凝胶注模成型Al2O3·ZrO2泡沫陶瓷的制备与表征

采用环保无毒生物高分子明胶作胶凝剂和四甲基氢氧化铵（TMAH）为分散剂，通过凝胶注模工艺制备了相对密度为10％～35％的ZrO2增韧Al2O3（ZTA）泡沫陶瓷，对制备泡沫陶瓷的结构和性能进行了表征。SEM分析表明泡沫陶瓷由相互贯通的球形孔室构成，其孔径分布取决于泡沫陶瓷的相对密度。ZTA泡沫陶瓷抗弯强度随相对密度从10％变化到31％而相应地从3．1MPa提高至28．1MPa，渗透系数随相对密度的增大呈指数衰减。     

ZrO2添加量对ZTA陶瓷力学性能及冲蚀磨损行为的影响

以α-Al2O3、ZrO(NO3)2.2H2O和氨水为原料,通过高温煅烧制备了ZTA复相陶瓷材料,研究了ZrO2添加量对ZTA陶瓷物相组成、表面微观形貌、力学性能以及常温固体粒子冲蚀磨损性能的影响。结果表明:随着ZrO2添加量增加,材料的力学性能逐渐提高,当ZrO2添加量为10 vol%时,ZTA复相陶瓷抗弯强度和断裂韧性分别达461MPa和5.77 MPa.m1/2,相对于纯Al2O3陶瓷提升量达21.3%和64.9%。ZTA复相陶瓷材料的体积冲蚀率随着ZrO2添加量的增加而降低,当ZrO2添加量小于4 vol%时,其体积磨损率急剧下降,随后趋于平稳;随后当ZrO2添加量为10 vol%时,其冲蚀率达最低,为0.015 mm3/g。其中,纯Al2O3陶瓷材料的冲蚀磨损机制主要为横向裂纹相互交错导致材料的剥落,添加ZrO2后,其冲蚀磨损机制以塑性变形为主。     

SiC泡沫陶瓷的凝胶注模制备与表征

以高分子多糖明胶为胶凝剂,采用凝胶注模工艺制备SiC泡沫陶瓷.测量了分散剂加入前后浆料的ζ电位的变化.研究了分散剂四甲基氢氧化铵(TMAH)、明胶加入量、固含量等对SiC浆料流变性能的影响.结果表明:分散剂的加入对SiC颗粒的动力学行为有显著影响.在碱性范围内,ζ电位绝对值随TMAH加入量的增加而增大;明胶的加入明显提高了浆料的粘度;固含量为65;~74;时,为使浆料具有好的稳定性和流动性,同时保证明胶的成胶性能,TMAH和明胶的加入量应分别控制在2.5;左右及5;~7;为宜.制备的泡沫陶瓷由相互贯通的球形孔室构成,孔隙率最高可达到92;,其孔径分布取决于泡沫体孔隙率,对于孔隙率为76;和90;的样品,其孔径分别达到120 μm 和200 μm.泡沫陶瓷的抗弯强度随相对密度增大而提高,相对密度达到25;时,其抗弯强度可达到25.2 MPa.     

磷酸盐低温烧结高强度SiC泡沫陶瓷及性能研究

通过有机模板复制法,以磷酸二氢铝为粘结剂,950 ℃烧成制备了高强度SiC泡沫陶瓷.研究了浆料中SiC含量和磷酸二氢铝含量对SiC泡沫陶瓷微观结构与性能的影响.结果表明:SiC微粉由A型Al(PO3)3粘结起来,烧成泡沫陶瓷通孔结构良好,开气孔率介于75;~91;之间.随着磷酸二氢铝含量的增加,烧成泡沫陶瓷的线收缩率、体积密度和抗折强度均逐渐增加,而开气孔率则逐渐减小;随着SiC含量的增加,烧成泡沫陶瓷的线收缩率和开气孔率均逐渐减小,而体积密度和抗折强度则逐渐增加.磷酸二氢铝含量为40;、SiC含量为60;时,泡沫陶瓷的抗折强度达(2.22±0.26) MPa.     

不同粒度SiC颗粒低温制备SiC泡沫陶瓷的性能

以SiC陶瓷前驱体聚碳硅烷(polycarbosilane,PCS)为粘结剂、SiC微粉为填料、聚氨酯海绵为模板,低温制备出了SiC泡沫陶瓷.研究了SiC颗粒粒度和PCS含量对SiC泡沫陶瓷线收缩率、体积密度、微观结构与抗弯强度的影响.确定了不同粒度SiC颗粒制备泡沫陶瓷的最佳烧成温度.结果表明,随SiC颗粒粒度与PCS含量的增加泡沫陶瓷的线收缩率增大、体积密度降低;泡沫陶瓷的抗弯强度随SiC颗粒粒度的增大而降低;颗粒粒度小于1μm时,最佳烧成温度为1200℃,颗粒粒度大于1μm时,最佳烧成温度为1100℃;PCS在1100℃与1200℃热解可得到β-SiC晶粒,其晶粒尺寸为12.2 nm与19.6 nm.     

Yb2 O3含量对ZTA陶瓷相组成、微观结构及力学性能的影响

采用阿基米德排水法、三点弯曲法、单边切口梁法、扫描电子显微镜( SEM)及X射线衍射( XRD)分析手段和设备,研究了不同含量的Yb2 O3对ZTA的相组成、微观结构及力学性能影响,并对烧结后陶瓷样品的密度、力学性能、微观组织结构及相组成进行了研究。研究结果表明：在不添加Yb2 O3时,ZTA的断裂韧性、抗弯强度及硬度均为最大值,分别为7.42 MPa·m1/2、623.10 MPa、1919.60 HV。添加Yb2 O3后,ZTA陶瓷的力学性能及相组成均发生变化,t-ZrO2相变成c-ZrO2相,并且出现新的 Yb3 Al5 O12相。力学性能均有所降低,其中断裂韧性与没有添加Yb2 O3相比,减小了30.7;。     

低温烧结3Y-TZP陶瓷的研究

以不同质量分数的MnO2-TiO2(质量比为1:1)为烧结助剂,在1300～1500 ℃下低温烧结制备了3Y-TZP陶瓷.对3Y-TZP陶瓷的相对密度、物相及显微结构、显微硬度、抗弯强度及断裂韧性进行了测试分析,并对烧结助剂的基本性能进行了表征.探究了烧结助剂及烧结温度对3Y-TZP陶瓷性能的影响.实验结果表明:在3Y-TZP陶瓷中加入烧结助剂MnO2-TiO2(质量比为1:1)可以实现低温烧结.试样的相对密度、显微硬度、抗弯强度、断裂韧性随烧结温度的升高先增大后降低.在烧结助剂为0.5wt;,烧结温度为1350 ℃时,试样的相对密度及力学性能都达到最大,在此条件下,试样的相对密度达97.16;,显微硬度为2032.8 HV,抗弯强度为300 MPa,断裂韧性为8.35 MPa· m1/2,且试样的断裂方式为晶粒拔出及晶粒断裂遵循着穿-沿晶断裂的模式,且晶粒极小.     

热压烧结制备AlN/BN复相陶瓷及其性能研究

以氮化铝(AlN)粉和高活性六方氮化硼(h-BN)粉为原料,不添加烧结助剂,采用热压烧结法制备了AlN/BN(20vol;)复相陶瓷.研究了烧结温度(1750～1900℃)对复相陶瓷相对密度、物相组成、显微结构、力学性能、热导率及介电性能的影响.结果表明,在1850℃以上可以制备出相对密度大于98.6;的致密AlN/BN复相陶瓷.试样显微结构均匀,晶粒细小,晶界干净,无明显杂质相,h-BN未形成明显的卡片房式结构.随着烧结温度的提高,试样的相对密度、力学性能、热导率及介电性能(1 MHz)均显著提高.1900℃烧结的试样性能最优,相对密度99.3;,抗弯强度482±42 MPa、断裂韧性4.4±0.4 MPa·m1/2、维氏硬度8.56±0.33GPa、热导率47.2 W·m-1·K-1、介电常数7.64,介电损耗4.62×10-4.     

叔丁醇基凝胶注模成型制备ZTA多孔陶瓷

采用叔丁醇基凝胶注模成型工艺,以丙烯酰胺为单体制备了ZTA多孔陶瓷.优化了固含量、预混液浓度、引发剂用量和固化温度等成型工艺参数.分析了烧结温度和保温时间对多孔陶瓷气孔率及孔径分布的影响.研究发现固含量为10vol;、预混液浓度为15wt;、引发剂用量为20wt;、固化温度为40℃,在1500c℃条件下保温2h烧结得到的ZTA多孔陶瓷气孔率可达59.05;,最可及孔径为0.72 μm,孔径分布在0.40 ～5.00μm的气孔占总气孔的87.22;,压缩强度达到56.09MPa.     

Al2O3/Y2O3复合助剂对碳化硅蜂窝陶瓷烧结性能的影响研究

以碳化硅为主要原料,以羟丙基甲基纤维素(HPMC)为粘结剂,以Al2O3和Y2O3作为复合烧结助剂,采用挤出成型工艺制备出碳化硅多孔蜂窝陶瓷.探究了复合助剂Al2O3/Y2O3的加入量对蜂窝陶瓷物相组成和微观形貌的影响;研究了烧结温度对碳化硅陶瓷物相、微观形貌以及孔隙率、线收缩率、体积密度、抗压强度的影响规律.结果表明:Al2O3/Y2O3复合助剂的加入量增大和烧结温度的提高,陶瓷液相量增多;在钇铝石榴石(YAG)的共晶点1760 ℃附近,更易于析出结晶形成YAG相.烧结温度升高,陶瓷收缩率增大;体积密度和抗压强随烧结温度变化规律接近;体积密度和抗压强度在1750℃达到最大值分别为1.8 g/cm3和14.09 MPa.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

通过SiO2涂层改善BaSi2O2N2∶Eu2荧光粉的热性能

本文研究了SiO2涂层对BaSi2O2N2∶ Eu2蓝绿色荧光粉发光性能和热性能的影响.采用溶胶-凝胶法制备了SiO2包覆的BaSi2O2N2∶Eu2+蓝绿色荧光粉.实验结果表明,最佳镀膜量为6wt;,当镀膜量大于此值时,荧光粉亮度迅速降低.涂覆SiO2后,在150℃下BaSi2O2 N2∶Eu2荧光粉的热猝灭性能提高了2.4;,在500℃热降解后荧光粉的发光性能提高了15;.SiO2涂层显著提高了BaSi2O2N2∶Eu2+荧光粉的热稳定性.SiO2涂层的作用机理是在荧光粉表面和氧化气氛之间形成阻挡层,保护Eu2的发光中心在热加热过程中不被氧化.     

Optical properties of the germanate melilites Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7

Refractive indices and their dispersion in the wavelength range from 365 nm to 2325 nm and transmission ranges of the tetragonal melilite‐type germanates Sr₂MgGe₂O₇, Sr₂ZnGe₂O₇ and Ba₂ZnGe₂O₇ were determined. The uniaxial positive crystals Sr₂MgGe₂O₇ and Ba₂ZnGe₂O₇ both offer the possibility for phase matched second harmonic generation, a detailed analysis of phase matching conditions is given. The refractive indices of Sr₂ZnGe₂O₇ show an isoindex (isotropic) point at 467 nm. The investigation was performed on Czochralski grown large single crystals. The crystal structure of all three germanates were determined by means of X ‐ray diffraction. The results corroborate unmodulated melilite‐type structures at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Crystal structure of bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate, [C6H5CH2CHCH2CH2NH2CH2CH2]2HPO4·5H2O

The salt bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate is orthorhombic with the following unit cell dimensions: a = 11.235(2) Å, b = 27.924(6) Å, c = 9.321(4) Å space group Pca2₁ with Z = 4. The structure was solved by the Patterson method and refined to final R value of 0.049 for 1802 independent reflections. The flack parameter is 0.14 with an e.s.d. of 0.23. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O—H,...,O and N—H,...,O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure of {Pb[S2CN(C2H5)2]2(1,10-phenanthroline)}2

Lead (II) nitrate reacts with 1,10-phenanthroline and sodium diethyldithiocarbamate in water to produce yellow bisdiethyldithiocarbamata 1,10-phenanthroline lead(II). Crystals from water are triclinic, space group $P\bar 1$ (#2),a=10.53(2) Å,b=11.050(12)Å,c=24.74 (3) Å, α=94.71 (9)⁰, β=98.15(11)^o, γ=114.11(9)^o,V=2569(6) ų,Z=2. Each lead atom has approximate pentagonal pyramid coordination geometry through the nitrogens of a phenathroline and sulfurs of two dithiocarbamates. Additionally, complexes form loose dimers in which lead atoms are weakly coordinated to a sulfur in an adjacent complex. IR and proton nmr spectrum of the complex are consistent with the solid state structure.     

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.