多孔氮化硅陶瓷的微观结构、力学性能和气体透气性的研究

本研究中,以石油焦为造孔剂、Y2O3-Al2O3为烧结助剂,通过注浆成型制备出多孔氮化硅陶瓷.研究石油焦的加入量对多孔氮化硅陶瓷微观结构、力学性能及气体透气性的影响.结果表明:多孔氮化硅陶瓷的微孔是由长棒状的β-Si3N4晶粒互相搭接而成,大孔是由石油焦燃烧而成.随着石油焦加入量的增加,气孔率及达西渗透系数(μ)增大,但试样的抗弯强度降低.在起始α-Si3N4粉末中添加10wt;～50wt;石油焦、5wt; Y2O3-3wt;Al2O3 1800℃下保温2h制备出气孔率为37.08;～59.40;、抗弯强度为52.00～154.27 MPa、μ值为(3.04 ～6.87)×10-13m2的多孔氮化硅陶瓷.     

pH值对ZrO2超细粉体料浆性能的影响

研究了不同pH值时超细ZrO2粉体料浆的Zeta电位、沉降速度和粘度等性能.测试了加入柠檬酸三铵作分散剂和A型分散剂(聚丙烯酸盐)以及不加分散剂时料浆的Zeta电位,结果证明采用A型分散剂分散效果最好,在pH=10.53时Zeta电位具有最大负值-44.28mV,研究了不同pH值时料浆的沉降情况,在pH=10.55时料浆沉降速度最慢,同时研究了pH值对料浆粘度的影响,在pH=10.66时料浆粘度最低.料浆呈现出剪切变稀特性,在pH值为10～11范围内,成型的坯体网络结构稳定,最大弯曲强度达到53.90MPa.     

高固相含量纳米ITO水基浆料流变性能的研究

以PAA为分散剂制备高固相含量纳米ITO水基浆料,研究了pH值、分散剂用量、固相含量对浆料流变性能的影响.结果表明:PAA对改善纳米ITO粉体的表面电动特性有显著作用,PAA的加入使粉体Zeta电位从-16mV降到-38 mV;高固相含量的浆料均呈现出明显的剪切变稀行为;浆料粘度随固相含量增加而急剧增大;最佳的PAA用量及pH值范围分别为0.06 mg/m2和10～11.55wt;固相含量的浆料在150 s-1剪切速率下粘度为0.38 Pa·s,以此为原料采用胶态成型技术制备出微观结构均匀的ITO陶瓷素坯.     

La2O3对氧化铝/高岭土复合定向多孔陶瓷性能的影响

以微米级α-Al2O3、陶瓷水体分散剂为主要原料,以La2O3-水洗高岭土为烧结助剂,采用冰模板法制备了一种具有高孔隙率和较高抗压强度的氧化铝/高岭土复合定向多孔陶瓷.研究了不同添加量的La2O3对多孔陶瓷的显气孔率、体积密度、抗压强度和微观形貌的影响.结果表明:添加适量的稀土La2O3能降低多孔陶瓷烧结温度、提高体积密度和抗压强度.通过高能机械球磨法添加La2O3,在1350℃烧结制备的多孔材料样品显气孔率为82;,样品的抗压强度达到10 MPa以上.当La2O3加入量达到3;时,可使多孔陶瓷抗压强度提高到15.2 MPa,较不掺加La2O3提高了约53;.     

分散剂对CSLST微波介质陶瓷水系流延浆料稳定性的影响

分别采用聚乙烯吡咯烷酮(PVP)、聚乙烯酸(PAA)、聚丙烯酰胺为分散剂,以苯丙乳液为粘结剂,丙三醇为增塑剂,去离子水为分散介质,水系流延成型法制备添加B2O3-CuO-LiCO3(BCL)玻璃料为烧结助剂的(Ca0.9375Sr0.0625)03(Li0.5Sm0.5)07TiO3 (CSLST)微波介质陶瓷,研究了分散剂种类及含量对陶瓷粉体浆料分散稳定性以及流延膜片的影响.结果表明:当以PVP为分散剂,添加量为0.8;,调节浆料的pH=10时,浆料的分散稳定性最佳,经流延后可制备得到表面光滑,均匀无裂纹的延膜片.     

多孔陶瓷负载TiO2光催化降解甲基橙溶液的研究

采用有机先驱体浸渍法及无压烧结工艺,制备了Al2O3多孔陶瓷载体。利用溶胶-凝胶法在多孔陶瓷上负载Sm3+掺杂Ti O2光催化材料。研究了煅烧温度、涂层次数等工艺因素对多孔陶瓷负载Ti O2光催化降解甲基橙溶液的影响规律。结果表明,借助于多孔陶瓷高的气孔率,Ti O2负载在Al2O3颗粒表面或进入颗粒间的孔隙内,使材料具有较大的比表面积。掺入Sm3+使材料的光催化活性提高。在煅烧温度为600℃、四次涂层、甲基橙溶液p H值为2时,多孔陶瓷负载Ti O2光催化降解甲基橙溶液效果最佳。     

共沉淀法制备CoAl2 O4陶瓷颜料及其呈色机理研究

采用共沉淀法制备CoAl2 O4陶瓷颜料,并通过XRD、SEM和XPS表征陶瓷颜料的组成、形貌和元素价态,研究Co/Al比、溶液pH值和煅烧温度对CoAl2 O4陶瓷颜料呈色的影响,并探讨其呈色机理。结果表明：所得CoAl2 O4陶瓷颜料均具有典型的尖晶石结构,当Co/Al比为0.7∶2、溶液pH值为11、煅烧温度为1200℃时可以获得彩度较高的蓝色CoAl2 O4陶瓷颜料。 CoAl2 O4陶瓷颜料的呈色变化主要与所得产物中Co元素的价态有关,当Co含量过高或者前驱体溶液的pH值较大时,产物中含有Co3 O4( Co4+),进入CoAl2 O4后形成固溶体导致其晶格发生畸变,从而使得陶瓷颜料呈现绿色。     

聚乙二醇对自反应淬熄法制备空心陶瓷微珠的影响

以Al+ Fe2O3+ BaO2+蔗糖+环氧树脂为反应体系、聚乙二醇为表面活性剂,运用将火焰喷涂技术与自蔓延高温合成技术(Self-propagating High-temperature Synthesis,缩写SHS)及快速冷却凝固技术相结合的自反应淬熄法,制备了空心复相陶瓷微珠.通过SEM、EDS、XRD等手段,研究了聚乙二醇的加入对团聚粉及制备的空心陶瓷微珠的影响.结果表明,与未加聚乙二醇相比,加入聚乙二醇后,团聚粉颗粒分布均匀,具有良好的流动性;所制备的空心微珠粒径趋于一致,成球率得到了明显提升,相结构中Fe3O4转变成了Fe2O3,且出现了具有尖晶石结构的BaFe2O4,这有助于提高空心微珠的吸波性能.     

淀粉固结工艺制备多孔氮化硅基陶瓷复合材料

本文以氮化硅,氮化硼,二氧化硅作为陶瓷基体材料,通过淀粉固结工艺,采用常压部分氧化烧结制备了氮化硅基多孔陶瓷。通过Zeta电位测试确定了制备陶瓷坯体的最佳pH值在9.42~10.76之间。混合浆料的浆料流变性能测试表明陶瓷浆料体系呈现剪切变稀特征。XRD分析结果表明在烧结样品组成成分为α-Si3N4、β-Si3N4、BN、Quartz low,sys以及Moganite。SEM的显示氮化硅基多孔陶瓷呈现片层型微观结构。显气孔率随淀粉含量增加而增加,试验制得多孔陶瓷显气孔率最大值高达73.2%。     

高性能氮化硅陶瓷凝胶注模成型的研究

凝胶注模成型工艺的关键在于制备低粘度高固相体积含量的陶瓷浆料.本文以四甲基氢氧化铵(TMAH)溶液为分散剂制备氮化硅陶瓷浆料,研究了pH值、分散剂含量、助烧剂含量以及固相体积含量对氮化硅浆料流变性的影响;测定了凝胶注模成型素坯以及烧结体的力学性能.研究结果表明:当pH＝10.5,分散剂加入量为6;(相对于氮化硅固相体积比),助烧剂加入量为10;(质量分数)时,浆料具有最好的流变性.根据以上制备的工艺参数,制备得到固相体积含量大于50;,具有良好流变性的浆料.铸模成型干燥后,素坯的抗弯强度达27MPa;常压烧结后氮化硅陶瓷具有优异的力学性能,其抗弯强度为730 MPa,断裂韧性高达8.8 MPa·m1/2.     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

Selinidin: Crystal structure generated by C–H···O, C–H···π and π-π interactions

The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C₁₉H₂₀O₅, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 ₁ with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.     

Chromene and Imidazole Based D-π-A Chemosensor Preparation and Its Anion Responsive Effects

We have designed and synthesized the colorimetric chemosensor through the reactions of 2-(4H-chromen-4-yildene)malonitrile and 4-imidazolecarboxaldehyde. Due to its well conjugated D-π-A system and the existence of NH- fragment in structure, we expected that the chemosensor can detect anion using NH- fragment in the imidazole moiety of the structure. In this regard, UV-Vis absorption spectra were measured to investigate sensing properties of the probe toward different anions in DMSO. This chemosensor can detect both fluoride and cyanide ion with absorption change in intensity. In addition, pH sensing property was also investigated upon the addition of hydroxide ion. These properties are related to the deprotonation effect. The ICT system in this molecule was also observed by the computational approach using Material Studio 4.3 package.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

4- and 5-nitroindane

Mononitration of indane produces a mixture of 4- and 5- nitroindanes. Crystallization from mixtures occurs after distillation improves composition of a major component to above 80%. 4-Nitroindane: triclinic, space group (#2),a=7.332(4) Å,b=8.304(4) Å,c=8.358(4) Å, =61.43(4)°, =67.60(4)°, =70.15(4)°,V=405.4(4) ų,Z=2. Non-H-atoms are nearly planar, aliphatic H's are eclipsed. 5-Nitroindane: monoclinic, space groupP2₁/c (#14),a=10.946(8) Å,b=15.643(10) Å,c=9.415(6) Å, =92.34(5)°,V=1611(2) ų,Z=8. Non-H-atoms in the two molecules differ in torsion of the nitro group with respect to indane and fold of the nonbenzylic methylene group. Semiempirical calculations (PM3) suggest that distorsion from planarity may be associated with the two lowest energy vibrational modes. Uv, ir, ms, proton, and¹³C-nmr spectra are correlated with the solid state structures.     

6<Emphasis Type="Italic">S</Emphasis>,8α-Dihydroxy-14,15-Dihydrocarapin (Khayanone) from the Stem Bark of <Emphasis Type="Italic">Khaya Senegalensis</Emphasis> (Meliaceae): Isolation and its Crystal Structure

Khayanone was isolated from the stem bark of African mahogany, Khaya senegalensis (Meliaceae), and characterized as 6S,8α-dihydroxy-14,15-dihydrocarapin on the basis of spectral analysis and single crystal X-ray diffraction study. The compound crystallizes in the tetragonal space group P4 ₁ 2 ₁ 2 with unit cell parameters: a = 13.2315(19) Å, c = 29.118(6) Å, Z = 8. The crystal structure has been solved by direct methods and refined to R = 0.0375 for 4552 unique reflections. The six-membered rings A and B exist in boat conformations, rings C and D in chair conformations, and the furan ring is planar. The crystal structure is stabilized by O-H···O and C-H···O interactions. This is the first report about 6S configuration of mexicanolide revealed by X-ray diffraction analysis. The configuration of oxygenated C-6 in mexicanolide-group limonoids is discussed.     

Nuclear magnetic resonance: a powerful tool to study liquid crystals

Nuclear magnetic resonance (NMR) is a spectroscopic technique widely used to investigate materials and soft matter in particular. In this brief review, the main uses of NMR techniques to investigate different aspects of liquid crystals, such as the orientational and dynamic properties, the supramolecular structure and average molecular conformations, are described. In the second part of the paper, the case study of a ‘de Vries’ liquid crystal is reported and the main results obtained by combining different NMR techniques are discussed.     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)