300 mg/g。在亚甲基蓝溶液初始质量浓度为1 000 mg/L,吸附剂投加质量浓度为1.5 g/L时,吸附树脂对亚甲基蓝的吸附率可达98%以上,且羧甲基纤维素-单宁基吸附树脂具有较好的重复使用性能。     

改性山核桃外果皮炭对碱性染料的吸附特性研究

用磷酸活化山核桃外果皮制备的生物质炭吸附剂处理碱性染料废水,研究了该吸附剂对废水中孔雀石绿(MG)和亚甲基蓝(MB)的吸附性能。结果表明,该吸附剂为高效的碱性有机染料吸附剂,当其投加量为1 g/L时,318 K条件下对初始质量浓度为300 mg/L的MG的去除率达99.20%,303 K条件下对初始质量浓度为200 mg/L的MB的去除率达98.48%;吸附动力学符合准二级动力学方程;等温吸附模型符合Langmuir方程。     

玉米淀粉/羧甲基纤维素生物复合凝胶的制备及吸附行为研究

以玉米淀粉与羧甲基纤维素（CMC）为骨架，以丙烯酸（AA）、丙烯酰胺（AM）、2-丙烯酰胺基-2-甲基丙磺酸（AMPS）为单体制备复合凝胶，对复合凝胶材料进行表征。以亚甲基蓝（MB）为吸附质，考察复合凝胶吸附剂对阳离子染料吸附过程的动力学和热力学行为，分析阳离子强度、水体pH值、染料初始质量浓度等对吸附剂吸附性能的影响。结果表明：玉米淀粉-CMC-g-AA-AM-AMPS凝胶是一种表面多孔的吸附材料，其比表面积为24.939 7 m2/g，平均吸附孔径为8.668 2 nm。凝胶对MB的吸附过程与准二级动力学模型和Langmuir模型拟合较好，属于单分子层的化学吸附。阳离子对凝胶吸附MB有明显抑制作用，抑制效果为Al3+>Ca2+>Na+。随着离子强度的增加，抑制作用越明显。在投加量为0.1 g、温度为298 K、pH值为11.0、MB初始质量浓度为2 000 mg/L条件下，吸附剂最大吸附量达到1 938.82 mg/g、去除率为96.94%，能有效去除MB。     

SMA-β-环糊精聚合物制备及其对水中亚甲基蓝的吸附性能

用β-CD与苯乙烯-马来酸酐交替共聚物(SMA)反应,制备了β-CD质量分数为49.8%的水不溶性SMA-β-CD,并用IR、元素分析及热分析表征。以SMA-β-CD为吸附剂,研究了25℃下SMA-β-CD对水中亚甲基蓝(MB)的吸附性能。结果表明,吸附性能随体系p H升高而提高,吸附在120 min内达到平衡。固液比为0.25g/L时,SMA-β-CD对20 mg/L的MB的吸附率为100%;固液比为0.5 g/L时,对213.6 mg/L的MB吸附率达98%。SMA-β-CD对MB的吸附符合Langmuir模型,由Langmuir方程求得的最大吸附量为316.4 mg/g;吸附符合拟二级动力学模型。     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

Structure Evolution from Pb(Mg1/3Nb2/3)O3 to La(Mg2/3Nb1/3)O3

The crystal structure of lanthanum-modified lead magnesium niobates having composition (Pb_{1− x} La _x ) (Mg_{(1+ x )/3}-Nb_{(2− x )/3})O₃ with X = 0 to 1 was investigated by X-ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B'_1/2-B"_1/2)O₃ ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.     

Microwave Dielectric Properties of CaTiO3-CaAl1/2Nb1/2O3 Ceramics Doped with Li3NbO4

The microwave dielectric properties of CaTi_{1− x} (Al_1/2Nb_1/2) _x O₃ solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO₃. The substitution of Ti⁴⁺ by Al³⁺/Nb⁵⁺ improved the quality factor Q of the sintered specimens. A small addition of Li₃NbO₄ (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛ_r) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −2 ppm/K. Li₃NbO₄ as a sintering additive had no harmful influence on τ_f of ceramics.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Dielectric-State Analysis in Solid-Solution Pb(Yb1/2Ta1/2)O3–Pb(Lu1/2Nb1/2)O3

The structure and temperature dependence of complex lead perovskite dielectrics were investigated for the system (1 − x )Pb(Yb_1/2Ta_1/2)O₃– x Pb(Lu_1/2Nb_1/2)O₃. Superlattice reflections for the compositions 0.8 < x < 1.0 were observed by X-ray diffractometry, and the temperature-composition dielectric-state diagram was determined. In the present study, the disordered middle composition, with 0.2 < x < 0.8, showed a diffuse paraelectric–ferroelectric phase transition, whereas the ordered end compositions, with 0 ≤ x < 0.2 and 0.8 < x ≤ 1.0, revealed successive sharp paraelectric–antiferroelectric and weak antiferroelectric–ferroelectric phase transitions. The dielectric state was confirmed by examining the variation of polarization ( P ) with electric field ( E ).