稀土固体超强酸SO4^2—／TiO2／La^3＋催化合成丁酸丁酯

研究了以稀土固体超强酸ＳＯ４＾２－／ＴｉＯ２／Ｌａ＾３＋为催化剂,丁酸和正丁醇为原料合成丁酸丁酯,并考察了影响反应４ 因素。结果表明,醇酸物质的量比为１．８：１,催化剂用量为０．５ｇ（本酸为０．２ｍｏｌ的情况下）,带水剂甲苯为１５ｍＬ,反应时间为２．０ｈ是合成丁酸丁酯的较适宜的反应条件,酯化率达９８．６％。     

固体超强酸SO2-4/TiO2/La3+催化合成己酸乙酯

研究了以固体超强酸ＳＯ＾２－／ＴｉＯ２／Ｌａ＾３＋为催化剂,己酸和无水乙醇为原料合成己酸乙酯,并考察了影响反应的因素,结果表明,醇酸比为２．０：１,催化剂用量为０．５ｇ（己酸为０．２ｍｏｌ的情况下）,带水剂苯为１５ｍＬ,反应时间为２．０ｈ是最适宜的反应条件,酯化率达９６．８％。     

稀土固体超强酸SO42-/TiO2/La3+催化合成马来酸二戊酯

研究了以固体超强酸ＳＯ４＾２－／ＴｉＯ２／Ｌａ＾３＋为催化剂,马来酸和正戊醇为原料合成马来酸二戊酯并考察了影响反应的因素。结果表明,醇酸摩尔比为４．０：１,催化剂用量为１．０ｇ,带水剂甲苯为１５ｍＬ,反应时间为３．０ｈ是最适宜的反应条件,酯化率达９８．８％。     

稀土固体超强酸SO^2—4／TiO2／La^3＋催化合成异丁酸丁酯

研究了以稀土固体超强酸ＳＯ＾２－４／ＴｉＯ２／Ｌａ＾３＋为催化剂，异丁酸和正丁醇为原料合成异丁酸丁酯，并考察了影响反应的因素。结果表明，醇酸比为１．８１：１，催化剂用量为０．５ｇ，带水剂甲苯为１５ｍｌ，反应时间为２．０ｈ是最适宜的反应条件，酯化率达９７．２％。     

稀土固体超强酸SO^2—4／TiO2／La^3＋催化合成马来酸二丁酯

以固体超强酸ＳＯ＾２－４／ＴｉＯ２／Ｌａ＾３＋为催化剂,马来酸和正丁醇为原料合成马来酸二丁酯,考察了影响反应的因素,结果表明：ｎ（醇）：ｎ（酸）＝４．０：１,催化剂用量为１．０ｇ;带水剂甲苯为１５ｍＬ;反应时间为３．０ｈ是最的反应条件,酯化率达９７．４％。     

TiSiW12 O40/Ti2催化合成葡萄糖五丁酸酯

报道了新型催化剂ＴｉＳｉＷ１２Ｏ４０／ＴｉＯ２催化酯化合成工区２糖五丁酸酯的糖酸比、催化剂用量、反应时间、反应温度诸因素对产率的影响。实验表明：ＴｉＳｉＷ１２Ｏ４０／ＴｉＯ２是合成葡萄糖五丁酸酯的良好催化剂,最佳反应条件为：糖酸摩尔比１：６,催化剂的用量为反应物料总量的２．０％,酯化反应时间为２．０ｈ,反应温度９０￣９５℃,反应产率可达８５．４％。     

固体超强酸SO4^2—／ZrO2—TiO2催化剂的研制及其催化合成草莓酸酯的 …

选用ＳＯ４＾２－／ＭｘＯｙ型固体超强酸催化草莓酸的酯化反应,筛选出催化剂ＳＯ４＾２－／ＺｒＯ２－ＴｉＯ２,制备该催化剂的最优条件为：钛锆物质的量比为４：１,氨水调节ｐＨ值８～９,用浓度为０．５ｍｏｌ／Ｌ硫酸浸渍,马弗炉５５０℃焙烧３ｈ;使用该仙化剂合成草莓酸酯的最优酯化条件为：催化剂用量３ｇ／ｍｏｌ,酯化时间３ｈ,其催化合成草莓酯戊酯产率可达９０．８％。     

稀土改性SO^2—4／TiO2催化合成尼泊金酯

以稀土改性的固体超强酸ＳＯ＾２－４／ＴｉＯ２为催化剂，无水ＭｇＳＯ４作脱水剂，合成了尼泊金丁酯。考察了影响收率的诸因素，其最佳条件为：醇酸摩尔比为３：１，催化剂用量２０ｇ／ｍｏｌ酸，回流温度下反应３．０ｈ，收率达到９０．４％。     

稀土固体超强酸SO_4~(2-)/TiO_2/La~(3 )催化合成异丁酸丁酯

研究了以稀土固体超强酸 ＳＯ_４~（２－）／ＴｉＯ_２／Ｌａ~（３＋）为催化剂，异丁酸和正丁醇为原料合成异丁酸丁酯，并考察了影响反应的因素。结果表明，醇酸比为 １． ８∶ １，催化剂用量为 ０． ５ｇ，带水剂甲苯为 １５ｍｌ（异丁酸为 ０．２ｍｏｌ的情况下），反应时间为 ２．０ｈ是最适宜的反应条件，酯化率达９７． ２％。     

TiSiW12O40／TiO2催化合成丁酸乙酯的研究

介绍了杂多酸盐型固体超强酸ＴｉＳｉＷ１２Ｏ４０／ＴｉＯ２的制备方法。以自制的ＴｉＳｉＷ１２Ｏ４０／ＴｉＯ２为催化剂,通过正丁酸和无水醇反应合成了丁酸乙酯,并搪塞绎产率的影响。实验表明：ＴｉＳｉＷ１２Ｏ４０／ＴｉＯ２具有良好的催化活性,醇酸摩尔比为１．５：１,催化睡量为反应液总量的１．０％,酯化反应时间为１．５ｈ,反应温度为９３￣９６℃,丁酸乙酯的产率达７５．６％。     

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.     

(Bi1/2Na1/2)TiO3–Ba(Cu1/2W1/2)O3 Lead-Free Piezoelectric Ceramics

(Bi_1/2Na_1/2)TiO₃ with 0–6 mol% Ba(Cu_1/2W_1/2)O₃ (BNT-BCW), a new member of the BNT-based group, has been prepared following the conventional mixed oxide route. The compacted bodies were sintered at 1130°C for 2 h to get dense ceramics. The addition of BCW into BNT ceramics facilitated the poling process because of a reduction in leakage current. 0.995BNT·0.005BCW ceramics exhibit a relatively high piezoelectric constant ( d ₃₃= 80 × 10⁻¹² C/N) and a relatively low dielectric loss (tan δ= 1.5%). Increased amount of BCW was found to increase the dielectric constant and loss of BNT-BCW ceramics and to suppress the grain growth. During sintering, some BCW diffuses into the lattice of BNT to form a solid solution and some remains on the grain boundaries.     

炭黑/煤矸石/碳纳米管复合填料体系对天然橡胶性能的影响研究*

利用硝酸氧化法对碳纳米管(CNTs)进行纯化,并用环氧天然橡胶(ENR)进行改性处理。结合胶质量分数测定结果表明, ENR用量15%(质量)时效果最佳。采用胶乳凝聚法制备CNTs/天然橡胶(NR)母料。煤矸石粉(CG)经高温煅烧和表面改性处理。 将CNTs/天然橡胶(NR)母料、CG和炭黑(CB)通过机械混炼法与天然橡胶及配合剂混合,制备CB/CG/CNTs/NR复合材料,并对复合材料进行硫化特性及物理机械性能。结果表明： CNTs延迟硫化效应明显;相比炭黑,CG对硫化具有促进作用。硫化特性和甲苯溶胀法测定结果表明,在填料份数相同的条件下,单独由CB填充的NR有最大的交联密度,CNTs对交联密度影响不明显。物理机械性能测试结果表明,当CG：CB：CNTs=17.5:16.5:1(Phr)时,NR硫化胶的300%定伸应力和扯断伸长率明显高于单独由CB填充NR,而拉伸强度与之接近,复合填料样填充NR具有较好的综合性能。扫描电镜测试结果表明,复合填料在NR基体中分布均匀。     

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 ).