scholarly journals Scientific approaches to problems of mixtures sintering

2005 ◽  
Vol 37 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Arnold Savitskii
Keyword(s):  
Driving Forces ◽  
Solid Phase ◽  
Scientific Basis ◽  
Liquid Phase Sintering ◽  
Alloy Formation ◽  
Sintering Process ◽  
Volume Changes ◽  
Powder Body ◽  
Metal Materials ◽  
Skeleton Structure

Existing theories cannot convincingly explain relationships observed during sintering of mixtures and do not always help solve practical problems of sintering metal materials and ceramics. The main weakness of the known theories is insufficient attention to the phenomenon of alloy formation and its effect on volume changes of compacts, faulty ideas regarding driving forces for the sintering process, the mistaken mechanism of dissolution of solid phase in liquid, and the inaccurate mechanisms of growth and densification during the sintering of mixtures. Besides, obsolete theories are developed, as a rule, on the basis of a two-partial model that does not permit taking into account the skeleton structure of a powder body and the presence of interparticle pores in it. Essentially fresh concepts in the theory of mixture sintering are formulated and defined in this paper. The new approaches eliminate the drawbacks and discrepancies in the existing theories and provide the scientific basis for solid state and liquid phase sintering of mixtures.

Effect of Copper Micro-Scale Excess on the Dielectric Properties of CaCu3Ti4O12 Ceramics Prepared via Tape Casting

2014 ◽  
Vol 941-944 ◽  
pp. 517-520
Author(s):  
Wei Li ◽  
Zhao Xian Xiong ◽  
Hao Xue ◽  
Chun Xiao Song ◽  
Hong Qiu
Keyword(s):  
Dielectric Properties ◽  
Solid Phase ◽  
Tape Casting ◽  
Temperature Stability ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Micro Scale ◽  
Low Dielectric ◽  
High Dielectric ◽  
Effect Of Copper

CaCu(3+x)Ti4O12 (x = 0, 0.001, 0.002, 0.004 and 0.008) ceramics with variation in copper micro-scale excess were prepared via solid-state reaction, Aqueous technology of tape casting was applied to obtain thick films of, about 100 μm in thickness. Crystal phases of the samples were identified by XRD. SEM of samples revealed that copper micro-scale excess can accelerate some important solid phase reactions in the sintering process, most because of liquid phase sintering mechanism. EDX analysis indicated that copper micro-scale excess could compensate for a lack of copper in sintering process. The Cu3.004 sample exhibited the best dielectric properties with a very low dielectric loss (0.029), while retaining a very high dielectric constant (91,536), and the Cu3.002 and Cu3.004 samples exhibited a well frequency and temperature stability which was of significant industrial relevance. In this work, it was concluded that a certain amount of Cu micro-scale excess could improve dielectric properties, frequency stability and temperature stability of CCTO ceramics.

scholarly journals A Computational Method for The Computer Simulation of The Liquid Phase Sintering of Metallic Systems

2020 ◽  
Author(s):  
Hamed Hosseinzadeh
Keyword(s):  
Liquid Phase ◽  
Binary Phase Diagram ◽  
Solid Phase ◽  
Liquid Phase Sintering ◽  
Solid Particles ◽  
Computational Method ◽  
Sintering Process ◽  
Composition Variation ◽  
Liquid And Solid Phases ◽  
Oswald Ripening

The growth of solid particles during liquid phase sintering was modeled by the Cellular Automata method. The binary phase diagram and Fickian approach for the diffusion process were applied to simulate the chemical composition variation in liquid and solid phases during sintering. The Oswald-Ripening effect was considered during the dissolution of the solid phase in the liquid phase. It is used to define the probability of solid-phase dissolution by the liquid phase and develop the model to simulate the alloy with solid solubility. So, the microstructure could be modeled in the liquid phase sintering process.

Upconversion luminescence properties of Li+-doped ZnWO4:Yb,Er

2008 ◽  
Vol 23 (8) ◽  
pp. 2078-2083 ◽  
Author(s):  
Xi-xian Luo ◽  
Wang-he Cao
Keyword(s):  
Liquid Phase ◽  
Calcination Temperature ◽  
Crystal Field ◽  
Lower Energy ◽  
Upconversion Luminescence ◽  
Peak Position ◽  
Liquid Phase Sintering ◽  
Red Shift ◽  
Luminescence Properties ◽  
Sintering Process

Upconversion luminescence (UPL) characteristics and effects of Li+ ion on the UPL of ZnWO4:Yb,Er polycrystalline phosphors were investigated. It was shown that introduction of Li+ ions could reduce the calcination temperature by about 200 °C and increase the crystallinity of ZnWO4:Yb,Er by a liquid-phase sintering process via formation of Li2WO4 and other intermediates. UPL efficiency is remarkably promoted by Li+ ions. Moreover, the UPL spectrum of Li+-doped ZnWO4:Yb,Er presents a red shift, and the strongest peak position shifts from 553 to 559 nm. These can be attributed to a shift in the 4f level barycenter to lower energy, which results from lowering of the symmetry of the crystal field around Er3+.

scholarly journals Synthesis of Ge1−xSnx Alloy Thin Films by Rapid Thermal Annealing of Sputtered Ge/Sn/Ge Layers on Si Substrates

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2248 ◽  
Author(s):  
Hadi Mahmodi ◽  
Md Hashim ◽  
Tetsuo Soga ◽  
Salman Alrokayan ◽  
Haseeb Khan ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Near Infrared ◽  
Annealing Temperature ◽  
Solid Phase ◽  
Infrared Region ◽  
Alloy Formation ◽  
Phase Mixing ◽  
Si Substrates ◽  
Msm Photodetector

In this work, nanocrystalline Ge1−xSnx alloy formation from a rapid thermal annealed Ge/Sn/Ge multilayer has been presented. The multilayer was magnetron sputtered onto the Silicon substrate. This was followed by annealing the layers by rapid thermal annealing, at temperatures of 300 °C, 350 °C, 400 °C, and 450 °C, for 10 s. Then, the effect of thermal annealing on the morphological, structural, and optical characteristics of the synthesized Ge1−xSnx alloys were investigated. The nanocrystalline Ge1−xSnx formation was revealed by high-resolution X-ray diffraction (HR-XRD) measurements, which showed the orientation of (111). Raman results showed that phonon intensities of the Ge-Ge vibrations were improved with an increase in the annealing temperature. The results evidently showed that raising the annealing temperature led to improvements in the crystalline quality of the layers. It was demonstrated that Ge-Sn solid-phase mixing had occurred at a low temperature of 400 °C, which led to the creation of a Ge1−xSnx alloy. In addition, spectral photo-responsivity of a fabricated Ge1−xSnx metal-semiconductor-metal (MSM) photodetector exhibited its extending wavelength into the near-infrared region (820 nm).

scholarly journals Online Monitoring Based on Temperature Field Features and Prediction Model for Selective Laser Sintering Process

2018 ◽  
Vol 8 (12) ◽  
pp. 2383 ◽  
Author(s):  
Zhehan Chen ◽  
Xianhui Zong ◽  
Jing Shi ◽  
Xiaohua Zhang
Keyword(s):  
Temperature Field ◽  
Prediction Model ◽  
Selective Laser Sintering ◽  
Principal Component ◽  
Laser Sintering ◽  
Support Vector ◽  
Sintering Process ◽  
Metal Materials ◽  
Key Features ◽  
The Mathematical Model

Selective laser sintering (SLS) is an additive manufacturing technology that can work with a variety of metal materials, and has been widely employed in many applications. The establishment of a data correlation model through the analysis of temperature field images is a recognized research method to realize the monitoring and quality control of the SLS process. In this paper, the key features of the temperature field in the process are extracted from three levels, and the mathematical model and data structure of the key features are constructed. Feature extraction, dimensional reduction, and parameter optimization are realized based on principal component analysis (PCA) and support vector machine (SVM), and the prediction model is built and optimized. Finally, the feasibility of the proposed algorithms and model is verified by experiments.

scholarly journals A mathematical approach to Ostwald ripening due to diffusion and deformation in liquid bridge

2013 ◽  
Vol 45 (3) ◽  
pp. 261-271 ◽  
Author(s):  
B. Randjelovic ◽  
K. Shinagawa ◽  
Z.S. Nikolic
Keyword(s):  
Liquid Phase ◽  
Liquid Bridge ◽  
Ostwald Ripening ◽  
Solid Phase ◽  
Liquid Phase Sintering ◽  
Solute Diffusion ◽  
Deformation Analysis ◽  
Mathematical Approach ◽  
Fe Method ◽  
Grain Coarsening

From many experiments with mixtures of small and large grains, it can be concluded that during liquid phase sintering, smaller grains partially dissolve and a solid phase precipitates on the larger grains and grain coarsening occurs. The growth rate can be controlled either by the solid-liquid phase boundary reaction or by diffusion through the liquid phase. The microstructure may change either by larger grains growing during the Ostwald ripening process or by shape accommodation. In this study, two-dimensional mathematical approach for simulation of grain coarsening by grain boundary migration based on a physical and corresponding numerical modeling of liquid phase sintering will be considered. A combined mathematical method of analyzing viscous deformation and solute diffusion in liquid bridge between two grains with different sizes will be proposed. The viscous FE method will be used for calculating meniscus of the liquid bridge, with the interfacial tensions taken into consideration. The FE method for diffusion will be also implemented by using the same mesh as the deformation analysis.

Effect of WC Addition on Phase Formation and Microstructure of TiC-Ni Composites

2008 ◽  
Vol 55-57 ◽  
pp. 353-356
Author(s):  
Nawarat Wora-uaychai ◽  
Nuchthana Poolthong ◽  
Ruangdaj Tongsri
Keyword(s):  
Liquid Phase ◽  
Tungsten Carbide ◽  
Phase Formation ◽  
Liquid Phase Sintering ◽  
Precipitation Process ◽  
Solid Solution Phase ◽  
Binder Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray

In this research, titanium carbide-nickel (TiC-Ni) composites, with tungsten carbide addition, were fabricated by using a powder metallurgy technique. The TiC-Ni mixtures containing between 0-15 wt. % tungsten carbide (WC), were compacted and then sintered at 1300°C and 1400°C, respectively. The phase formation and microstructure of the WC-added TiC-Ni composites have been investigated by X-ray diffraction and scanning electron microscopy techniques. Mechanical properties of these composites were assessed by an indentation technique. The X-ray diffraction patterns showed no evidence of tungsten rich phases in the sintered WC-added cermets. This indicates that during the sintering process, tungsten carbide particles were dissolved in metallic binder phase (Ni phase) via dissolution/re-precipitation process during liquid phase sintering. The liquid phase formed during sintering process could improve sinterability of TiC-based cermets i.e., it could lower sintering temperatures. The TiC-Ni composites typically exhibited a core-rim structure. The cores consisted of undissolved TiC particles enveloped by rims of (Ti, W)C solid solution phase. Hardness of TiC-Ni composites increased with WC content. Sintering temperature also had a slight effect on hardness values.

Sign in / Sign up

Export Citation Format

Share Document