Synthesis, characterization and magnetic properties of KFeO_(2) nanoparticles prepared by a simple egg white solution route

Nanoparticles of potassium ferrite(KFeO_(2))in this work were synthesized by a simple egg white solution method upon calcination in air at 773,873,and 973 K for 2 h.The effects of calcination temperature on the structural and magnetic properties of the synthesized KFeO_(2) nanoparticles were investigated.By varying the calcination temperature,X-ray diffraction and transmission electron microscopy results indicated the changes in crystallinity and morphology including particle size,respectively.Notably,the reduction in particle size of the synthesized KFeO_(2) was found to have a remarkable influence on the magnetic properties.At room temperature,the synthesized KFeO_(2) nanoparticles prepared at 873 K exhibited the highest saturation magnetization(M_(S))of 2.07×10^(4) A·m^(−1).In addition,the coercivity(H_(C))increased from 3.51 to 16.89 kA·m^(−1) as the calcination temperature increased to 973 K.The zero-field cooled(ZFC)results showed that the blocking temperatures(T_(B))of about 125 and 85 K were observed in the samples calcined at 773 and 873 K,respectively.Therefore,this work showed that the egg white solution method is simple,cost effective,and environmentally friendly for the preparation of KFeO_(2) nanoparticles.

Influence of polymer solution on the morphology and local structure of NH_(4)ZnPO_(4)powders synthesized by a simple precipitation method at room temperature

NH_(4)Zn PO_(4)powders were synthesized using a simple precipitation method at room temperature.The effects of polyvinyl pyrrolidone(PVP),polyvinyl alcohol(PVA),glucose,and hexadecyltrimethylammonium bromide(CTAB)solutions on the morphology and structure of the prepared samples were investigated.The phase composition and morphology of the prepared samples were characterized using X-ray diffraction and scanning electron microscopy,respectively.Depending on the polymer sources,the hexagonal structure prepared using non-surfactant of water completely changed to monoclinic structure when CTAB was added.X-ray absorption near-edge structure(XANES)and X-ray photoelectron spectroscopy(XPS)were performed to study the local structure and surface electronic structure of the prepared samples,confirming that the oxidation states of P and Zn ions are^(5+)and^(2+),respectively.On the basis of the results of inductively coupled plasma atomic emission spectroscopy(ICP-OES),the NH_(4)Zn PO_(4)powders can be classified as a slow-release fertilizer where less than 15%of the ions were released in 24 h.A simple precipitation method using water,PVP,PVA,sucrose,and CTAB as a template can be used to synthesize NH4 Zn PO4 powders.In addition,this method may be extended for the preparation of other oxide materials.

Enhanced giant dielectric properties and improved nonlinear electrical response in acceptor-donor (Al^(3+), Ta^(5+))-substituted CaCu_(3)Ti_(4)0_(12) ceramics

The giant dielectric bchavior of CaCu_(3)Ti_(4)0_(12)(CCTO)has been widely investigated owing to its potential applications in electronics;however,the loss tangent(tan8)of this material is too large for many applications.A partial substitution of CCTO ceramics with either Al^(3+) or Ta^(5+)-ions generally results in poorer nonlinear properties and an associated increase in tan8(to~0.29-1.15).However,first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Tit sites,which can improve the electrical properties of the grain boundary(GB).Surprisingly,in this study,a greatly enhanced breakdown electric field(~200--6588 V/cm)and nonlinear coefficient(-4.8-15.2)with a significantly reduced tan8(~0.010--0.036)were obtained by simultaneous partial substitution of CCTO with acceptor-donor(Al^(3+),Ta^(5+))dopants to produce(Al^(3+),Ta^(5+))-CCTO ceramics.The reduced tan8 and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure.The signifcant reduction in the mean grain size of the(Al^(3+),Ta^(5+))-CCTO ceramics compared to pure CCTO was mainly because of the Ta^(5+)-ions.Accordingly,the increased GB density due to the reduced grain size and the larger Schottky barrier height(Ф_(b))at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance,improved nonlinear properties,and reduced tan8 values compared to pure and single-doped CCTO.In addition,high dielectric constant values(ε'≈(0.52-2.7)×10^(4))were obtained.A fine-grained microstructure with highly insulating GBs was obtained by Ta doping,while co-doping with Ta^(5+) and Al^(3+ )resulted in a high Ф_(b).The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.

Glycerol valorization through production of di-glyceryl butyl ether with sulfonic acid functionalized KIT-6 catalyst

In this work,the etherification of glycerol with n-butanol catalyzed by sulfonic acid functionalized on KIT-6 mesoporous silica(SO_(3)H-KIT-6)was investigated for the production of valuable fuel additives.The SO_(3)H-KIT-6 catalyst was synthesized by co-condensation with different molar ratios of tetraethoxysilane and 3-mercaptopropyl(methyl)di-methoxy silane.The etherification reaction was systematically examined to determine the optimal reaction temperature,reaction time,catalyst loading,and glycerol to n-butanol ratio under autogenous pressure.The maximum glycerol conversion and di-glyceryl n-butyl ether(di-GNBE)selectivity were 59.09 and 51.50%,respectively,when the SO_(3)H-KIT-6 catalyst with the highest acidity was applied.Interestingly,the presence of a methyl group on the catalyst surface prevented glycerol adsorption during the reaction process,leading to the inhibition of undesired product formation.The SO_(3)H-KIT-6 catalyst could be reused up to three times,with only a 13%decrease in glycerol conversion being found.Moreover,the superior performance of the SO_(3)H-KIT-6 catalyst for di-GNBE production was also demonstrated compared with conventional solid acid catalysts including HZSM-5,H-beta zeolite,Amberlyst-35,and Amberlyst-36.

Enhancement of output power density in a modified polytetrafluoroethylene surface using a sequential O_(2)/Ar plasma etching for triboelectric nanogenerator applications

In this work,the surface modification using a two-steps plasma etching has been developed for enhancing energy conversion performance in polytetrafluoroethylene(PTFE)triboelectric nanogenerator(TENG).Enhancing surface area by a powerful O_(2) and Ar bipolar pulse plasma etching without the use of CF_(4) gas has been demonstrated for the first time.TENG with modified surface PTFE using a sequential two-step O_(2)/Ar plasma has a superior power density of 9.9 W·m^(-2),which is almost thirty times higher than that of a pristine PTFE TENG.The synergistic combination of high surface area and charge trapping sites due to chemical bond defects achieved from the use of a sequential O_(2)/Ar plasma gives rise to the intensified triboelectric charge density and the enhancement of power output of PTFE-based TENG.The effects of plasma species and plasma etching sequence on surface morphologies and surface chemical species were investigated by a field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),and X-ray photoelectron spectroscopy(XPS).The correlation of surface morphology,chemical structure,and TENG performance was elucidated.In addition,the applications of mechanical energy harvesting for lighting,charging capacitors,keyboard sensing and operating a portable calculator were demonstrated.

Ultraelow loss tangent and giant dielectric permittivity with excellent temperature stability of TiO_(2) co-doped with isovalent-Zr4þ/ pentavalent-Ta5þ ions

The excellent giant dielectric properties(ExGDPs)are represented in the isovalenteZr4þ/pentavalent eTa5þions coedoped TiO_(2) with different coedoping percentages(x%ZrTTO).The dopants were dispersed homogeneously in a highly compactegrained ZrTTO microstructure.The mean grain size and cell parameters with bond lengths slightly enlarged as x%increased.The(1%e5%)ZrTTO oxides exhibited ultra elow tand values of 0.004e0.016 with the giant dielectric permittivity(ε0~2.7e3.7104);while theε0 of the 5%ZrTTO was slightly dependent on the temperature ranging from--60 to 200C,following the temperature dependence requirement for application in the X7/8/9R capacitors.Impedance spectroscopy showed a very large resistance of the grain boundaries.The dielectric properties of the 1%ZrTTO were strongly dependent on the applied DC electric field,indicating the dominant internal barrier layer capacitor(IBLC)effect.However,the dielectric properties of the 5%ZrTTO were nearly independent on the applied DC electric field up to 30 V/mm,which was primarily resulted from electron localization in defect dipoles.Therefore,the ExGDPs of the x%ZrTTO were attributed to the combined effects of the IBLC and localizedeelectron defectedipoles related to oxygen vacancies(Ti4þ,e--VO--e--,Ti4þand 3Ti4þ,e----VO--TaTi)and Ti4þ,e--TaTi.

Fabrication of fluoroalkylsilane/zeolitic imidazolate framework composites for highly efficient superhydrophobic coating

Superhydrophobic bagasse paper was successfully engineered by facile spray coating with a zeolitic imidazolate framework composite modified by 3,3,3-trifluoropropyltrimethoxysilane(FAS)and used as a filter membrane with special wettability for oil/water separation.Surface characteristics such as surface morphology,surface moieties,roughness,and wettability were observed.The addition of FAS decreased the apparent surface energy between solid surfaces and liquids with a polar contribution of surface free energy as low as 0 mN m−1.The formation of the FAS layer was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy core-level spectra.Three-dimensional surface topography revealed an increase in the spray coating cycle that enhanced the hydrophobicity of the coated paper.The results confirmed that not only microstructures but also the presence of functional groups with low surface energy(such as FAS)can promote surface hydrophobicity.The spray-coated paper with FAS/ZIF in the presence of a small amount of nanocellulose provided a superhydrophobic surface after the first spray cycle.The separation efficiency was up to 85%and was slightly affected by oil viscosity.Moreover,this can be used as a filter membrane for water-in-oil emulsions.In the present work,simple spray-coated paper is a promising candidate material for gravity-driven oil/water separation and water repellent coating.