Ce:Y_3Al_5O_(12)透明陶瓷的制备和荧光性能的研究

以Ce(NO3)3.5H2O,Y(NO3)3.5H2O和A l(NO3)3.9H2O为原料,NH4HCO3为沉淀剂,采用醇水溶剂共沉淀法在弱还原气氛下1100℃煅烧2 h合成纯相1 at%Ce∶YAG纳米粉体,经1800℃真空烧结10 h后得到了Ce∶YAG透明陶瓷。通过XRD、TEM、SEM和荧光光谱仪对粉体和陶瓷进行了表征。结果表明:所制得的Ce∶YAG纳米粉体散均匀、团聚程度轻、结晶良好,平均晶粒尺寸约35 nm。Ce∶YAG透明陶瓷和纳米粉体的发射峰都在530 nm附近,但透明陶瓷的发射强度明显比纳米粉体强,且发射峰向长波方向移动。     

等静压成型对氮氧化铝陶瓷透明性的影响

本文采用高纯Al2O3、AlN和Al粉为原料,用Y2O3和MgO作为烧结助剂,在150 MPa下等静压成型,然后在氮气氛下,1850℃保温1 h制备出透明尖晶石型氮氧化铝(AlON)陶瓷.结果表明,透明AlON陶瓷晶粒尺寸细小,晶粒发育完善且分布均匀,晶界平直光滑且无第二相的存在.用等静压成型能明显能明显提高紫外区和可见光区的透明性能,但对红外区影响不明显,其在紫外光区(200～1100 nm)最大透光率为82;,在红外光区(1750～5000nm)最大透光率为98;,密度为3.70 g/cm3,约为其理论密度的99.7;.     

改进的共沉淀法制备YAG纳米粉体及透明陶瓷

采用改进的共沉淀法制备YAG透明陶瓷,研究了沉淀剂与金属盐溶液的摩尔比对粉体合成的影响以及成型压力对陶瓷烧结的影响.利用X射线衍射仪和场发射电子显微镜对实验样品进行表征.结果表明:当沉淀剂与金属盐溶液的摩尔比为NH4 HCO3/([Al3+]+[Y3+])=8,使用改进的共沉淀法在1000℃煅烧2h制备出平均粒径约为65 nm的YAG纳米粉体.以此YAG粉体为原料,TEOS为烧结助剂,经100 MPa成型后,在1750℃下真空烧结15 h获得透明陶瓷.     

碳酸盐共沉淀法制备Er:YAG透明激光陶瓷粉体

本文用碳酸盐共沉淀法制备出性能良好的透明Er:YAG陶瓷粉体,并应用DTA-TG、XRD、SEM、红外光谱等测试手段分析其粉体结构和形貌.结果表明在1000℃煅烧过程中,失重约45;,所得到的Er:YAG粉末结晶性能良好,粒度在150～200nm之间.而且经烧结后的陶瓷断面气孔率低,多晶晶粒尺寸在1～2μn之间.1700℃烧结后得到透光度良好的陶瓷体.     

共沉淀法制备YAG纳米粉体影响因素的研究

本文采用Al(NO3)3.9H2O和Y(NO3)3·6H2O为母盐,碳酸氢铵为沉淀剂,利用共沉淀法制备YAG(Y3Al5O12)纳米粉体。利用XRD、SEM对YAG前驱体及煅烧纳米粉体进行了表征,并分析了母盐溶液的浓度、母盐溶液的滴加速度以及有机溶剂的种类对制备YAG纳米粉体的影响。结果表明:母盐溶液的浓度、滴加速度及有机溶剂种类对前驱体和煅烧粉体的分散性、组成及形貌有显著的影响。当母盐溶液浓度比较低时([Y3+]=0.08mol/L,[Al3+]=0.13mol/L),得到YAG纳米粉体的分散性较好,加入少量乙醇(乙醇与母盐溶液体积比为1∶5)更易获得纯相YAG粉体,快速加入母盐溶液比慢速滴入更易获得纯相YAG粉体。实验证实所制备的YAG粉体能够烧结出透明陶瓷,证明通过系统地控制上述3个因素可以得到具有良好烧结性的YAG纳米粉体。     

碳酸盐共沉淀法制备Er∶YAG透明激光陶瓷粉体

本文用碳酸盐共沉淀法制备出性能良好的透明Er∶YAG陶瓷粉体 ,并应用DTA TG、XRD、SEM、红外光谱等测试手段分析其粉体结构和形貌。结果表明在 10 0 0℃煅烧过程中 ,失重约 4 5 % ,所得到的Er∶YAG粉末结晶性能良好 ,粒度在 15 0～ 2 0 0nm之间。而且经烧结后的陶瓷断面气孔率低 ,多晶晶粒尺寸在 1～ 2 μm之间。 170 0℃烧结后得到透光度良好的陶瓷体     

WO3掺杂对BST微波介质陶瓷性能的影响

采用固相反应法,研究了WO3掺杂对Ba4Sm9.33Ti18O54(简称BST)微波介质陶瓷相组成、显微结构、烧结性能与介电性能的影响.结果表明:适量添加WO3能通过不等价离子取代Ti位,产生晶格缺陷,促进离子扩散,不仅能有效降低BST陶瓷的烧结温度至1280 ℃,而且能减少氧空位的产生,降低介电损耗.同时适量WO3时有新相BaWO4生成,它的出现也有利于改善其介电性能.添加0.25wt; WO3的BST陶瓷在1280 ℃烧结3 h时取得最佳介电性能:εr=80.4,Q·f=11740.85 GHz,Υf=-23.3×10-6/℃.     

Li2CO3掺杂对0.94Mg2SiO4-0.06Ca0.9Sr0.1TiO3陶瓷微波介电性能的影响

采用传统固相反应法,研究了Li2CO3掺杂对0.94Mg2SiO4-0.06Ca0.9Sr01TiO3微波介质陶瓷的烧结性能和介电性能的影响.结果表明,烧结助剂Li2 CO3的引入未改变陶瓷的相组成.添加适量的Li2CO3可以促进烧结,烧结温度由1440℃降低到1355℃,而且介电性能也得到了优化,Q ×f值有明显的提高;过量Li2CO3的引入,降低了材料的致密性,增加了陶瓷的介电损耗.在1355℃烧结,保温3h,添加0.50wt; Li2 CO3的0.94Mg2SiO4-0.06Ca09Sr0.1TiO3陶瓷获得最佳的介电性能:εr=7.96,Q×f=96409 GHz(f=14.571 GHz),τf=+4.62 ppm/℃.     

V2O5掺杂对0.6SrTiO3-0.4LaAlO3微波介质陶瓷结构与性能的影响

采用固相反应法,研究了V2O5添加量与0.6SrTiO3-0.4LaAlO3(简称6ST-4LA)陶瓷烧结性能及介电性能之间的变化关系.结果表明:少量V2O5的引入未改变陶瓷的晶相组成,主晶相仍为SrTiO3基固溶体,适量添加V2O5不仅能显著降低6ST-4LA陶瓷的烧结温度,而且能增大其介电常数和品质因数(Q·f),调节谐振频率温度系数τf;随着V2O5添加量的继续增加,有第二相SrVO3出现并逐渐增多.当V2O5添加量为0.10wt;,1450 ℃烧结时,6ST-4LA陶瓷获得最佳微波介电性能:εr=46.46,Q·f=59219 GHz,τf=3×10-6 /℃.     

利用水热沉淀法合成的YAG粉体制备多孔陶瓷及性能研究

YAG具有许多独特的性能,应用非常广泛.利用水热沉淀法制备超细YAG粉体,研究合成工艺对粉体形貌的影响,并采用合成的超细YAG粉体制备YAG多孔陶瓷,结果显示:盐碱摩尔比Y3+:OH-=1:8时,能够得到形貌比较均匀的颗粒,当继续增大盐碱摩尔比时,得到的粉体形貌没明显变化.反应时间越长,颗粒尺寸越粗大.Y3+的浓度越小,颗粒尺寸越细小.通过实验,在反应温度为200 ℃、反应时间为2 d和盐碱摩尔比为1:8的条件下,所得到棒状颗粒为多晶体结构,它的直径大约是150 nm,长度大约为4000 nm,通过XRD检测,粉体纯度较高.随着陶瓷坯体烧结温度的提升,YAG多孔陶瓷气孔率呈现下降趋势,而抗压强度随之升高.结合气孔率、抗压强度和显微孔结构综合考虑,利用水热沉淀法合成的棒状超细YAG粉体烧结制备YAG多孔陶瓷的烧结温度确定为1500 ℃较为适宜.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

Crystal structures of the cis and trans isomers of a tetrathia[3.3.3.3]cyclophane

Both the cis and trans isomers of 3,11,18,26-tetrathiatricyclo[26.2.2.1^5,9.2^13,16.1^20,24] hexatriaconta-5,7,9,20,22,24-hexene have been prepared and structurally characterized. Each of these centrosymmetric tetrathia dimers includes two cyclohexane rings in chair conformations with either 1,4-cis or 1,4-trans bonding and two meta-substituted benzene rings. The cis isomer packs into the monoclinic space group P2₁/a with a = 10.485(3)Å, b = 10.3956(18)Å, c = 14.1343(10)Å, = 105.200(13)°, Z = 2 and refined to an R factor of 0.046. The trans isomer crystallizes in the monoclinic space group P2₁/c with a = 10.7217(12)Å, b = 5.6797(7)Å, c = 25.415(5)Å, = 96.001(12)°, Z = 2 and refined to an R factor of 0.043. In the cis structure each benzene ring faces a cyclohexane ring while in the trans structure the cyclohexane rings face one another.     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.     

电沉积法制备ZnO纳米棒阵列及其发光特性

本文以掺F的SnO2导电玻璃为基板,以硝酸锌水溶液为电解液,采用三电极恒电位体系电沉积制备ZnO纳米棒阵列,系统考察了硝酸锌浓度和沉积电位等工艺参数对ZnO纳米棒阵列的微观形貌及其发光性能的影响规律.结果表明,硝酸锌浓度和沉积电位对纳米棒阵列的形貌有显著影响,控制适宜的工艺条件可以制备出直径分布均匀、结晶性好且纯度高的六方纤锌矿ZnO纳米棒阵列.荧光光谱分析表明,电沉积制备出的ZnO纳米棒阵列在385 nm附近有一个强荧光发射峰,且发光性能稳定、对纳米棒阵列微观形貌的细微变化不敏感,使其在发光二极管和激光器等领域具有广阔的应用前景.