The Sintering Mixed Powders Behavior of Triuranium Octoxide in Uranium Dioxide

2015 ◽  
Vol 1114 ◽  
pp. 22-28
Author(s):  
Aurica Barbu ◽  
Mihai Ovidiu Cojocaru
Keyword(s):  
Uranium Dioxide ◽  
Surface Defects ◽  
Hydrogen Atmosphere ◽  
Diameter Ratio ◽  
Theoretical Density ◽  
Metallographic Analysis ◽  
Sintering Behavior ◽  
Cold Pressing ◽  
Triuranium Octoxide

The main aim of this research was to study the sintering behavior in hydrogen atmosphere of mixed powders of triuranium octoxide (U3O8) powder in dioxide uranium (UO2) powders. By cold pressing the green pellets of mixed powders of triuranium octoxide in hyper stoichiometric uranium dioxide has density over 40 % UO2 theoretical density (TD). The sintered pellets had a height diameter ratio (H / D) over one and oxygen uranium ratio (O/U) near stoichiometry of uranium dioxide (UO2). The densities of sintered pellets were up to 97% of uranium dioxide theoretical density. The proposed treatment of sintering are function of green pellets density. Increasing the proportion of triuranium octoxide leads to a decrease in the density of the sinter pellets. The pellets made by 100 % of triuranium octoxide not resist to proposed sintering treatment. The metallographic analysis show uniform grains for sinter pellets made by the 30 % mixture of triuranium octoxide in uranium dioxide. This UO2 sinter pellets are without surface defects.

Consolidation Behavior of the Cu-Al2O3 Nanocomposite Powder

2019 ◽  
Vol 822 ◽  
pp. 258-263
Author(s):  
Pu Guang Ji ◽  
Dong Won Lee ◽  
E.S. Vasilyeva
Keyword(s):  
Hot Extrusion ◽  
Hydrogen Atmosphere ◽  
Alumina Content ◽  
Sintering Behavior ◽  
Green Density ◽  
Nanocomposite Powder ◽  
Consolidation Process ◽  
Cold Pressing ◽  
Powder Compacting ◽  
Consolidation Behavior

The consolidation process of agglomerated Cu – γ-Al2O3 composite nanopowder was investigated experimentally. Process includes powder compacting by uniaxial cold pressing, sintering in hydrogen atmosphere, and hot extrusion. The interdependence of alumina content, powder agglomeration, green density of compacts, and isothermal sintering behavior of powders was evaluated.

Sintering behavior and thermal conductivity of graphite flakes/uranium dioxide composites

2021 ◽  
pp. 153106
Author(s):  
Yi Zhong ◽  
Zhenliang Yang ◽  
Qiqi Huang ◽  
Zhiyi Wang ◽  
Yun Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Uranium Dioxide ◽  
Sintering Behavior

scholarly journals Resource-saving preparation of the 38KHGNM steel surface for heading of automobile components

2020 ◽  
Vol 157 ◽  
pp. 01006
Author(s):  
Aleksey Filippov ◽  
German Pachurin ◽  
Diana Goncharova ◽  
Gor Gevorgyan ◽  
Mariia Mukhina ◽  
...  
Keyword(s):  
Surface Defects ◽  
Metal Flow ◽  
Steel Grade ◽  
Metallographic Analysis ◽  
Rolled Stock ◽  
Resource Saving ◽  
Cold Upsetting ◽  
Automobile Components ◽  
Hot Rolled ◽  
Decarburized Layer

To produce high-quality fasteners for motor group components of automobiles it is necessary to follow the increased requirements to calibrated rolled stock in terms of surface defects. Therefore, the goal of this paper is to study the reasons, types and depth of the surface defects on the calibrated rolled stock from steel 38KHGNM Ø 12.0 mm on the basis of the metallographic analysis. Before cold upsetting, the hot-rolled products are subjected to metal flow and removal of unacceptable surface defects by means of expensive turning operation during which the screw cuts and cracks might appear. It has been defined, that the hot-rolled stock from steel, grade 38KHGNM, diameter 12.0 мм has nonuniform mechanical properties, grooves, laps and partial decarburization on the surface. The heat treatment of the rolled stock with a decarburized layer on the surface contributes to its further decarburization. Poor alignment of calibrated stock during its turning at the turning machine does not enable to completely remove the decarburized layer with minimum skinning of rolled stock. It has been shown that the use of rolled stock from steel 38KHGNM with surface defects and unreasonably high decarburized layer on the surface increases its rejection by 8% and raises the consumption of rolled stock for manufacturing of important fasteners for the motor group of automobiles.

Effect of Different Compacting Processes on the Microwave Sintering Behavior of LaNbO4/MoSi2 Composites

2010 ◽  
Vol 148-149 ◽  
pp. 1588-1593
Author(s):  
Yun Long Ai ◽  
Yan Yan Li ◽  
Chang Hong Liu ◽  
Wen He ◽  
Jia Yuan Ding
Keyword(s):  
Microwave Sintering ◽  
Sintered Sample ◽  
Sintering Behavior ◽  
Sintering Process ◽  
Cold Pressing ◽  
Comprehensive Properties ◽  
Sintering Time ◽  
Homogeneous Structures ◽  
Compaction Processes ◽  
Mosi2 Composite

The green bodies of LaNbO4/MoSi2 composite materials were compacted by warm pressing and cold pressing processes, and then the composites were prepared by microwave sintering. Effects of the two different compaction processes on sintering process and sintered samples were analyzed. The results show that the density of the microwave sintered sample by cold pressing (5.599g/cm3) is similar to that of warm pressing (5.593 g/cm3). But cold pressing has some disadvantages, such as longer sintering time, incomplete sintered samples, peeling easily on the surface and delaminating, existing internal stress, having microcrack and impurities, and occurring distortion easily in sintered samples. The samples compacted by warm pressing have higher heating rate in the microwave sintering process, which have more homogeneous structures, no clear microcrack and big cavities, and higher fracture toughness after sintering. Compared with cold pressing, the comprehensive properties of warm pressing are better.

Sintering Behavior of AL2O3 Ceramics Doped with Pre-Sintered NB2O5 and LiF

2020 ◽  
Vol 1012 ◽  
pp. 190-195
Author(s):  
Pedro Henrique Poubel Mendonça da Silveira ◽  
Paulo Roberto Rodrigues de Jesus ◽  
Matheus Pereira Ribeiro ◽  
Sergio Neves Monteiro ◽  
Julio César Soares De Oliveira ◽  
...  
Keyword(s):  
Grain Size ◽  
Theoretical Density ◽  
Sintering Behavior ◽  
Different Temperatures

A study was carried out on the behavior during the sintering of Al2O3 ceramics with pre-sintering of the additives Nb2O5 and LiF at different temperatures. It was observed through XRD and DSC the formation of the LiNb3O8, Nb3O7F and LiNbO3 phases during the pre-sintering of the additive powders and the formation of the LiAl5O8, AlNbO4 phases during the sintering of the samples The samples showed densities around 91% of the theoretical density, and pre-sintered samples showed low growth in grain size.

Low-Temperature Sintering of ZnO–TiO2 Ceramics

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Zhengwei Nie ◽  
Yuyi Lin ◽  
Feixue Wang
Keyword(s):  
Low Temperature ◽  
Vanadium Pentoxide ◽  
Material Properties ◽  
Sintering Temperature ◽  
Theoretical Density ◽  
Sintering Behavior ◽  
Low Temperature Sintering ◽  
Sintering Aid

Vanadium pentoxide (V2O5) was chosen as a sintering aid to lower the sintering temperature of the ZnO–TiO2 system. The effect of V2O5 on the sintering behavior and material properties of ZnO–TiO2 ceramics and cermets made of ZnO–TiO2 ceramics and copper (Cu) was investigated as a function of V2O5 percentage and sintering temperature. Densities and hardness of the specimens were improved with an increase of V2O5 up to 2 wt. %. The sintering temperature of the specimens can be reduced to below 1000 °C. The properties of ZnO–TiO2 ceramics and cermets made from ZnO–TiO2 ceramics and Cu with V2O5 are strongly dependent on the sintering temperature. The density of ZnO–TiO2 ceramics and cermets was increased up to 95%, 90% of theoretical density at 900–920 °C, 960–1000 °C, respectively, for 4 hrs.

Fabrication of Uranium Dioxide Microspheres by Classic and Novel Sol-Gel Processes

2014 ◽  
Vol 1683 ◽  
Author(s):  
A. Deptuła ◽  
M. Brykala ◽  
M. Rogowski ◽  
T. Smolinski ◽  
T. Olczak ◽  
...  
Keyword(s):  
Uranium Dioxide ◽  
National Laboratory ◽  
Sol Gel ◽  
Nitrate Solution ◽  
Hydrogen Atmosphere ◽  
Substantial Improvement ◽  
Complexing Agent ◽  
Reduction Step ◽  
Oak Ridge ◽  
Sol Gel Process

ABSTRACTUranium dioxide (UO2) microspheres were fabricated by two sol-gel processes. First used was a classical process variant, as developed at Oak Ridge National Laboratory, consisting of (1) reduction of commercial uranyl to U(IV) nitrate; (2) preparation of a sol by precipitation of uranium hydroxide, its peptization, and solvent extraction of nitrates; and (3) gelation to microspheres by extraction of water through addition of a dewatered 2-ethyl-1-hexanol emulsion. Substantial improvement in microsphere production was achieved by application of a sol-gel process in which ascorbic acid was used as strong complexing agent. In this method, the reduction step was omitted and uranyl (VI) ascorbate sols/hydroxyl sols were formed from a suspension of either a uranium trioxide or a uranyl nitrate solution. Gelation through water extraction yielded perfect microspheres. Other metals can be easy added to these sols. Thermal treatment of the UO2 microspheres by calcination and reduction in hydrogen atmosphere was designed on the basis of differential thermal analysis and thermogravimetric analysis.

Rarely Occurring Defects on Tinplates

2020 ◽  
Vol 405 ◽  
pp. 234-239
Author(s):  
Peter Vranec ◽  
Slavka Hockicková ◽  
Alicia Mašlejová ◽  
Mária Demčáková ◽  
Lucia Hrabčáková ◽  
...  
Keyword(s):  
Surface Defects ◽  
Steel Substrate ◽  
Substrate Surface ◽  
Rolling Direction ◽  
Base Material ◽  
Metallographic Analysis ◽  
Continuous Annealing ◽  
Foreign Material ◽  
Random Occurrence ◽  
Short Period

This paper deals with rarely occurring defect on the surface of the tinplates produced in the conditions of U. S. Steel Košice, s.r.o. at the cleaning section of the continuous annealing line (CAL), which was caused by burnt. Random occurrence of such surface imperfections was observed within the short period of time (two months) for various continuous annealed tinplate grades, i.e. TH415, TH435 or TH550 with the thickness of the materials in the interval of 0.172 – 0.240 mm. Surface defects caused by burnt (thermal attack) manifested in different ways. Their appearance on the sheet surface was spot with regular or irregular circle shape, as well as line with the length of up to 2 mm oriented not directly in the rolling direction. By observing of the imperfections in scanning electron microscope (SEM) it was found that the surface of the steel substrate was always compact in the defective areas with clearly visible rolling lines. Foreign material, EDS analysis of which revealed that its chemical composition was on the basis of Fe and Cr, was deposited on the surface of the base material. The appearance of the foreign material shape indicated that it was in the liquid state at the time of incidence on the steel substrate surface. Metallographic analysis from the longitudinal metallographic sections through the defective areas revealed that the substrate under the spot defect with regular circle shape had thermally influenced microstructure. Similar manifestations of the microstructure influence were observed for the line defects. In the case of the spot defect with irregular shape, the microstructure of the material was not influenced, what indicated that the particle of liquid metal was solidified at the time of incidence on the plate surface. After revising technical conditions of the cleaning section of CAL, this type of imperfection was suppressed.

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