Gražyna Simha Martynková

Preparation of organovermiculites using HDTMA : Structure and sorptive properties using naphthalene

Three types of organovermiculites with various organic cation (HDTMA) loading were prepared to be used as sorptive material for non-ionic organic compounds. The prepared materials were characterized using XRD and TOC analysis. The experiments evolved the fact that lower loading of HDTMA is more acceptable for sorption of neutral organic molecules from aqueous solutions. One of the possible models of intercalated molecules arrangement in vermiculite spacing was proposed.

Modified clay minerals efficiency against chemical and biological warfare agents for civil human protection

Sorption efficiencies of modified montmorillonite and vermiculite of their mono ionic Na and organic HDTMA and HDP forms were studied against chemical and biological warfare agents such as yperite and selected bacterial strains. Yperite interactions with modified clay minerals were observed through its capture in low-density polyethylene foil-modified clay composites by measuring yperite gas permeation with using chemical indication and gas chromatography methods. The antibacterial activities of synthetized organoclays were tested against selected Gram-positive and Gram-negative bacterial species in minimum inhibitory concentration tests. The obtained results showed a positive influence of modified clay minerals on the significant yperite breakthrough-time increase. The most effective material was the polyethylene-Na form montmorillonite, while the polyethylene-Na form vermiculite showed the lowest efficiency. With increasing organic cations loading in the interlayer space the montmorillonite efficiency decreased, and in the case of vermiculite an opposite effect was observed. Generally the modified montmorillonites were more effective than modified vermiculites. The HDP cations seem to be more effective compare to the HDTMA. The antibacterial activity tests confirmed efficiency of all organically modified clay minerals against Gram-positive bacteria. The confirmation of antibacterial activity against Y. pestis, plague bacteria, is the most interesting result of this part of the study.

Vermiculite: Structural Properties and Examples of the Use

The effort to clarify the meanings of the terms ‘clay’, ‘clays’, and ‘clay minerals‘ was the subject of the joint nomenclature committees (JNCs) of the Association Internationale pour l’Etude des Argiles (AIPEA) and the Clay Minerals Society (CMS). The JNCs have proposed the term a class of hydrated phyllosilicates forming the fine-grained fraction of rocks, sediments, and soils and have defined ‘clay’ as ‘‘a naturally occurring material composed primarily of fine-grained minerals, which is generally plastic at appropriate water contents and will harden when dried or fired’’ [1]. According to this definition synthetic clays and clay-like materials are not regarded as clay even though they may be fine grained, and display the attributes of plasticity and hardening on drying and firing.

Preparation and characterization of porous cordierite for potential use in cellular ceramics

Cordierite porous ceramics Z, X, and K were prepared using three mixtures of clay minerals: Z from kaolinite, talc, and aluminum hydroxide, X from kaolinite, talc, vermiculite, and aluminum hydroxide, and K from kaolinite, talc, and magnesium oxide. Ceramics were different in porosity, specific surface area, cordierite polymorphs, and secondary crystalline phases. Vermiculite influenced textural architecture of calcined cordierite ceramics X and predestinated crystallization of the high-temperature hexagonal α-cordierite with secondary minerals enstatite, spinel and corundum. Ceramics Z contained low-temperature orthorhombic β-cordierite, enstatite, and corundum, K was diphase of β-cordierite and forsterite. Total pore area (TPA) and specific surface area (SSA) of X, in spite of the higher porosity and the pore size distribution in the range of 300–1000 nm, were smaller in comparison with TPA and SSA of Z. Ceramics K retained high porosity, two maxima at 300–1000 nm and 50–200 nm in the pores size distribution, and the highest TPA and SSA compared to those observed in ceramics Z and X.

Tuning Carbon Nanotubes Through Poor Metal Addition to Iron Catalysts in CVD

In this contribution we explore the use of poor metals (Al, Ga, In and Pb) and Zn with Fe in the catalytic CVD of carbon nanotubes. The addition of these metals lead to a rich set of changes in the obtained nanotubes. The uses of poor metals are shown to offer benefits in the quality and control in the number of walls of the produced carbon nanotubes. They can improve the quality of single walled carbon nanotubes (Fe/Zn) or be used to tailor the type of resultant tube from high‐yield double‐walled carbon nanotubes (Fe/Al) and to higher order CNT (Fe/Pb) and bamboo CNT (Fe/Ga and Fe/In).

Semimetallic Brake Friction Materials Containing ZrSiO4: Friction Performance and Friction Layers Evaluation

The effect of ZrSiO4 (zircon) content on friction performance and friction surfaces of semimetallic brake friction materials is discussed. The experimental results indicate that the varying content of zircon affects the friction performance as well as plays crucial role in the iron film formation on the friction surfaces. The friction layers, formed during friction process, were carefully characterized using scanning electron microscopy with energy dispersive X-ray microanalysis, and X-ray diffraction methods. The phenomenon of two different types of iron film formation (film I and film II) on the friction surfaces is proposed and their formation and destruction mechanism is described. Despite the compositions of both iron films being similar, film I is formed by steel wool itself and film II by the debris from either disc or steel wool. The relationships among formulation, friction performance, and friction surfaces are summarized.

Decoration of Inorganic Substrates with Metallic Nanoparticles and Their Application as Antimicrobial Agents

Effect on antimicrobial activity observed for several types of hybrid materials is described in our chapter. The substrates for functional antimicrobial particles are natural clay minerals and carbon materials for this review limited to graphite/graphene and carbon nanoparticles (nanotubes and fullerenes). Short description of substrate materials and their properties is followed by discussion of the effect of selected most popular antimicrobial metals (silver, copper) and several oxides (zinc, titanium and copper oxides) and it is conferred for Gram positive and Gram negative bacterial strains. The methods for preparation of such particles may vary but the most used are intercalation and decoration methods from solution for the clay minerals. Nanoparticles (NPs) of metals and metal oxides on carbon and nanocarbon materials are prepared using physico-chemical approach. The research confirmed that the shape and size of functional NPs can depend on used substrate, preparation conditions and used method. Interestingly, it was found that Ag-clay sample was as effective as the free Ag+ions. Generally, it was found the size of active surface area, mobility and availability of potential active particles (ions or nanoparticles) and chemical state of them plays an important role in antimicrobial activity.

Filamentous Carbon Catalytic Deposition of Coal‐Tar Pitch Fraction on Corundum

Abstract Our work was focused on deposition of volatile hydrocarbons of carbonaceous precursor on corundum wafer, taking advantage of a metallic catalyst incorporated in precursor. Coal tar‐pitch, namely a fraction soluble in toluene, served as precursor material for deposition of filamentous material. The toluene‐soluble fraction of tar‐pitch originally contained metallic particles of iron and nickel. During heat treatment up to 1000°C, metallic particles accompanied the volatile hydrocarbons conducive to forming a filamentous deposit. The deposit obtained demonstrates a semicrystalline material that has an irregular filamentous structure with an average filament diameter of 30 µm. The presence of catalysts after the deposition process was proved in the deposit but catalysts were not found in the residuum.

Preparation of calcium-deficient hydroxyapatite particles on vermiculite by precipitation and sonication

Ca-deficient hydroxyapatite (CDH) is biocompatible, cheap material used in implants and non-biological applications. Due to similarity of CDH with human hard tissues, it is suitable for manufacturing of bone substituents. Clay minerals are suitable natural and non-toxic materials used as substrates for the growth of nanoparticles. Combination of non-toxic nature of the clay minerals with CDH is possible to achieve nanocomposites with properties advantageous for medical or catalytic applications. The aim of the study was to prepare CDH on the surface of a monoionic Na/Mg form of original vermiculites (Vs) from Brazil and Bulgaria. The CDH was prepared by precipitation under constant mixing or sonication conditions. XRD analysis confirmed that CDH was successfully prepared on the V surfaces, and the type of V did not influence CDH creation. Basal reflections of vermiculites do not show changes indicating an interaction between vermiculites and CDH. No interactions between V and CDH were observed in FTIR measurement and fitting analysis. Scanning electron microscopy shows creation of CDH particles and coherent layer on the V surface. The results showed that V serves as a support for CDH particles and probably does not influence the chemistry of CDH.

Simulation of Friction Composite Behavior Using Heat Treatment

One of the factors influencing performance of friction composites is stability (optimal condition ) of surface at high temperatures. When measuring coefficient of kinetic friction and volume wear rate, preheating of tiie cast iron disc is used to simulate behaviour in real conditions. Using this method the comparison of different friction composites can be canied out. The heat treatment of selected samples in inert atmosphere was applied to obtain information about tiie bulk material and surface changes at gradually increased temperature. We have observed changes in components morphology and phase composition of bulk material and compared it with structure of surface after friction test. We have focused on characterization of friction modifiers, fibrous fillers and resin binder as well.