Stanislaw Blazewicz

Bioactive Polymer/Hydroxyapatite (Nano)composites for Bone Tissue Regeneration

Bioactive polymer/hydroxyapatite (nano)composites are currently being intensively investigated as materials for promotion of bone tissue regeneration and reconstruction. The advantages of polymeric biomaterials, compared to metallic or ceramic materials, are the ease of manufacturing components having various and complex shapes, reasonable cost, and their ability to possess a wide range of physical and mechanical properties. Additionally, hydroxyapatite (HAp) is one of the most attractive materials for bone implants because of its composition and biological similarity to natural tissues. It can be obtained in a nanostructured form, which facilitates its fine dispersion in the polymer matrix as well as producing advantageous interactions with bioactive polymer and tissue. This paper reviews recent advances in polymer/(nano)HAp composites and nanocomposites for bone tissue regeneration, with particular emphasis on the material characteristics. Specific topics associated with polymer/HAp composition, molecular orientation and morphology, surface modifications, the interactions between the components, and their biological behaviours are described. Finally, the challenges facing this emerging field of research are outlined.

Some observations on carbon nanotubes susceptibility to cell phagocytosis

The aim of this study was to assess the influence of different types of carbon nanotubes (CNTs) on cell phagocytosis. Three kinds of carbon nanotubes: single-walled carbon nanohorns (SWCNHs), multiwalled carbon nanotubes (MWCNTs), and ultralong single-walled carbon nanotubes (ULSWCNTs) before and after additional chemical functionalization were seeded with macrophage cell culture. Prior to biological testing, the CNTs were subjected to dispersion process with the use of phosphate buffered solution (PBS) and PBS containing surfactant (Tween 20) or dimethyl sulfoxide (DMSO). The results indicate that the cells interaction with an individual nanotube is entirely different as compared to CNTs in the form of aggregate. The presence of the surfactant favors the CNTs dispersion in culture media and facilitates phagocytosis process, while it has disadvantageous influence on cells morphology. The cells phagocytosis is a more effective for MWCNTs and SWCNHs after their chemical functionalization. Moreover, these nanotubes were well dispersed in culture media without using DMSO or surfactant. The functionalized carbon nanotubes were easily dispersed in pure PBS and seeded with cells.

Preparation and characterization of nanofibrous polymer scaffolds for cartilage tissue engineering

Polymer substrates obtained from poly(lactic acid) (PLA) nanofibres modified with carbon nanotubes (CNTs) and gelatin (GEL) for cartilage tissue engineering are studied. The work presents the results of physical, mechanical, and biological assessment. The hybrid structure of PLA and gelatine nanofibres, carbon nanotubes - (CNTs-) modified PLA nanofibres, and pure PLA-based nanofibres was manufactured in the form of fibrous membranes. The fibrous samples with different microstructures were obtained by electrospinning method. Microstructure, physical and mechanical properties of samples made from pure PLA nanofibres, CNTs-, and gelatin-modified PLA-nanofibres were studied. The scaffolds were also tested in vitro in cell culture of human chondrocytes collected from patients. To assess the influence of the nanofibrous scaffolds upon chondrocytes, tests for cytotoxicity and genotoxicity were performed. The work reveals that the nanofibrous structures studied were neither genotoxic nor cytotoxic, and their microstructure, physical and mechanical properties create promising scaffolds for potential use in cartilage repairing.

Influence of high-temperature treatment of granular activated carbon on its structure and electrochemical behavior in aqueous electrolyte solution

Activated carbon Norit R3-ex (demineralized) was annealed at various temperatures (950–2700 °C) in an argon atmosphere. The changes of the porosity of the products were characterized on the basis of N 2 adsorption isotherms (at 77 K). The texture of the samples was investigated by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The presence of surface oxygen (Fourier transform infrared) and its content in the surface layer (from energy dispersive spectroscopy) were determined. The electrical resistivity of powdered samples was measured. Cyclovoltammetry of carbon (powdered electrodes) were carried out and the electrical double-layer capacitances were estimated from the cyclic voltammetry curves. Heat treatment increased the degree of crystallization of the samples, which was correlated with changes in their conductivity. A rapid drop in porosity (at 1800–2100 °C) took place in parallel with a decrease in the electrical double layer capacity. The presence of surface oxygen as a result of oxygen chemisorption on freshly annealed carbon samples was confirmed using several methods.

The effects of the thermal treatment of activated carbon on the phenols adsorption

The adsorptive properties of thermally treated activated carbon at 1,500 and 1,800 °C were investigated. The adsorption kinetics and adsorption efficiency of phenol, 4-chlorophenol and 2,4-dichlorophenol from aqueous solutions were examined. The adsorption kinetic data were analyzed using the pseudo-first and pseudo-second order models, while the equilibrium adsorption data were described by the Langmuir and Freundlich isotherms. The adsorption rate and efficiency increased in the order: phenol<4-chlorophenol<2,4-dichlorophenol. The activated carbons were also used for the modification of the carbon paste electrodes for the detection of the phenols based on the differential pulse voltammetry. Compared to the non-modified electrode, all the new paste electrodes showed a significantly greater sensitivity for the detection of the phenols. The signal response was closely related to the porosity of the materials used, and increased with an increase in the adsorption ability and the specific surface area of the modifiers.

Study of the Carbonization and Graphitization of Coal Tar Pitch Modified with SiC Nanoparticles

Silicon carbide nanoparticles (nSiC) have been used to modify coal tar pitch (CTP) as a carbon binder. The influence of ceramic nanoparticles on the structure and microstructure was studied. The structure of CTP-based carbon residue with various nSiC contents was analyzed by using SEM with EDAX, Raman spectroscopy, and X-ray diffraction. The effect of ceramic nanofiller on the crystallite sizes (, ) and the -axis spacing () in carbonized samples after heating from 1000 to 2800°C was analyzed. Ceramic nanofillers inhibit structural changes in carbonized samples heated to 1000°C. After heating CTP with nSiC above 2000°C, the carbon samples contained two carbon components differing in structural ordering. Ceramic nanoparticles increase carbon crystallite growth, while their impact on the -axis spacing is low.

Mechanical and thermal properties of carbon-nanotube-reinforced self-healing polyurethanes

AbstractThe study was conducted to synthesize self-healing polyurethanes (PUs) in the presence of multiwalled carbon nanotubes (CNTs). Measurements of the self-healing ability of PUs synthesized from N3300 isocyanate and polytetrahydrofuran with various contents of CNTs were taken. The mechanical and thermal properties were studied to analyse healing efficiency in experimentally damaged composite samples. The addition of CNTs results in a slight decrease in the self-healing efficiency of nanocomposites as compared to pure PUs. PU samples containing 40% content of soft segments self-healed much better than the samples with 50% content of soft segments. Functionalized carbon nanotubes CNT-OH due to presence of surface functional groups interact with PU chains, which results in an increase in the healing efficiency of mechanical strength and thermal conductivity of nanocomposites.

Mechanical properties of C/C composites processed by wet impregnation and P-CVI methods

Wet impregnation with phenolic resin and P-CVI methods were used to manufacture C/C composites. The influence of impregnation process of porous 2D carbon fibre substrate with resin and pyrocarbon deposited by CVD technique on mechanical properties of formed composites was studied. The results indicate that using P-CVI method large pores remain in the matrix resulting in lower mechanical strength. This fraction does not undergo any changes during thermal treatment. The flexural modulus of C/C composites depends mainly on the type of reinforcing fibres. The values of moduli measured in composites obtained by both methods do not differ significantly. Comparison of two methods of fabrication of C/C composite show that much better strengths can be achieved by forming the carbon matrix in solid state.

Wood-Derived Tar as a Carbon Binder Precursor for Carbon and Graphite Technology

In addition to the many benefits of coal tar pitch, these materials are known to contain polycyclic aromatic hydrocarbons. For this reason, studies are being developed to elaborate new, ecologically friendly, alternative binders for carbon–graphite technology. This article presents the results of wood tar recovered during thermal degradation of selected types of woods as alternative binders in the manufacture of carbon materials. Two kinds of wood tars obtained from different raw materials were analyzed. Sawdust thermal conversion makes it possible to obtain carbon binders with a lower coking value and quinoline-insoluble matters in comparison to coal tar pitch. These binders produce significantly reduced emissions of polycyclic aromatic hydrocarbons in carbon–graphite technology. Carbon samples manufactured using wood-derived binders with carbon fillers showed similar density and mechanical compression strength values compared to those based on conventional coal tar pitch binders.

Organosilicon resin-based carbon/ceramic polygranular composites with improved oxidation resistance

We examined the thermo-mechanical properties of carbon materials modified with silicon oxycarbide (Si-O-C) and silicon carbide (Si-C). These compounds were obtained by the impregnation of carbon components with a silicon-containing polymer resin. Graphite and anthracite powders were used as carbon components, and poly[methyl(phenyl) siloxane] resin (P) was used as the ceramic precursor. Carbon/polymer compositions (C/P) were subjected to two-stage annealing, first to 1,000 °C and next to 2,000 °C in an inert atmosphere, leading to the formation of C/Si-O-C and C/Si-C composite samples, respectively. The materials were then examined under conditions of isothermal oxidation to determine their oxidation resistance and the mechanical properties before and after oxidation tests. The structure of the samples before and after oxidation was studied. C/Si-C composites, despite their high porosity, proved to have enhanced resistance to oxidation at 600 °C, although they had lower mechanical properties in comparison to C/Si-O-C samples.