Removal of metal impurities in metallurgical grade silicon by cold crucible continuous melting and directional solidification

2017 ◽  
Vol 188 ◽  
pp. 67-72 ◽  
Author(s):  
Feng Huang ◽  
Ruirun Chen ◽  
Jingjie Guo ◽  
Hongsheng Ding ◽  
Yanqing Su
Keyword(s):  
Directional Solidification ◽  
Cold Crucible ◽  
Metallurgical Grade Silicon ◽  
Metal Impurities ◽  
Continuous Melting ◽  
Removal Of Metal ◽  
Grade Silicon

The Influence of Cooling Water Flow to Purify the Metallurgical Grade Silicon by Directional Solidification

2013 ◽  
Vol 712-715 ◽  
pp. 784-787
Author(s):  
Tao Lin ◽  
Da Jun Zhang ◽  
Chun Yan Duan ◽  
Dong Liang Lu
Keyword(s):  
Directional Solidification ◽  
Water Flow ◽  
Removal Efficiency ◽  
Cooling Water ◽  
Experimental Results ◽  
Metallurgical Grade Silicon ◽  
Density Of Dislocations ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Grade Silicon

Directional solidification is one of the most important processes to purify the impurities in the metallurgical grade silicon. A lot of factors could influence the result of directional solidification. In this paper, we researched cooling water flow which could influence the result of directional solidification. We have studied three data of cooling water flow which influenced the results of the removal efficiency of the impurities. Experimental results showed that cooling water flow can influence the density of dislocations and twins in the ingot. The metal impurities of Al, Fe and Ca were concentrated in the middle of the silicon ingot mostly. It was inferred that the bigger cooling water flow was better to the efficiency of the purification in the experiment.

Experiment Research on Purifying Metallurgical Grade Silicon and Crystal Growth in Directional Solidification

2009 ◽  
Vol 79-82 ◽  
pp. 1213-1216 ◽  
Author(s):  
Xiang Yang Mei ◽  
Wen Hui Ma ◽  
Kui Xian Wei ◽  
Yong Nian Dai
Keyword(s):  
Crystal Growth ◽  
Directional Solidification ◽  
Crystalline Silicon ◽  
Acid Leaching ◽  
Raw Material ◽  
Metallurgical Grade Silicon ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Segregation Effect ◽  
Grade Silicon

The main raw material of solar energy is multi-crystalline silicon. Directional solidification technique is one important technological process of metallurgy purification technology for multi-crystalline silicon. It can purify metallurgical grade silicon by removing metal impurities and control crystal growth at the same time. In experiment, metallurgical grade silicon by acid leaching pre-treatment, was purified by our self-assembled directional solidification furnace. The sample was analyzed by electron-prode micro analysis (EPMA). According to the results, the removal efficiency of Fe and Al is 96.3% and 96.7%, respectively. The removing mechanism of metal impurities and the difference between theory value and experiment value were also discussed. The segregation effect in directional solidification is the reason of removing Fe, but analgesic effects of the segregation effect combined with vacuum volatilization are that of removing Al. When the silicon ingot was cooled down, lengthways section of silicon ingot was cut and etched, crystal growth was studied. The results indicate that columnar crystal growth shows diverging tendency from the bottom to the top of silicon ingots, and solidification interface shape is convex. The reasons may be the nucleation of new crystals on crucible sidewall is very serious and the pulling rate is too high.

Effect of Na2O-SiO2 Slag Treatment on Hydrometallurgical Purification of Metallurgical Grade Silicon

2013 ◽  
Vol 420 ◽  
pp. 139-143 ◽  
Author(s):  
M. Fang ◽  
C.H. Lu ◽  
H.X. Lai ◽  
L.Q. Huang ◽  
J. Chen ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Acid Corrosion ◽  
Intermetallic Phases ◽  
Leaching Behavior ◽  
Metallurgical Grade Silicon ◽  
Metal Impurities ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Corrosion Experiment ◽  
Grade Silicon

The effects of Na2O-SiO2slag treatment on purification of metallurgical grade silicon by leaching with hydrogen fluoride have been investigated. A comparative analysis of microstructure evolution was carried out to examine the leaching behavior of impurities from metallurgical grade silicon. It was found that the distribution of metal impurities Al, Ca, Ti and Na, which co-deposited with Si and formed different intermetallic phases at grain boundaries, had manifest distinction between precipitated phase and silicon. Moreover, acid corrosion experiment results revealed that slag treatment improved the dissolution rate of metal impurities from metallurgical grade silicon as contrasted to that without slag treatment.

Effect of Withdrawal Rate on Defects of Upgraded Metallurgical Grade (UMG)-Silicon Prepared by Vacuum Directional Solidification

2013 ◽  
Vol 750 ◽  
pp. 316-319
Author(s):  
Wen Hui Ma ◽  
Yong Jiang ◽  
Yang Zhou ◽  
Kui Xian Wei ◽  
Bin Yang ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Directional Solidification ◽  
Carbon Concentration ◽  
Withdrawal Rate ◽  
Structural Defects ◽  
Driving Mechanism ◽  
Quasi Equilibrium ◽  
Metallurgical Grade Silicon ◽  
Grade Silicon ◽  
Upgraded Metallurgical Grade Silicon

The structural defects including dislocations and grain boundaries (GBs) in upgraded metallurgical grade silicon (UMG-Si) prepared by vacuum directional solidification were investigated. The results demonstrated that higher withdrawal rates increased the dislocation density. The state of melt growth changed from quasi-equilibrium to non-equilibrium, and the GB type was also highly related to the withdrawal rate, especially for ∑3 boundary. The change of total interfacial energy and increase of carbon concentration may be a possible driving mechanism for this phenomenon.

Transition-Metal Impurities Removal from Metallurgical Grade Silicon by Electron Beam Injection

2011 ◽  
Vol 675-677 ◽  
pp. 105-108
Author(s):  
Rui Xun Zou ◽  
Da Chuan Jiang ◽  
Wei Dong ◽  
Zheng Gu ◽  
Yi Tan
Keyword(s):  
Electron Beam ◽  
Transition Metal ◽  
Removal Rate ◽  
Silicon Powder ◽  
Sio2 Film ◽  
Metallurgical Grade Silicon ◽  
Beam Injection ◽  
Metal Impurities ◽  
Transition Metal Impurities ◽  
Grade Silicon

The electron beam injection (EBI) process involves offering electrons around silicon powder, whose surface was oxidized, and subsequently the powder is washed by HF acid so as to remove the SiO2 film. The new electron beam injection process, in which micro electric filed formed between Si and SiO2 film will accelerate impurities diffusion from Si to SiO2 film, was developed and applied to eliminate the transition-metal impurities of MG-Si. It is proved to be effective to remove transition-metal impurities from metallurgical grade silicon (MG-Si). By applying the electron beam injection method, the removal rate of 10% to 59% was achieved during the refining process. The efficiency of impurity removal originates from two aspects: the impurity concentration gradient on both sides of Si/SiO2 interface; the micro electric field formed from Si to SiO2 film. A further increase in the removal rate can be realized by controlling the processing parameters.

Effect of Sodium-Based Slag Treatment on the Distribution of Impurities in Metallurgical Grade Silicon

2013 ◽  
Vol 690-693 ◽  
pp. 949-953
Author(s):  
Ming Fang ◽  
Cheng Hao Lu ◽  
Hui Xian Lai ◽  
Liu Qing Huang ◽  
Juan Chen ◽  
...  
Keyword(s):  
Slag Phase ◽  
Homogeneous Distribution ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Metal Impurities ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Before And After ◽  
Grade Silicon ◽  
Metallic Impurities

The distribution of impurities in metallurgical grade silicon before and after slag treatment was investigated for the purpose of upgrading metallurgical grade to solar grade silicon. It was found that metal impurities co-deposited with silicon and formed different intermetallics in the precipitated phase, and these intermetallics such as Si-Fe, Si-Ni, Si-Ti-V and Si-Ca-Al-Fe were substituted by Si-Fe-Ti-V after treatment of Na2CO3-SiO2 slag. Non-metallic impurities B and P were nearly homogeneous distribution in metallurgical grade silicon before and after slag treatment. Moreover, a particular analysis of the microstructure of slag has been carried out, it was determined that metal impurities Al and Ca could easily migrate from silicon to slag phase in the refining process.

Sign in / Sign up

Export Citation Format

Share Document