溶胶-凝胶法制备二元稀土掺杂(Sm2O3)0.04 (Gd2O3)0.06 Ce0.8O2-δ纳米粉体

以Sm2O3、Gd2O3与Ce2(CO3)3.nH2O为原料,采用Sol-Gel法制备了二元稀土掺杂(Sm2O3)0.04(Gd2O3)0.06Ce0.8O2.δ纳米粉体.测定了pH值对0.80Ce(OH)4·0.08Sm(OH)3·0.12Gd(OH)3水溶胶体系zeta电位的影响.pH值约为7.0时,体系的Zeta电位为0,即体系的等电点(IEP)为7.0.pH值为10.0时,Zeta电位达到最大值-18.5my,说明此时该体系的稳定性最好.DTA/TG热分析表明,0.80Ce(OH)4·0.08Sm(OH)3·0.12Gd(OH)3粉体的热分解温度约为232℃.由粉末XRD分析可知,经750℃焙烧的二元稀土掺杂CeO2粉末为立方萤石结构,说明Sm2O3与Gd2O3已完全固溶到CeO2中形成了CeO2基固溶体.由TEM照片可以看出,粉末具有良好的分散性,呈软团聚状态,粒径在5-10nm之间.经BET测试计算的平均颗粒尺寸为11nm,与TEM结果是一致的.     

共沉淀-喷雾干燥法制备Sm2O3掺杂CeO2纳米粉体

以Sm（NO3）3.6H2O和Ce（NO3）3.6H2O为原料,用共沉淀-喷雾干燥法制备了Sm2O3掺杂CeO2（SDC）粉体。通过沉降实验、TG-DSC、XRD、BET、SEM和粒度分布对前驱体的分散性、稳定性及制得的SDC粉体性能进行表征,研究了洗涤方法、分散剂对前驱体及SDC粉体的影响。结果表明：无机陶瓷膜洗涤后前驱体分散性好,经500℃以上温度焙烧后的粉体为立方萤石型结构。加入分散剂后前驱体的分散性明显提高,制得的SDC粉体比表面积显著增加,最终获得了晶粒平均粒径为12.51 nm、团聚态颗粒为球形的SDC纳米粉体。     

铈掺杂TiO2光催化剂的制备及其催化性能

以TiCl4为原料、Ce(NO3)3·6H2O为稀土掺杂剂,制备了不同掺杂量的Ce/TiO2粉体,并进行了DTA-TG,XRD,SEM和TEM表征.实验主要考察铈掺杂对TiO2粉体的表面形状和光催化活性的影响.结果表明,掺铈能明显改善样品的团聚状态,有利于样品比表面积的增大.SEM和TEM对500℃的焙烧样品表征结果,掺杂样品二次颗粒的成孔性远好于没有掺杂的纯样品.掺杂量从m(CeO2)=0.5%增加到m(CeO2)=8%,样品的比表面积增加了74m2·g-1;活性评价结果表明,掺杂铈可有效提高催化剂的光催化活性,其中m(CeO2)=1%的样品活性最好.     

铈掺杂TiO2光催化剂的制备及其催化性能

以TiCl4为原料、Ce(NO3)3·6H2O为稀土掺杂剂,制备了不同掺杂量的Ce/TiO2粉体,并进行了DTA-TG,XRD,SEM和TEM表征.实验主要考察铈掺杂对TiO2粉体的表面形状和光催化活性的影响.结果表明,掺铈能明显改善样品的团聚状态,有利于样品比表面积的增大.SEM和TEM对500℃的焙烧样品表征结果,掺杂样品二次颗粒的成孔性远好于没有掺杂的纯样品.掺杂量从m(CeO2)=0.5%增加到m(CeO2)=8%,样品的比表面积增加了74m2·g-1;活性评价结果表明,掺杂铈可有效提高催化剂的光催化活性,其中m(CeO2)=1%的样品活性最好.     

爆轰法制备球形纳米CeO2粉末

采用爆轰合成的方法,以Ce(NO3)3·6H2O为原料,制得了CeO2纳米粒子. 炸药采用黑索金粉,添加剂为CO(NH2)2,NaNO2. 爆轰产物经水洗,烘干后,利用X射线衍射仪器和高分辨率透射电镜对实验结果进行了分析. XRD结果表明,该法所得到的CeO2为立方晶系,颗粒平均粒度为33 nm. TEM图像显示其颗粒呈球形,颗粒大小主要分布在20～40 nm之间,颗粒具有较好的分散性. 球形纳米CeO2颗粒的形成原因有两点:(1) 由于爆轰过程的快速性和急剧冷却的特点,CeO2晶粒来不及择优生长; (2) 产物Na2CO3的熔点较低,爆轰时呈熔融状态包覆在CeO2晶核的周围,阻隔了CeO2晶粒的团聚生长.     

Y2O3和CeO2复合掺杂ZrO2纳米晶的制备与表征

以ZrOCl2.8H2O,Y2O3,Ce（NO3）3.5.5H2O为原料,NH3.H2O作沉淀剂,少量表面活性剂PE作分散剂,采用反向共沉淀-喷雾干燥法,结合物理、化学分散技术,成功地制备了Y2O3,CeO2复合掺杂ZrO2纳米粉末。通过DSC-TG,XRD,XPS,BET和SEM等方法对所制得粉末进行了表征。结果表明：以Ce0.1Y0.1Zr0.8O1.95化学计量比制备的多元氢氧化物胶体经过喷雾干燥处理后,在500℃基本完成水合氧化物的分解,577℃附近完成由非晶相向立方相的转变;经过580-1000℃煅烧后,CeO2和Y2O3已经完全固溶到ZrO2中,形成类质同相体,该粉末系列均属于立方相萤石结构;掺杂进入ZrO2晶格中的Ce呈＋4价形式存在;比表面积由22.0 m^2.g^-1（580℃煅烧）减至4.97 m^2.g^-1（1000℃煅烧）;SEM结果显示800℃煅烧的该粉末颗粒尺寸分布均匀,多呈类球状,且粒径在50-80 nm。     

共沉淀法制备Lu3 Al5 O12:Ce陶瓷发光粉体的研究

报道了用反滴定共沉淀法及低温煅烧前驱体的方法制备Ce3+摻杂的Lu3Al5O12石榴石陶瓷发光粉体的研究. 通过对实验中制备的Lu3Al5O12∶ Ce前驱体和煅烧粉体进行的X射线粉末衍射(XRD)和透射电镜(TEM)的测试表征表明, 在1000 ℃烧结热处理2 h即可获得完全单一的立方相Lu3Al5O12∶ Ce粉体, 粉体的平均粒径～30 nm. 而随烧结温度的增加, 粒径有增大的趋势. 在1000 ℃空气氛热处理的Lu3Al5O12∶ 0.5%Ce发光粉体具有最强的荧光发射. 粉体经干压、等静压成型后, 在1800 ℃经流动的H2气氛常压烧结保温6 h可获得半透明Lu3Al5O12∶ 0.5%Ce陶瓷. X射线激发下的快分量衰减时间短至十几ns, 占发光成分中主要部分的慢分量为～100 ns.     

附载CeO2的纳米γ-Al2O3合成及其悬浮液的分散稳定研究

以异丙醇铝和六水硝酸亚铈为铈源和铝源,采用溶胶-凝胶法制备了前驱体,并将前驱体在800℃下空气中焙烧2 h得到附载CeO2的高纯纳米γ-Al2O3.样品经X射线衍射(XRD)、透射电镜(TEM)、比表面积(BET)、化学成分和杂质含量分析,结果表明:合成的粉末为由γ-Al2O3和CeO2组成的混合物相,两者均属立方晶系,其中γ-Al2O3空间群为O7H-FD3M,CeO2空间群为Fm3m;晶粒平均粒径为15.7 nm,颗粒平均粒径约60～80 nm,粒子呈类球形,比表面积为159.01 m2·g-1;粒子纯度不低于99.97%,CeO2含量为24.22%.红外光谱(IR)测试结果显示,有Al-O-Ce键生成,表明CeO2与Al2O3并非简单混合.进一步通过对其悬浮液体系Zeta电位和吸光度的测定,研究了不同pH值条件、分散剂种类和用量以及氧化剂对其悬浮液分散稳定性的影响;采用超声波分散法,选择硝酸、氢氧化钾溶液作为pH调节剂,异丙醇胺作为分散剂,过氧化氢作为氧化剂,成功制备了长期存放不沉降的附载CeO2的纳米γ-Al2O3CMP浆料,确定了配制的优化工艺条件.     

粒径可控纳米CeO_2的微乳液法合成

以十六烷基三甲基溴化铵(CTAB)/正丁醇/正辛烷/硝酸铈(Ce(NO3)3)水溶液(氨水)所形成的反相微乳液体系合成CeO2前驱体,利用热重(TG)和X射线衍射(XRD)分析方法确定了得到纳米CeO2的适宜焙烧温度为550℃,CeO2前驱体经550℃焙烧后得到纳米CeO2.采用XRD、透射电镜(TEM)、紫外-可见(UV-Vis)分光光度计等表征手段分别对纳米CeO2的晶形、形貌、粒径及紫外吸收性质进行了表征,该纳米CeO2粒子具有立方晶型结构,分散性较好、粒径范围为5-18nm.考察了微乳液中正辛烷与正丁醇质量比、Ce(NO3)3浓度对纳米CeO2粒径的影响,结果表明:利用微乳液法,通过改变微乳液中正辛烷与正丁醇质量比、Ce(NO3)3浓度能够对纳米CeO2粒径进行有效控制;纳米CeO2的粒径均随着正辛烷与正丁醇质量比和Ce(NO3)3浓度的增大而减小.同时,对不同条件下制得的纳米CeO2的紫外吸收性质进行了考察.     

铈掺杂对超细LaMnO_(3+λ)催化性能的影响

以Ce2(CO3)3,La2O3和Mn(NO3)2为原料,用"溶胶-凝胶"法结合"超临界干燥"技术,将铈掺入超细LaMnO3+λ气凝胶中。用TG-DTA,XRD,TEM,FT-IR等手段对样品进行表征;并用"2CO+2NO=2CO2+N2"反应测试铈掺杂对超细LaMnO3+λ催化活性的影响。结果显示:260℃时,镧铈锰气凝胶为疏松、絮状且具有较好分散性的棕色粉末,由大量直径小于10 nm的球形颗粒组成;850℃热处理后,镧铈锰气凝胶为粒径小于20 nm的类球形颗粒,晶相成分为LaMnO3+λ,La2O3和CeO2;铈掺杂增加LaMnO3+λ晶格的氧空缺数量,改善氧化还原催化的气氛条件,提高超细LaMnO3+λ的催化活性。     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Die Photoionenspektren von SCl2, S2Cl2 und S2Br2

Photoionization Mass Spectra of SCl₂, S₂Cl₂, and S₂Br₂ Photoionization mass spectra of SCl₂, S₂Cl₂, and S₂Br₂ have been measured. Heats of formation, bond energies, and ionization potentials of fragments have been calculated from appearance potentials.