低温燃烧合成Ce0.8Y0.2O1.9固溶体及烧结性能的研究

以硝酸盐做氧化剂,柠檬酸为燃料,采用低温燃烧法制备纳米级超细Ce0.8Y0.2O1.9 (YDC)固溶体.利用TG-DSC,XRD,SEM,FT-IR和BET等手段对凝胶前驱体的热分解行为、相转化过程和YDC粉体的性能进行表征.TG-DSC结果表明,柠檬酸-硝酸盐干凝胶的点火温度约为263.3℃;经XRD测试,粉体经600℃焙烧即形成了单相立方萤石型结构的固溶体,晶粒度为16 ～23nm.柠檬酸与硝酸盐摩尔比(CA/N)对粉体的微观形貌、比表面积和烧结活性有显著影响.当CA/N为1.5∶1时,粉体粒子间仅有微弱的软团聚,将素坯在1400℃烧结2h,得到相对密度为95.6％,平均粒径约为0.7 μm的陶瓷烧结体.     

掺杂F-,Sr2+的氧化铈紫外屏蔽和氧化催化性研究

采用沉淀法合成F-,Sr2+单掺杂和共掺杂的氧化铈,探讨了不同掺杂离子对氧化铈紫外屏蔽性能和氧化催化性能的影响.XRD结果表明,F-,Sr2+单掺杂或共掺杂的CeO2均为立方萤石结构,但衍射峰因掺杂离子的不同而稍有偏移.UV-Vis光谱表明,F-,Sr2+单掺杂和共掺杂的氧化铈的紫外屏蔽性能均优于纯氧化铈.共掺杂氟锶后的氧化铈的氧化催化性明显比纯氧化铈的弱,但是,单掺杂氟离子或锶离子的氧化铈的氧化催化性比纯氧化铈的强.     

Pt/CeO2-ZrO2变换催化剂的制备、表征与性能

 用共沉淀法制备了不同Ce/Zr比的CeO2-ZrO2复合氧化物,用浸渍法制备了Pt/CeO2-ZrO2水煤气变换催化剂,并对该催化剂进行了活性评价. 结果表明,与传统的Cu基低变催化剂相比,该催化剂具有操作温度范围宽和抗氧化冲击等优点,具有应用于车载重整制氢过程的潜力. 考察了温度、空速和汽/气比等条件对催化剂活性的影响,对催化剂的制备参数和工艺参数进行了研究. 结果表明,不同Ce/Zr比的Pt/CeO2-ZrO2催化剂的活性相差很大,其中Pt/Ce0.8Zr0.2O2变换催化剂活性最高. XRD结果表明,制备的Pt/Ce0.8Zr0.2O2形成了固溶体. 通过增加单位质量催化剂表面的Pt原子数可提高催化剂的活性.     

CeO2-La2O3/γ-Al2O3催化还原SO2反应机理的研究

 采用浸渍法制备了负载型CeO2/γ-Al2O3,La2O3/γ-Al2O3和CeO2-La2O3/γ-Al2O3催化剂,并用XRD和XPS对催化剂进行了表征,在n(SO2)/n(CO)=1/3,载流气体为N2,气体流量为1 L/min,催化剂用量为15 g的条件下,考察了催化剂催化CO还原SO2反应的性能,研究了催化剂的活化过程、催化活性和反应物配比对活性的影响. 结果表明,CeO2-La2O3/γ-Al2O3在催化还原SO2反应中的活化温度比单组分催化剂CeO2/γ-Al2O3或La2O3/γ-Al2O3下降了50~100 ℃,而且具有更高的活性. 这可以解释为由CeO2的redox反应与La2O3的COS中间物反应之间的协同作用所致. 还对SO2还原反应机理进行了探讨,发现CeO2的redox反应所生成的单质硫是整个过程中COS中间物反应的重要来源. 在此基础上,对CeO2-La2O3/γ-Al2O3催化CO还原SO2反应提出了redox-COS叠加反应机理.     

Electron stimulated desorption of O2 from gadolinia-doped ceria surfaces

The interactions of gas phase oxygen with gadolinia-doped ceria (GDC) surfaces are investigated by electron stimulated desorption (ESD). The primary desorbed cationic species related to molecular oxygen adsorption is O₂⁺. The threshold energy for ESD of O₂⁺ is 13–14 eV, indicating electron impact ionization of molecular oxygen bound at oxygen vacancies. Dependence of O₂⁺ velocities upon incident electron energy and substrate temperature reveals the dominant influence of the effective charge of the adsorption complex. The O₂⁺ velocity distribution is bimodal, and the onset of the faster components at room temperature is related to the balance between fluxes of incident electrons and secondary electron emission, causing effective hole production and neutralization of trapped electrons at surface states.     

Au/Ce1-xZrxO2催化剂的制备、表征及其在CO氧化和水煤气变换反应中的催化性能

采用共沉淀法制备了不同锆铈摩尔比的Ce1-xZrxO2(x=0,0.1,0.3,0.5,0.7,0.9和1.0)氧化物,并以改性的浸渍法制备了金担载量为1%(质量分数)的Au/Ce1-xZrxO2催化剂.考察了催化剂在低温CO氧化和水煤气变换反应中的催化性能.应用氮物理吸附、X射线衍射、透射电镜和H2程序升温还原等技术对氧化物载体及其负载金催化剂进行了表征,并与其催化性能进行了关联.结果表明,与纯CeO2和ZrO2相比,Ce1-xZrxO2的比表面积增大而孔径减小,孔分布更加集中.Zr的加入使表面Ce4 的还原更加困难,使体相Ce4 的还原更加容易.活性组分金的加入有利于铈锆氧化物的还原.ZrO2载体较大的孔径使金在载体表面分散均匀而粒子较小,因此与Au/CeO2和Au/Ce1-xZrxO2相比,Au/ZrO2具有更好的低温CO氧化活性和水煤气变换活性,而Au/CeZrO在高温下的水煤气变换反应中表现出更好的催化性能.     

Nano-Size Characterization and Antifungal Evaluation of Essential Oil Molecules-Loaded Nanoliposomes

Nanoliposomes, bilayer vesicles at the nanoscale, are becoming popular because of their safety, patient compliance, high entrapment efficiency, and prompt action. Several notable biological activities of natural essential oils (EOs), including fungal inhibition, are of supreme interest. As developed, multi-compositional nanoliposomes loaded with various concentrations of clove essential oil (CEO) and tea tree oil (TTO) were thoroughly characterized to gain insight into their nano-size distribution. The present work also aimed to reconnoiter the sustainable synthesis conditions to estimate the efficacy of EOs in bulk and EO-loaded nanoliposomes with multi-functional entities. Following a detailed nano-size characterization of in-house fabricated EO-loaded nanoliposomes, the antifungal efficacy was tested by executing the mycelial growth inhibition (MGI) test using Trichophyton rubrum fungi as a test model. The dynamic light scattering (DLS) profile of as-fabricated EO-loaded nanoliposomes revealed the mean size, polydispersity index (PdI), and zeta potential values as 37.12 ± 1.23 nm, 0.377 ± 0.007, and −36.94 ± 0.36 mV, respectively. The sphere-shaped morphology of CEO and TTO-loaded nanoliposomes was confirmed by a scanning electron microscope (SEM). The existence of characteristic functional bands in all tested counterparts was demonstrated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Compared to TTO-loaded nanoliposomes, the CEO-loaded nanoliposomes exhibited a maximum entrapment efficacy of 91.57 ± 2.5%. The CEO-loaded nanoliposome fraction, prepared using 1.5 µL/mL concentration, showed the highest MGI of 98.4 ± 0.87% tested against T. rubrum strains compared to the rest of the formulations.