纳米二氧化钛粉末的溶胶-凝胶法合成及晶相转化

Nanosized TiO₂ powder with anatase and rutile structures was synthesized by a sol-gel method using TiCl₄ ethanol solution as a precursor.The grain size of TiO₂ powder was about 63nm after the precursor was calcined at 600℃ for 2 hours .The experimental techniques of XRD,TEM and Particle Distribution were used to characterize the synthesized specimens. Various special effects were investigated for their contribution to crystal structure and the size of TiO₂ powder .The formation of anatase as well as the rutile phase of TiO₂ was indicted from the XRD when the reaction temperature was above 30℃ and when the sol was irradiated by infrared rays .However, an anatase TiO₂ powder formed after the heat treatment of the dried gel in a temperature range from 300℃ to 500℃.Under the vacuum drying and with the calcined time below 3hours ,the anatase phase was gained .As well as with the increase of gelatinizing time, the anatase TiO₂ powder was obtained.     

介稳态氧化钨超微粉体的水热合成与光致变色性质研究

Under hydrothermal conditions, the superfine powders of cubic pyrochlore-type of tungsten oxide and hexagonal tungsten bronze were obtained by using Na₂WO₄·2H₂O as the starting material. The products were characterized by XRD, TG, IR, UV and EPMA, respectively. The effects of the pH value, the acid concentration, reaction temperature and time on the structure and particle size of products were investigated in detail. The conditions for the preparation of superfine powders of tungsten oxide were optimized. The pH 2.5～4.5 of the reaction system led to the formation of a pyrochlore phase and pH 0.5～2.0 gave the hexagonal tungsten bronze structure. The photochromism property of the hexagonal tungsten bronze was studied. The results show that pyrochlore and bronze phases are decomposed at 300 ℃ and 450 ℃, respectively. With the increasing of temperature, the structure of the two oxides changes. The pyrochlore-type powder changes completely into triclinic Na₂W₄O₁₃ around 500 ℃, while the bronze phase into a mixture of Na₂W₆O₁₉ and triclinic WO₃ at 550 ℃. The powder of the hexagonal tungsten bronze showed better photochromism property.     

Solution thermolysed tungsten oxide-based electrochromic devices: thickness-dependent step potential analysis

The characterisation of electrochemical behaviour of electrochromic (EC) devices based on solution thermolysed (ST) tungsten oxide (WO₃) thin films was carried out using the step potential excitation method. The method, based on generating plots of current density (J) as a function of passed charge (ΔQ), has been applied for the characterisation of EC-WO₃ thin films in proton-containing aqueous electrolyte. EC devices have been fabricated by employing WO₃ thin films with variable thickness (T) ranging from 0.04 to 0.52 μm. The J vs time (t) responses (chronoamperometry) of these devices were recorded at a fixed applied potential (±0.7 V vs S.C.E.) and values of total passed H⁺ charges (ΔQ) into the WO₃ host lattice during the coloration process are calculated. The J-ΔQ curves corresponding to films of different thickness were plotted as a function of the passed charge volume density, ΔQ /T, and an intercalatable film thickness is calculated to be 0.13 μm. The modulation in optical transmittance after coloration and bleaching was studied in the wavelength range between 350 and 850 nm and an optical efficiency (ξ_λ) is calculated at λ=700 nm. It is found that the ξ_λ wanes with increasing intercalation. Electronic Publication     

混合价钨氧化物的制备及其性质研究

Precursors were synthesized with hydrazine oxalic acid and tungstic acid in different ratios and a series of tungsten oxides， O/W ratios from 2.90 to 2.30，were obtained by thermal decomposition from the precursors under nitrogen atmosphere at 640～760℃. This kind of tungsten oxides were found to belong to mixed valence compounds which have some special electrical properties. The experimental result indicated that the electrical conductivity of this tungsten oxide has a close relation with its O/W ratio and reach the maximum at WO_2.50. Seclecting WO_2.50 as an example， its conductivity was measured at different temperatures from -197 ℃ to -2.5 ℃ and it was found that the mixed valence tungsten oxide as conductor belongs to the class of metal ones. Owing to their relatively high electrical conductivity and stability in air， mixed valence tungsten oxide shows some potential use in polymer products as additives.     

一种新的光致变色膜：Na2WO4-PAA-Glycerol体系研究

A method for preparing Na₂WO₄-PAA-Glycerol photochromic films was reported. The film was composed of Na₂WO₄, PAA and Glycerol, which were coated on a glass substrate. The film turned blue in the sun, and bleached to transparent in the darkness. The UV-Visible spectra showed strong absorbance at 300～500 nm, and the ABS changed signifanctly at 500～800 nm. The film showed the best photochromic behavior when n_Na2WO4∶n_PAA is 4%～5%. The mechanism was suggested that after irradiation, poly tunstate produced by Na₂WO₄ and PAA formed the tungsten blues. The tungsten blues were bleached due to oxidation back to poly tunstate by oxygen. The film showed not only an excellent photochromism property with rapid response and good reversibility, but also the simple techniques and good stability.     

用稀土多元渗法制备钾稀土钨青铜KxLayWO3的XPS研究

Potassium tungsten bronze K_xLa_yWO₃ (x>0.5 and y<0.01) was synthesized by rare earth co-permeation method using α-K₇[SiMg₃(OH₂)₃W₉O₃₇] as the precursor. Binding energies of La, W, O and C were determined by XPS. From the XPS data, a peak at 34.21 eV indicates that some W⁶⁺ turned into W⁵⁺ by rare earth co-permeation. The binding energies La3d were the same in the surface and inner of the composite, showing that rare earth element La could diffuse into the body of the composite and the compound of K_xLa_yWO₃ was formed at the same time. The binding energies of O1s in K_xLa_yWO₃ surface were 531.4 eV and 532.0 eV, respectively, while peak at 531.4 eV disappeared through etching process. The result implies that the binding energy of 531.4 eV was due to the adsorbent O. In addition, the binding energies of C1s in the surface were 283.5 eV, 285.0 eV and 286.7 eV respectively, while the inner had only one peak at 285.0 eV due to standard C1s. This proves that there was no C in the core.     

PMW-PNN-PT陶瓷的制备及介电性能研究

0.29Pb(Mg_1/2W_1/2)O₃-0.41Pb(Ni_1/3Nb_2/3)O₃-0.30PbTiO₃ ＋ 0.002 5MnO₂＋xWO₃(PMW-PNN-PT) ceramics were prepared by Semichemical Method. The Mg(Ac)₂, Ni(Ac)₂, and Mn(NO)₃ solution rather than MgO, NiO and MnO₂ were added to the slurry of PbO, WO₃, Nb₂O₅ and TiO₂ and then calcined at 850 ℃ for 2 h. Then the sample was sintered at 1 100～1 200 ℃ for 2 h. The effect of sintering temperature and WO₃-excess amounts on the phase constitute, microstructure and the dielectric characteristics was investigated. The result showed that the PMW-PNN-PT powders with pure pervoskite phase were prepared by single-step calcination. The development of sintered temperature contributes to the increase of dielectric constant and the flatness of dielectric temperature dependence. But the dielectric properties will be worse if the sintered temperature is too high. The increase of WO₃-excess level lead to an increase of Pb₂WO₅ phase and the flatness of dielectric curves, but the dielectric constant will be decreased. The proper WO₃-excess amount of X7R type PMW-PNN-PT ceramics is 5mol% and the proper sintering condition is 1 150 ℃ for 2 h, the maximum dielectric constant is 5 395.     

溶胶-凝胶法制备掺锰钛酸钡纳米粉体及其陶瓷

The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD， SEM and TEM. The dielectric properties of the ceramics were also measured. The influences of calcination temperature and Mn concentration on the microstructure， dielectric properties and phase composition of BaTiO₃ nano-powders and ceramics were discussed. The results indicated that the BaTiO₃-based powders doped with 1.0mol% Mn were mainly in cubic BaTiO₃ phase， but the tetragonal phase became more evident when the calcination temperature increased. After sintering， Mn-doped ceramics were mainly composed of cubic BaTiO₃. Specially， a new phase of hexagonal crystal BaTiO₃ and BaMnO₃ existed in the ceramics doped with 5.0mol% Mn and the ceramic grains were in ‘clintheriform’. The structure of ‘clintheriform’ led to the poor densification of ceramics， reducing the dielectric constant obviously. The dielectric constants of BaTiO₃ ceramics first increased and then decreased as the Mn concentration increased. The room temperature dielectric constant was 2 290 and the lowest dielectric loss was 0.004 when the Mn concentration was 0.5mol%.     

针状TiO2锐钛矿晶粒溶胶的制备、结构及形成机理研究

The PTA sol was prepared using titanyl sulfate(TiOSO₄), peroxide (H₂O₂) and ammonia (NH₃·H₂O) as raw materials. The semitransparent, light yellow AS(autoclaved sol) with ultra-fine needle-like anatase crystals was synthesized by autoclaving the PTA sol at 80～100 ℃ for different times. The anatase crystals were needle-like and 80 nm in length, 20～30 nm in diameter. The FTIR, XRD, SEM were used to analyse the chemical structure, properties of the AS and influencing factors during the sol preparation. The mechanism model of the AS formation was established based on the inorganic and crystal structural chemistry. The PTA molecules were decomposed to form Ti⁴⁺ under hydrothermal conditions and the Ti⁴⁺ were hydrated with water to get [Ti(OH)₄(OH₂)₂]⁰, a growing units of the anatase crystals. The appearance of the needle-like anatase crystals and the anatase precipitate are also explained in this paper.     

纳米晶PbTiO3负载CuO催化NO分解

A large specific surface area perovskite-type mixed oxide PbTiO₃ supported cupric oxide was synthesized as a catalyst for NO decomposition and characterized by techniques such as XPS, XRD, H₂-TPR before and after NO decomposition reactions. The catalytic properties were tested with a fix-bed micro-reactor. The results showed that the PbTiO₃ was inactive for the reactions, but 1wt % Cu/PbTiO₃ catalyst gave fairly good activities for NO decomposition at temperature as low as 473 K. Copper species were found well-dispersed but weakly interacted with the support before NO decomposition, and the NO decomposition caused significant change in the environment of the copper species, which became Cu(Ⅰ) and most probably incorporated into surface crystal lattice of the nano-sized PbTiO₃. In NO reaction, a large amount of oxygen atoms from the decomposition of NO penetrated into the nano-sized PbTiO₃ support and caused small expansion of crystal lattice. The transport of oxygen between the copper species and the catalyst support may be helpful to speed up the kinetic regeneration of active metal sites from oxygen occupancy and resulted in good catalytic performance.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.