水溶液中硫酸钾晶体生长动力学

The single crystal growth rates of potassium sulfate in pure aqueous solution under different conditions were determined by photomicrography in a flow system for crystal growth. The effects of themain controlling factors, such as supersaturation, crystal size, solution velocity and crystal growth temperature, on crystal growth rates of potassium sulfate were discussed in detail by using non-linear regression from the experimental data, and several empirical relationships were given. The results showed that the growth rates of crystals increased with supersaturation, crystal size, solution velocity and temperature. Moreover supersaturation was the most important controlling factor influencing growth rates of crystals, crystal size and solution velocity were the secondary and temperature was the least.Furthermore, It was found that the growth rate of crystals along the [100] crystallographic axis was higher than that along the [001] in the same condition. The effect of every factor on crystal growth rates along the [100] crystallographic axis was stronger than that along the [001].     

Influence factors on activity of Ru–Zn catalysts in selective hydrogenation of benzene

Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru–Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru–Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N_2 physisorption, X-ray powder diffraction(XRD), inductively coupled plasma optical emission spectrometer(ICP-OES), scanning electron microscope(SEM), temperature-programmed reduction(H_2-TPR)and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content(22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru–Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.     

Rapid synthesis of CNTs@MIL-101(Cr) using multi-walled carbon nanotubes (MWCNTs) as crystal growth accelerator☆

In this work,hybrid material CNTs@MIL-101(Cr) was synthesized in 2 h using multi-walled carbon nanotubes(MWCNTs) as the crystal growth accelerator with hydrothermal method.The characteristic differences between the crystals of CNTs@MIL-101(Cr) and MIL-101 were investigated by N_2 adsorption–desorption isotherms,X-ray diffraction(XRD),scanning electron microscope(SEM) and thermogravimetric analyzer(TGA).The results showed that MWCNTs embedding in the hybrid material provide more mesoporous volumes than that of MIL-101.Moreover,the fast synthesized crystals of CNTs@MIL-101(Cr) still preserve the octahedral shape like MIL-101 and have a larger size ranging from 1.5 to 2.0 μm which were approximately three times larger than that of MIL-101.In the proposed mechanism,the roles of MWCNTs played in the crystallization were discussed where MWCNTs can be seen as coaxial cylindrical tubes composed of multi-layer graphenes and the place where nucleation and crystal growth processes occur at the tubes' out surface.Then,a crystal seeding layer bonding with the MWCNTs may be easily formed which accelerates the growth rate of MIL-101 crystals.Thus,larger crystals of CNTs@MIL-101(Cr) were formed due to the faster crystal growth rate of MIL-101.     

Multiscale Modelling of Polymer Properties,Volume 22

Single Crystal Growth of Semiconductors from Metallic Solutions covers the four principal growth techniques currently in use for the growth of semiconductor single crystals from metallic solutions. Providing an in-depth review of the state-of-the-art of each, both experimentally and by numerical simulations. The importance of a close interaction between the numerical and experimental aspects of the processes is also emphasized.     

溶剂与杂质对11α-羟基-16α,17α-环氧黄体酮晶习的影响

The effects of solvent and impurity on the crystal habit of 11α-hydroxy-16α, 17α-epoxyprogesterone （HEP） grown from solution were studied by scanning electron microscope. Long prismatic crystals were produced when HEP was crystallized from pure acetone and N,N-dimethylformamide, while blocky crystals were produced from pure chloroform by cooling crystallization. One kind of isomorphic impurity, 16α, 17α-epoxyprogesterone （EP） was selected to examine its effect on the HEP crystal habit. When the content of EP in the mother liquor is very high （55.45%, solvent free basis）, the habit of produced HEP crystals was greatly modified from prismatic to octahedral. The differential scanning calorimetry and X-ray powder diffraction analyses showed that the change of crystal habit was originated from the crystal structure modification.     

A Population Morphologically Structured Model for MicroscopicGrowth of Filamentous Microorganism

The growth of filamentous microorganism is contributed by tip extenasion and branching, The microecoplc growth of filamentous mlcroorgemiam means the growth process from one or a few spores. In ordeT to descrihe the microecopic procees, a population morphological]y staagtured model is proposed, in which three morphological compartment and their interactions were ccamidemd, and the heterogeneity of hyphal growth was included. The model was a4ppfied to describe the microscopic growth of Stzeptomyces tendae mad Geotrichum caudidtun with good agreement. From model prediction, it is concluded that if the number of hyphae is large enough (macropscpic growth), the specific growth rate of filamentous microorganism and the ratio of morphologicad forms in hyphse will become constant.     

用扫描隧道显微镜研究铜表面苯并三氮唑吸附膜的结构形态

It is observed by scanning tunneling microscopy (STM) that the adsorbed Benzotriazole (BTA) on copper is long in shape and has an irregular rectangle.The growth of BTA on copper is in the from of polymeric chain and mainly in one dimension rather than two dimensions.The copper surface covered by BTA becomes flatter,smoother and the roughness was smaller than that of bare copper,so the corrosion is largely decreased.However,many grooves can be seen between BTA polymeric chains in which corrosion may exist to a degrees.     

MSMPR反应结晶器中地塞米松磷酸钠晶体生长模型的研究

The reactive crystallization process of dexamethasone sodium phosphate was investigated in a continuous mixed-suspension, mixed-product-removal(MSMPR) crystallizer. Analyzing experimental data, it was found that the growth of product crystal was size-dependent. The Bransom, CR, ASL, M J2 and M J3 size-dependent growth models were discussed in details. Using experimental steady state population density data of dexamethasone sodium phosphate, parameters of five size-dependent growth models were determined by the method of non-linear least-squares. By comparison of experimental population density and linear growth rate data with those obtained from the five size-dependent growth models, it was found that the MJ3 model predicts the growth more accurately than do the other four models. Based on the theory of population balance, the crystal nucleation and growth rate equations of dexamethasone sodium phosphate were determined by non-linear regression method. The effects of different operation parameters such as supersaturation, magma density and temperature on the quality of product crystal were also discussed, and the optimal operation conditions were derived.     

6.0mol•L－1KOH溶液中锌单晶（002）和（100）晶面的电化学行为

In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.     

苯为前驱体的稠环芳烃的自由基反应机理的量子化学研究

The free-radical growth mechanisms for the formation of polycyclic arenes (PCAs) were constructed based on the block unit of benzene, and were calculated by the quantum chemistry PM3 method. Two kinds of reaction paths are proposed and discussed. The calculation results show that the formation of PCAs is only controlled by the elimination of H atom from benzene, and the corresponding activation energy is 307.60 kJ•mol－1. H2 is only the ef-fluent gas in our proposed reaction mechanism, and the calculation results are in accord with the experimental facts.     

IN SITU SEPARATION OF ETHANOL DURING BATCH FERMENTATION WITH CO_2 STRIPPING AND ACTIVATED CARBON ADSORPTION

In situ separation of ethanol during batch fermentation with CO_2 stripping and activated carbon adsorption was studied. The higher initial glucose concentration and fermentation rate were reached due to the elimination of ethanol inhibition on the cell growth by means of CO_2 stripping. The stripped ethanol vapor was selectively adsorbed by an activated carbon column. The conde(?)sate desorbed from the adsorption column can be higher than 50% by weight. Ar unstructured model was used to simulate the experimental data satisfactorily.     

Preparation and Properties of Sintered Corundum at Low Temperatures with Nano-η-Al_2O_3 Powder

In order to reduce the sintering temperature and improve the properties of sintered corundum, corundum specimens were prepared by granulation and sintering with nano-η-Al_2O_3 as the raw material and polyvinyl alcohol as the binder. The effects of different sintering temperatures(1 550, 1 600, 1 650 and 1 700 ℃) and holding time(2, 4 and 6 h) on the properties and microstructures of the specimens were studied, and the transformation mechanism of η-Al_2O_3 was analyzed. The results show that dense sintered corundum with bulk density of 3.74 g/cm~3 and apparent porosity of 1.77% is obtained by calcinating at 1 650 ℃ for 6 h; the phase transition from η-Al_2O_3 to α-Al_2O_3 occurs first on the surface of alumina particles and then diffuses rapidly to the interior; at lower sintering temperatures there is no abnormal growth of crystals, the bonding between the grains is tight, transgranular fracture is the main fracture mode, there are fewer intergranular pores, and the grain size is in the range of 3.5-7.5 μm.     

Effect of Y_2O_3 Addition on Sintering Properties and Microstructure of Spinel Materials

The effect of Y_2O_3 addition on the sintering properties and microstructure of spinel was investigated using alumina-rich spinel as the raw material. The phase constitution and microstructure of the specimens were characterized by XRD and SEM,and the pore structure of the specimens was measured by a mercury porosimeter. The results indicate that a viscous melt forms wrapping around spinel crystals by adding a little Y_2O_3 powders(1 mass%),yttrium alumina garnet will crystallize around spinel crystals by adding more Y_2O_3 powders( ≥3 mass%); the sintering properties of the spinel are significantly improved by adding Y_2O_3 powders less than 3 mass%,while they will be relatively weakened by adding Y_2O_3 powders more than 3 mass%.     

液-液同向流中冰浆的形成

A new technique for ice slurry production was explored. Multiple small water-drops were formed in another immiscible chilled liquid by a single-nozzled atomizer and frozen in the fluidized bed by direct contact heat transfer. Experiments were conducted to investigate the dynamic behaviors of the ice crystal making system. The results demonstrate that the ice crystals could be produced continuously and stably in the vertical bed with the circulating coolant of initial temperature below -5℃. The size distribution of the ice crystals appears non-uniform, but is more similar and more uniform at lower oil flow rate. The mean ice crystal size rests seriously with the jet velocity and the oil flow rate. It decreases with decreasing the oil flow rate, and reaches the maximum at an intermediate jet velocity at about 16.5 m.s y. The ice crystal size is also closely related to the phenomenon of drop-coalescing, which can be alleviated considerably by reducing the flow rate or lowering the temperature of the carrier oil. However, optimization of liquid-liquid atomization is a more effective approach to produce fine ice crystals of desired size.     

酸性废水体系中硫酸钙反应结晶过程研究(英文)

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.     

釜外和釜内螺旋半圆管夹套内流体流动与换热性特性

The physical models of the outer and inner half coil jackets were simplified to two types of coiled ducts.The mathematic models of incompressible fluid at the condition of laminar flow and heat transfer in the two types of jackets for cooling process reactor were set up and solved by the semi-implicit method for pressure linked equa-tions consistent (SIMPLEC) algorithm based on a control volume method.The flow and temperature fields were given and the effects of Dean and Prandtl numbers on flow and heat transfer were studied.The results show that flow in the inner half coil jacket is found to exhibit transition of secondary flow pattern from two vortices to four vortices when the Dean number increases,but that in the outer half coil jacket is not found.The critical Dean num-ber is about 96.The inner half coil jacket has stronger heat transfer ability than the outer half coil jacket and this superiority is more evident with larger Prandtl number.However,as the Dean number is greater than 105,the flow resistance enhances more severely in the inner jacket than the outer jacket.For both jackets,the centers of the heated wall are the poorest for heat transfer.     

不同萃取技术获得的Artemisia sp的甲醇提取物其抗氧化和抗菌活性的比较

The polyphenol content,antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species(Artemisia vulgaris and Artemisia campestris)were compared.Ultrasound positively affected the yield of extractive substance and the kinetics of extraction,but the extract obtained by the classical extraction showed the highest antioxidant activities and contained higher total contents of phenolic compounds and flavonoids than the extracts obtained by two other extraction techniques.Both flavonoid aglycones(apigenin,quercetin,quercetin 3,3′-dimethyl ether)and flavonoid glycosides(rutin,hyperoside and kaempferol 3-rhamnoside)were identified by thin layer chromatograph(TLC)analysis in the extracts from both species.A.campestris extracts were richer in quercetin than A.vulgaris and its antimicrobial activity was also better than A.vulgaris.Extracts obtained from both species were found to be more effective on the tested yeasts than bacteria.The kinetics of the total extractive substances,such as phenolic,flavonoids and quercetin extraction,was successfully described by the model of unsteady-state diffusion.     

毛竹的主要化学成分分析及热解

In recent years, great attention has been paid to the exploitation and use of biomass energy.Using bamboo as the raw material to produce energy and other chemicals is significantly important. A primary study was made on the pubescens, one kind of bamboo distributed broadly in China with fast growth rate. The contents of cellulose, hemi-cellulose, and lignin in different parts of pubescens with different growth ages, as major components of the cell wall, were determined. The analysis procedures were as follows, firstly the substances other than the above mentioned three were removed chemically,then the hydrolyzed cellulose liquid was oxidized with excess oxidants, and at last titrated. Pubescens powder was packed into the quartz tube reactor, then was heated from room temperature to 300, 350,400, 450, 500, 550℃ and 600℃ respectively in flowing N2. Pyrolysis was held at the final temperature for 10 h. The liquid products were analyzed with GC/MS. The main products in the liquid obtained were.acetic acid, 2,6-dimethoxy phenol, 2,3-dihydrobenzofuran, etc. The pyrolysis temperature exerted great effect on the composition of the liquid products. The distribution of the products could be regulated by controlling pyrolysis temperature.     

Preparation,Performance and Slag Resistant Mechanism of Low Thermal Conductivity Microporous Corundum

The microporous corundum material was prepared using alumina micro-powder as the main raw material,alumina sol and starch as binders by a wet process,achieving the bulk density of 3. 05 g·cm~(-3),the apparent porosity of 9. 1%,the closed porosity of 12. 3%,the median pore diameter of 0. 43 μm,and the thermal conductivity of 6. 5 W·m~(-1)·K~(-1)at 800 ℃ which is41. 6% lower than that of common corundum. The slag resistance of the microporous corundum material was studied by immersion and compared with that of the common corundum aggregate, and the slag resistant mechanism of microporous corundum material was revealed. The results show that the slag resistance of the microporous corundum material is superior to that of the common corundum aggregate,the SEM and EDX show that on the reaction interface between microporous corundum and molten slag,a continuous isolation layer with a large quantity of CA_2 and CA_6columnar crystals is formed; while the common corundum aggregate reacts with the molten slag interface to form a discontinuous isolation layer of columnar crystals,through which a lot of molten slag corrodes or permeates into the aggregate. The mechanism is mainly that the microporous structure is more advantageous to nucleation and growth of CA_2 and CA_6 columnar crystals; in the reaction with the aggregate,the molten slag gets saturated and the critical solution thickness of the microporous corundum and the common corundum is 0. 16 μm and 0. 34 μm,respectively,this is caused by the smaller microporous corundum aggregate pores; and the smaller pores also increase the second phase ripening rate of microporous corundum,which is 9. 7 times of that of the common corundum.     

Control of Microstructural Development in Reaction—Bonded Silicon Nitride（RBSN） by Seeding With β—Si3N4 Single Crystals

The addition of β－Si3N4 seed grains to a ceramic powder is an effective means of controlling the microstructural evolution,In this work addition of β－Si3N4 seed grains gave rise to a bi-modal microstructure made up of large rod-lkike grains that grew from the added seed during the liquid phase sintering process and the usua elongated grains which are developed from the α→β transformation process in silicon nitride,The morphology of te grains that were grown epitaxially from the seed was influenced by the size and shape of the seed crystals;the relatively large and elongated seed grains gave rise to large rod-like grains whilst those with equiaxed-like shape gave rise to large grains similar in shape to the seed from which they were grown.The evolution of the large rod-like grains and the resultant bi-modal microstructure led to a considerable improvement in the mechanical properties.