共查询到20条相似文献,搜索用时 15 毫秒
1.
The solubilities of the ternary system,Yb(NO_3)_3·3H_2O-B15C5·C_2H_5OH, at 18 ℃ have been investigated by the modified semimicro method for study of phase equilibrium. The results indicated that there are two solubility curves for this ternary system: the long one corresponds to the solid phase of the complex (Yb(NO_3)_3·B15C5·3H_2O·2.5C_2H_5OH), and the short one to the solid phase of B15C5. The curve of refractive indexes for saturated solutions consists of two branches, which correspond with two branches with solubility curve. We have not found other complex species having different ratio, Yb/crown.The behavior of water for this system in equilibrium has been examined. The results are: the mole ratio, H_2O/Yb(NO_3)_3, no matter whether it is in liquid phase or solid phase, is alwaysl 3:1.The complex has been isolated from organic solvent, C_2H_5OH. The composition of this complex has been determined by chemical analysis and it is Yb(NO_3)_3·B15C5·3H_2O·0.65C_2H_5OH. The properties of this complex have been investigated by chemical analysis, infrafed spectra, DTG and TG. 相似文献
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Coronado E Curreli S Giménez-Saiz C Gómez-García CJ Deplano P Mercuri ML Serpe A Pilia L Faulmann C Canadell E 《Inorganic chemistry》2007,46(11):4446-4457
The paramagnetic and chiral anion [Fe(C5O5)3]3- (C5O52-=croconate) has been combined with the organic donor BEDT-TTF (=ET=bis(ethylenedithio)tetrathiafulvalene) to synthesize a novel paramagnetic semiconductor with the first chirality-induced alpha phase, alpha-(BEDT-TTF)5[Fe(C5O5)3].5H2O (1), and one of the few known paramagnetic molecular metals, beta-(BEDT-TTF)5[Fe(C5O5)3].C6H5CN (2). Both compounds present layers of BEDT-TTF molecules, with the alpha or beta packing modes, alternating with layers containing the high-spin S=5/2 Fe(III) anions and solvent molecules. In the alpha phase, the alternation of the chiral [Fe(C5O5)3]3- anions along the direction perpendicular to the BEDT-TTF chains induces an alternation of the tilt angle of the BEDT-TTF molecules, giving rise to the observed alpha phase. The alpha phase presents a semiconductor behavior with a high room-temperature conductivity (6 S.cm-1) and an activation energy of 116 meV. The beta phase presents a metallic behavior down to ca. 120 K, where a charge localization takes place with a reentrance to the metallic state below ca. 20 K followed by a metal-semiconductor transition at ca. 10 K. The magnetic properties are dominated by the paramagnetic S=5/2 [Fe(C5O5)3]3- anion with an extra Pauli-type paramagnetism in the metallic beta phase. The ESR spectra confirm the presence of the high-spin Fe(III)-containing anion and show a progressive localization in the organic sublattice along with an antiferromagnetic coupling below ca. 120 K that, in the metallic beta phase, could be at the origin of the transition from the metallic to the activated conductivity regime. The correlation between crystal structure and conductivity behavior has been studied by means of tight-binding band structure calculations which provide a rationalization of the charge distribution and conductivity results. 相似文献
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新型低聚噻吩衍生物的设计、合成及其液晶性能的研究 总被引:3,自引:0,他引:3
设计、合成了一系列新型低聚噻吩衍生物N,N’-双烷烃基-5,5’-二溴基-2 ,2’:5’,2’-三噻吩-4,4’-二酰胺[N,N’-dialkyl-5,5’-dibromo-2,2’:5 ’,2’-terthiophene-4,4’-dicarboxamide](DNCnDBr3T,n=5,8,6,18)。示差扫描 量热法(DSC)测定的结果及偏光光学显微镜观察的结果显示,DNC18DBr3T, DNC16DBr3T,DNC8DBr3T具有近晶A形液晶性质,DNC5DBr3T不具有液晶性质。为了探 讨分子间氢链对液晶形成的影响,设计、合成了新型低聚噻衍生物4,4“-双烷烃 酯-5,5“-二溴基-2,2’:5’,2’-三噻吩[4,4’-bis(alkyloxycarbonyl)-5,5’ -dibromo-2,2’:5’,2’-terthiophene](DOCnDBr3T,n=5,8,16,18).测定和观察的 结果发现,DOCnDBr3T(n=5,8,16,18)不具有液晶的结果。这个结果表明,酰胺基 的存在于液晶的形成起着重要的作用。测定DNC18DBr3T在结晶状态和液晶状态下的 红外光谱,进一步证实了部分分子间氢键对于液晶的形成起着重要的作用。 相似文献
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Alireza Najafi Chermahini Masoud Nasr-Esfahani Zeinab Dalirnasab Hossein Abdol Dabbagh Abbas Teimouri 《Journal of Molecular Structure》2007,820(1-3):7-11
Computational calculations at B3LYP/6-31++G(d,p) level were employed in the study of the predominant tautomeric forms of 1-H and 2-H tetrazole derivatives (5-NO2, 5-CF3, 5-F, 5-H, 5-NH2, 5-OH, 5-CH3) in the gas phase and solution using PCM model. For electron withdrawing derivatives in the gas phase and solution 2-H forms are more stable and dominant form. For electron releasing groups in the gas phase and solution with low dielectric constants the 2-H form is more stable but in solvents with high dielectric constants 1-H isomer is dominant form. In addition variation of dipole moments and charges on atoms in the solvents are studied. 相似文献
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The Sr3Tl5 phase was prepared by high temperature synthesis techniques through reaction of the high purity elements in the welded Nb tubes.The structure established through X-ray structural analysis shows the compound is a good hypoelectronic trielide example of the Pu3Pd5 structural type in which skeletal electron count is lower than in a traditional Zintl phase(Cmcm,Z = 4;a = 10.604(2) ,b = 8.675(2) ,and c = 10.985(2) ;V = 1010.5(3) 3).The strontium size and the compound’s polarity appear responsible for this thallium phase crystallization in the Pu3Pd5 family type rather than the isoelectronic Sr3In5 version.A first-principle electronic structure calculation(LMTO) demonstrates that the strontium atoms participate substantially in Sr-Tl bonding in the structure. 相似文献
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拟三元相图的研究可为获得制备纳米材料的微乳液提供理论依据。本文首先通过实验绘制了45℃下十二烷基硫酸钠(SDS)/正戊醇-环己烷-水溶液体系的拟三元相图,并用电导法进行了验证,说明电导的测定结果与相图吻合的很好。其次,绘制了45℃及65℃下,SDS/正戊醇-环己烷-水、SDS/正戊醇-环己烷-硝酸锌水溶液和SDS/正戊醇-环己烷-氢氧化钠水溶液体系的拟三元相图并对6个相图进行了比较,研究了碱(NaOH)和盐(Zn(NO_3)_2)对SDS/正戊醇-环己烷-水拟三元体系相图影响。结果表明,硝酸锌及碱的加入使SDS/正戊醇-环己烷-水拟三元相图水包油(O/W)和油包水(W/O)区域明显的缩小。45℃时,SDS/正戊醇-环己烷-氢氧化钠水溶液体系的拟三元相图中的O/W区域甚至消失;65℃时,O/W和W/O区域均存在,且3个相图的W/O和O/W区域有重叠区。在此基础上,确定了制备纳米Zn O的微乳液的条件,即SDS/正戊醇-环己烷-硝酸锌水溶液和SDS/正戊醇-环己烷-氢氧化钠水溶液体系的拟三元相图中W/O区域的重叠区(各相图中的Ⅱ区)。制备的纳米氧化锌为多晶结构,平均粒径为80 nm。 相似文献
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Tam-Chang SW Helbley J Iverson IK 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):2133-2139
Ionic perylenebis(dicarboximide)s 1-5 were synthesized. The aggregation and liquid-crystalline properties of these compounds in aqueous solutions were investigated. In the concentration range of approximately 5 x 10-7-5 x 10-4 M, the structures of the ammonium side chains and counterions did not have a significant effect on the electronic transition properties and H-aggregate formation of these compounds. However, the liquid-crystalline phase properties varied with the structure of the side chains and the counterions. Ionic perylenebis(dicarboximide)s 1, 3, and 5 with chloride ions formed nematic (N) phases from the isotropic (I) phase, while 2 and 4 with p-methylbenzenesulfonate ions formed chromonic ribbons from the I phase. Studies by polarized light microscopy and 2H NMR spectroscopy indicated that the N phase of 5 (with gem dimethyl groups) formed at higher concentrations than those observed for 1 and 3 at the same temperature. Furthermore, the N phase of 5 was less ordered compared to those of 1 and 3 at a similar concentration and temperature, presumably due to the bulkiness of the side chains of 5 that hindered the stacking and pi-interactions of the aromatic rings. 相似文献
9.
P. Pardhasaradhi D. Madhavi Latha P. V. Datta Prasad G. Padmaja Rani P. R. Alapati V. G. K. M. Pisipati 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1483-1490
As a part of the systematic studies on symmetric liquid crystal dimer homologous series, α,ω-bis-(4-n-alkylaniline benzylidene-4′-oxy) alkanes, (referred to as m.OnO.m with m = 3, 4, and 5; and n = 8, 9, and 10), we present in this article the nature of phase transitions across isotropic–nematic and nematic–smectic-A (N–SmA) phases exhibited by the just mentioned compounds. The methods employed are differential scanning calorimetry and dilatometry. The compounds studied were 3.O8O.3, 4.O8O.4, and 5.O8O.5; and 3.O9.03, 5.O9O.5, 3.O10O.3, 4.O10O.4, and 5.O10O.5. Different from the case of their corresponding monomers, all these compounds exhibit a nematic phase only with the exception of 5.O8O.5 which exhibits a SA phase in addition to the nematic phase. The phase transitions viz., isotropic–nematic transitions studied in all these compounds were confirmed to be of first-order nature, whereas the N–SmA transition exhibited by the compound 5.O8O.5 only was found to be of second-order nature. We also report in this article the calculated density jumps, thermal expansion coefficient maxima, and pressure dependence of transition temperatures which are analyzed in the light of the available literature data. 相似文献
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Katsufumi Tanaka Yuichiro Tanabe Takatoshi Morina Ryuichi Akiyama 《Liquid crystals》2008,35(3):253-264
Solid cast films with polydomain textures were prepared on a glass substrate with transparent interdigitated electrodes from an isotropic aqueous solution of hydroxypropyl cellulose via its liquid crystalline phase under the sinusoidal electric field with small amplitude and frequency of 0.05 V µm-1 and 105 Hz, respectively. The process was monitored using microdielectrometry as well as polarised optical microscopy. The apparent dielectric constant εr' and loss factor εr' sensitively changed with time depending on the process conditions. On the other hand, the logarithmic relation between εr' and εr' showed a single curve, when they were normalised by an effective portion of the electrostatic energy density estimated using each solid-film thickness. The conversion to the solid film was estimated during the process based on the concentration dependences of εr' and εr'. Characteristic times were reported for the onset of the biphasic phase, fully developed cholesteric phase and termination of the process. 相似文献
12.
本文测定了三元体系NH4Cl-SbCl3-HOAc在25℃时平衡态和介稳态的溶度及部分饱和溶液的折光指数, 并绘制了相应的溶度图. 体系在稳定平衡态时有五种固相: NH4Cl、SbCl3(原始盐), 5NH4Cl-SbCl3(1)、2NH4Cl-SbCl3.5HOAc(2)和5NH4Cl-3SbCl3.2.5HOAc(3)(复盐). 一支介稳溶度曲线所对应的固相是3NH4Cl.SbCl3(4). 本文初步描述了以上四种复盐的一些物理化学性质. 体系中合成的二元复盐1和溶剂合复盐2与3文献中均未见报道. 本文提供了一种制备3NH4Cl.SbCl3的新方法. 相似文献
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Ti3O5 shows a first-order phase transition from the monoclinic structure to the pseudobrookite structure at 448°K, at which temperature a magnetic susceptibility anomaly has been reported earlier in the literature. There is an electrical conductivity discontinuity accompanying the phase transition. Incorporation of Fe stabilizes the high-temperature phase of Ti3O5; while with 2% Fe the transition temperature and enthalpy change are lowered, with 5% Fe there is no transition. Mössbauer spectra of 2% Fe-doped Ti3O5 are similar below and above the transition temperature and show no evidence for magnetic ordering in the low-temperature phase. These results are compared to the VO2 transition. 相似文献
14.
Varadwaj KS Seo K In J Mohanty P Park J Kim B 《Journal of the American Chemical Society》2007,129(27):8594-8599
We report the synthesis of single-crystalline nanowires (NWs) of metastable Fe5Si3 phase via an iodide vapor transport method. Free-standing Fe5Si3 NWs are grown on a sapphire substrate placed on a Si wafer without the use of any catalyst. The typical size of the Fe5Si3 nanowires is 5-15 microm in length and 100-300 nm in diameter. Synthesis of the metastable phase is induced by composition-dependent nucleation from the gas-phase reaction. Depending on the concentration ratio of FeI2(g) to SiI4(g), different phases of iron silicides are formed. The growth of nanowires is facilitated by the initial nucleation of silicide particles on the substrate and further self-seeded growth of the NWs. The present work not only provides a method for the synthesis of metastable Fe5Si3 nanowires but also suggests that the phase controlled synthesis can be further optimized to produce other metal-rich silicide nanostructures for future spintronic devices. 相似文献
15.
The complex permittivity of a room-temperature ferroelectric liquid crystal 4-n-octyloxy benzoic acid 4'-[(2-methylbutyloxy)carbonyl]phenyl ester, has been measured in the vicinity of the phase transition in the frequency range 40 Hz-300 kHz. In the para-electric phase the contribution εs of the soft mode to the permittivity and the soft-mode relaxation frequency fs satisfy the Curie-Weiss law. Under a biasing field E, the helicoidal structure is unwound, and εs and fs can then be measured even in the ferroelectric phase. On the other hand, the phase transition is smeared under the influence of E. This smearing results in deviations from the Curie-Weiss law for both εs and fs in the vicinity of the transition. On increasing E, the maximum of the permittivity, εmax, is lowered and shifted to higher temperatures. Both the shift and ε-1max are proportional to E2/3. From experimentally found dependences, some constants in the free energy are determined. 相似文献
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在SrO-Ln2O3-TiO2-Nb2O5(Ln=La, Y)体系中,通过固相反应法,合成了填满型钨青铜结构新铌酸盐Sr5LaTi3Nb7O30与Sr5YTi3Nb7O30.分别采用X射线衍射分析、扫描电镜进行了结构分析,并进行了介电性能测试.结果表明, Sr5LaTi3Nb7O30室温时为四方钨青铜结构顺电相,晶胞参数a=1.233 60(4) nm, c=0.388 01(2) nm;频率为1 MHz时,其陶瓷的室温相对介电常数为466,介电损耗约为5×10-3.Sr5YTi3Nb7O30为弛豫性铁电体, 10 kHz时居里温度为260 ℃;室温时为四方钨青铜结构铁电相,晶胞参数a=1.228 80(4) nm, c=0.387 05(2) nm; 1 MHz时,陶瓷体的室温相对介电常数为290. 相似文献
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The phase behavior of the water/poly(oxyethylene)-poly(dimethylsiloxane) copolymer (Si25C3EO51.6)/pentaoxyethylene dodecyl ether (C12EO5) ternary system has been studied. Both the silicone copolymer and the surfactant have equal volumes of hydrophilic and lipophilic parts; i.e., these are balanced amphiphiles. Although only a lamellar phase is observed in water-Si25C3EO51.6 and water-C12EO5 binary systems, a variety of liquid crystalline phases, including normal micellar cubic (I1), hexagonal (H1), bicontinuous cubic (V1), lamellar (L(alpha)), reverse bicontinuous cubic (V2), and reverse hexagonal (H2), are observed in the copolymer-rich region of the ternary phase diagram. The small C12EO5 molecules dissolve at the hydrophobic interface in the thick bilayer of the Si25C3EO51.6 L(alpha) phase occupying a large area of the total interface of the aggregates and modulate the curvature of the aggregates. Hence a variety of self-assembled structures are observed. In contrast, Si25C3EO51.6 is not dissolved in the thin bilayer of the C12EO5 lamellar phase (L'(alpha)). Hence, the C12EO5 L'(alpha) phase coexists with copolymer-rich L(alpha) and H2 phases. Consequently, small surfactant molecules are dissolved in a large silicone copolymer aggregate to induce a change in layer curvature, but a large copolymer molecule is hard to incorporate with surfactant aggregates. 相似文献
18.
The flash high speed counter-current chromatographic (FHSCCC) separation of gingerols and 6-shogaol was performed on a HSCCC instrument equipped with a 1200-ml column (5 mm tubing i.d.) at a flow rate of 25 ml/min. The performance met the FHSCCC feature that the flow rate of mobile phase (ml) is equal to or greater than the square of the diameter of the column tubing (mm). The separation employed the upper phase of stationary phase of the n-hexane-ethyl acetate-methanol-water (3:2:2:3, v/v) as the stationary phase. A stepwise elution was performed by eluting with the lower phase of n-hexane-ethyl acetate-methanol-water (3:2:2:3, v/v) for first 90 min and the lower phase of the n-hexane-ethyl acetate-methanol-water (3:2:6:5, v/v) for the second 90 min. In each separation 5 g of the ethyl acetate extract of rhizomes of ginger was loaded, yielding 1.96 g of 6-gingerol (98.3%), 0.33 g of 8-gingerol (97.8%), 0.64 g of 6-shogaol (98.8%) and 0.57 g of 10-gingerol (98.2%). The separation can be expected to scale up to industrial separation. 相似文献
19.
The phase behaviour of the discotic mesogen 5,10,15,20-tetrakis(4-n -dodecylphenyl)porphyrin (C12TPP) was investigated under hydrostatic pressures up to 300MPa by high pressure DTA and wide angle X-ray diffraction methods. The typical enantiotropic phase transitions of C12TPP, low- to high-temperature crystal (Cr2-Cr1), Cr1-discotic lamellar phase (DL), and DL-isotropic liquid (I) are observed at pressures up to 10MPa. Application of hydrostatic pressure to the sample generates a pressure-induced crystal polymorph (Cr3) between the Cr2 and Cr1 phases, and the phase transitions Cr2-Cr3-Cr1-DL-I occur reversibly in the pressure region between 10 and 180MPa. On heating at higher pressures above 180MPa, the fourth crystal polymorph (Cr4) is formed between the Cr2 and Cr3 phases at lower temperatures, and at the same time the fifth crystal polymorph (Cr5) appears abruptly between the Cr1 and DL phases at high temperatures. The Cr2-Cr4-Cr3-C1-(Cr5)-DL-I transition processes were observed at 180 200MPa. Further increasing the pressure above 270MPa induces entirely different thermal behaviour: only two peaks for the pressure-induced transition between the sixth and fifth polymorphs (Cr6-Cr5) and the Cr5-I transitions are detected at low and high temperatures on heating, while both the DTA and WAXD experiments on cooling show the formation of the DL phase as a monotropic phase between the I and Cr5 phases, indicating the I DL Cr5 Cr6 process. The thermal behaviour was ambiguous and complex in the pressure region between 200 and 260MPa because the peaks for the intermediate crystal transitions were too small to detect with confidence. The two different sequences of the Cr2-Cr4-Cr3-Cr1-DL-I and Cr6-Cr5-(DL)-I processes seems to occur competitively. The T vs. P phase diagram of a sample cooled at 300MPa was studied to determine the triple point of the DL phase and to investigate the phase stability of the pressure-induced crystal polymorphs. The Cr6-Cr5-I transition process was observed on heating at 200 and 300MPa, while the Cr6-Cr5-DL-I process was detected at lower pressures below 100MPa. Since the Cr5-DL transition temperature changes linearly with a slope dT/dP 40 degrees C/100 MPa, while the DL-I transition temperature changes slightly (dT/dP 5.5 degrees C/100MPa), the DL phase forms a triangle in the T vs. P diagram. The triple point of the DL phase was found to be 240.8MPa and 168.8 C. The Cr6 polymorph reorganized to the stable Cr2 form under atmospheric pressure on annealing at room temperature overnight. 相似文献
20.
《Liquid crystals》1999,26(7):1067-1078
The phase behaviour of the discotic mesogen 5,10,15,20-tetrakis(4-n -dodecylphenyl)porphyrin (C12TPP) was investigated under hydrostatic pressures up to 300MPa by high pressure DTA and wide angle X-ray diffraction methods. The typical enantiotropic phase transitions of C12TPP, low- to high-temperature crystal (Cr2-Cr1), Cr1-discotic lamellar phase (DL), and DL-isotropic liquid (I) are observed at pressures up to 10MPa. Application of hydrostatic pressure to the sample generates a pressure-induced crystal polymorph (Cr3) between the Cr2 and Cr1 phases, and the phase transitions Cr2-Cr3-Cr1-DL-I occur reversibly in the pressure region between 10 and 180MPa. On heating at higher pressures above 180MPa, the fourth crystal polymorph (Cr4) is formed between the Cr2 and Cr3 phases at lower temperatures, and at the same time the fifth crystal polymorph (Cr5) appears abruptly between the Cr1 and DL phases at high temperatures. The Cr2-Cr4-Cr3-C1-(Cr5)-DL-I transition processes were observed at 180 200MPa. Further increasing the pressure above 270MPa induces entirely different thermal behaviour: only two peaks for the pressure-induced transition between the sixth and fifth polymorphs (Cr6-Cr5) and the Cr5-I transitions are detected at low and high temperatures on heating, while both the DTA and WAXD experiments on cooling show the formation of the DL phase as a monotropic phase between the I and Cr5 phases, indicating the I DL Cr5 Cr6 process. The thermal behaviour was ambiguous and complex in the pressure region between 200 and 260MPa because the peaks for the intermediate crystal transitions were too small to detect with confidence. The two different sequences of the Cr2-Cr4-Cr3-Cr1-DL-I and Cr6-Cr5-(DL)-I processes seems to occur competitively. The T vs. P phase diagram of a sample cooled at 300MPa was studied to determine the triple point of the DL phase and to investigate the phase stability of the pressure-induced crystal polymorphs. The Cr6-Cr5-I transition process was observed on heating at 200 and 300MPa, while the Cr6-Cr5-DL-I process was detected at lower pressures below 100MPa. Since the Cr5-DL transition temperature changes linearly with a slope dT/dP 40 degrees C/100 MPa, while the DL-I transition temperature changes slightly (dT/dP 5.5 degrees C/100MPa), the DL phase forms a triangle in the T vs. P diagram. The triple point of the DL phase was found to be 240.8MPa and 168.8 C. The Cr6 polymorph reorganized to the stable Cr2 form under atmospheric pressure on annealing at room temperature overnight. 相似文献