两种反相微乳液体系合成纳米羟基磷灰石的比较

制备了两种稳定的CTAB/正丁醇/正己烷/水体系和TritonX-100/正己醇/环己烷/水反相微乳液体系,研究了微乳液组份的浓度和比例对微乳液性质的影响,比较了两种反相微乳液体系的三元相图,用“微反应器”合成了纳米羟基磷灰石(HAP)粉体,比较了HAP颗粒在X-射线衍射、TEM、SEM表征中的异同。两种体系都表明反向微乳液法可以有效地控制和改变HAP的分散性和粒度大小。     

新型吖啶-二氧化硅荧光纳米颗粒的合成及表征

利用油包水的反相微乳液法,运用TritonX-100（曲拉通X-100）/正己醇/环己烷微乳液自组装体系,分别以吖啶、9-氨基吖啶、9-（2-氨基苯胺基）吖啶为核包覆SiO2,制备得到核壳型荧光氧化硅纳米颗粒。该方法克服了传统方法荧光试剂泄露的问题。透射电子显微镜检测和荧光光谱分析表明,所制得的纳米颗粒荧光强度高,荧光性质稳定,具有潜在生物亲和性,可望作为新型的荧光标记物。     

双微乳液法制备纳米硫酸钡颗粒

在水溶液/TritonX-100/正己醇/环己烷组成的反相微乳液中,以氯化钡和硫酸钠为原料,通过沉淀反应,制备出类球形BaSO₄纳米颗粒,并通过XRD、SEM、TEM、FTIR对其进行表征。考察了三种反应方式、水/TritonX-100摩尔比（R）、反应物浓度以及助表面活性剂/表面活性剂摩尔比（P）对纳米BaSO₄颗粒大小和形貌的影响。同时考察了R对微乳液液滴大小和粒径分布的影响,并通过动态光散射技术（DLS）对微乳液液滴进行测定。实验结果表明：室温条件下,采用双微乳液法,R=17.97,P在2.11～4.22之间是纳米BaSO₄颗粒合成的最佳反应条件,反应物浓度对BaSO₄颗粒的大小和形貌几乎没有影响。在该反应条件下,合成出的类球形BaSO₄粒径为18～22 nm,产率可达87.5%。     

CTAB/正丁醇/正己烷反相微乳液体系合成纳米羟基磷灰石的工艺探讨

利用一种新型的微乳液法制备了纳米羟基磷灰石,确定了稳定的CTAB/正丁醇/正己烷/水四元反相微乳液体系,研究了影响微乳液法制取纳米羟基磷灰石的最佳pH值和煅烧温度等工艺条件.x-射线衍射仪、TEM、SEM和IR对羟基磷灰石颗粒进行表征和分析结果表明：颗粒分散均匀,呈球形,粒度为30m左右,此方法可以有效地控制和改变HAP的分散性和粒度大小.     

反相微乳液法制备钛酸钡纳米棒的形貌控制

采用水/辛基酚聚氧乙烯(10)醚/正己醇/环己烷反相微乳液体系,制备了钛酸钡(BaTiO3)纳米棒.研究了微乳液体系中水与表面活性剂的摩尔比、反应物浓度及陈化时间对纳米棒尺寸和形貌的影响.用透射电子显微镜、X射线衍射仪表征样品的形貌和结构.结果表明:所得BaTiO3纳米棒直径约10～60 nm、长约260～1 200 nm,为单一立方相.经电感耦合等离子体发射光谱仪分析,产品中钡与钛的摩尔比为1.0.     

反相微乳法制备纳米ZrO2前躯体溶液微观结构的研究

本文通过拟三元相图法、电导法和红外光谱法对CTAB/正己醇/环己烷/水形成的四元反相微乳液体系的微观结构进行了研究,进而确定用于制备纳米ZrO2的最佳反相微乳液体系。     

表面活性剂含量对微乳液法合成纳米氧化锆粉体结构与性能的影响

采用水/环己烷/TritonX-100/正己醇四元油包水体系,通过微乳液法制备了纳米ZrO2粉体.用X射线衍射、透射电镜等表征所制备的纳米粉体,重点研究表面活性剂含量对ZrO2纳米粒子结构与性能的影响,分析产生团聚的原因,并提出改进措施.结果表明:所制备的纳米单斜相ZrO2粉体的晶粒尺寸可控制在15nm左右;随表面活性剂含量的增加,晶粒的尺寸有所减小,团聚现象亦有所减少.     

溶胶-反相微乳液体系制备粒径可控的纳米CeO2

以环己烷/H_2O/CTAB/正丁醇形成的反相微乳液体系为反应介质,其中,水相为调节Ce(NO_3)_3溶液pH值形成的溶胶,研究了Ce(NO_3)_3浓度、溶胶和反相微乳液体系的温度、反相微乳液体系pH值对CeO_2粒径的影响,并用XRD、激光粒度仪对样品进行了表征。结果表明,可以在1～100 nm内制备出粒径可控的CeO_2颗粒。控制Ce(NO_3)_3浓度为1.2 mol/L、溶胶和反相微乳液体系的温度为25℃、反相微乳液体系pH值为8,可得到D_(90)粒径在25～45 nm的CeO_2颗粒。     

微乳液法制备无定形纳米二氧化硅

采用Triton X-100／正己醇／环己烷／氨水体系配制反相微乳液，在碱性条件下正硅酸乙酯在反相微乳液中发生受控水解，合成了具有无定形结构的球形二氧化硅纳米粒子。通过红外光谱（FT-IR）、X衍射（XRD）、透射电镜（TEM）分别对样品的结构及形貌尺寸进行了表征和分析。结果表明：改变表面活性剂加入量可以得到不同粒径（50～110nm）、不同粒度分布及不同分散程度的球形二氧化硅纳米粒子。随着表面活性剂在微乳液中体积分数的增大，二氧化硅纳米粒子的粒径先减小后增大，团聚程度也呈现先减小后增大的趋势。当表面活性剂在微乳液体系中的体积分数为20％时，所合成的二氧化硅纳米粒子粒径最小（50nm），粒度均匀且呈现出良好的分散性。     

反相微乳液合成纳米羟基磷灰石的新方法

利用一种新型的微乳液法制备了纳米羟基磷灰石,确定了稳定的CTAB/正丁醇/正己烷/水四元反相微乳液体系,研究了不同浓度CTAB和正丁醇对微乳液体系的影响,探索了反应的最佳条件.X射线衍射仪、TEM、SEM和IR对合成的粉体表征和分析结果表明:颗粒分散均匀,呈球形,粒度为30nm左右,这种新方法可以有效地控制和改变HAP的分散性和粒度大小.     

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.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

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.     

(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.     

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.     

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。