scholarly journals The Effect of CuO on the Thermal Behavior of the High-Energy Combustion Agent of the Al/MnO2 System

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Hao Wang ◽  
Tao Guo ◽  
Wen Ding ◽  
Miao Yao ◽  
Xiang Fang ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Theoretical Calculations ◽  
High Energy ◽  
Gas Content ◽  
Scanning Calorimetry ◽  
Enthalpy Changes ◽  
Endothermic Reactions ◽  
High Temperature Area ◽  
Experimental Findings ◽  
Heat Released

In this work, the effect of CuO addition into the high-energy combustion agent of Al/MnO2 system was studied. First, the combustion experiments of five samples with different contents had been carried out, in which CuO was found capable of influencing the flame ejection to a great extent. Then, in order to find out the underlying reasons, CuO effects on the thermal behavior of Al/MnO2 system were analyzed via theoretical calculations of Gibbs free energy and enthalpy changes. In addition, field emission scanning electron microscopy (FE-SEM) that could characterize the mixture morphology and thermogravimetric-differential scanning calorimetry (TG-DSC) that could indentify the exothermic and endothermic reactions and measure mass change were carried out. Finally, on the basis of all experimental findings, it was suggested that addition of CuO into Al/MnO2 system could result in dramatic increase of gas content throughout the reaction and the consequent high pressure. Also, speed of flame injection and heat released in the high-temperature area would thus be conducive to the continuous exothermic behavior of the reaction.

Microstructures and Synthesis of Noble Metal-Based Bulk Metallic Glasses (Zr-Be-Ni-Ti)

2016 ◽  
Vol 17 ◽  
pp. 1-6
Author(s):  
M. Abo-Elsoud
Keyword(s):  
Metallic Glasses ◽  
Thermal Analyses ◽  
Bulk Metallic Glasses ◽  
High Energy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Stage Crystallization ◽  
Energy Ball ◽  
Experimental Findings

High-energy ball-milling in hexane medium was employed to prepare Nobel Zr-based bulk metallic glasses (BMGs) alloy of three different nominal compositions Zr47Be23Ni15Ti15, Zr50Be20Ni15Ti15 and Zr52Be18Ni15Ti15, numbers indicate at.%). The glass forming ability was found to increase with decreasing Zr and increasing Be content, which can be ascribed to the enhanced atomic size mismatch of the constituents on Be addition. Amorphous Zr47Be23Ni15Ti15 powder undergoes two-stage crystallization with onset temperatures at 640 and 700 K and glass transition temperature Tg at 566 K. In contrast, the Zr50Be20Ni15Ti15 and Zr52Be18Ni15Ti15 samples remained crystalline to a certain extent even after prolonged milling and contained FCC Zr crystallites. Structural characterization was done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, thermal analyses were performed by means of differential scanning calorimetry (DSC) thermogram to justify the experimental findings.

scholarly journals Preparation and DFT Study for New Three-Ring Supramolecular H-Bonded Induced Liquid Crystal Complexes

2021 ◽  
Vol 9 ◽  
Author(s):  
Sayed Z. Mohammady ◽  
Daifallah M. Aldhayan ◽  
Mohamed Hagar
Keyword(s):  
Liquid Crystal ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Compact Groups ◽  
Scanning Calorimetry ◽  
Thermal Stabilities ◽  
Functional Theory ◽  
Enthalpy Changes ◽  
Bonding Interaction ◽  
Chain Lengths

Supramolecular three-ring Schiff base novel liquid crystal complexes have been prepared and investigated. Schiff bases of para-substituted aniline derivatives and para-pyridine carbaldehyde have been prepared and then mixed in equimolar quantities with para-alkoxy benzoic acids. On one side, the alkoxy chain length varies from 8 to 16 carbon atoms. On the other side, terminal small compact groups substituting aniline with various polarities are used. Hydrogen-bonding interaction was elucidated by FTIR spectroscopy. The mesomorphic thermal and optical characteristics of the samples were obtained by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). All samples exhibit enantiotropic mesophases. Experimental results obtained for the induced mesophases were correlated with density functional theory (DFT) theoretical calculations. The results revealed that both the polar compact groups’ polarity and the alkoxy chain lengths contribute strongly to mesomorphic characteristics and thermal stabilities of the mesophases. Surprisingly, the observed values of enthalpy changes associated with the crystalline mesomorphic transitions lie in the range of 2.2–12.5 kJ/mol. However, the enthalpy changes corresponding to the mesomorphic–isotropic transitions vary from 0.9 to 13.9 kJ/mol, depending on the polarity of para-attached groups to the aniline moiety.

THERMAL BEHAVIOR AND IGNITION OF HIGH-ENERGY MATERIALS CONTAINING B, ALB2, AND TIB2

2020 ◽  
Author(s):  
A. G. Korotkikh ◽  
◽  
V. A. Arkhipov ◽  
I. V. Sorokin ◽  
E. A. Selikhova ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal Behavior ◽  
Flux Density ◽  
Ignition Delay ◽  
Delay Time ◽  
Heat Flux Density ◽  
Ignition Delay Time ◽  
High Energy ◽  
Energy Materials ◽  
High Energy Materials

The paper presents the results of ignition and thermal behavior for samples of high-energy materials (HEM) based on ammonium perchlorate (AP) and ammonium nitrate (AN), active binder and powders of Al, B, AlB2, and TiB2. A CO2 laser with a heat flux density range of 90-200 W/cm2 was used for studies of ignition. The activation energy and characteristics of ignition for the HEM samples were determined. Also, the ignition delay time and the surface temperature of the reaction layer during the heating and ignition for the HEM samples were determined. It was found that the complete replacement of micron-sized aluminum powder by amorphous boron in a HEM sample leads to a considerable decrease in the ignition delay time by a factor of 2.2-2.8 at the same heat flux density due to high chemical activity and the difference in the oxidation mechanisms of boron particles. The use of aluminum diboride in a HEM sample allows one to reduce the ignition delay time of a HEM sample by a factor of 1.7-2.2. The quasi-stationary ignition temperature is the same for the AlB2-based and AlB12-based HEM samples.

scholarly journals Diffuse γ-ray emission toward the massive star-forming region, W40

2020 ◽  
Vol 639 ◽  
pp. A80
Author(s):  
Xiao-Na Sun ◽  
Rui-Zhi Yang ◽  
Yun-Feng Liang ◽  
Fang-Kun Peng ◽  
Hai-Ming Zhang ◽  
...  
Keyword(s):  
Cosmic Ray ◽  
High Energy ◽  
Young Star ◽  
Gas Content ◽  
Large Area ◽  
Stellar Cluster ◽  
Production Region ◽  
Star Forming ◽  
Photon Index ◽  
Young Star Clusters

We report the detection of high-energy γ-ray signal towards the young star-forming region, W40. Using 10-yr Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended γ-ray excess region with a significance of ~18σ. The radiation has a spectrum with a photon index of 2.49 ± 0.01. The spatial correlation with the ionized gas content favors the hadronic origin of the γ-ray emission. The total cosmic-ray (CR) proton energy in the γ-ray production region is estimated to be the order of 1047 erg. However, this could be a small fraction of the total energy released in cosmic rays (CRs) by local accelerators, presumably by massive stars, over the lifetime of the system. If so, W40, together with earlier detections of γ-rays from Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and 30 Dor C, supports the hypothesis that young star clusters are effective CR factories. The unique aspect of this result is that the γ-ray emission is detected, for the first time, from a stellar cluster itself, rather than from the surrounding “cocoons”.

scholarly journals Thermal Dynamic Behavior in Bi-Zone Habitable Cell with and without Phase Change Materials

Proceedings ◽  
2020 ◽  
Vol 63 (1) ◽  
pp. 41
Author(s):  
Hanae El Fakiri ◽  
Lahoucine Ouhsaine ◽  
Abdelmajid El Bouardi
Keyword(s):  
Thermal Behavior ◽  
Thermal Comfort ◽  
Phase Change ◽  
Dynamic Behavior ◽  
Phase Change Materials ◽  
Energy Performance ◽  
High Energy ◽  
Water Heater ◽  
Simplified Modeling

The thermal dynamic behavior of buildings represents an important aspect of the energy efficiency and thermal comfort of the indoor environment. For this, phase change material (PCM) wallboards integrated into building envelopes play an important role in stabilizing the temperature of the human comfort condition. This article provides an assessment of the thermal behavior of a “bi-zone” building cell, which was built based on high-energy performance (HEP) standards and heated by a solar water heater system through a hydronic circuit. The current study is based on studying the dynamic thermal behavior, with and without implantation of PCMs on envelope structure, using a simplified modeling approach. The evolution of the average air temperature was first evaluated as a major indicator of thermal comfort. Then, an evaluation of the thermal behavior’s dynamic profile was carried out in this study, which allowed for the determination of the PCM rate anticipation in the thermal comfort of the building cell.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

scholarly journals Modulation of Crystallinity through Radiofrequency Electromagnetic Fields in PLLA/Magnetic Nanoparticles Composites: A Proof of Concept

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4300
Author(s):  
Marta Multigner ◽  
Irene Morales ◽  
Marta Muñoz ◽  
Victoria Bonache ◽  
Fernando Giacomone ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Nanoparticles ◽  
Electromagnetic Fields ◽  
Biomedical Applications ◽  
Infrared Camera ◽  
Proof Of Concept ◽  
Scanning Calorimetry ◽  
Radiofrequency Electromagnetic Fields ◽  
Degradation Properties ◽  
Heat Released

To modulate the properties of degradable implants from outside of the human body represents a major challenge in the field of biomaterials. Polylactic acid is one of the most used polymers in biomedical applications, but it tends to lose its mechanical properties too quickly during degradation. In the present study, a way to reinforce poly-L lactic acid (PLLA) with magnetic nanoparticles (MNPs) that have the capacity to heat under radiofrequency electromagnetic fields (EMF) is proposed. As mechanical and degradation properties are related to the crystallinity of PLLA, the aim of the work was to explore the possibility of modifying the structure of the polymer through the heating of the reinforcing MNPs by EMF within the biological limit range f·H < 5·× 109 Am−1·s−1. Composites were prepared by dispersing MNPs under sonication in a solution of PLLA. The heat released by the MNPs was monitored by an infrared camera and changes in the polymer were analyzed with differential scanning calorimetry and nanoindentation techniques. The crystallinity, hardness, and elastic modulus of nanocomposites increase with EMF treatment.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

scholarly journals Investigation of viscoelastic properties and thermal behavior of photocurable epoxy acrylate nanocomposites

2017 ◽  
Vol 24 (5) ◽  
pp. 691-697
Author(s):  
Behzad Shirkavand Hadavand ◽  
Hossein Hosseini
Keyword(s):  
Thermal Behavior ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Cuo Nanoparticles ◽  
Epoxy Acrylate ◽  
Silane Coupling Agents ◽  
Scanning Calorimetry ◽  
Dynamic Mechanical ◽  
Acrylate Resin ◽  
Epoxy Acrylate Resin

AbstractIn this study, the dynamic-mechanical properties and thermal behavior of the nanocomposites of a photocurable epoxy-acrylate resin and CuO nanohybrid were determined. In order to improve the dispersion of CuO nanoparticles and prevention of nanoparticle migration to the surface coating, the surface of commercial nanoparticles was modified by triethoxymethylsilane (TEMS) and vinyltrimethoxysilane (VTMS) as silane-coupling agents. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) tests were then performed on CuO-filled epoxy-acrylate resins to identify the loading effect on the properties of material. The thermal stability of nanocomposites was affected slightly after incorporation of CuO nanoparticles. DMA studies revealed that filling the CuO nanoparticles into epoxy-acrylate resin can produce a significant enhancement in storage modulus, as well as a shift in the glass transition temperature. The films reinforced with the modified CuO exhibit the most significant enhancements in properties.

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