Characterization of processing pores and their relevance to the strength in alumina ceramics

1999 ◽  
Vol 14 (8) ◽  
pp. 3370-3374 ◽  
Author(s):  
Yao Zhang ◽  
Mineyuki Inoue ◽  
Nozomu Uchida ◽  
Keizo Uematsu
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Power Function ◽  
Optical Microscope ◽  
Strength Distribution ◽  
Alumina Ceramics ◽  
Simple Power Function ◽  
Measured Strength ◽  
Good Agreement

Characterization of bulk defects was successfully accomplished in alumina with a transmission optical microscope. The characterization technique used is based on the fact that many ceramics are essentially transparent. Most defects in this particular ceramic were found to be pore. Their size distribution was found to follow a simple power function. With these characteristics of defects, the strength distribution of the ceramics was calculated with Baratta's model and compared to the measured strength of the ceramics. A good agreement was found between them when the pore was assumed to be accompanied with cracks 4 times the length of the grain size.

Optical characterization of ceramic thin films: Applications in low-temperature solid oxide fuel-cell materials research

2004 ◽  
Vol 19 (2) ◽  
pp. 573-578 ◽  
Author(s):  
B.P. Gorman ◽  
V. Petrovsky ◽  
H.U. Anderson ◽  
T. Petrovsky
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Optical Characterization ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Fuel Cell Materials ◽  
Reflection Spectrophotometry ◽  
Transmission And Reflection ◽  
Good Agreement

Characterization of thin film solid oxide fuel-cell materials can be difficult due to the range of porosities in electrodes and electrolytes as well as the nano-sized pores and particles. In this study, optical characterization techniques such as ultraviolet–visible transmission and reflection spectrophotometry are illustrated as methods for achieving information about the film density from the film refractive index as well as the film thickness. These techniques were used to investigate the sintering process of colloidal CeO2 on sapphire substrates and polymeric precursor-derived ZrO2:16%Y (YSZ) thin films on silicon over the temperature range 400–1000 °C, and the results were compared with traditional characterization techniques such as electron microscopy, profilometry, ellipsometry, and x-ray diffraction line broadening analyses. Most of the techniques were in good agreement with the CeO2 grain size changing from 5–65 nm and the film thickness changing from 0.8–0.5 μm. Comparisons of transmission and reflection spectrophotometry with ellipsometry illustrated that scattering effects from the porous CeO2 films caused an overestimation of the refractive index from ellipsometry, but allowed for accurate grain size measurements from transmission and reflection data. Both techniques were in good agreement during the sintering of the YSZ thin films, with the density changing from 90–100% theoretical after heating between 400 and 800 °C.

Synthesis and Characterization of Nano Crystalline Hydroxyapatite Spheroids Using Anionic Template for Bio Applications

2011 ◽  
Vol 493-494 ◽  
pp. 723-727
Author(s):  
P.Michael SL Shanthi ◽  
M. Ashok ◽  
R.V. Mangalaraja ◽  
T. Balasubramanian
Keyword(s):  
Size Distribution ◽  
Room Temperature ◽  
Precipitation Method ◽  
Uniform Size ◽  
Nano Crystalline ◽  
Co Precipitation ◽  
Anionic Template ◽  
Template Material ◽  
Good Agreement

Nano crystalline Hydroxyapatite (HAp) spheroids of uniform size distribution of diameter ~200 nm have been prepared by co-precipitation method at room temperature. The anionic surfactant SDS has been used as the template material. The calcinated samples were subjected to FTIR and XRD characterizations to confirm the phase of HAp. The Ca/P ratio that has been measured from the EDS spectrum 1.69 has good agreement with the theoretical value. The SEM and TEM images reveal the nano spherical nature and narrow size distribution of the HAp particles, which were good candidates for drug delivery applications.

scholarly journals Contribution to Sandy Site Characterization: Spectro-Directional Signature, Grain Size Distribution and Mineralogy Extracted from Sand Samples

2019 ◽  
Vol 11 (20) ◽  
pp. 2446 ◽  
Author(s):  
Viallefont-Robinet ◽  
Bacour ◽  
Bouvet ◽  
Kheireddine ◽  
Ouhssain ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Optical Sensors ◽  
Optical Measurements ◽  
Small Samples ◽  
Spectral Bands ◽  
Reflectance Factor ◽  
Bidirectional Reflectance Distribution

The characterization of sands detailed in this paper has been performed in order to support the in-flight radiometric performance assessment of space-borne optical sensors over the so-called Pseudo-Invariant Calibration Sites (PICS). Although the physical properties of PICS surface are fairly stable in time, the signal measured from space varies with the illumination and the viewing geometries. Thus, there is a need to characterize the spectro-directional properties of PICS. This could be done on a broad scale, thanks to multi-spectral multi-directional space-borne sensors such as the POLDER instrument (with old data). However, interpolating or extrapolating the spectro-directional reflectance measured from space to spectral bands of another sensor is not straightforward. The hyperspectral characterization of sand samples collected within or nearby PICS could contribute to a solution. In this context, a set of 31 sand samples was compiled. The BiConical Reflectance Factor (BCRF), linked to Bidirectional Reflectance Distribution Function (BRDF), was measured between 0.4 and 2.5 µm, over a half hemisphere when the amount of sand in the sample was large enough and for only a single fixed angular configuration for small samples. These optical measurements were complemented by grain size distribution measurements and mineralogical analysis and compiled together with previously published measurements in the so-called PICSAND database, freely available online.

The Issue of Grain Size Distribution Using Mean Field Models for Dynamic and Post-Dynamic Recrystallization

2016 ◽  
Vol 879 ◽  
pp. 1794-1799 ◽  
Author(s):  
Guillaume Smagghe ◽  
David Piot ◽  
Frank Montheillet ◽  
G. Perrin ◽  
A. Montouchet ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mean Field ◽  
304L Stainless Steel ◽  
Mean Field Model ◽  
Average Grain Size ◽  
Fundamental Equations ◽  
Good Agreement

A mean field model for discontinuous dynamic recrystallization (DDRX) has been developed and chained with a post-dynamic recrystallization (PDRX) model to predict transient and steady-state flow stresses and average grain sizes. Numerical results are compared with experimental data obtained on a 304L stainless steel yielding to a good agreement in terms of average grain size. However an unrealistic grain-size distribution is observed using DDRX, which affects results of the PDRX model. This result is discussed with respect to the fundamental equations of DDRX.

Evaluation of hydraulic conductivity based on grain size distribution parameters using power function model

2018 ◽  
Vol 19 (2) ◽  
pp. 596-602
Author(s):  
Rajat Kango ◽  
Vijay Shankar ◽  
M. A. Alam
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Size Distribution ◽  
Power Function ◽  
Grain Size Distribution ◽  
Specific Weight ◽  
Experimental Investigations ◽  
Function Model ◽  
Earthen Structures ◽  
Distribution Parameters

Abstract Hydraulic conductivity is a parameter dictating groundwater recharge, having dependability on factors related to aquifer properties such as particle size, shape, degree of compaction, grain size distribution and fluid flow properties like viscosity and specific weight. The present study is focused on the effect of the grain size distribution of the particles of the aquifer material on its permeability. In order to investigate variation of permeability with respect to the grain size distribution, experimental investigations are conducted on natural borehole samples and those prepared by mixing borehole samples with known quantities of marble chips within a laminar flow regime. A power function model is developed for the estimation of permeability based on grain size distribution parameters σ (standard deviation) and D50 (median grain size). The results from the developed model show good agreement with experimental data as the values of R2, RMSE and MAE for the model are (0.99, 0.007, 0.005) for 5.08 cm dia., (0.99, 0.005, 0.004) for 10.16 cm dia. and (0.97, 0.004, 0.003) for 15.24 cm dia. permeameters respectively. The developed power function model provides an efficient tool to estimate the yield of wells, seepage below earthen structures and design of filters with reasonable accuracy.

Effect of Applied Pressure of Hip on the Removal of Processing Void in Alumina Ceramics and the Resultant Improvement of Mechanical Property

1991 ◽  
Vol 251 ◽  
Author(s):  
Masayori Miyashita ◽  
Jin-Young Kim ◽  
Nozomu Uchida ◽  
Keizo Uematsu
Keyword(s):  
Hot Isostatic Pressing ◽  
Applied Pressure ◽  
Optical Microscope ◽  
Strength Distribution ◽  
Alumina Ceramics ◽  
High Concentration ◽  
Compaction Process ◽  
Large Size ◽  
Before And After ◽  
Processing Defects

ABSTRACTAlumina ceramics prepared at various processing conditions were subjected to hot isostatic pressing (HIP) to remove processing-originated voids. Transmission optical microscope was used for characterizing voids in specimens before and after HIP, and for understanding the effect of HIP condition on the removal of void. The strengths of all specimens were measured to discuss the relation between void and strength. Voids of large size and high concentration were present in all sintered alumina ceramics. The size and concentration of void increased with decreasing pressure used in powder compaction process. HIP was found to be very effective for removing these voids which are the major processing defects in ceramics. The strength of alumina ceramics increased markedly with decreasing size and concentration of voids. The strength distribution of alumina ceramics was explained in terms of the measured void size distribution.

Grain-size distribution of Italian raw materials for building clay products: a reappraisal of the Winkler diagram

Clay Minerals ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 435-442 ◽  
Author(s):  
M. Dondi ◽  
B. Fabbri ◽  
G. Guarini
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Raw Materials ◽  
New Classification ◽  
X Ray ◽  
Size Characterization ◽  
Good Behaviour ◽  
Hollow Bricks

AbstractThe grain size of raw materials influences their behaviour during the technological process and affects many properties of building clay products. Over the last few years, brickworks have been technologically updated and grain size requirements have been modified to ensure good behaviour during shaping and drying. Therefore, the reference schemes used to assess the suitability of clays, such as the classic Winkler diagram, should be updated.For this purpose, the grain-size distribution of 350 clays currently used in ~240 Italian plants was determined by X-ray monitoring of gravity sedimentation. Raw materials are basically represented by silty clays and clayey silts, while bodies present a narrower grain-size range. With reference to the Winkler diagram, most of the Italian bodies fall within the field of ‘thin-walled hollow bricks’, with no significant differentiation among the various product types.In order to improve the grain-size characterization of bodies, a new classification scheme for Italian raw materials is proposed, based on three ranges: >10 µm, 2-10 µm and <2 µm, respectively. It allows distinction of specific grain-size features of bodies for (a) facing bricks; (b) roofing tiles; and (c) lightweight blocks, paving bricks and hollow slabs.

scholarly journals Characterization of Grain-Size Distribution, Thermal Conductivity, and Gas Diffusivity in Variably Saturated Binary Sand Mixtures

2018 ◽  
Vol 17 (1) ◽  
pp. 180026 ◽  
Author(s):  
T.K.K. Chamindu Deepagoda ◽  
Kathleen Smits ◽  
J.R.R.N. Jayarathne ◽  
Benjamin M. Wallen ◽  
Timothy J. Clough
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Gas Diffusivity

Effects of Deposition Temperature on the Growth Characteristics of CVD SiC Coatings

2008 ◽  
Vol 368-372 ◽  
pp. 846-848 ◽  
Author(s):  
Yan Li Huo ◽  
Yu Feng Chen
Keyword(s):  
Surface Roughness ◽  
Grain Size ◽  
Phase Composition ◽  
Crystallite Size ◽  
Deposition Temperature ◽  
Optical Microscope ◽  
Columnar Structure ◽  
Growth Characteristics ◽  
Sic Coatings

The effects of deposition temperature on the growth characteristics of CVD SiC coatings were investigated. CVD SiC coatings were made by pyrolysis of methyltrichlorosilane (MTS) in hydrogen at a low pressure of 5kPa. The ratio of MTS to hydrogen was 1/12. The deposition temperatures were varied from 1373K to 1503K. Optical microscope and SEM were used to observe the surface morphology and microstructure of the coatings. XRD was used for characterization of the phase composition. Results indicated that the deposition rate and the surface roughness varied with deposition temperature. At 1373K, the deposited grains were mainly equiaxed with the crystallite size of 22 nm. However, when the deposition temperature was 1503K, the SiC grains were mainly showed faceted columnar structure with the crystallite size of 32 nm. Grain size increased with the increase of deposition temperature.

Contribution to a Technological Characterization of Kaolins from Cuba and Brazil

2006 ◽  
Vol 530-531 ◽  
pp. 720-727
Author(s):  
Guillermo Ruperto Martín Cortés ◽  
Wildor Theodoro Hennies ◽  
Francisco Rolando Valenzuela-Díaz
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Simple Description ◽  
X Ray ◽  
The Republic

This paper studies the main well-know technological types of kaolins clays from the Republic of Cuba and compares it with one from Brazil. A simple description from the Cuban geology and from the involved kaolins deposits is showed. The basic characterization of each kind of kaolin, includes, chemical analyzes, grain size distribution, scanning electronic microscopy, X-ray diffraction and X-ray fluorescence for chemicals. For special assays it had conformed, by a simple axis hand press up to 5 t, test bodies, which had been burnt to the temperatures of 950, 1250 and 1450°C. These results include refractory and contraction results.

Sign in / Sign up

Export Citation Format

Share Document