scholarly journals GAS SENSITIVE SEMICONDUCTOR NANOMATERIALS FOR CREATION OF HYDROGEN SENSORS

2020 ◽  
pp. 40-44
Author(s):  
I. Matushko ◽  
L. Oleksenko ◽  
N. Maksymovych ◽  
G. Skolyar ◽  
O. Roik ◽  
...  
Keyword(s):  
Particle Size ◽  
Recovery Time ◽  
Oxidation Reaction ◽  
Hydrogen Oxidation ◽  
Precipitation Method ◽  
Hydrogen Sensors ◽  
Sensor Surface ◽  
Heater Power ◽  
Co Precipitation ◽  
Microcrystalline Material

Co-precipitaion method and sol-gel technique were used to prepare semiconductor microcrystalline and nanosized SnO2/Sb2O5 and Со/SnO2/Sb2O5 (0.15 wt.% Sb) materials aimed to create high sensitive hydrogen sensors. Morphology and phase composition of the obtained samples were studied by SEM, TEM and XRD methods. It was found that microcrystalline SnO2/Sb2O5 material with particle size of 1–30 μm was obtained by a co-precipitation method and nanosized SnO2/Sb2O5 material with particle size of 5–25 μm (an average size – 12 nm) was obtained by a zol-gel method. Only cassiterite phase was detected for both microcrystalline and nanosized materials. Sensitivity measurements of the sensors were carried out with using of air-hydrogen mixtures in the concentration range of 40 – 1145 ppm Н2, and dynamic characteristics (response time and relax time) were evaluated for 40 ppm Н2 at different heater power consumptions – 0.25 and 0.35 W. To increase sensitivities of the sensors, cobalt oxide, a known catalyst for hydrogen oxidation, was added to the resulting SnO2/Sb2O5 materials. It was shown that the sensors obtained by a zol-gel method demonstrate more significant sensitivity to hydrogen concentration in comparison with the sensors obtained by a co-precipitation method. It is probably associated with a higher surface area of the nanomaterial that agrees with its smaller particles as compared with the particles of the microcrystalline material. The Co-containing sensors based on the nanosized SnO2/Sb2O5 material are established to reveal higher sensitivity to Н2 than microcrystalline Co/SnO2/Sb2O5 sensors. The Co-containing sensors based on the nanosized SnO2/Sb2O5 material were found to have better dynamic characteristics than microcrystalline Co/SnO2/Sb2O5 sensors. The sensitivities increase and the response and recovery time decrease were found for both sensor materials at increasing of the sensors heater power consumption. The obtained results can be explained with different degree of energy surface heterogeneity of the used materials. The sensor response time is determined by the time of dynamic equilibrium establishment of the hydrogen oxidation reaction on the sensor surface and the recovery time is determined by the time of desorption of the H2 oxidation reaction products (H2O) from the sensor surface. Because of the processes, the sensor with a gas sensitive layer based on the nanosized material possessing with more homogeneous structure of its surface (according to the obtained TEM data) demonstrates improved gas sensitive properties in comparison with the sensor based on the microcrystalline material. The obtained results concerning the sensitivities to H2 and the dynamic parameters of the created sensors point to possibility of effective usage of the sensors based on the nanomaterial to detect H2 in air in the practice.

scholarly journals Impact of Iron on the Fe–Co–Ni Ternary Nanocomposites Structural and Magnetic Features Obtained via Chemical Precipitation Followed by Reduction Process for Various Magnetically Coupled Devices Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 341
Author(s):  
Tien Hiep Nguyen ◽  
Gopalu Karunakaran ◽  
Yu.V. Konyukhov ◽  
Nguyen Van Minh ◽  
D.Yu. Karpenkov ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Reduction Process ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Magnetic Characteristics ◽  
Reduction Temperature ◽  
Fe Content ◽  
Magnetic Features ◽  
Co Precipitation

This paper presents the synthesis of Fe–Co–Ni nanocomposites by chemical precipitation, followed by a reduction process. It was found that the influence of the chemical composition and reduction temperature greatly alters the phase formation, its structures, particle size distribution, and magnetic properties of Fe–Co–Ni nanocomposites. The initial hydroxides of Fe–Co–Ni combinations were prepared by the co-precipitation method from nitrate precursors and precipitated using alkali. The reduction process was carried out by hydrogen in the temperature range of 300–500 °C under isothermal conditions. The nanocomposites had metallic and intermetallic phases with different lattice parameter values due to the increase in Fe content. In this paper, we showed that the values of the magnetic parameters of nanocomposites can be controlled in the ranges of MS = 7.6–192.5 Am2/kg, Mr = 0.4–39.7 Am2/kg, Mr/Ms = 0.02–0.32, and HcM = 4.72–60.68 kA/m by regulating the composition and reduction temperature of the Fe–Co–Ni composites. Due to the reduction process, drastic variations in the magnetic features result from the intermetallic and metallic face formation. The variation in magnetic characteristics is guided by the reduction degree, particle size growth, and crystallinity enhancement. Moreover, the reduction of the surface spins fraction of the nanocomposites under their growth induced an increase in the saturation magnetization. This is the first report where the influence of Fe content on the Fe–Co–Ni ternary system phase content and magnetic properties was evaluated. The Fe–Co–Ni ternary nanocomposites obtained by co-precipitation, followed by the hydrogen reduction led to the formation of better magnetic materials for various magnetically coupled device applications.

Effect of the Synthesis Method on the Properties of Ultrafine YAG Powder

2018 ◽  
Vol 281 ◽  
pp. 40-45
Author(s):  
Jie Guang Song ◽  
Lin Chen ◽  
Cai Liang Pang ◽  
Jia Zhang ◽  
Xian Zhong Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Calcination Temperature ◽  
Hydrothermal Reaction ◽  
Synthesis Method ◽  
Particle Morphology ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Synthesis Process ◽  
Powder Materials ◽  
Co Precipitation

YAG materials has a number of unique properties, the application is very extensive. In this paper, the superfine YAG powder materials were prepared by co-precipitation method and hydrothermal precipitation method. The influence of synthesis process on the morphology of the powder was investigated. The results showed that the precursor powder prepared via the co-precipitation method is mainly from amorphous to crystalline transition with the increasing calcination temperature, the precursor agglomeration is more serious, In the process of increasing the calcination temperature, the dispersibility of the roasted powder is greatly improved, which is favorable for the growth of the crystal grains, so that the particle size of the powder is gradually increased, the YAG precursor prepared by the co-precipitation method is transformed into YAG crystals, the phase transition occurs mainly between 900 and 1100°C. When the molar ratio of salt to alkali is Y3+: OH-=1: 8 via the hydrothermal reaction, the YAG particles with homogeneous morphology can be obtained. When the molar ratio of salt and alkali is increased continuously, the morphology of YAG particles is not obviously changed. The co-precipitation method is easy to control the particle size, the hydrothermal method is easy to control the particle morphology.

Aluminate Green Phosphor with Small Particle Size Used for PDP via Co-Precipitation Method

2011 ◽  
Vol 295-297 ◽  
pp. 890-895
Author(s):  
Yan Dong ◽  
Yang Zhou ◽  
Xue Lin Han ◽  
Wei Jie Gu
Keyword(s):  
Particle Size ◽  
Phase Transformation ◽  
Small Particle ◽  
High Efficiency ◽  
Particle Growth ◽  
Solid State Reaction Method ◽  
Precipitation Method ◽  
Small Particle Size ◽  
Green Phosphor ◽  
Co Precipitation

Mg doped BaAl12O19:Mn2+ phosphor is one of the most efficient green phosphors for PDP. It is difficult to prepare the phosphor both have small particle size (< 3μm) and high luminescence. In the present work, a BaAl12O19:Mn2+ phosphor with small particle size was synthesized by the chemical co-precipitation method. Phase transformation and particle growth process during calcining process were investigated. The nucleation process was also discussed. The results show that, the phase transformation is complicated, the transition phases include BaCO3, γ-Al2O3, BaF2, BaAl2O4 and two phases contain Mn; The BaAl12O19 phase is formed from the reaction between BaAl2O4 phase and γ-Al2O3 phase, no a-Al2O3 phase appears during the entire process; The formation temperature of pure BaAl12O19 phase is 1200°C, which is lower than that in the high-temperature solid state reaction method. High efficiency BaAl12O19:Mn2+ phosphor with small particle size (< 2μm) and hexagonal flaky shape can be prepared by this method.

ChemInform Abstract: Preparation of BaMgAl10O17:Eu2+ Phosphor with Small Particle Size by Co-Precipitation Method.

ChemInform ◽  
2011 ◽  
Vol 42 (13) ◽  
pp. no-no
Author(s):  
Yan Dong ◽  
Zhisen Wu ◽  
Xuelin Han ◽  
Rong Chen ◽  
Weijie Gu
Keyword(s):  
Particle Size ◽  
Small Particle ◽  
Precipitation Method ◽  
Small Particle Size ◽  
Co Precipitation

The Influence of Calcination Temperature on Quantitative Phase of Hematite from Iron Stone Tanah Laut

2015 ◽  
Vol 1112 ◽  
pp. 489-492
Author(s):  
Ali Mufid ◽  
M. Zainuri
Keyword(s):  
Particle Size ◽  
Calcination Temperature ◽  
Thermo Gravimetric Analysis ◽  
Precipitation Method ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Particle Size Analyzer ◽  
Co Precipitation

This research aims to form particles of hematite (α-Fe2O3) with a basis of mineral iron ore Fe3O4 from Tanah Laut. Magnetite Fe3O4 was synthesized using co-precipitation method. Further characterization using X-ray fluorescence (XRF) to obtain the percentage of the elements, obtained an iron content of 98.51%. Then characterized using thermo-gravimetric analysis and differential scanning calorimetry (TGA-DSC) to determine the calcination temperature, that at a temperature of 445 °C mass decreased by 0.369% due to increase in temperature. Further Characterization of X-ray diffraction (XRD) to determine the phases formed at the calcination temperature variation of 400 °C, 445 °C, 500 °C and 600 °C with a holding time of 5 hours to form a single phase α-Fe2O3 hematite. Testing with a particle size analyzer (PSA) to determine the particle size distribution, where test results indicate that the α-Fe2O3 phase of each having a particle size of 269.7 nm, 332.2 nm, 357.9 nm, 412.2 nm. The best quantity is shown at a temperature of 500 °C to form the hematite phase. This result is used as the calcination procedure to obtain a source of Fe ions in the manufacture of Lithium Ferro Phosphate.

Morphology-Controlled CaCO3 Nanostructures by Modified Co-Precipitation in Pulsed Mode

2015 ◽  
Vol 752-753 ◽  
pp. 148-153
Author(s):  
M.M. Nassar ◽  
Taha Ebrahiem Farrag ◽  
M.S. Mahmoud ◽  
Sayed Abdelmonem
Keyword(s):  
Particle Size ◽  
Calcium Carbonate ◽  
Rotation Speed ◽  
Average Particle Size ◽  
Calcium Nitrate ◽  
Precipitation Method ◽  
Average Particle ◽  
X Ray ◽  
Co Precipitation ◽  
Pulsed Mixing

Calcium carbonate nanoparticles and nanorods were synthesized by precipitation from saturated sodium carbonate and calcium nitrate aqueous solutions through co precipitation method. A new rout of synthesis was done by both using pulsed mixing method and controlling the addition of calcium nitrate. The effect of the agitation speed, and the temperature on particle size and morphology were investigated. Particles were characterized using X-ray Microanalysis, X-ray analysis (XRD) and scanning electron microscopy (SEM). The results indicated that increasing the mixer rotation speed from 3425 to 15900 (rpm) decreases the average particle size to 64±7 nm. A rapid nucleation then aggregation induced by excessive shear force phenomena could explain this observation. Moreover, by increasing the reaction temperature, the products were converted from nanoparticle to nanorods. The maximum attainable aspect ratio was 6.23 at temperature of 75°C and rotation speed of 3425. Generally, temperature raise promoted a significant homoepitaxial growth in one direction toward the formation of calcite nanorods. Overall, this study can open new avenues to control the morphology of the calcium carbonate nanostructures.

Preparation of Tetracalcium Phosphate and the Effect on the Properties of Calcium Phosphate Cement

2009 ◽  
Vol 610-613 ◽  
pp. 1356-1359 ◽  
Author(s):  
Dan Kai ◽  
Hong Song Fan ◽  
Dong Xiao Li ◽  
Xiang Dong Zhu ◽  
Xing Dong Zhang
Keyword(s):  
Particle Size ◽  
Calcium Phosphate ◽  
Calcium Phosphate Cement ◽  
Preparation Method ◽  
Precipitation Method ◽  
Improve Performance ◽  
Solid Reaction ◽  
Tetracalcium Phosphate ◽  
Fast Cooling ◽  
Co Precipitation

In the present study, three types of tetracalcium phosphate (TTCP) were prepared by solid-solid reaction or co-precipitation method and by different cooling modes. The effect of TTCP on the performance of calcium phosphate cement (CPC) was investigated. The result showed that the characteristic of TTCP varied with preparation method and played an important role in CPC performance. A solid-solid reacted TTCP yielded smaller particle size and resulted in bad workability and mechanical strength of CPC. The fast cooling of sintering TTCP by liquid nitrogen could avoid the decomposition of TTCP and make pure TTCP. TTCP prepared by wet-precipitation could improve performance of CPC and was promising to optimization of CPC.

Effect of Surfactant on the Preparation of Nano-powder for Yb Doping Laser Transparent YAG Ceramic

2013 ◽  
Vol 32 (5) ◽  
pp. 511-515 ◽  
Author(s):  
Xiao Guo Cao ◽  
Jia Wang ◽  
Qi Bai Wu ◽  
Hai Yan Zhang
Keyword(s):  
Particle Size ◽  
Polyethylene Glycol ◽  
Average Particle Size ◽  
Ammonium Bicarbonate ◽  
Spherical Particles ◽  
Precipitation Method ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Nano Powder ◽  
Co Precipitation

AbstractYb:YAG transparent ceramic nano-powder was prepared by chemical co-precipitation method, with ammonium bicarbonate as the precipitant and polyethylene glycol as surfactant. The addition of polyethylene glycol can reduce the agglomeration and particle size of the prepared Yb:YAG powder. The morphology, thermal stability and phase structure of Yb:YAG nano-powder were charactered by scanning electron microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. The results show that well-crystallized nano-powder was obtained by calcining the precursors at 900 °C for 3 h. The average particle size of Yb:YAG powder is about 100–200 nm. When the volume amount of polyethylene glycol is 2.0%, well-dispersed Yb:YAG powder with spherical particles of 100 nm diameter was obtained.

scholarly journals Investigation on Variables Contributing to the Synthesis of C-S-H/PCE Nanocomposites by Co-Precipitation Method

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7673
Author(s):  
Ziyang You ◽  
Jing Xu
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Precipitation Method ◽  
Synthesis Process ◽  
Orthogonal Experimental Design ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Ultra Fine Particle ◽  
Early Performance ◽  
Co Precipitation

The usage of nanoscale calcium silicate hydrate (nano C-S-H) proved to have an excellent promotion effect on the early performance of concrete as nano C-S-H with ultra-fine particle size can act as seeding for cement hydration. Therefore, it is of importance to tune the particle size during the synthesis process of nano C-S-H. In this paper, the influence of several variables of the particle size distribution (PSD) of nano C-S-H synthesized by chemical co-precipitation method with the aid of polycarboxylate (PCE) was studied by orthogonal experimental design. In addition, the composition, microstructure, and morphology of the C-S-H/PCE nanocomposites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectrum. The results showed that the concentration of reactants had a significant impact on the PSD of C-S-H/PCE nanocomposites, followed by the dosage of dispersant. Ultrasonic treatment was effective in breaking the C-S-H/PCE aggregates with unstable agglomeration structures. The change in synthetic variables had a negligible effect on the composition of the C-S-H/PCE nanocomposites but had a significant influence on the crystallinity and morphology of the composites.

scholarly journals Structural, Magnetic and Electronic Properties of Nanostructured Magnetic Materials

2021 ◽  
Author(s):  
◽  
Tushara Prakash
Keyword(s):  
Particle Size ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
Arc Discharge ◽  
Superparamagnetic Nanoparticles ◽  
Precipitation Method ◽  
Verwey Transition ◽  
Electrostatic Charging ◽  
Saturation Moment ◽  
Co Precipitation

<p>This thesis was motivated by the different properties exhibited by magnetic nanoparticles when compared with the bulk. For example the coercivity and magnetocrystalline anisotropy vary with the particle size and the finite particle size can affect the spin-wave dispersion. When the nanoparticle radius becomes small enough it is possible to observe superparamagnetism with negligible hysteresis. The transport properties can also be different in nanoparticle composites when compared with the bulk. It is particularly interesting if the nanoparticles have a degree of electronic spin polarization because it is then possible to observe spin-dependent tunnelling. This thesis reports the results from a study of the structural, magnetic, and electronic properties of two partially electronically spin-polarized nanostructured compounds, iron-nickel alloy and magnetite, that were made using a new arc-discharge method, ion implantation and annealing, and a co-precipitation method.  It was found that permalloy powders could be made by arc-discharge where there were a range of particle sizes from nms to 10s of microns. Magnetoresistance was observed where it is due to the ordinary magnetoresistance and spin-dependent tunnelling between the particles. It was also possible to make magnetite using the arc-discharge process and the powders contained nanoparticles, large faceted nanoparticles, and larger particles in the 10s of micron range. The temperature dependence of the saturation magnetization changes at 127 K, which can be attributed to the charge-ordering Verwey transition. A large magnetoresistance was observed and attributed to spin-dependent tunnelling between the magnetite particles. It was less than predicted due to a spin-disordered interfacial region. The electrical resistance was modelled in terms of small nanoparticles coating the larger particles and electrostatic charging during tunnelling between small nanoparticles. Magnetite powders were also synthesized via a chemical co-precipitation method where nanoparticles with diameters of ~14 nm were observed. The Verwey transition was only observed in the zero-field cooled field-cooled magnetization for the arc-discharge powders. It was observed for the magnetite powders made using both methods in the temperature dependence of the saturation moment. The saturation magnetic moment for powders made using both methods has a power law dependence on temperature with an exponent of 3/2 at low temperatures and a higher value above the Verwey transition temperature 2. There was also a large magnetoresistance due to spin-dependent tunnelling for magnetite nanoparticle made using a chemical co-precipitation method and the electrical resistance could be modelled in terms of electrostatic charging during tunnelling.  NixFe₁₋x nanoparticles were made for the first time by ion beam implantation. Small superparamagnetic nanoparticles occurred after implantation. The saturation moment after implantation did not follow the Bloch’s T³/² for x=0.82, which is likely to be due to spin-waves propagating in the nanoparticle/NiyFe₁₋ySizOn matrix. A bi-modal particle size distribution of mostly spherical nanoparticles was observed for x=0.82 after annealing. An x=0.45 sample showed large asymmetric NixFe₁₋x nanoparticles with minimal smaller nanoparticles. The different nanoparticle morphologies is likely to be due to the different nucleation centres and the different initial concentration profiles. The saturation moment had an exponent of 3/2 at low temperatures and there was a contribution from surface disordered spins. A higher Ni fluence with x=0.53 lead to the formation of superparamagnetic nanoparticles that had a higher blocking temperature, indicating the formation of larger nanocrystallites. There was an enhancement in the permeability.</p>

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