External Heating Temperature Research Articles

Mechanical properties and defects in friction stir welded acrylonitrile butadiene styrene polymer

In this research work, a butt joint between acrylonitrile butadiene styrene (ABS) sheets was made using Friction stir welding (FSW). Polymers such as ABS have great potential to be used as body parts in automotive industries because of their high strength-to-weight ratio. In the aerospace industry, polymers are preferred over metals as they can retain their properties at low temperatures and their light weight reduces fuel consumption. The objective of this research work was to investigate mechanical properties and defect characterization in weldments. Maximum weld strength achieved was 19.4 MPa which is 61% of the base material at a rotational speed of 224 r/min, travel speed of 50 mm/min, external heating temperature of 45°C, and shoulder diameter of 16 mm. The images of macro and microstructure from an optical microscope and scanning electron microscope, respectively, showed that in FSW of ABS polymer defects were mainly formed on the retreating side of the weld nugget, unlike FSW of metals having it on the advancing side. Only two experiments out of L18 experiments showed tunneling defect, i.e., Experiment no. 8 and Experiment no. 10 and four experiments showed undercutting defect, i.e., Experiment no. 6, 9, 12, and 18. By performing the Vickers microhardness test it was observed that the hardest region formed in and around the weld nugget.

The Nature of Active Sites for Plasmon‐Mediated Photothermal Catalysis and Heat‐Coupled Photocatalysis in Dry Reforming of Methane

Solar energy‐induced catalysis has been attracting intensive interests and its quantum efficiencies in plasmon‐mediated photothermal catalysis (P‐photothermal catalysis) and external heat‐coupled photocatalysis (E‐photothermal catalysis) are ultimately determined by the catalyst structure for photo‐induced energetic hot carriers. Herein, different catalysts of supported (TiO2‐P25 and Al2O3) platinum quantum dots are employed in photo, thermal, and photothermal catalytic dry reforming of methane. Integrated experimental and computational results unveil different active sites (hot zones) on the two catalysts for photo, thermal, and photothermal catalysis. The hot zones of P‐photothermal catalysis are identified to be the metal–support interface on Pt/P25 and the Pt surface on Pt/Al2O3, respectively. However, a change of the active site to the Pt surface on Pt/P25 is for the first time observed in E‐photothermal catalysis (external heating temperature of 700 °C). The hot zones contribute to the significant enhancements in photothermal catalytic reactivity against thermocatalysis. This study helps to understand the reaction mechanism of photothermal catalysis to exploit efficient catalysts for solar energy utilization and fossil fuels upgrading.

Reliability analysis of the cutting tool in plasma-assisted turning and prediction of machining characteristics

ABSTRACT Heat-assisted machining (HAM) is an alternative method for the successful machining of difficult-to-cut aerospace superalloys. However, the tool wear progression in HAM has been substantially affected by the workpiece external heating temperature along with the machining parameters. It is of great importance to precisely estimate the tool wear progression and reliability of the cutting tool operated in HAM to enhance the machining efficiency and economics. Hardened AISI4340 alloy steel was machined under plasma-arc heating conditions with WC cutting tools. The experimental results reviled that for 200°C of preheating temperature, the surface roughness noted as 2.03µm and tool life as 870s. While at 600°C, the surface roughness as 1.68µm, and tool life extended to 1885s to reach the set threshold value of 0.4mm flank wear. Notch wear as dominant tool wear mechanism at 200°C and 400°C, while it is diffusion wear at 600°C. On the establishment of stochastic tool life distribution and reliability models, tool lives measured at all heating conditions followed a Weibull distribution. Empirical models for tool wear, surface roughness, and material removal rate were postulated and validated statistically as-well-as experimentally. The derived reliability and empirical models can be used to predict the machining characteristics to enhance its performance.

Methane Dry Reforming over Ni/Al2O3 Catalyst in Spark Plasma Reactor: Linking Computational Fluid Dynamics (CFD) with Reaction Kinetic Modelling

Efficient processes are needed for the valorisation of major greenhouse gases, methane and carbon dioxide, and electrification and energy storage are highly desired as well. Plasma based dry reforming provides the answer in all areas, as fast switch -on and -off times could use excess grid electricity to produce valuable products and decrease the carbon footprint. The reaction was studied in a non-equilibrium atmospheric pressure spark discharge reactor, which achieves higher yields than DBD reactors. CH4 and CO2 feed mixture at different ratios was converted to H2 and CO with high selectivity, achieving conversions of 85% for CH4 and 75% for CO2. The syngas production energy cost was 315 kJ/mol, indicating 20% of input energy transferred to chemical energy. CO2 plasma regeneration and cyclic reaction operation was proposed to tackle the coking problem. With the intent of improving the yield, gaseous plasma was coupled with a solid Ni/Al2O3 heterogeneous catalyst, wash-coated on porous alumina foam material. The effects of specific energy input, external heating temperature and gas flow rate were also screened. In addition, a CFD and chemical kinetics model was developed in order to further investigate the system, which achieved good agreement with the experiments using relatively simple chemistry.

Hydrogen for Fuel Cells: Effect of Copper and Iron Oxides on the Catalytic Hydrolysis and Hydrothermolysis of Ammonia Borane

Hydrogen storage and generation systems based on ammonia borane (NH3BH3) were considered. Data on the kinetics of H2 evolution during the catalytic hydrolysis and hydrothermolysis of NH3BH3 involving CuO, Fe2O3, and CuFe2O4 were presented. The products of the reduction of these oxides in the reaction medium were studied by XRD analysis. The catalytic hydrothermolysis of NH3BH3 in the presence of CuFe2O4 is a potentially highly efficient method for hydrogen production for fuel cells at an external heating temperature of 90°C.

Fast hydrogen generation from solid NH3BH3 under moderate heating and supplying a limited quantity of CoCl2 or NiCl2 solution

Abstract New results of an investigation of NH3BH3 dehydrogenation with supplying a limited quantity of aqueous solution of a catalyst precursor to a solid-state bed of the hydride particles with subsequent external heating at 40–90 °C are presented. Measurements of the reaction layer temperature and the amount of the evolved hydrogen have shown that at external heating temperature higher than 85°С there was acceleration of the first stage of the process, the highly exothermic catalytic hydrolysis of a portion of ammonia borane, which resulted in a stronger heating of the reaction layer and the start of NH3BH3 thermolysis. This type of process is referred to as hydrothermolysis. A TEM, ATR FTIR, and XRD investigation has shown that in the reaction medium the metal chlorides become reduced to an amorphous catalytically active phase. During this process, ammonia reacts with chlorides to form NH4Cl. All of this leads to increased rate of hydrogen generation and hydrogen yield. Gravimetric hydrogen capacity of 7.6 wt% and the average rate of H2 evolution of 39 ml·gcomp.−1min−1 have been achieved at molar ratios of NH3BH3/MCl2 = 50 (M = Co, Ni) and H2O/NH3BH3 = 2 and at external heating of 85°С.

Plasma Catalytic Removal of p-Xylene from Air Stream Using γ-Al2O3 Supported Manganese Catalyst

The abatement of dilute p-xylene (500 ppm) from a contaminated air stream (2 L min−1) by the non-thermal plasma in combination with an ozone decomposing catalyst (pelleted Mn/γ-Al2O3) was investigated. The reactor performance was evaluated in terms of p-xylene conversion, CO x selectivity and ozone emission with and without external heating. Generally, the removal of p-xylene gradually increased with increasing the applied voltage from 16 to 22 kV (peak height). As the catalyst was used (i.e., packed inside the plasma active region), the reactor was able to remove ca. 82% of p-xylene at 22 kV, compared to 54% done by plasma alone. Under the same plasma-catalytic condition, the removal of p-xylene was successfully achieved (ca. 96%) by heating up the reactor to 150 °C. Not only was the conversion improved, but also the mineralization of p-xylene was also enhanced considerably by the mild thermal heating, increasing the CO2 selectivity from ca. 41 to 59%. The ozone emission measurement showed that ozone formed in plasma was readily catalytically decomposed on Mn/γ-Al2O3 at above 16 kV, even without external heating. As revealed by the reactor infrared thermographic images, the plasma-induced surface temperature of the catalyst was far higher than the external heating temperature (i.e., 150 °C), facilitating the catalytic degradation of ozone and reducing the formation of byproducts. Additionally, no organic compounds have been found on the spent catalyst, avoiding the possibility of catalyst deactivation during the course of experiment.

Preparation and thermal properties of SAT-CMC-DSP/EG composite as phase change material

In this study, a series of SAT-CMC-DSP/EG (sodium acetate trihydrate-disodium hydrogen phosphate dodecahydrate-carboxyl methyl cellulose/expanded graphite) composite phase change materials (CPCMs) with different mass ratio of EG was prepared. The influence of EG addition on the thermal conductivity was examined using transient plane source method, thermal properties including melting temperature and latent heat were evaluated using differential scanning calorimetry (DSC), the latent heat storage and release time and the degree of supercooling were obtained using cooling curves method. The results showed that as a thermal conductivity enhancer, EG could improve the thermal conductivity of SAT effectively. At the same time, it brings some problems with the increase of EG mass fraction, such as lower enthalpy and higher subcooling degree. The SAT-CMC-DSP/EG with 3wt% EG was considered as the most suitable choice with the melting temperature, latent heat, thermal conductivity and degree of supercooling were 58.1°C, 210.7kJ/kg, 1.37W/(mK) and 2°C. The impact of external heating temperature on the composite PCM containing 3wt% EG was tested. The results showed that the heating temperature is should better not exceed 78°C. Furthermore, thermal cycling test results indicated that SAT-CMC-DSP/EG showed a good thermal reliability.

Modifications in the Thermicity of the Pyrolysis Reactions of ZnCl2-Loaded Wood

The influence of the loaded zinc chloride content (0–11 wt %, dry sample basis) on the pyrolysis of beechwood particles packed in a bench-scale bed was studied. Given an external heating temperature of 655 K, the temporal profiles of the thermal field showed maximum values progressively increasing from 683 to 790 K as the catalyst content was increased from 0 to about 5 wt %. Based on cumulative char and water yields increasing from about 51 to 70 wt % and yields of condensable organics decreasing from about 35 to 15 wt %, the enhancement in the global exothermicity of the conversion process can be attributed to the successive predominance of dehydration with cross-linking reactions over depolymerization reactions. The exothermic effects were found to be qualitatively similar to but quantitatively lower than those associated with a sulfuric acid treatment. For higher acid contents and both additives, the noncatalytic effects associated with their loading were also found to contribute significantly to the ...

The Influence of Temperature and Load on Dry Sliding Wear and Friction Property of Low Metallic Friction Material

This study investigates the influence of temperature and load on the dry sliding property of interface between brake friction material with low metallic formulation and gray cast iron disc. Full factorial design was employed to conduct pin-on-disc wear tests to attain wear and friction response under external heating temperature and applied load ranging from 25-175°C and 50-500N(0.35-3.5MPa), respectively. The analysis of experiment results shows the effect of load on wear rate is almost linear. Wear rate exhibits an increase followed by decrease trend with applied load. Friction coefficient is positively affected by external heating temperature but almost independent of applied load. Quadratic regression is conducted to fit the influence of temperature and load on wear rate and friction coefficient and the result shows sound fitting effect.

Numerical Simulation of Heat Transfer Characteristics for Two Metallic TPS Structures

Two structures of metallic thermal protection system(TPS) for hypersonic vehicle were presented. One model was a multi-layer construction and the other has cavities in the metallic layer. Numerical simulations were conducted on the three-dimensional TPS models using CFD software of Gambit and Fluent. Two heating temperatures of 1073K and 773K with constant temperature and isothermal boundary conditions were considered. Heat transfer was treated as single conductivity and thermal radiation effect was not involved. The results of simulation investigation showed that: The metallic layer had poor capability to restrict the heat conductivity. Heat was easier to transfer across the bracket into the internal part of the TPS. The ability of cavities in metallic layer to resist heat conductivity was limited. The temperature-heating time variation pattern was similar for different external heating temperature. Internal cooling was important for the TPS. The thermal radiation effect on the TPS would be focused in further research.

Preparation of ultrafine PZT powders by ultrasonic spray combustion synthesis (USCS)

Ultrafine PZT powders were synthesized by the ultrasonic spray combustion method from Pb(NO 3) 2, ZrO(NO 3) 2· xH 2O, TiO(NO 3) 2, and CH 6N 4O precursors. The molar ratio of oxidizer and fuel was 1:1 for the maximum exothermic reaction. The DTA/TGA curves of the precursor mixture showed exothermic peaks for combustion. The external heating temperature for ultrasonic spray combustion synthesis was 800 °C. The ultrasonically generated droplets are filtered using a metal screen filter and Reynolds number was kept at a value of 1200 to avoid coagulation of droplets in the system. XRD analysis showed that the as-received powders without calcination were PZT. The lattice parameters calculated by X-ray methods were a= b=3.997±0.001 Å, c=4.147±0.001 Å. SEM and TEM observations showed that the particles of the synthesized tetragonal PZT powders had a 100–200 nanometer size with uniform spherical shape.