TiO2-Al2O3载体的制备方法对其负载的磷化镍催化剂加氢脱氮反应性能的影响

采用共沉淀法和原位溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体,其负载的磷化镍催化剂采用等体积浸渍法和H₂原位还原法制备. 通过N₂吸附（BET）、X射线衍射（XRD）、透射电镜（TEM）、程序升温还原（TPR）,X射线光电子能谱（XPS）和等离子体发射光谱（ICP-AES）表征技术对催化剂进行了表征,并通过喹啉的加氢脱氮反应评价了催化剂的加氢脱氮性能. 结果表明,原位溶胶-凝胶法制成的复合载体基本保留了原有的γ-Al₂O₃的孔特征,具有较大的比表面积和较宽的孔分布,TiO₂主要以表面富集的形式分散在管状的γ-Al₂O₃表面,其负载的磷化镍催化剂还原后所形成的活性相为Ni₂P和Ni₁₂P₅;而共沉淀法制成的复合载体比表面积较小,孔径分布更加集中,TiO₂趋于在块状的Al₂O₃表面均匀分散,其负载的磷化镍催化剂具有更好的可还原性,还原后所形成的活性相为Ni₂P. 不同的载体制备方法和不同的钛铝比对催化剂加氢脱氮性能影响较大,当n（Ti）/n（Al）=1/8时,共沉淀法载体负载的催化剂表现出最佳的加氢脱氮性能,在340 ℃,3 MPa,氢油体积比500,液时空速3 h^-1的反应条件下,喹啉的脱氮率可以达到91.3%.     

铬离子掺杂对LiFePO4电化学性能的影响

采用机械球磨和共沉淀的方法合成了两种Cr3＋掺杂的LiFePO4. 通过对合成样品的XRD、SEM及其电化学性能（循环性能、大电流放电性能）的研究表明，少量Cr3＋的掺杂未影响到LiFePO4的晶体结构，但显著改善了它的电化学性能，在低放电倍率（0.1 C）时，机械球磨掺杂和共沉淀掺杂Cr3＋的LiFePO4的放电容量分别为144和158 mAh•g－1，而当放电倍率提高到2 C时，两种掺杂的LiFePO4仍分别具有110和130 mAh•g－1的放电容量，且循环性能良好.同时表明通过铁源共沉淀掺杂是一条改善离子掺杂效果的有效途径.     

有序介孔碳负载NiCo2O4电极的制备及其超电容性能

以有序介孔碳(OMC)为载体,采用共沉淀法制备了OMC/NiCo2O4复合物.用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱和透射电镜(TEM)研究其结构与形貌,发现NiCo2O4纳米颗粒均匀地负载在有序介孔碳上.循环伏安和恒流充放电测试表明,NiCo2O4质量分数为40%时,在1A·g-1的电流密度下,复合物电极的比电容可以达到577.0F·g-1,电流密度为8A·g-1时,比电容可以达到470.8F·g-1,并具有良好的循环稳定性.在2A·g-1的电流密度下,经过2000次循环后,比电容还可达到508.4F·g-1,电容保持率为92.7%.     

Synthesis and characterization of chitosan-hydroxyapatite composite for bone graft applications

In the current work chitosan-hydroxyapatite composites were synthesized using the method of co-precipitation for bone grafting. The composite samples were characterized using SEM, EDS and UTM. The composites showed a good Ca:P ratio of 2.10, indicating a sufficient level of osteoconductive of the composites. The EDS peaks showed a strong presence of carbon, oxygen, calcium and phosphorous with insignificant impurities. The UTM tests revealed compressive modulus of 80 ?MPa desired for various human bones. Also, grey rational analysis was used to optimize the process parameters. The results thus obtained show an improvement over previously reported results of bone grafts using other materials and procedures. Thus, the work can serve as a viable alternative to traditional bone grafting techniques, such as allografts and autografts, which face problems of biocompatibility and affordability.     

Effect of Nd substitution on structural and electrical properties of nanocrystalline zinc ferrite

Polycrystalline soft ferrite samples with general formula ZnNd_xFe_2−xO₄ (where x=0, 0.01, 0.02 and 0.03) were synthesized by oxalate co-precipitation method. The samples were characterized by XRD and SEM techniques. The single phase cubic spinel structure of all the samples was confirmed by XRD. The lattice constant and grain size of the samples are found to decrease with increase in Nd³⁺ content. Room temperature DC resistivity of the Nd³⁺ substituted zinc ferrites is 10² times higher than that of zinc ferrite. The dielectric constant (ε′) and dielectric loss (tan δ) of all the samples were measured in the frequency range 20 Hz-1 MHz. The dielectric behaviour is attributed to the Maxwell-Wagner type interfacial polarization. The dielectric loss of the samples is found to decrease with increase in Nd³⁺ content. High resistivity and low dielectric loss makes these ferrites particularly suitable for high frequency applications.     

Comparative studies on the structure and electromagnetic properties of Ni−Zn ferrites prepared via co-precipitation and conventional ceramic processing routes

The magnetic and physical properties of ferrites are very sensitive to microstructure, which in turn critically depends on the manufacturing process. In this study, nickel zinc ferrite powder with composition Ni_0.8Zn_0.2Fe₂O₄ has been prepared via conventional ceramic processing and co-precipitation methods. The toroidal and pellet form samples were sintered at various temperatures such as 1100, 1200 and 1300 °C. The microstructure, magnetic and dielectric properties of both samples were studied. The X-ray diffraction patterns confirm the formation of single-phase cubic spinel structure for the co-precipitation technique after sintering. The microstructure studies of Ni_0.8Zn_0.2Fe₂O₄ show the grain size increases and the porosity decreases with temperature for both methods. The controlled permeability with small loss and wide operational frequency range are found in the co-precipitation samples. Dielectric constants decrease with increase of frequency and increase with sintering temperature in both methods. Consequently, the homogenous microstructure with the low-loss high-performance of nickel zinc ferrite has been discovered by means of co-precipitation method.     

稀土离子共掺杂的钼酸钙发光材料的合成与光谱性质

采用了化学共沉淀法合成了一系列的镨、铽共掺杂的钼酸钙发光材料,研究了单掺Pr~(3+)和Tb~(3+)以及CaMoO4∶0.03Pr~(3+),yTb~(3+)共掺杂的浓度、温度对材料发光性能的影响。采用X射线衍射仪(XRD)和荧光光谱对样品进行了晶格结构、荧光性质表征。XRD分析表明:样品的主衍射峰与标准卡片(JCPDS 29-0351的衍射峰数据一致,说明少量Pr~(3+)掺杂没有改变基质晶格结构。荧光光谱分析表明,样品在275nm紫外光激发下,发射光谱主要包括多个发射峰,波长为488,560,621和652nm,分别对应于镨离子的~3P_0-~3H_4,~3P_0-~3H_5,~1D_2-~3H_4和~3P_0-~3F_2的跃迁,在掺杂量为3%时,样品特征发射峰最强,CaMoO4∶0.03Pr~(3+)和CaMoO4∶0.05Tb~(3+)的最佳煅烧温度分别为800和600℃。随着Pr~(3+)和Tb~(3+)掺入量的增加,CaMoO4∶Pr~(3+)发光材料的特征发射光谱和激发光谱的特征峰强度逐渐减小,而CaMoO4∶Tb~(3+)材料发光先减小后增大,存在着浓度猝灭效应。此外,在CaMoO4∶0.03Pr~(3+),yTb~(3+)发光体系中,Tb~(3+)的共掺杂可显著增强镨离子的特征发射峰,这是由于存在Tb~(3+)→Pr~(3+)的有效的能量传递。     

Electrospinning fabrication of rime-like NiO nanowires/nanofibers hierarchical architectures and their photocatalytic properties

Rime-like NiO Nanowires/nanofibers hierarchical architectures have been fabricated employing a co-precipitation reaction and electrospinning method. The synthesized hierarchical structure was characterized using SEM, XRD and BET analysis methods. The effects of growth temperature and reaction time on the morphologies of the as-prepared structures were investigated by SEM characterization and a possible mechanism for the formation of NiO hierarchical structures is proposed. Based on the nitrogen adsorption and desorption measurements, the BET surface area of the as-obtained sample is 61.0 m²/g and the pore sizes of ca. 5.0 nm. The catalytic efficiency of the NiO nanomaterials developed was evaluated by the photocatalytic degradation of acetaldehyde. In comparison with sphere-like and fiber-like structures, the NiO hierarchical structures show an excellent ability to rapidly acetaldehyde pollutant, which may be attributed to its unique hierarchical and porous surface structures.     

共沉淀法合成Sm3+掺杂的Sr2CeO4的荧光光谱

以（NH4）2C2O4为沉淀剂，用Sr，Ce和Sm的硝酸盐为反应物，制备了Sr2CeO4：Sm的前驱体。将此前驱体烧结后，得到了Sm掺杂的Sr2CeO4白色荧光材料。其荧光光谱强度与烧结温度和Sm^3＋的掺杂浓度密切相关，当烧结温度为1050℃以及Sm^3＋的掺杂浓度为1mol％时，峰值为470nm的宽带以及Sm^3＋在608和654nm的线谱发射最强。同直接在高温固相反应下得到的样品进行比较，其发射光谱强度大大提高。     

磁性纳米复合氧化物固体酸催化剂的制备及酯化性能

固体酸催化剂的无腐蚀、环境友好和可循环使用等特点使其成为无机液体酸的最佳替代物.磁性纳米固体酸具有优于常规固体酸催化剂的催化活性及分离简单的特性.用共沉淀法分别合成了一系列三组分TiO2-Al2O3-Fe3O4(TAF)和CeO2-Al2O3-Fe3O4(CAF)及四组分ZrO2--Al2O3-Fe3O4(ZACF)磁性纳米复合氧化物固体酸催化剂,通过电感耦合等离子体原子发射光谱、比表面积测定、X射线衍射、透射电镜、热重分析和红外光谱等对其进行了表征,并利用酯化反应作为探针反应评价了其催化性能.结果表明,合成的磁性纳米固体酸催化剂在酯化反应中表现出很好的催化活性.