One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and Their Sulfur Derivatives with H2SO4 Supported on Silica Gel or Alumina

The one-pot condensation of aromatic aldehydes, β-dicarbonyl compounds, and urea or thiourea in the presence of H₂SO₄ supported on silica gel or alumina (80% m/m) in refluxing n-hexane produces 3,4-dihydropyrimidin-2(1H)-ones and their sulfur derivatives in high to excellent yields.     

Morphology-controlled electrochemical sensing amaranth at nanomolar levels using alumina

Different-shaped aluminas were readily prepared via hydrothermal reaction. It was found that the morphology and the electrochemical sensing properties of alumina were heavily dependent on the reaction time. When extending the reaction time from 6 h to 24 h, the obtained alumina samples changed from amorphous bumps to regular microfibers in diameter of 200 nm, as confirmed by scanning electron microscopy. Transmission electron microscopy observation revealed that longer reaction time was beneficial for the formation of porous and uniform fiber-like structures. Electrochemical tests proved that alumina microfibers were more active for the oxidation of amaranth and exhibited much higher enhancement effect, compared with alumina bumps. On the surface of alumina microfibers, the oxidation peak currents of amaranth increased remarkably. The influences of pH value, amount of alumina microfibers, and accumulation time on the signal enhancement of amaranth were discussed. As a result, a novel electrochemical method was developed for the detection of amaranth. The linear range was from 1 to 150 nM, and the detection limit was 0.75 nM after 1-min accumulation. The analytical application in drink samples was investigated, and the results consisted with the values that obtained by high-performance liquid chromatography.     

Dispersion of Colloidal Alumina using a Rhamnolipid Biosurfactant

Dispersability of colloidal alumina in water has been studied using a rhamnolipid containing biosurfactant. Zeta potential measurements revealed that the surface charge of alumina was altered due to adsorption of the biosurfactant and the iso‐electric‐point of alumina shifted from pH 9 to 6.3. Sedimentation tests indicated that the alumina suspension was completely dispersed for 3–5 hours in the presence of biosurfactant after which some settling was observed. Stability of the suspension in the time period studied was found to be independent of pH. Capillary suction time measurements showed that the alumina suspension was dispersed in the presence of the biosurfactant and varied with pH. Maximum dispersion is obtained in the pH range of 3.5–5 and 7–11 while a minimum is obtained around pH 6. This behavior is consistent with the changes in zeta potential in the presence of the biosurfactant and thus capillary suction time measurements appeared to be more reliable than the sedimentation tests. Optimization studies showed that about 60 mg/g of biosurfactant was necessary for best dispersion and dispersion could be done up to 40% solids. The application of a natural biosurfactant for dispersing colloidal alumina has been demonstrated.     

Ethylene Glycol as New Mobile Phase for Resolution of Two-Component Mixture of Cationic Surfactants on Alumina Surface

Aqueous ethylene glycol (ethane 1,2 diol) as a green mobile phase has been used for thin layer chromatographic (TLC) studies of cationic surfactants on alumina layers. Nineteen solvent systems were used to examine the mobility of the surfactants and to discover the best TLC system for the selective separation of dodecyl trimethylammonium bromide (DTAB) from multi-component mixture of other surfactants. Among the TLC systems studied, M₃ (ethylene glycol: water, 8:2) was best for achieving the selective separation of DTAB from multi-component mixture of other surfactants because in this mobile phase mobility of all surfactants except DTAB were insignificant. Effect of organic additives in aqueous ethylene glycol mobile phase on the mobility of surfactants was examined. The results obtained on laboratory made alumina TLC plates and commercially available precoated alumina HPTLC plates were compared. The lower limits of detection of DTAB, CPC, CTAB, HDTAC, and TTAB were 0.02, 0.05, 0.04, 0.06, or 0.08 µg per zone respectively. The resolution of mixture of cationic surfactants was also examined in the presence metal cations as an impurity in the analyzed sample.     

Ni基催化剂催化燃油重整耦合选择性催化还原NOx反应

分别以La₂O₂CO₃, CeO₂, ZrO₂和Al₂O₃为载体, 采用浸渍法制备了Ni基重整催化剂, 并以正十二烷模拟车载燃油进行催化重整反应以同时制备小分子碳氢化合物(HCs)和H₂, 考察了其在4wt%Ag/Al₂O₃上选择性催化还原(HC-SCR)氮氧化物(NO_x)的性能. 采用N₂吸附-脱附、X射线粉末衍射、H₂程序升温还原和热重等手段对Ni基催化剂进行了表征. 结果表明, 随着重整催化剂氧化还原性能增强, 产物中H₂浓度增加, 可参与SCR反应的HCs含量减少, 从而导致重整-SCR耦合体系上NO_x净化活性温度窗口向低温移动, NO_x最高转化率降低. Ni/ZrO₂+Ag/Al₂O₃耦合体系中H₂/HCs符合SCR反应所需的最优比例, 在柴油车典型排气温度范围内表现出良好的NO_x净化能力. 同时, 在Ni/ZrO₂+Ag/Al₂O₃耦合体系上考察了其燃油重整-SCR的活性稳定性. 结果显示, 重整催化剂的耐久性有待进一步提高.     

制备方法对Al2O3掺杂Pt/WO3-ZrO2催化剂上正庚烷异构化反应的影响

采用恒pH法和非恒pH法制备了Al₂O₃掺杂的Pt/WO₃/ZrO₂催化剂,并用N₂吸附-脱附、X射线衍射、紫外-可见漫反射、CO化学吸附、X射线光电子能谱、²⁷Al魔角旋转核磁共振和吡啶吸附红外等技术对催化剂进行了表征.结果表明,相比于非恒pH法制备的催化剂,恒pH法制备的催化剂具有较高的比表面积和Pt分散度,在H₂气氛中产生更多的B酸位,从而表现出更高的催化正庚烷临氢异构化反应活性; 在200℃和质量空速0.9h^-1的反应条件下,正庚烷转化率达70.0%,明显高于非恒pH法制备的催化剂(43.5%).     

复合软模板法可控制备红毛丹状AlOOH/Al2O3纳米材料

以Al(NO₃)₃为铝源,尿素为均相沉淀剂, 在聚乙二醇400(PEG4000)-DL-天冬氨酸形成的复合软模板体系中, 通过简单的常压回流方式成功合成出形貌和尺寸较为均一的红毛丹状γ-AlOOH纳米结构, 继而考察了反应物和添加剂用量对前驱体形貌和尺寸的影响, 并对γ-AlOOH纳米结构可能的形成机理进行了探讨. 实验结果表明, 所合成的红毛丹状γ-AlOOH具有球中球的核壳结构, 统计得内球直径约为400 nm, 外壳外径约为600 nm, 密集状态的壳层厚度约为15 nm, 毛刺状凸出物长度可达60 nm以上. 前驱体样品经600℃煅烧5 h后即转变为具有良好形貌继承性的γ-Al₂O₃, Brunauer-Emmett-Teller (BET) N₂-吸附实验表明其比表面积高达299.97 m²·g^-1.     

Ho3+/Yb3+共掺ZnO-Al2O3-GeO2-SiO2玻璃陶瓷的制备和上转换发光性质

综合ZnO-Al₂O₃-SiO₂系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho³⁺/Yb³⁺共掺以ZnAl₂O₄为主晶相的ZnO-Al₂O₃-GeO₂-SiO₂系玻璃陶瓷。因[GeO₄]四面体和[SiO₄]四面体都是玻璃网络形成体,讨论了GeO₂取代SiO₂对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO₂的取代量为10.55%（w/w）时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色（546 nm）和弱的红色（650 nm）上转换发光,并研究了不同Ho³⁺/Yb³⁺掺杂比对样品上转换发光的影响,最终结果表明当Ho³⁺/Yb³⁺掺杂比为1：11（n/n）时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。     

Influences of Sr2+ Doping on Microstructure,Giant Dielectric Behavior,and Non-Ohmic Properties of CaCu3Ti4O12/CaTiO3 Ceramic Composites

The microstructure, dielectric response, and nonlinear current-voltage properties of Sr²⁺-doped CaCu₃Ti₄O₁₂/CaTiO₃ (CCTO/CTO) ceramic composites, which were prepared by a solid-state reaction method using a single step from the starting nominal composition of CCTO/CTO/xSrO, were investigated. The CCTO and CTO phases were detected in the X-ray diffraction patterns. The lattice parameter increased with increasing Sr²⁺ doping concentration. The phase compositions of CCTO and CTO were confirmed by energy-dispersive X-ray spectroscopy with elemental mapping in the sintered ceramics. It can be confirmed that most of the Sr²⁺ ions substituted into the CTO phase, while some minor portion substituted into the CCTO phase. Furthermore, small segregation of Cu-rich was observed along the grain boundaries. The dielectric permittivity of the CCTO/CTO composite slightly decreased by doping with Sr²⁺, while the loss tangent was greatly reduced. Furthermore, the dielectric properties in a high-temperature range of the Sr²⁺-doped CCTO/CTO ceramic composites can be improved. Interestingly, the nonlinear electrical properties of the Sr²⁺-doped CCTO/CTO ceramic composites were significantly enhanced. The improved dielectric and nonlinear electrical properties of the Sr²⁺-doped CCTO/CTO ceramic composites were explained by the enhancement of the electrical properties of the internal interfaces.     

Small-scale fracture toughness of ceramic thin films: the effects of specimen geometry,ion beam notching and high temperature on chromium nitride toughness evaluation

For the implementation of thin ceramic hard coatings into intensive application environments, the fracture toughness is a particularly important material design parameter. Characterisation of the fracture toughness of small-scale specimens has been a topic of great debate, due to size effects, plasticity, residual stress effects and the influence of ion penetration from the sample fabrication process. In this work, several different small-scale fracture toughness geometries (single-beam cantilever, double-beam cantilever and micro-pillar splitting) were compared, fabricated from a thin physical vapour-deposited ceramic film using a focused ion beam source, and then the effect of the gallium-milled notch on mode I toughness quantification investigated. It was found that notching using a focused gallium source influences small-scale toughness measurements and can lead to an overestimation of the fracture toughness values for chromium nitride (CrN) thin films. The effects of gallium ion irradiation were further studied by performing the first small-scale high-temperature toughness measurements within the scanning electron microscope, with the consequence that annealing at high temperatures allows for diffusion of the gallium to grain boundaries promoting embrittlement in small-scale CrN samples. This work highlights the sensitivity of some materials to gallium ion penetration effects, and the profound effect that it can have on fracture toughness evaluation.