Facile synthesis of monodispersed copper oxalate flaky particles in the presence of EDTA

Monodispersed copper oxalate paxticles with flaky morphology were prepared via a simple one-pot synthesis method. Scanning electron microscope （SEM）, X-ray diffraction （XRD）, and fourier tza^sform infraJced （FTIR） spectra were used to characterize paxticle mor- phology, size, phase composition, and functional groups. It was found that the presence of ethylenediaminetetzaacetic acid （EDTA） and the solution pH value had strong influence on the morphological and size evolution of the precipitated particles. On the basis of controlled re- lease of copper ions from a Cu2＋-EDTA complex and Weimazn＇s law, a stzategy for the controlled synthesis of monodispersed copper oxa- late paxticles was designed by refemng to the basic mode of the St0ber method. The inherent nature of crystallization to form the flaky solid in the early stage of precipitation as well as the driving force of the long-lasting low supersaturation in the growth stage was proposed to ex- plain the size and morphological evolution of the copper oxalate precipitates. Thermodynamic equilibrium concentrations of copper（II） spe- cies in the Cu（II）-EDTA-oxalate-H20 solution system were calculated to help explain the possible formation mechaNsm of copper oxalate precipitates.

Effect of Flaky Plastic Particle Size and Volume Used as Partial Replacement of Gravel on Compressive Strength and Density of Concrete Mix

Common ways of disposing waste plastic such as incineration and landfilling have negative impacts on the environment. Partial replacement of natural aggregate in concrete with waste plastic including polyethylene terephthalate (PET) is more environmental friendly and sustainable. The effect of adding 5% to 20% waste plastic by volume of natural coarse aggregate (“gravel”) and plastic particle size (3 to 7 mm) on the density and compressive strength of plastic-concrete mix after 28 days of curing was studied. The results showed that density of the concrete decreased from 2406.7 to 2286.7 kg/m3 as waste plastic increased from 5% to 20% v/v compared with 2443.3 kg/m3 recorded by concrete without waste plastic. Change in particle size from 3 to 7 mm has no significant effect on the density of the plastic-concrete mix. The compressive strength decreased as the volume and particle size of waste plastic increased. When waste plastic volume changed from 5% to 20% v/v, the compressive strength decreased from 20.5 to 15 MPa, 18.6 to 14.3 MPa and 17.2 to 13.8 MPa for 3, 5 and 7 mm waste plastic particle size respectively while the concrete without plastic has 21.33 MPa. Therefore, the addition of 5% (v/v gravel) of flaky waste plastic in the concrete produces a lightweight concrete which could offer economic benefit without substantially reducing the compressive strength of the plastic-concrete mix.

Effects of flaky rare earth oxide additives on the high temperature performance of nickel electrodes

Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the ...

Facile synthesis of flake-like dihydrate zinc oxalate particles

Monodispersed dihydrated zinc oxalate(ZnC_2O_4·2H_2O) particles with characteristic morphology were synthesized by aging a mixed solution of zinc nitrate(Zn(NO_3)_2) and sodium oxalate(Na_2C_2O_4) in the presence of a citrate ligand, with an average flat size of approximately 10–15 μm. The important parameters, including the solution pH values and the concentration of the zinc ions and citrate ligand, were investigated using a series of experiments. It is verified that the citrate ligand significantly affects the morphology of zinc oxalate particles, probably via its multiple roles of chelating, dispersing, and selective absorption. Thermodynamic equilibrium of the distribution of zinc species in an aqueous solution of Zn(Ⅱ)-citrate-oxalate-H_2O was estimated to explain the experimental results and to clarify the size and morphological evolution mechanism of the precipitated particles.

Synthesis of High Purity SiC Powder for High-resistivity SiC Single Crystals Growth

High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.

EFFECT OF Si CONTENT ON ORDERING DEGREE AND ELECTROMAGNETIC CHARACTERISTICS IN FeSiAl ALLOYS

FeSiAl alloys ribbons synthesized by melt-quench were annealed in vacuum at 873 K for 60 rain. The flaky powders were prepared by milling the annealed ribbons for 70 h. After milling, the powders were heat treated at 573 K for 90 rain. The ordering degree of the powders lattice structure was analyzed by X-ray diffraction （XRD）. The measurement of specific saturation magnetization was carried out by vibrating samples magnetometer （VSM）. Complex permittivity and complex permeability in the frequency band of 0.5-18 GHz were measured with the vector network analyzer. The ordering degree of the superlattice structure increased from 0.2＇7 to 0.49. Complex permittivity and complex permeability decreased with increasing Si content. After ordering, the specific saturation magnetization decreased from 134.2 to 85.0 A.m2.kg-1. For use in anti-EMI material, the total contents of Si and Al in FeSiAl alloys should be controlled at a low level.

Double-layer Modifi cation of Water-based Aluminum with SiO2 and Polyacrylic Acid by Solgel Process and in situ Polymerization

A double-layer aluminum consisting of an aluminum core and a shellof SiO2 and polyacrylic acid was synthesized.This modified aluminum was used to improve the corrosion resistance and dispersive property of aluminum in waterborne media.TEM,FTIR,XPS,and EDX determination showed that PAA and SiO2 were coated on the surface of aluminum.Evolved hydrogen detection showed that the corrosion resistance of composite particle had been markedly improved.Maximum corrosion inhibition efficiency of SiO2 coated aluminum（SiO2@Al）was 95.1% while that of double-layer coated aluminum（PAA/SiO2@Al）was 98.8%.Meanwhile,polyacrylic acid layer improved the agglomeration of aluminum significantly.According to the dispersibility test,the particle size of 50% volume fraction [d（0.5）] of aluminum,SiO2@Aland PAA/SiO2@Alwere 42,53,and 34 μm,respectively.

Relationship between Retrographical and Physical Properties of Aggregates

The relationship between petrographical and physical properties of limestone, basalt, granite and gneiss was investigated. Petrographical data were quantified from polished thin sections with a polarising microscope to determine the modal composition. The properties of resistance to fragmentation and abrasion were determined by Los Angeles abrasion test and crushing test. The shape characteristic was measured by Flakiness index test. The experimental results indicate that abundance of fineto medium-grained minerals （especially of plagioclase, quartz and feldspar） are prime, and strong micrographic intergrowth texture with interlocking grain boundaries have the great positive influence on the physical properties. It is also indicated that petrographical properties and surface texture of rocks can decide the potentiality of rocks as raw materials with high quality on resisting fragmentation and abrasion. Analysis of Integration of petrographical data and mechanical properties is ideal for the selection of aggregates used in asphalt concrete.

Evaluating the Subgrade Reaction Modulus Variations with Soil Grains Shape in Coarse-Grained Soils Using Genetic Algorithm

Subgrade reaction modulus (Ks) is one of the main factors in evaluating engineering properties of soils for structural calculations and operations. So, many studies have been performed on the effect of other soil geotechnical parameters on it. One is the effect of soil grains shape on engineering properties of soils, especially Ks. The aim of the present research is to evaluate the effect of soil grains shape on Ks for coarse-grained soils of the west of Mashhad, Iran. For this purpose, 20 PLTs were performed on coarse-grained soils of the west of Mashhad and Ks amounts were determined. Then, flakiness and elongation of the samples measured and changes of Ks by soil grain shape were evaluated. The results showed the strength dependency of Ks to grain forms which an increase in flakiness and elongation indices leads to a decrease in Ks. Therefore, it is necessary to reduce Ks estimated form empirical relationships for flaky and elongated soils. So, by writing a genetic algorithm-based program to find the optimal relationship between the grain shape and the subgrade reaction coefficient, a valid equation for correcting the results from previous empirical equations was presented.

Electron Structure and Microwave Absorbing Ability of Flaky FeSiAl Powders

Soft magnetic metallic materials have been widely used for absorbing electromagnetic wave.Flaky Fe 86 t Si t Al 14（t=9,11,14 and 16） alloys powders were prepared from melt-quenched ribbons by annealing and milling.In a previous report we discussed the order-disordered structure of this alloys.In this article,we studied their electron structure.Covalence electron numbers of（111） and（100） plane increase with increasing Si content but Bohr magneton decreases.Complex permittivity and complex permeability are both decreased with increasing Si content t.The lowest value of reflectivity among the four alloys is originated from Fe 70 Si 14 Al 14.The peak values of reflectivity are all lower than 10 dB,and the absorbing frequency range（R 10 dB） increases from 1 to 2 GHz when t reaches 16.

Fabrication and characterization of Ag flake hybrid circuits with IPL-sintering

The study of photonic sintering has gained interest based on the advantages of fast processing at room temperature.However,printed electronics made from photonic sintering with an intensive pulsed light(IPL)energy source exhibit more mechanical instability than those made from conventional thermal sintering processes.To solve the mechanical instability problems,we fabricated Ag flake hybrid pastes with a variety of concentrations of Ag flake(0,25,50,75,and 100 wt.%).All of the screen-printed hybrid Ag circuits were fabricated on polyimide substrates and were sintered at 3.5 MW.Surface porosity was analyzed using the Brunauer-Emmett-Teller method.An IPC(Packaging Electronic Circuits)sliding test was performed to analyze the flexibility of the screen-printed Ag flake hybrid circuits.The adhesion strength of the hybrid circuits was evaluated with a roll-type 90°peel test.The hybrid Ag printed circuit showed improvements in both the flexibility and adhesion strength with the addition of Ag flake.