Physico-chemical characteristics of chemically activated cement containing boron

The use of colemanite ore waste (CW) containing boron as a cement replacement material increases the long-term strength of the concrete. Despite this benefit, the use of CW is limited due to the low-early strength of the CW concrete. The study reported below intended to eliminate this problem. The experimental part comprises two stages: in the first stage the possibility of using CW instead of natural gypsum has been investigated through several tests. In the second stage, a number of chemical activators, namely, sulphonated melamine formaldehyde (SMF) condensates, sulphonated naphthalene formaldehyde (SNF) condensates, _Na2SO4${\mathrm{Na}}_2{\mathrm{SO}}_4$, and calcium chloride were used. The results showed that replacement of natural gypsum by CW results in an acceptable initial and final setting time of cement and increases the compressive strength of the mortar at long term. The addition of chemical activators into the system accelerated pozzolanic reaction and considerably increased early strength of the mortars. The results also indicate that chemical activators not only alter the rate of cement paste hydration, but the microstructure of mortar as well.     

Use of boron wastes in the production of heavy clay ceramics

Colemanite, ulexite and tincal are the main boron ores found in Turkey and account to 63% of the world estimated reserves. The production route of boron products results in significant amounts of different types of Boron Wastes, BW. Their open field disposal raises substantial environmental concerns in fear of leaching and groundwater pollution. The heavy clay ceramic industry can potentially absorb substantial quantities of BW. In the present study, BW produced from Kirka borax plants in Turkey, with 12.6 wt.% B₂O₃ was introduced in 0 wt.%, 5 wt.% and 15 wt.% in a heavy clay body mixture. Four peak temperatures, 800 °C, 850 °C, 900 °C and 950 °C, were examined for the dry pressed samples. The thermal behaviour analyzed by dilatometry and TGA shows that major loss in weight starts about 600 °C and continues to 700 °C approximately. For 5 wt.% BW addition and firing at 900–950 °C, the sintered bodies present comparable or improved physical and mechanical properties with respect to the reference formulation. The microstructure was analyzed by SEM whereas the main crystalline phases were identified by XRD. Samples fired at 900 °C with 5 wt.% BW present comparable properties with the reference ones. At 950 °C, the obtained properties were improved. Deformation occurs for samples with 15 wt.% BW when fired at >900 °C.     

Antimutagenic activities of some foods

There has been a recent increase in research into the possible ways of protecting individuals from cancer by making changes in dietary habits. In this study raw and boiled juice and leaf and dried seeds of Urtica sp, Stachys annula, sage, rosehip, grape molasses and tarhana were not found mutagenic in S typhimurium TA 100. All of the foods decreased sodium azide mutagenicity in S typhimurium TA 100. Among the foods tested, raw Urtica sp (46.32%) and rosehip (44.03%) showed the highest antimutagenic effect followed by leaf of Urtica sp (41.25%), boiled juice of Urtica sp (37.22%), Stachys annula (36.42%), grape molasses (33.03%) and tarhana (28.60%), respectively. The antimutagenic activities of Urtica sp and rosehip were found to be significantly higher than the antimutagenic activity of tarhana (p<0.01). © 1999 Society of Chemical Industry     

Conductivity Study of Polyaniline-Cobalt Ferrite (PANI-CoFe2O4) Nanocomposite

Nano-Micro Letters - In this investigation, the structural and electrical properties of nanocomposites of polyaniline (PANI) and cobalt ferrite synthesized by hydrothermal route are reported for...     

Synthesis,conductivity and dielectric characterization of salicylic acid–Fe3O4 nanocomposite

We report on the synthesis of water dispersible salicylic acid –Fe₃O₄ nanocomposites via a co-precipitation route by using Fe(III) and Fe(II) chloride salts, and salicylic acid. Crystalline phase was identified as Fe₃O₄ and the crystallite size was obtained as 13 ± 6 nm from X-ray line profile fitting. As compared to the particle size of 20 nm obtained from TEM analysis these particles show polycrystalline nature. The capping of salicylic acid around Fe₃O₄ nanoparticles was confirmed by FTIR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface. ac and dc conductivity measurements performed on the nanocomposite revealed semiconductor characteristics and varying trends with temperature due to reorganization of the nanocomposite. Permittivity measurements showed increasing dielectric constant with increasing temperature as expected from semiconductors. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite.     

Setting and hardening of borogypsum-Portland cement clinker-fly ash blends. Studies on effects of molasses on properties of mortar containing borogypsum

The present work describes a study of setting and hardening of blends of borogypsum, fly ash, and Portland cement clinker (PC). The possibility of using borogypsum instead of natural gypsum in fly ash-cement matrix has been investigated through several tests. In addition, the effects of molasses on the setting times of cement and strength of the mortar were also studied. The setting times of the cement were retarded when the natural gypsum was replaced by borogypsum. Molasses exhibited a rather significant retarding effect when used in combination with borogypsum in cement. The inclusion of molasses to the system at a level of 0.1% resulted in a reduction in early strength of the mortar. However, it significantly enhanced the strength of the mortar after 7 days of curing age. In general, the cement prepared with borogypsum was found to have similar strength properties to those obtained with natural gypsum, and inclusion of molasses into the system significantly increased the strength of the sample after 7 days of curing age.     

ZnxCu(1−x)Fe2O4 Nanoferrites by Sol–Gel Auto Combustion Route: Cation Distribution and Microwave Absorption Properties

The effect of Zn doping on magnetic properties and site preference of cations of CuFe₂O₄ has been investigated. Zn substituted Cu ferrite nanoparticles with general formula Zn_xCu_(1?x)Fe₂O₄ were synthesized by a sol–gel auto combustion method. Samples showed fine particle size with very strong aggregation, due to the high temperatures attained during the combustion process. All samples showed high phase purity assessed from X-ray diffraction analysis and do not have magnetization hysteresis, which reveals superparamagnetic character of the fabricated particles. It was found that a certain amount of Zn substitution in Cu ferrite (0.4 < x < 0.6) causes different site occupation of cations. XRD and magnetic hysteresis data of all samples were analyzed and the cation distribution in spinel ferrites was calculated by these two experimental techniques. It was found that the Neel antiferromagnetic aligned sublattice model is valid below this region (x < 0.4), and above it (x > 0.6) the canted spins at octahedral site are dominant according to the tetrahedral site spins.     

Size and surface effects on magnetic properties of Fe3O4 nanoparticles

In this study, size and surface effects on temperature and frequency dependent magnetic properties of superparamagnetic Fe3O4 nanoparticles in a size range of 1.1-11 nm are investigated by SPR technique. We used a theoretical formalism based on a distribution of diameters or volumes of the nanoparticles following lognormal proposed by Berger et al. The nanoparticles are considered as single magnetic domains with random orientations of magnetic moments and thermal fluctuations of anisotropic axes. The individual line shape function is derived from the damped precession equation of Landau-Lifshitz. Magnetic properties of the samples were strongly temperature and size dependent. The increase in SPR line width, the decrease in the resonance field and also increase in anisotropy filed by decreasing the temperature core-shell type structure of the nanoparticles and disordered magnetic structure (spin-glass like phase) of the particle surface. A linear microwave frequency dependence of the resonance field and the increase in the blocking temperature of the particles by the particle size were also observed.