原位沉析法制备壳聚糖棒材的研究

以壳聚糖凝胶膜为模板,将壳聚糖溶液与NaOH凝固液隔离,利用膜渗透原位沉析法制备了高性能的壳聚糖棒材(d=4.5mm),其弯曲强度、弯曲模量和剪切强度分别为92.4MPa,4.1GPa和36.5MPa.扫描电子显微镜(SEM)分析结果表明,原位沉析法制备的壳聚糖棒材具有同心筒状层叠结构,并对其成型机理进行了探讨.     

原位复合法制备层状结构的壳聚糖/羟基磷灰石纳米材料

用原位复合法制备了高性能的壳聚糖/羟基磷灰石(CS/HA)纳米复合材料.用预先沉积的壳聚糖膜将含有羟基磷灰石前驱体的壳聚糖溶液与凝固液隔离,同时控制壳聚糖沉积与羟基磷灰石前驱体转化为羟基磷灰石的过程,使其缓慢且有序地进行.当pH值改变时,质子化的壳聚糖分子链在负电层诱导下有序沉积并形成层状结构与羟基磷灰石原位生成CS/HA,并实现二者分子级复合.XRD和TEM测试证实原位生成的磷酸盐是羟基磷灰石,且其颗粒长约为100nm,宽30～50nm.SEM结果表明,用原位复合法制备的材料具有层状结构,CS/HA(质量比100/5)纳米复合材料弯曲强度高达86MPa,比松质骨的高3～4倍,相当于密质骨的1/2,有望用于可承重部位的组织修复材料.     

原位沉析法制备磁性氧化铁羟基磷灰石/壳聚糖棒材

首先通过化学沉淀法制备磁性氧化铁羟基磷灰石(Fe3O4/HA),然后以壳聚糖(CS)为基体,利用原位沉析法将Fe3O4/HA与CS复合,制得磁性Fe3O4/HA/CS复合材料.经XRD、粒径分布和PPMS测试,结果表明了Fe3O4/HA复合物的生成.系统研究了磁性Fe3O4/HA/CS棒材力学性能的影响因素,最终确定Fe3O4与HA质量比为3∶17,磁性Fe3O4/HA与CS质量比为9∶91时,棒材的力学性能最优,弯曲强度可达到87.0 MPa,弯曲模量1.57 GPa.     

电磁处理对水溶液中碳酸钙微粒沉降及附着性能的影响

通过Zeta电位、表面自由能及其分量、粘附功等热力学参数的测定与分析, 研究了电磁处理对等物质的量Na₂CO₃与CaCl₂溶液混合生成的碳酸钙微粒的沉积特性及阻垢机理. 结果显示电磁处理可以使碳酸钙微粒的Zeta电位绝对值减小约5 mV, 同时加快碳酸钙微粒的沉降速度. 经电磁处理生成的碳酸钙微粒的表面自由能为31.59 mJ•m^－2, 比未经处理时减小30%, 同时表面自由能Lifshitz-van der Waals分量从处理前的43.53 mJ•m^－2下降到25.50 mJ•m^－2, 说明成垢溶液的电磁处理可以提高碳酸钙微粒的热力学稳定性. 水溶液中碳酸钙微粒与316L不锈钢表面之间的理论粘附功计算显示, 电磁处理降低了该理论粘附功, 使碳酸钙微粒在不锈钢表面的附着能力下降.     

流化床O2/CO2气氛下添加石灰石对燃煤PM2.5的控制

采用小型流化床研究了在O₂/CO₂气氛下添加石灰石对PM_2.5(空气动力学直径小于2.5 μm的颗粒物)的控制.实验采用荷电低压撞击器(ELPI)采集和分析燃烧后的PM_2.5.结果表明,添加石灰石是燃烧过程中影响PM_2.5生成的重要因素.添加石灰石后,生成PM_1.0的数量浓度均降低,而PM_1.0~2.5的数量浓度均略有增加;PM_2.5质量粒径分布均呈双峰分布,峰值分别出现在0.2和2.0 μm左右.随着Ca/S物质的量比的增加,PM_2.5中Si、Na、K、S和Cu的含量呈减少的趋势;随着颗粒粒径的减小,S、Cu、K和Na的含量有增大的趋势,而Si的含量有减少的趋势.     

N-羧丙酰壳聚糖钠增强改性壳聚糖棒材

采用原位沉析法制备N-羧丙酰壳聚糖钠增强改性的三维壳聚糖复合棒材, 并用傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、热重(TG)分析、扫描电镜(SEM)以及力学性能测试等方法研究复合棒材结构与性能之间的关系. FTIR分析表明, 壳聚糖分子中的氨基官能团和乙酰氨基官能团均与N-羧丙酰壳聚糖钠分子中的羧酸盐官能团发生强烈的静电相互作用. 加入N-羧丙酰壳聚糖钠后: 两种分子间产生强烈的静电相互作用, 限制了大分子链的运动, 使得大分子链趋于刚性, 同时复合棒材的层状叠加结构变得更加紧密, 提高了复合棒材的热稳定性与力学性能; 大分子链的刚性增强, 限制了分子链排入晶格, 从而降低了壳聚糖的结晶度. 当复合棒材中含有15% (w)的N-羧丙酰壳聚糖钠时, 其弯曲强度和弯曲模量可达156.0 MPa、5.3 GPa, 与纯壳聚糖棒材相比, 分别提高了68.8%、29.3%.因此, N-羧丙酰壳聚糖钠可有效地增强改性三维壳聚糖棒材, 该三维复合物棒材有望用作骨折内固定材料.     

电结晶制Co/Pt多层膜的结构及磁性研究

以单晶Si(111)为基底, 在以P盐[主要成分Pt(NO₂)₂(NH₃)₂]和CoSO₄为主盐的硼酸体系中电结晶Co/Pt多层膜. SEM观察多层膜的断面形貌, 证实多层膜具有周期结构. 经XRD测试, 首次证实了Co-Pt界面上有CoPt₃化合物的存在. 用PPMS测试了多层膜的磁滞回线, 平行于外磁场时膜的矫顽力约为165 Oe, 垂直于外磁场时的矫顽力随Co含量的增加而增加, 最大达到396 Oe. 首次用电结晶方法制得了易磁化轴垂直于膜面的Co/Pt多层膜.     

一种基于静电吸附作用的直接检测补体C3新型可再生电容型免疫传感器

通过壳聚糖/褐藻酸钠体系实现抗体在电极上的固定,制得可多次再生的电容型免疫传感器,用于补体C₃的检测.先在金电极表面上组装一层半胱胺单分子层,通过戊二醛把壳聚糖修饰在金电极上,再用十二硫醇封闭电极,最后,利用壳聚糖与褐藻酸钠之间的强静电相互作用实现抗体的固定.使用交流阻抗法研究了溶液pH值和离子强度对电极膜层稳定性及对抗体固定性的影响.结果表明,所制备的传感器操作简便,易于再生,电容响应与补体C₃浓度在18.2～292.5ng/mL范围内呈线性关系,检出限为9.1ng/mL.     

电解质对TiO2纳米管阵列膜光生阴极保护效应的影响

基于光电化学测试考察了光电解池中电解质(NaNO₃, NaCl, Na₂SO₄, Na₂S和NaOH)的种类和浓度对阳极氧化法制备的锐钛矿型TiO₂膜电极光电性能的影响, 并解释了其作用机理.结果表明, 电解质捕获空穴的能力顺序为Na₂S>NaOH>Na₂SO₄>NaCl>NaNO₃.Na₂S和NaOH在溶液中具有协同作用, 当两者组成混合溶液并且浓度均为0.5 mol/L时, 更有利于TiO₂膜光生电子-空穴对的分离和光电转化性能的提高.当0.5 mol/L NaCl溶液中的403不锈钢(403SS)与0.5 mol/L Na₂S+0.5 mol/L NaOH混合溶液中的TiO₂膜电极耦连时, 光照膜电极可使403SS的电极电位负移约650 mV, 具有良好的光生阴极保护效应.当切断光源时, 在该混合液中TiO₂膜也能对403SS起到一定的阴极保护作用.     

SIFSIX-3-Ni膜的制备及氢气分离性质

利用(NH₄)₂SiF₆修饰大孔玻璃基底后, 在溶剂热条件下制备了SIFSIX-3-Ni膜, 并研究了温度和浓度对制备SIFSIX-3-Ni膜的影响. 能谱分析(XPS)结果表明大孔玻璃表面引入了氟元素. SIFSIX-3-Ni膜的粉末X射线衍射(PXRD)峰位置和模拟结果一致, 表明成功制备出SIFSIX-3-Ni膜. 从扫描电子显微镜(SEM)照片中观察到膜连续均匀, 厚度约为20 μm. 热重分析(TGA)结果表明, 活化前的膜没有客体分子. 单组分测试结果表明, 膜的H₂, CO₂和N₂渗透量分别为6.83×10 ^-6, 7.42×10 ^-7和8.89×10 ^-7 mol·m ^-2·s ^-1·Pa ^-1, H₂/CO₂和H₂/N₂的理想分离比分别为9.20和7.68. 在连续测试5 h后, H₂, CO₂和N₂渗透量基本保持不变, 表明SIFSIX-3-Ni膜具有很好的稳定性.     

碳酸钙微米球的制备与表征

采用醋酸钙和碳酸钠为原料,在反应温度为5℃和柠檬酸三钠质量百分浓度为15%的条件下,采用沉淀法合成出了粒度为1～4μm、分散性好的球形碳酸钙粉体。用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、红外光谱仪(IR)、原子力扫描探针显微镜(ASPM)、光学显微镜、粒度分析仪等对样品进行了表征,并用光学显微镜跟踪考察了碳酸钙微米球的形成过程。结果表明,碳酸钙微米球是由大量纳米级颗粒组装而成。     

孪生球状碳酸钙的直接混合沉淀法制备及表征

以醋酸钙和碳酸钠为原料, 柠檬酸三钠为晶形控制剂, 利用液相直接混合沉淀法合成了分散性好、粒度约1.5~3.0 μm、长短轴比约2∶1的孪生球形碳酸钙晶体. 利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶红外光谱仪(FTIR)、原子力扫描探针显微镜(ASPM)和粒度分析仪等对样品进行了表征. 结果表明, 在不添加柠檬酸三钠的溶液中得到微米级的立方状碳酸钙晶体, 而添加柠檬酸三钠(质量分数30%~40%)后则得到具有不同表面粗糙度的孪生球状碳酸钙晶体. 同时, 用分形生长理论和成核限制聚集(NLA)模型对孪生球状碳酸钙粒子的形成机理进行了分析.     

Formation of stable vaterite with poly(acrylic acid) by the delayed addition method

The crystallization of CaCO3 was examined by changing the addition time of poly(acrylic acid) (PAA) to an aqueous solution of calcium carbonate by selectively interacting with the crystal at different stages during the crystal-forming process. The precipitation of CaCO3 was carried out by a double jet method to prevent heterogeneous nucleation on glass walls, and the sodium salt of PAA was added by a delayed addition method. In the initial presence of PAA in an aqueous solution of calcium carbonate, PAA acted as an inhibitor for the nucleation and growth of crystallization. However, it was found that stable vaterite particles were successfully obtained by delaying the addition of PAA from 1 to 60 min. The vaterite particles were stable in the aqueous solution for more than 30 days, and the CaCO3 particles were formed by a spherulitic growth mechanism. It is suggested that PAA strongly binds with the Ca2+ ion on the surface of CaCO3 particles to stabilize the unstable vaterite form effectively. Upon changing the addition time of PAA, we found that CaCO3 particles were formed through different formation mechanisms in selectively controlled crystallization at different stages during the crystallization process.     

Formation of calcium alginate-based macroporous materials comprising chitosan and hydroxyapatite

Macroporous alginate hydrogels are prepared by the internal gelation method using crystalline saccharose. For this purpose, a sodium alginate solution containing D-glucono-δ-lactone and dispersed calcium carbonate particles was added to saccharose. Hydrolysis of D-glucono-δ-lactone gives rise to gradual acidification of the solution, which results in the decomposition of CaCO₃ with the release of calcium cations; the latter crosslink polysaccharide macromolecules via chelate complexes to cause the formation of a gel. Washing out saccharose with water results in the formation of pores separated by calcium alginate films with a thickness of smaller that 100 nm. It is shown that the proposed method can be applied to produce a composite material containing particles of hydroxyapatite, which is incorporated into implants to accelerate the repair of bone tissues. The particles are entrapped into alginate films. A cationic polysaccharide, chitosan, is additionally incorporated into the alginate materials for their reinforcement; its stabilizing action is achieved via the formation of a polyelectrolyte complex with negatively charged alginate macromolecules. Chitosan is incorporated by a new method, which consists in gradually charging the polysaccharide during the acidification of the solution as a result of D-glucono-δ-lactone hydrolysis. Materials thus prepared are characterized by different methods, including scanning electron microscopy, dynamic mechanical analysis, and porosimetry.     

Preparation and properties of gluten/calcium carbonate composites

Environment friendly thermosetting composites were prepared by blending wheat gluten （WG） as matrix, calcium carbonate （CaCO3） as filler and glycerol as plasticizer followed by compression molding the mixture at 120 ℃ to crosslink the WG matrix. Morphology observation showed that the CaCO3 particles were finely dispersed in matrix. Incorporation of CaCO3 up to 10 wt% into the composites caused Young＇s modulus and tensile strength to increase markedly. On the other hand, the moisture absorption and elongation at break decreased slightly.     

Synthesis of uniform and dispersive calcium carbonate nanoparticles in a protein cage through control of electrostatic potential

We have synthesized calcium carbonate nanoparticles (Ca-NPs) in the cavity of a cage-shaped protein, apoferritin, by regulating the electrostatic potential of the molecule. The electrostatic potential in the cavity was controlled by pH changes resulting from changes in the dissolved carbon dioxide (CO(2)) concentration in the reaction solution. Recombinant L-apoferritin was mixed with a suspension of calcium carbonate (CaCO(3)), and the mixture was pressurized with gaseous CO(2) at 2 MPa. The pH of the solution decreased from 9.3 to 4.4; the CaCO(3) dissolved during pressurization, and then precipitated after the pressure was reduced to ambient. After repeating the pressurization/depressurization process three times, about 70% of the apoferritin molecules were found to contain nanoparticles with an average diameter of 5.8 ± 1.2 nm in their cavity. Energy-dispersive X-ray spectroscopy and electron diffraction analysis showed that the nanoparticles were calcite, one of the most stable crystal forms of CaCO(3). Electrostatic potential calculations revealed a transition in the potential in the apoferritin cavity, from negative to positive, below pH 4.4. The electrostatic potential change because of the change in pH was crucial for ion accumulation. Since the Ca-NPs synthesized by this method were coated with a protein shell, the particles were stably dispersed in solution and did not form aggregates. These Ca-NPs may be useful for medical applications such as synthetic bone scaffolds.     

纳米级CaCO_3粒子与弹性体CPE微粒同时增韧PVC的研究

研究了平均粒径为 30nm的超细级纳米CaCO3 与氯化聚乙烯 (CPE)对聚氯乙烯 (PVC)共混体系二元协同增韧效应及机制 .结果表明 ,当共混体系中有一定量的CPE时 ,纳米CaCO3 的加入可以明显地提高共混物的韧性 ,而不降低共混物的强度和刚性 .纳米CaCO3 在PVC基体中达到了纳米级的分散 .当纳米CaCO3 的用量为 8份 (质量 )时 ,PVC CPE 纳米CaCO3 共混物的冲击断面产生了大量的有规则的网丝状结构 ,共混物的缺口冲击强度达到 81 1kJ m2 ,比不加纳米CaCO3 的共混体系高 7 3倍 .CPE的加入对共混体系的加工流动性能无影响 ,纳米CaCO3 的加入使共混体系的加工流动性能变差     

阴离子氨基酸表面活性剂调控碳酸钙的仿生合成

室温下, 在乙醇或乙醇-水混合体系中, 利用氨基酸表面活性剂N-酰基十二烷基肌氨酸钠(Sar)调控合成碳酸钙, 采用SEM, XRD和FTIR等技术表征了反应产物. 在乙醇体系中, 首先形成多面体形状的文石, 然后逐渐转变为圆球状的无定形碳酸钙. 在乙醇-水混合体系中, 合成了花簇状多级结构碳酸钙晶体. 增加N-酰基十二烷基肌氨酸钠的用量有助于形成球霰石结构, 当n(Ca2+)∶n(Sar)=1∶1 时, 得到的花状碳酸钙为球霰石和方解石的混合物, 当n(Ca2+)∶n(Sar)=1∶2 时, 得到纯净的球霰石, 其形貌为大小较均一的单分散的球, 直径约为7 μm; 另外, 当n(Ca2+)∶n(Sar)=1∶1时, 混合溶剂中水和乙醇的体积比由1.5∶1依次增加为7∶3和3∶1时, 碳酸钙晶体的形貌由花状逐渐向球形过渡, 晶体中球霰石和方解石的含量也随之变化, 其中, 当水和醇的体积比为7∶3时, 产物主要为球霰石型晶体.     

无添加剂条件下文石型碳酸钙晶须制备及影响因素研究

在不加任何结晶控制剂或模板条件下,以CaCl2和Na2CO3为原料,利用复分解反应法制备了具有较好形貌和高长径比,且分布均一的文石型碳酸钙晶须,并利用扫描电镜(SEM)、X-射线粉末衍射(PXRD)和傅里叶转换红外光谱图(FT-IR)等手段对其进行了表征。研究了浓度、滴加速度、反应温度、搅拌速度以及滴加方式等因素对碳酸钙晶须的影响。结果表明最佳制备工艺为:CaC12溶液与Na2CO3溶液的浓度为0.05 mol.L-1,溶液滴加速度为1 mL.min-1,反应体系温度为80℃,搅拌速度为250 r.min-1。     

Interaction between biopolyelectrolytes and sparingly soluble mineral particles

We investigate the complex physicochemical behavior of dispersions containing calcium carbonate (CaCO(3)) particles, a sparingly soluble mineral salt; and carrageenans, negatively charged biopolyelectrolytes containing sulfate groups. We reveal that the carrageenans suspend and stabilize CaCO(3) particles in neutral systems by absorbing on the particle surface which provides electrosteric stabilization. In addition, carrageenans provide a weak apparent yield stress which keeps the particles suspended for several months. The absorption measurements of carrageenan on the CaCO(3) particle indicate that more carrageenan is removed from the solution than expected from the case of a simple monolayer adsorption. Confocal laser scanning microscopy observations confirm that polyelectrolyte-containing precipitate is formed in both CaCO(3)-carrageenan and CaCl(2)-carrageenan mixtures. On the basis of these results, we confirm that in the presence of carrageenan some CaCO(3) dissolves and the Ca(2+) ions interact with the sulfate groups leading to aggregation and formation of particle-like structures. These new insights are important for fundamental understanding of other mineral-polyelectrolyte systems and have important implications for various industrial applications where calcium carbonate is used.