Jonjaua Ranogajec

Thermal and photocatalytic behavior of Ti/LDH nanocomposites

The development of nanocomposite photocatalyst based on layered double hydroxides (LDHs) associated with TiO2 was the subject of this research. The thermally activated Zn–Al LDHs were selected as catalyst support precursor because of their proven photocatalytic activity and therefore their possible contribution to overall activity of novel Ti–Zn–Al nanocomposite. The catalyst precursor (Zn–Al LDH) was synthesized by low supersaturation coprecipitation method, and its association with active TiO2 component targeting the formation of novel Ti–Zn–Al nanocomposite was achieved by wet impregnation. Simultaneous thermal analysis (TG–DTA) was used to investigate the thermal behavior of Zn–Al LDH and Ti–Zn–Al LDHs. Complementary, morphology, texture, and structure characterization was carried out. The photocatalytic test reaction was performed under UV light using the methylene blue degradation. The results confirmed a successful impregnation of TiO2 on catalyst support precursor Zn–Al–LDH followed by considerable change in morphology and structure of Zn–Al LDH precursor. It was concluded that the synergic effect between TiO2 and Zn–Al LDH precursor contributes to the overall photocatalytic activity.

Design of self-cleaning TiO2 coating on clay roofing tiles

The phenomenon of heterogeneous photocatalysis takes place in the degradation process of many organic contaminants on solid surfaces. Photocatalysis is based on the excitation of the semiconductor by irradiation with supraband gap photons and the migration of electron-hole pairs to the surface of the photocatalysts, leading to the reaction of the holes with adsorbed H2O and OH− to form hydroxyl radicals. Due to the stability and photosensitivity of TiO2 semiconductors, this system is well studied and is of great interest from an ecological and industrial point of view for use in the field of building materials. Clay roofing tiles, due to their long-term exploitation, are subject to physical, chemical and biological degradation that leads to deterioration. Ceramic systems have a high percentage of total porosity and considering their non-tolerance of organic coating, the use of surface active materials (SAM) that induce porosity in TiO2 coatings is of vital significance. Photocatalytic coatings applied on clay roofing tiles under industrial conditions were designed by varying the quantity of TiO2 (mass/cm2) on the tile surface (thin and thick TiO2 layer). The positive changes in specific surface area and mesopore structure of the designed coatings were made by the addition of PEG 600 as a surface active material. It was shown that a thin photocatalytic layer (0.399 mg suspension/cm2 tile surface), applied onto ceramic tiles under industrial conditions, had better photocatalytic activity in methylene blue decomposition, hydrophilicity and antimicrobial activity than a thick photocatalytic coating (0.885 mg suspension/cm2).

Portland Ash Cement Degradation in Ammonium-Sulfate Solution

Abstract This paper considers the sulphate corrosion of Portland cements (C 3 A content in clinker 6.60% and 13.31%) and the same Portland cements where the 30% of Portland cement clinker was replaced with coal ash. The test samples were prepared according to Koch-Steinegger’s method and then exposed to the influence of aggressive environment (10% (NH 4 ) 2 SO 4 solution). The measurements of several properties were carried out, the results were analyzed, and a correlation among the influencing factors was suggested through mass change, bonded SO 4 2− content, and degradation coefficient. There was a strong influence of coal ash on degradation, also.

Particle size range as a factor influencing compressibility of ceramic powder

The paper reports on an investigation conducted with the aim to determine whether an overall deformation stress of ceramic powder depends on the size of particles present in a system. For this purpose, six fractions (obtained by sieving of raw material, so as to contain particles with defined size range) were compacted and their compaction response diagrams were generated. For each particular fraction the parameters of the Heckel compaction model were calculated and used for estimating the deformation stress of each particular fraction. A correlation between average diameter of particles and the overall deformation stress of powder was found.

Microbial Deterioration Of Clay Roofing Tiles

The study illustrates both the biodeterioration and biomineralization actions of two fungus species (Aspergillus niger and Cladosporium sp.) and two organic acids (oxalic and acetic) and the action of the frost (frost dilatation studies in laboratory conditions) as the main factors of the process of ageing of clay roofing tiles. The nano-crystalline products, formed in this way, contribute to the abundant reactive surface area of the existing and new filled pores (due to the fungus hyphen penetration into the ceramic support) deepening the ageing processes of the clay roofing tiles. A relationship between the textural and microstructural characteristics of the studied systems and the formation of the specific crystal forms, developed after the actions of fungus, and oxalic/acetic acids was set up.

Compaction mechanism as the function of atomized powder particle size

The cold compaction process of spray dried powder for ceramic floor/wall tiles production was followed by compaction response and compaction rate diagrams. Seven fractions of defined size, as well as the industrial powder batch, were compacted at pressures up to 31.5 MPa. The effect of particle size, textural and morphological characteristics on the consolidation mechanism was investigated. Both plastic deformation and brittle fracture were identified, the dominating mechanism in a given pressure range being the direct function of the size and morphology characteristics of the particles.

Chemical corrosion phenomena of roofing tiles

Abstract The deterioration phenomena of roof tiles in model systems, formed from clay minerals and Ca-carbonate component, have been investigated. The systems after a specific thermal treatment were exposed to real atmospheric conditions, i.e. to attack of sulphurous acidic rains. The dual action, of SO 2 and atmospheric humidity, on roofing tiles, supporting the destruction phenomena of samples, elucidated the formation of specific phases: gel of calcium silicate hydrates and crystals of aluminate hydrates, cancrinite, scawtite and zeolites.

Nanocomposite photocatalyst based on layered double hydroxides (LDHs) associated with TiO2

The surfaces of building materials are constantly exposed to the actions of environmental factors, pollutants of inorganic and organic origin as well as to microorganisms, which significantly contribute to corrosion phenomena.The application of coatings decreases the negative action of the pollutants minimizing their direct contact with the substrate. Different types of coatings with additional functions have been developed. A specific problem of these applications is the lack of compatibility of the photocatalysts with the surface of the building materials and the detachment of potentially toxic TiO2 nanoparticles. In the present study, this problem was solved by the proper immobilization of TiO2 nanoparticles onto the photocatalyst support, layered double hydroxides (LDHs). The newly formed coating possesses acceptable porosity for a porous building material (porosity within the range of 30-46 %) and satisfied photocatalytic activity, as well as mineralogical compatibility with the substrates (mortars, renders, bricks). Additionally, a positive effect considering the self-cleaning phenomenon was attained.

An optimization of fly ash quantity in cement blending

Abstract The Two Goal Approach was applied to the maximization of fly ash quantity (i.e. minimization of energy consumption) in producing cement of acceptable mechanical characteristics. Mathematical model of the optimization problem consists of two objective functions; a requirement concerning ash quantity and a condition upon particular mechanical property. All data were obtained by a kind of the Mixture Design experiments, i.e. mixtures were made, by blending of various quantities of usually used components with fly ash, and their characteristics were determined by the standardized methods. The procedure was applied to a few chosen examples and optimal quantities of fly ash were suggested.

Preliminary evaluation of galvanic sludge immobilization in clay-based matrix as an environmentally safe process.

This study attempts to determine the possibilities and limitations of the immobilization of galvanic wastes by their incorporation into clay-based materials. It focuses on the effects of several processing parameters such as the temperature of thermal treatment, the relative amount of sludge, and the physico-chemical aspects of the sample, on the fixing level of relevant metals (Zn, Ni, Fe, Mn, Pb, Cu, Cr) in thermally treated clay-based samples. The effectiveness of sludge inactivation was assessed by water-leaching test and conductivity measurements. In view of the potential use of the sludge stabilization products as construction materials, the linear shrinkage and bending strain of the fired samples was investigated. To characterize their morphology, mineralogy and composition, fired samples of clay and its mixtures with galvanic sludge were studied on a scanning electron microscope (SEM) coupled with an energy dispersive X-ray analyser (EDS) and X-ray diffractometer (XRD). It was found that the efficiency of metal immobilization is dependent on the clay composition and the temperature of the thermal treatment of the prepared mixtures. The thermal treatment of all samples at all temperatures resulted in the stabilization of all heavy metal ions (copper, nickel, iron, lead, manganese and zinc) with the exception of chromium.