Ruiz Caballero, José L.

Profile Picture

Filters

2010 - 20172
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    PublicationRestricted
    Experimental and theoretical study of solubility of 1, 3, 5-trinitrohexahydro-S-triazine (Rdx) In alcohols
    (2010) Ruiz Caballero, José L.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Román Velázquez, Félix R.; Mina Camilde, Nairmen; Santana Vargas, Alberto; Department of Chemistry; Briano Peralta, Julio G.
    The solubility of 1,3,5-trinitrohexahydro-s-triazine (RDX) in different alcohols were measured by HPLC, DSC, GC/MS, and NMR. The conformation of RDX in acetone-D6 solution was verified by vibrational studies using Raman spectroscopy. The thermodynamic parameters and conformations were calculated using density functional theory, Hartree-Fock, and the polarized continuum model. Raman studies suggest that the RDX molecule has approximate C3v symmetry in solution, with alteration of the attached NO2 groups. The solubility of RDX in alcohols (ethyl alcohol, 2-methyl-1-propanol, 2-propanol and 1-butanol) has been determined at six different temperatures, 15, 20, 25, 30, 35, 40°C. From the solubility data, the values of thermodynamic functions such as Enthalpy (ΔsolvH), Entropy (ΔsolvS) and free energies of solutions or solvation (ΔsolvG) were obtained. In the calculation, different basis sets for DFT and HF methods are reported for the geometry, energy, and Gibbs solvation energy of the high explosive in the gas phase and dissolved in alcohols, as previously mentioned. The Polarizable Continuum model (PCM) has been applied to investigate the effect of the alcohols medium on these AAARDX, AAE-RDX and EEE-RDX conformers. The inclusion of a solvent reaction field has a strong influence on the Gibbs free energy of solvation and on calculation of molecular properties. The PCM model was consistent with the experimental observations, the RDX in AAA conformation was predicted to be strongly favored in a condensed dielectric medium excluding that the distortion associated with the NO2 groups has not been found.
  • Thumbnail Image
    PublicationRestricted
    Preparation and study of thin RDX films standards on various substrates deposited by spin coating technology
    (2017-05) Ruiz Caballero, José L.; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Mina Camilde, Nairmen; Santana Vargas, Alberto; Infante Castillo, Ricardo; Department of Chemistry; Rodríguez Solís, Rafael A.
    The highly energetic material (HEM) hexahydro-1,3,5-trinitro-s-triazine, also known as RDX, has two stable conformational polymorphs at room temperature: α-RDX (molecular conformation of –NO2 groups: axial-axial-equatorial) and β-RDX (molecular conformation of –NO2 groups: axial-axial-axial). Both polymorphs can be formed by crystallization upon deposition on stainless steel (SS) and gold (Au) substrates using a spin coating methodology. α-RDX is the most stable crystal form at room temperature and ambient pressure. However, β-RDX, which has been reported to be difficult to obtain in bulk form at room temperature, was readily formed. Reflection-absorption infrared spectroscopy (RAIRS) measurements of RDX-coated substrates provided spectral markers that were used to distinguish between the conformational polymorphs on large surface areas of the substrates. Raman spectroscopy was employed to examine small areas where the intensity is proportional to the height of the structures for RDX. Spectral features were interpreted and classified by using principal component analysis (PCA). The results of these spectral analyses provided good correlation with the values reported in the literature. Optimized conditions to generate nearly only β-RDX crystalline films using increasing rotational speeds on these substrates were obtained. PCA was also applied to predict percentages of polymorphs present in experimental samples. On the other hand, the optical properties for crystalline films of the highly energetic material (HEM) previously cited as RDX, deposited on gold (Au) and stainless steel (SS) substrates are also presented. The optical properties obtained in the present study correspond to thin film samples of predominantly β-RDX polymorph. The infrared spectroscopic intensities measured showed significant differences in the -RDX crystalline films deposited on the two substrates with respect to the calculated real part of refractive index. The β-RDX/Au crystalline films have a high dynamic response, which is characterized by the asymmetric stretching mode of the axial nitro groups, whereas for the β-RDX/SS crystalline films, the dynamic response was mediated by the –N–NO2 symmetric stretch mode. This result provides an idea of how the electric field vector propagates through the β-RDX crystalline films deposited on the two substrates. Applications for the results obtained suggest the modification of existing vibrational spectroscopy-based spectral libraries for defense and security applications. Understanding the effects of polymorphism of HEMs will result in the attainment of higher confidence limits in the detection and identification of explosives especially at trace or near trace levels.