Papers by Keyword: Calcium Carbonate Whisker

Abstract: Calcium carbonate whisker is a new kind of environmental-friendly inorganic material. Some advantages of calcium carbonate whisker such as low manufacture cost, simple preparation condition and excellent properties draw a lot of attention and make it higher potential competitive in the market. This review summarizes the research progress of calcium carbonate whiskers prepared with the different methods such as carbonation method, metathesis reaction method, sol-gel method, urea hydrolysis method and gravity crystallization method, and describes the research status in diverse applications of calcium carbonate whisker in enforcement of composite materials, being as filler of paper-making and additives in friction materials.

Abstract: Mechanical grinding method was employed in this study to disperse CaCO3 whiskers in cement matrix. Mechanical properties of the ground whisker reinforced cement were measured. It is shown that the mechanical grinding method was advantageous to the dispersion and mechanical properties of composites. But the grinding process must be proper to assure a certain length and integrality of the whiskers. Crack deflection and whisker pullout mechanisms could account for the strengthening and toughening effects caused by whiskers.

Abstract: CaCO3 whiskers were treated by stearic acid and the surface property of the treated whisker were evaluated by activation index. When the mass fraction of stearic acid was 4.0%, activation exponential increased to 80.0% almost from zero. The composites were prepared by blending with polypropylene and the treated whiskers. The performance of the composites, such as thermal behavior, mechanical properties and microstructure, were analyzed with differential scanning calorimetry, scanning electron microscopy and tensile testing. The results showed that CaCO3 whisker played heterogeneous nucleation to induce crystalline behavior of PP phase in the blends and the crystallization rate of PP phase also increased because of CaCO3 whiskers intervening. Moreover thermo-decomposing temperature and tensile strengths of the blends all increased with increasing whisker content, except a little less than that of pure PP as filling 3.22% CaCO3 whiskers, but the elongation at break increased with increasing whisker content.

Abstract: Strengthening and toughening efficiency contributed by calcium carbonate whisker was questioned in this study when the interfacial bonding strength between whisker and Portland cement was increased by adding silica fume. A simple proving experiment was employed and the basic mechanical properties were measured. The results showed that the compressive strength of the composites with silica fume was more sensitive to whisker loading. The flexural strength, split tensile strength and work of fracture were increased no matter with or without silica fume. However, the strengthening and toughening efficiency caused by whiskers in the composites with silica fume was lower than that without silica fume. The scanning electron microscopy images illustrated six mechanisms which can account for the strengthening and toughening effects. It is concluded that crack deflection was the efficient mechanism to toughen cement composite materials. And the interfacial bonding strength should be weak enough to introduce more crack deflection mechanism.

Abstract: Calcium carbonate (CaCO₃) whiskers were firstly treated by sodium stearate, and then blended with polypropylene (PP) to prepare the composites by a closely intermeshing co-rotating twin-screw extruder at 200°C. The performance of the composites, such as thermal behavior, microstructure and mechanical properties, were analyzed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing. The results showed that CaCO₃ whisker influenced the crystalline behavior of PP phase in the blends because of its intervening. Moreover, thermo-decomposing temperature, tensile and bending strengths of the blends all increased with increasing whisker content. CaCO₃ whiskers had good reinforcing and toughening effects on PP.

Abstract: CaCO3 whiskers were synthesized with soluble phosphates by one-step carbonization method, controlling mechanisms were investigated via XRD and FTIR, and it has been indicated that the most stable calcium phosphates in thermodynamics, hydroxyapatite was formed through the reaction of soluble phosphates and Ca(OH)2 in advance before CO2 was introduced, and then [CO32-(OH)] entered the crystal lattices of hydroxyapatite to replace partially [PO43-] to yield B-carbonate hydroxyapatite in the early stage of blowing CO2, which induced aragonite to heterogeneously nucleate as nucleation center and grew into calcium carbonate whiskers by the continuous stack of Ca2+ and CO32-, while other HA selectly adsorbed onto the flanks of CaCO3 to control crystal morphology.