Experimental Study on Stability and Improving Sweep Efficiency with Microfoam in Heterogeneous Porous Media

In this paper, we attempted to prepare microfoam by using a sandpack filled with glass beads with co-flowing gas and foaming solution, the microfoam stability and effectiveness in improving profile control capacity at micromodel and pore media were evaluated by micromodel tests and double-core experiments. The results of micromodel tests showed that microfoam stability was increased with increasing xanthan gum concentration due to a higher solution viscosity and viscoelasticity of liquid film. The xanthan gum-stabilized microfoam had a longer propagation distance through the low permeable region of heterogeneous micromodel at time of breakthrough than common microfoam, the optimum performance of microfoam for fluid diversion was multiple bubble trapping and mobilization rather than lamella division. According to the results of double-core experiments, the microfoam could plug the high permeability sandpack and improve the sweep efficiency in the low permeability sandpack, which could improve the water injection profile of porous media effectively. The increase in profile control effects had a good correspondence with the increase of xanthan gum concentration. The presented results were useful in understanding and designing microfoam injection in reservoirs for enhanced oil recovery.     

Effect of Cryostructuring Treatment on Some Properties of Xanthan and Karaya Cryogels for Food Applications

Cryogels are novel materials because the manufacturing process known as cryostructuring allows biopolymers to change their properties as a result of repeated controlled freeze–thaw cycles. Hydrogels of xanthan and karaya gums were evaluated after undergoing up to four controlled freeze–thaw cycles in indirect contact with liquid nitrogen (up to −150 °C) to form cryogels. Changes in structural, molecular, rheological, and thermal properties were evaluated and compared to those of their respective hydrogels. Samples were also analyzed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), Rotational Rheology (RR), Modulated Differential Scanning Calorimetry (MDSC) and zeta potential (ζ). In general, significant differences (p < 0.05) between the numbers of freeze–thaw cycles were found. Karaya cryogels were not stable to repeated cycles of cryostructuring such as the three-cycle xanthan cryogel, which has the best structural order (95.55%), molecular interactions, and thermal stability, which allows the generation of a novel material with improved thermal and structural properties that can be used as an alternative in food preservation.     

体系pH值、乳化温度和电解质离子对异丙甲草胺水乳剂稳定性的影响

通过测定药物液滴的平均粒径和Zeta电位研究了体系pH值、 乳化温度和电解质离子对乳化剂三苯乙烯基苯酚聚氧乙烯醚磷酸酯三乙醇胺盐(SCP)稳定的异丙甲草胺水乳剂稳定性的影响. 结果发现, 体系的pH值影响SCP分子在水中的电离能力, 当pH=9时, SCP完全电离, 能为液滴提供较大的静电稳定作用, 水乳剂稳定性最好; 乳化温度低时, SCP分子向液滴界面扩散慢, 且舒展不完全, 液滴所带负电荷较少, 水乳剂稳定性差; 温度升高后, 水相黏度减小, 布朗运动加剧, 液滴碰撞合并几率增大, 且SCP分子热运动增强, 易从界面逃逸, 液滴间静电斥力减弱, 同时SCP亲水性下降, 水乳剂稳定性变差; 电解质离子会压缩界面双电层, 降低Zeta电位, 液滴带电量减少而聚结, 离子浓度越大, 电荷数越大, 水乳剂稳定性越差. 在相同的离子浓度下, 水合半径小的Ca²⁺压缩双电层能力强于Mg²⁺, 添加Ca²⁺后水乳剂稳定性更差.     

Double Emulsions Stabilized by Xanthan in the Absence of Hydrophilic Surfactant

The preparation of double water-in-oil-in-water (W/O/W) emulsions containing xanthan gum (XG) in the absence of hydrophilic surfactant was investigated. The emulsions were prepared by the two-step emulsification process. The stability of these systems was evaluated through the evaluation of physicochemical and rheological properties. Microscopic observations in combination with particle size analysis were also performed. The obtained results show that it is possible to prepare stable double emulsions with a single polysaccharide by using the indirect process. The stability depends on the viscosity of the continuous phase and hence the concentration of XG. The apparent viscosity of the emulsions increased with the increase of XG concentration. Particle size analysis shows that the droplet sizes are directly related to XG concentration.     

Effect of Xanthan Gum on the Performance of Aqueous Film-Forming Foam

Solution properties of aqueous film-forming foam (AFFF) formulations containing different xanthan gum contents were investigated first by varying the mass fraction of xanthan gum in the range of 0.1–0.5%. Foam properties and fire-extinguishing performance of the AFFF formulations were then evaluated. Results indicated that xanthan gum content slightly affected surface tension of foam solutions. However, xanthan gum significantly affected viscosity of AFFF concentrates. Foaming of the AFFF formulations was hardly affected by xanthan gum, but foam stability of the compounds was obviously enhanced with the addition of xanthan gum. Optimal xanthan gum content was determined as 0.3%, which resulted in the shortest 90% control time and fire extinguishment time. Burnback time of foams increased with the addition of xanthan gum because of the enhanced foam stability.     

Bubble point measurements on large areas of microporous membranes

The classical bubble point measurement can only be applied to membrane areas limited in size. In the case of areas larger than approx. 0.05 m² the diffusion flow exceeds the convective flow through individual pores. This difficulty can be avoided by using a microphone as a flow sensor which responds only to convective flows. Filter cartridges with membrane areas of 1 m² were tested by this method, and the maximum pore sizes compared with the retention capacity with respect to Pseudomonas diminuta. The maximum pore diameters correlate with bacterial retention within a tolerance of ± 0.3 μm.     

聚合物分散剂对氟虫脲水悬浮剂分散稳定性的影响

通过测定药物颗粒界面Zeta电位和平均粒径, 研究了聚合物分散剂苯乙烯磺酸聚合物钠盐(GY-D08)用量、pH和盐离子对氟虫脲水悬浮剂分散稳定性的影响, 研究结果表明, 分散剂GY-D08的加入量与水悬浮剂分散效果密切相关, 制备质量分数为5%氟虫脲水悬浮剂的GY-D08最佳用量为2%, GY-D08用量过多或过少都会使分散效果下降; pH影响分散剂GY-D08在水中的电离能力, 当pH=9时, GY-D08分子完全电离, 能为颗粒提供较大的静电位阻, 水悬浮剂分散稳定性最好; Mg²⁺或Ca²⁺压缩颗粒界面的双电层, 降低Zeta电位, 使颗粒因带电量减少而聚结, 导致水悬浮剂分散稳定性变差, 且Mg²⁺或Ca²⁺浓度愈大, 其分散稳定性愈差; 当离子浓度相同时, Ca²⁺压缩双电层的能力比Mg²⁺强, 添加Ca²⁺后的水悬浮剂的分散稳定性更差.     

Effect of Variant Counterions on Stability and Particle Size of Silica Sol

The effects of variant counterions with ionic strength of 0.05, 0.10, 0.20 and 0.25 mol·kg^-1 on the stability and particle size of silica sols have been studied using the traditional methods of Ubbelohde viscosity measurement, TEM and titration respectively, finding that the stability and particle size of the silica sols are all concerned with the acidic, positively electric properties and the sizes of the counterions, as well as the attraction between the counterions and surface silicon hydroxyl groups of the silica sols. The small positively charged counterions lead to the decrease in particle sizes, making the silica sol the most stable. But the larger weakly acidic counterions can restrict the particle sizes of the silica sols and easily make the sols coagulate. It was also found that there existed a linear relationship between log r and log η, which has not ever been reported. The effect of temperature on the stability and particle sizes was also discussed.     

黄原胶和瓜尔胶混合溶液及其硼砂交联体系的流变性能

本文研究了黄原胶(XG)和瓜尔胶(GG)的混合溶液及其硼砂(B)交联体系的流变性,考察了XG/GG间的“协同增效作用”以及溶液组成、pH和电解质(NaCl和CaCl 2)对其流变性的影响。结果表明,所有溶液体系均为假塑型流体,其流变曲线可用Herschel-Bulkley和Casson模型描述。XG和GG复配具有明显的“协同增粘效应”,在XG占两聚合物的质量分数w(XG)为20%和90%时协同增粘效应最强,其“协同增粘率”(R m)分别约为42%和34%。硼砂(B)可交联XG/GG混合溶液,其交联增粘效果随w(XG)的减小和硼砂质量浓度ρ(B)的增大而增大;在w(XG)=50%和ρ(B)=1.00 g/L时,“交联增粘率”可达85%。在所研究的pH值范围(6.2~10.0)内,XG/GG混合溶液的流变性基本无变化,而XG/GG/B交联体系(w(XG)=50%和ρ(B)=0.75~1.00 g/L)的表观粘度随pH值增大先升高后降低,pH=9.0时出现最大值,交联增粘率达107%。电解质可使XG/GG/B交联溶液(w(XG)=10%和ρ(B)=0.50 g/L)体系的粘度大幅下降,且CaCl 2的影响明显高于NaCl,表明交联结构的耐盐能力较差。这些结果加深了对XG/GG混合溶液流变性的认识,可为其实际应用(如在强化采油中的应用)提供依据。     

三偏磷酸钠交联黄原胶的制备及其溶液流变性

以三偏磷酸钠(STMP)为交联剂,合成了水溶性低交联度黄原胶(XG),依据其溶液粘度优化出了最佳合成条件;考察了电解质质量分数、pH值及温度对STMP交联黄原胶(简记为SP-c-XG)溶液流变性的影响,并与XG溶液进行了对比。 结果表明,在所研究的电解质(NaCl和CaCl₂)质量分数(0~5.0%)、pH值(2~11)和温度(20~70 ℃)范围内,SP-c-XG和XG溶液的流变曲线均为假塑型,符合Herschel-Bulkley模型;其屈服值、表观粘度和动力学模量随电解质质量分数增大均先下降后上升,而随pH值的升高先升高后降低,随温度升高而降低。 SP-c-XG和XG溶液具有相似的流变性,但与XG溶液相比,SP-c-XG溶液具有更高的屈服值和表观粘度,特别是具有更强的弹性和耐温性,在油田强化采油领域具有重要应用前景。     

A comparison of rheokinetics on static and shear crosslinking processes of xanthan gum

The crosslinking process of xanthan gum was studied under static and shear conditions. Conventional rotational rheometer was adopted to study the shear crosslinking process, and the static crosslinking process was monitored using an optical microrheometer without physical contact between the instrument and the sample. Both experiment and numerical simulation were adopted to compare the two gelation processes at different temperatures. The results showed that the effects of temperature on static and shear crosslinking processes of xanthan gum have the same trend and the rheological curves of the two gelation processes are similar in shape. The same rheokinetics equations were established to describe the two gelation processes and the simulated values are in good agreement with the experimental data. The changes of the model parameters with respect to temperature are quite similar for both the gelation processes, which verifies the feasibility of the microrheology method for measuring the static crosslinking reaction.     

Quality of Emulsions Based on Modified Watermelon Seed Oil,Stabilized with Orange Fibres

The aim of the study was to evaluate emulsion systems prepared on the basis of blended fat in different ratios (watermelon seed oil and mutton tallow) stabilised by orange fibres and xanthan gum. Emulsions were subjected to stability testing by Turbiscan and were assessed in terms of mean droplet size, colour, viscosity, texture, skin hydration and sensory properties. The most stable systems were found to be the ones containing a predominance of mutton tallow in a fat phase. For these emulsions the lowest increase in mean particle size during storage was observed. The study also confirmed the synergistic effect of the thickeners used. The presented emulsions despite favourable physicochemical parameters, did not gain acceptance in sensory evaluation.     

电位滴定法研究多胺铕铽络合物稳定性及其对磷酸二酯键水解断裂

用电位滴定法研究了24元大环多胺(BDBPH)-Eu(Ⅲ)和BDBPH-Tb(Ⅲ)溶液中络合物的稳定性和物种分布,分析了不同pH条件下各物种的存在形式及变化趋势。发现当3个质子被中和后BDBPH才与稀土离子发生配位,分别形成质子化和脱质子化的比较稳定的单核和双核络合物。BDBPH与Tb(Ⅲ)能够形成单羟基、双羟基和三羟基配位的双核络合物。选择BDBPH-Tb络合物体系(1∶2)研究对模型化合物-二(对硝基苯酚)磷酸酯(BNPP)的催化水解作用,得到了其二级反应速率常数(kBNPP=2.3×10-3((mol/L)-1.s-1)和络合物体系的有效物种(L-Tb2-OH),其催化机理可能是Lew is酸碱催化机理,即络合物中双金属和配位羟基分别进攻磷酯基团中的O和P,加速了原有P O键的断裂。研究结果为进一步模拟核酸酶对DNA或RNA的水解断裂提供了重要资料。     

Incubation Effect of Pre-Irradiation on Bubble Formation and Ablation in Laser Ablation in Liquids

Pulsed laser ablation in liquids (PLAL) is a multi-scale process, which is widely studied either in batch ablation with prolonged target irradiation as well as mechanistic investigations, in a defined (single-shot) process. However, fundamental studies on defined pulse series are rare. We have investigated the effect of a developing rough morphology of the target surface on the PLAL process with nanosecond pulses and, partially, picosecond pulses. At low fluence the cavitation bubble growth as well as the ablation yield depend on the irradiation history of the target. The bubble size increases with repeated irradiation on one spot for the first 2–30 pulses as well as with the applied dose. This is discussed within the framework of incubation effects. Incubation is found to be important, resulting in a bubble volume increase by a factor of six or more between pristine and corrugated targets. The target surface, changing from smooth to corrugated, induces a more efficient localization of laser energy at the solid-liquid interface. This is accompanied by a suppressed reflectivity and more efficient coupling of energy into the laser-induced plasma. Thus, the cavitation bubble size increases as well as ablation being enhanced. At high fluence, such incubation is masked by the rapid development of surface damage within the first shots, which eventually would lead to a reduction of bubble sizes.     

二氧化硅纳米管的稳定性及尺寸效应

运用密度泛函计算, 对无水(SiO2-NTs)和水合(SiO2-WNTs)的SiO2纳米管进行结构优化和频率计算, 研究了与尺寸有关的平均结合能和红外光谱. SiO2-WNTs中发现当纳米管的层数或长度相同时平均结合能相等. SiO2-WNTs比SiO2-NTs和二元环直链结构都要稳定. 对截面为四元环的纳米管红外光谱的分析发现, 振动峰值与实验值相吻合, 且切向和径向振动显示较强的尺寸效应. SiO2-WNTs是一维SiO2纳米管一种合适的结构模型.     

The Effect of Grains Size and Temperature on Superconducting Parameters

A survey of published data on the effect of the grains size and temperature on magnetic parameters of YBa2Cu3O7 is given. The magnetization values are divided into two major parts. 1. Intrinsic parameters such as: Hc1, Hc2, λ etc which are not affected by the grains size and 2. values such as: the shielded and Meissner fractions, the intragrain critical current density (Jc) and the demagnetization factor which reflect specific features of the real size of the granular ceramic superconductor. The close relation between the grains size and the second group of parameters is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

一些聚合物对中相微乳液物性的影响

研究了水解聚丙烯酰胺、黄原胶和木质素磺酸盐对中相微乳液相体积、粘度和界面张力的影响。实验结果表明: 含有聚丙烯酰胺时,中相微乳液的相态、增溶参数、中相与下相间界面张力及中相粘度均无明显变化。生物聚合物对中相微乳液的物理性质影响也不大。木质素磺酸盐则对微乳液的形成产生明显影响: 随着木质素磺酸盐浓度的增大,微乳液由中相转变为上相,相应的物理参数亦有变化。     

氯化乙丙共聚物的热行为与稳定性研究

用TMA、DSC和丁G/DTG研究了氯化乙丙共聚物CEP的热行为和稳定性。结果表明:在相同氯含量时,丙烯组份含量高的CEP的软化温度和分解活化能均较高;乙、丙组份比相同的CEP的软化温度随氯含量增加而升高。在氯含量大于50％时,CEP脱HCl活化能显著增加。在CEP中加入热稳定剂,可有效地改善它的稳定性。在所试验的6种稳定剂中,以二盐基亚磷酸铅的效果最好。     

粒度对多相反应动力学参数的影响

以纳米氧化锌与硫酸氢钠溶液为反应体系, 研究反应物粒度对动力学参数的影响规律. 讨论了表观活化能降低的原因. 结果表明：当反应物粒径、反应温度和搅拌速率一定时, 纳米氧化锌与硫酸氢钠溶液的反应速率仅与反应物的浓度有关；反应物粒度对多相反应的反应级数、速率常数、表观活化能和指前因子均有较大的影响；随着反应物粒径的减小, 表观活化能和指前因子减小, 而反应级数和速率常数增大, 并且速率常数和表观活化能与反应物粒径的倒数呈线性关系；反应物粒度是通过摩尔表面积、摩尔表面能和摩尔表面熵三个方面影响多相反应的动力学参数的.     

Characterization of Monomer Emulsions in Terms of Droplet Size and Stability: Effect of Emulsifier Concentration

In emulsification processes, the estimation of the droplet size distribution is important data not only because it is linked with the manufacturing process, but also because it is an important parameter affecting the emulsion stability. The aim of this research is to use the ultraviolet-visible transmission spectrum as a tool for emulsion characterization (droplet size and stability) to be a function of monomer concentration, and to verify of emulsion stability using the volume of separated phase's technique. Both techniques are applied to monomer emulsions as a function of emulsifier concentration. Results show correlations between droplet size measurements and stability of emulsions using the spectroscopy technique; results were also found to be in agreement using the cleared volume method.