The freezing and melting of water in MCM-41 type ordered mesoporous silica materials with cylindrical pores of uniform size (3-12 nm pore width) was studied by differential scanning calorimetry (DSC). A systematic dependence of the melting point depression ΔT_m on the pore radius R was observed which can be represented by a modified Gibbs-Thomson equation, ΔT_m(R) = K/ (R-t), where t can be taken as the thickness of a surface layer of non-frozen water at the pore wall. The experimental value of K agrees with an estimate of the Gibbs-Thomson constant based on thermodynamic data for the normal melting point of ice. DSC freezing scans on samples with partially filled pores show a peak pattern that depends on the degree of pore filling Φ. The individual peaks are ascribed to different states of the liquid in the pore space, viz. pore water in completely filled regions, and water as an adsorbed film at the pore wall. These two states coexist in a pore filling range Φ_(min) <Φ< 1, but only the film state exists at Φ < Φ_(min). In heating scans only one DSC peak is observed, independent of the pore filling.
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机译：通过差示扫描量热法（DSC）研究了MCM-41型有序介孔二氧化硅材料中的MCM-41型有序的介孔二氧化硅材料的冻结和熔化，具有均匀尺寸的圆柱形孔（3-12nm孔宽）。观察到熔点凹陷Δt_m对孔半径R上的系统依赖性，其可以由修改的gibbs-thomson方程表示，Δt_m（r）= k /（r），其中t可以作为表面的厚度。在孔壁上的非冻水层。 K的实验值同意基于冰正常熔点的热力学数据估计Gibbs-Thomson常数。 DSC冻结样品上的扫描，具有部分填充的孔隙显示峰值图案，其取决于孔隙填充程度φ。单个峰置于孔隙空间中的液体的不同状态，Viz。在完全填充的区域中孔隙水，以及孔壁上的水作为吸附薄膜。这两个状态在孔填充范围φ_（min）<φ<1中共存，但只有胶片状态存在于φ<φ_（min）。在加热扫描中，仅观察到一个DSC峰，与孔填充无关。
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