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1.
贝壳珍珠层中的文石相对于在自然环境中生长的文石来说具有更优异的力学性能,这种力学性能取决于其独特的晶体排布方式。通过电子背散射衍射(EBSD)技术获得了马氏珠母贝中不同文石的结晶学取向信息,结果表明珍珠层中文石晶体的c轴均垂直于珍珠层层面,而a、b轴在平行珍珠层方向上具有两级取向畴结构:在初级畴结构内,相邻畴绕c轴偏转,导致不同畴之间a轴或b轴的取向差约64°。在次级畴结构内,文石板片围绕c轴偏转,导致不同畴之间a轴或b轴取向差在10°或20°左右。这种畴结构为我们认识珍珠层中文石的生长机理提供了有益线索。 相似文献
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采用K[Ru(Hedta)Cl]·1.5H2O(edta为乙二胺四乙酸根)与含氮杂环配体5-(4-吡啶)四唑(4-ptz)或2,5-吡啶二甲酸(2,5-Pydc)反应,设计合成了2个单核[Ru(Hedta)(4-ptz)]·4H2O(1)和[Ru(Hedta)(2,5-Pydc)]·3H2O(2)配合物。晶体结构解析表明配合物1属于单斜晶系C2/c空间群,晶胞参数为a=2.348 06(15) nm,b=1.301 23(8) nm,c=14.930 8(9) nm,β=101.075 0(10)°;配合物2属于单斜晶系I2/a空间群,晶胞参数为a=3.249 4(7) nm,b=0.966 23(19) nm,c=1.434 1(3) nm,β=93.88(3)°。对2个配合物分别进行了IR及UV-Vis的表征,并通过电子吸收光谱和荧光淬灭光谱研究了配合物与DNA的作用,实验结果表明这2个钌配合物通过插入方式与DNA作用。 相似文献
5.
本文以6,6'-二硫二烟酸为主配体,通过水热法合成了新的配合物{[Zn(cpds)(dpa)]·H2O}n(1)(H2cpds=6,6'-dithiodinicotinic acid,dpa=dipyridin-2-ylamine)。用X-射线单晶衍射分析确定了配合物为三斜晶系,P1空间群,其晶体学参数为a=0.8467(2),b=1.1674(3),c=1.2265(3)nm,α=73.605(3)°,β=78.656(3)°,γ=81.484(3)°,V=1.1347(5)nm3,Dc=1.850g·cm-3,Z=2。结构分析表明配合物1为一维链状结构,相邻一维链之间堆积形成三维超分子网络结构。本文还研究了配合物的热稳定性和荧光性质。 相似文献
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采用水热法合成了2个具有二维结构的吡啶羧酸类稀土配位聚合物{[Ln2(bpdc)3(H2O)2]·5H2O}n,(Ln=Nd(1),Eu(2),2,2’-Bipyridyl-3,3’-dicarboxylicacid)。单晶衍射分析显示1、2结构相似,均属于单斜晶系,P2/c空间群。1、2的晶胞参数分别为a=1.24100(19)nm,b=0.74835(59)nm,c=2.06050(20)nm,β=94.84(1)°;a=1.24100(19)nm,b=0.74301(20)nm,c=2.05250(30)nm,β=94.95(2)°。配合物是由之字形一维链构成的二维网络结构,其拓扑符号为{3^9;4^18;5}。热重测试结果表明1、2热稳定性较好。配合物2显示出很好的荧光性能。 相似文献
8.
二硝酸根(N, N, N'', N''-四正丁基丙二酰胺)合铀酰(Ⅱ)配合物的合成和结构 总被引:2,自引:1,他引:2
配合物[UO2(Bu2NCOCH2CONBu2)(NO3)2]晶体属单斜晶系,P21/c空间群,a=10.744(2),b=13.229(5),c=20.011(8)β,β=99.21(3)°,V=2808(2)β3,Dc=1.07g·cm-3,Z=4,配合物分子中具有直线结构的铀酰离子由六个氧原子配位,其中四个来自硝酸根,另外两个来自羰基,形成平面六角形,六角形的平面与铀酰离子的直线垂直,两个硝酸根处于相邻位置. 相似文献
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本文合成了间亚苯基桥接的席夫碱型双-(苯并15-冠-5)苦味酸铷配合物以及测定了其晶体结构.实验证明该晶体属单斜晶系,P21/n空间群,晶胞参数:a=19.3049(49)Å,b=20.4544(39)Å,c=25.4375(75)Å,β=107.925(21)°,V=9556.90Å3,F(000)=4175.41(e),Dc=1.455g/cm3.对8172个可观测反射精修所有的结构参数,最后偏离因子R=0.0781.此双冠醚以反-反式构型与Rb+离子形成4:2(冠醚单元:阳离子)分子间夹心结构配合物,Rb1和Rb2分别与两个双冠醚分子中不同取向的醚环的十个氧原子配位.Rb-O平均键长为2.986和2.998Å,并与席夫碱型双冠醚苦味酸钾配合物进行比较. 相似文献
11.
Polymerization of p-acetoxybenzoic acid between mica sheets, from both the melt and dilute solution, in a wide range of polymerization temperatures (180–400°C) yields an epitaxial-like overgrowth of PpOBA on the mica cleavage surface. The PpOBA overgrowth forms long rows by lateral aggregation of ribbon crystals situated in three substrate directions rotated by 60°. The c-axes of the PpOBA phase I and II lattices are parallel to the 001 plane of the mica, coinciding with the a-axes of the mica hexagonal structure. The aI- and bII-axes lie predominantly on the mica surface. The surface-orienting effect is tentatively attributed to surface steps and or/polar effects; lattice matching does not occur. The recrystallization of bulk polymer samples previously prepared also leads to ordering between mica like that in melt or solution polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1807–1820, 1997 相似文献
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We have investigated tension wood cellulose obtained from Populus maximowiczii using X-ray diffraction at temperatures from room temperature to 250 °C. Three equatorial and one meridional d-spacings showed a gradual linear increase with increasing temperature. For temperatures above 180 °C, however, the equatorial
d-spacing increased dramatically. Thus, the linear and volume thermal expansion coefficients (TECs) below 180 °C were determined
from the d-spacings. The linear TECs of the a-, b-, and c-axes were: α
a
= 13.6 × 10−5 °C−1, α
b
= −3.0× 10−5 °C−1, and α
c
=0.6× 10−5 °C−1, respectively, and the volume TEC was β = 11.1× 10−5 °C−1. The anisotropic thermal expansion in the three coordinate directions was closely related to the crystal structure of the
wood cellulose, and it governed the macroscopic thermal behavior of solid wood. 相似文献
13.
F. Honda G. Oomi A. V. Andreev K. Prokeš L. Havela V. Sechovský 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(3):441-444
The linear thermal expansion, compressibility and magnetostriction of UNiGa have been measured under high pressure. Huge anisotropic
behaviors are observed in these physical quantities. The linear thermal expansion coefficients are α
a
∼ 16·10−6 K−1 along thea-axis anda
c
∼5·10−6 K−1 along thec-axis, and the linear compressibilities at room temperature are κ
a
∼ 3.6·10−3 GPa−1 and κ
c
∼ 1.7·10−3 GPa−1 alonga-axis andc-axes, respectively. UNiGa orders antiferromagnetically belowT
N=39 K and shows a metamagnetic transition at 4.2 K in magnetic fieldB
C=1 T. It is found thatT
N decreases andB
C increases with increasing pressure. 相似文献
14.
The formation of facets in domains of three monolayer systems, differing in molecular structure or headgroup charge, is observed
by Brewster-angle microscopy under different experimental conditions. Arachidic acid forms faceted domains on increasing the
pH of the subphase from pH 12.0 to 12.3 or by adding traces of cholesterol at pH 12.0. The degree of faceting is gradually
varied in a mixture of 1-monopalmitoyl-rac-glycerol and 1-O-hexadecyl-rac-glycerol. The surface potentials of the pure substances were measured in order to determine the electrostatic forces in the
mixture. Reversible faceting of domains of heptadecanoic acid methyl ester is observed within 2 °C near 30 °C. Faceting in
monolayers is explained on the basis of fundamental forces that govern domain texture and shape, including line tension anisotropy
and electrostatic repulsive forces. This explanation also accounts for the formation of dendrites along certain directions
at domains of arachidic acid and the methyl ester.
Received: 9 August 1999/Accepted in revised form: 24 August 1999 相似文献
15.
E. P. Styngach S. T. Malinovskii L. P. Bets L. A. Vlad M. Gdanets F. Z. Makaev 《Journal of Structural Chemistry》2005,46(4):765-769
Crystal and molecular structure of a new homodrimanic compound (1S,2S,4aS, 8aS)-N-(N-allyldiaminomethanethione)-1-(2-hydroxy-2,5,5,8a-tetramethyldecahydronaphthalenyl) acetamide has been determined by X-ray
diffraction analysis. The crystal is monoclinic, unit cell parameters are: a = 9.577(2) Å, b = 7.414(1) Å, c = 16.856(3) Å; β = 94.83(3)°, space group P21, Z = 2, of composition C20H35N3O2S. Two cyclohexan fragments have ordinary structure and chair-configuration typical of this compound class in homodrimanic
skeleton. Ethanol molecule is located in the outer sphere. The withdrawal of carbon atoms from planar fragments of cyclohexan
rings varies within the limits from 0.722(5) Å to − 0.634(5) Å. A dihedral angle between the mean-square planes of the latter
equals 16.0(2)°, torsion angle (5)-(5)-(10)-(16) 171.0(1)° indicates their trans-joint. In the side non linear chain allyl group is connected to terminal nitrogen atom of thiosemicarbazide molecule. Intermolecular
hydrogen bonds between carbonyl atom of acetamide fragment, ethanol molecule, and donor-acceptor groups of thiosemicarbazide
moiety play the main part in crystal structure organization.
Original Russian Text Copyright ? 2005 by E. P. Styngach, S. T. Malinovskii, L. P. Bets, L. A. Vlad, M. Gdanets, and F. Z.
Makaev
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 4, pp.785–789, July–August, 2005. 相似文献
16.
The specific micro- and mesopore volumes (V) of alumina compacts fired between 900 and 1250 °C for 2 h were determined from nitrogen adsorption/desorption data. The
V value was taken as a sintering equilibrium parameter. An arbitrary sintering equilibrium constant (K
a) was estimated for each firing temperature by assuming K
a = (V
i − V)/V, where V
i is the largest value at 900 °C before sintering. Also, an arbitrary Gibbs energy (ΔG
a
°) of sintering was calculated for each temperature using the K
a value. The graph of ln K
a versus 1/T and ΔG
a
° versus T were plotted, and the real enthalpy (ΔH°) and the real entropy (ΔS°) of sintering were calculated from the slopes of the obtained straight lines, respectively. On the contrary, real ΔG° and K values were calculated using the real ΔH° and ΔS° values in the ΔG° = −RT lnK = 165814 − 124.7T relation in SI units. 相似文献
17.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide was synthesized from 3-chlorobenzo[b] thiophene -2-carboxyl chloride and 8-aminoquinoline in the presence of triethylamine. The single crystal X-ray structure
determination confirmed the earlier proposed structure and also characterized by 1HNMR, and Mass spectroscopy. Crystallographic study reveals that the structure crystallizes in monoclinic system, a = 14.878(4) ?, b = 8.4292(15) ?, c = 25.461(7) ?, β = 112.022(18)°, Z = 8, V = 2960.20(12) ?3 with space group C2/c (No. 15). In the structure packing, three kinds of interactions are responsible for the stability of the structure. Infinite
two-dimensional stair-like layered chains are formed by relatively strong intermolecular hydrogen bonds [C14—H14...O1]. These
parallel chains are connected by several π—π and CH—π interactions, alternatively. There are two such parallel chains with
70.53°, which are in contact by van der Waals interactions. 相似文献
19.
Pascale Bénézeth Donald A. Palmer David J. Wesolowski 《Journal of solution chemistry》1997,26(1):63-84
The three molal dissociation quotients for citric acid were measured potentiometrically with a hydrogen-electrode concentration
cell from 5 to 150°C in NaCl solutions at ionic strengths of 0.1, 0.3, 0.6, and 1 molal. The molal dissociation quotients
and available literature data at infinite dilution were fitted by empirical equations in the all-anionic form involving an
extended Debye-Hückel term and up to five adjustable parameters involving functions of temperature and ionic strength. This
treatment yielded the following thermodynamic quantitites for the first dissociation equilibrium at 25°C: logK
1a=−3.127±0.002, ΔH
1a
o
=4.1±0.2 kJ-mol−1, ΔS
1a
o
=−46.3±0.7 J-K−1-mol−1, and ΔCp
1a
o
=−162±7 J-K−1-mol−1; for the second acid dissociation equilibrium at 25°C: logK
2a
=−4.759±0.001, ΔH
2a
o
=2.2±0.1, ΔS
2a
o
=−83.8±0.4, and ΔCp
2a
o
=−192±15, and for the third dissociation equilibrium at 25°C: logK
3a=−6.397±0.002, ΔH
3a
o
=−3.6±0.2, ΔS
3a
o
=−134.5±0.7, and ΔCp
3a
o
=−231±7. 相似文献