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1.
A new method is developed for the determination of activation energies for nucleation(E_n) and for growth of nuclei (E_g) during crystallization of amorphous alloys. This methodis based on the crystallization kinetics theory and the experimental results of the variationrelationships of local activation energy E_c(x) and local Avrami exponent n(x) with the crys-tallized volume fraction (x) during crystallization of an amorphous Ni--P alloy. Calculationresults of E_n and E_g in tbe case of crystallization of the amorphous Ni--P alloy by thismethod show that this method is not only simple in the experimental procedures, but alsoaccurate in the quantitative results.  相似文献   

2.
THE RELATIONSHIP BETWEEN RETENTION VALUES OF HOMOLOGUES AND THE COLUMN TEMPERATURE IN REVERSED-PHASE LIQUID CHROMATOGRAPHYTHE...  相似文献   

3.
A poly (vinyichloride-diethyl maleate) copolymer has been fractionated by repeated precipitation method. All fractions and the unfractionated sample have been characterized by viscometry, dynamic osmometry, Zimm static osmometry, light scattering and gel permeation chromatography. After correction for polydispersity, a [η]~M relationship for monodisperse polymer solutions has been obtained:[η]=1.99×10~(-3)M~(0.87) (ml/g, at 25℃, in cyclohcxanone)For the copolymer solution in THF, the second virial coefficient A_2 decreases as the molecular weight increases. The relationship isA_2=2 slope ((?)_n RT)~(-1/2).  相似文献   

4.
The isothermal crystallization of poly (ethylene terephthalate ) (PET),which is free of catalyst, stabilizer, oligomer and diethylene glycol (DEG), was studied by DSC. The crystallization behaviour of pure PET is different from commercial PET and a reasonable explanation is presented. The influences of catalyst, stabilizer, oligomer and DEG on the crystallization of pure PET were examined. It is shown that catalyst (Manganese acetate)and stabilizer (Triphenyl phosphite) result in an increase of the crystallization rate of PET; on the contrary, DEG and oligomer (cyclotetramer) result in a reduction of the crystallization rate. When catalyst and stabilizer coexist together, both of them promote the crystallization at lower temperature ,only a smaller effect was found at higher temperature, it is evident that metal phosphite is formed between the catalyst and stabilizer at higher temperature.  相似文献   

5.
<正> The relationships between stretching vibration frequencies (v) and distances (r) of the bonds Mo-S and Fe-Cl in ten compounds have been investigated- It is found that vMO-S is linearly related to rMo-s. This provides a convenient method to obtained bond distance data for some cluster compounds whose molecular structures could not be determined by X-ray analyses, The linear relationship between vFe-cl and rFe-cl is also discussed. The near-linear relationships of vvs. rFe-Mo and vFe-sb vs. rFe-Mo demons-trate that the formation of Fe-Sb bond has an important influence on the formation of Fe-Mo bond and the Fe-Mo distance may be estimated from v values.  相似文献   

6.
1 The structure of the bradykinin potentiating peptide component BPP_1 from a 70% methanol extract of the lyophilyzed powder of pit viper from Zhejiang Province is shown as follows: Glu·Gly·Arg·Pro·Pro·Gly·Pro·Pro·Ile·Pro·Pro2 When the pyroglutamyl residue was removed by pyroglutamate aminopeptidase, the activity of BPP_1 was enhanced two-fold but decreased gradually during the course of Edman degradation. The above facts show that the structure integrity of the C-terminal is absolutely necessary for the activity of BPP_1.  相似文献   

7.
This paper proposes that the formation of SSTA is a dynamic instability of large-scaleSST disturbance. Using a linear coupled air-sea model, in which the baroclinic atmosphere isdivided into two levels and the ocean is a mixture layer and a deep water layer, we obtainphysical conditions as well as spatial and temporal seales for the growing of SST disturbance.The major factors for the growing of SST disturbance include Sverdrup transportation, heatexchange between mixture layer and deep water, and modulation effect of clouds on solarradiations. The main horizontal scales of growing SST disturbance range from 3000 to 6000km and its temporal scales are several months. even soveral years. On the basis of thesetheoretical results, the causes for the formation of SSTA are also discussed.  相似文献   

8.
This article reports on the application of the (z/l, X) rule of chemical processes in seawater to the study of the Principle of Hard and Soft Acids and Bases (HSAB). One result is the establishment of new scales of the hardness-softness of acids and bases which are more complete than those in the literature.Based on the principle of HSAB as well as abundant experimental data, we developed a new general principle of marine chemistry viz. the principle of least . Application of the principle of least has produced good results in the study of chemical model of the major constituents of seawater, the chemical speciation of trace elements, inorganic ion exchange reactions, the Irving-Williams aeries of transition elements, etc. Our investigations indicate that chemical models of the major constituents of seawater should take into consideration the formation of chloride ion pairs.  相似文献   

9.
<正> The effects of structure on the growth habits and defective formation in the crystal of Tri-hydroxymethylaminomethane(TAM) have been studied experimentally and structurally. Dependence of orientations and properties in O - H...O and O - H....N hydrogen bridges on the polar growth and on the face development, and relationship between the structural channels in open structure and defective formation, have been dis cussed briefly.  相似文献   

10.
The heats of protonation of N-(para-substituted phenyl) glycines (R—C_6H_4—NHCH_2COOH, R=CH_3O, CH_3, H, C1) and the heats of formation of these amino acids with copper(Ⅱ) have been determined calorimetrically at 25℃ in 30% (v/v) ethanol in the presence of 0.1M sodium perchlorate. The data obtained conform nicely to the equation △H_(ML)-Q-β△H_(HL) where △H_(ML) denotes the heats of formation of complex compounds, △H_(HL) denotes the heats of protonation of the ligands, and Q and β are constants.  相似文献   

11.
The crystal-growing conditions and the results of preliminary X-ray crystallographic analysis of (L-Try)~(A1)-insulin and (D-Try)~(A1)-insulin are reported. The single crystals of this pair of insulin analogue suitable for X-ray diffraction analysis have been grown in the citrate buffer system by still-setting method. They both belong to the trigonal system with space group R3. The parameters of the unit cell (L-Trp)~(A1)-insulin are αH= 80.31, cH= 37.45 and those of (D-Trp)~(A1)-insulin αH = 79.48, cH = 43.81. There are two molecules in an asymmetric unit. The obtained results are discussed.  相似文献   

12.
The crystallization kinetics of the copolyester, poly(ethylene terephthalate) (PET) modified by sodium salt of 5-sulpho-isophthalic acid(SIPM), was investigated by means of differential scanning calorimeter. The experimental results and polari-microscopy observation all showed that the introduction of SIPM did not affect the nucleation of crystallization. Within the temperature range between their glass transition temperature T_θand melting point T_m, the crystallization rate of the copolyester sample decreased with increasing content of SIPM. The relative crystallization rate constant Z of SIPM/DMT (dimethyl terephthalate) 4mol % sample was about 1% pure PET's Z value. For isothermal crystallized copolyester samples, DSC heating curves displayed multi-melting behavior. This was interpreted by molecular weight fractionation during crystallization and premelting-recrystallization mechanism. This interpretation showed why the second melting point T_(m2) will change according to Hoffman-Weeks(H-W) equation and the first melting point T_(m1) will increase with increasing SIPM. The principal cause of these phenomena is the high temperature crystallization rate decreases rapidly with increasing SIPM.  相似文献   

13.
New binuclear copper(Ⅱ) complexes, [Cu(samen)Cu(NO_2-phen)]·H_2O and [Cu(sampn)-Cu(NO_2-phen)]·2H_2O have been synthesized, where samen~(4-), sampn~(4-) and NO_2-phen denote N, N′-ethylenedisalicylamidate anion, N, N′-1, 2-propanedisalicylamidate anion and 5-nitro-1, 10-phenanthroline respectively. 3ased on IR, elemental analyses and electronic spectra, the complexes are proposed to have a phenoxy-bridged structure and to consist of the Cu(Ⅱ)ion in distorted planar environment. The complexes have been characterized with varlable-temperature magnetic susceptibility (4—300 K) and the observed data were fit to those from a modified Bleaney-Bowers equation by least-squares method, giving the exchange integral J=-63.0 cm~(-1) (samen) and J=-46.5cm~(-1) (sampn). This indicates the existence of antiferromagnetic spin exchange interaction among the metal ions.  相似文献   

14.
A series of perovskite type oxides La_(1-x)A_(x)MnO_3(x=0.1 for A=Li,Na,K;x=0.1~0.5 for A=Li)have been prepared by impregnation.Experimental results showed that the substitution of La~(3 ) by Li~ inLaMnO_(3 ?) greatly increased the selectivity to ethane and ethylene for theoxidative coupling of methane.Temperature-programmed desorption of oxygenproved the presence of oxygen vacancies in the oxide lattice.The higher Mn~(4 )/Mn_t ratio in oxide made the formation of oxygen vacancies easier on the oxidesurface.The general formula of the oxides is La_(1-x)Li_(x)Mn'V'_(y)O_(3-y),V=vacancy.  相似文献   

15.
In this second part, the so-called "discontinuous vibration analysing" method is used to discuss the qualitative features of the solutions in the system set up in Part I. The system and the phase space are divided into two subsystems and two subspaces, which are corresponding to the slow and fast varying processes respectively. The qualitative vector field and trajectories for solutions are analysed and the mechanisms for the transition and nonuniform oscillation of high and low indexes are discussed.  相似文献   

16.
Four new types of microporous beryllophosphates werehydrothermally synthesized using BeO - P_2O_5- R - MCl (or MCl_2) - H_20, Rbeing HMDA (1, b-hexanediamine), EDA (ethylenediamine), or TBAOH(tetrabutytamine hydroxide), M alkali or alkali earth cation. By means ofX-ray diffraction patterns (XRD), infrared (IR), TG-DT and elemental analyseswe show that the crystalline beryllopbospbates have novel, unique frameworkstructures, composed from basic units of tetrahedral P0_4 and Be0_4. Thesematerials exhibit zeolite-like adsorption and ion-exchange properties.  相似文献   

17.
<正> The title compound was prepared from the corresponding elements (Sm, Nb and Se) using transport reaction with iodine at a temperature gradient of 1100/1040℃. The crystal structure was established by the single crystal X-ray diffraction technique with the following crystal data: Sm0.27Nb2.73Se4, Mr = 609. 8, hexagonal, P63/m, a = 9.997(1), c=3.470(2) A , V = 300. 4(2)A3, Z = 2, Dc= 6. 75 g/cm3, F (000) = 529. 34,μ= 292. 6cm-1, R = 0. 018, Rw = 0. 019. The ternary compound was confirmed to be isostructural with the compound Nb3Se4, and was found to be a conductor.  相似文献   

18.
乔从德 《高分子科学》2013,31(9):1321-1328
The melting and crystallization behaviors of poly(ε-caprolactone) (PCL) ultra-thin films with thickness from 15 nm to 8 nm were studied by AFM technique equipped with a hot-stage in real-time. It was found that melting can erase the spherulitic structure for polymer film with high thickness. However, annealing above the melting point can not completely erase the tree-like structure for the thinner polymer film. Generally, the structure formation of thin polymer films of PCL is controlled not only by melting and crystallization but also by dewetting during thermal annealing procedures, and dewetting predominates in the structure formation of ultra-thin films. However, the presence of tree-like morphology at 75 °C may be due to the strong interaction between PCL and mica surface, which may stick the PCL chains onto the mica surface during thermal annealing process. Moreover, the growth of the dendrites was investigated and it was found that crystallization is followed from a dewetted sample, and the branches did not grow with the stems. The crystallization of polymer in the ultra-thin films is a diffusion-controlled process. Both melting and crystallization behaviors of PCL in thin films are influenced by film thickness.  相似文献   

19.
The isotropy or anisotropy in some physical properties of the ammorphous poly(ethyleneterephthalate) films uniaxially drawn at temperatures above its T_g and then quenched toroom temperature have been studied. Experimental results here presented show that thisamorphous state of high global chain orientation but nearly random segmental orientation,the GOLR state, is nearly isotropic in refractive indices and Young's modulus for smalldeformation, while it is very probably anisotropic in thermal conduction and microwavedielectric properties.  相似文献   

20.
<正> The structures of two complexes C(CuOC6H4CH2NHCH2COO)2 (H2 O)]·H2P(1) and [Co(NH3)6[Co(OC6H4CH2NHCH2COO)2]2[C1]·10H2O (2) were determined by X-ray analyses. Compound (1) crystallizes in the orthorhombic space group P212121 with a=11. 357(1),b= 24. 304(2),c=7.317(4) A,Z= 4;While compound (2) in the monoclinic space group A2/a(C2/c) with a=23. 486(9) ,b=26. 605(6) ,c= 10. 542(1) A,γ= 128. 42(4)°,Z= 4. In compound (1),two Cu(Ⅱ) ions are bonded together by the phenolic oxygen atoms of two tridentate chelating ligands and each of them is separately coordinated by the carboxyl oxygen,amino nitrogen of each chelate ligand and by the fifth oxygen atom as well (from aqua or the carbonyl group in adjacent molecule). Thus the coordination of each Cu(Ⅱ) is a square pyramid with distances of 1. 93- 1. 97A to the four corner atoms and 2. 30 and 2. 32 A to the apex atoms. The whole molecule has an approximately planar configuratioir with the two pyramid apexes pointing towards one side. Compound (2) consists of  相似文献   

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