Investigation of the influence of the mode of heat treatment of the initial powder on the efficiency of sintering zirconium ceramics by dilatometry

2021 ◽  
Vol 103 (3) ◽  
pp. 17-24
Author(s):  
S. Shevelev ◽  
◽  
E. Sheveleva ◽  
O. Stary ◽  
Keyword(s):  
Thermal Annealing ◽  
Zirconium Dioxide ◽  
Annealing Temperature ◽  
Average Particle Size ◽  
Average Particle ◽  
Sintered Ceramic ◽  
Tetragonal Modification ◽  
Thermal Sintering ◽  
Powder Compacts ◽  
High Degree

Using methods of synchronous thermal and X-ray structural analyzes applied to zirconium dioxide powders partially stabilized with yttrium obtained by chemical coprecipitation the processes of dehydration of these powders during annealing in air have been investigated. Using the dilatometry method, the regularities of compaction of powder compacts have been investigated with thermal sintering. It was found that the resulting powders mainly consist of the tetragonal modification zirconium dioxide and are nano-sized. The average particle size was 25 nm. The resulting powders are characterized by a high degree of agglomeration. It is shown that an increase in the thermal annealing temperature from 500 to 700ºС leads to partial baking of individual particles inside the agglomerate, and causes the formation of hard agglomerates, the presence of which complicates the processes of compaction and subsequent sintering. The presence of such agglomerates prevents the production of ceramics with high mechanical characteristics: density and porosity. Thermal annealing temperature increase leads to a decrease in the density of the sintered ceramic and a decrease in its hardness.

scholarly journals Influence of Cu on the Improvement of Magnetic Properties and Structure of L10 FePt Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1097
Author(s):  
Luran Zhang ◽  
Xinchen Du ◽  
Hongjie Lu ◽  
Dandan Gao ◽  
Huan Liu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Annealing Temperature ◽  
Reduction Method ◽  
Solid Phase ◽  
Average Particle Size ◽  
Fept Nanoparticles ◽  
Average Particle ◽  
Phase Reduction ◽  
Different Temperatures ◽  
One Step

L10 ordered FePt and FePtCu nanoparticles (NPs) with a good dispersion were successfully fabricated by a simple, green, one-step solid-phase reduction method. Fe (acac)3, Pt (acac)2, and CuO as the precursors were dispersed in NaCl and annealed at different temperatures with an H2-containing atmosphere. As the annealing temperature increased, the chemical order parameter (S), average particle size (D), coercivity (Hc), and saturation magnetization (Ms) of FePt and FePtCu NPs increased and the size distribution range of the particles became wider. The ordered degree, D, Hc, and Ms of FePt NPs were greatly improved by adding 5% Cu. The highest S, D, Hc, and Ms were obtained when FePtCu NPs annealed at 750 °C, which were 0.91, 4.87 nm, 12,200 Oe, and 23.38 emu/g, respectively. The structure and magnetic properties of FePt and FePtCu NPs at different annealing temperatures were investigated and the formation mechanism of FePt and FePtCu NPs were discussed in detail.

FABRICATION AND CHARACTERIZATION OF AQUEOUS SOL–GEL-DERIVED LaFeO3 THIN FILMS

2000 ◽  
Vol 14 (22n23) ◽  
pp. 801-808 ◽  
Author(s):  
M. RAJENDRAN ◽  
M. GHANASHYAM KRISHNA ◽  
A. K. BHATTACHARYA
Keyword(s):  
Thin Films ◽  
Single Phase ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Average Particle Size ◽  
Optical Transmittance ◽  
Dip Coating ◽  
Correlation Spectroscopy ◽  
Average Particle ◽  
X Ray

A novel all-inorganic aqueous sol–gel process has been developed to fabricate LaFeO3 thin films by dip-coating. Stable, positively charged colloidal sol particles of hydrous lanthanum ferrite with an average particle size (Z av ) of 7 nm were prepared and coated onto quartz plates under controlled conditions. The sols have been characterized using photon correlation spectroscopy (PCS) for Z av and size distribution. The redispersible gel was characterized by thermogravimetric and differential thermal analysis (TG-DTA) and also by isothermal heating followed by X-ray diffraction to identify the reaction sequence to form LaFeO 3. The sol–gel films as deposited were X-ray amorphous on heating up to 500°C, partially crystalline at 600°C, fully crystalline and single phase at 650°C and above. These films were continuous, polycrystalline, single phase, had uniform thickness in the range between 180 to 1000 nm, depending on deposition conditions, and showed about 80% optical transmittance. The optical band gap varied from 2.7 to 3.3 eV as a function of the annealing temperature. The refractive index increased with increase in annealing temperature from 1.55 at 500°C to 1.86 at 800°C.

scholarly journals STUDY OF PHASE FORMATION IN FE2O3-ND2O3→NDFEO3/FE2O3 NANOCOMPOSITES AS A RESULT OF THERMAL ANNEALING

2021 ◽  
Vol 78 (3) ◽  
pp. 43-50
Author(s):  
K.B. Egizbek ◽  
◽  
K.K. Kadyrzhanov ◽  
◽  
Keyword(s):  
Thermal Annealing ◽  
Targeted Drug Delivery ◽  
Annealing Temperature ◽  
Synthesis Method ◽  
Planetary Mill ◽  
Initial State ◽  
Spinel Type ◽  
Magnetic Devices ◽  
Magnetic Carriers ◽  
Thermal Sintering

The aim of this work is systematic study of the thermal annealing effect on the preparation of nanostructured composites NdFeO3/Fe2O3 with a spinel type structure. The interest in these nano­composites is due to the enormous potential of their application as a basis for magnetic devices, catalysts, and magnetic carriers for targeted drug delivery. As a synthesis method, two­stage syn­thesis was used, which includes mechanochemical grinding of nanopowders Fe2O3 and Nd2O3 in a planetary mill, followed by thermal annealing of the resulting mixture in a wide temperature range: 600­1000°C. During the studies carried out, it was found that in the initial state the obtained nano­composites are a mixture of a solid solution of interstitial and substitutional Fe2O3 and Nd2O3. At an annealing temperature of 600°C, the onset of the formation of the NdFeO3 phase is observed, which at a temperature of 1000°C is fully formed and dominates in the composite structure (content more than 85%). It was also found that during thermal sintering, the processes of phase transformations of the Fe2O3­Nd2O3→NdFeO3/Fe2O3 type are accompanied by an increase in the particle size by a factor of 1.5­2

SYNTHESIS OF YTTRIA-STABILIZED CUBIC ZIRCONIA NANOCRYSTALS BY ULTRASONIC–MICROWAVE ROUTE

NANO ◽  
2010 ◽  
Vol 05 (05) ◽  
pp. 271-277 ◽  
Author(s):  
JIAN-DONG WANG ◽  
CHONG-XIAO LUO ◽  
JIN-KU LIU ◽  
YI LU ◽  
GUANG-MING LI
Keyword(s):  
Average Particle Size ◽  
Degree Of Crystallinity ◽  
Average Particle ◽  
Stabilized Zirconia ◽  
Uniform Size ◽  
X Ray ◽  
Microwave Assisted ◽  
Transmission Electron ◽  
High Degree ◽  
Microwave Assisted Method

The yttria-stabilized zirconia (YSZ) nanocrystals with uniform size, high purity, and high degree of crystallinity, were prepared by ultrasonic–microwave-assisted method. The structure, optical properties and morphologies of YSZ nanocrystals were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, UV–vis absorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The SEM and TEM images of the YSZ nanocrystals indicate that the product is a mono-dispersion structure with an average particle size of about 25 nm.

scholarly journals Structure and dielectric behaviour of Sr-modified Bi4Si3O12 thin films prepared via sol gel method

2018 ◽  
Vol 12 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Abbas Sadeghzadeh-Attar ◽  
Saeid Hajijafari-Bidgoli ◽  
Mohammad Bafandeh
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Loss ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Average Particle Size ◽  
Average Particle ◽  
Sem Images ◽  
Gel Method ◽  
Sol Gel Method

Bismuth silicate (Bi4Si3O12, BSO) nanostructured films containing 0,1,2, and 3mol% Sr were prepared via sol-gel method and annealed at different temperatures up to 700?C. The effects of Sr content on the structure and morphology of prepared films were investigated. SEM images showed that surfaces of the prepared films were dense, smooth and homogeneous. The average particle size was changed from 30 to 35 nm as the annealing temperature was increased from 500 to 700?C. Variation of the dielectric constant and dielectric loss as a function of frequency and annealing temperature for the synthesized thin films with different content of Sr were also studied. The dielectric constant and dielectric loss decrease with Sr addition, and reach the minimum for the sample containing 2mol% Sr. These changes could be attributed to the crystal structure and formation of secondary phases.

Sintering diagrams of titanium powders

2020 ◽  
pp. 5-9
Author(s):  
M. I. Alymov ◽  
◽  
S. I. Averin ◽  
S. V. Semichev ◽  
◽  
...  
Keyword(s):  
Melting Temperature ◽  
Volume Diffusion ◽  
Average Particle Size ◽  
Relative Size ◽  
The Other ◽  
Average Particle ◽  
Powder Sintering ◽  
Titanium Powders ◽  
Sintering Mechanisms ◽  
Powder Compacts

Sintering of powder compacts can lead to an increase in their density, with the neck between the particles growing. Powder sintering diagrams are constructed in coordinates: the relative size of the particles radius (the size of the neck between the sintered particles divided by the particle radius) and the homological melting temperature of the material. To build sintering diagrams, it is necessary to solve a system of pairs of velocity equations for the existing sintering mechanisms. The solution gives the equations of the boundaries separating the regions on the graph “relative radius of the particles – homological temperature”, in which the sintering rate by one mechanism is greater than the other. At these boundaries, the two selected sintering mechanisms make equal contributions to the growth rate of the neck between particles. Sintering diagrams of titanium powders of various dispersions were built (with an average particle size of 0,1 mkm, 1 mkm, 5 mkm and 10 mkm.). The sintering diagrams show that the dominant mechanisms of the sintering of titanium micro- and nanopowders in the temperature range 0,6 – 0,9 absolute melting temperature are surface diffusion from the surface and volume diffusion of the substance from the sources at the boundaries of grains.

scholarly journals SIZE-DEPENDENT FERROMAGNETISM AND ITS AGING BEHAVIOR IN PURE Y2O3 NANOPARTICLES

2013 ◽  
Vol 27 (05) ◽  
pp. 1350031
Author(s):  
ZHONG HUA ZHU ◽  
DA QIANG GAO ◽  
ZHAO LONG YANG ◽  
JING ZHANG ◽  
ZHEN HUA SHI ◽  
...  
Keyword(s):  
Room Temperature ◽  
Annealing Temperature ◽  
Room Temperature Ferromagnetism ◽  
Average Particle Size ◽  
Average Particle ◽  
Heating Effect ◽  
Aging Behavior ◽  
Size Dependent ◽  
Oxygen Defects ◽  
Vacuum Heating

A series of Y 2 O 3 nanoparticles of average particle size 19–37 nm are synthesized by a glycine-nitrate method. Room temperature ferromagnetism is observed in all samples. The magnetization of these samples decreases with increasing annealing temperature, showing a size-dependent ferromagnetism. Vacuum-heating effect on the ferromagnetism is also investigated, which indicates that the observed ferromagnetism is possibly associated with oxygen defects. Interestingly, an aging behavior of the ferromagnetism is observed when the sample is exposed to air or immersed in ethanol. These results further support the oxygen-vacancy-mediated ferromagnetism mechanism.

Evolution of Microstructure, Precipitate and Magnetic Properties with the Different Annealing Temperature in High Grade Nonoriented Electrical Steels

2013 ◽  
Vol 416-417 ◽  
pp. 1645-1651 ◽  
Author(s):  
Tie Ye ◽  
Cheng Zhou ◽  
Zhen Yu Gao
Keyword(s):  
Magnetic Properties ◽  
Magnetic Induction ◽  
Annealing Temperature ◽  
Average Particle Size ◽  
Second Phase ◽  
Average Particle ◽  
High Grade ◽  
Final Annealing ◽  
Electrical Steels ◽  
Evolution Of Microstructure

The evolution of microstructure, precipitate and magnetic properties in nonoriented electrical steels with different annealing temperature was studied. The iron loss of steel decreases with an increase in the final annealing temperature ranging from 800~900°C. This phenomenon is associated with grains recovery; recrystallization and grains grow up with the temperature increasing. Grain size continues to increase, but the average particle size decreases and particle density increases at 880~900°C which show precipitates have dissolved. It approved that the dissolution process of a lot of precipitates occurred after grains growing up. Precipitates are mainly of the second phase particles MnS and AlN. The magnetic induction increased firstly at 800~880°C and then increasing at 880~900°C.It can be found that the proportion of the texture for [{100} +Gos/ {111} at 900°C is higher than that at 880°C and the proportion of Gauss texture is higher at 900°C than that at 880°C. Gauss texture in high grade silicon steel plays an important role which promotes magnetic induction to increase.

Synthesis of dense β, β″–alumina ceramics by reaction sintering of Na2O-containing alumina compact

1991 ◽  
Vol 6 (3) ◽  
pp. 585-591 ◽  
Author(s):  
Yoshihiro Hirata ◽  
Takeshi Izaiku ◽  
Yoshimi Ishihara
Keyword(s):  
Phase Change ◽  
Low Temperatures ◽  
Average Particle Size ◽  
Colloidal Suspensions ◽  
Liquid Phase Sintering ◽  
Alumina Powder ◽  
Average Particle ◽  
Reaction Sintering ◽  
Controlled Structure ◽  
Powder Compacts

Reaction sintering in the Na2O–MgO–Al2O3system was studied with α–alumina green compacts containing Na2O and MgO in the pores of a controlled structure to produce β, β″–alumina polycrystalline at low temperatures. HCOONa and (CH3COO)2Mg were infiltrated into the alumina powder compacts (average particle size 0.2 μm) with relative densities of 51 to 66% at the compositions of Na2O/MgO/Al2O3= 1/0.10/4.0–7.6. The alumina powder compacts were formed by filtration of the aqueous colloidal suspensions through gypsum molds. Phase change from α to β, β″–alumina proceeded fast at low temperatures in the samples with high Na2O/Al2O3ratios. However, no significant densification occurred below 1500 °C owing to the volume increase of powder compacts associated with the phase change of α to β, β″–alumina. At 1600 °C, the green compacts were rapidly densified to relative densities above 99%. This densification was related to the liquid phase sintering based on the partial decomposition of β″–alumina. The dense β, β″–alumina polycrystalline consisted of needle-like grains of 2–5 μm in length and 1–2 μm in width.

DOPANT EFFECTS ON THE STRUCTURAL, OPTICAL AND ELECTRICAL TRANSPORT PROPERTIES IN SrTi1-xCoxO3 NANOPARTICLES SYNTHESIZED BY SOL–GEL METHOD

2010 ◽  
Vol 19 (02) ◽  
pp. 219-227
Author(s):  
DOAN THI THUY PHUONG ◽  
NGUYEN VAN MINH
Keyword(s):  
Transport Properties ◽  
Electrical Transport ◽  
Annealing Temperature ◽  
Dopant Concentration ◽  
Sol Gel ◽  
Average Particle Size ◽  
Average Particle ◽  
Electrical Transport Properties ◽  
Gel Method ◽  
Sol Gel Method

We investigate effects of Co dopant concentration on the structure, as well as optical and electrical transport properties in SrTi 1-x Co x O 3 (x = 0.00, 0.10, 0.20, 0.30, 0.40, 0.50) nanoparticles prepared by sol–gel method with annealing temperature considerably lower than that employed conventionally. The dopant-induced changes are studied by XRD, Raman, Optical absorption and Impedance measurements. The results show an average particle size of about 30 nm, and decreasing lattice parameters. In the Raman spectra, a broad structure in the region 200–500 cm-1 is almost absent and the peaks in the region 600–800 cm-1 show different relative weights with respect to those from SrTiO 3, which is related to structural changes, decreasing gap with increasing dopant concentration in conjuction with increasing grain boundary contribution to the impedance. These results also demonstrate the feasibility of synthesizing the compound with low annealing temperature.

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