Southwest University of Science and Technology

About: Southwest University of Science and Technology is a education organization based out in Mianyang, China. It is known for research contribution in the topics: Adsorption & Graphene. The organization has 10017 authors who have published 8923 publications receiving 94850 citations. The organization is also known as: Xīnán Kējìdàxué.

Aluminum–organophosphorus hybrid nanorods for simultaneously enhancing the flame retardancy and mechanical properties of epoxy resin

Abstract: New aluminum–organophosphorus hybrid nanorods (AOPH-NR) have been prepared by reacting aluminum hydroxide (ATH) with dibenzylphosphinic acid (DBPA) with aluminum hydroxide (ATH) and used to prepare nanocomposites with epoxy resin. In order to determine the structure–property relationship of these composites, several other phosphinic acids of the general formula (R(CH2)n)2POOH (R = ester, allyl, nitrile, n = 1 or 2), and corresponding AOPHs were synthesized. FTIR, Raman, TGA, and XRD examinations showed that only AOPH-NR possesses a highly hybrid structure and high thermostability. SEM and TEM confirmed the nanorod morphology of AOPH-NR. The formation mechanism can be described as a decomposing–reforming process. This characteristic causes AOPH-NR to exhibit superior properties. Limiting oxygen index (LOI) determination and cone calorimeter analysis showed that the incorporation of only 4.25 wt% AOPH-NR remarkably improved the LOI value to as much as 28.0 and led to a 23% reduction in peak heat release rate (PHRR). Dynamic mechanical analysis (DMA) indicated that the mechanical properties of epoxy resin were also improved by incorporating AOPH-NR. In this way, the aluminum–organophosphorus hybridization via reacting ATH with specific organophosphinic acids shows promise as a means of improving flame retardancy and mechanical properties simultaneously. The thermal and anti-flaming properties of composites, combined with the properties of AOPHs, allowed us to discover the important role that the release and migration of phosphorus species plays in fire-retarding materials. This provides a new insight into the design of high-performance flame retardants.

Microencapsulated Paraffin Phase-Change Material with Calcium Carbonate Shell for Thermal Energy Storage and Solar-Thermal Conversion.

Abstract: A series of microencapsulated phase-change materials (MEPCMs) based on paraffin core and calcium carbonate (CaCO3) shell were synthesized, and the effect of emulsifier type and pH value on morphology, structure, and properties of paraffin@CaCO3 MEPCMs were investigated. The results showed that CaCO3 shell was formed in vaterite and calcite crystalline phase when emulsifier was sodium dodecyl benzene sulfonate and styrene-maleic anhydride (SMA), respectively. When sodium dodecyl sulfate was used as an emulsifier, both vaterite and calcite CaCO3 were formed. The forming mechanism of emulsifier type on CaCO3 crystalline phase was studied. Furthermore, phase-change enthalpy and leakage rate of MEPCMs were related with the type of emulsifier and the pH value of the emulsion. With optimum condition of SMA as emulsifier and pH value of 7, paraffin@CaCO3 MEPCMs had an encapsulation ratio at 56.6% and leakage rate at 2.88%, illustrating its considerable heat storage capability and leakage-prevention property. The 50 heating-cooling cycles test indicated that the MEPCMs owned excellent thermal reliability. The thermal conductivity of MEPCMs was significantly improved due to the existence of CaCO3 shell. In addition to excellent thermal storage ability, the paraffin@CaCO3 MEPCMs also owned good mechanical property and light-to-heat energy conversion efficiency. The characteristics of MEPCMs indicated its potential application in solar energy resource.

A third order exponential time differencing numerical scheme for no-slope-selection epitaxial thin film model with energy stability

Abstract: In this paper we propose and analyze a (temporally) third order accurate exponential time differencing (ETD) numerical scheme for the no-slope-selection (NSS) equation of the epitaxial thin film growth model, with Fourier pseudo-spectral discretization in space. A linear splitting is applied to the physical model, and an ETD-based multistep approximation is used for time integration of the corresponding equation. In addition, a third order accurate Douglas-Dupont regularization term, in the form of $-A \dt^2 \phi_0 (L_N) \Delta_N^2 ( u^{n+1} - u^n)$, is added in the numerical scheme. A careful Fourier eigenvalue analysis results in the energy stability in a modified version, and a theoretical justification of the coefficient $A$ becomes available. As a result of this energy stability analysis, a uniform in time bound of the numerical energy is obtained. And also, the optimal rate convergence analysis and error estimate are derived in details, in the $\ell^\infty (0,T; H_h^1) \cap \ell^2 (0,T; H_h^3)$ norm, with the help of a careful eigenvalue bound estimate, combined with the nonlinear analysis for the NSS model. This convergence estimate is the first such result for a third order accurate scheme for a gradient flow. Some numerical simulation results are presented to demonstrate the efficiency of the numerical scheme and the third order convergence. The long time simulation results for $\varepsilon=0.02$ (up to $T=3 \times 10^5$) have indicated a logarithm law for the energy decay, as well as the power laws for growth of the surface roughness and the mound width. In particular, the power index for the surface roughness and the mound width growth, created by the third order numerical scheme, is more accurate than those produced by certain second order energy stable schemes in the existing literature.

H∞ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays.

Abstract: The problem of H∞ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays is investigated in this paper. The transition probabilities under consideration are time-varying, i.e., Markovian chain is nonhomogeneous. By using the Lyapunov functional approach and reciprocally convex technique, a less conservative delay-dependent bounded real lemma is developed in terms of linear matrix inequalities. Moreover, a sufficient condition for the existence of the desired filter which guarantees the stochastic admissibility and the H∞ performance index of the resulting filtering error system is presented. Numerical examples are employed to show the usefulness of the proposed results.