Experimental Study On Tungsten Type Delay Composition With Low Temperature Sensitivity And High Precision

In order to reduce the influence of ambient temperature on the burning rate of tungsten type delay composition and improve the delay accuracy of tungsten type delay composition,the influence of different materials on the thermal conductivity and temperature coefficient of tungsten type delay composition was investigated by adding a series of thermal conductive fillers and negative thermal expansion materials.In order to facilitate the comparison,the total accuracy of high and low temperature delay time is used to express the temperature coefficient.（1）A device for testing delay time by p-t curve is designed.The delay time of second-level extension body and millisecond-level extension body were measured by p-t curve method and photoelectric method respectively,and the results were compared.Among them,the delay accuracy of second-level extension body calculated by photoelectric method is 2.22%,and that calculated by p-t curve method is 2.73%.Experiments show that the p-t curve method has low error and high accuracy in measuring second-level extension body,which fully meets the experimental requirements of tungsten delay composition in this paper.（2）The thermal conductivity and delay time of tungsten type delay composition base composition and its mixture with thermal conductive fillers such as AlN,BN and SiC were tested.The thermal conductivity of the base composition is 0.3670W/（m.K）at low temperature（-40℃）and 0.3662 W/（m.K）at high temperature（65℃）,and the thermal conductivity is only reduced by 0.22%at high temperature.The thermal conductivity of the base composition with 16%AlN sample is 0.3904W/（m.K）at low temperature and0.3855W/（m.K）at high temperature.The thermal conductivity decreases to a certain extent at high temperature.The test results of short extension body（200mg delay charge）show that the total accuracy of high and low temperature of base composition is about 27%.The total accuracy of high and low temperature of tungsten type delay composition is 15.15%after adding 10%AlN.The test results of long delay body（440mg delay charge）show that the total accuracy of high and low temperature of base composition is about 20%.After adding16%AlN,the total accuracy of high and low temperature is 11.39%.Through the analysis of TG-DSC spectra,it can be inferred that the addition of thermal conductive fillers has a certain catalytic effect on the solid-solid reaction of tungsten delay composition,and AlN itself does not participate in the combustion process,but plays the role of absorbing heat.In this temperature range,the thermal conductivity of BN and SiC increases with the increase of temperature,so the thermal conductivity of the base composition with 6%BN and10%SiC increases by 2.66%and 3.07%respectively at high temperature.The test of delay time shows that BN and SiC can act as burning rate modifier of tungsten type delay composition,but have little effect on temperature coefficient.（3）When 10%negative thermal expansion material ZrW₂O₈ is added to the base composition,the thermal conductivity of the sample increases significantly,and decreases by 2.7%at high temperature compared with that at low temperature.It can be inferred that the negative thermal expansion effect of ZrW₂O₈ results in a negative correlation between the thermal conductivity and temperature of the mixture.The thermal conductivity of the base composition with 20%Mn₃Cu_0.5Ge_0.5N_0.9C_0.1 did not change significantly at-40℃^-8℃,and ZrW₂O₈ and Mn₃Cu_0.5Ge_0.5N_0.9C_0.1 have no significant effect on reducing the temperature coefficient of tungsten delay composition.The reasons need to be further studied.