Quenched Disorder and the Consolute Point

9617943 Cannell这是一个更新项目，其中激光散射将用于研究模型系统的临界点附近的序参数波动的长度尺度和动力学，该模型系统涉及异丁酸/水混合物，其中含有稀二氧化硅网络。这个系统的临界点位于（在温度上）亚稳畴形成的区域之下，就像随机场磁体的临界点位于亚稳“冻结畴”状态之下一样。与磁体的情况不同，对于流体混合物存在达到平衡状态的简单方法。（使含有混合物的凝胶与流体混合物的储器接触允许其达到平衡。这种令人高兴的巧合将允许在临界点附近的平衡系统上进行实验，这对于随机场磁体是不可行的。这是一个更新项目，其中将进行实验以研究非常稀的多孔材料如何影响某些相变。所研究的相变是两种液体的分层，多孔材料将是合成石英（二氧化硅）的纤细网络。实验将试图把这个系统与已知的含有固定杂质的磁性系统联系起来。对于流体系统，二氧化硅网络起着固定杂质的作用，在没有杂质的情况下，众所周知，磁体和流体密切相关。虽然这是一个非常基础的研究项目，但更深入地了解多孔材料如何影响分层过渡可能会在有机液体污染地下水等情况下有所帮助。***

9617943 Cannell This is a renewal project in which laser light scattering will be used to study the length scale and dynamics of order parameter fluctuations near the critical point of a model system involving isobutyric acid/water mixtures containing a dilute silica network. The critical point of this system lies below (in temperature) a region of metastable domain formation, much as the critical point of a random-field magnet lies below the metastable "frozen-domain" state. Unlike the case with magnets, a simple method of reaching the equilibrium state exists for the fluid mixture. (Leaving the gel containing the mixture in contact with a reservoir of the fluid mixture allows it to reach equilibrium.) This happy coincidence will permit experiments to be carried out on the equilibrium system near the critical point, something which is not feasible for random-field magnets. %%% This is a renewal project in which experiments will be done to study how very dilute porous materials affect certain phase transitions. The phase transition to be studied is the demixing of two liquids, and the porous material will be tenuous network of synthetic quartz (silica). The experiments will try to relate this system to what is already known about magnetic systems containing impurities that are fixed in position. For the fluid system, the silica network plays the role of the fixed impurities, and with no impurities it is already well known that the magnets and fluids are closely related. Although this is a very basic research project, a deeper understanding of how porous materials affect the demixing transition might prove helpful in situations such as contamination of ground water by organic liquids. ***