Study On The Surface Modification And Properties Of Metal Hydride

Hydrogen energy is the twenty-first century green new energy. Hydrogen has thecharacteristic of the smallest molecular weight, the highest unit mass heat ofcombustion, and has good combustion performance, inflammable, product ofcombustion do not pollute the environment and so on. It is also a kind of excellentrocket fuel. But restricted by technological conditions at present, we can not addliquid hydrogen into solid propellant, the probable method of introduction ofhydrogen in solid rocket propellant is metal hydride. Metal hydrides are one ofpromising metallic hydrogen storage materials. Because of the characteristic of largeamount of hydrogen storage and stable property, therefore metal hydride has highercombustion heat than metal, so this feature made it have high research value inenergetic materials areas. This text use hydroxyl-terminated polybutadiene (HTPB)and octadecylamine respectively coated on the surface of titanium hydride (TiH2),magnesium hydride (MgH2) and lithium hydride (LiH) in order to improve thecompatibility and increase the dispersion of hydride and ammonium perchlorate (AP)which is the main components in solid rocket propellant, we also study the impacts ofmodified hydride on the thermal decomposition of ammonium perchlorate (AP).1. In this paper, we used hydroxyl-terminated polybutadiene (HTPB) which act asadhesive in solid rocket propellant as coating agent and2,4-toluene diisocyanate(TDI) as a curing agent for surface coating modification on titanium hydride (TiH2)and magnesium hydride (MgH2). This article also uses octadecylamine on lithiumhydride (LiH) for surface coating modification. Using FTIR, SEM, XRD, XPS,TG/DSC on the before and after coating of TiH2and MgH2were characterized; UsingSEM, XRD, TG/DSC on the before and after coating of LiH were characterized. Itturned out that a layer of dense organic membrane was coated on the surface ofTiH2,MgH2and LiH; coated TiH2and coated MgH2have appeared the vibrationabsorption peak of N-H bond; HTPB coated on pure TiH2and pure MgH2particlesdid not have an impact on the crystal form and the thermodynamic perormances ofTiH2and MgH2. We detected C, N, O three elements but no Ti and Mg element bothin coated TiH2and coated MgH2. The coated degrees of HTPB coating on TiH2is40.97%, the coated degrees of HTPB coating on MgH2is63.45%. We coated a layerof octadecylamine on the surface of pure LiH successfully. Octadecylamine coated onpure LiH particles did not have an impact on crystal form of LiH. The coated degree of octadecylamine coating on LiH is25%.2. We can know that HTPB coated on the surface of TiH2and MgH2effectivelyprevent AP oxidizing TiH2and MgH2though the XRD test of metal hydride andAPcomposite particles. From the dispersity of TiH2and MgH2in HTPB, we knowthat coated TiH2and MgH2have good disperstiveness in the HTPB.3. The results of three kinds of metal hydride on the thermal decomposition ofammonium perchlorate (AP) show that TiH2has a catalytic effect on the thermaldecomposition of AP. Following the addition of TiH2content, TiH2has someimpediment on the low-temperature thermal decomposition temperature of AP, reducethe high-temperature thermolysis temperature of AP and increase the heat release ofthe thermolysis of AP. MgH2has a catalytic action on the thermolysis of AP. With theaddition of MgH2content, MgH2has some impediment on the low-temperaturethermal decomposition temperature of AP, reduce the high-temperature thermolysistemperature of AP and increase the heat release of the thermolysis of AP. LiH makethe decomposition of AP at low temperature and high temperature into oneexothermic peak. LiH have obvious catalytic action on the thermolysis of AP, and LiHcan decrease high-temperature thermal decomposition temperature of AP and increasethe heat release of the thermal decomposition of AP.4. The results of three kinds of metal hydride on the kinetics of ammoniumperchlorate (AP) show that the activation energy of composite particle of modifiedTiH2and AP are101.1296KJ/mol and162.062KJ/mol at low temperaturedecomposition and high temperature decomposition respectively; the activationenergy of composite particle of modified MgH2and AP are101.27KJ/mol and141.44KJ/mol at low temperature decomposition and high temperature decompositionrespectively; the activation energy of composite particle of modified LiH and AP is88.757KJ/mol. Compared with the activation energy of pure AP, the coated TiH2,MgH2and LiH can obviously reduce the activation energy of AP, this shows that thecoated metal hydride have obvious role in promoting on the thermal decompositionprocess of AP.