Characterization of lattice defects by means of a double crystal diffractometer

1986 ◽  
Vol 175 (3-4) ◽  
Author(s):  
W. Fiedler ◽  
Mai Zhenhong
Keyword(s):  
Hydrogen Atmosphere ◽  
Sample Heat ◽  
Double Crystal ◽  
Cluster Radius ◽  
Silicon Crystals ◽  
Heat Treated ◽  
Different Temperatures ◽  
The Mean ◽  
Double Crystal Diffractometer

AbstractSilicon crystals grown in a hydrogen atmosphere were heattreated at different temperatures. With the aid of a double-crystal diffractometer rocking curves of the specimen were recorded. Only the sample heat-treated at 1000°C showed significant diffuse scattering due to clustering of hydrogen. The mean cluster radius was determined.

scholarly journals Influence of Different Pretreatments on the Structure and Hydrolysis Behavior of Bamboo: A Comparative Study

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2570 ◽  
Author(s):  
Xuemin Qi ◽  
Jie Chu ◽  
Liangliang Jia ◽  
Anuj Kumar
Keyword(s):  
Lignin Content ◽  
Crystallinity Index ◽  
Cellulose Fibers ◽  
Fiber Bundles ◽  
Wet Chemistry ◽  
Naoh Pretreatment ◽  
Different Temperatures ◽  
Bamboo Fibers ◽  
The Mean

In the present study, three pretreatments of sodium hydroxide (NaOH), sulfuric acid (H2SO4), and glycerin were employed with bamboo fibers at two different temperatures of 117 °C and 135 °C, respectively. The chemical composition and structural characterization of the pretreated bamboo fibers were comparatively studied using spectroscopic and wet chemistry methods. Furthermore, the comparative hydrolysis behaviors of pretreated bamboo were studied due to the synergistic interaction between cellulases and xylanase. The NaOH treatment increased the holocellulose contents to 87.4%, and the mean diameter of the cellulose fibers decreased from 50 ± 5 µm (raw fiber bundles) to 5 ± 2 µm. The lignin content and the degree of cellulose polymerization both decreased, while the crystallinity index of cellulose and thermostability increased. The hydrolysis yields of NaOH pretreated bamboo at 135 °C increased from 84.2% to 98.1% after a supplement of 0.5 cellulose to 1 mg protein/g dry xylan. The NaOH pretreatment achieved optimal enzymatic digestibility, particularly at higher temperatures as indicated by the results.

Synthesis and Characterization of an Experimental Zn-Hydroxyapatite Powders with Application in Dentistry

2013 ◽  
Vol 587 ◽  
pp. 43-51 ◽  
Author(s):  
Doina Prodan ◽  
Marioara Moldovan ◽  
Cristina Prejmerean ◽  
Laura Silaghi-Dumitrescu ◽  
Stanca Boboia ◽  
...  
Keyword(s):  
Size Distribution ◽  
Nanometer Scale ◽  
Size Distributions ◽  
Sem Images ◽  
X Ray ◽  
Microstructural Parameters ◽  
Heat Treated ◽  
Different Temperatures ◽  
Adsorption Desorption

In the present study, Zn-hydroxyapatite (Zn-HA) was synthesized, the powder was thermally treated at different temperatures and then characterized. The Zn-HA powder was characterized mainly by FTIR and XRD, but have been performed investigations like SEM, BET and size distribution. The addition of ZnO in hydroxyapatite causes alleged interactions with the existing groups in HA, which amend the corresponding signals to these groups in the IR spectra. X-ray diffractograms for samples (untreated and heat-treated) have been recorded and microstructural parameters for the all samples have been calculated. The obtained average sizes of the crystallites and the network tensions support the idea that Zn-HA powders are nanostructured. The SEM images and size distributions for Zn-HA indicate a cluster of crystals with nanometer-scale of the population-base. Was determined the adsorption-desorption isotherms for Zn-HA powder at 100 o C and 800 o C. The dates obtained from the analysis of particle size distribution indicates for the Zn-HA powder an size distribution for granules in the range from 0.05 to 0.3μm

Preparation and Characterization of Tungsten Trioxide (WO3) Thin Films

2013 ◽  
Vol 678 ◽  
pp. 32-36 ◽  
Author(s):  
Raveendran Lavanya ◽  
Gandhimathinathan Saroja ◽  
Veerapandy Vasu
Keyword(s):  
Thin Films ◽  
Electron Beam Evaporation ◽  
Glass Substrates ◽  
Heat Treated ◽  
Electron Beam Evaporation Technique ◽  
Different Temperatures ◽  
Evaporation Technique ◽  
Crystalline Nature ◽  
Wo3 Thin Films

The thin films of WO3were prepared on cleaned microscopic glass substrates by the electron beam evaporation technique. The films were coated at room temperature using pure WO3pellets as source. The prepared films were further post heat treated at different temperatures (100°C to 350°C) for about 1hr in air. The optical properties of WO3 thin films were studied in detail. The increase in the density of the film as the annealing temperature increases have been confirmed by the transmittance spectra. The film annealed at 250°C shows a strong photoluminescence peak. The peak intensity is found to be less for all other temperature. The observed results were discussed in terms of crystalline nature of WO3.

A 4 Crystal Monochromator for High Resolution Rocking Curves

1987 ◽  
Vol 31 ◽  
pp. 403-408
Author(s):  
Robert W. Green
Keyword(s):  
Bragg Reflection ◽  
Thin Layers ◽  
Double Crystal ◽  
Rocking Curve ◽  
X Ray ◽  
Lattice Constants ◽  
Monochromator Crystal ◽  
Parallel Configuration ◽  
Double Crystal Diffractometer

X-ray characterization of single crystal materials in the form of thin layers can be accomplished with the use of a double crystal diffractometer. The resultant rocking curve is a convolution of the Bragg reflection from both the first and second crystals. The width of the rocking curve at half-height is a measure of the crystal perfection of a materiel. Since the FWHM for the material being analyzed cannot be less than that of the first crystal (Monochromator), the first crystal should be of very good crystal quality. The problem that arises with the two crystal parallel configuration (Fig. 1) is that the monochromator crystal must be changed each time a material of different orientation or stoichiometry with different resultant lattice constants is analyzed. This requires changing the monochromator and re-aligning the double crystal diffractometer.

scholarly journals Synthesis and characterization of sol-gel derived monophasic mullite powder

Cerâmica ◽  
2020 ◽  
Vol 66 (379) ◽  
pp. 307-313
Author(s):  
A. Jana ◽  
D. Ray
Keyword(s):  
Sol Gel ◽  
Grain Morphology ◽  
Precursor Powder ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
X Ray ◽  
Heat Treated ◽  
Different Temperatures

Abstract High-purity microfine mullite precursor powder of stoichiometric chemical composition, 3Al2O3.2SiO2, was synthesized through the sol-gel route using aluminum isopropoxide and tetraethyl orthosilicate. The derived mullite precursor powder was characterized by BET surface area, particle size distribution, Fourier-transform infrared spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy. Phase analysis of the precursor powder and calcined samples at different temperatures was done by XRD. Non-isothermal crystallization kinetics of mullite precursor was studied by TG-DTA in static air using heating rates of 5.0, 7.5, 10.0, 12.5, and 15 K.min-1. Grain morphology was studied by SEM. The results showed that synthesized mullite precursor powder possessed homogeneity of Al and Si components, and the amorphous precursor powder was converted to monophasic mullite crystal when heat-treated at 970 °C. Based on Flynn-Wall-Ozawa and Kissinger equations, the activation energy associated with the crystallization of mullite was determined to be 1189.8 and 1189.0 kJ.mol-1, respectively.

New Methods for the Accurate Comparison of Lattice Parameters

1993 ◽  
Vol 37 ◽  
pp. 123-128 ◽  
Author(s):  
D. K. Bowen ◽  
B. K. Tanner
Keyword(s):  
Lattice Parameter ◽  
Lattice Parameters ◽  
Parameter Determination ◽  
Double Crystal ◽  
New Methods ◽  
Accurate Comparison ◽  
Peak Location ◽  
The Mean ◽  
Rotation Stage ◽  
Double Crystal Diffractometer

AbstractTwo new methods of comparison of lattice parameters are described. The first method uses a double crystal diffractometer, fitted with a specimen rotation stage. Bragg peak positions of a silicon reference and the specimen crystal are recorded for the crystals at 0 and rotated 180° about the diffraction vector. From the mean Bragg positions the lattice parameters can, in principle, be compared to parts in 106. The second method is a variant on the above, using a triple axis diffractometer. It uses a beam conditioner and monochromator to define the incident wavevector ko, and an analyser crystal to define the diffracted wave vector kh. Only the analyser motion must be accurate and stable to the arc second level. We present a detailed error analysis for the case where reference and specimen Bragg angles differ significantly. Peak location to a confidence level of 1 arc second permits absolute, traceable lattice parameter determination to several parts in 106.

Synthesis and Characterization of Si3N4 Nanopowder by RF Induction Thermal Plasma

2017 ◽  
Vol 898 ◽  
pp. 1597-1602 ◽  
Author(s):  
Xuan Zhao ◽  
Hai Yan Chen ◽  
Chen Yang Shu ◽  
Li Hua Dong ◽  
Yan Sheng Yin
Keyword(s):  
Electron Microscopy ◽  
Thermal Plasma ◽  
X Ray Diffraction ◽  
N Source ◽  
Α Phase ◽  
Induction Thermal Plasma ◽  
Transmission Electron ◽  
Heat Treated ◽  
Different Temperatures

Nano-Si3N4 has been synthesized by the thermal plasma with silicon tetrachloride (SiCl4) as the Si source, liquid ammonia (NH3) as the N source, and silane (SiH4) as the catalyst. And the prepared Nano-Si3N4was heat-treated atfour different temperatures of 1350°C, 1400°C, 1450°C, 1500°C. The as-prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The results showed that the particle size of the nano-Si3N4 powder was less than 100 nm and it was amorphous when the temperature below 1450°C. At 1500°C, the synthesized Si3N4 powder with the grain size of 10 nm was crystallized, and the α-phase Si3N4 reached more than 90%.

Characterization of carbides in M50NiL

1991 ◽  
Vol 49 ◽  
pp. 606-607
Author(s):  
L. S. Lin ◽  
K. P. Gumz ◽  
A. V. Karg ◽  
C. C. Law
Keyword(s):  
Temperature Effects ◽  
Base Composition ◽  
Lattice Parameter ◽  
Control Surface ◽  
Carbide Formation ◽  
Particle Sizes ◽  
Low Carbon ◽  
Fee Structure ◽  
Heat Treated

Carbon and temperature effects on carbide formation in the carburized zone of M50NiL are of great importance because they can be used to control surface properties of bearings. A series of homogeneous alloys (with M50NiL as base composition) containing various levels of carbon in the range of 0.15% to 1.5% (in wt.%) and heat treated at temperatures between 650°C to 1100°C were selected for characterizations. Eleven samples were chosen for carbide characterization and chemical analysis and their identifications are listed in Table 1.Five different carbides consisting of M6C, M2C, M7C3 and M23C6 were found in all eleven samples examined as shown in Table 1. M6C carbides (with least carbon) were found to be the major carbide in low carbon alloys (<0.3% C) and their amounts decreased as the carbon content increased. In sample C (0.3% C), most particles (95%) encountered were M6C carbide with a particle sizes range between 0.05 to 0.25 um. The M6C carbide are enriched in both Mo and Fe and have a fee structure with lattice parameter a=1.105 nm (Figure 1).

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