Impurity Analysis Of Rocket Propellant AlH₃ & Distinct Effects Of Rhenium And Tantalum On Helium Clustering In Tungsten:A First-principles Calculation

First part:Aluminum hydride(AlH₃),an attractive hydrogen storage material,has a crucial role in rocket propellant industry.The impurities in aluminum hydride may seriously cause the deterioration in properties and stability of AlH₃.Mixing AlH₃sample with the known content of silicon,we distinguish all the elements in AlH₃sample and determine their concentration by using PIXE,XPS and elemental analyzer.Elements of Al,Si,Cl,Ca and Fe were identified by PIXE.XPS technique was used to measure the oxidized product of the mixed silicon.C,H content were obtain from the elemental analyzer.For carbon,the large discrepancy was found between XPS and elemental analyzer,which suggests XPS technique is not well suited to the determination of the bulk concentration of elements easily contaminated from ambient.For H,our quantitative result is slightly less than the theoretical value,which could attribute to the decomposition of our samples.Mixing the AlH₃ sample with known content of single-crystal silicon,we distinguish the phase compositions in two type of AlH₃ product and determine their concentration by Rietveld refinement method.Results show the content of?-AlH₃,?'-AlH₃,Al(OH)₃and amorphous phases in sample A is 63.94%(±3.40),9.83%(±0.64),7.95%(±0.99)and 18.27%(±4.39)respectively.Sample B contains 24.12%(±0.81)?-AlH₃,6.53%(±0.57)Al and 69.34%(±1.29)amorphous phases.Above results suggest that sample A is better than sample B.By using TG-IR-MS method,we distinguished the organic residue in AlH₃ product and determined their concentration.Results show there are 2.45%methylbenzene(C₇H₈),0.07%cyclohexane(C₆H₁₂)and 0.28%ethyl ether(C₄H₁₀O).This work provides the analysis method of impurities in AlH₃ product,which is veryimportant for the evaluation of its quality.Second part:The radiation damage especially helium bubbles caused by deuterium tritium thermonuclear fusion reaction is a serious challenge for tungsten applied in first wall materials.Therefore,it is necessary to study the behavior of He cluster in tungsten under fusion conditions.Low energy He⁺irradiation experiments have confirmed that the self-trapping of He atom results in the formation of He bubbles in defect-free tungsten.By using DFT calculations,we have studied the influence of rhenium(Re)and tantalum(Ta)on clustering of helium(He)atoms in the defect-free tungsten.The results show that He atoms prefer to have a monolayer structure between tungsten(110)planes and their bond is tight during the clustering.Thermodynamic analyses show that the substitutional Re atom acts as a trap for capturing interstitial He clusters and enhances their nucleation,while the Ta atom repulses with large He clusters(n?5),thus the growth of He cluster in the vicinity of Ta atom is not energetically favorable.Moreover,the critical content of He atoms that triggers trap mutation is decreased when Re exists,but Ta raises the threshold of this transition,suggests Re can facilitate the evolution of He clusters while Ta inhibits their further growth to huge bubbles.These results are contributed to the understanding of nucleation and evolution of He clusters in a atomic level and expected to provide sound explanation of recent irradiation experiments on W-Re and W-Ta alloys.