A Convenient Method for Preparing Well-Dispersed Er2Zr2O7 Nanocrystals

2010 ◽  
Vol 123-125 ◽  
pp. 611-614 ◽  
Author(s):  
Yu Ping Tong ◽  
Rui Zhu Zhang ◽  
Shun Bo Zhao ◽  
Chang Yong Li
Keyword(s):  
Particle Size ◽  
Combustion Synthesis ◽  
Crystal Size ◽  
Lattice Distortion ◽  
Combustion Method ◽  
Treatment Temperature ◽  
Synthesis Process ◽  
Thermal Treatment Temperature ◽  
Average Size ◽  
Xrd And Tem

Well-dispersed fluorite Er2Zr2O7 nanocrystals have been successfully prepared by a convenient salt-assistant combustion method. The effects of calcinations temperature and salt category on the characteristics of the products were investigated by XRD and TEM. The thermal treatment temperature has an important effect on crystal size and lattice distortion of the nanocrystals. The experiment showed that the introduction of salt in the combustion synthesis process resulted in the formation of well-dispersed Er2Zr2O7 nanocrystals. The average size was 30 nm and was in agreement with the XRD result, which indicated that the nanocrystals were uniform in particle size distribution. Moreover, the possible formation process in the salt-assisted combustion synthesis was also analyzed.

scholarly journals Solution Combustion Synthesis of Cr2O3 Nanoparticles and the Catalytic Performance for Dehydrofluorination of 1,1,1,3,3-Pentafluoropropane to 1,3,3,3-Tetrafluoropropene

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 361 ◽  
Author(s):  
Haili Wang ◽  
Wenfeng Han ◽  
Xiliang Li ◽  
Bing Liu ◽  
Haodong Tang ◽  
...  
Keyword(s):  
Particle Size ◽  
Combustion Synthesis ◽  
Reaction Rate ◽  
Crystal Size ◽  
Solution Combustion Synthesis ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Chromium Nitrate ◽  
Solution Combustion ◽  
Cr2o3 Nanoparticles

Cr2O3 nanoparticles were prepared by solution combustion synthesis (SCS) with chromium nitrate as the precursor and glycine as the fuel. Commercial Cr2O3 and Cr2O3 prepared by a precipitation method were also included for comparison. The morphology, structure, acidity and particle size of fresh and spent Cr2O3 catalysts were investigated by techniques such as XRD, SEM, TEM, BET and NH3-TPD. In addition, catalytic performance was evaluated for the dehydrofluorination of 1,1,1,3,3-pentafluoropropane (CF3CH2CHF2, HFC-245fa) to 1,3,3,3-tetra-fluoropropene (CF3CH=CHF, HFO-1234ze). The catalytic reaction rate of Cr2O3 prepared by SCS method is as high as 6 mmol/h/g, which is about 1.5 times and 2 times higher than that of precipitated Cr2O3 and commercial Cr2O3, respectively. The selectivity to HFO-1234ze for all the catalysts maintains at about 80%. Compared with commercial and precipitated Cr2O3, Cr2O3-SCS prepared by SCS possesses higher specific surface area and acid amount. Furthermore, significant change in the crystal size of Cr2O3 prepared by SCS after reaction was not detected, indicating high resistance to sintering.

Research on Mechanochemical of Silica and its Composite Powders

2014 ◽  
Vol 881-883 ◽  
pp. 1487-1491 ◽  
Author(s):  
Jing Jing Zhu ◽  
Hua Zhi Gu ◽  
Tian Xing Peng ◽  
Bao Hua Sun
Keyword(s):  
Particle Size ◽  
Crystal Size ◽  
Lattice Distortion ◽  
X Ray Diffraction ◽  
Composite Powders ◽  
X Ray ◽  
Peak Intensity ◽  
Area Increase ◽  
Surface Area Increase ◽  
Grinding Time

Silca and its composite powders added different amount of microsilica were ground in a planetary ball mill (QM-3SP4) at various grinding period with addition of a certain number of grinding aid. The effects of mechano-chemical on particle size, crystal size and lattice deformation in grinding process were analyzed. The phase compositions and size compositions of the treated powders were investigated by X-ray Diffraction (XRD) and Laser Particle Size Analyzers. With the increase of grinding time, the particle size decrease, the specific surface area increase, and the more amount of microsilica added, the smaller particle size the powders had after grinding. The XRD results showed that the diffraction peak intensity of powders weaken and gradually widen. The surface of the particle happened to amorphization, and occurred grain refinement and lattice distortion. Comparing with other treated powders, the change of the powders with the microsilica addition of 5% was larger. Even though the grinding time reached to 30h, the crystal transformation of SiO2has not been detected.

Synthesis and Luminescent Properties of Pr3+ Activated KNbO3 Phosphors by Sol-Gel Combustion Process

2013 ◽  
Vol 873 ◽  
pp. 783-786 ◽  
Author(s):  
Jun Ji Zhang ◽  
Hui Zhou ◽  
Ji Shi Chen ◽  
Ting Tang ◽  
Yuan Zheng Hao
Keyword(s):  
Particle Size ◽  
Single Phase ◽  
Sol Gel ◽  
Combustion Process ◽  
Luminescent Properties ◽  
Phase Evolution ◽  
Combustion Method ◽  
Treatment Temperature ◽  
Nanoscale Particles ◽  
Gel Combustion

Praseodymium doped KNbO3 (KNbO3:Pr) phosphors were synthesized by a facile solgel combustion method. Phase evolution, particle size and luminescent properties of the powders synthesized at various temperatures were investigated. Single-phase KNbO3:Pr nanoscale particles were obtained at 600°C by directly crystallizing from amorphous precursors. The particle size of KNbO3:Pr powders can be well controlled by varying the heat treatment temperature. Under the excitation of 450 nm, KNbO3:Pr phosphors showed the well-known Pr3+ emissions associated with the 4f inter-level electronic transitions in Pr3+ ions.

Effect of Carbon Source Content on the Carbothermal Synthesis of AlN Powders Using a Combustion Synthesis Precursor

2012 ◽  
Vol 554-556 ◽  
pp. 526-531
Author(s):  
Ai Min Chu ◽  
Ming Li Qin ◽  
Bao Rui Jia ◽  
Hui Feng Lu
Keyword(s):  
Particle Size ◽  
Carbon Source ◽  
Combustion Synthesis ◽  
Aluminum Nitrate ◽  
Spherical Particles ◽  
Molar Ratio ◽  
Mixed Solution ◽  
Particle Size And Morphology ◽  
Size And Morphology ◽  
Average Size

AlN powders were synthesized by carbothermal reduction method using a combustion synthesis precursor derived from aluminum nitrate (oxidizer), glucose (carbon source), and urea (fuel) mixed solution. Effects of carbon source content on the combustion temperature of solutions, the particle size and morphology of the precursors and the synthesized AlN were studied in detail. The results indicated that a regular variation in the particle size and morphology of precursors had been observed with the increasing molar ratio of glucose to aluminum nitrate (C/Al). The products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, could have completed the nitridation reaction, while the nitridation products prepared with (C/Al=4 and 16) are opposite. The nitridation products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, are comprised of well-distributed spherical particles of AlN with the average size ranging from 50 to 80 nm.

Rapid Synthesis of Eu2Zr2O7 Nanocrystals via Salt-Assistant Combustion Method

2009 ◽  
Vol 79-82 ◽  
pp. 405-408
Author(s):  
Yu Ping Tong ◽  
Chang Yong Li ◽  
Shun Bo Zhao
Keyword(s):  
Low Cost ◽  
Three Dimensional ◽  
Combustion Method ◽  
Treatment Temperature ◽  
Fluorescent Properties ◽  
Solution Combustion ◽  
Excitation Spectra ◽  
Transmission Electron ◽  
Average Size ◽  
20 Nm

Eu2Zr2O7 nanocrystals with cubic structure were successfully synthesized by salt-assistant combustion method. The Eu2Zr2O7 nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Emission/ excitation spectra. The effect of thermal treatment temperature on the crystal size of nanocrystals was studied. The results indicated that Eu2Zr2O7 nanocrystals obtained by this method were well-dispersed and uniform in particle size distribution with average size of 20 nm. By comparison, it was found that the introduction of KCl in the solution combustion reaction process can effectively prevent nanocrystallites from sintering and forming inseparable three-dimensional network, and result in the formation of well-dispersed nanoparticles. The method provides a convenient, low-cost and nontoxic route for the synthesis of nanostructures of oxide materials. Moreover, the strong fluorescent property of the Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method at 385 nm upon excitation was measured at room temperature. The results showed that Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method put up excellent fluorescent properties.

Continuous Precipitation of Lead Iodide

1994 ◽  
Vol 59 (7) ◽  
pp. 1503-1510
Author(s):  
Stanislav Žáček ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Particle Size ◽  
Crystal Size ◽  
Crystal Growth Rate ◽  
Laboratory Model ◽  
Lead Iodide ◽  
Secondary Nucleation ◽  
Equimolar Ratio ◽  
Continuous Precipitation ◽  
The Mean

Lead iodide was precipitated from aqueous solutions of 0.015 - 0.1 M Pb(NO3)2 and 0.03 - 0.2 M KI in the equimolar ratio using a laboratory model of a stirred continuous crystallizer at 22 °C. After reaching the steady state, the PbI2 crystal size distribution was measured sedimentometrically and the crystallization kinetics was evaluated based on the mean particle size. Both the linear crystal growth rate and the nucleation rate depend on the specific output of the crystallizer. The system crystallization constant either points to a significant effect of secondary nucleation by the mechanism of contact of the crystals with the stirrer blade, or depends on the concentrations of the components added due to the micromixing mechanism.

Batch Precipitation of Lead Iodide

1994 ◽  
Vol 59 (6) ◽  
pp. 1301-1304
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Crystal Size ◽  
Lead Nitrate ◽  
Lead Iodide ◽  
Constant Rate ◽  
Mean Size ◽  
The Mean

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.

scholarly journals Microwave-Assisted Combustion Synthesis of ZnO Nanoparticles

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
M. Kooti ◽  
A. Naghdi Sedeh
Keyword(s):  
Electron Microscopy ◽  
Zno Nanoparticles ◽  
Combustion Method ◽  
Zinc Nitrate ◽  
High Yield ◽  
Fast Method ◽  
Simple Method ◽  
X Ray ◽  
Microwave Assisted ◽  
Average Size

A new and simple method was applied for the synthesis of ZnO nanoparticles with an average size of 20 nm. In this microwave-assisted combustion method, glycine as a fuel and zinc nitrate as precursor were used. The final product was obtained very fast with high yield and purity. The synthesized nanoscale ZnO was characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT-IR). The size and morphology of the ZnO nanoparticles have been determined by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. This is a simple and fast method for the preparation of ZnO nanoparticles with no need for expensive materials or complicated treatments.

scholarly journals ZnWO4 Nanoparticle Scintillators for High Resolution X-ray Imaging

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1721
Author(s):  
Heon Yong Jeong ◽  
Hyung San Lim ◽  
Ju Hyuk Lee ◽  
Jun Heo ◽  
Hyun Nam Kim ◽  
...  
Keyword(s):  
Particle Size ◽  
Zinc Oxide ◽  
High Resolution ◽  
Tungsten Oxide ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
X Ray ◽  
X Ray Imaging ◽  
Average Size ◽  
And Tungsten

The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 μm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.

Direct Synthesis of 3,5-Dinitropyrazole Catalyzed by Newly Sulfated Nanosolid Superacid TiO2/ SO

2011 ◽  
Vol 391-392 ◽  
pp. 1296-1301
Author(s):  
Li Min Xi ◽  
Xin Xin Zhang
Keyword(s):  
Direct Synthesis ◽  
Sol Gel ◽  
Acid Base ◽  
Direct Transformation ◽  
Acid Base Titration ◽  
Optimal Reaction Condition ◽  
Superacid Catalyst ◽  
Average Size ◽  
Optimal Reaction ◽  
Xrd And Tem

The newly sulfated nanosolid superacid TiO2/SO4 prepared by sol-gel method was broadly characterized by acid base titration, XRD and TEM, which identified that the superfine solid TiO2/SO4 showing good dispersibility with average size of 27 nm belongs to kind of crystalline nanoparticles. With the help of the catalyst TiO2/SO4, the optimal reaction condition for direct transformation of pyrazole and nitrosonitric acid into 3, 5-Dinitropyrazole was n (pyrazol)=0.10 mol, m (TiO2/SO4 )＝1.5g, V(n-octannol)＝90mL, and V(nitrosonitric acid)＝50mL. Moreover, the optimal yield of the catalytic reaction reached up to 59.4% when the reaction time is 7 hours. The nanosolid superacid catalyst is still of high activity after regenerating eight times by calcination at 600。C.

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