Military School of Engineering
La Paz, Bolivia
Time filter
Source Type

Elbasuney S.,Military School of Engineering
Powder Technology | Year: 2017

Inorganic hydroxides represent more than 50% of flame retardants (FRs) sold globally. This is due to their low cost, low toxicity, and minimum corrosivity. Aluminium tri-hydroxide (ATH) is the largest FR in use. This paper reports on a novel continuous flow fabrication of nanoscopic ATH with consistent product quality. TEM micrographs demonstrated nanoplate structure with 25 nm size. XRD diffractogram revealed highly pure crystalline structure free from defects and any interfering substances. The made-up ATH has the potential to deliver a flame retardant action (heat sink action) to the hosting polymer by absorbing heat, releasing water, and forming a protective oxide layer (Al2O3). This oxide layer can prevent further polymer degradation. The effectiveness of ATH heat sink action was evaluated with thermal analysis techniques including TGA and DSC. The phase transition of ATH to corresponding oxides during its endothermic decomposition was verified with XRD. The synergism between the ATH heat sink and intumescent action (provoked with a phosphorous-based FR agent known as AP750) was employed to develop self-extinguishing multi-component epoxy nanocomposite. The developed nanocomposite was able to resist direct flame source at 1700 °C; it demonstrated superior flammability performance using cone calorimeter testing. The peak heat released was decreased by 58%, and the time to peak heat released was extended by 35%. The synergism between ATH and AP750 was ascribed to the ability of the protective oxide layer (Al2O3) (resulted from ATH decomposition) to crosslink the phosphoric acid chains (resulted from AP750 decomposition) and to form aluminium phosphate (AlPO4). This catalytic action was demonstrated by conducting XRD of the developed char layer. © 2016 Elsevier B.V.

Elbasuney S.,Military School of Engineering
Applied Surface Science | Year: 2017

A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180–240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This manuscript revealed the state of the art for the real development of stable colloidal mono-dispersed particles with controlled surface properties. © 2017 Elsevier B.V.

Nian Y.J.,Military School of Engineering
Zhonghua shao shang za zhi = Zhonghua shaoshang zazhi = Chinese journal of burns | Year: 2016

The accurate diagnosis of burn depth is one of the important problems in the field of burn surgery. The diagnosis accuracy rate is directly related to the treatment plan and effect. The existed clinical diagnosis methods mainly depend on the experience of burn surgeon, making the accuracy rate from 50% to 65%. In order to improve the accuracy rate of clinical burn depth diagnosis, a large number of diagnosis methods based on imaging are proposed, however, all of the methods are still in the stage of experimental research. In this paper, the research advances on the diagnosis techniques of burn depth are summarized, both the advantages and the shortcomings are pointed, and the development trend of diagnosis techniques of burn depth is expected.

Zhang H.-F.,Military School of Engineering | Sun Z.,Chongqing University | Sang W.-L.,Southwest University | Sang W.-L.,CAS Institute of Theoretical Physics | Li R.,Xi'an Jiaotong University
Physical Review Letters | Year: 2015

With the recent LHCb data on ηc production and based on heavy quark spin symmetry, we obtain the long-distance matrix elements for both ηc and J/ψ productions, among which, the color-singlet one for ηc is obtained directly by the fit of experiment for the first time. Using our long-distance matrix elements, we can provide good description of the ηc and J/ψ hadroproduction measurements. Our predictions on J/ψ polarization are in good agreement with the LHCb data, explain most of the CMS data, and pass through the two sets of CDF measurements in the medium pt region. Considering all the possible uncertainties carefully, we obtained quite narrow bands of the J/ψ polarization curves. © 2015 American Physical Society.

Cui C.-Y.,Military School of Engineering | Liu Y.-L.,National University of Defense Technology | Huang M.-Q.,National University of Defense Technology
European Physical Journal C | Year: 2013

We investigate whether the newly observed narrow resonance Zc(4025) can be described as a D*D̄* molecular state with quantum numbers JP=1+. Using QCD sum rules, we consider contributions up to dimension six in the operator product expansion and work at leading order of αs. The mass obtained for this state is (4.05±0.28) GeV. It is concluded that the D*D̄* molecular state is a possible candidate for Zc(4025). © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Chen D.-Q.,Military School of Engineering
Signal, Image and Video Processing | Year: 2016

The recovery of images from the observations that are degraded by a linear operator and further corrupted by Poisson noise is an important task in modern imaging applications such as astronomical and biomedical ones. Gradient-based regularizers involving the popular total variation semi-norm have become standard techniques for Poisson image restoration due to its edge-preserving ability. Various efficient algorithms have been developed for solving the corresponding minimization problem with non-smooth regularization terms. In this paper, motivated by the idea of the alternating direction minimization algorithm and the Newton’s method with upper convergent rate, we further propose inexact alternating direction methods utilizing the proximal Hessian matrix information of the objective function, in a way reminiscent of Newton descent methods. Besides, we also investigate the global convergence of the proposed algorithms under certain conditions. Finally, we illustrate that the proposed algorithms outperform the current state-of-the-art algorithms through numerical experiments on Poisson image deblurring. © 2016 Springer-Verlag London

Elbasuney S.,Military School of Engineering | Mostafa H.E.,Military School of Engineering
Particuology | Year: 2015

Abstract Nanoparticles can provide flame retardance to hosting polymers and act as nano fire extinguishers. Hydroxyapatite (Ca5(OH)(PO4)3) (HA) is not hygroscopic, and is thermally stable up to 800 °C, with 18.5 wt% phosphorous content. It is this high phosphorous content that can provide HA with flame retardant properties. In this paper, we report on the continuous synthesis of ultrafine HA using a hydrothermal synthesis technique. The HA surface properties were changed from hydrophilic to hydrophobic by post-synthesis surface modification. The ratio of the HA nanoparticles and an intumescent agent known as Exolit AP750 was investigated to yield a self-extinguishing multi-component epoxy nanocomposite for extended application under extreme fire conditions. The HA/AP750/epoxy nanocomposite was able to resist a flame at 1700 °C and self-extinguish after the flame had been removed. The nanocomposite showed an enhanced flammability performance in standard cone calorimetry testing and formed a compact and cohesive protective char layer with a 50% decrease in peak heat released compared with virgin epoxy. Our aim was to establish the use of HA as an effective nanofiller with phosphorous-based flame retardant properties. The surface of this nano fire extinguisher was modified effectively with different surfactants for enhanced compatibility with different polymeric matrices. © 2015 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.

Elbasuney S.,Military School of Engineering
Particuology | Year: 2015

Abstract Aluminum-oxide-hydroxide (AlOOH) is a clean and non-toxic flame retardant. There have been many trials for the fabrication of ultrafine AlOOH. Two main approaches exist for nano-AlOOH synthesis: reactive precipitation and batch hydrothermal synthesis. Both approaches are laborious and time consuming with poor control of particle morphology. We report on the novel continuous flow manufacture of AlOOH nanorods with controlled morphology (particle size and shape) by hydrothermal synthesis. AlOOH was harvested from its mother liquor (colloidal solution) using poly(acrylamide-co-acrylic acid) copolymer as a flocculating agent. The developed AlOOH shape and size, crystalline phase, thermal stability, and endothermic heat sink action were investigated by transmission electron microscopy, X-ray diffractometry, thermogravimetric analysis, and differential scanning calorimetry, respectively. The phase transition of AlOOH to Al2O3 was demonstrated by conducting different X-ray diffractometry scans from 400 to 700 °C. These results may provide an option for the continuous synthesis of nano-AlOOH as a clean and non-toxic flame retardant with excellent thermal stability. Consequently, enhanced flammability properties can be achieved at low solids loading. © 2015 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.

Elbasuney S.,Military School of Engineering
Powder Technology | Year: 2014

There are well known problems with the dispersion of inorganic nanoadditives into organic medium as they tend to aggregate and agglomerate, therefore the particles act like micron sized particles rather than nanoparticle scale. In this paper, we investigated the differences between dispersing dry and colloidal TiO2 nanoparticles into epoxy resin. The dry TiO2 was commercially obtained P25 and freeze dried TiO2 from continuous hydrothermal synthesis (CHS). The colloidal TiO2 was produced from CHS but without a drying stage. Specific parameters including loading level (1-30wt.%), mechanical mixing (2-60min), polymer heating (25-80°C), and dry and wet addition were investigated. The nanoparticle dispersion was investigated with SEM and quantified by using Labview image analysis (National Instruments), in order to quantify the characteristic aggregate dimensions such as perimeter, maximum feret diameter, and size. TiO2 nanoparticles were formulated and surface modified with dodecenyl succinic anhydride (DDSA) by using CHS technique. Online phase transfer was used to produce colloidal DDSA-titania dispersed in toluene which could then be directly integrated into epoxy resin. This approach showed enhanced nanoparticle dispersion (nanoscale dispersion) with minimum aggregation compared with the dispersion of dry nanoparticles. Furthermore, this approach enabled the elimination of nanoparticle freeze drying and the redispersion of aggregated dry nanoparticles into polymeric matrix. © 2014 Elsevier B.V.

Elbasuney S.,Military School of Engineering
Powder Technology | Year: 2015

One of the significant impacts of nanotechnology on polymeric material's flammability is the achievement of polymer nanocomposites (PNCs). Layered double hydroxide (LDH) is one of the most promising synthetic clays for PNC fabrication. A novel continuous flow method for LDH synthesis via controlled hydrothermal conditions has been recently reported. This paper reports on fine tuning surface chemistry of LDH via surface modification with different surfactants in a continuous flow manner. LDH surface properties were changed from hydrophilic to hydrophobic, and the developed particles were harvested from the water phase to the organic phase. The synthesized LDH has the potential to deliver a flame retardant action (as a heat sink material) to the hosting polymer by absorbing heat, releasing water, and forming a protective oxide layer which can prevent further degradation. The heat sink action of synthesized LDH was evaluated with thermal analysis techniques. The phase transition of LDH to corresponding oxides during its endothermic decomposition was investigated with XRD. This is the first time LDH has been surface modified continuously and its FR action as well as its phase transition has been examined. This paper might open the route for LDH as nano-filler with flame retardant properties. Surface modification was reported to enhance the dispersion characteristics of inorganic nanoparticles into the hosting polymer. Therefore enhanced flammability performance can be achieved at low solid loading level. © 2015 Elsevier B.V.

Loading Military School of Engineering collaborators
Loading Military School of Engineering collaborators