LiF negative catalyst

The thermal decomposition process of AP particles is altered significantly when 10% LiF is added, as shown in Fig. 7.25. The decomposition of AP particles without LiF commences at about 570 K and 50% mass loss occurs at 667 K, which corresponds to the exothermic peak. The TG curve consists of a two-stage mass-loss process. The first stage corresponds to the first exothermic reaction at 635 K, and the second stage corresponds to the second exothermic reaction in the high-temperature region between 723 K and 786 K observed in the DTA experi- 

When 10% liF is added to the AP particles, an endothermic peak is observed at 516 K. The exothermic peak originally at 725 K now appears at 635 K. An endothermic reaction occurs between 520 K and 532 K. An additional exothermic peak is observed in the higher temperature region between 720 K and 790 K. 

An endothermic peak at 525 K is observed when lithium perchlorate (LiC104 LP) is thermally decomposed, caused by the phase change from soUd to hquid. As the temperature is increased further, the molten LiC104 begins to decompose at about 680 K and rapid mass-loss decomposition occurs in the temperature range between 720 K and 790 K. This decomposition is similar to that of the AP particles with 10 % LiF added. 

The mass loss of the first-stage decomposition of the AP particles with 10% LiF is 56.7 %, and that of the second-stage decomposition is 28.5 %. The residue remaining above 790 K is 14.8%. As shown in Fig. 7.26, the two-stage decomposition process can be summarized as follows [i5] 

The decomposition process of the AP particles is greatly altered by the addition of LiF. After the rapid decomposition and gasification reactions at about 630 K, an undecomposed liquefied residue remains. This residue is the same material as observed in the temperature range between 640 K and 720 K. When the temperature is increased further, the liquefied residue again decomposes at about 750 K and produces a solidified residue at 790 K. This solidified residue is determined by chemical analysis to be LiCl. 

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Iron oxides and organic iron compounds act as posihve catalysts, whereas liF, CaC03, and SrC03 act as negative catalysts. 

Q4 MPa s When a negative catalyst such as LiF or SrCOj was added to the AP composite propellant, combustion interruption occurred. As shown in Fig. 7.27, the pressure deflagration limit is lowered by the addition of the negative catalysts. Detailed design work of a dual-grain dual-thrust motor and the associated combustion test results are shown in Ref [5]. 

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