【作者】 郭斌；

【导师】 叶国田；

【作者基本信息】 郑州大学 ， 材料工程（专业学位）， 2017， 硕士

【摘要】 由于硅溶胶结合浇注料的脱模强度低,未能得到广泛的应用。关于胶凝剂对硅溶胶结合浇注料的常温物理性能和高温使用性能的研究已经很多,然而具体到胶凝剂是如何影响硅溶胶粒子间化学键重组的研究报道很少。因此,本工作主要利用傅里叶红外光谱(FTIR)分析和X-射线光电子能谱(XPS)分析手段来考察胶凝剂对硅溶胶粒子在养护过程中化学键重组的影响,进而系统地探究硅溶胶结合浇注料的脱模强度与硅溶胶化学键重组的内在联系。实验结果表明,胶凝剂(铝酸钙水泥(CAC)、氢氧化镁(Mg(OH)2)或镁砂(MgO))加入到硅溶胶后,硅溶胶的电导率会随着搅拌时间的延长而呈现降低趋势,并逐渐趋于稳定。扫描电子显微镜(SEM)显微结构显示,随着养护温度的升高,未加胶凝剂的硅溶胶中的部分Si O2粒子相互连接,颗粒尺寸变大。而胶凝剂(CAC、Mg(OH)2或MgO)加入到硅溶胶后,硅溶胶中更多的SiO2粒子连接成整体。并且,养护温度越高(60°C),硅溶胶中SiO2粒子连接的越多。FTIR光谱分析结果显示,1115 cm-1、799 cm-1和474 cm-1处分别为Si-O-Si的反对称伸缩、对称伸缩和弯曲振动峰,以及976 cm-1处为Si-OH的振动峰。硅溶胶中胶凝剂CAC的加入,在FTIR光谱中发现Si-O-Al(876 cm-1)、Si-O-Ca(858 cm-1)新的微弱振动峰。而胶凝剂Mg(OH)2或MgO的加入,则在FTIR光谱中发现Si-O-Mg(864 cm-1)的新的微弱振动峰。XPS能谱分析发现,相比未加胶凝剂CAC的硅溶胶,硅溶胶中加入0.5%CAC,60°C养护24 h后的XPS全谱中观察到了Ca 2p(~346 e V)、Ca 2s(~439eV)和Al 2p(~74 eV)的特征峰。证实了CAC水化溶解出的Al3+和Ca2+离子参与了硅溶胶的缩合反应。同样,硅溶胶中加入0.5%Mg(OH)2(或MgO),60°C养护24 h后的XPS全谱中可以观察到Mg 1s(~1302 eV)、Mg 2s(~87 eV)和Mg 2p(~48 eV)的特征峰。并且养护温度越高,Mg 1s、Mg 2s和Mg 2p的特征峰的强度越高,证实了氢氧化镁水解(或镁砂水化)释放出的Mg2+离子参与了硅溶胶的缩合反应,养护温度越高,促凝效果越好。拟合相应O 1s谱图的结果再次证实了硅溶胶中加入胶凝剂(CAC、Mg(OH)2或MgO)后会出现Si-O-M(M:Al,Ca,Mg)新的化学键。硅溶胶结合浇注料的脱模强度结果显示,胶凝剂(CAC、Mg(OH)2或MgO)的加入均提高了浇注料的脱模强度。并且脱模强度增加的趋势与硅溶胶中新化学键Si-O-M(M:Al,Ca,Mg)增加的趋势一致。这些新化学键Si-O-M(M:Al,Ca,Mg)将硅溶胶中SiO2粒子连接在一起,并形成一个稳定的三维的网络结构,进而提高浇注料脱模强度。因此可以推断,硅溶胶结合浇注料的脱模强度与硅溶胶化学键的重组密切相关。更多还原

【Abstract】 The low demoulding strength of colloidal silica-bonded castables has narrowed the range of application.There are many researches on the physical properties of room temperature and high temperature performance of colloidal silica bonded castables,while rare researches investigate the influence of gelling agent on the change of chemical bonds between Si O2 particles of colloidal silica.Therefore,this work aims to study the relationship between demoulding strength and the change of chemical bonds of the particles of colloidal silica with and without gelling agent.The influence of different gelling agents(calcium aluminate cement(CAC),magnesium hydroxide(Mg(OH)2)or magnesia(Mg O))on the change of chemical bonds of colloidal silica(solid content of 30%)was investigated during the dehydration condensation reaction.The chemical bonds of the colloidal silica were investigated by Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)to systematically characterize the relationship between the chemical bonds and demoulding strength of colloidal silica bonded castables.The results show that the conductivity of colloidal silica decreased with the addition of gelling agent(CAC,Mg(OH)2 or Mg O),then gradually stabilized.Some Si O2 particles in colloidal silica were bonded each other with the increase of curing temperature.With the addition of the gelling agent,more Si O2 particles in colloidal silica were connected with each other.Moreover,the higher the curing temperature(60°C),the more obviously the morphological change.FTIR spectral analysis results show that the band at 1115 cm-1 was assigned to the Si-O-Si asymmetrical stretching vibration,while the band at 799 cm-1 on behalf of the symmetrical stretching vibration,the band at 474 cm-1 belonged to the bending vibration of Si-O-Si and the band at 976 cm-1 is the Si-OH vibration.New peaks of Si-O-Al(876 cm-1)and Si-O-Ca(858 cm-1)bonds were observed in the FTIR spectra with the addition of CAC.While the new weak vibration peak of Si-O-Mg(864 cm-1)binding could be found in the FTIR spectra with the addition of Mg(OH)2 or Mg O.XPS spectra analysis showed that Ca 2p(~346 e V),Ca 2s(~439 e V)and Al 2p(~74 e V)could be observed in the XPS spectra with the addition of CAC(added 0.5% and cured 24 h at 60°C).It was confirmed that the Al3+ and Ca2+ ions dissolved by the hydration of CAC involved in the condensation reaction of colloidal silica.Mg 1s(~1302 e V),Mg 2s(~87 e V)and Mg 2p(~48 e V)were observed in the XPS spectra of colloidal silica with the addition of Mg(OH)2(or Mg O)(added 0.5% and cured 24 h at 60°C).The higher the curing temperature,the more obvious the characteristic peaks of Mg 1s,Mg 2s and Mg 2p,which confirmed that the Mg2+ ions released from the hydrolysis of Mg(OH)2(or hydration of Mg O)were involved in the condensation reaction,and the higher the curing temperature,the better the coagulation.The results of the corresponding O 1s spectra were again confirmed the new chemical bonds of Si-O-Al and Si-O-Ca were formed with the addition of CAC.And the new chemical bond of Si-O-Mg was formed with the addition of Mg(OH)2(or Mg O).The demoulding strength of colloidal silica bonded castables increased with the addition of gelling agent(CAC,Mg(OH)2 or Mg O).The increased demoulding strength coincides with the formation of new chemical bonds of Si-O-M(M: Al,Ca,Mg)in the colloidal silica.These new chemical bonds of Si-O-M(M: Al,Ca,Mg)will connect colloidal silica particles together,and form a three-dimensional network structure,which will bond castable particles into a whole,increasing the demoulding strength of castables.It can be deduced that the increase of demoulding strength of colloidal silica bonded castables is closely to the recombination of chemical bonds of colloidal silica.更多还原