Preparation and characterization of electroless nickel-coated cellulose fibres
The aim of this project was to fabricate electroless nickel-coated cellulose fibres. Ultimately, these nickel-coated cellulose fibres will be used to develop a cost-effective polymer composite for electromagnetic interference (EMI) shielding and/or electrostatic discharge (ESD) applications. An attempt has been made to impart electrical conductivity onto cellulose fibres via an electroless nickel plating process. The aim was to achieve a homogeneous, continuous layer of Ni on the cellulose fibres, and the plating conditions were optimized to achieve this. The relationship between the coating morphology and the performance of the coated fibre was also of interest. Testing was carried out using cellulose filter paper and then loose cellulose fibres. Scanning electron microscopic (SEM) images of nickel-coated filter paper showed that nickel particles are bonded to the cellulose fibres. The coating appeared more compacted and continuous as plating time increased, corresponding to lower surface resistivity. This observation suggested a correlation between morphology and electrical conductivity of the coating. For nickel-coated cellulose fibres, after optimization of plating conditions, a uniform deposition of nickel particles around the cellulose surfaces was confirmed by SEM images. EDS and XRD results confirmed similar coating could be produced on filter paper and cellulose fibres. SEM images of cross-sectioned nickel-coated cellulose fibres illustrated nickel particles had penetrated into the inner walls of the cellulose fibres. This impregnation of the fibres should act to increase the bonding between nickel coating and cellulose fibres. These nickel-impregnated cellulose fibres could now be incorporated into a polymer matrix to create an electrically conducting composite with the right processing parameters.
Cellulose Mineralization as a Route for Novel Functional Materials
Cellulose possesses excellent properties, but its performance characteristics do not satisfy human requirements completely, which has soured a constant effort to improve its features. Currently, cellulose is combined with inorganics in a process called mineralization that results in a novel type of materials referred to as bio‐nanocomposites. There are many examples of mineralized tissues with superior properties in living nature. This circumstance gives us a reason to biomimic them by compounding biopolymers with inorganics. Here, the main mineralization techniques, properties, structure, functionality, and application of mineralized cellulose are the focus. Cellulose can be combined with inorganics through the vapor phase or by the methods of wet chemistry. Much attention has been paid to sol–gel chemistry, which is of first importance in cellulose mineralization. Inorganics can protect polysaccharides, regulate hydrophilicity–hydrophobicity, and impart self‐cleaning, antimicrobial and conducting properties, which not only improves them but results in bio‐nanocomposites with novel functionalities and performance, not known before for cellulosic materials. Further calcination and carbonization of mineralized cellulose under mild conditions give nanosized metals, metal oxides, and their nanocomposites with carbon, which are often unavailable by conventional methods. Therefore, mineralization is used to develop innovative textiles, oil absorbent and oil/water separating membranes, catalysts and photocatalysts, solar cells, conductors, supercapacitors, transistors and batteries for flexible electronics, and energy storage devices. These nontraditional and highly promising areas for applications have caused an intense interest in cellulose that resembles its rediscovery.
Brushite-collagen composites for bone regeneration.
Brushite-based biomaterials are of special interest in bone regeneration due to their biocompatibility and biodegradability; on the other hand, collagen is a well-known osteoconductive biomaterial. In the present study a new brushite-collagen composite biomaterial is reported. This new biomaterial was prepared by combining citric acid/collagen type I solutions with a brushite cement powder. The obtained biomaterial was a cement paste, with improved handling properties. The effect of collagen on the setting reaction of brushite cement was studied, and was found to speed up the cement setting reaction. The cement paste set into a hard ceramic material within 18.5+/-2.1min and had compressive strength similar to that of spongeous bone (48.9+/-5.9MPa in dry conditions and 12.7+/-1.5MPa in humid conditions). The combination of collagen with citric acid revealed an interesting synergistic effect on the compressive strength of the composite material. Moreover, this new biomaterial had excellent cohesion properties (ninefold better than brushite cement), and high cellular adhesion capacity (threefold higher than brushite cement). The composite biomaterial described in this study combines good handling properties, compressive strength, cohesion and cell adhesion capacity, along with the osteoconductive and biodegradable properties inherent in brushite and in collagen-based biomaterials.