Temperature/salt tolerance and oil recovery of xanthan gum solution enhanced by surface-modified nanosilicas

Amide-and alkyl-modified nanosilicas(AANPs)were synthesized and introduced into Xanthan gum(XG)solution,aiming to improve the temperature/salt tolerance and oil recovery.The rheological behaviors of XG/AANP hybrid dispersions were systematically studied at different concentrations,temperatures and inorganic salts.At high temperature(75C)and high salinity(10,000 mg,L1 NaCl),AANPs increase the apparent viscosity and dynamic modulus of the XG solution,and XG/AANP hybrid dispersion exhibits elastic-dominant properties.The most effective concentrations of XG and AANP interacting with each other are 1750 mg·L^(-1) and 0.74 wt%,respectively.The temperature tolerance of XG solution is not satisfactory,and high temperature further weakens the salt tolerance of XG.However,the AANPs significantly enhance the viscoelasticity the XG solution through hydrogen bonds and hydrophobic effect.Under reservoir conditions,XG/AANP hybrid recovers approximately 18.5%more OOIP(original oil in place)than AANP and 11.3%more OOIP than XG.The enhanced oil recovery mechanism of the XG/AANP hybrid is mainly increasing the sweep coefficient,the contribution from the reduction of oil-water interfacial tension is less.

Mechanical properties and deformation mechanisms of surface-modified 6H-silicon carbide

The effect of amorphous film on the deformation mechanism and mechanical properties of 6 H-SiC were systematically explored by a combination of both experiments and molecular dynamic(MD)simulations in nanoindentation.The experimental results showed that the plastic deformation of surface-modified6 H-SiC is mainly accommodated by dislocation activities in the subsurface and an amorphous layer with uniform thickness.The MD results indicated that the amorphous layer on the surface of the residual indentation mark consists of both amorphous SiO_(2)and SiC due to direct amorphization.In addition,the amorphous SiO_(2)film undergoes densification and then ruptures with the indentation depth increases.The modulus and hardness increase with increasing the indentation depth at the initial stage but will reach their stable values equivalent to monocrystalline 6 H-SiC.

Experimental investigation of enhancement of carbon dioxide foam stability, pore plugging, and oil recovery in the presence of silica nanoparticles

The influence of surface-modified silica(SiO_2) nanoparticles on the stability and pore plugging properties of foams in porous media was investigated in this study. The pore plugging ability of foams was estimated from the pressure drop induced during foam propagation in porous media. The results clearly showed that the modified Si02 nanoparticlestabilized foam exhibited high stability, and the differential pressure increased in porous media by as much as three times.The addition of SiO_2 nanoparticles to the foaming dispersions further mitigated the adverse effect of oil toward the foam pore plugging ability. Consequently, the oil recovery increased in the presence of nanoparticles by approximately 15%during the enhanced oil recovery experiment. The study suggested that the addition of surface-modified silica nanoparticles to the surfactant solution could considerably improve the conventional foam stability and pore plugging performance in porous media.

Treatment of mine water high in Fe and Mn by modified manganese sand

The iron and manganese absorption properties of several filter media were studied. Four plain filter media and six surface-modified media were examined. The surface modification was performed using potassium permanganate as a surface treatment. The surface-modified manganese sand was found to be most efficient at removing iron and manganese from water. The metal concentrations in filtered effluent were between 0.01 and 0.04 mg/L, which is far lower than the standard for recycle water. A concen-tration of 5% KMnO4 was found to be most effective as surface modifier. The surface of the manganese sand modified by 5% KMnO4 was examined and found to be covered with a dense membrane of some compound. The membrane had the advantages of uniform texture, large surface area and physical and chemical stability. It was effective at removing iron and manganese from mine water.

Surface BrØnsted-Lewis dual acid sites for high-efficiency dinitrogen photofixation in pure water

As is known to all, nitrogen not only plays an important role in the industrial development of human society but also plays an important part in the proteins that constitute the essence of life[1]. In 1910, the Haber-Bosch process was first used to synthesize ammonia.

Microstructure evolution and acicular ferrite nucleation in inclusion-engineered steel with modified MgO@C nanoparticle addition

To investigate the effect of surface-modified nanoparticles(NPs)on the inclusion refinement and microstructure evolution,deoxidized experiment ingots with different amounts of modified NPs were manufactured under different cooling conditions.Laser scanning confocal microscope(LSCM)was hereby used for in-situ observation of the phase transition and microstructural evolution during heat cycle process.The results revealed that the inclusion size was always smaller under water quenching than under air cooling,and the number of inclusions was greater under water quenching.After NP addition,the nucleant inclusions were identified as MgAl_(2)O_(4)spinel and irregular TiN inclusion from SEM-EDS measurement and equilibrium calculations using Factsage thermodynamic software.The higher cooling rate under water quenching resulted in less polygonal ferrite decrease and the formation of bainite in the steel.The LSCM experiments showed that ferrite side plates(FSP)always formed on the boundary prior to the formation of acicular ferrite(AF)on the intragranular inclusions,and the start transformation temperatures of FSP and AF phases both lowered after NP addition.The higher cooling rate and NP addition contributed to AF formation and increased the degree of interlocking of the AF phase.Finally,the relationship between the characteristics of inclusions and the kinetics of AF was investigated.