Preparation of nano-sized cerium and titanium pyrophosphates via solid-state reaction at room temperature

Nano-sized cerium-titanium pyrophosphates Ce1-xTixP2O7 （with x = 0, 0.2, 0.5, 0.7, 0.9, and 1.0） were obtained by grinding a mixture of Ce（SO4）2·4H2O, Ti（SO4）2, and Na4P2O7·10H2O in the presence of surfactant PEG-400 at room temperature, washing the mixture with water to remove soluble inorganic salts, and drying at 100℃. The products and their calcined samples were characterized using ultraviolet-visible spectroscopy （UV-vis）, thermogravimetry and differential thermal analyses （TG/DTA）, X-ray powder diffraction （XRD）, and transmission electron microscopy （TEM）. The results show that nano-sized Ce1-xTixP2O7 behave as an excellent UV-shielding material. Thereinto, the CeP2O7 has the most excellent UV-shielding effect, and the amorphous state of Ce0.8Ti0.2P2O7 can keep at a higher temperature than CeP2O7. Therefore, the stabilization of the amorphous state of the cerium pyrophosphates was carded out by doping titanium. This stabilization is a significant improvement, which enables to apply these amorphous pyrophosphates not only to cosmetics and paints, but also plastics and films.

Electrochemical properties of spinel LiMn_2O_4 and LiAl_(0.1)Mn_(1.9)O_(3.9)F_(0.1) synthesized by solid-state reaction

Two types of spinel cathode powders, LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1, were synthesized by solid-state reaction, X-ray diffraction （XRD） patterns of the prepared samples were identified as the spinel structure with a space group of Fd 3^- m. The cubic lattice parameter was determined from least-squares fitting of the XRD data. The LiAl0.1Mn1.9O3.9F0.1 sample showed a little lower initial capacity, but better cycling performance than the LiMn2O4 sample at both room temperature and an elevated temperature. The Vanderbilt method was used to test the electrochemical conductivity of the LiMn2O4 samples. The electrochemical impedance spectroscopy （EIS） method was employed to investigate the electrochemical properties of these spinel LiMn2O4 samples.

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.

Effects of Solid-State Reaction Synthesis Processing Parameters on Thermoelectric Properties of Mg_2Si

The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.

Preparation of new sunscreen materials Ce_(1-x)Zn_xO_(2-x) via solid-state reaction at room temperature and study on their properties

Superfine cerium-zinc oxides Ce1-xZnxO2-x with x = 0, 0.1, 0.3, 0.5, and 1.0 were obtained by grinding Ce（SO4）2·4H2O, ZnSO4·7H2O and NH4HCO3 under the condition of surfactant PEG-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts, drying at 80°C, and calcining.The precursor and its calcined samples were characterized using thermogravimetry and differential thermal analyses（TG/DTA）, UV-vis absorption spectroscopy, X-ray powder diffraction（XRD）, and scanning electron microscopy（SEM）.The results showed that superfine Ce1-xZnxO2-x behaved as an excellent UV-shielding material.The ZnO-doped CeO2 can facilitate the formation of crystalline state CeO2.The catalytic ability of products used in air oxidation of castor oil was investigated.The results showed that the catalytic abilities of products decreased with increasing zinc amount.

Synthesis and characterization of high-voltage cathode material LiNi_(0.5)Mn_(1.5)O_(4)by one-step solid-state reaction

LiNi_(0.5)Mn_(1.5)O_(4)was prepared under various conditions by one-step solid-state reaction in air and its properties were investigated by X-ray diffractormetry(XRD),scanning electron microscopy(SEM)and electrochemical measurement.XRD patterns show that LiNi_(0.5)Mn_(1.5)O_(4)synthesized under various conditions has cubic spinel structure.SEM images exhibit that the particle size increases with increasing calcination temperature and time.Electro chemical test shows that the LiNi_(0.5)Mn_(1.5)O_(4)calcined at 700℃for 24 h delivers up to 143 mA·h/g,and the capacity retains 132 mA·h/g after 30 cycles.

Preparation of NH_4ZrH(PO_4)_2·H_2O via solid-state reaction at low heat and its catalytic performance in the synthesis of butyl acetate

Nanocrystalline NH4ZrH（PO4）2·H2O was obtained by grinding ZrOC12·8H2O and （NH4）2HPO4 in the presence of surfactant PEG-400 via solid-state reaction at room temperature. The product NH4ZrH（PO4）2·H2O and its product of thermal decomposition were characterized using thermogravimetry and differential thermal analyses （TG/DTA）, Fourier transform infrared spectroscopy （FT-IR）, X-ray powder diffraction （XRD）, and transmission electron microscopy （TEM）. Nanocrystalline NHaZrH（PO4）2·H2O with an average particle size of 17 nm was obtained when the product was kept at80℃ for 3 h. Its crystalline framework was stable at temperatures below 250℃. In addition, the catalytic performance of NH4ZrH（PO4）2·H2O in the synthesis of butyl acetate was investigated. The results show that NH4ZrH（PO4）2·H2O behaved as an excellent heterogeneous catalyst in the synthesis of butyl acetate.

Effect of NH_4F and Nano-SiO_2 on Morphological Control of α-Al_2O_3 Platelets via Solid-state Reaction

Alpha-alumina(α-Al_2O_3) platelets were prepared via solid-state reaction using pseudo-boehmite as the starting material, while NH_4F and nano-SiO_2 were used as additives, and nitric acid was used as the binder. The effect of these additives on properties of the alumina platelets was determined via scanning electron microscopy, X-ray diffraction, and measurements of the surface area and silicon content. A mechanism governing their role in the synthesis process was proposed. The results indicated that NH_4F could promote the formation of highly crystalline platelets. Addition of nano-SiO_2 could lead to increase in the diameter and reduction in the thickness of the platelets, and could also prevent their transformation to α-Al_2O_3. This addition weakened the effect of NH_4F because of the reaction of nano-SiO_2 with F-species and the formation of volatile SiF_4.

Effect of Ethanol on Synthesis and Electrochemical Property of Mesoporous Al-doped Titanium Dioxide via Solid-state Reaction

Mesoporous aluminum-doped titanium dioxide(Al-TiO2) materials with high specific surface areas were prepared via a solid-state reaction route.The properties of these materials were characterized by X-ray diffraction(XRD),high resolution transmission electron microscopy(HRTEM),energy dispersive spectroscopy(EDS),N2 absorption-desorption,ultraviolet visible light spectroscopy(UV-Vis) and electrochemical spectroscopy.The results show that the mesoporous structure of the product with ethanol is composed of anatase laced crystal walls with amorphous grain boundaries formed gradually by degradation.Compared with those without ethanol,these samples possess larger crystallite size since ethanol decreases the pore size at higher temperature.With the increase of ethanol amount,however,the crystallite size will grow.The amorphous grain boundaries in the mesoporous material,with a large impedance and low incidental cyclic potential,are difficult to effectively degrade and the phase transformation temperature is changed from 500 to 550℃.The growth rate of Al-TiO2 crystallites that obeys the quadratic polynomial equation may be controlled.

Synthesis of Nano-sized Barium Titanate Powder by Solid-state Reaction between Barium Carbonate and Titania

Size control of BaTiO3 in solid-state reaction between BaCO3 and TiO2 was demonstrated by varying the size of TiO2 and milling conditions of BaCO3. The smaller TiO2 particles had higher surface area, resulting in faster initial reaction. The mechanically milled BaCO3 particles accelerated the diffusion process and decreased the calcinations temperature. It can be deduced from the results that the size control is possible and nano-sized BaTiO3 particles with about 60 nm can be synthesized by using the conventional solid-state reaction between BaCO3 and TiO2.

Solid-state reaction of a CaO−V_(2)O_(5)mixture:A fundamental study for the vanadium extraction process

The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V_(2)O_(5),which is the predominant binary mixture involved in the vanadium recovery process.Thermal analysis,X-ray diffraction spectroscopy,scanning electron microscopy,and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples.The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns.The results indicate that the solid reaction of the CaO−V_(2)O_(5)mixture is strongly influenced by the reaction temperature and CaO/V_(2)O_(5)mole ratio.The transformation of calcium vanadate in-volves a step-by-step reaction of CaO−V_(2)O_(5),CaO−CaV_(2)O_(6),and CaO−Ca_(2)V_(2)O7 depending on the CaO/V_(2)O_(5)mole ratio.The kinetic data of the solid reaction of the CaO−V_(2)O_(5)(1:1)mixture followed a second-order reaction model.The activation energy(Ea)and preexponential factor(A)were determined to be 145.38 kJ/mol,and 3.67×10^(8)min^(−1),respectively.

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 Mn_(0.90)Co_(0.05)Mg_(0.05)HPO_4?3H_2O

Three individual peaks of thermal solid-state reaction processes of the synthesized Mn0.90Co0.05Mg0.05HPO4?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 Eαand 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 Eαvalues 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.

Microwave direct synthesis and thermoelectric properties of Mg_(2)Si by solid-state reaction

In order to reduce the oxidation and volatilization caused by Mg element in the traditional methods for synthesizing Mg2Si compounds,Mg2Si thermoelectric materials were prepared by solid state reaction and microwave radiation techniques.Structure and phase composition of the materials were investigated by X-ray diffraction.The electrical conductivity,Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 700 K.It is found that high purity Mg2Si powders can be obtained with excessive content of 8% Mg from the stoichiometric Mg2Si at 853 K and 2.5 kW for 30 min.A maximum dimensionless figure of merit,ZT,of about 0.13 was obtained for Mg2Si at 600 K.

Preparation and electrochemical characteristics of Co_3(PO_4)_2-coated LiNi_(0.8)Co_(0.2)O_2 by solid-state reaction at room temperature

LiNi0.8Co0.2O2 particles were modified by Co3（PO4）2 coating. The effects of the Co3（PO4）2 coating on the structure and electrochemical properties of the LiNi0.8Co0.2O2 cathode material were investigated. The Co3（PO4）2 coating forms a thin layer on the surface of the LiNi0.8Co0.2O2 material and a solid solution by interacting with the LiNi0.8Co0.2O2 core material during calcination at 700℃ for 4 h. Charge-discharge experiment results show that the Co3（PO4）2 coating improves the cycling stability of the LiNi0.8Co0.2O2 cathode material. The capacity retention of the pristine LiNi0.8Co0.2O2 cathode after 50 cycles is 83.6%, whereas it is 91.7% in the case of the LiNi0.8Co0.2O2 cathode coated with 1 wt.% Co3（PO4）2. Storage tests of the 4.35 V charged electrode at 60℃ after a month show that the Co3（POg）2-coated sample exhibits good storage properties compared with the pristine sample.

Synthesis and ionic conductivity of Li_6La_3BiSnO_(12) with cubic garnet-type structure via solid-state reaction

The synthesis and transport properties of the Li6La3BiSnO1212 solid electrolyte by a solid-state reaction were reported. The condition to synthesize the Li6La3BiSnO1212 is 785 °C for 36 h in air. The refined lattice constant of Li6La3 BiSnO1212 is 13.007A. Qualitative phase analysis by X-ray powder diffraction patterns combined with the Rietveld method reveals garnet type compounds as major phases. The Li-ion conductivity of the prepared Li6La3BiSnO12 is 0.85×10^-4 S/cm at 22 °C, which is comparable with that of the Li5La3Bi2O12. The Li6La3BiSnO1212 compounds are chemically stable against Li CoO2 which is widely used as cathode material up to 700 °C but not against the Li Mn2O4 if the temperature is higher than 550 °C. The Li6La3 BiSnO1212 exhibits higher chemical stability than Li5La3Bi2O12, which is due to Sn substitution for Bi.

Synthesis and electrochemical performance of 5V spinel LiNi_(0.5)Mn_(1.5)O_4 prepared by solid-state reaction

Spinel compound LiNi0.5Mn1.5O4 with high capacity and high rate capability was synthesized by solid-state reaction. At first, MnCl2·4H2O and NiCl2·6H2O were reacted with (NH4)2C2O4·H2O to produce a precursor via a low-temperature solid-state route, then the precursor was reacted with Li2CO3 to synthesize LiNi0.5Mn1.5O4. The effects of calcination temperature and time on the physical properties and electrochemical performance of the products were investigated. Samples were characterized by thermal gravimetric analysis(TGA), scanning electron microscopy(SEM), X-ray diffractometry(XRD), charge-discharge tests and cyclic voltammetry measurements. Scanning electron microscopy(SEM) image shows that as calcination temperature and time increase, the crystallinity of the samples is improved, and their grain sizes are obviously increased. It is found that LiNi0.5Mn1.5O4 calcined at 800 ℃ for 6 h exhibits a typical cubic spinel structure with a space group of Fd3m. Electrochemical tests demonstrate that the sample obtained possesses high capacity and excellent rate capability. When being discharged at a rate as high as 5C after 30 cycles, the as-prepared LiNi0.5Mn1.5O4 powders can still deliver a capacity of 101 mA·h/g, which shows to be a potential cathode material for high power batteries.

Effect of Lithium Nitrate on the Structure and Property of α-Al2O3 Platelets Prepared via Solid-state Reaction

The α-Al_2O_3 platelets were prepared via solid-state reactions and the effect of the amount of lithium nitrate additive on the property of the platelets was investigated. The ICP results indicated that the high temperature calcination process resulted in a large loss of lithium species because of volatilization, but there was still a small amount of residual lithium species in the α-Al_2O_3 platelets. The SEM micrographs showed that lithium nitrate led to decrease in the thickness of α-Al_2O_3 platelets and irregular morphology of aggregates. Pore structures results exhibited that addition of lithium nitrate led to decrease in the pore size and increase in the specific surface area of aggregates of α-Al_2O_3 platelets. The XRD and IR patterns suggested that the residual lithium and aluminum oxide formed LiAl_5O_8. The existence of LiAl_5O_8 was the basic reason for the changed performance of α-Al_2O_3 platelets.

Preparation of transparent yttrium aluminum garnet ceramics by relatively low temperature solid-state reaction

A new preparation method for a highly sinterable Y 2O 3 powder was developed, using the mixture of the powder with Al 2O 3 powder, a transparent yttrium aluminum garnet(YAG) ceramic was prepared at relatively low temperature by a solid state reaction method. Yttrium nitrate was used as a mother salt, and aqueous ammonia was used as a precipitant reagent, the fine and dendritic precursor crystalline was prepared by adding 0.5% ammonium sulfate into the precipitation reaction system. The highly pure and low agglomerated Y 2O 3 powders were obtained by calcinating the precursor at 1 100 ℃, the primary particles are spherical and 60 nm in diameter. The mixture of Y 2O 3 and Al 2O 3 powders was calcinated, and the resulting mixture compact pressed in mold could be sintered to transparency under vacuum at 1 700 ℃. The sintered transparent YAG polycrystalline exhibits a homogeneous microstructure and its transmittance reaches 45% in the visible light region and 70% in the near infrared wavelength region.

Investigation of solid-state reaction by terahertz time-domain spectroscopy

Terahertz time-domain spectroscopy(THz-TDS)was utilized to investigate the solid-state reaction between L(+)-Tartaric acid and sodium hydrogen carbonate.Solid sodium hydrogen L(+)-tartrate monohydrate was synthesized efficiently by mechanical grinding,which is particularly sustainable and environmentally benign.Distinct THz absorptions were observed for pure reactants and the proposed product.The reaction process could be clearly visualized by THz spectral patterns of the reaction mixtures at different grinding time.The observed results were further confirmed by synchrotron radiation X-ray powder diffraction(SRXRPD)and Fourier transform infrared (FT-IR)spectroscopy.The study demonstrates that THz-TDS is an effective novel tool to monitor solid-state reactions in pharmaceutical industry.

Solid-State Reaction and Vacancy-Type Defects in Bilayer Fe/Hf Studied by the Slow Positron Beam

The positron annihilation lifetimes and the Doppler broadening by slow positron beam are measured in thin Fe films with thickness 500 nm, a thin Hf film with thickness 100 nm, and the bilayer Fe (50 nm)/Hf (50 nm) on quartz glass substrate. We have analyzed the behavior in vacancy-type defects in each layer through some deposition temperatures and annealing. It is observed that the thin Fe film, the thin Hf film, and the bilayer Fe (50 nm)/Hf (50 nm) already contain many vacancy-type defects. We have investigated the change of densities of the vacancy-carbon complex and the small vacancy-cluster with carbons, through solid-state amorphization of Fe (50 nm)/Hf (50 nm) bilayer.