The Effect of Carbonation Conditions on the Properties of Carbohydrate-Calcium Carbonate Hybrid Pigments

The influence of two polysaccharides, native corn starch and carboxymethyl cellulose (CMC), on the precipitation of calcium carbonate was examined by utilizing two different carbonation processes. In a batch process, carbon dioxide gas was fed through calcium hydroxide slurry at pH 11.5 to 12.0. The reaction was complete when the pH had been decreased to 7. In a fed-batch reaction, the carbon dioxide was dissolved in water while calcium hydroxide was pumped into the water, maintaining a constant pH of 6.0±0.5. Scanning electron microscopy, particle size analysis, and specific surface area analysis were used to characterize the structure of the precipitated calcium carbonate (PCC) pigments. In application testing, the impact of modified pigments on paper properties was examined. The results showed that carbohydrates can significantly affect the crystallization of calcium carbonate, but the influence depends on the precipitation conditions and the type and concentration of the carbohydrate added. The starch-modified PCC, produced by the fed-batch reaction, improved the mechanical properties of the paper, whereas CMC-modified PCC yielded paper with good surface and optical performance but weakened strength properties

Multidimensional Co-Exfoliated Activated Graphene-Based Carbon Hybrid for Supercapacitor Electrode

Herein, a simple route for the fabrication of highly porous-activated few-layer graphene for application in supercapacitors as an electrode material is reported. The process makes use of natural and renewable materials, which is an essential prerequisite, especially for large-scale application. Few-layer graphene is exfoliated in aqueous suspension with the aid of microfibrillated cellulose (MFC), an environmentally benign eco-friendly medium that is low-cost, biodegradable, and sustainable. The exfoliated product is subsequently activated to increase the surface area and to form the desired pore structure. The prepared electrode materials exhibit a high surface area of up to 720 m2 g−1. MFC is also used as a nontoxic environmentally friendly binder in the electrode application. The electrochemical performance is evaluated in a three-electrode system, and the prepared samples show a high specific capacitance of up to 120 F g−1 at a current density of 1 A g−1. The samples also exhibit a high capacity-retentionrate of about 99% after 5000 cycles and 97% after 10 000 cycles. The proposed method for the fabrication of graphene-based supercapacitor electrode materials, based largely on renewable and sustainable materials, offers potential for commercially viable applications.Peer reviewe

Co-exfoliation and fabrication of graphene based microfibrillated cellulose composites-mechanical and thermal stability and functional conductive properties

The excellent functional properties of graphene and micro-nanofibrillated cellulose (MNFC) offer plenty of possibilities for wide ranging applications in combination as a composite material. In this study, flexible graphene/microfibrillated cellulose (MFC) composite films were prepared by a simple method of co-exfoliation of graphite in an MFC suspension by high-shear exfoliation. We show that pristine graphene, without any chemical treatment, was homogeneously dispersed in the MFC matrix, and the produced composites showed enhanced thermal, electrical and mechanical properties compared to a non-co-exfoliated control. The film properties were studied by XPS, XRD, Raman, SEM, FTIR, TGA, nitrogen sorption, UV-vis spectroscopy, optical and formation analysis tests. At 0.5 wt% loading, the specific surface area of graphene/MFC composites increased from 218 to 273 m2 g-1 while the tensile strength and Young's modulus for the graphene/MFC composites increased by 33% and 28% respectively. Thermal stability was enhanced by 22% at 9 wt% loading and the composites showed a high electrical conductivity of 2.4 S m-1. This simple method for the fabrication of graphene/MFC composites with enhanced controlled functional properties can prove to be industrially beneficial, and is expected to open up a new route for novel potential applications of materials based largely on renewable resources.Peer reviewe

Forming and Dewatering of a Microfibrillated Cellulose Composite Paper

An approach is demonstrated for the manufacturing of a microfibrillated cellulose (MFC) composite paper. A key element in the manufacturing paradigm is the use of high consistency suspensions to improve retention and minimize the need for water removal after forming. The rheological characterization of the composite furnish, which contained 70% structured pigment, 20% MFC, and 10% pulp fibers, revealed a gel-like shear thinning behavior of the suspension, which differs greatly from traditional fiber-based papermaking furnishes. The results from laboratory and pilot scale studies show that the headbox consistency range from 5 to 10% offers the best combination of processing, forming characteristics, retention, and dewatering. While the furnish dewatering in laboratory scale was very problematic, under suitable dynamic conditions the wire section dewatering was excellent. The results of this study suggest that the MFC composite can be manufactured on a modified paper machine and that the final product will have an attractive cost structure