Experiment on the silica sol imbibition of low-permeability rock mass:With silica sol particle sizes and rock permeability considered

It’s a universal engineering problem to seal micro-cracks of low-permeability argillaceous rock mass by grouting in the fields of civil engineering and mining.This paper achieved the grouting sealing of lowpermeability artificial rocks with the permeability of 0.1–40 mD by adopting silica sol imbibition grouting.The variation characteristics of particle size,viscosity,and contact angle of silica sol during solidification and the pore size distribution of low-permeability artificial rocks were measured,and spontaneous imbibition tests of the artificial rocks were carried out.Finally,combined with the imbibition theory,percolation theory,and fracture medium grouting principle,the silica sol imbibition mechanism of lowpermeability rocks and soil was discussed.The results show that:(1)Silica sol can be injected into artificial rocks with the minimum permeability of 0.1 mD through spontaneous imbibition;(2)The particle size increase of silica sol leads to decreased wettability,affinity,and injectability in grouting materials;and(3)In the range of 0.1–40 mD,the grout absorption first increases and then decreases with increased permeability.The number of large pores and fractures in the rock mass is related to injectability,and the number of small and medium pores is related to the internal driving force of imbibition.This study provides a theoretical basis for silica sol grouting sealing of low-permeability argillaceous rocks and is,therefore,an important reference for application.

Synthesis of Nanometer-sized Mesoporous Oxide Spheres

A few hundreds nanometer-sized mesoporous silica and alumina spheres were synthesized in organic solvents. The impacts of ammonia, N, N-dimethylformamide (DMF) and stirring speed were also investigated.

Preparation and Application of Silica-based Perfusion Packing of Size Exclusion Chromatography for Quantitation of Polyacrylamide in Enhanced Oil Recovery Systems

The synthesis and characterization of a novel macroporous silica derived size exclusion chromatography （SEC） packing for quantitative analysis of high molecular weight （MW） polyacrylamide （PAM） are presented. Using this packing, a fast, sensitive and reproducible approach for quantitation of super high-MW PAM in demanding enhanced oil recovery （EOR） waters was developed and the effect of synthesis parameters on the properties of resultant materials was investigated. These parameters include salt addition, reaction temperature and duration, activation condition of functional groups on the silica surface, as well as the reaction cycles required for optimal silica modification. Moreover, SEC analysis conditions, such as mobile phase composition, flow rate, detection and sample preparation, were also explored and an optimal analysis protocol was developed. Under this optimized SEC analysis conditions, the synthesized macroporous materials proved satisfactory for quantification of PAM with average MW up to 22 million Daltons. An SEC analysis required less than few minutes with a detection limit of 1 ng, a linear response range of 0.1 to 75 mg/L with squared R value of 0.99 and reproducibility better than 9.2% RSD （relative standard deviation）. The analysis of PAM in highly saline oilfield production water containing interfering high MW polymeric surfactants indicated the recovery ranges from 92.5% to 110.1% for 1.0 mg/L PAM and 94.2% to 103.8% for 50 mg/L PAM solution. This study presented for the ftrst time that the reliable quantization of high MW PAM in highly demanding EOR waters can be achieved by SEC.

The Effect of Silica Particle Size on the Performance of Color Ink-jet Printing Paper

In this paper,the effects of four sorts of silica with the particle size range of 4～10μm on coated paper properties and printing performance were studied.The results showed that the smaller particle size silica can provide the coated paper with higher density and contrast, better definition and good printing performance.

Synthesis of Mesoporous Silica Nanoparticles with Tunable Shape and Size

The structural and morphological properties of mesoporous silica nanoparticles( MSNs) have dramatical influence on their in vivo biological behaviors,and thereby synthesis of MSNs with well-defined shape and size has recently attracted much more attention in the biomedical field. The synthesis of MSNs with controllable size and shape was presented by controlling the reaction temperature and the concentration of templating agent(cetyltrimethylammonium bromide,CTAB). The results indicated that MSNs were larger in particle size and more round in shape with increasing of the reaction temperature,but their particle size and dispersivity became smaller and poorer as CTAB concentration increased. Therefore,the particle size and shape of MSNs can be tuned by using the optimal synthesis conditions for specific biomedical applications.

Effect of Pore Size on Properties of Highly Porous Silica Ceramic Foams for Heat Insulation

Highly porous silica ceramics with different pore sizes were fabricated by adjusting the mixed surfactants addition.The effect of the pore size on the cold compressive strength and the thermal conductivity of the ceramics was researched.The results show that the smaller pore size can improve the compressive strength and the thermal conductivity.With the mixed surfactants addition increasing from 0.1 mass%to 0.4 mass%,the porosity is close,in the range of 88.10%-88.31%,and the average pore size decreases from 190μm to 97μm;the compressive strength is enhanced from 2.97 MPa to 3.55 MPa;and the thermal conductivity decreases from 0.104 W·m-1·K-1 to 0.089 W·m-1·K-1.

稻壳灰粒径对水泥砂浆的碱硅酸反应风险影响

固废资源化是实现可持续发展的重要内容.稻壳灰的火山灰活性高,有望作为辅助性胶凝材料用于水泥砂浆或混凝土,但其中K 2O和Na 2O含量较大,需探明不同粒径稻壳灰的掺入可能带来的碱硅酸反应风险.现有研究表明,粉煤灰的火山灰活性能抑制碱硅酸反应,已得到广泛应用.对比起见,设置了基准组、掺4种粒径粉煤灰组和稻壳灰组,在分别测试其抗压、抗折强度的基础上,测试膨胀率,通过SEM和EDS测试了掺粒径为5μm的稻壳灰试件和未掺稻壳灰试件的微观形貌和元素组成.试验结果表明:稻壳灰或粉煤灰的掺入均可以提高砂浆的力学性能,稻壳灰粒径越小提高的程度越大,中值粒径为5μm的稻壳灰可以使砂浆28 d抗压强度提高50.6%,抗压强度提高64.7%,效果均好于粉煤灰;稻壳灰的粒径不超15μm时,对砂浆的膨胀率可起到显著的抑制作用,且抑制效果优于粉煤灰,5μm的稻壳灰能使14 d膨胀率减小90%,并使骨料表现为无害,而8~20μm粉煤灰均仅减小60%左右的14 d膨胀率,骨料仍表现为有害;稻壳灰的火山灰活性不仅能生成低Ca/Si比的C-S-H凝胶,降低碱含量,还能使砂浆致密性提高,抑制碱离子和水的渗透,从而表现为对碱硅酸反应的抑制效果.

温度对高硅氧基体玻璃纤维性能的影响及其机理探索

针对经石蜡型浸润剂涂覆后的高硅氧基体玻璃纤维原丝,在高温环境下性能、生产利用率下降的问题,深入研究了温度对其性能的影响规律,并对机理进行了讨论。采用红外、热重、扫描电镜等分析手段,对不同形态的高硅氧基体玻璃纤维原丝在不同温度、不同存放时间下的性能进行了表征。结果表明,随着温度的升高,浸取液碱性增强,机械性能下降,同时纤维丝表面晶体析出越多,且存在碳酸根。因此,可以得出,温度影响高硅氧基体玻璃纤维性能的根本原因,可能在于高温促进了纤维中Na^(+)运动,加快了其与纤维表面水分子中H+的离子交换,从而加速了纤维结构的破坏,导致性能下降。

溶胶凝胶法制备纳米二氧化硅及性能研究

以绿色环保和有效利用为出发点,采用溶胶凝胶法以正硅酸乙酯为原料、氨水为碱性催化剂,不断调整优化原料配比及反应条件等多个影响因素,得到了粒径大小可控的超疏水纳米溶胶。实验结果表明,当TEOS用量为3 mL、EtOH用量为80 mL、NH_(3)·H_(2)O用量为2 mL,温度为60℃,反应时间为1.5 h,它的官能团、形貌特征和粒径大小通过红外光谱、扫描电镜(SEM)、纳米粒度仪等方法表征,结果表明已经获得平均直径在200 nm以内的纳米SiO_(2)粒子。

尺寸可控有机杂化二氧化硅胶体粒子的制备

有机杂化二氧化硅胶体粒子因其独特的性质被广泛地应用于生物医学领域。对于不同的器官组织,纳米粒子的尺寸不同,因而尺寸可控的有机杂化二氧化硅胶体粒子在生物医学应用中尤为重要。以乙烯基三甲氧基硅烷(VTMS)为硅烷前驱体,氢氧化铵为催化剂,通过硅烷前驱体在碱性条件下自发形成乳液,然后由引发剂过硫酸铵(APS)引发聚合来制备尺寸可控的有机杂化二氧化硅胶体粒子。采用场发射扫描电子显微镜和ImageJ软件,探究了引发剂种类、前驱体浓度、氢氧化铵浓度以及乳化时间等不同条件对有机杂化二氧化硅胶体粒子尺寸的影响。结果表明:前驱体浓度增大会造成有机杂化二氧化硅胶体粒子的尺寸增大,而氢氧化铵浓度增大则起到相反的作用。随着乳化时间延长,有机杂化二氧化硅胶体粒子的尺寸先减小后增大。

碳化法制备高比表面积纳米白炭黑的工艺条件研究

以工业水玻璃为原料,CO_(2)为沉淀剂,着重开展碳化法制备纳米白炭黑的碳化反应过程工艺条件研究。以所制备纳米白炭黑样品的平均粒径、BET值为主要考察指标,筛选并确定较适宜的复配分散剂为2%TTLY+1%TTLX;考察并确定较适宜的碳化反应工艺条件为:体系SiO_(2)质量浓度11%,碳化反应温度60℃,水玻璃模数3.3,Na_(2)CO_(3)初始含量3%;所制备出的纳米白炭黑样品平均粒径为23.43 nm,BET值达到422.77 m^(2)/g,样品为无定形非晶态结构,粒度均匀性和分散性均较好。

功能性二氧化硅微球的制备

考察了正硅酸乙酯、氨水、醇水体积比和反应温度对微球制备的粒径及单分散性影响;制备了粒径180~820 nm可调、形貌均匀的单分散性二氧化硅(SiO_(2))微球。结果表明:随着正硅酸乙酯用量的增大,SiO_(2)微球的粒径逐渐增大;随着氨水用量的增加,SiO_(2)微球的粒径呈先增大后减小的趋势;随着反应温度的升高,SiO_(2)微球的粒径减小;随着醇水体积比的减小,SiO_(2)微球的粒径减小。在此基础上,用3-氨丙基三乙氧基硅烷、戊二酸酐和十八烷基三乙氧基硅烷分别将氨基、羧基和烷基引入到SiO_(2)微球的表面,红外光谱和热分析结果表明,成功制备了功能性SiO_(2)微球。

硅溶胶粒径对取向硅钢绝缘涂层性能的影响

为了探究不同粒径硅溶胶对取向硅钢绝缘涂层性能的影响,分别对使用至少一种粒径硅溶胶的绝缘涂液及涂层性能进行研究。实验表明:使用小粒径硅溶胶的涂液更稳定,并且能提升涂层与底层的结合程度,具有较大的硬度和较小的铁损;使用大粒径硅溶胶能提升涂液的润湿性能,并能有效提升涂层光泽度,使涂层更容易结晶,按照一定比例混合时还能略微提升涂层的耐腐蚀性能。

Gold nanoparticle stabilization within tailored cubic mesoporous silica:Optimizing alcohol oxidation activity

Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic mesoporous silica（FDU-12） as a function of pore entrance size.Simple adjustments to the type of organic template and reaction temperature enable the successful synthesis of FDU-12 with controllable entrance sizes（ 3,3-5 and 7 nm）.Excellent anti-sintering properties are observed for FDU-12 with a sub-5-nm entrance size（3-5 nm） over a wide loading concentration（1.0-8.3 wt%） and the AuNPs can be stabilized within a 4.5-5.0-nm range after calcination at 550 ℃in air for 5 h.Smaller entrance size（ 3 nm） prevents ingress of 3-nm AuNPs to the mesopores and results in low loading capacity and sintering.Conversely,FDU-12 possessing a larger entrance size（7 nm） shows promising anti-sintering properties at high loading concentrations,although catalytic performance is significantly lost at lower concentrations（e.g.2.1 wt%,14.2 ± 5.5 nm）.Different anti-sintering mechanisms are proposed for each of the different FDU-12 entrance sizes.Additionally,catalytic data indicates that the obtained 4.5-nm AuNPs supported on FDU-12 with a sub-5-nm entrance size exhibit excellent mass-specific activity（1544 mmol g_（Au）^（-1） h^（-1）） and selectivity（ 99%）at 230 ℃ for the gas-phase selective oxidation of cyclohexanol.

Effects of support pore size on new Cs_(2.5)H_(0.5)PW_(12)O_(40)/SiO_2 catalysts for the ring-opening polymerization of tetrahydrofuran

Mesoporous silica supported Cs2.5H0.5PW12O40 catalysts were prepared by impregnation method, and several silica supports with different pore size were utilized. N2 adsorption, XRD and ICP-AES techniques were utilized to characterize the silica supports and catalysts. XRD results showed that the dispersion of Cs2.5H0.5PW12 was better for the silica support with larger pore size. The catalytic activity results showed that the pore size played important role on the catalyst activity and the molecular weight of PTHF. When Cs2.5H0.5PW12O40 was dispersed on larger pore size silica support, the catalysts showed good performances for the synthesis of PTHE The molecular weight of PTHF product on the sample in which Cs2.5H0.5PW12O40 was dispersed on larger pore support was higher than that on the catalyst with smaller pore support. The leaching amounts of the active components for the supported Cs2.5H0.5PW12O40 catalysts were much lower. After five reaction cycles, there were still good activities and stabilities for the supported Cs2.5H0.5PW12O40 catalysts with larger pore silica supports. These results were much better than those of the supported heteropolyacid H3PW12O40 catalyst.

Microstructure of β-Dicalcium Silicate after Accelerated Carbonation

The present work presents the microstructure of β-Ca_2SiO_4(β-C_2S) after accelerated carbonation. The synthesis procedure of β-C_2S was examined first, and the crystalline and amorphous structure, the distribution and the pore structure of β-C_2S carbonation products were also determined by X-ray diffraction(XRD) quantitative analysis, simultaneous thermal analyzer(TG/DTA), Fourier transform-infrared spectroscopy(FT-IR), high resolution ^(29)Si magic angle spinning nuclear magnetic resonance(^(29)Si NMR), N_2-sorption techniques, and scanning electron microscopy(SEM), respectively. Test results indicate that carbonation products are dramatically formed in the initial 2 h. The main carbonation products are crystalline calcite and amorphous three-dimensional network silica gels, which contain nanometer-sized pores. The calcite, silica gels and un-carbonated β-C_2S are distributed hierarchically.

Calculation of Alkali Silica Reaction (ASR) Induced Expansion before Cracking of Concrete

A calculation method for predicting the formation of alkali-silica gel and analyzing the relationship of ASR induced expansion and aggregate size was proposed. The complicated chemistry of alkali silica reaction was simplified to be controlled by the diffusion process of chemical ions into reactive aggregates. The transport of chemical ions was described by the Fick＇s law. The ASR induced expansion was assumed to be directly related to the volume of produced alkali-silica gel. The finally expansion of a representative volume element （RVE） of concrete was then calculated according to the ratio of volume of alkali-silica gel and RVE. The input parameters of the model contains radius of reactive aggregate, volume fraction of reactive aggregate, initial concentration of chemical ions and porosity of cement paste. The applicability of the model was validated by an experiment of ASR-affected concrete specimens containing glass aggregate. It is shown that the amount of alkali-silica gel and ASR induced expansion can be well predicted. The expansion increasing with the decreasing aggregate size can be reproduced by the proposed model.

Synthesis and Characterization of Bimodal Mesoporous Silica

Mesoporous silica with controllable bimodal pore size distribution was synthesized with cetyltrimethylammonium bromide （CTAB） as chemical template for small mesopores and silica gel as physical template for large mesopores. The structure of synthesized samples were characterized by Fourier transform infrared （FT-IR） spectroscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and N2 adsorption-desorption measurements. The experimental results show that bimodal mesoporous silica consists of small mesopores of about 3 nm and large mesopores of about 45 nm. The small mesopores which were formed on the external surface and pore walls of the silica gel had similar characters with those of MCM-41, while large mesopores were inherited from parent silica gel material. The pore size distribution of the synthesized silica can be adjusted by changing the relative content of TEOS and silica gel or the feeding sequence of silica gel and NH4OH.

Effects of Flame Temperature and SiCl_4 Concentration on Particle Characteristics for Synthetic Silica Glass

Effects of flame temperature and SiCl4 concentration on the particle characteristics were studied.The flame temperature distributions were measured using modified sodium line-reversal technology.The particles were collected by quartz supports and were analyzed by scanning electron microscope（SEM） at different locations along the flame centerline.When the SiCl4 concentration is 16 g/min,the particles first grow and then shrink with the flame temperature increasing.When the SiCl4 concentration is 26 g/min,the flame temperature has little influence on the particle characteristics along the flame and many large spherical particles exist all the way.

Polydisperse spherical colloidal silica particles：Preparation and application

A new industrial method has been developed to produce polydisperse spherical colloidal silica particles with a very broad particle size,ranging from 20-95 nm.The process uses a reactor in which the original seed solution is heated to 100 ℃,and then active silicic acid and the seed solution are titrated to the reactor continuously with a constant rate.The original seeds and the titrated seeds in the reactor will go through different particle growth cycles to form different particle sizes.Both the particles＇ size distribution and morphology have been characterized by dynamic light scattering（DLS）and the focus ion beam（FIB） system.In addition,the as-prepared polydisperse colloidal silica particle in the application of sapphire wafer＇s chemical mechanical polishing（CMP） process has been tested.The material removal rate（MRR） of this kind of abrasive has been tested and verified to be much faster than traditional monodisperse silica particles.Finally,the mechanism of sapphire CMP process by this kind of polydisperse silica particles has been investigated to explore the reasons for the high polishing rate.