Preparation And Characterization Of Ni-doped Methyl-modified Silica Membrane Material

Sol-gel prepared SiO2 membrane for gas separation have great application prospect.It's choice of hydrogen has good permeability,simple process,low cost,strong regeneration membrane.Used for industrialized mass production can greatly reducing the production cost.the traditional SiO2 film has obvious hydrophilic,membrane structure and the aperture in a hydrothermal environment are affected which greatly reduce the use of membrane efficiency and life span.This article through the introduction of hydrophobic groups in SiO2 membrane material surface-methyl and doping transition metal nickel and two improved methods of porous SiO2 membrane materials were modified at the same time,?Increasing its hydrophobicity and water thermal stability.Experiments use sol-gel method to fabricate nickel load and methyl modified SiO2 membrane materials,Using ethyl silicate as precursors,methyl triethoxy silane providing-CH3,six water nickel nitrate as the source of nickel.Under the condition of ethanol liquid mixed of the reactants.(1)The experimental studied methyl modified silica membrane sol with nickel doped.The study found that the gel solids increased with the increasing of the nNi,its growth trend in accord with the linear growth.gel time decreased with the increasing of nNi,gel time fell sharply when the nNi is less than 0.1.As Ni doping quantity was big,sol viscosity was bigger,its growth rule fit the linear growth.sol particle size and zate potential test showed that the nickel load should not be less than the nNi=0.1,but also should not be too big,when the nNi=0.2,the particle size distribution and change trend,poor stability and sol state.Sol IR shows the mixed state of nickel has no effect on modification of methyl.(2)Experiment studied the morphology of nickel element in SiO2 skeleton network and crystal structure and pore structure of the membrane material.The study found that both in air and nitrogen atmosphere calcined samples containing Ni-O-Si structure.For sample of air roasting atmosphere,the presence of nickel form is micro crystalline NiO and the crystal size increased with the rising calcination temperature with the trend of crystallization.For Samples roasting with nitrogen atmosphere,when the calcination temperature is not higher than 500?,the existing form of nickel is micro crystalline NiO.When roasting temperature reaching 600?,micro crystalline NiO will revert to elemental crystal Ni.Membrane pore size distribution and pore ratio:samples with calcined in air atmosphere,the micropore rate is extremely high,the microporous membrane material rate of nNi=0.1 can reach 80%.And smaller pore size distribution,the average aperture in 2 nm.The nNi=0.2 of membrane materials appeared more mesoporous,microporosity fell and the pore size increased.Nitrogen atmosphere calcined samples compared to the sample of air roasting atmosphere,specific surface area of the membrane material increased with high porosity,but the pore size distribution and pore rate data clearly lowed than air atmosphere roasting of the membrane material.(3)Experiment studied the hydrophobicity of membrane material,the results found that in air and nitrogen atmosphere roasting of membrane material,after a week in water and gas environment,the sample of the nNi=0.1,microporous area reduction of BET specific surface area respectively was 74.5%.Compared with control group and nickel doped membrane material in water and gas environment,the microporous membrane material area down more with nickel doped membrane material.Micropore volume is relatively small amounts of 12.6%.SiO2 membrane material roasting in Air atmosphere have the of membrane contact Angle and surface free energy:for SiO2 membrane nNi=0.1,with the increase of calcination temperature,the surface of distilled water contact Angle decreased,and the corresponding membrane surface free energy is on the rise as a whole.The different samples of calcinating at 350?:With the increasing of nNi,the surface free energy is on the rise.Membrane surface free energy calculations show that the mixed nickel leads to the increase of membrane surface polarity force,which results in the decrease of membrane surface wettability and hydrophobic decline.