Influence of inorganic pigments on the fluidity of cement mortars

Among the admixtures used for cement composites, an inorganic pigment, which contributes color to the final product, enhances the esthetic value of a building. It can be reasonably assumed that the use of inorganic pigments will increase, given the recent trend to make cities more beautiful with color. The aim of this study was to investigate the effects of inorganic pigments on the fluidity of cement mortar. For this purpose, a flow test was carried out on cement mortar mixed with inorganic pigments by changing the proportion of cement mortar, water-cement ratio, and ratio of pigment. When red and yellow pigment mortars were used, the fluidity rapidly decreased with increasing ratio of pigment. To secure an acceptable workability, the amount of mixing water had to be increased or a superplasticizer employed. When a green pigment mortar was used, however, the fluidity of the mortar recorded −2.4-6.9%, indicating almost no change in flow. When a black pigment mortar was used, the pigment had no effect on fluidity.     

Research on improving the heat insulation and preservation properties of small-size concrete hollow blocks

To solve the problems of poor thermal insulation and heat preservation properties that exist in the walls made of small-size concrete hollow blocks, a new type of compound small-size concrete hollow blocks has been developed. As shown in tests and calculations, the compound blocks not only improve significantly the thermal insulation effect, heat preservation properties, and impermeability of the walls, but also show good decorative results.     

Crystallization and magnetic property of iron oxide nanoparticles precipitated in silica glass matrix

Crystallization and magnetic property of Fe₂O₃ nanoparticle precipitated in SiO₂ matrix was investigated. Fe₂O₃/SiO₂ nanocomposite thin film was obtained by annealing of the amorphous Fe-Si-O thin film deposited by RF-magnetron sputtering of (α-Fe₂O₃)_1−x/(SiO₂)_x composite targets. The Fe₂O₃ crystallite size increased with decreasing SiO₂ area ratio, x of the target and increasing annealing temperature. ?-Fe₂O₃ with the crystallite size of 20-30 nm was obtained after annealing the film deposited in SiO₂ area ratio, x = 0.33-0.42 at 900 °C. Lower SiO₂ area ratio (x) than 0.25 and higher annealing temperature resulted in precipitation of α-Fe₂O₃ with the larger crystallite size than 40 nm. In the case of SiO₂ area ratio, x ≥ 0.50, the annealed film was amorphous and showed higher magnetization and smaller coercivity due to the precipitation of very small crystalline γ-Fe₂O₃. The ?-Fe₂O₃/SiO₂ composite thin film showed ferromagnetic hysteresis with coercive force of 0.14 T.     

Tunable structural and electrical impedance properties of ordered and disordered iron oxide phases for capacitive applications

Having extensive knowledge of room temperature and temperature dependent dielectric and impedance properties of iron oxide nanostructures will help in extending the field of application from biomedical sciences to microelectronics industry. This aspect of iron oxide has long been neglected and the attention is mostly focused on magnetic investigations. To explore and extend the field of application of iron oxide this study is focused on detailed investigation of structural as well as temperature dependent (30–210?°C) dielectric along with impedance analysis. Iron oxide nanostructures are prepared using template free oleic acid assisted sol-gel method with variation in molarity of the finally synthesized sol in the range of 0.2–2.0?mM (interval 0.2?mM). Magnetite (Fe₃O₄) phase is observed at molarity of 0.2?mM whereas, vacancy ordered and disordered maghemite (γ-Fe₂O₃) phases are observed at molarities of 0.8–1.0?mM and 1.4–2.0?mM, respectively. Dielectric constant of 104.6, 74.5 and 98.43 (log f = 5.0) is observed at molarities of 0.2?mM, 1.0?mM and 2.0?mM for Fe₃O₄ and vacancy ordered (V_o) & disordered (V_d) γ-Fe₂O₃ phase, respectively. Zview software is used for the fitting of Nyquist plots. Fitted data reveals that dielectric constant strongly depends on grain boundary resistance (R_gb). Activation energy of 0.25?eV and 0.296?eV (log f = 5) is observed for Fe₃O₄ and V_d γ-Fe₂O₃ phase at 0.2?mM and 2.0?mM molarity of the final iron oxide sol.     

An investigation on room temperature synthesis of vertically oriented arrays of iron oxide nanotubes by anodization of iron

Formation of iron oxide nanotubes on to pure iron substrate by an electrochemical anodization method was investigated in fluoride containing electrolytes. Anodization of iron foil in fluoride containing borate solution resulted in stacked nano-ring type oxide morphology. Nanoporous oxide layer was observed at low pH and a granular oxide layer was formed at higher pH of phosphate + fluoride solutions. Formation of either nanoporous or nanotubular oxide layer was observed in ethylene glycol (EG) solution containing 0.05-0.1 M fluoride + 1.5-3.0 vol.% water. Transition from nanoporous structure to nanotubular structure was critically controlled by anodization potential, water addition and fluoride concentration of the EG solution. The potential required for this transition decreased with increase in the water content up to 7 vol.% beyond which enhanced dissolution occurred. Annealing of the nanotubes at 500 °C resulted in predominantly α-Fe₂O₃ crystal structure. The annealed Fe₂O₃ samples consisting of a single layer of nanotubular structure showed a photo current density of 0.4 mA/cm² at 0.5 V Ag/AgCl in 1 M KOH solution under simulated solar light illumination.     

Kinetic behaviour of iron oxide sorbent in hot gas desulfurization

Although a number of reports on sorbents containing ZnO for H₂S removal from coal-derived gases can be found in the literature, it is shown in our study that a special sorbent containing Fe₂O₃·FeO (SFO) with minor promoters (Al₂O₃, K₂O, and CaO) as the main active species is more attractive for both sulfidation and regeneration stages, also under economic considerations. This paper presents the kinetic behaviour of SFO in a hot gas desulfurization process using a thermogravimetric analysis under isothermal condition in the operating range between 500 and 800 °C. The gas stream was N₂ with a 2% wt of H₂S. Experiences carried out on sorbent sulfidation with SFO (particle sizes in the range of 0.042-0.12 mm) indicate that the sorbent sulfidation capacity sharply increases with temperature in the range of 500-600 °C. It is also shown that the sample weight reaches its maximum absorption capacity, near saturation, at 600 °C so that it makes no sense to increase the sulfidation temperature from this point. To make a comparison between SFO and a zinc titanate based sorbent, a set of sulfidation tests was carried out at 600 °C during 7200 s using the same sieve range for both sorbents between 42 and 90 μm. Results show that the sulfidation capacity of SFO is 1.9 times higher than that of zinc titanate.     

The effect of temperature on the properties of calcined red iron oxide pigments

The effect of calcination temperature on the properties of red iron oxide pigments obtained from FeSO₄, 7H₂O by calcination at constant temperatures over the range from 700 to 900 °C, has been investigated. It was found that the particle diameter increased from 0.065 μm at 700 °C to 0.25 μm at 900 °C; the increase was gradual up to 800 °C and abrupt at 850 and 900 °C. The colour changed from red with decreasing yellowish hue between 700 and 750 °C, to red with increasing bluish hue between 750 and 900 °C; the dominant wavelength increased from 599 nm at 700 °C to 610 nm at 900 °C. The tinting strength was found to vary irregularly with temperature, and to pass through a maximum at 750 °C. The oil absorption was found to decrease with temperature and to be a linear function of the specific surface area.     

A study of the effect of sulphation on iron oxide catalysts for methane oxidation

Sulphated and non-sulphated iron oxides derived from goethite have been compared as methane oxidation catalysts. It has been observed that sulphation increases surface area, suppresses low temperature total oxidation and enhances the formation of partial oxidation products. Characterisation of these materials prior to activity testing demonstrates that, although transformed into haematite, both exhibit a relic morphology related to that of their precursor and that sulphation causes extensive pitting of crystallites. Analysis of powder X-ray diffraction patterns indicates that the relic morphology is multidomainic and that sulphation increases line widths in relation to the non-sulphated system. The post-reactor sulphated samples were found to have lost crystallinity and both catalysts had changed phase from haematite to maghemite.     

Study on steel furnace slags with high MgO as additive in Portland cement

In this study, usability of Basic Oxygen Process (BOP) slags of Kardemir Iron and Steel Plant, Karabük, Turkey as an additive into cement was investigated. Slags were ground to 4000 and 4700 cm²/g levels, and added in ratios 15, 30 and 45 wt.%. Volume expansion, setting time, compressive strength and bending strength tests were measured according to Turkish standards. Due to impurities of the slags, the 2- and 7-day compression strengths decrease with increase in amount of Mn, but this decrease is lower in the 28-day compression strength, 30 wt.%. It is observed that the physical and mechanical properties of the resulting concrete were acceptable in the Turkish Standards Institute (TSE).     

Influence of catalyst pretreatments on volatile organic compounds oxidation over gold/iron oxide

This paper reports a study on the influence of calcination pretreatments on the catalytic behaviour of the Au/iron oxide system towards the combustion of some representative volatile organic compounds (2-propanol, ethanol, methanol, acetone and toluene). The catalytic activity of Au/Fe₂O₃ samples towards the total oxidation to CO₂ has been found to be strongly dependent on the catalyst pretreatment, decreasing on increasing the calcination temperature. On the basis of characterisation data (XPS, FT-IR, XRD, BET surface area) it has been proposed that the catalytic behaviour is related to the gold state and/or the iron oxide phase. It appears plausible to suggest that the gold oxidation state and/or the particle size play a key role in the catalytic combustion of volatile organic compounds.     

Fischer–Tropsch synthesis. Conversion of alcohols over iron oxide and iron carbide catalysts

Both iron oxide (Fe₂O₃) and iron carbide catalysts are active for the dehydration of tertiary alcohols; the oxide catalyst is not reduced nor is the bulk carbide oxidized by the steam generated during the dehydration reaction. Secondary alcohols are selectively converted to ketones plus hydrogen by both the iron oxide and carbide catalyst. Fe₂O₃ is reduced to Fe₃O₄ during the conversion of secondary alcohols. Both iron carbide and oxide catalysts dehydrogenate a primary alcohol (C_n) to an aldehyde which undergoes a secondary ketonization reaction to produce a symmetrical ketone with 2n−1 carbons. These results plus those of our earlier ¹⁴C-tracer studies suggest that dehydration of alcohols to produce olefins makes a minor, if any, contribution during Fischer–Tropsch synthesis with an iron catalyst at low and intermediate pressure conditions.     

Composite magnetic particles: 2. Encapsulation of iron oxide by surfactant-free emulsion polymerization

This is a second paper in the series concerning the synthesis and characterization of composite polymeric particles with encapsulated magnetic iron oxide and bearing reactive β-diketone groups on the surface. Composite particles have been prepared by two-step method in which first step requires preparation of the iron oxide nano-particles and during second step iron oxide was encapsulated into formed poly(styrene/acetoacetoxyethyl methacrylate) (PS-AAEM) particles directly during polymerization process. It has been found that the modification of the iron oxide nano-particle surface with sodium oleate improves significantly the encapsulation during polymerization process. This procedure gives a possibility to obtain composite particles with raspberry morphology and both the particle size and iron oxide content can be varied. Change of monomer to iron oxide ratio gives a possibility to change effectively the morphology of hybrid particles, however, polydispersity of composite particles increases at higher content of magnetic particles in the system. Variation of AAEM concentration in reaction mixture at constant iron oxide particles concentration gives a possibility to control the particle size of formed hybrid microspheres. Composite particles were characterized by dynamic light scattering and electron microscopy (SEM) with respect to their particle size and morphology of the surface layer. X-ray diffraction (XRD) and magnetization measurements indicate presence of maghemite (γ-Fe₂O₃) in composite particles.     

Effect of high temperature or fire on heavy weight concrete properties

Temperature plays an important role in the use of concrete for shielding nuclear reactors. In the present work, the effect of different durations (1, 2 and 3 h) of high temperatures (250, 500, 750 and 950 °C) on the physical, mechanical and radiation properties of heavy concrete was studied. The effect of fire fitting systems on concrete properties was investigated. Results showed that ilmenite concrete had the highest density, modulus of elasticity and lowest absorption percent, and it had also higher values of compressive, tensile, bending and bonding strengths than gravel or baryte concrete. Ilmenite concrete showed the highest attenuation of transmitted gamma rays. Firing (heating) exposure time was inversely proportional to mechanical properties of all types of concrete. Ilmenite concrete was more resistant to elevated temperature. Foam or air proved to be better than water as a cooling system in concrete structure exposed to high temperature because water leads to a big damage in concrete properties.     

Influence of crystal size of Yellow 13-type pigments on optical and rheological properties of lithographic inks

Use of a modern diffractometer and detailed knowledge of the crystal lattice structure have improved ability to size crystals of CI Pigment Yellow 13-type pigments. This has enabled confirmation and refinement of correlations observed in earlier work between crystal sizes and optical and rheological properties of commercially available pigments in lithographic inks. The correlations indicate that the dispersion procedures used have produced inks in which the pigments exist substantially as individually dispersed crystals. The correlations also indicate that the crystals of the commercially available pigments are effectively perfect. An alternative explanation on the basis that the various pigments have similar degrees of aggregation and imperfection of crystals is also possible, but improbable due to the widely different compositions and sources of the pigments. Whether or not abietyl resin added to improve dispersibility of pigment remains on the crystal surfaces in inks has not been resolved.     

Influence of ZnO buffer layer thickness on the electrical and optical properties of indium zinc oxide thin films deposited on PET substrates

The influence of the ZnO buffer layer thickness on the electrical and optical properties of In₂O₃–10 wt.% ZnO and ZnO bilayers deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering were investigated. The optimum ZnO buffer layer thickness was found to be 90 nm which gives the lowest electrical resistivity of the bilayer of IZO and ZnO deposited on the PET substrate. The surface roughness decreases and diffusion of moisture and gas is more efficiently restrained, which contributes to lower the resistivity of the bilayer as the ZnO buffer layer thickness is increased. On the other hand, the total resistivity of the bilayer increases as the ZnO buffer layer thickness is increased because the resistivity of ZnO is higher than that of IZO. Introduction of a ZnO buffer layer does not nearly affect the IZO/ZnO/PET sample.     

Influence of surface oxide layer of SiC powder on the rheological properties of its slurry

In this paper, the influence of surface oxide layer of SiC powder on the rheological behavior of its slurry was studied by acid washing, HF etching, and calcination oxidation processes. Zeta potential, particle size, inductively coupled plasma atomic emission spectrometry (ICP-AES), energy dispersive X-ray spectroscopy, and viscosity tests indicated the main factor that resulted in high viscosity of slurry is impure ions existing either on the powder surface or in the water phase, rather than the surface oxide layer. After the impure ions are removed, the surface oxide layer formed at a calcination temperature range of 400°C-750°C does not cause an increase in the slurry viscosity, but contributes to an improvement in the rheological properties of SiC slurry.     

Effect of iron oxide nanoparticles on the morphological properties of isotactic polypropylene

Isotactic polypropylene (iPP) and iron oxide (Fe₃O₄) nanocomposites were mixed by masterbatch blending technique in a single screw extruder machine. The concentrations of Fe₃O₄ in the iPP/Fe₃O₄ nanocomposites were 0.5, 1, 2, and 5% by weight. The influence of Fe₃O₄ nanoparticles on the effectiveness of nucleation, morphology, mode of crystallization, and crystallinity of iPP were studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The introduction of Fe₃O₄ nanoparticles in the iPP matrix inhibited the formation of β crystals, and caused a shift in the melting point to higher values. The magnitude of the shift was up to 20–21°C which indicates that using the masterbatch technique leads to an enhancement of the dispersion process of the Fe₃O₄ nanoparticle and the formation of less agglomerates in the iPP/Fe₃O₄ nanocomposites. The percentage crystallinity, X_c, increased at the low cooling rates of 1 and 2°C/min. At higher cooling rates of 5, 10, and 20°C/min, the masterbatch technique produced nanocomposites of X_c with nonuniform trends. The overall crystallization rate enhancement for the iPP/Fe₃O₄ nanocomposites is attributed to the presence of Fe₃O₄ nanoparticles as a nucleating agent which have no significant effect on the growth rate of iPP crystals. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010