Floral-like microarchitectures of cobalt iron cyclotetraphosphate obtained by solid state synthesis

Floral-like microparticle of a binary cobalt iron cyclotetraphosphate CoFeP₄O₁₂ was synthesized through solid phase reaction using cobalt carbonate, iron metal and phosphoric acid with further calcinations at the temperature of 500 °C. The XRD and FTIR results indicate that the prepared CoFeP₄O₁₂ has a pure monoclinic phase without the presence of any phase impurities. The floral-like microparticle and superparamagnetic behavior of the synthesized CoFeP₄O₁₂ are important properties for specific applications, which were revealed by SEM and VSM techniques, respectively. The dominant features of the synthesized CoFeP₄O₁₂ in this work are compared with M₂P₄O₁₂ (M = Co and Fe) and CoFeP₄O₁₂ reported in our previous works.     

Synthesis of potassium niobate (KNbO3) nano-powder by a modified solid-state reaction

Crystalline lead-free piezoelectric potassium niobate (KNbO₃) powders have been synthesized through a modified solid-state reaction method. The thermal behavior of the K₂C₂O₄·H₂O and Nb₂O₅ raw material mixture was investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The X-ray diffraction technique (XRD) was used to investigate the phase formation and purity. The morphology of the powder obtained was characterized using a scanning electron microscope (SEM). The XRD pattern showed that the monophasic perovskite phase of KNbO₃ could be synthesized successfully at a temperature as low as 550 °C for 240 min, with an average crystallite size of 36 ± 8 nm. The SEM images suggested that the average particle size of the powder obtained was 278 ± 75 nm.     

Non-occupational lead and cadmium exposure of adult women in Bangkok, Thailand

This survey was conducted to examine the extent of the exposure of Bangkok citizens to lead (Pb) and cadmium (Cd), and to evaluate the role of rice as the source of these heavy metals. In practice, 52 non-smoking adult women in an institution in the vicinity of Bangkok, volunteered to offer blood, spot urine, boiled rice and 24-h total food duplicate samples. Samples were wet-ashed, and then analyzed for Pb and Cd by ICP-MS. Geometric means for the levels in blood (Pb-B and Cd-B) and urine (Pb-U and Cd-U as corrected for creatinine concentration), and also for dietary intake (Pb-F and Cd-F) were 32.3 micrograms/l for Pb-B, 0.41 microgram/l for Cd-B, 2.06 micrograms/g creatinine for Pb-U, 1.40 micrograms/g creatinine for Cd-U, 15.1 micrograms/day for Pb-F and 7.1 micrograms/day for Cd-F. Rice contributed 30% and 4% of dietary Cd and Pb burden, respectively. When compared with the counterpart values obtained in four neighboring cities in southeast Asia (i.e. Nanning, Tainan, Manila, and Kuala Lumpur), dietary Pb burden of the women in Bangkok was middle in the order among the values for the five cities. Pb level in the blood was the lowest of the levels among the five cities and Pb in urine was also among the low group. This apparent discrepancy in the order between Pb-B (i.e. the fifth) and Pb-F (the third) might be attributable to recent reduction of Pb levels in the atmosphere in Bangkok. Regarding Cd exposure, Cd levels in blood and urine as well as dietary Cd burden of Bangkok women were either the lowest or the next lowest among those in the five cities.     

Solid-state reaction synthesis of sodium niobate (NaNbO<Subscript>3</Subscript>) powder at low temperature

A modified solid-state reaction was applied to produce lead-free piezoelectric sodium niobate (NaNbO₃) powders. The mixture of Na₂C₂O₄ and Nb₂O₅ was identified by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The powders were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The SEM image suggested that the particle size of the powders obtained ranged from 180 to 360 nm. The XRD pattern showed that the pure perovskite phase of NaNbO₃ could be synthesized at the low temperature of 475 °C for 1 h, with an average crystallite size of 31.45 ± 5.28 nm. This temperature was about 300 °C lower than that when using the conventional solid-state method with Na₂CO₃ as reactant, which resulted in a cost-, energy-, and time-saving method.     

Synthesis and ferromagnetic property of new binary copper iron pyrophosphate CuFeP2O7

The pyrophosphate of CuFeP₂O₇ was synthesized through one step-thermal synthesis at 500 °C using the mixing of copper carbonate, iron metals and phosphoric acid. FTIR and XRD results indicate the dominant feature of pyrophosphate (P₂O₇⁴⁻) anion and a pure monoclinic phase with space group C_2h⁶ (Z = 4), respectively. The crystallite size of 25 ± 9 nm for the CuFeP₂O₇ was estimated by X-ray line broadening. Room temperature magnetization result shows ferromagnetic behavior of the CuFeP₂O₇ powder, having hysteresis loop in the range of ± 10,000 Oe with the specific magnetization value of 1.57 emu g^− 1. This property is important for specific application and is presented for the first time.     

Kinetics of Thermal Transformation of Mg<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 8H<Subscript>2</Subscript>O to Mg<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The kinetics of thermal dehydration of Mg₃(PO₄)₂ · 8H₂O was investigated using thermogravimetry at four different heating rates. The activation energies of the dehydration step of Mg₃(PO₄)₂ · 8H₂O were calculated through the isoconversional Ozawa and Kissinger-Akahira-Sunose (KAS) methods and iterative methods, which were found to be consistent and indicate a single mechanism. The possible conversion function of the dehydration reaction for Mg₃(PO₄)₂ · 8H₂O has been estimated through the Coats and Redfern integral equation, and a better kinetic model such as random nucleation of the “Avrami–Erofeev equation (A _3/2 model)” was found. The thermodynamic functions (ΔH*, ΔG*, and ΔS*) of the dehydration reaction are calculated by the activated complex theory and indicate that it is a non-spontaneous process when the introduction of heat is not connected.     

Dietary assessment of refugees living in camps: a case study of Mae La Camp, Thailand

This study presents data on consumption patterns, methods of food procurement, and adequacy of dietary intake among Burmese refugee camp households living along Thailand's border with Burma. Households established for one or more years and with children under 15 years of age were sampled. A questionnaire was used to determine economic, food-consumption, and dietary intake patterns; foods consumed were weighed and measured using a 24-hour recall for the household unit; and nutritional status was determined by a Microtoise tape and digital standing scales. In total, 182 households containing 1,159 people were surveyed. The average household energy and protein intakes were 96.6% and 111.4%, respectively, of the recommended daily allowance (RDA) for healthy Thais. Twelve percent of protein was derived from animal sources. Carbohydrate, protein, and fat accounted for 84%, 9%, and 7% of total energy, respectively. The intake of vitamins A, B1, B2, and C and of calcium ranged from 24.2% to 53.1% of the RDA. Iron intake was 85.3% of the RDA, derived mainly from rice, fermented fish, mung beans, green leafy vegetables, and eggs. Ration foods supplied 60.5% to 98.18% of all nutrients consumed in the households, with the exception of vitamins A and C. Among children under five years of age, 33.7% were underweight, 36.4% were studied, and 8.7% were wasted. Although the refugees were able to procure some nonration foods by foraging, planting trees and vegetables, raising animals, and purchasing and exchanging ration foods for other items, the quantity and quality were not sufficient to compensate for the nutrients that were low or lacking in the ration. The overwhelming majority of dietary nutrients were provided by ration foods, and although the ration and the overall diet may be adequate for short-term subsistence, they do not suffice for long-term survival and optimal growth, especially for younger children.     

Synthesis and phase evolution of electrospun antiferroelectric lead zirconate (PbZrO3) nanofibers

Lead zirconate (PbZrO₃; PZO) fibers were synthesized by the electrospinning method using a solution that contained 5 wt% poly(ethylene oxide) (PEO) in ethanol and a sol–gel solution of PZO. Some parameters varied, for example, the ratio between PEO and PZO, concentrations of the precursor solution, flow rate, and calcination temperature. The as-spun and calcined PZO/PEO composite fibers were characterized by TG-DTA, X-ray diffraction, FT-IR, SEM and TEM. PZO fibers were obtained successfully with a well-developed perovskite structure after as-spun PZO/PEO composite fibers were calcined using the PZO/PEO volume ratio of 10:3 at a PZO concentration of 1.0 M at 650 °C for 4 h. Stable nanofibers were produced with an average diameter of 300 ± 64 nm. Additionally, the PZO fibers showed a Curie temperature that rose by nearly 13 °C, when comparing with a normal PZO particle.     

Parallelogram-like microparticles of calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) obtained by a rapid precipitation route in aqueous and acetone media

Calcium dihydrogenphosphate monohydrate (Ca(H₂PO₄)₂·H₂O) was prepared by a rapid and simple precipitation method using CaCO₃ and H₃PO₄ in aqueous and acetone media at ambient temperature. The thermal transformation of the synthesized Ca(H₂PO₄)₂·H₂O at 500 °C was obtained to be CaP₂O₆ occurred through the dehydration and the phosphate condensation reactions, as revealed by thermoanalytical techniques (TG/DTG/DTA). The synthesized Ca(H₂PO₄)₂·H₂O and its decomposition product CaP₂O₆ were characterized by X-ray powder diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy and scanning electron microscope (SEM). Thermal behavior and the morphology of the synthesized Ca(H₂PO₄)₂·H₂O in aqueous and acetone media are compared with those of other works. The SEM micrograph of Ca(H₂PO₄)₂·H₂O show parallelogram-like microparticles containing small and large grain sizes. The aqueous and acetone media are proposed to play an important role in the synthetic process of calcium phosphates in exhibiting different physical properties, which are important for specific applications.     

Thermal kinetic analysis of a complex process from a solid-state reaction by deconvolution procedure from a new calculation method and related thermodynamic functions of Mn0.90Co0.05Mg0.05HPO4·3H2O

Three individual peaks of thermal solid-state reaction processes of the synthesized Mn_0.90Co_0.05Mg_0.05HPO₄·3H₂O were observed corresponding to dehydration I, dehydration II and polycondensation processes. An alternative method for the calculation of the extent of conversion was proposed from the peak area of the individual DTG peak after applying the best fitting deconvolution function (Frazer-Suzuki function). An iterative integral isoconversional equation was used to compute the values of the apparent activation energy E_α and they were found to be 65.87, 78.16 and 119.32 kJ/mol for three peaks, respectively. Each individual peak was guaranteed to be a single-step kinetic system with its unique kinetic parameters. The reaction mechanism functions were selected by the comparison between experimental and model plots. The results show that the first, second and final individual peaks were two-dimensional diffusion of spherical symmetry (D₂), three-dimensional diffusion of spherical symmetry (D₃) and contracting cylinder (cylindrical symmetry, R₂) mechanisms. Pre-exponential factor values of 3.91×10⁶, 1.35×10⁷ and 2.15×10⁷ s^?1 were calculated from the E_α values and reaction mechanisms. The corresponded standard thermodynamic functions of the transition-state (activated) complexes were determined and found to agree well with the experimental data.