Advanced Process Model for Polymer Pyrolysis and Uranium Ceramic Material Processing

2006 ◽  
Author(s):  
Xiaolin Wang ◽  
Suraj C. Zunjarrao ◽  
Hui Zhang ◽  
Raman P. Singh
Keyword(s):  
Material Processing ◽  
Ceramic Material ◽  
Chemical Reactions ◽  
Process Model ◽  
Uranium Oxide ◽  
Volume Ratio ◽  
Ceramic Materials ◽  
Processing Technique ◽  
Transport Processes ◽  
Polymer Pyrolysis

Silicon carbide (SiC) based uranium ceramic material can be fabricated as hosts for ultra high temperature applications, such as gas-cooled fast reactor fuels and in-core materials. A pyrolysis-based material processing technique allows for the fabrication of SiC based uranium ceramic materials at a lower temperature compared to sintering route. Modeling of the process is considered important for optimizing the fabrication and producing material with high uniformity. This study presents a process model describing polymer pyrolysis and uranium ceramic material processing, including heat transfer, polymer pyrolysis, SiC crystallization, chemical reactions, and species transport of a porous uranium oxide mixed polymer. Three key reactions for polymer pyrolysis and one key reaction for uranium oxide polymer interaction are established for the processing. Included in the model formulation are the effects of transport processes such as heat-up, polymer decomposition, and volatiles escape. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Processing of a sample with certain geometry is simulated. The effects of heating rate, particle size and volume ratio of uranium oxide and polymer on porosity evolution, species uniformity, reaction rate are investigated.

Advanced Process Model for Polymer Derived Ceramic Processing

2006 ◽  
Author(s):  
Xiaolin Wang ◽  
Suraj C. Zunjarrao ◽  
Hui Zhang ◽  
Raman P. Singh
Keyword(s):  
Chemical Reactions ◽  
Process Model ◽  
Transport Phenomena ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Source Material ◽  
Porosity Evolution ◽  
Polymer Precursors ◽  
Polymer Pyrolysis ◽  
Lower Temperature

Pyrolysis of preceramic polymers allows a new type of ceramic materials to be processed at a relatively low temperature. The ceramics via polymer pyrolysis display a number of exceptional mechanical, thermal and chemical properties, including high thermal stability, high oxidation/creep resistance, etc. Moreover, they offer better geometrical accuracy compared to conventional ceramics. In addition, thermal induced pyrolysis of organometallic polymer precursors offers the possibility of net shape manufacturing at a lower temperature compared to traditional powder sintering process. The pyrolysis of polymer precursors involves curing of polymer precursors in which the polymer undergoes cross-linking to form a green body, followed by a pyrolysis stage that involves the formation of amorphous SiC and crystallization of SiC at a higher temperature. The source material changes phase and composition continuously during polymer pyrolysis based ceramic process. Chemical reactions and transport phenomena vary accordingly. To obtain ceramics with high uniformity of microstructure and species without crack, transport phenomena in material processing needs to be better understood and a process model needs to be developed to optimize the fabrication process. In this paper, a numerical model is developed, including heat and mass transfer, polymer pyrolysis, species transport, chemical reactions and crystallization. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Pyrolysis of a sample with certain geometry is simulated. The effects of heating rate, particle size and initial porosity on porosity evolution, mass loss and reaction rate are investigated. Optimal conditions for the manufacturing are also proposed.

Numerical Modeling and Experimental Characterization of the Pyroplasticity in Ceramic Materials during Sintering

2010 ◽  
Vol 62 ◽  
pp. 203-208 ◽  
Author(s):  
Pasquale Bene ◽  
Danilo Bardaro ◽  
Daniela Bello ◽  
Orazio Manni
Keyword(s):  
Ceramic Material ◽  
Ceramic Materials ◽  
Constitutive Law ◽  
Beam Deflection ◽  
Firing Cycle ◽  
Experimental Characterization ◽  
Viscosity Increase ◽  
Ceramic Components ◽  
Deflection Theory ◽  
Sintering Shrinkage

The aim of the work is the study of the pyroplasticity in ceramic materials in order to simulate the deformations of complex ceramic component during sintering. A ceramic material undergoing densification can be treated as a linear viscous material. Generally, the viscosity decreases as the temperature increases, however the densification and the consequent grain growth, result in a viscosity increase. A bending creep test is proposed for measuring the change in viscosity of the ceramic material during densification. Equations, based on beam deflection theory, are derived to determine the viscosity during the whole firing cycle by measuring the deflection in the centre of specimens. In addition, dilatometric analyses are performed to measure the sintering shrinkage and the specimen density, which continuously changes during the sintering process. On the basis of an accurate experimental characterization the parameters of Maxwell viscoelastic constitutive law are derived. A numerical-experimental procedure has been adopted in order to calibrate the numerical model that, finally, has been used to predict the pyroplastic deformations of complex ceramic components.

Silicon Carbide and Uranium Oxide Based Composite Fuel Preparation Using Polymer Infiltration and Pyrolysis

2006 ◽  
Author(s):  
Abhishek K. Singh ◽  
Suraj C. Zunjarrao ◽  
Raman P. Singh
Keyword(s):  
Silicon Carbide ◽  
Uranium Oxide ◽  
Chemical Interaction ◽  
Processing Technique ◽  
Spherical Particles ◽  
Ceramic Yield ◽  
Processing Scheme ◽  
Carbide Matrix ◽  
Silicon Carbide Matrix ◽  
Polymer Infiltration

Ceramic composite pellets consisting of uranium oxide, U3O8, particles in a silicon carbide matrix are fabricated using a novel processing technique based on polymer infiltration and pyrolysis (PIP). In this process, spherical particles of depleted uranium oxide, in the form of U3O8, are dispersed in liquid allylhydridopolycarbosilane (AHPCS), and subjected to pyrolysis up to 900°C under a continuous flow of ultra high purity (UHP) argon. Pyrolysis of AHPCS produces near-stoichiometric amorphous SiC at 900°C. Multiple polymer infiltration and pyrolysis (PIP) cycles are required to minimize open porosity and densify the silicon carbide matrix, in order to enhance the mechanical strength of the material. Structural characterization is carried out after first pyrolysis to investigate chemical interaction between U3O8 and SiC. The physical and mechanical properties are also quantified, and it is shown that this processing scheme promotes uniform distribution of uranium fuel source along with a high ceramic yield of the parent matrix. Furthermore, the processing technique involves lower energy requirements than conventional sintering processes currently in practice.

Application of Meshless Pore-Level Model to Pyrolysis and Synthesis of Nuclear Fuels

2007 ◽  
Author(s):  
Xiaolin Wang ◽  
Hui Zhang ◽  
Lili Zheng
Keyword(s):  
Material Processing ◽  
Transport Phenomena ◽  
Nuclear Material ◽  
Processing Technique ◽  
System Level ◽  
Scale Model ◽  
Nuclear Fuels ◽  
Particle Hydrodynamics ◽  
Level Model ◽  
Pore Level

Uranium-ceramic nuclear fuels can be fabricated through pyrolysis-based materials processing technique. This technique requires lower energy compared to sintering route. During the fabrication process, the source material changes composition continuously and chemical reactions and transport phenomena vary accordingly. Therefore, to obtain such nuclear fuel materials with high uniformity of microstructure/species without crack, transport phenomena in the material processing needs to be better understood. A system-scale model has been developed to account for the pyrolysis-based uranium-ceramic nuclear material processing in our prior work. In this study, a pore-scale numerical model based on Smoothed Particle Hydrodynamics (SPH) will be described for modeling the synthesis of SiC matrix and U3O8. The system-level model provides thermal boundary conditions to the pore-level model. The microstructure and compositions of the produced composites will be studied. Since the control of process temperature plays an important role in the material quality, the effects of heating rate and U3O8 particle size and volume on species uniformity and microstructure are investigated.

Application of Focus-Variation Technique in the Analysis of Ceramic Chips

2019 ◽  
Vol 957 ◽  
pp. 187-194
Author(s):  
Roman Wdowik ◽  
Slawomir Swirad
Keyword(s):  
Machine Tool ◽  
Ceramic Material ◽  
Microscopic Study ◽  
Ceramic Materials ◽  
Software Tools ◽  
Milling Machine ◽  
Focus Variation ◽  
3D Scans ◽  
Physical Phenomena ◽  
Variation Technique

The paper presents the method of a microscopic study of ceramic chips which can be useful in the analysis of physical phenomena regarding machining of ceramic materials. The analyzed chips were obtained on the milling machine tool from the Al2O3 based ceramic material. The measurements were performed using focus-variation technique (FVT). The InfiniteFocus Real3D microscope from Alicona Imaging company was applied. The paper mainly focuses on the methodology of measurements and the application of microscope’s software tools which can be used in the analysis of chips' 3D scans. The conditions of measurement process are discussed on the basis of the results of exemplary measurements of ceramic chips.

scholarly journals Treatment of Soil Contaminated by Mining Activities to Prevent Contamination by Encapsulation in Ceramic Construction Materials

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6740
Author(s):  
Juan María Terrones-Saeta ◽  
Jorge Suárez-Macías ◽  
Antonio Bernardo-Sánchez ◽  
Laura Álvarez de Prado ◽  
Marta Menéndez Fernández ◽  
...  
Keyword(s):  
Ceramic Material ◽  
Contaminated Soil ◽  
Toxic Elements ◽  
Construction Materials ◽  
Well Being ◽  
Ceramic Materials ◽  
Potentially Toxic Elements ◽  
Raw Material ◽  
Mining District ◽  
Different Soils

Mining is an essential activity for obtaining materials necessary for the well-being and development of society. However, this activity produces important environmental impacts that must be controlled. More specifically, there are different soils near new or abandoned mining productions that have been contaminated with potentially toxic elements, and currently represent an important environmental problem. In this research, a contaminated soil from the mining district of Linares was studied for its use as a raw material for the conforming of ceramic materials, bricks, dedicated to construction. Firstly, the contaminated soil was chemically and physically characterized in order to evaluate its suitability. Subsequently, different families of samples were conformed with different percentages of clay and contaminated soil. Finally, the conformed ceramics were physically and mechanically characterized to examine the variation produced in the ceramic material by the incorporation of the contaminated soil. In addition, in this research, leachate tests were performed according to the TCLP method determining whether encapsulation of potentially toxic elements in the soil occurs. The results showed that all families of ceramic materials have acceptable physical properties, with a soil percentage of less than 80% being acceptable to obtain adequate mechanical properties and a maximum of 70% of contaminated soil to obtain acceptable leachate according to EPA regulations. Therefore, the maximum percentage of contaminated soil that can be incorporated into the ceramic material is 70% in order to comply with all standards. Consequently, this research not only avoids the contamination that contaminated soil can produce, but also valorizes this element as a raw material for new materials, avoiding the extraction of clay and reducing the environmental impact.

scholarly journals Effect of LiNbO3 on the Electrocaloric Performance of 0.94BNT-0.06BT Ceramic Materials

2021 ◽  
Author(s):  
Jing Chen ◽  
lei Wu ◽  
Luanfan Duan ◽  
Dongren Liu
Keyword(s):  
Ceramic Material ◽  
Room Temperature ◽  
Ceramic Materials ◽  
Adiabatic Temperature ◽  
Cooling Effect ◽  
Material System ◽  
Temperature Changes ◽  
Cooling Temperature ◽  
Temperature Range

Abstract Considering that the electric refrigeration temperature range of 0.94BNT-0.06BT ceramic materials is 100 ~ 140℃, the electric refrigeration performance of the 0.94BNT-0.06BT ceramic material system was modified by LiNbO3 doping to reduce the cooling temperature. As a result, the refrigeration temperature range of the 0.94BNT-0.06BT ceramic material system was lowered to 25 ~ 80℃, achieving its cooling effect near room temperature, and in this temperature range, the adiabatic temperature changes ∆T > 0.6K.

Preparation of Macroporous Ceramic Materials by Using Aluminium Powder as Foaming Agent

2014 ◽  
Vol 699 ◽  
pp. 336-341 ◽  
Author(s):  
Nurulfazielah Nasir ◽  
Ridhwan Jumaidin ◽  
Hady Efendy ◽  
Mohd Zulkefli Selamat ◽  
Goh Keat Beng ◽  
...  
Keyword(s):  
Ceramic Material ◽  
Reaction Rate ◽  
Porous Alumina ◽  
Porous Ceramic ◽  
Ceramic Materials ◽  
Calcium Sulphate ◽  
Alumina Ceramic ◽  
Deionized Water ◽  
Foaming Agent ◽  
Aluminium Powder

Aluminium powder was used as foaming agent in the production of macro-porous alumina ceramic. The porous ceramic material was developed by mixing an appropriate composition of cement, aluminium powder (Al), alumina (Al2O3), calcium oxide (CaO), gypsum (calcium sulphate dehydrate, CaSO4.2H2O), silica powder and deionized water. Different compositions of porous ceramic were produced at 2wt.%, 3wt.% and 4wt.% of aluminium powder. Their mechanical properties and macro-porosity structural of the porous ceramic material were analysed and compared. It is determined that the optimal properties of porous ceramic material were found at 3wt.% of aluminium powder and degraded drastically at 4wt.%. This phenomenon is due to the chemical reaction between the aluminium powder and DI water in which they form aluminium oxide that promotes the strength of the material but at the same time, more pores are created at higher reaction rate between these two fundamental materials.

Próteses parciais fixas metal free em região posterior – revisão da literatura considerando a longevidade, material cerâmico usado e principais falhas

2021 ◽  
Vol 12 (47) ◽  
pp. 113-125
Author(s):  
Nathalia Silveira Finck ◽  
Juliana da Mota Paiva ◽  
Rafael Dario Werneck ◽  
Mariana Itaborai Moreira Freitas ◽  
Priscilla Santos Guimarães
Keyword(s):  
Ceramic Material ◽  
Ceramic Materials ◽  
Inclusion Criteria ◽  
Electronic Library ◽  
Metal Free ◽  
Significant Difference ◽  
Bibliographical Survey ◽  
Observation Period

This study aimed to present a literature review with data obtained in vitro and in vivo on metal free partial fixed protheses (PFP) in the posterior region, considering the following variables: ceramic material to be used; prosthesis extension; survival or longevity; main failures found, and comparison with the longevity of conventional metaloceramic PFP. A bibliographical survey was carried out using the databases: United States National Library of Medicine (PubMed) and Scientific Electronic Library Online (Sciello) for articles in English and Portuguese from 1998 to 2019. Articles should meet the inclusion criteria, which were articles that contained information that enabled the calculation of PFPs survival and success, articles with a minimum observation period of 3 years, articles that identified the reason of failures, and studies reported since 1998. Sixteen studies met the inclusion criteria and were evaluated comparatively. The survival rate of the PFP’s varies depending on the ceramic material used and the prostheses extension, no significant difference was observed in the relation between the ceramic material used and the connectors size; however, the greater the extension of the prosthesis, the higher must be the connector size. It was concluded that ceramic materials based on zirconia are the ones that have the longest survival. In addition, the main reasons that lead to decreased survival of PFP’s are secondary caries and connector fracture, however, more studies are needed to determine safely which materials and the extent of PFP’s are the most indicated.

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