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.

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.

scholarly journals Radiation Safety for Incineration of Radioactive Waste Contaminated by Cesium

2017 ◽  
Author(s):  
Yu. Veriuzhsky ◽  
O. Hrynko ◽  
V. Tokarevsky
Keyword(s):  
Radioactive Waste ◽  
Chemical Reactions ◽  
Contaminated Soil ◽  
Radiation Safety ◽  
Chemical Properties ◽  
Damage Effect ◽  
Gas Purification ◽  
Physical And Chemical Properties ◽  
Physical And Chemical ◽  
And Chemical Properties

Problems in the treatment of radioactive waste contaminated by cesium nuclides are considered in the paper. Chornobyl experience in the management of contaminated soil and contaminated forests is analyzed in relation to the accident at Fukushima-1. The minimization of release of cesium aerosols into atmosphere is very important. Radiation influence of inhaling atmosphere aerosols polluted by cesium has damage effect for humans. The research focuses on the treatment of forests contaminated by big volumes of cesium. One of the most important technologies is a pyro-gasification incineration with chemical reactions of cesium paying attention to gas purification problems. Requirements for process, physical and chemical properties of treatment of radioactive waste based on the dry pyro-gasification incineration facilities are considered in the paper together with the discussion of details related to incineration facilities. General similarities and discrepancies in the environmental pollution caused by the accidents at Chornobyl NPP and Fukushima-1 NPP in Japan are analyzed.

scholarly journals Augmented Chemical Reactions: 3D Interaction Methods for Chemistry

2013 ◽  
Vol 9 (S8) ◽  
pp. 80 ◽  
Author(s):  
Patrick Maier ◽  
Gudrun Klinker
Keyword(s):  
Augmented Reality ◽  
Chemical Reactions ◽  
Chemical Properties ◽  
Spatial Relations ◽  
Computer Applications ◽  
Degree Of Freedom ◽  
Lower Degree ◽  
3D Interaction ◽  
Input Devices ◽  
Chemistry Students

Supporting chemistry students in learning and researchers in developing and understanding new chemical molecules is a task that is not that easy. Computer applications try to support the users by visualizing chemical properties and spatial relations. Thus far, there mostly exist applications that are controlled by using ordinary input devices as mice and keyboards. But these input devices have one problem: they always try to map a lower degree of freedom to 6-dimensional movements for the location and the orientation of the virtual molecules. Augmented Chemical Reactions is an application that uses Augmented Reality to visualize and interact with the virtual molecules in a direct way. With the introduced 3D interaction methods, the work of students and researchers is tried to be simplified to concentrate on the actual task.

scholarly journals Influence of flue gas components on the chemical properties of the ceramic materials (Co-)Ce0,8Gd0,2−xPrxO2−δ

2011 ◽  
Vol 18 (7) ◽  
pp. 072005 ◽  
Author(s):  
J Schneider ◽  
Ch Semmler ◽  
Ch Kaps ◽  
F Schulze-Küppers ◽  
S Baumann ◽  
...  
Keyword(s):  
Flue Gas ◽  
Chemical Properties ◽  
Ceramic Materials

Research on the Effect of Repairing Anterior Teeth with All-Ceramic Veneer Based on CT Images

2020 ◽  
Vol 10 (4) ◽  
pp. 940-946
Author(s):  
Shuang Liu ◽  
Hui Yan ◽  
Yuehang Gao
Keyword(s):  
Light Transmission ◽  
Chemical Properties ◽  
Ct Scanning ◽  
Ceramic Materials ◽  
Original Data ◽  
Image Method ◽  
Finite Element Software ◽  
Anterior Teeth ◽  
All Ceramic ◽  
Simulation Results

IPS e.maxPress all-ceramic materials have good physical and chemical properties, biocompatibility, light transmission similar to natural teeth and excellent aesthetic properties, so they are widely used in clinical practice. In this study, the anterior porcelain veneer was made by using IPS e.maxPress hot-pressed casting ceramic under the guidance of DSD software aesthetic design, and its clinical aesthetic repair effect and success rate were evaluated, which provided a useful reference for clinical aesthetic restoration work. The original data was obtained by using the medical image method; the DICOM data obtained by CT scanning was input into the reverse engineering software for image processing and data optimization by using the reverse technique to obtain the real tooth and mandible model. The 3D modeling software is used to establish the implant model and the associated tissue model, and the assembly is completed. The finite element software is introduced, the contact type between the tissues is set, and the clinical simulation results are compared to analyze the simulation results. Practice provides a better surgical solution.

Reaction of Elemental Sulfur and Mercaptobenzothiazole

1956 ◽  
Vol 29 (4) ◽  
pp. 1369-1372
Author(s):  
G. A. Blokh ◽  
E. A. Golubkova ◽  
G. P. Miklukhin
Keyword(s):  
Elemental Sulfur ◽  
Active Form ◽  
Chemical Properties ◽  
Intermediate Compound ◽  
Point Of View ◽  
Experimental Fact ◽  
Acceleration Process ◽  
Physico Chemical ◽  
Lower Temperature ◽  
Vulcanization Process

Abstract One of the most important problems in the field of the physics and chemistry of rubber is that of vulcanization. Until now no single theory has been established, which elucidates the complex physico-chemical changes which occur during this process. Still more obscure has been the mechanism of the action of vulcanization accelerators, which, as is well known, not only reduce the time and the temperature of vulcanization, but also influence the physico-mechanical and chemical properties of the rubber. Most investigators have assumed that in the acceleration process a reaction with sulfur converts it to an active form which is capable of bringing about vulcanization at a lower temperature and at a greater rate, than with ordinary elemental sulfur in the absence of an accelerator. This point of view is based on the experimental fact that the vulcanization of rubber by sulfur dioxide and hydrogen sulfide, for example, which form sulfur in the nascent condition, proceeds rapidly even at room temperature. Investigators have also assumed that in the vulcanization process activation of sulfur in the presence of accelerators may occur by different mechanisms. It is possible that the accelerator, reacting with elemental sulfur, forms unstable intermediate compounds, which decompose with liberation of sulfur in an active form. The latter reacts with rubber, and the regenerated accelerator reacts again with elemental sulfur, etc. However, a different process is possible for the activation of elemental sulfur. By this second mechanism the unstable combination of accelerator and sulfur reacts directly with rubber without the formation of active sulfur. Both these mechanisms necessarily assume the formation of intermediate unstable combinations of the accelerator with sulfur. However, direct, experimentally-based demonstrations of such an interaction are lacking in the literature. There exist only theoretical hypotheses concerning the nature of the possible intermediate combination of the accelerator with sulfur. According to Ostromislensky's concepts, further developed by Bedford, such an intermediate compound has the character of a polysulfide. According to Bruni and Romani, this intermediate compound is a disulfide. As is well known, the disulfide theory was placed in doubt by Zaide and Petrov on the basis of data from the vulcanization of rubber in the presence of benzothiazolyl disulfide.

Sign in / Sign up

Export Citation Format

Share Document