A Microscopic Model of the Asymmetric Neck Growth during Sintering Process upon the Asymmetric Particle Arrangement

2011 ◽  
Vol 327 ◽  
pp. 66-71
Author(s):  
Yu Niu ◽  
Feng Xu ◽  
Xiao Fang Hu ◽  
Yong Cun Li ◽  
Jing Zhao ◽  
...  
Keyword(s):  
Growth Rate ◽  
Contact Area ◽  
Monte Carlo Model ◽  
Traditional Theory ◽  
Sintering Process ◽  
Sphere Model ◽  
Particle Rotation ◽  
Neck Growth ◽  
Neck Size ◽  
Particle Arrangement

A kinetic Potts Monte Carlo model was used to investigate the microstructural evolution of a three particles configuration during sintering. The a series of peculiar phenomena was observed and analyzed quantitatively, which indicated that even if the particle shape and the contact area are both completely symmetrical, the asymmetric neck growth will arise due to a special particle arrangement. Although the linear relationship between neck size logarithm and time logarithm was consistent with the traditional theory, a slower neck growth rate comparing with that of the two sphere model displayed a result of the asymmetric neck growth. The analysis of the particle rotation was made to confirm the occurrence of the asymmetric neck growth. It was firstly observed that the morphology of the grain boundaries became bevel, and the reason for this morphology was discussed. All the special phenomena have proved that the asymmetric particle arrangement about the contact area can trigger the unstable neck growth.

scholarly journals Life‐history variation of a neotropical thrush challenges food limitation theory

2005 ◽  
Vol 272 (1564) ◽  
pp. 769-773 ◽  
Author(s):  
Valentina Ferretti ◽  
Paulo E Llambías ◽  
Thomas E Martin
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Clutch Size ◽  
Life History Traits ◽  
Food Limitation ◽  
Life History Evolution ◽  
Traditional Theory ◽  
Life History Variation ◽  
Nestling Growth ◽  
Parental Feeding

Since David Lack first proposed that birds rear as many young as they can nourish, food limitation has been accepted as the primary explanation for variation in clutch size and other life‐history traits in birds. The importance of food limitation in life-history variation, however, was recently questioned on theoretical grounds. Here, we show that clutch size differences between two populations of a neotropical thrush were contrary to expectations under Lack's food limitation hypothesis. Larger clutch sizes were found in a population with higher nestling starvation rate (i.e. greater food limitation). We experimentally equalized clutches between populations to verify this difference in food limitation. Our experiment confirmed greater food limitation in the population with larger mean clutch size. In addition, incubation bout length and nestling growth rate were also contrary to predictions of food limitation theory. Our results demonstrate the inability of food limitation to explain differences in several life-history traits: clutch size, incubation behaviour, parental feeding rate and nestling growth rate. These life-history traits were better explained by inter‐population differences in nest predation rates. Food limitation may be less important to life history evolution in birds than suggested by traditional theory.

A kinetic Monte Carlo Model of Silicon CVD Growth from a Mixed H2/siH4 Gas Source

1999 ◽  
Vol 584 ◽  
Author(s):  
M. Fearn ◽  
M. Sayed ◽  
J. H. Jefferson ◽  
D. J. Robbins
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Model ◽  
Hydrogen Desorption ◽  
Time Step ◽  
Cvd Growth ◽  
Step Algorithm ◽  
Dynamics Simulations

AbstractWe report the development of an atomistic scale Kinetic Monte Carlo model of silicon CVD growth. By employing a variable time step algorithm, simulations have been performed over a range of time scales, enabling direct comparison with experimental data. The validity of using the kinetic theory of gases for evaluating steady state incoming particle fluxes within the model is demonstrated by comparison with computational fluid dynamics simulations. The model is applied to study hydrogen desorption rates from Si(001) and the dependence of silicon growth rate on substrate temperature, with results found to be in good agreement with experimental data. An experimentally observed decrease of growth rate with increasing H2 partial pressure is also reproduced by the model and shown to be caused by a decrease in silane adsorption on a hydrogen-rich surface.

scholarly journals In Situ Investigation of the Silicon Carbide Particles Sintering

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Yu Niu ◽  
Feng Xu ◽  
Xiaofang Hu ◽  
Jianhua Zhao ◽  
Hong Miao ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Solid State ◽  
Growth Exponent ◽  
Time Curve ◽  
Neck Growth ◽  
Neck Size ◽  
In Situ Investigation ◽  
Solid State Sintering ◽  
Time Observation ◽  
Sintering Neck

A real-time observation of the microstructure evolution of irregularly shaped silicon carbide powders during solid state sintering is realized by using synchrotron radiation computerized topography (SR-CT) technique. The process of sintering neck growth and material migration during sintering are clearly distinguished from 2D and 3D reconstructed images. The sintering neck size of the sample is presented for quantitative analysis of the sintering kinetics during solid state sintering. The neck size-time curve is obtained. Compared with traditional sintering theories, the neck growth exponent (7.87) obtained by SR-CT experiment is larger than that of the two-sphere model. Such condition is discussed and shown in terms of sintering neck growth, in which the sintering process slows down when the particle shape is irregular rather than spherical.

Computer Simulation of Neck Growth During Sintering Process

1999 ◽  
pp. 61-66
Author(s):  
Zoran S. Nikolic ◽  
Ivona Mitrovic ◽  
Vojislav V. Mitic
Keyword(s):  
Computer Simulation ◽  
Sintering Process ◽  
Neck Growth

scholarly journals Determination of the Neck Size between Powders during Sintering Process Using Finite Element Methods

2020 ◽  
Vol 1 (2) ◽  
pp. 29-36
Author(s):  
Anas Obeed Balod ◽  
Ziad Al Sarraf ◽  
Anas Abid Mattie
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Process Time ◽  
Sintering Process ◽  
Solid Product ◽  
Discrete Method ◽  
Neck Size ◽  
Powder Density ◽  
Structure Geometry

Today, sintering considers one of the significant processes that can be used in powder technology to produce a new solid product from powders using thermal energy. Many parameters can be successfully controlled by this process such as temperature, Particle size, process time, structure geometry, powder density, and powder composition. Study and analysis of the behavior of powder during the sintering process was carried out using finite element methods. The simulation provides two styles of discrete method and Qusi-static method. This research contributes to two types of processes in order to simulate the copper powder during the sintering process and to determine the variation by using contact and shrinkage ratios of powder behaviors. Finally, a comparison between the two styles of discrete element method explains how the selected parameters were impacted on the sintering process.

Numerical Simulation on the Sintering Process of Nanocomposite Ceramic Tool Materials

2012 ◽  
Vol 500 ◽  
pp. 519-524
Author(s):  
Hong Mei Cheng ◽  
Chuan Zhen Huang ◽  
Bin Zou ◽  
Hong Tao Zhu ◽  
Han Lian Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Growth Rate ◽  
Model Simulation ◽  
Ceramic Matrix ◽  
Ceramic Materials ◽  
Sintering Process ◽  
Ceramic Tool ◽  
Two Phase ◽  
Tool Materials ◽  
Simulation Results

A Monte Carlo Potts model for the sintering process of two-phase nanocomposite ceramic tool materials is proposed. The grain growth, pore diffusion and vacancy annihilation at grain boundaries are simulated in the model. Simulation results are presented and discussed. It is found that pore and nanophase can pin the ceramic matrix and decrease the growth rate of matrix grain during the microstructure evolution. The addition of nanoparticles is not only beneficial to the refinement of ceramic matrix grain and the formation of intra/intergranular-type microstructure but also advantageous to the densification of ceramic materials.

Simulating Sintering Process in SmCo5 Magnets

2008 ◽  
Vol 591-593 ◽  
pp. 80-85 ◽  
Author(s):  
José Adilson de Castro ◽  
Marcos Flavio de Campos
Keyword(s):  
Growth Rate ◽  
Particle Size ◽  
Grain Size ◽  
Magnetic Properties ◽  
Grain Growth ◽  
Sintering Process ◽  
Densification Rate ◽  
Size Evolution ◽  
Sintering Conditions ◽  
Crystal Particle

SmCo5 sintered magnets are produced according the following main processing: milling until single crystal particle size, compaction and sintering. It is necessary high density to maximize remanence, but small grain size to maximize coercivity. A sintering model able to incorporate both, the densification rate and the grain growth rate, is described. This makes easier to find the better sintering conditions for optimization of the magnetic properties (coercivity and remanence). The presented model represents a refinement of previous sintering models, because it takes into account the coupled effects of grain size evolution and shrinkage.

Monte Carlo Simulation of Gas Phase Particle Formation and Sintering

1992 ◽  
Vol 278 ◽  
Author(s):  
M. Kamal Akhtar ◽  
S. E. Pratsinis ◽  
G. G. Lipscomb
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Fractal Dimension ◽  
Gas Phase ◽  
Phase Particle ◽  
Monte Carlo Model ◽  
Sintering Process ◽  
Small Length ◽  
Cluster Aggregation ◽  
Random Particle

AbstractA Monte Carlo model has been developed to describe the gas phase formation and sintering of nanoclusters. Sintering was incorporated into the model by modifying Kadanoff's algorithm [1] for random particle walks on the surface of the cluster. The effect of restructuring and sintering on cluster-cluster aggregation have been investigated via 2d simulations. In the initial stages the sintering process results in clusters which are compact on small length scales. As time progresses and the clusters become larger, the sintering process slows down and the fractal dimension of the clusters is decreased. The model shows the effect of time and temperature on the specific surface area and size distribution of clusters.

Microstructural Study of Diamond Deformed Under High Pressure and Temperature

1985 ◽  
Vol 43 ◽  
pp. 230-231
Author(s):  
E. F. Koch
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Lattice Structure ◽  
Diamond Particle ◽  
Polycrystalline Diamond ◽  
Sintering Process ◽  
Ion Milling ◽  
Sintered Compact ◽  
Transmission Electron ◽  
High Pressure Sintering

Because of the extremely rigid lattice structure of diamond, generating new dislocations or moving existing dislocations in diamond by applying mechanical stress at ambient temperature is very difficult. Analysis of portions of diamonds deformed under bending stress at elevated temperature has shown that diamond deforms plastically under suitable conditions and that its primary slip systems are on the ﹛111﹜ planes. Plastic deformation in diamond is more commonly observed during the high temperature - high pressure sintering process used to make diamond compacts. The pressure and temperature conditions in the sintering presses are sufficiently high that many diamond grains in the sintered compact show deformed microtructures.In this report commercially available polycrystalline diamond discs for rock cutting applications were analyzed to study the deformation substructures in the diamond grains using transmission electron microscopy. An individual diamond particle can be plastically deformed in a high pressure apparatus at high temperature, but it is nearly impossible to prepare such a particle for TEM observation, since any medium in which the diamond is mounted wears away faster than the diamond during ion milling and the diamond is lost.

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