云母微晶玻璃/Y-TZP复相材料的制备和力学性能

本文用烧结法制备了云母微晶玻璃／－TZP复相材料,用X光衍射分析（XRD）法测定了材料断裂过程中氧化锆的相变体积分数,用拉曼微探针谱测定了相变区宽度,并对增韧机制进行了研究．结果表明：氧化锆的加入可以显著提高材料的力学性能．当加入40vol％ZrO₂时,云母微晶玻璃的强度和断裂韧性分别可达446MPa和4．8MPam^1／2氧化锆的相变分数随氧化锆含量的增加而减小,而相变区宽度随氧化锆含量的增加而增大;氧化锆主要通过应力诱导相交增韧机制来提高云母微晶玻璃的断裂韧性,但随着氧化锆含量的增加,裂纹在氧化锆颗粒附近的偏转会进一步提高材料的断裂韧性．     

Dynamic mechanical and mechanical properties of polypropylene/poly(vinyl butyral)/mica composites

Three-component composites consisting of polypropylene (PP) matrix, poly(vinyl butyral) (PVB) modifier, and mica filler at various ratios of matrix to modifies and a constant mica content (30 wt %) were prepared by using two different kinds of PVB, viz., PVB and PVB-P. By correlating with the morphology, the dynamic mechanical and mechanical properties of the composites are studied in detail. PVB component in PP/PVB/mica composites cannot display a reinforcing effect to PP/mica binary composites, while impact strength of the composites are reduced further. It associates with incompatibility between PP and PVB, and as well as higher glass transition temperature of PVB. For PP/PVB-P/mica composites, stiffness decreases and, meanwhile, impact strength increases when PVB-P content is 7 wt %. The improvement of impact strength on PP/mica binary composites at the composition is due to a little affinity between the PP matrix and the plasticizer of PVB-P. Moreover, a minor amount of PP-g-MA in the 63/7/30 PP/PVB/mica composites only acts as an adhesion promoter. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2003–2011, 1997     

聚酰亚胺纳米杂化薄膜绝缘材料77K下的电击穿性能研究

介绍了77K下薄膜状绝缘材料电气强度的测试方法,研究了聚酰亚胺/蒙脱土、聚酰亚胺/云母、聚酰亚胺/SiO2三个系列的低温电气强度。结果表明:前两个系列填料对电气强度的影响趋势相同,均存在最佳填料含量,聚酰亚胺/蒙脱土电气强度最佳可达215.77MV/m;对于聚酰亚胺/SiO2系列,电气强度比纯PI薄膜略有下降,且含量较高时下降明显,但仍然可以满足应用的要求。     

PP/PP-g-MMA/M复合材料非等温结晶动力学研究

用示差扫描量热法(DSC)考察了聚丙烯(PP)、聚丙烯/云母(PP/M)和聚丙烯/聚(丙烯-g-甲基丙烯酸甲酯)/云母复合材料(PP/PP-g-MMA/M)的非等温结晶过程.用Avrami方程和Ozawa方程对上述过程进行分析,n、t1/2、F(T)、Tp等参数表明,M和PP-g-MMA,特别是PP-g-MMA的掺入改变了PP的结晶成核和生长机理.用Dobreva方法分析填料的成核活性,ε数值表明,M有较强的成核活性,PP-g-MMA的掺入又进一步增强其成核活性,从而使结晶温度明显提高.Kissinger方法的计算结果表明,添加M可使PP的结晶活化能减小,再添加PP-g-MMA又使PP/M复合体系的结晶活化能进一步减小.     

AFM的DNA样品制备技术研究

AFM应用中最为关键的一步无疑是样品的制备。本文介绍DNA样品制备的几种主要方法,通过实验发展了两种适合对DNA及其碎片进行长度测量和做统计分析的制样方法,它们分别采用APS-云母和纯云母为衬底。这两种方法不仅丰富了DNA样品制备方法,对推广AFM在生物研究中的应用也具有重要意义。     

Van der Waals Epitaxy Enables Rollable Dielectric Superlattice for Record High Overall Energy Density

Nanoengineered polar oxide films have attracted much attention for electric energy storage thanks to their high energy density, though they are all deposited on thick and rigid substrates, resulting in inferior overall energy density and poor manufacturability. Herein, an alternative strategy is developed for oxide dielectrics utilizing van der Waals epitaxy on ultrathin and flexible mica substrate, with a dielectric superlattice of Pb_0.92La_0.08(Zr_0.95Ti_0.05)O₃-SrTiO₃ carefully engineered to break its long-range antiferroelectric polar order. An ultrathin flexible capacitor is obtained as a result, with a record high overall energy density of 12.19 J cm⁻³ and an efficiency of 90.98%, and there is much room for further improvement since mica substrate can approach 2D limit. The superlattice can be easily rolled for large-scale manufacturing, and the energy storage performances are well maintained under large bending deformation as well as extended bending cycling. The study thus establishes a viable route for dielectric oxide films, paving way for their practical applications in high-energy density capacitors.     

某非金属矿钽铌锂铷综合回收选矿试验研究北大核心

甘肃某非金属矿主要矿物组成为石英、长石、云母,矿石中伴生有锂、铷、钽、铌等有价金属。针对矿石中钽铌比重大、具有磁性且矿石泥化严重、云母嵌布特性复杂等性质特点,采用“高梯度磁选、摇床精选钽铌—钽铌磁选尾矿脱泥浮选云母—云母粗精矿和钽铌精选尾矿合并再磨精选云母—云母浮选尾矿进行长石石英分离”的工艺流程,获得了Ta_(2)O_(5)+Nb_(2)O_(5)品位和回收率分别为30.16%、55.85%的钽铌精矿;Li_(2)O、Rb_(2)O品位分别为3.28%、0.59%,回收率分别为92.80%、42.35%的云母精矿;Rb_(2)O品位为0.18%、回收率为49.51%的长石精矿和SiO_(2)品位为99.23%的石英精矿,长石精矿和云母精矿中Rb_(2)O总回收率为91.86%,钽铌精矿和石英精矿可作为合格产品直接销售,云母精矿和长石精矿作为后续冶炼工艺提取锂铷的原料,研究结果为矿石的综合利用提供了技术依据和支撑。     

Switchable and Reversible p+/n+ Doping in 2D Semiconductors by Ionic 2D Minerals

2D semiconductors are promising for fabricating miniaturized and flexible electronic devices. The manipulation of polarities in 2D semiconductors is key to fabricate functional devices and circuits. However, the switchable and reversible control of polarity in 2D semiconductors is challenging due to their ultrathin body. Herein, a reversible and non-destructive method is developed to dope 2D semiconductors by using ionic 2D minerals as the electrostatic gating. The 2D semiconductor channel can be reversibly transformed between n⁺ and p⁺ types with carrier concentrations of 1.59 × 10¹³ and 6.82 × 10¹² cm⁻², respectively. With the ability to in situ control carrier type and concentration in 2D semiconductors by ionic gating, a reversible PN/NP junction and programmable logic gate are demonstrated in such devices. This 2D mineral materials-based ionic doping approach provides an alternative method for achieving multi-functional and complex circuits in an all-2D material flatform.     

石煤硫酸浸出过程中含钒矿物的浸出行为北大核心

以陕西省商南县石煤钒矿为研究对象,研究了直接酸浸、氧化酸浸及活化酸浸的提钒效果,分析了酸浸过程中含钒矿物钒的浸出规律和活化浸出机理。结果表明:在硫酸浓度250 g/L、液固比5 mL/g、温度90℃条件下,浸出12 h,钒浸出率仅为48.55%;在相同条件下,加入3%氯酸钠,氧化酸浸9 h,钒浸出率增加到61.42%;再添加9%氟化钙,仅活化浸出6 h,钒浸出率可达到92.90%。工艺矿物学研究表明:在活化酸浸过程中,氟化钙与硫酸反应生成的氢氟酸,促进了硫酸对含钒矿物结构的破坏,同时参与了含钒云母的反应,促进了含钒矿物中钒的浸出;矿物中含钒云母、钒钛矿、褐铁矿、钒硫化物中钒的浸出率分别为98.47%、42.22%、98.09%、89.70%,与氧化酸浸相比,分别增加了31.77、26.90、18.01、89.70个百分点。