调控亲有机黏土分散体系的力学性能：颗粒组成与预剪切历史的影响
Tuning the mechanical properties of organophilic clay dispersions: particle composition and preshear history effects
AI总结：
该研究探究了颗粒组成与预剪切历史对亲有机黏土分散体系力学性能的影响，揭示了片状、针状颗粒及其混合物的浓度依赖规律，发现预剪切可显著调控黏弹性，为可定制力学响应的有机黏土分散体系设计提供了依据。
摘要：
黏土矿物是储量丰富的天然材料，广泛应用于涂料、建筑材料、陶瓷领域，同时也是钻井液的组分之一。本文研究了稳态与振荡预剪切对合成油中亲有机改性黏土凝胶的影响。片状颗粒与针状颗粒均被用作钻井液配方中的增黏剂。对于两种颗粒，其平台模量表现出相似的浓度依赖关系，即G_P ~ c^3.9；而屈服应变方面，片状颗粒为γ_y ~ c^(-1)，针状颗粒为γ_y ~ c^-1.7。两种颗粒的混合物表现出介于两者之间的行为：低浓度下，其弹性和屈服应变与针状颗粒一致，而在更高浓度下则表现出更弱的幂律依赖关系。此外，通过改变预剪切历史，凝胶的黏弹性可得到显著调控。在较低（较高）黏土浓度下，特定振荡应变幅度或稳态剪切速率下的预剪切可引发分散体系的硬化（软化），且在所有浓度下都会降低剪切应变。因此，在针状颗粒分散体系中，预剪切导致弹性模量的体积分数依赖关系从G_P ~ c^3.9变为G_P ~ c^2.5，屈服应变的体积分数依赖关系从γ_y ~ c^-1.7变为γ_y ~ c^-1。然而，小角X射线散射结果显示，在所覆盖的q范围内，体系结构未发生明显变化。本研究结果为设计力学响应可按需调控的胶体有机黏土分散体系提供了思路。
英文摘要：
Clay minerals are abundant natural materials used widely in coatings, construction materials, ceramics, as well as being a component of drilling fluids. Here, we present the effect of steady and oscillatory preshear on organophilic modified clay gels in synthetic oil. Both platelet and needle-like particles are used as viscosifiers in drilling fluid formulations. For both particles the plateau modulus exhibits a similar concentration dependence, G_P ~ c^3.9, whereas the yield strain is γ_y ~ c^(-1) for the platelets and γ_y ~ c^-1.7 for the needles. Mixtures of the two follow an intermediate behavior: at low concentrations their elasticity and yield strain follows that of needle particles while at higher concentrations it exhibits a weaker power law dependence. Furthermore, upon varying the preshear history, the gel viscoelastic properties can be significantly tuned. At lower (higher) clay concentrations, preshear at specific oscillatory strain amplitudes or steady shear rates, may induce a hardening (softening) of the dispersions and, at all concentrations, a lowering of the shear strain. Hence, in needle dispersions preshear resulted in changes in the volume fraction dependence of the elastic modulus from G_P ~ c^3.9 to G_P ~ c^2.5 and of the yield strain from γ_y ~ c^-1.7 to γ_y ~ c^-1. However, small angle X-ray scattering showed not much structural changes, within the q-range covered. Our findings indicate ways to design colloidal organoclay dispersions with a mechanical response that can be tuned at will.
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