La2O3掺杂SiO2-B2O3-Nb2O5复相微晶玻璃相界及储能性能研究

采用可控析晶法制备了La₂O₃掺杂的SiO₂-B₂O₃-Nb₂O₅ (SBN)复相微晶玻璃,利用DSC、Raman、XRD、SEM、铁电和介电性能测试等分析表征了La₂O₃掺杂对SBN复相微晶玻璃结构与储能性能的影响。结果表明:La₂O₃掺杂能够有效提高复相微晶玻璃的热稳定性,随着La₂O₃含量增加,系统析晶势垒增大,热膨胀系数先降低后升高,价键振动加剧,介电常数先增大后减小,介电损耗先减小后增大;掺杂1.00%(摩尔分数)La₂O₃时,复相微晶玻璃在40 kV/cm电场下的储能密度和储能效率最大,分别为0.031 J·cm^-3和77.6%;储能性能主要通过介电常数和击穿场强的协同作用来评价,La₂O₃能通过提高结构热稳定性和降低介电损耗来提高介电常数,当其引入体系后处于玻璃网络的空隙中,可有效增强材料耐击穿性能;复相微晶玻璃结构可以增加结构无序度,从而降低弛豫损耗,有效提高材料的储能性能。     

固相法制备掺杂型高色度CoxM1-xAl2O4/高岭土复合颜料

为了制备低成本、高色度的钴蓝颜料,本文以高岭土为载体,以Al₂O₃和Co₃O₄为主要原料,通过引入ZnO、CaO及MgO不同金属氧化物,采用固相法制备了高色度(Co_xM_1-xAl₂O₄)/高岭土复合颜料(M为Ca²⁺、Mg²⁺或Zn²⁺)。系统考察了研磨时间、煅烧温度、煅烧时间和不同金属氧化物掺量对复合颜料呈色性能的影响规律。研究表明,在煅烧温度1 200 ℃、研磨时间12 h和n(Co²⁺)/n(M²⁺)为3:2时,制得的复合颜料具有最好的呈色性能(L^*=53.68,a^*=7.58,b^*=-62.89)。同时,引入不同的金属元素,可实现对复合颜料颜色的调控,引入Ca²⁺后,所制备的Co_xCa_1-xAl₂O₄复合颜料偏红相,而引入Zn²⁺后,所制备的Co_xZn_1-xAl₂O₄复合颜料偏绿相。通过相关表征,提出了复合颜料的呈色机理,在颜料制备过程中,引入与Co²⁺离子半径接近的Mg²⁺或Zn²⁺,Mg²⁺或Zn²⁺可进入CoAl₂O₄的四面体配位中,部分替代Co²⁺,形成MgAl₂O₄-CoAl₂O₄或ZnAl₂O₄-CoAl₂O₄的固溶体,而引入离子半径较大的Ca²⁺,形成CaAl₂O₄和CoAl₂O₄的均相混合物。最后,将制得复合颜料应用到有机硅耐热涂料中,可以明显提高有机硅涂料的热稳定性。     

Fe2O3对铜尾矿基CaO-MgO-Al2O3-SiO2微晶玻璃析晶行为的影响

以铜尾矿为主要原料,通过熔融法制备CaO-MgO-Al₂O₃-SiO₂(CMAS)微晶玻璃,并外掺Fe₂O₃晶核剂对细粒级铜尾矿基CMAS微晶玻璃析晶行为进行优化。利用DSC、XRD和SEM等手段研究了晶核剂用量对细粒级铜尾矿基CMAS微晶玻璃析晶行为和物理性能的影响,借助Ozawa-Chen法拟合计算了析晶动力学参数。结果表明,外掺Fe₂O₃晶核剂用量大于3.72%(质量分数)时,细粒级铜尾矿制备的微晶玻璃可以实现整体析晶。辉石相的析出是玻璃相中的Fe、Mg元素进入[Si(Al)O₄] 四面体晶格配位的结果,Fe³⁺的增加有利于辉石相的析出并降低了析晶活化能,外掺Fe₂O₃晶核剂能够较好地优化细粒级铜尾矿基微晶玻璃的析晶行为和力学性能。     

CaO-B2O3-SiO2微晶玻璃的制备及介电性能

低介电常数、低介电损耗的微晶玻璃是制造低温共烧陶瓷基板的重要材料。本文采用熔融水淬法制备了CaO-B₂O₃-SiO₂(CBS)微晶玻璃,重点研究了m(CaO)/m(SiO₂)质量比、B₂O₃含量对CBS微晶玻璃介电性能的影响。结果表明：CBS微晶玻璃的主要晶相有Ca₃Si₃O₉、Ca₂B₂O₅、CaB₂O₄、SiO₂和Ca₂SiO₄。随着m(CaO)/m(SiO₂)质量比的增加,介电常数增加,介电损耗先降低后增加;硅灰石相的增多使介电损耗从2.87×10^-3降到1.36×10^-3,介电损耗随着SiO₂、Ca₂B...     

晶化温度对MgO-Al2O3-SiO2系尖晶石微晶玻璃结构与性能的影响

采用熔融法制备了MgO-Al₂O₃-SiO₂系微晶玻璃,利用DSC、XRD、SEM等表征手段研究了晶化温度对微晶玻璃结构与性能的影响。结果表明,晶化温度为860℃时,有尖晶石晶体析出。晶化温度为1037℃、1080℃时,主晶相为尖晶石,次晶相为二钛酸镁和钛酸锆,随着晶化温度的升高,晶相含量增多,晶粒尺寸增加。晶化温度为1120℃时,主晶相仍为尖晶石,次晶相为金红石、钛酸锆。在1080℃晶化2 h后的微晶玻璃具有最佳的综合性能,其显微硬度为8.59 GPa,抗弯强度为146.0 MPa,热膨胀系数6.05×10^-6/K,密度为2.760 g/cm³。     

MgAl2O4:Ce荧光粉辐照合成及发光机理研究

通过伽马射线辐照辅助聚丙烯酰胺凝胶法合成了MgAl₂O₄和MgAl₂O₄:Ce荧光粉。通过X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、紫外可见分光光度计和荧光分光光度计研究了MgAl₂O₄:Ce荧光粉的晶体结构、表面形貌、光学性质和发光性质;基于实验所获得的结果,分析了纳米级MgAl₂O₄:Ce荧光粉的发光机理。实验结果表明:采用伽马射线辐照辅助聚丙烯酰胺凝胶法制备纯相MgAl₂O₄和MgAl₂O₄:Ce荧光粉的结晶温度要比传统聚丙烯酰胺凝胶法低100 ℃左右;MgAl₂O₄:Ce荧光粉的平均颗粒尺寸为14 nm,Ce离子掺杂后导致样品颗粒细化;Ce离子的掺入,降低了MgAl₂O₄的能带值,改善了其颜色性质和发光性质;当采用275 nm的光去激发MgAl₂O₄:Ce荧光粉时,获得了425 nm和464 nm的蓝光发射。通过能量传递原理分析认为,杂质缺陷（Ce³⁺）在整个发光过程中扮演了重要角色。MgAl₂O₄:Ce作为一种抗辐射能力强的荧光粉,在空间照明领域具有很好的应用前景。     

晶核剂对透明堇青石微晶玻璃析晶与性能的影响

采用熔融法制备了含有不同晶核剂的非化学计量比堇青石微晶玻璃，通过DSC、XRD、FE-SEM、UV-VIS-NIR等测试方法研究了不同晶核剂对微晶玻璃析晶与性能的影响，并用经典动力学方程(Johnson-Mehl-Avrami)分析了微晶玻璃的析晶动力学。结果表明，以P₂O₅和P₂O₅+ZrO₂为晶核剂的微晶玻璃晶化机制均为表面晶化，而以P₂O₅+ZrO₂+TiO₂为晶核剂的微晶玻璃则倾向于整体析晶。三组微晶玻璃在950℃晶化时主晶相为μ-cordierite,当温度升高到980℃时开始转变为α-cordierite,引入TiO₂使α-cordierite的含量增加，析出的晶体更加复杂致密。随着晶化时间延长，与其他晶核剂相比，P₂O₅+ZrO₂+TiO₂组合晶核剂微晶玻璃在相同晶化时...     

Na2O对固体氧化物燃料电池用透辉石封接微晶玻璃性能的影响

本文设计和制备了以透辉石为主晶相的R₂O-RO-Al₂O₃-B₂O₃-SiO₂系封接微晶玻璃,用于固体氧化物燃料电池(SOFC)的封接,研究了Na₂O含量(0%～10%,摩尔分数)对封接玻璃热膨胀系数(CTE)、析晶与烧结润湿特性的影响,表征了封接件在高温长时间热处理后玻璃与SUS403不锈钢的封接界面。结果表明,Na₂O可以显著改善玻璃的热性能,所制备的玻璃样品在封接温度范围内经热处理后可获得主晶相为透辉石(CaMgSi₂O₆)的微晶玻璃。随着Na₂O含量增加,主晶相透辉石的晶相含量不同,微晶玻璃的热膨胀系数由未晶化前的8.22×10^-6 K^-1提升至11.79×10^-6 K^-1,能够满足SOFC封装的热膨胀匹配。当Na₂O含量大于等于8...     

Ni2+掺杂对MgCr2O4材料红外辐射性能的影响

开发高发射率红外辐射材料是高温窑炉节能的重要方向。本工作采用高温固相反应工艺制备Ni²⁺掺杂MgCr₂O₄材料,研究了Ni²⁺掺杂量摩尔分数对MgCr₂O₄材料红外辐射性能的影响,探讨了影响MgCr₂O₄材料红外发射率的机理。结果表明,Ni²⁺能掺杂进入MgCr₂O₄材料晶格,所制备的Mg_1–x Ni_xCr₂O₄(0.1≤x≤0.5)材料产生了晶格畸变,少量Ni²⁺价态发生转变;同时,随着Ni²⁺掺杂量增加,氧空位浓度的增大,禁带宽度减小,所制备材料在近中红外波段的发射率均有提高。x=0.5的材料(Mg_0.5Ni_0.5Cr₂O₄)在...     

不同Al2O3/SiO2比的MgO-Al2O3-SiO2微晶玻璃制备及性能研究

本文采用烧结法制备MgO-Al₂O₃-SiO₂(MAS)微晶玻璃，研究不同Al₂O₃/SiO₂质量比对MAS微晶玻璃的微观结构和理化性能的影响，采用X射线衍射、差热分析、红外光谱、扫描电子显微镜对基础玻璃与微晶玻璃的结构和表面形貌进行表征，并对微晶玻璃的密度、力学性能、耐蚀性、热学性能和介电性能进行测试分析。结果表明：随着Al₂O₃/SiO₂质量比从0.52增大至0.64,基础玻璃的玻璃化转变温度T_g增大、析晶峰值温度T_p减小，促使样品析出α-堇青石晶相；样品密度在2.52～2.60 g/cm³波动，介电常数ε_r由1.73增加到4.51,热膨胀系数由4.46×10^-6℃^-1降低到2.38×10^-6℃^-1,介电损耗tan...     

Zinc doping effect on the optical bands of cr3 in LiNbO3: Zn, Cr crystals

The optical absorption and luminescence of Cr³⁺ ions in ZnO doped LiNbO₃:Cr³⁺ crystals have been studied. It has been found that ZnO produces the same effect as that observed in MgO co-doped samples: A strong reduction in the Cr³⁺ concentration together with a shift in the ⁴A₂ → ⁴T₁ vibronic transition to lower energy. As in the case of MgO co-doped samples a new Cr³⁺ centre is formed in ZnO co-doped samples.     

1700℃流动氮气下金属铝–镁铝尖晶石复合材料的物相组成与反应机理(英文)

研究了高纯氮气下先后进行580℃保温8 h、1 700℃保温3 h热处理后Al–MgAl₂O₄复合材料的物相组成和反应机理。结果表明:经580℃保温8 h后,Al–MgAl₂O₄复合材料形成分层现象,即外层区含金属铝–氮化铝壳核结构。当温度升至某一特定值时,金属铝–氮化铝壳核结构破裂,金属铝Al(l/g)溢出/逸出,与N₂和O₂分别反应生成AlN和Al₂O(g),促进化学计量比的镁铝尖晶石(MgAl₂O₄)分解形成富氧化铝的镁铝尖晶石(Al₂O₃-rich spinel)和镁蒸气(Mg(g))。一方面,AlN与富氧化铝的镁铝尖晶石形成MgAlON尖晶石;另一方面,AlN与Mg(g)和O₂发生固溶体反应生成氮化铝固溶体,(Mg,Al)(N,O)。内层区的材料物相组成不同于外层区,含有许多由气–气反应Al₂O(g)+O₂(g)+N₂(g)+Mg(g)→MgAlON(s)或Al(g)+O₂(g)+N₂(g)+Mg(g)→MgAlON(s)生成的片状MgAlON;此外,内层区富氧化铝的镁铝尖晶石没有进一步转变为MgAlON尖晶石。     

Catalytic decomposition of N2O over CeO2 promoted Co3O4 spinel catalyst

A series of CeO₂ promoted cobalt spinel catalysts were prepared by the co-precipitation method and tested for the decomposition of nitrous oxide (N₂O). Addition of CeO₂ to Co₃O₄ led to an improvement in the catalytic activity for N₂O decomposition. The catalyst was most active when the molar ratio of Ce/Co was around 0.05. Complete N₂O conversion could be attained over the CoCe0.05 catalyst below 400 °C even in the presence of O₂, H₂O or NO. Methods of XRD, FE-SEM, BET, XPS, H₂-TPR and O₂-TPD were used to characterize these catalysts. The analytical results indicated that the addition of CeO₂ could increase the surface area of Co₃O₄, and then improve the reduction of Co³⁺ to Co²⁺ by facilitating the desorption of adsorbed oxygen species, which is the rate-determining step of the N₂O decomposition over cobalt spinel catalyst. We conclude that these effects, caused by the addition of CeO₂, are responsible for the enhancement of catalytic activity of Co₃O₄.     

Computational spectroscopy and DFT investigations into nitrogen and oxygen bond breaking and bond making processes in model deNOx and deN2O reactions

Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for analysis of the NO bond breaking and NN and OO bond making in the context of deNO_x and deN₂O reactions. Interaction of NO, N₂O and NO₂ with cationic (transition metals) and anionic (surface O²⁻ ions) centers was explored at the molecular level. The elementary events such as reactant coordination, charge and spin redistributions, which are principal molecular constraints for efficient decomposition of the nitrogen oxides (N₂O and NO) were discussed. Particular attention was paid to dynamics of the NO bond cleavage in N₂O molecule through electron and oxygen atom transfer routes, evaluation of preferable coordination modes of NO, discrimination between inner- and outer-sphere mechanism of NN bond formation, and the influence of spin and electronic redistribution on the reaction course (spin catalysis). Owing to their simplicity and well known surface chemistry, model systems selected for studies of such processes include MoO_x/SiO₂, MgO and ZSM-5 zeolite exchanged with various transition metal ions (TMI) of different electron configuration and spin multiplicity: Mo⁵⁺ (d¹, ²D) Fe³⁺, Mn²⁺, Cr⁺ (d⁵, ⁶S), Fe²⁺ (d⁶, ⁵D), Co²⁺ (d⁷, ⁴F), Ni²⁺ (d⁸, ³F), Cu²⁺ (d⁹, ²D) and Cu⁺, Zn²⁺ (d¹⁰, ¹S).     

Potassium-doped Co3O4 catalyst for direct decomposition of N2O

Direct decomposition of nitrous oxide (N₂O) on K-doped Co₃O₄ catalysts was examined. The K-doped Co₃O₄ catalyst showed a high activity even in the presence of water. In the durability test of the K-doped Co₃O₄ catalyst, the activity was maintained at least for 12 h. It was found that the activity of the K-doped Co₃O₄ catalyst strongly depended on the amount of K in the catalyst. In order to reveal the role of the K component on the catalytic activity, the catalyst was characterized by XRD, XPS, TPR and TPD. The results suggested that regeneration of the Co²⁺ species from the Co³⁺ species formed by oxidation of Co²⁺ with the oxygen atoms formed by N₂O decomposition was promoted by the addition of K to the Co₃O₄ catalyst.     

Effect op the preparation conditions on the reducibility of Cu-Co based oxides

The nature of the active sites of Cu-Co-Al Catalysts used to convert synthesis gas to methanol and higher alcohols is still a matter of debate. The main difficulty to discern the nature of the synergism responsible for alcohol formation is related to the Co reducibility under reaction conditions. In this paper we studied the influence of the preparation conditions on the reducibility of Co. Binary Cu-Co, Cu-Al and Co-Al, and ternary Cu-Co-Al samples were prepared by coprecipitation and characterized by temperature-programmed reduction. X-ray powder diffraction and diffuse reflectance spectroscopy techniques. Depending on the Co/Al ratio and calcination atmosphere, the Co ions were present in three different phases before H₂ activation: CuCoO₂, GO₃O₄ and partly inverse CoAl₂O₄ spinel. The Co reducibility was in the order CuCoO₂ > Co₃O₄ > Co_oh ions in CoAl₂O₄ > Co_td ions in CoAl₂O₄. In all the cases, the presence of Cu activated the reduction of Co²⁺ and Co³⁺ ions. The mixed oxides obtained in nitrogen did not contain CO₃O₄ and the CuCoO₂ phase was formed only when the Co/Al atomic ratio was greater than 0.5. The samples calcined in air contained CO₃O₄ but not CuCoO₂. All the samples contained CoAl₂O₄, spinel phase with finely dispersed CuO. It was found that the preparative procedures and the chemical composition of the samples greatly Influence the reducibility of Co ions, thereby determining the kind of Cu-Co interaction.     

Co3O4 with ordered pore structure derived from wood vessels for efficient Hg0 oxidation

Catalytic oxidation of Hgo to Hg^O is an efficient way to remove Hg⁰ from coal-fired flue gas.The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg⁰ oxidation efficiency.Therefore,in the present work,wood vessels were used as sacrificial template to obtain Co₃O₄with ordered pore structure.SEM and BET results show that,when the mass concentrations of Co(NO₃)₂·6H₂O wa...     

SrFe0.6Co0.4O3催化降解孔雀石绿的研究

具有复杂分子结构的三苯甲烷类染料孔雀石绿是一种典型的较难降解染料,是工业废水处理的难点之一。本文根据Goldschmidt半径容差规则法,设计了用于孔雀石绿降解的ABO₃型SrFe_(1-x)Co_xO₃催化剂,并选择出活性较高的SrFe_0.6Co_0.4O₃催化剂。通过XRD、SEM、BET吸附及XPS分析表明:该催化剂是纯净钙钛矿结构,颗粒形貌为无规则堆叠的“蜂窝”片状;吸附等温线没有明显的回滞环,说明没有“墨水瓶”类孔结构;XPS谱中,B位离子同时存在Fe²⁺/Fe³⁺和Co²⁺/Co³⁺ 4种价态离子,且反应前后,4种离子的分布比例有较大变化。根据实验结果,推测该催化反应机理为:催化剂B位Co³⁺与溶解氧形成活性氧[O₂]⁺和Co²⁺;活性氧[O₂]⁺完成氧化反应后其正电荷转移到B位Fe²⁺上形成Fe³⁺,Fe³⁺的正电荷可再转移到Co²⁺形成Co³⁺,完成催化过程的电荷转移与循环。