MgO焙烧-碳热氯化法提取包钢选矿厂尾矿中的稀土

包钢选矿厂尾矿中含有大量稀土,可以回收利用.提出MgO焙烧-碳热氯化提取包钢选矿厂尾矿中稀士的新工艺.在该工艺中首先将尾矿与MgO混合焙烧脱氟,然后使用氯气作为氯化剂,碳作为还原剂,碳热氯化该脱氟后的尾矿中的稀土,水浸取回收稀土.考察了MgO的用量、碳热氯化时间、碳热氯化温度对稀土提取率的影响.结果表明:尾矿与Mgo焙烧后,700℃氯化反应0.5 h,氯化率高达83%.利用X射线衍射探讨了脱氟过程可能发生的反应.     

1kHz窄脉宽高峰值功率MgO∶LN电光腔倒空Nd∶YAG激光器

报道了一种1kHz窄脉冲宽度、高峰值功率的电光腔倒空1 064nm全固态激光器.该激光器采用808nm脉冲LD侧面泵浦Nd:YAG晶体棒的双凹型折叠谐振腔结构和同步延迟MgO∶LN晶体横向加压式电光腔倒空技术,通过优化设计谐振腔结构,在脉冲重复频率200Hz时,获得了最大单脉冲能量46.7mJ、脉冲宽度4.06ns、峰值功率11.50MW的1 064nm脉冲激光稳定输出,脉冲宽度和能量的峰峰值不稳定度分别为±1.52%和±2.02%;在1kHz时,最大单脉冲能量达到18.3mJ,脉冲宽度5.02ns,峰值功率3.69MW,脉冲宽度和能量的峰峰值不稳定度分别为±2.75%和±3.52%,激光束因子为3.849和3.868,远场发散角为3.46mrad和3.55mrad,束腰直径为1 508.84μm和1 477.30μm.     

不同表面活性剂对合成介孔氧化镁晶体性质的影响

采用液相法,以Mg(NO3)2·6H2O为镁源,NH3·H2O为沉淀剂,研究了不同表面活性剂对介孔MgO晶体性质的影响.采用XRD、FT-IR、SEM、BET和CO2-TPD等手段对介孔MgO晶相组成、骨架结构、微观形貌、孔结构及表面化学性质进行了分析表征.研究结果表明,不同表面活性剂对介孔MgO晶体物化性质影响较大.以非离子型PEG-2000为表面活性剂制得产品表面碱强度和碱总量均大于以阴离子型SDS、阳离子型CTAB制得的产品.以非离子型PEG-2000为表面活性剂制备得到的介孔MgO同时具有弱碱、中强碱特征,碱总量为0.192 mmol·g-1,比表面积、孔容和平均孔径分别为145.42 m2·g-1、0.67 cm3·g-1和18.56 nm.     

单层FeSe薄膜/氧化物界面高温超导

单层FeSe/SrTiO₃界面增强超导的发现为理解高温超导机理提供了一个新的途径,也为实现新的高温超导体开拓了新思路.本文通过在SrTiO₃（001）表面高温沉积Mg进而沉积单层FeSe薄膜,制备出了FeSe/MgO双层/SrTiO₃异质结.利用扫描隧道显微镜研究了异质结的电学及超导特性,观测到约14–15 meV的超导能隙,比体相FeSe超导能隙值增大了5–6倍,与K掺杂双层FeSe/SrTiO₃的超导能隙值相当.这一结果可理解为能带弯曲造成的界面电荷转移和界面处电声耦合共同作用导致的超导增强.FeSe/MgO界面是继FeSe/TiO₂之后的一个新界面超导体系,为研究界面高温超导机理提供了新载体.     

准相位匹配周期极化高掺镁铌酸锂532 nm倍频准连续输出研究

对周期性极化高掺镁铌酸锂倍频过程进行了准相位匹配倍频理论研究。在室温下通过外加电场极化法,用较低的极化开关电场～5．5kV／mm,在厚为1mm、长为10mm、宽为10mm的掺镁铌酸锂基片上成功地制备了周期为5．8～7．3pm(间隔0．3pm)的一阶准相位匹配倍频周期性极化光学微结构。将温度控制在70℃左右,以波长为1．060μm的Nd：YAG激光为基频光源,对所研制的光学微结构样品进行倍频通光实验验证。当入射基频光为920mW时,可以获得约15mW的532nm准连续倍频蓝光输出．其归一化转换效率高达1．77％／W。     

离子交换树脂均匀沉淀法制备MgO纳米粒子

以(Mg(NO3)2·6H2O, (NH4)2CO3 和NH3·H2O为原料,采用两种离子交换树脂均匀沉淀法分别制备MgO纳米粒子.用热分析、X射线粉末衍射(XRD)、透射电子显微镜(TEM)、高分辨电子显微镜(HR TEM)、选区电子衍射(SAED)和BET等对所制备的MgO粒子进行了表征.结果表明:经700 ℃焙烧后制备的MgO纳米晶体属六方晶系,样品分散性较好,平均粒径约为25 nm;MgO纳米晶体清晰、有序的电子衍射点阵,表明晶体的结晶度较好;纳米粒子a和b的比表面积分别为31 m2/g and 32 m2/g.     

Removal of scratch on the surface of MgO single crystal substrate in chemical mechanical polishing process

Etching and chemical mechanical polishing (CMP) experiments of the MgO single crystal substrate with an artificial scratch on its surface are respectively performed with the developed polishing slurry mainly containing 2 vol.% phosphoric acid (H₃PO₄) and 10-20 nm colloidal silica particles, through observing the variations of the scratch topography on the substrate surface in experiments process, the mechanism and effect of removing scratch during etching and polishing are studied, some evaluating indexes for effect of removing scratch are presented. Finally, chemical mechanical polishing experiments of the MgO substrates after lapped are conducted by using different kinds of polishing pads, and influences of the polishing pad hardness on removal of the scratches on the MgO substrate surface are discussed.     

Fabrication of MgO barrier for a magnetic tunnel junction in as-deposited state using amorphous RE–TM alloy

MgO (1 0 0) textured films on Fe buffer layer with (1 0 0) preferential orientation were prepared by a reactive facing targets sputtering system at a substrate temperature of 100 °C during MgO deposition. This process can allow fabrication of MgO (1 0 0) tunneling barrier layer without high-temperature annealing process after the sputter-deposition. In addition, FeCo (1 0 0) preferred orientation films prepared on GdFeCo layers were improved with GdFeCo thickness. MgO films deposited on Fe (or FeCo) buffer layers revealed apparent (1 0 0) preferred orientation at the early stage of the film growth. 3 nm-thick MgO films deposited on GdFeCo [100 nm]/Fe [3 nm] exhibited (1 0 0) texture. Magnetic characteristic of perpendicular-magnetic tunnel junction (P-MTJ) element with the structure of GdFeCo [100 nm]/Fe [3 nm]/MgO [3 nm]/Fe [3 nm]/TbFeCo [100 nm] exhibited high squareness ratio of 0.8 and coercivity of free layer as low as 117 Oe by anomalous Hall effect, and (1 0 0) preferred orientation of 3 nm-thick MgO layer was observed by an X-ray diffractometer.     

ZnO-based terahertz quantum cascade lasers

High-power terahertz sources operating at room-temperature are promising for many applications such as explosive materials detection, non-invasive medical imaging, and high speed telecommunication. Here we report the results of a simulation study, which shows the significantly improved performance of room-temperature terahertz quantum cascade lasers (THz QCLs) based on a ZnMgO/ZnO material system employing a 2-well design scheme with variable barrier heights and a delta-doped injector well. We found that by varying and optimizing constituent layer widths and doping level of the injector well, high power performance of THz QCLs can be achieved at room temperature: optical gain and radiation frequency is varied from 108 cm^?1 @ 2.18 THz to 300 cm^?1 @ 4.96 THz. These results show that among II–VI compounds the ZnMgO/ZnO material system is optimally suited for high-performance room-temperature THz QCLs.     

电场中(MgO)2吸附H2的理论研究

电场诱导MgO材料吸附H2是一种有效的储氢方法,而较高的场强制约其广泛应用。本文在B3LYP/CC-PVTZ水平上对电场中 (MgO)2团簇的储氢性质进行了研究,结果表明仅需外加强度为0.005 a. u. 的电场,就能使其对单个H2在Mg/O上的吸附能由无电场时的-0.143/-0.091 eV提高到-0.202/-0.134 eV. 该场强远小于其他大尺寸MgO材料达到相同吸附强度所需的电场,表明降低材料尺寸是减少储氢所需电场强度的一种可能方法。计算还表明电场中(MgO)2最多能吸附8个H2,相应的质量密度达到16.7 wt%。