Author: momo
Link: https://zhuanlan.zhihu.com/p/675576020
Source: Zhihu
AI Summary
This paper, “Method of Vacuum Sealing and Sintering LK-99 by Falsification – Scientificity of the Falsified Sample after Firing,” analyzes the scientific validity of using the vacuum sealing method to synthesize LK-99 crystals. The main contents and conclusions include:
The study shows that when LK-99 is sintered under a vacuum of 10-3 Torr, the theoretical oxygen partial pressure at room temperature is 2.76 × 10-7 atm, which satisfies the equilibrium decomposition pressure of Cu2O at 925°C and prevents the reduction of PbO to lead. However, the actual working conditions do not match the theory.
The oxygen partial pressure inside the vacuum-sealed tube is affected by multiple factors, such as the desorption of adsorbed gases from objects and the high-temperature cracking reaction of mechanical pump oil, causing the oxygen partial pressure to fluctuate within a very wide range (from 1.42 × 10-1 to 1.1 × 10-19 atm), which makes it difficult to control the oxygen partial pressure.
LK-99 samples sintered under the same conditions have different properties. One time it may be an insulator, the next time it may be metallic. This inconsistency is due to the relationship between the redox reaction of copper and lead and the oxygen partial pressure in the tube.
Experiments show that there is no direct correspondence between the vacuum degree of the vacuum-sealed tube and the oxygen partial pressure inside the tube.
The study analyzed the equilibrium decomposition pressure (oxygen partial pressure) of Cu, Pb, and Fe oxides at different temperatures and believed that the reaction for synthesizing LK-99 can be divided into two steps: first, the redox reaction on the surface of cerussite and cuprous phosphide powders, and second, the substitution reaction between cuprous phosphide and cerussite. These reactions must be carried out in the corresponding oxygen partial pressure atmosphere.
Due to the influence of various uncontrollable factors, the oxygen partial pressure in the vacuum-sealed tube fluctuates too much, making it impossible to produce qualified LK-99.
The paper also explores the feasibility of the electric furnace sintering method for LK-99 using an oxygen probe to control the oxygen partial pressure.
In summary, this study falsifies the effectiveness of using the vacuum sealing method to prepare LK-99 and proposes possible improvements.
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