氧化镁陶瓷的烧结工艺研究

以硝酸镁、碳酸氢氨为原料,采用均相沉淀法制备碱式碳酸镁,经过不同温度煅烧制得MgO粉体,将粉体压制成型后,经不同温度下烧结,制备MgO陶瓷.TG-DTA、XRD和SEM分析结果表明:碱式碳酸镁的最佳煅烧温度为750 ℃左右,所制得的MgO粉体的晶粒大小为22.25 nm.MgO陶瓷最佳烧结温度为1500 ℃,所得到的陶瓷结构致密、气孔较少、收缩率较高、透光性最好.随着烧结温度的升高,MgO陶瓷中的晶粒有沿(200) 晶面择优生长的趋势.     

一种低T_g双官能聚磷腈的合成与表征

采用"一步法"合成线型聚二氯磷腈(PDCP),并通过亲核反应和后重氮偶合得到了一种含咔唑基和偶氮生色团的低Tg双官能聚磷腈,用1H NMR、31P NMR、IR、TG、DSC及GPC等手段对其进行了结构表征和分析,结果显示其在保持良好的溶解性的同时,具有较低的玻璃化转变温度和良好的热稳定性,分子量可控且分布较窄,比传统的聚磷腈开环聚合法更具优势。     

Electronic and optical properties of Au-doped Cu_2O:A first principles investigation

The Cu2O and Au-doped Cu2O films are prepared on MgO(001) substrates by pulsed laser deposition. The X-ray photoelectron spectroscopy proves that the films are of Au-doped Cu2O. The optical absorption edge decreases by 1.6%after Au doping. The electronic and optical properties of pure and Au-doped cuprite Cu2O films are investigated by the first principles. The calculated results indicate that Cu2O is a direct band-gap semiconductor. The scissors operation of 1.64 eV has been carried out. After correcting, the band gaps for pure and Au doped Cu2O are about 2.17 eV and2.02 eV, respectively, decreasing by 6.9%. All of the optical spectra are closely related to the dielectric function. The optical spectrum red shift corresponding to the decreasing of the band gap, and the additional absorption, are observed in the visible region for Au doped Cu2O film. The experimental results are generally in agreement with the calculated results.These results indicate that Au doping could become one of the more important factors influencing the photovoltaic activity of Cu2O film.     

不同加料方式对共沉淀法制备YAG纳米粉体的影响

用共沉淀法制备了钇铝石榴石(Y3Al5O12)纳米粉体,研究了正滴定、反滴定和一步注入工艺对钇铝石榴石纳米粉体合成过程及最终产物的影响。利用X射线衍射仪、傅立叶红外光谱仪、同步热分析仪、场发射电子显微镜对YAG前驱体及不同温度煅烧后的粉体进行表征。结果表明:通过正滴定、反滴定和一步注入工艺,分别制备出化学组成为10[8.9Al(OH)3+1·1NH4Al·(OH)2CO3]·3[Y2(CO3)3·3H2O]、10[7.3Al(OH)3+2.7NH4Al·(OH)2CO3]·3[Y2(CO3)3.3H2O]、10[Al(OH)3]·3[Y2(CO3)3·3H2O]的前驱体。前驱体经900℃煅烧2 h后,正、反滴定工艺得到的粉体主相为YAG(Y3Al5O12),但有少量的YAP(YAlO3),一步注入工艺则得到纯的YAG相。晶粒尺寸分别为85 nm、70 nm和65 nm,且一步注入工艺获得的粉体粒径分布较窄,分散性良好。     

Fe掺杂氢化非晶碳薄膜制备及其热稳定性能

 以H₂、反式-2-丁烯（T₂B）和二茂铁混合气体为工作气体,用金属有机等离子体增强化学气相沉积法（PECVD）制备了Fe掺杂氢化非晶碳（a-C:H:Fe）薄膜。使用X射线光电子能谱（XPS）对a-C:H:Fe薄膜成分进行了分析。使用台阶仪、场发射扫描电镜（FESEM）、热重分析和紫外可见分光光度计（UV-VIS）,对比分析了a-C:H薄膜和a-C:H:Fe薄膜的沉积速率、表面形貌、热稳定性和光学带隙变化。研究表明：相同制备条件下,相比a-C:H薄膜,a-C:H:Fe薄膜的沉积速率高,表面颗粒小,容易碳化,光学带隙变窄。     

衬底温度对类金刚石薄膜力学性能的影响

 采用脉冲激光沉积方法在不同衬底温度下制备了最高硬度与弹性模量分别达45 GPa和290 GPa,且表面十分光滑的类金刚石薄膜。在相对湿度为80%的条件下,薄膜最低的摩擦系数与磨损率分别为0.045与5.74×10^-10 mm³·N^-1·m^-1。实验结果表明,硬度与弹性模量随衬底温度升高而降低,摩擦系数与磨损率随衬底温度升高而增大。拉曼光谱表明:在室温下制备的薄膜为典型类金刚石结构,sp³含量高达76.8%,而随温度升高,薄膜结构逐渐经无定形碳结构向纳米晶石墨结构方向发展,sp³含量也随之降低,力学性能变差。     

Manipulating metal-insulator transitions of VO2 films via embedding Ag nanonet arrays

Manipulating metal-insulator transitions in strongly correlated materials is of great importance in condensed matter physics, with implications for both fundamental science and technology. Vanadium dioxide (VO₂), as an ideal model system, is metallic at high temperatures and shown a typical metal-insulator structural phase transition at 341 K from rutile structure to monoclinic structure. This behavior has been absorbed tons of attention for years. However, how to control this phase transition is still challenging and little studied. Here we demonstrated that to control the Ag nanonet arrays (NAs) in monoclinic VO₂(M) could be effective to adjust this metal-insulator transition. With the increase of Ag NAs volume fraction by reducing the template spheres size, the transition temperature (T_c) decreased from 68° to 51°. The mechanism of T_c decrease was revealed as:the carrier density increases through the increase of Ag NAs volume fraction, and more free electrons injected into the VO₂ films induced greater absorption energy at the internal nanometal-semiconductor junction. These results supply a new strategy to control the metal-insulator transitions in VO₂, which must be instructive for the other strongly correlated materials and important for applications.     

同质外延生长ZnO单晶结构及光电性能的研究

本文报道了同质外延生长氧化锌(ZnO)单晶在高温氧气气氛退火前后的结构及光电特性.利用化学气相输运(CVT)法生长了红棕色的ZnO单晶,且进行高温氧气气氛退火处理后的ZnO单晶呈现无色透明状.通过X射线衍射仪(XRD)、X射线光电子能谱(XPS)、能谱仪(EDS)和拉曼(Raman)光谱测试分析了高温氧气气氛退火前后的...     

氨水-六甲基二硅胺烷对SiO2化学膜环境稳定性的影响

针对溶胶-凝胶技术制的单层SiO₂化学膜，在室温下研究氨水-六甲基二硅胺烷（HMDS）气氛的量对膜层改性的影响，并在低真空条件下测试了其抗邻苯二甲酸二丁酯（DBP）污染性能。采用紫外-可见-近红外分光光度计（UV-Vis-NIR）、红外光谱仪和原子力显微镜分析了改性前后化学膜特性的演变。研究结果表明:经过DBP污染后，15～30 mL氨水-HMDS改性后化学膜的峰值透过率为99.8%，较改性前化学膜的峰值透过率提升了3.5%，此时化学膜表现出优异的抗污染特性。但是，随着氨水-HMDS处理量的进一步增多，化学膜的激光损伤阈值由改性前的的24.32 J/cm2降到19.36 J/cm2。本研究有助于优化改性参数，以提高化学膜的抗污染性能，在实际工程应用中具有重要的价值。     

Fe3O4/MgO(100)薄膜的激光分子束外延与磁电学性能

 采用激光分子束外延方法,以烧结α-Fe₂O₃/为靶材,在MgO（100）基底上制备了Fe₃O₄薄膜。通过反射高能电子衍射原位观察了薄膜生长前后的表面结构,结果表明所生长的Fe₃O₄薄膜表面平整。经显微激光拉曼光谱和X光电子能谱分析证实所得薄膜表面成分为纯相Fe₃O₄。磁电学性能采用多功能物性系统测量,结果表明：当温度降至100 K附近时,薄膜电阻率有较大增加,Verwey相转变的范围变宽而且不明显,说明反向晶粒边界的存在;在7 160 kA·m^-1的磁场下,室温磁电阻达到-6.9%,在80和150 K温度下磁电阻分别达到-10.5%和-16.1%;薄膜的室温饱和磁化强度约为260 kA·m^-1,其矫顽磁场约为202 kA·m^-1。