FeO-Fe2O3-CaO-SiO2体系铁磁微晶玻璃的磁性及生物活性

具有生物活性和磁性的微晶玻璃材料被认为是温热疗法治疗癌症的有效热种子材料.本文制备了添加少量B2O3和P2O5后的FeO-Fe2O3-CaO-SiO2体系铁磁微晶玻璃,并进行了微观结构分析、XRD分析、磁性检测以及生理模拟液的浸泡实验.实验结果表明,制备的微晶玻璃材料同时具备磁性和生物活性这两种重要性能.不经过核化处理在1000℃晶化2h能够获得较理想的磁铁矿主晶相和硅灰石次晶相均匀致密分布的微观组织,所得微晶玻璃具有最佳的磁性能.铁含量提高能够增加微晶玻璃的磁性,然而会抑制微晶玻璃表面羟基磷灰石的形成,从而降低其生物活性.     

La(Mg1/2Ti1/2)O3粉末的EDTA凝胶燃烧法合成研究

利用EDTA凝胶燃烧方法直接合成了单相的La(Mg1/2Ti1/2)O3粉末.通过调整La(NO3)3,Mg(NO3)2·6H2O,Ti(OC4H9)4和EDTA的溶液的pH值,获得了透明的凝胶.在250℃加热时,凝胶燃烧,直接转化为含少量炭化物的La(Mg1/2Ti1/2)O3粉末.利用XRD、FT-IR,SEM和激光粒径分析等技术表征了获得的粉末.     

碳热还原协同溶胶-凝胶法合成纳米ZrB2粉末

利用ZrO2-B2O3-C反应体系碳热还原的基本原理,分别使用正丙醇锆(Zr(OC3H7)4)、硼酸(H3BO3)和蔗糖(C12H22O11)为原料,采用溶胶-凝胶-碳热还原法合成了二硼化锆(ZrB2)纳米粉末。我们首先使用络合剂醋酸(AcOH)修饰Zr(OC3H7)4,以防止Zr(OC3H7)4的快速水解;其次,选用蔗糖作为碳源,是考虑到蔗糖热解时可以完全分解为碳,这样可以准确计算热解过程碳的生成量。此外,研究了凝胶温度对ZrB2纳米粉末形貌的影响。结果表明:当起始原料B/Zr(mol.)=2.3、热解温度为1 550℃时,通过碳热还原协同溶胶-凝胶法成功合成了单相ZrB2纳米粉末;当凝胶温度分别为65、75和85℃时,ZrB2纳米粉末形貌从球状演变为链状,最后生长为棒状,生长机理为定向吸附。     

溶胶-凝胶法制备0.1BiFeO3-0.9SrBi2Nb2O9铁电薄膜的结构和光学性质研究

采用硝酸铋[Bi(NO3)3·5H2O]、硝酸锶[Sr(NO3)2]、硝酸铁[Fe(NO3)3·9H2O]和乙醇铌[Nb(OC2H5)5]作为起始原料,乙二醇甲醚[C3H8O2]作为溶剂配制掺Fe的SrBi2Nb2O9前驱体溶液,利用溶胶-凝胶法在石英衬底上制备出0.1BiFeO3-0.9SrBi2Nb2O9铁电薄膜.研究了该薄膜的表面形貌、组分、晶体结构和光学性质.结果表明,经400℃退火后薄膜为非晶结构,而在空气中经600℃退火1h后,沉积的薄膜晶化成钙钛矿结构.制备的薄膜表面平整,颗粒分布均匀,表现出良好的光透过性,该薄膜的光学能隙大约为2.5eV.     

CaO-P2O5-SiO2溶胶凝胶玻璃在模拟体液中HCA层形成的研究

采用溶胶凝胶法制备了高硅含量的CaO-P2O5-SiO2系统玻璃.组成范围为(mol%)CaO13～18,P2O5 3～6,SiO2 78～83.样品采用体外溶液实验(in vitro)方法,在模拟体液(SBF)内浸泡不同时间.通过测定样品在SBF浸泡不同时间的溶液pH值变化,并对样品采用XRD、SEM等测试技术,研究了样品表面碳酸羟基磷灰石(HCA)层的形成机理及形貌变化.结果表明SiO2含量达78～83 mol%时玻璃仍具有很高的生物活性.玻璃表面在SBF中24 h内已开始形成HCA层,第3天已呈稳定态并布满整个表面,浸泡10d后的HCA由粒径在0.5～2.0 μm的球形颗粒构成.球形颗粒是纳米级HCA微晶聚集而成的多晶体.     

ZnO-B_2O_3-P_2O_5无铅玻璃结构的红外光谱研究

借助于红外光谱研究了ZnO-B2O3-PzO5磷酸盐玻璃的结构,分别讨论了玻璃中B2O3/ZnO组成的变化和P2O5/ZnO组成的变化对磷酸盐玻璃结构的影响.结果表明:玻璃中硼氧三角体[BO3]随B2O3含量的增加而增多,而硼氧四面体[BO4]减少,当B2O3≥30%(摩尔含量)时,[BO3]急剧增多,导致玻璃的化学稳定性先缓慢下降后急剧下降;随P2O5含量的增加,[BO3]减少而[BO4]增加,当P2O5≥45%(摩尔含量)时,玻璃中的B3+主要以硼氧四面体[BO4]的形式存在.     

Li2O含量对碲系玻璃温度及析晶性能的影响

通过DTA研究了TeO2-PbO-B2O3-Bi2O3-Li2O系统玻璃中TeO2、PbO物质的量比变化对玻璃转变温度(Tg)的影响,重点研究了n(TeO2)∶n(PbO)=2∶1条件下Li2O含量对玻璃转变温度的影响,并采用IR和XRD对玻璃的结构和析晶性进行了分析。结果表明:随着Li2O含量(2.7%~6.6%,摩尔分数)的增加,Tg呈N型变化趋势,当Li2O为2.7%(摩尔分数)时,Tg为最低值(300℃)。碲系统玻璃中形成了[TeO4]三角双锥体结构,它与[BO4]、[BiO6]等多面体共同构成了玻璃的三维网络结构,该玻璃经热处理后易形成Bi2TeO5晶体而会影响Tg。     

PbBr2-PbF2-P2O5玻璃的结构研究

采用红外光谱（IR）和X射线光电子能谱（XPS）等方法研究了PbBr2-PbF2-P2O5系铅卤磷酸盐玻璃的结构。结果表明，Pb^2 离子在玻璃中起着网络修饰阳离子和网络形成体的双重作用。当P2O5含量为60mol%时，Pb^2 离子主要是作为网络修饰体；当P2O5含量降低到50mol%时，一部分Pb^2 离子能够进入玻璃网络形成[PbO4]四面体或P－O－Pb键。Br^-和F^-离子达到一定浓度时就会进入玻璃网络，形成[PO4-nXn](X=Br或F，n=0-4)四面体使磷酸盐链长变短。玻璃中P2O5的含量不变时P－O－P键的比例也基本保持不变；当P2O5的含量降低时，P－O－P键和P－O^-键的含量都减少，P－O－Pb键的含量则明显增加。     

成分对烧结BAS(BaAl2Si2O8)凝胶玻璃形成的影响

采用XRD、SEM和拉曼光谱研究了溶胶一凝胶法制备的接近钡长石化学计量成分的Ba0．Al2O3-SiO2系烧结玻璃形成趋势。结果表明，在本实验条件下，SiO2含量高和BaO／Al2O3比值大，有助于形成玻璃。BaO／SiO2比值大，形成[AlO4]四配位结构的A12O3含量高。BaO／Al2O3与[AlO4]／Al^3 的关系近似线性关系。建立了一个烧结BAS凝胶玻璃形成的判别式，计算了在实验成分范围内，玻璃形成区与析晶区的边界线。根据判别式得到的计算结果与实验结果相符。     

ZnO-Al2O3-P2O5玻璃水化过程及机理的研究

研究了不同Al2O3/P2O3摩尔比和热历史的ZnO-Al2O3-P2O5玻璃在不同条件下的水化过程,利用XRD对部分水化过程的水化产物进行了晶相分析,探讨了其水化机理.结果表明:Al2O3/P2Os比的增加及退火均可降低ZnO-Al2O3-P2O5玻璃的水化速率;玻璃的水化累计失重量均与水化时间成线性关系,水失重百分数随着水化温度的提高,呈指数规律增加.研究认为:ZnO-Al2O3-P2O5玻璃的水化过程受表面水化层与内部未水化部分间的界面化学反应控制,水化过程中玻璃网络解体,相继生成了[P2O7]4-和白色不溶性物质Zn2P2O7·3H2O.     

Varistor properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics

The varistor properties of the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃-In₂O₃ ceramics were investigated for different concentrations of In₂O₃. The increase of In₂O₃ concentration slightly increased the sintered density (5.60-5.63 g/cm³) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In₂O₃. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In₂O₃ acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 10¹⁷ to 0.24 × 10¹⁷/cm³ with increasing concentration of In₂O₃.     

Nanocrystallization of SrBi2Nb2O9 from glasses in the system Li2B4O7---SrO---Bi2O3---Nb2O5

Transparent glasses in the system (100−x)Li₂B₄O₇–x(SrO---Bi₂O₃---Nb₂O₅) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi₂Nb₂O₉ (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (_r) and the loss factor (D) for the lithium borate, Li₂B₄O₇ (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix.     

Characterization of YBa2Cu3O7/PrBa2Cu3O7 superlattices

We investigated the structural and superconducting properties ofc-axis oriented (YBa₂Cu₃O₇) _nY /(PrBa₂Cu₃O₇) _npr superlattices with thicknesses of the individual layers down to one unit cell (10nY1; 18>nPr 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the samples, though the quantitative analysis shows the existence of defects. In superlattices with decoupled YBa₂Cu₃O₇ layers of two unit cell thickness we find a highT _c value of 75 K. We probed the flux line structure in the superlattices by measurements of the critical current density in magnetic fields. The experiments show that the flux-line dynamics is dominated by the movement of pancake vortices.     

Magnetic coupling in La0.67Ca0.33MnO3/La0.67Sr0.33CoO3/La0.67Ca0.33MnO3 sandwiches

La_0.67Ca_0.33MnO₃ (LCMO)/La_0.67Sr_0.33CoO₃ (LSCO)/LCMO trilayer films are fabricated on single-crystal substrates NdGaO₃ (110) and the interlayer coupling are investigated. Compared with LCMO single layer, sandwiches showed the enhanced metal-insulator transition temperature of LCMO layers. The magnetoresistance is dependent on spacer thickness and the peak value dramatically decreases when LSCO layer is thick enough because of shorting by the LSCO layer. The magnetic coercivity H_C shows a nonmonotonic behavior with changing spacer layer thickness and the waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom LCMO layers across the spacer layer.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.     

MoO3-V2O5-P2O5-Fe2O3玻璃的制备及性能研究

制备了MoO3-V2O5-P2O5-Fe2O3系磷酸盐玻璃,研究了玻璃形成能力、热膨胀系数和抗潮解等性能.结果表明,MoO3-V2O5-P2O5-Fe2O3系统具有较宽的玻璃形成区和较强的玻璃形成能力,当MoO3/V2O5≈1.5时,玻璃形成能力最强.MoO3-V2O5-P2O5-Fe2O3玻璃的热膨胀系数约为60～110×10-7/℃,并且随着Fe2O3含量的增加而逐渐增大.加入适量的Fe2O3能够显著改善MoO3-V2O5-P2O5玻璃的抗潮解性能,在90℃的去离子水中的溶解速率达到8.0×10-9g·cm-2·min-1.     

Structural study of Sr0.3Ba0.7Nb2O6 and La0.030Sr0.255Ba0.700Nb2O6 ceramic systems

Sr_0.3Ba_0.7Nb₂O₆ (SBN) and La_0.030Sr_0.255Ba_0.700Nb₂O₆ (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 °C) and later sintered both at 1400 °C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A₁ site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.     

Microstructures of YBa2Cu3O7/La0.7Ca0.3MnO3 and La0.7Ca0.3MnO3/YBa2Cu3O7 bi-layers grown on (001)LaAlO3

Epitaxial YBa₂Cu₃O₇/La_0.7Ca_0.3MnO₃ (YBCO/LCMO) bi-layers and La_0.7Ca_0.3MnO₃/YBa₂Cu₃O₇ (LCMO/YBCO) bi-layers were grown on (001)LaAlO₃ by pulsed laser deposition, and their microstructures were compared by transmission electron microscopy investigation. In the YBCO(100 nm)/LCMO(150 nm) bi-layers, the LCMO layer consists of columnar grains of ~ 17 nm in diameter and contains mixed orientation domains of [100]_c, [010]_c and [001]_c. The YBCO layer is totally c-axis oriented and the YBCO lattices are tilted − 2.5° to + 2.5° as they grew on the rough surfaces of LCMO columnar grains. For the LCMO(140 nm)/YBCO(140 nm) bi-layers, the LCMO/YBCO interface is sharp and flat. The initial 12-nm thickness of the YBCO layer is composed of c-axis oriented domains, and the upper part of YBCO layer is [100] oriented. The LCMO layer was predominantly [001]_c oriented while [100]_c-oriented domains were occasionally observed.     

Syntheses of hollandite type Rb2Cr8O16, K2Cr2V6O16 and K2V8O16

Hollandite-type compounds, Rb₂Cr₈O₁₆, K₂Cr₂V₆O₁₆ and K₂V₈O₁₆, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb₂Cr₈O₁₆ confirms that the structure is similar to that of K₂Cr₈O₁₆. Magnetic measurements indicate that Rb₂Cr₈O₁₆ is ferromagnetic below 295K, K₂Cr₂V₆O₁₆ paramagnetic down to 77K and K₂V₈O₁₆ has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies.     

静电纺丝法制备的Co0.6Ni0.3Cu0.1Fe2O4和Co0.6Ni0.3Zn0.1Fe2O4纳米纤维的结构及磁性能

采用静电纺丝技术制备出表面光滑、直径均匀的Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4/PVP和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4/PVP纳米纤维前驱丝,经500~900℃煅烧后得到Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维。用TG-DSC、XRD、SEM及VSM现代测试分析手段对Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的结构、形貌及磁学性能进行测试表征。结果表明:在空气气氛中经500~900℃煅烧后可得到纯尖晶石相、结晶度良好的纳米纤维或短纤维;当温度为700℃时,Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的形貌细长而光滑且直径相对均匀,大约为80nm;此时Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维则保有较高的剩磁比(M_r/M_s)及矫顽力,分别为0.56和1 088.87Oe。在500℃、600℃、700℃、800℃、900℃煅烧后,Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的饱和磁化强度分别比Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维增大了14.5%、7%、16%、10.7%、8%,而矫顽力则分别降低了38%、51%、50%、46%、46.7%。两种纳米纤维的饱和磁化强度及矫顽力存在差异,为CoNi铁氧体在电磁方面的应用提供了很好的参考。