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首页> 外文会议>IUTAM Symposium on Multiscale Modeling and Characterization of Elastic-Inelastic Behavior of Engineering Materials; 20021020-20021025; Marrakech; MA >EFFECTS OF POLYMERIC ADDITIVES ON THE MORPHOLOGY AND THE STRUCTURE OF CALCIUM CARBONATE MATERIAL
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EFFECTS OF POLYMERIC ADDITIVES ON THE MORPHOLOGY AND THE STRUCTURE OF CALCIUM CARBONATE MATERIAL

机译：高分子添加剂对碳酸钙材料的形貌和结构的影响

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In this work, we investigate the crystallization of calcium carbonate (CaCO_3) from supersaturated solutions and in the presence of polymeric additives such as an anionic polyelectrolyte (polystyrene sulfonate) and a non-ionic copolymer (polystyrene-polyethylene oxide). Depending on the nature and concentration of the additive used, we obtain various calcium carbonate particles having different sizes, crystalline structures, and morphologies. Thus, in the presence of the non-ionic copolymer alone, the mineral crystallization gives birth to CaCO_3 agglomerates of primary particles. The size of the primary particles, which present mostly rhombohedral morphologies, is about 4 μm and the aggregate size is the range 10-20 μm. On the other hand, in the presence of the anionic polyelectrolyte alone, we obtain CaCO_3 crystals having smooth spherical shape and size about 2 μm. However, in the presence of copolymer-polyelectrolyte mixture, the calcium carbonate crystallization gives birth to modified CaCO_3 crystals morphologies. Such morphologies are function of the ratio I, I = C_(copolymer)/C_(polyelectrolyte). The C_(copolymer) and C_(polyelectrolyte), are respectively, the copolymer and the polyelectrolyte concentrations used. Hence, at value of I=2.9, the calcium carbonate crystallization gives rough CaCO_3 spherical having size about 2 μm, while at values of I=3.1 and I=18.6, we observe elongated CaCO_3 particles having size (maximum crystal length) in the range 3.4-4.3 μm. The CaCO_3 crystal structures obtained by the X-ray analyses were pure calcite when the additive is the non-ionic copolymer and pure vaterite in the presence of the anionic polyelectrolyte. The data obtained indicate that the pure polyelectrolyte alone inhibits the crystal growth in all direction and lead to homogenous CaCO_3 spherical particles. However in the presence of the copolymer-polyelectrolyte mixture, the crystal growth seems to be inhibited in preferential directions. This study shows that the morphology and structure of the CaCO_3 crystals can be controlled by the use of either pure or mixture polymer additives. Finally, the effects of the polyelectrolyte and non-ionic copolymer on the precipitation of the CaCO_3 are explained in term of two main mechanisms involving ion exchange and/or ion complexation and preferential adsorption.
机译：在这项工作中，我们研究了碳酸钙（CaCO_3）从过饱和溶液中以及在聚合物添加剂（如阴离子聚电解质（聚苯乙烯磺酸盐）和非离子共聚物（聚苯乙烯-聚环氧乙烷））的存在下的结晶。根据所用添加剂的性质和浓度，我们获得了具有不同尺寸，晶体结构和形态的各种碳酸钙颗粒。因此，在单独存在非离子共聚物的情况下，矿物结晶产生初级颗粒的CaCO 3附聚物。主要呈现菱面体形态的初级颗粒的尺寸约为4μm，聚集体尺寸为10-20μm。另一方面，在单独存在阴离子聚电解质的情况下，我们获得了具有光滑球形和约2μm大小的CaCO_3晶体。然而，在共聚物-聚电解质混合物的存在下，碳酸钙结晶产生了改性的CaCO_3晶体形态。这样的形态是比率I的函数，I ＝ C_（共聚物）/ C_（聚电解质）。 C_（共聚物）和C_（聚电解质）分别是所使用的共聚物和聚电解质的浓度。因此，在I = 2.9的情况下，碳酸钙结晶会生成大小约为2μm的粗糙CaCO_3球形，而在I = 3.1和I = 18.6的情况下，我们会观察到尺寸（最大晶体长度）在该范围内的细长CaCO_3颗粒3.4-4.3微米当添加剂为非离子共聚物时，通过X射线分析获得的CaCO_3晶体结构为纯方解石，在阴离子聚电解质存在下为纯球v石。获得的数据表明，纯聚电解质单独抑制晶体在所有方向上的生长并导致均质的CaCO_3球形颗粒。然而，在共聚物-聚电解质混合物的存在下，晶体生长似乎在优先方向上受到抑制。这项研究表明，可以通过使用纯聚合物添加剂或混合聚合物添加剂来控制CaCO_3晶体的形态和结构。最后，从涉及离子交换和/或离子络合和优先吸附的两个主要机理解释了聚电解质和非离子共聚物对CaCO_3沉淀的影响。

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