冷冻-复温过程中葡萄细胞结晶变化研究

利用低温显微镜系统对葡萄进行了冷冻-复温实验,研究了葡萄细胞在冷冻-复温过程的结晶变化。通过分析冷冻-复温过程的葡萄细胞显微图像、细胞体积、内压、渗透率的变化,发现：葡萄细胞的结冰温度随冷冻速率的增加而降低;葡萄细胞的体积变化总趋势是随温度的降低而减小,但由于细胞内自由水体积的变化,在-5~0℃细胞体积会有所增大。在14℃/min、50℃/min冷冻速率下细胞体积分别减小了54.5%,26.3%。冷冻速率越大,细胞体积变化越小;冷冻过程中葡萄细胞的渗透系数随温度的降低而降低,随冷冻速率的降低而降低。在葡萄细胞的冷冻-复温过程中,提高复温温度能有效减少细胞的破损。

不同植冰温度下冷冻液的结晶变化及其对小鼠胚胎冷冻的效果

采用程序化冷冻方法 ,对不同植冰温度下几种冷冻液的结晶变化进行了分析 ,并比较了其对小鼠胚胎的冷冻效果。结果表明 ,- 5 .0℃植冰时 ,3种冷冻液 PEF、PGF和 PEGF只有部分结晶 ;当植冰温度为 - 5 .5℃时 ,PEF和 PEGF完全结晶时间为 1 0 min,PGF在 1 5 m in尚未完全结晶 ;- 6 .0℃植冰时 ,3种冷冻液完全结晶时间分别为 8,1 0和 1 0 min;- 6 .5℃植冰后完全结晶时间分别为 5 ,8和 5 min。将小鼠胚胎载入上述 3种冷冻液 ,- 5 .5℃植冰冷冻解冻后 ,囊胚孵化发育率分别为 81 .7% ,6 8.5 %和 87.5 % ,- 6 .0℃植冰时发育率分别为 80 % ,76 .5 %和 90 .9% ,- 6 .5℃植冰后的发育率分别为 1 0 % ,1 3.3%和 38.4 %。据此得出 ,在 - 5 .5或 - 6 .0℃时植冰 ,以

Modeling of strain hardening and dynamic recrystallization of ZK60 magnesium alloy during hot deformation

The flow stress behavior of ZK60 alloy at elevated temperature was investigated. The strain hardening and dynamic recrystallization of the alloy were modeled by Kocks-Meching model and Avrami equation, respectively. A new constitutive equation during hot deformation was constructed to predict the flow stress considering the dynamic recrystallization. The results show that the flow stress curves predicted by the proposed equation have high correlation coefficients with the experimental data, which confirms that the developed model is accurate and effective to establish the flow stress equation of ZK60 magnesium alloy during hot deformation. Microstructure observation shows that dynamic recovery occurs in the initial stage of hot deformation. However, the microstructure turns to recrvstallization structure as the strain increases.

Microstructure evolution and mechanical properties of ZK60 magnesium alloy produced by SSTT and RAP route in semi-solid state

The microstructure evolution and mechanical properties of a ZK60 magnesium alloy produced by the semi-solid thermal transformation （SSTT） route and the recrystallization and partial melting （RAP） route were studied, respectively. The microstructure evolution during partial remelting was studied at different temperatures for different time. The tensile mechanical properties of thixoformed components by the two routes at room temperature were examined. The results show that coalescence is dominant in the SSTT alloy and Ostwald ripening is dominant in the RAP alloy. Compared with the SSTT route, the RAP route can produce finer semi-solid microstructure under the similar isothermal holding condition. The microstructure of the RAP alloy is much more spheroidized compared with the SSTT alloy. Thixoforming for the ZK60 magnesium alloy produced by the SSTT and RAP route results in successful filling of the die, and the thixoforming process improves the mechanical properties of ZK60 magnesium alloy. The RAP alloy shows significantly advantageous mechanical properties over that of the SSTT alloy.

Effect of nano TiN/Ti refiner on as-cast and hot-working microstructure of commercial purity aluminum

A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was investigated. The results show that TiN/Ti refiner exhibits excellent grain refining performances on pure Al. With an addition of 0.2% TiN/Ti refiner, the average grain size of pure Al decreases to 82 μm, which is smaller than that of pure Ti and Al 5Ti 1B master alloy as refiners. The microstructure of weld joint of pure Al with 0.1% TiN/Ti refiner is fine equiaxed grains and the hardness of weld joint is higher than that of the base metal. For pure Al with 40% cold deformation and recrystallization at 250 °C for 1.0 h, the grains of the sample added 0.1% Ti powder have an obvious grain growth behavior. In contrast, oriented grains caused by deformation have been eliminated, and there is no obvious grain growth in pure Al refined with 0.1% TiN/Ti refiner, indicating that nano TiN in the refiner inhibits the growth of grain during recrystallization.

铝酸盐水泥后期强度改进研究

常见的铝酸盐水泥是拥有凝结硬化好、早期强度好、水化热高、防火、抗氧化等良好特性的建筑材料。但是,由于铝酸盐混凝土的水化过程在水化后期很容易出现结晶变化,从而造成了混凝土整体的质量倒缩,从而降低了铝酸盐砂浆混凝土构件的后期强度与施工质量。铝酸盐水泥后期的质量收缩问题,严重影响了其实际施工使用。因此,综合研究铝酸盐水泥后期强度倒缩的一些问题,并找出了解决铝酸盐水泥后期强度倒缩的解决办法。

稀盐酸水解棉纤维反应过程的综合研究

对稀酸催化水解棉纤维工艺进行了综合实验研究,用扫描电子显微镜观察了棉纤维形态的变化,采用X射线衍射仪测定了棉纤维结晶结构的变化.研究结果表明:盐酸质量分数的增加、反应温度的提高、反应时间的延长,对常压条件下棉纤维稀酸水解反应均有促进作用;固-液比的变化对水解反应的影响是综合的;水解反应伴随着棉纤维宏观形态和结晶度变化进行.研究获得了最佳反应工艺参数:盐酸质量分数9.5%、反应温度95℃、固-液比4∶100.

Hot deformation and processing map of GH3535 superalloy

The hot deformation behavior of GH3535 superalloy was investigated by hot compression tests in the temperature range of 1000-1200 °C and strain rate range of 0.01-50 s-1. The activation energy is about 356.3 k J/mol, and the flow curves and processing map were developed on the basis of experimental data. The processing map exhibits a stable domain which occurs in the strain rate range of 0.01-1 s-1 at all the temperatures and a instable domain which occurs in the strain rate range of 1-50 s-1. Microstructural observations reveal that the full dynamic recrystallization（DRX） occurs in the conditions of（1150 °C, 0.01 s-1）,（1200 °C, 0.01 s-1） and（1200 °C, 0.1 s-1） with different grain sizes and undissolved carbides. The flow localization and cracks occur in the regime of flow instability.

Investigation on hot deformation behavior of AZ31 magnesium alloy

The hot compressive deformation of extruded AZ31magnesium alloy with the mass fractions of Al and Zn equal to 3 % and 1 % respectively is studied by a Gleeble-1500D thermal mechanical simulator over the temperature range from 200 ℃ to 400 ℃ and the strain rate from 10-3 s-1 to 100 s-1. The true stress-strain curves of the strain of 65 % are tested. The deformation activation energy is obtained and the flow stress model is established by analyzing the effects of strain rate and temperature on the flow stress. Zener-Hollomon parameter is introduced to describe the softening behaviors of AZ31 magnesium alloy resulted from dynamic recrystallization during the hot compressive deformation, whose natural logarithm is linear with the critical strain of dynamic recrystallization.

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.

Hot deformation behavior of AZ91 magnesium alloy in temperature ranging from 350℃ to 425℃

The flow behavior and microstructure evolution of AZ91 magnesium alloy during a thermomechanical process, hot compression test, was investigated. The specimens were hot compressed at a temperature ranging from 350 ℃ to 425 ℃ and at strain rate of 0.1 s-1 to the strains of 0.3, 0.5 and peak. Microstructural evolutions were studied using optical and scanning electron microscopes. The results show that during the compression process, the recrystallized grains nucleate along the pre-existing grain boundaries. The amount of dynamically recrystallized grains is increased with strain in a sigmoid scheme followed by Avrami equation. The size of dynamically recrystallized grains also increases at the beginning and decreases after reaching the maximum value.

Transformation of microstructure and phase of disodium guanosine 5′-monophosphate: Thermodynamic perspectives

Microstructure and phase transformation of disodium guanosine 5′-monophosphate(5′-GMPNa_2) are extremely important for controlling the process and understanding the mechanism of crystallization. In this work, the thermodynamic properties of polymorphous 5′-GMPNa_2 especially the solubility were studied, the solubility results show that 5′-GMPNa_2 is more soluble in ethanol–water(E–W) than in isopropanol–water(I–W). The amorphous form of 5′-GMPNa_2 is more soluble than the crystalline form at the same mole fraction and temperature. Meanwhile, the crystalline forms and morphologies of the residual solids were characterized by PXRD and SEM. The results indicate that solid forms of 5′-GMPNa_2 transformed spontaneously from amorphous to crystalline when the ethanol proportion is ≥20%. In addition, increasing the pH facilitates the dissolution of 5′-GMPNa_2 and helps to maintain the crystalline form. The associated Gibbs free energy values were calculated to verify the trend of transformation from amorphous to crystalline 5′-GMPNa_2. These results should help to guide the industrial crystallization process and to obtain the crystalline form of 5′-GMPNa_2.

Formation of crystalline particles from phase change emulsion： Influence of different parameters

Solidification or crystallization of phase change emulsion in the form of fine emulsion drops in a direct contact coolant at temperatures below their freezing point was studied. This work is mainly focused on the size and shape of the generated partides from phase change emulsified fats. Size of the particles is the major or key factor being considered during their formation, however, other factors that govern the particle size and shape were also observed. The operating parameters of the process were optimized in order to obtain particles of smaller size ranges in the window of current operating conditions. The crystallization of complex emulsion maffices is very difficult to control in the bulk at desired requirement. Hence, the emulsion drop to particle formation has advan- tage in comparison with the bulk solidification or crystallization. The main objective of this work is to achieve spherical emulsion particles in a direct contact cooling system. Parameters like： stat）ility, characterization, viscos- ity, and the effect of different energy inputs were examined. Moreover, the effects of the capillary size, interracial tension, temperature of the emulsion on the particle size were also monitrored.

Fabrication and Properties of Microencapsulated n-octadecane and Paraffin

Microencapsulated n-alkanes as energy- storage materials have promising application prospects. The ndcrocapsules containing 100 - 50 wt% of n - octadecane, 0 -20 wt% of paraffin and 0 - 30 wt% of cyclohexane were synthesized by in-situ polymerization using melamine- formaldehyde polymer as shell. Cyclohexane was removed after heat-treated the microcapsules at 100℃. The morphologies, cell parameters, phase change properties, thermal stable temperatures of these microcapsules were examined. The diameters of these microcapsules are lower than 5 μm. The effect of paraffin in the microcapsules on the cell parameters of n-octadecane is negligible. The paraff＇m is effectively used as a nucleating agent to decrease the degree of supercooling. The melting enthalpy is decreased from 132 J/g to 111 J/g due to the increase of the cyclohexane contents. The thermal stable temperature is enhanced 6 - 16℃ after heat-treated the microcapsules at 160℃ for 30 min.

Estimation of main rheological parameters for Pangxidong-Jinkeng structural fracture zone and Qinzhou-Hangzhou metallogenetic belt in South China

The mylonites occurred in the fracture zones are studied by dynamically recrystallized quartz grains.The natural microstructures in mylonites are simulated and the deformation conditions of mylonitization are estimated by fractal analysis,recrystallized grain size paleopiezometer and flow laws of quartzite.Depending on fractal analysis,the deformation temperature of mylonitization is approximately 600℃,which presents high greenschist facies to low amphibolite facies.The mylonitization occurred at differential stresses of 9.1--10.7MPa(lower limits).Compared with extrapolation of quartzite flow laws and estimates of fractal analysis,the strain rate of mylonitization is under 10-13.8/s.

Novel Thermally-Accessible Structural Changes of Chiral and Some Related Cu（ll） Complexes

A mononuclear chiral copper（ll） complex, [Cu（RRchxn）2（C（CN）3）2]＇H20 （RRchxn = （1R, 2R）-diaminocyclohexane） （RRchxnH）, and its deuterated compound, [Cu（RRchxn）2（C（CN）3）z].D20 （RRchxnD）, and their isomers, [Cu（trchxn）2（C（CN）3）2]＇H20 （trchxn = trans-l,2-diaminocyclohexane） （trchxnH） and [Cu（trchxn）2（C（CN）3）2]＇D20 （trchxnD） have been prepared and characterized by means of 1R （infrared）, electronic, and CD （circular dichroism） spectra, magnetic susceptibility, and variable-temperature X-ray crystallography as single crystals or powder. Interestingly, depending on grain size of samples, RRchxnH exhibits the monoclinic form and the orthorhombic form, which are distinguished by systematic absence and powder XRD （X-ray diffraction） patterns clearly. Although single crystals did not exhibit phase transition, powder XRD patterns of RRchxnH and weakly hydrogen bonded RRchxnD emerged low-temperature phase of monoclinic in the orthorhombic patterns only around 200-220 K. However, as a control, powder XRD patterns of both trchxnH and trchxnD did not exhibit such phase transition clearly.

The Preparation of Ultra-fine Calcium Carbonate and Its properties Study

This article adopts the double decomposition method, select the appropriate experimental conditions and operation process, respectively add appropriate amount of sodium carboxymethyl cellulose （CMC） as crystal control agent to study the influence of crystalline of ultrafine calcium carbonate. The experimental results show that the different concentrations of CMC as crystal control agent on the morphology and crystal structure of calcium carbonate have obvious effect, which emerge morphology change from square to spherical, crystalline transition from calcite to aragonite. Thus, the results provide experimental data and theoretical basis for the use of different additives, and provide experimental basis and feasible solution for this kind of reaction.

New insight into solvent engineering technology from evolution of intermediates via one-step spin-coating approach

The anti-polar solvent technique is an effec- tive way to improve the film quality in a perovskite solar cell. In this work, we reveal the reason why chloroben- zene （CBZ） plays an important role in controlling the crystallization process. By investigating the formation of intermediate phases in the precursor solution, we observed that the CH3NH3I （MAI）-PbI2-dimethylformamide （DMF） or MAI-PbI2-dimethylsulphoxide （DMSO） adducts have not yet formed until washed with non-polar solvent. The accelerated formation of intermediate phase yields high crystalline perovskite layers. Rapid solvent evaporation and retarded perovskite crystallization in one-step method are efficient to obtain high-quality perovskite films. Conse- quently, MAI-PbI2-DMSO intermediate shows neat rod-like structure with high crystallinity, which eventually transforms extremely dense and uniform perovskite films.

Approaching strain limit of two-dimensional MoS_(2) via chalcogenide substitution

Strain engineering is a promising method for tuning the electronic properties of two-dimensional(2 D)materials,which are capable of sustaining enormous strain thanks to their atomic thinness.However,applying a large and homogeneous strain on these 2D materials,including the typical semiconductor MoS_(2),remains cumbersome.Here we report a facile strategy for the fabrication of highly strained MoS_(2) via chalcogenide substitution reaction(CSR)of MoTe_(2) with lattice inheritance.The MoS_(2)resulting from the sulfurized MoTe_(2) sustains ultra large in-plane strain(approaching its strength limit~10%)with great homogeneity.Furthermore,the strain can be deterministically and continuously tuned to~1.5%by simply varying the processing temperature.Thanks to the fine control of our CSR process,we demonstrate a heterostructure of strained MoS_(2)/MoTe_(2)with abrupt interface.Finally,we verify that such a large strain potentially allows the modulation of MoS_(2) bandgap over an ultra-broad range(~1 e V).Our controllable CSR strategy paves the way for the fabrication of highly strained 2D materials for applications in devices.

Structural and thermal sensitivity of Cu-Zr-Ti amorphous alloys to tension

Structural and thermal sensitivity of Cu(60-x)Zr(30+x) Ti 10 (x=0,5,and 10 at%) amorphous alloys to the application of tension was investigated. The structural sensitivity to tension decreases with increasing Cu content. The crystallization enthalpy increases with increasing excess free volume. The characteristic temperatures of the tensile samples can surpass those of the as-cast ones under a critical heating rate which differs in the Cu content. The increase of the excess free volume significantly influences the glass transition and crystallization procedures.