利用氧化镁热分解氯化铵制氨气工艺的研究

确定了得到MgOHCl产物所需转化剂的用量,以反应温度、反应物的摩尔比、反应时间为变量,固体产物中的氮质量分数、氯收率为评价指标,对MgO热分解NH4Cl制NH3的工艺条件进行了研究。实验结果表明,在反应温度为375℃,转化剂、MgO、NH4Cl的摩尔比为1.3∶1∶0.6,反应时间为60 min时,固体产物中氮质量分数约为0,氯收率可达到90%以上。同时在加入适量转化剂的条件下,MgO分解NH4Cl能够直接生成MgOHCl,不需向反应器中通入蒸汽,简化了工艺流程。     

助剂MgO对甲烷二氧化碳重整Co/BaTiO3催化剂催化性能的影响

采用溶胶-凝胶法在Co/BaTiO3催化剂中引入助剂MgO,考察了其对甲烷二氧化碳重整Co/BaTiO3催化剂的催化反应性能的影响,利用X射线衍射仪(XRD)、H2程序升温还原(H2-TPR)对催化剂进行了表征,结果表明,助剂MgO使钴催化剂中的活性Co2O3组分增多,还原性和分散性能较好;在n(CO2)∶n(CH4)为1∶1、气相空速(GHSV)为12 000 h-1、反应温度为700℃的条件下,催化剂Co-MgO/BaTiO3表现出良好的催化性能,且反应初期甲烷转化率可达到94.87%,CO选择性可达85.21%,H2收率可达74.08%。     

粉末冶金法制备纳米MgO颗粒增强铜基复合材料

采用粉末冶金法制备了不同体积分数的纳米MgO颗粒增强铜基复合材料,测定了MgO/Cu复合材料的密度、硬度和电导率,并进行了微观组织观察。结果表明,随着MgO颗粒含量的增加,MgO/Cu复合材料的密度和电导率降低,硬度先升高后降低,当MgO体积分数达到2.5%时,综合性能最好。微观组织观察表明,热挤压后,增强相颗粒弥散分布在铜基体上;随着增强相体积分数的增加,颗粒出现团聚并聚集在铜基体晶界处。     

Influence of oxygen content on the crystallinity of MgO layers in magnetic tunnel junctions

With RF sputtering process, Si/Si02/Ta/Ru/Ta/CoFeB/MgO/CoFeB/Ta/Ru structure has been grown on Si （100） substrate. Attempting different targets and adjusting the oxygen dose, the crystallization quality of the MgO layer is studied. The X-ray diffraction measurements demonstrate that crystal structure and crystallization quality of MgO layers are related to the type of target and concentration of oxygen in sputtering process. With the method sputtering Mg in an ambient flow of oxygen, not only the crystallization quality of a normal MgO layer with lattice constant of 0.421 nm is improved, but also a new MgO crystal with lattice constant of 0.812 nm is formed and the perpendicular magnetic anisotropy of CoFeB is enhanced. Also it is found that crystallization quality for both the normal MgO and new MgO is more improved with MgO target and same oxygen dose, which means that this new method is helpful to form a new structure of MgO annealed at 400 ℃ in vacuum. with lattice constant of 0.812 nm. All of the samples were     

改性纳米MgO/PLLA复合薄膜的制备及性能

为了改善左旋聚乳酸(PLLA)的降解性,采用溶液共混法将PLLA和MgO纳米颗粒(MgO-NPs)进行复合,制备了一种具有良好力学性能的骨修复复合材料.结果显示:改性MgO纳米颗粒(g-MgO-NPs)在PLLA基体中的分散效果及界面结合性比未改性的好.4%(质量比)g-MgO-NPs的添加量使薄膜的拉伸强度从10.6 MPa增大到30.1 MPa,断裂伸长率从71%减小为59%,并使薄膜降解后的pH值趋于稳定,基本接近生理盐水的pH值.由此表明:g-MgO-NPs在一定程度上能改善聚乳酸复合膜的降解性及其力学性能.     

高温退火对MgO晶体光致发光性能的影响

利用自行搭建的实验平台,测试了高纯MgO晶体和Sc掺杂MgO晶体的紫外光光致发光(PL)光谱,发射峰值分别位于389.31、498.61nm、712.44和749.06nm,其可见光发射区和红外发射区主要对应于MgO晶体中由O空位构成的F色心和F+色心通过激发和退激发机制发射;在不同温度退火条件下测试Sc掺杂MgO晶体的PL光谱,并利用高斯分解实现了Sc掺杂MgO晶体中F色心和F+色心的定位。结果表明,高温退火处理可以有效降低MgO晶体表面的污染,进而提高晶体的光电活性;Sc掺杂导致MgO晶体可见光发射区域的蓝移和增强,其中F+色心对于温度的依赖性较强。     

Dislocation reactions,plastic anisotropy and forest strengthening in MgO at high temperature

The collective properties of dislocations in MgO are investigated in the high temperature regime and at constant strain rate with 3D Dislocation Dynamics simulations. Intersections between slip systems 1/2〈1 1 0〉{1 1 0} and 1/2〈1 1 0〉{1 0 0} allow essentially two types of junction reactions. These junctions are energetically stable and are expected to promote strong forest strengthening at high temperature. Large-scale DD simulations show that MgO strain hardening at high temperature may be dominated by forest reactions. Important parameters for dislocation density based modeling of MgO plasticity are finally calculated and verified to be consistent with experimental observations.     

Synthesis of nano-ceria powder of high thermal stability

A new method is studied for preparing nano-ceria by acid leaching MgO from CeO₂−MgO mixed powder made by calcining a gel. The MgO in the mixed powder can be leached completely with acetic acid solution at room temperature, but the CeO₂ remains unaffected. The surface area (Sg) of the resulting CeO₂ increases with Mg/Ce ratio, but approaches constant after the ratio is larger than a given value which is higher for the higher gel calcining temperature. When Mg/Ce is 8 (molar ratio) and the calcining temperature is 1253 K, the Sg of the resulting ceria remains 25.1 m²/g even after annealed at 1253 K for 4 h. In comparison with the conventional methods, CeO₂ from the new method shows higher surface area and higher thermal stability.     

Fabrication of Nd:YAG transparent ceramics with both TEOS and MgO additives

Neodymium doped YAG transparent ceramics were fabricated by vacuum reactive sintering method using commercial α-Al₂O₃, Y₂O₃ and Nd₂O₃ powders as the starting materials with both tetraethyl orthosilicate (TEOS) and MgO as sintering aids. The morphologies and microstructure of the powders and Nd:YAG transparent ceramics were investigated. Fully dense Nd:YAG ceramics with average grain size of ∼10 μm were obtained by vacuum sintering at 1780 °C for 8 h. No pores and grain-boundary phases were observed. The in-line transmittance of the ceramic was 83.8% at 1064 nm.