• Title/Summary/Keyword: Crystallite Size

Search Result 290, Processing Time 0.026 seconds

The Relation of Crystallite Size and Ni2+ Content to Ferromagnetic Resonance Properties of Nano Nickel Ferrites

  • Lafta, Sadeq H.
    • Journal of Magnetics
    • /
    • v.22 no.2
    • /
    • pp.188-195
    • /
    • 2017
  • The ferromagnetic resonance and other magnetic properties dependence on $Ni^{2+}/Fe^{3+}$ ratio and crystallite size were investigated for nano nickel ferrite ($NiFe_2O_4$). The crystallite size was controlled by controlling the nickel content in the starting material solution. The XRD and TEM were utilized to measure the crystallite size through Scherrer formula and particle size respectively. The most frequent particle sizes were lower than crystallite size, which ranged from 16.5 to 44.65 nm. The general behavior of M-H loop shapes and parameters showed superparamagnetic one. The saturation magnetization had a maximum value at $Ni^{2+}/Fe^{3+}$ molar ratio equal to 0.186. The FMR signals showed, generally, broad linewidths, where the maximum width and minimum resonance field were for the sample of the lowest crystalline size. Furthermore, FMR resonance field shows linear dependence on crystalline size. The fitting relation was estimated to express this linear dependency on the base of behavior coincidence between particle size and the inverse of saturation magnetization. The given interpretations to understand the intercept and the slope meanings of the fitted relation were based on Larmor equation, and inhomogeneous in the anisotropy constant.

Tailoring Porosity of Colloidal Boehmite Sol by Controlling Crystallite Size

  • Park, Myung-Chul;Lee, Sung-Reol;Kim, Hark;Park, In;Choy, Jin-Ho
    • Bulletin of the Korean Chemical Society
    • /
    • v.33 no.6
    • /
    • pp.1962-1966
    • /
    • 2012
  • Boehmite sols have been prepared by crystallization of amorphous aluminum hydroxide gel obtained by hydrolysis and peptization of aluminum using acetic acid. The size of the boehmite crystallites could be controlled by Al molar concentration in amorphous gel by means of controlling grain growth at nucleation stage. The size of boehmite increases as a function of Al molar concentration. With increasing boehmite crystallite size, the $d_{(020)}$ spacing and the specific surface area decreases, whereas the pore volume increases along with pore size. Especially, the pore size of the boehmite sol particles is comparable to the crystallite size along the b axis, suggesting that the fibril thickness along the b axis among the crystallite dimensions of the boehmite contributes to the pore size. Therefore, the physical properties of boehmite sols can be determined by the crystallite size controlled as a function of initial Al concentration.

Crystallite Size Measurement of Uranium Oxide Fuel Powders by Neutron Diffraction (중성자 회절에 의한 산화우라늄 핵연료 분말의 결정크기 측정)

  • 류호진;강권호;문제선;송기찬;최용남
    • Journal of Powder Materials
    • /
    • v.10 no.5
    • /
    • pp.318-324
    • /
    • 2003
  • The nano-scale crystallite sizes of uranium oxide powders in simulated spent fuel were measured by the neutron diffraction line broadening method in order to analyze the sintering behavior of the dry process fuel. The mixed $UO_2$ and fission product powders were dry-milled in an attritor for 30, 60, and 120 min. The diffraction patterns of the powders were obtained by using the high resolution powder diffractometer in the HANARO research reactor. Diffraction line broadening due to crystallite size was measured using various techniques such as the Stokes' deconvolution, profile fitting methods using Cauchy function, Gaussian function, and Voigt function, and the Warren-Averbach method. The non-uniform strain, stacking fault and twin probability were measured using the information from the diffraction pattern. The realistic crystallite size could be obtained after separation of the contribution from the non-uniform strain, stacking fault and twin.

A Study On the Structure and Mechanical Properties of tensioned and non-tensioned annealed PP filaments (긴장 및 무긴장 상태에서 열처리한 PP 필라멘트의 구조 및 역학적 성질에 관한 연구)

  • Lee, Eun-Woo
    • Journal of the Korean Society of Industry Convergence
    • /
    • v.4 no.4
    • /
    • pp.413-418
    • /
    • 2001
  • The change of crystalline structure and mechanical properties of drawn PP filaments which was treated by tensioned and non-tensioned annealing was investigated. Measurements were carried out with XRD for crystallite size, density gradient tube for crystallinity. and UTM for mechanical properties. Tensioend and non-tensioned annealing were carried out $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$: for 10min., 30min., 60min, in oil bath. It was found that the crystallinity and crystallite size of (110) plane of samples were increased with increasing of annealed temperature and time. Also crystallinity and crystallite size of samples which was tensioned annealing were larger than those of non-tensioned annealed samples. Initial modulus and tensile strength of tensioned annealed samples were higher than non-tensioned annealed samples, But elongation of tensioned annealed samples was lower than non-tensioned annealed samples.

  • PDF

Effects of Crystallite Size on Gas Sensitivity and Surface Property of Oxide Semiconductor (산화물 반도체의 결정입도가 가스감도와 표면특성에 미치는 영향)

  • Song, Guk-Hyeon;Park, Sun-Ja
    • Korean Journal of Materials Research
    • /
    • v.3 no.4
    • /
    • pp.319-326
    • /
    • 1993
  • The effects of $SnO_2$ crystallite size on the powder characteristics, the resistance in air and the sensitivity to 0.5 vol % $H_2$, CO-air mixture were observed. The size of SnO, powder was controlled by calcining temperature variation ($500^{\circ}C$ ~$1100^{\circ}C$) of $\alpha$-stannic acid fabricated from $SnCl_4 \cdot xH_2O$. Its crystallite size. evaluated from TEM image, was in the range of 8-54nm. With the reduction of crystallite size, the adsoption peak of $H_2O$ on FTIR curve became more clear while the lattice parameters were invariable. As the crystallite size decreased, with elements of thick film, the temperatures showing a minimum resistance in air and a maximum sensitivity to H, gas reduced. The temperature variations were assigned to the changes of activation energy of the active adsorbates, and it was suggested that the decrease of activation energy can be one of the reasons for the' sensitivity increase with the' fine powder.

  • PDF

A Study On Crystalline Structure Change by Isothermally Annealed after Elevated heating of drawn PP filaments (연신한 PP filament의 승온열처리에 의한 결정구조 변화에 관한 연구)

  • Lee, Eun-Woo
    • Journal of the Korean Society of Industry Convergence
    • /
    • v.3 no.4
    • /
    • pp.345-351
    • /
    • 2000
  • The change of crystalline structure of drawn PP filaments were investigated. Samples were treated by isothermally annealed after elevated heating from $20^{\circ}C$. Measurements were carried out with XRD for crystallite size and density gradient tube for crystallinity. Isothermally heat treatment were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. in dry oven. The isothermal heat treatment after elevated heating from $20^{\circ}C$ were carried out at the temperature of $100^{\circ}C$, $120^{\circ}C$ and $140^{\circ}C$ for 10min., 30min. and 60min. with heating rate of $1^{\circ}C$/min., $5^{\circ}C$/min. and $10^{\circ}C$/min. From the results of this study, it found the following facts. It was found that the crystallinity and crystallite size of (110) plane of sample were increased with increasing of annealed temperature and time. Also crystallinity and crystallite size of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were higher than those of isohtermally annealed samples.

  • PDF

X-ray Diffraction Studies of Poly(aryl ether ether ketone) Fibers with Different Degrees of Crystallinity and Orientation

  • Karacan Ismail
    • Fibers and Polymers
    • /
    • v.6 no.3
    • /
    • pp.206-218
    • /
    • 2005
  • Structural studies of series of 'as spun' and drawn PEEK fibers have been carried out using X-ray diffraction and optical microscopy techniques. The analysis of results suggest that fibers produced at a constant draw ratio with increasing draw temperatures show enhanced orientation and crystalline behaviour. The resolved equatorial and meridional traces provide additional structural parameters in terms of crystallinity, crystallite size, and crystallite thickness. It is concluded that drawing at a temperature below $T_g(i.e.,\;144^{\circ}C)$ results in poorly oriented non-crystalline materials, whereas drawing above $T_g$ results in highly oriented semi crystalline materials. Additional drawing proved to increase the overall orientation with slight improvements in lateral order of the chain molecules. Quantitative analysis revealed that the crystallite size increases with increasing drawing temperature. The results also revealed the increased crystallite size upon additional drawing. Crystalline orientation parameter, $_c$, suggests almost perfect orientation. In all cases, the amorphous orientation is found to be lower than the overall orientation parameter obtained from the optical birefringence. As a result of additional drawing, crystalline orientation was found to increase slightly but the increase in the orientation of non-crystalline material was found to be substantial. An average crystalline density was determined from the orthorhombic unit cell dimensions. It was found to vary as a result of processing conditions. It was also found that the value of the maximum birefringence shows heavy dependence on the chain conformation.

The Change of Crystal Structure of TiO2 Fine Powders by Heat Treatment (열처리에 의한 TiO2 미립자의 결정구조 변화)

  • Kim, S.J.;Chang, G.H.;Jin, Y.C.;Jheong, G.R.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.7 no.1
    • /
    • pp.11-16
    • /
    • 1994
  • Anatase $TiO_2$ particles prepared by experiment were used to study the change of crystal structure by calcination temperature. The results were as follows. Crystallite size of anatase $TiO_2$ particles increased with calcination temperature. The rate of increasing the crystallite size of anatase $TiO_2$ particles was decreased below $700^{\circ}C$ and was markedly increased above $700^{\circ}C$. Unit cell volume of $TiO_2$ was expanded at low temperature and was contracted at high temperature. This result means that the growth of crystallite size was occured in the direction.

  • PDF

Preparation and Characterization of Silicon Carbide Nanofiber (탄화규소 나노섬유의 제조 및 물성)

  • 신현익;송현종;김명수;임연수;이재춘
    • Journal of the Korean Ceramic Society
    • /
    • v.37 no.4
    • /
    • pp.376-380
    • /
    • 2000
  • Carbon nanofibers with an average diameter of 100nm were reacted with SiO vapor generated from a mixture of Si and SiO2 to produce silicon carbide nanofibers at temperature ranging 1200∼1500$^{\circ}C$ under vacuum. The nanofiber reacted at 1200$^{\circ}C$ for two hours consisted of silicon carbide with an average crystallite size of 10-20nm, amorphous silica and a significant amount of unreacted carbon. The surface area of silicon carbide nanofiber, obtained after removal of amorphous silica and unreacted carbon from converted carbon nanofibers at 1200$^{\circ}C$, was as high as 150㎡/g. With increasing reaction temperature to 1500$^{\circ}C$, the surface area was decreased to 14㎡/g. Growth of SiC crystallite size with increasing conversion temperature of carbon nanofiber was confirmed from Scherrer formula using the (111) diffraction line and TEM images of converted carbon nanofibers.

  • PDF

Control of Crystal Phase and Agglomeration of Iron Oxide Nanoparticles in Gas Phase Synthesis

  • Lee, Chang-Woo;Lee, Jai-Sung
    • Proceedings of the Korean Powder Metallurgy Institute Conference
    • /
    • 2006.09a
    • /
    • pp.424-425
    • /
    • 2006
  • The effects of reaction temperature and precursor concentration on the microstructure and magnetic properties of ${\gamma}-Fe_2O_3$ nanoparticles synthesized as final products of iron acetylacetonate in chemical vapor condensation (CVC) were investigated. Pure ${\gamma}-Fe_2O_3$ phase was obtained at temperature above $900^{\circ}C$ and crystallite size of ${\gamma}-Fe_2O_3$ nanoparticles decreased with lowering precursor concentration. Also, the coercivity decreases with decreasing crystallite size of nanopowder. The lowest coercivity was 7.8 Oe, which was obtained from the ${\gamma}-Fe_2O_3$ nanopowder sample synthesized at precursor concentration of 0.3M. Then, the crystallite size of ${\gamma}-Fe_2O_3$ nanoparticles was 8.8 nm.

  • PDF