Increasing Heating Rate Research Articles

Effect of thermal debinding and sintering parameters on the mechanical properties of 4605 MIM compact using the RSM

ABSTRACT In metal injection moulding (MIM) process, improper debinding or sintering process is mainly responsible for forming defects in final parts. In this study, the effects of thermal debinding and sintering parameters on the physical and mechanical properties of low alloy steel parts produced by the MIM process are investigated. For this reason, the design of experiments was done using the central composite design (CCD) method with parameters of 3–7 °C/min for heating rate, 1–3 h for sintering time, and 1200–1300 °C for temperature. The density, strength, hardness, and elongation of the sintered parts were measured for each experiment. The results showed that among the process variables, the heating rate has the most significant effect on the properties mentioned above. Also, the impact of sintering temperature showed to be more significant than the sintering time. Finally, it was observed that with the increase in the thermal debinding rate from 3 to 7 °C/min, the relative density decreased by 3%, and elongation decreased from 10 to 4%. As for the strength, there is an optimum point of heating rate after which, with the increase of heating rate (from 5 to 7 °C/min), the strength decreases significantly by 70 MPa.

Determination of kinetic triplet, thermal degradation behaviour and thermodynamic properties for pyrolysis of a lignocellulosic biomass

Kinetic triplet, thermal degradation behaviour and thermodynamic properties of peanut shells were determined on the basis of non-isothermal thermogravimetric experiments conducted at three different heating rates under N2 atmosphere. A single differential peak was observed for the devolatilization stage. The kinetic triplet of devolatilization stage was determined using Coats-Redfern and a combined method consisting the utilization of isoconversional and Criado methods. Kinetic validation revealed that the kinetic triplet determined using the combined method described the experimental values more precisely. The reaction mechanism ascertained by the combined method was D5-D3 combination. The Ea value was strong function of conversion, and computed using isoconversional methods (Boswell, Flynn-Wall-Ozawa, Starink, Tang) between 169 and 268 kJ/mol. Entalphy, entrophy and Gibbs energy changes were computed in 164–259 kJ/mol, −37–141 J/(mol.K) and 173–187 kJ/mol ranges, respectively. The comprehensive pyrolysis index values were also calculated, and shown to increase with increasing heating rate.

Combustion characteristics and kinetic analysis of oil sludge with CaO additive

Combustion of High-sulfur oil sludge (OS) blended with CaO can significantly reduce the emission of sulfur gas pollutants, but its combustion and kinetic characteristics need to be further studied. TGA experiments showed the combustion characteristics of OS were significantly changed after adding CaO. As reflected by comprehensive combustion index (S), the combustion performance of OS decreased after adding CaO, and significantly improved with the increase of heating rate. The kinetic parameters of the main combustion process of OS with CaO were calculated by the iso-conversion methods of Friedman, FWO, and Starink, respectively. Kinetic analysis results indicated the energy required for OS combustion with CaO first increased and then decreased with deepening of reaction degree. The thermodynamic parameters of ΔH, ΔG and ΔS were determined on the basis of kinetics. The negative ΔH, positive ΔG, and negative ΔS validated the combustion of OS with CaO was an exothermic and nonspontaneous process.

Mixed biochar obtained by the co-pyrolysis of shrimp shell with corn straw: Co-pyrolysis characteristics and its adsorption capability

The co-pyrolysis characteristics of shrimp shell (SS) with corn straw (CS) were investigated by comprehensive characterization to reveal the synergistic effects and further discuss the adsorption capability. TGA results showed that pyrolysis behavior and reactivity were improved with the increase of heating rate and doping ratio of CS. Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) indicated that co-pyrolysis can effectively reduce energy consumption and promote the decomposition of CaCO3. TG-FTIR and Py-GC/MS analysis indicated that the release of CH4, CO2, CO and NH3 at the doping ratio of 25% CS (75SS+25CS) was higher than that at other doping ratios, and the relative proportions of N-heterocyclics and oxygenates were lower, which was conducive to the development of pore structure for mixed biochar and effectively alleviated the pollution during co-pyrolysis process. The structure of mixed biochar was improved, confirmed by the characterizations of BET, SEM, FTIR and XRD. The mixed biochar prepared at 800 °C (75SS+25CS800) exhibited optimal porosity, aromatization and the most thorough CaCO3 decomposition. Batch adsorption experiment showed that the removal rate of 50 mg/L Cu(II) by 75SS+25CS800 was close to 100% under the dosage of 1 g/L and pH = 3–6. The adsorption process was well described by Langmuir, pseudo-second-order and Webber-Morris model, illustrating diffusion monolayer chemisorption was the main adsorption mechanism of Cu(II) on 75SS+25CS800. The maximum adsorption capacity of 75SS+25CS800 for Cu(II) was 79.77 mg/g at 35 °C. In short, this study provided a reference in optimizing the preparation process and improving the adsorption performance of mixed biochar.

Assessment of constant and time-varying temperature schemes on the convective drying characteristics of hemp leaves

In the present study, selected mathematical drying models are evaluated for describing the convective drying of hemp (Cannabis sativa L.) leaves. Drying kinetics have been experimentally investigated in a laboratory scale convective dryer for a constant airflow velocity of 1 m s-1 and air-drying temperatures of 40, 50 and 60 °C. Non-stationary temperature conditions were also investigated for the same temperature range, under different advancing time-varying temperature profiles. Weibull formula was the most suitable mathematical expression for describing the drying kinetics for both stationary and non-stationary drying conditions. Drying at increased heating rates led to a lower final moisture content compared with the constant drying temperature levels, exposing the raw material for a shorter duration to the higher air-drying temperature.

Effects of heating rate on the alloy element partitioning and mechanical properties in equiaxed α+β Ti-6Al-4V alloy

The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation of α→β in Ti-6Al-4 V alloy under solution treatment have been investigated by the experiments and phase field simulations, which reveal the evolutions of microstructure and compositions at the non-equilibrium state and well verify the experimental results. The specific results indicate that the compositions measured through electron probe micro-analysis (EPMA) under a lower heating rate are close to the equilibrium ones corresponding to the solution temperature. Heating up to the target solution temperature, as the heating rate increases, the Al content decreases and V increases in the primary α (αp) grain with a larger size, the volume fraction of αp increases and the composition gradient between αp and β phases gets steeper. The interrelated relationship among the diffusion, compositions, solution temperature and free energy of the system has been discussed in detail. Moreover, increasing the heating rate (~20.0 K/min) may help to improve the mechanical properties of the alloy by mainly adjusting the αp/βt volume fractions, αp particle size and secondary α (αs) size during the process of heating up to the solution temperature. These results may shed some light on the optimization of the knowledge-based heat treatment route.

Thermal conversion behavior and nitrogen‐containing gas products evolution during co‐pyrolysis of cow manure and coal: A thermal gravimetric analyzer/differential scanning calorimetry–mass spectrometer investigation

AbstractThe kinetics and thermal behaviors of cow manure (CM) and Meihuajing bituminous coal (MHJ) blending from room temperature to 950°C were investigated by thermal gravimetric analyzer (TGA) coupled with differential scanning calorimetry (DSC) and mass spectrometer (MS). TG curves show that the high heating rate accelerates thermal decomposition rate, and the position of differential thermal gravity (DTG) peaks shifts to a higher temperature. Owing to the heat transfer limitation phenomenon, the residual weight of CM is only 40.38% with the heating rate of 1°C/min in comparison with other heating rate. DSC takes more time to reach a steady state than TGA. Gaseous evolution curves of HCN and NH3 were obtained during the pyrolysis of blends based on TG–MS experiments. With the increased heating rate, the emissions increased a lot due to the secondary reaction of volatiles. The Eα of 1C1M obtained using Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Friedman, and Kissinger methods is within 124.58–317.18, 121.97–321.11, 150.28–331.64, and 209.26 kJ/mol, respectively. The kinetic parameters calculated based on four model‐free kinetic modeling methods shows good agreement. And the thermodynamic parameters were obtained and discussed under different conversion rates. This work is greatly important to understand the co‐prolysis mechanism of CM and coal and to design the pyrolysis reactors.

Martensite formation during heating from cryogenic temperatures – A phase-field study

A 3D elastoplastic phase-field model is used to study the effect of isochronal heating on martensitic transformation in stainless steel quenched to cryogenic temperature. The results show that the slower the heating, the larger is the martensite volume fraction developed on heating. The simulated microstructures show that the transformation is driven by autocatalysis during the early stages and by coarsening of existing martensite units during later stages of the transformation. The internal stresses are mainly relaxed by autocatalysis during the initial stages of the transformation, whereas they are relaxed by plastic deformation during the later stages of the transformation. The temperature for attaining a certain martensite fraction increases with increasing heating rate, which is consistent with a thermally activated transformation. Kissinger-like analysis of the simulated transformation curves provides an activation energy of 11.9 kJ/mol.

Effect of heating rate on the pyrolysis of camel manure

Information on the pyrolysis degradation kinetics of feedstock is critical for the design and fabrication of pyrolysis reactors. In this study, the pyrolytic behaviour of a novel biomass, camel manure, has been studied in a non-isothermal thermogravimetric analyser. The thermal analyses were performed from room temperature to 950 °C at different heating rates (10, 20, and 50°C/min) in an N2 environment (100 ml/min). The kinetic parameters of the manure components are determined using an Arrhenius model equation, and the influence of heating rate on the pyrolytic characteristics and kinetic parameters of the manure components has been examined. The results indicated that the increase in heating rates increased the starting and ending temperatures (decomposition) of manure components. The increase in heating rates shifted the ignition, peak, and burnout temperatures to higher temperatures. At the same time, the increase in heating rates improved the char yield from 22.50 to 31.51%. However, the increase in heating rates showed an insignificant effect on the kinetic parameters of the camel manure components.

Study on Pyrolysis Characteristics of Rubber Wood Based by TG and Py-GC/MS

In order to explore the formation mechanism of pyrolysis products of rubber wood, the pyrolysis characteristics of rubber wood at different heating rates were investigated by thermogravimetric analyzer (TG), and the pyrolysis behavior and distribution of pyrolysis products of rubber wood at 400, 600 and 800 °C were further analyzed by py GC / MS. The results showed that with the increase of heating rate, the heat transfer hysteresis of rubber wood pyrolysis occurred. The pyrolysis products of rubber wood mainly include acids, phenols, ketones, aldehydes and aromatic hydrocarbons. At 400 °C, the yields of phenols and aldehydes reach the maximum. At 600 °C, the yields of toluene, ethylbenzene and olefins increase, while the yields of phenols and aldehydes decrease. At 800 °C, the yields of phenols and aldehydes increase slightly. At the same time, the contents of polycyclic aromatic hydrocarbons increase with the increase of temperature, and reach the maximum at this time.

The influence of high-energy ball milling and nanoadditives on the kinetics of heterogeneous reaction in Ni-Al system

Kinetic studies were performed utilizing high-speed temperature scanner in the Ni-Al system including those with and without mechanical activation (MA) of different duration in a planetary ball mill, with and without using carbon nanoadditives (NA). The temperature profiles were taken and treated at different heating rates from 100 up to 2600 °C/min considering the influence of activation duration and the role of nanoadditive on the characteristic points of thermograms. Kissinger method allowed to evaluate activation energy (Ea) for non-activated, activated (1, 2, 3, 5 min), nanoadditive (1 wt.%) containing and nanoadditive (1 wt.%) containing mechanoactivated (1, 3, 5 min) mixtures. The beneficial influence of NA on the interaction between Ni and Al in the non-activated and moderately mechanoactivated mixtures was demonstrated. The influence of MA and NA on the microstructure features and phase formation sequence at various heating rates were revealed. For all the mixtures under study, T* characteristic temperatures (the temperature, where the maximum exothermic effect was observed) were found to increase with increasing heating rates. It was unravelled that mechanical treatment leads to significant changes in the reaction kinetics and phase formation laws. Particularly, in an activated mixture, the formation of Ni3Al is followed by NiAl intermetallic, in contrast to non-activated mixture, where the reaction proceeds only with the NiAl formation. The both MA in 1 min and addition of 1 wt.% NA decreased the activation energy of the Ni-Al reaction, exhibiting commensurate impact on the effective activation energy value of the Ni-Al system. However, > 3 min MA in the presence of 1 wt.% NA have prohibitive effect on the reaction in the Ni-Al system.

Intercritical annealing of cold-rolled ferrite-pearlite steel: Microstructure evolutions and phase transformation kinetics

The manufacturing of Dual-Phase steels includes as a crucial step the annealing of a cold-rolled ferrite-pearlite (F/P) microstructure, which involves numerous and interacting metallurgical mechanisms, namely recovery/recrystallization of ferrite, globularization, manganese enrichment, coarsening of cementite and finally austenite transformation. Present study focuses on the austenite transformation considering its interaction with the ferrite recrystallization and the influence of the chemical composition of the cementite. The behavior of a cold-rolled F/P microstructure is studied at three heating rates to induce weak and strong interactions between the mechanisms, in particular using post mortem microstructure observations but also in situ High Energy X-Ray Diffraction experiments on a synchrotron beamline.Slow heating leads to a necklace austenite distribution whereas fast heating conducts to a banded topology. This particular microstructure morphogenesis is explained by the presence of numerous intergranular (or isolated) carbides inside the ferrite matrix, inherited from the hot-rolling. Thermokinetic analysis accounting for the cementite composition shows that the pearlite islands transformation necessarily involves the partition of substitutional elements. Conversely, the dissolving isolated carbides undergo a partition/partitionless transition on heating. After the dissolution of the cementite, a final ferrite/austenite transformation takes place. The phase transformation kinetics increases with increasing heating rates, despite the thermal-activated nature of the austenite growth process. This is interpreted thanks to kinetic simulations with DICTRA software, which allow to analyze the austenite growth regimes involving or not the partition of the alloying elements.

Evaluation of thermokinetics methodology, parameters, and coke characterization of co-pyrolysis of bituminous coal with herbaceous and agricultural biomass

In this paper, conventional thermogravimetric analysis and a new congruent–mass thermogravimetric analysis were used to study the reaction mechanism of the co-pyrolysis process of coal and biomass in the thermogravimetric analyzer, the effects of heating rate and carrier gas flow rate on co-pyrolysis were investigated, and kinetic analysis was conducted for the major pyrolysis stages to explore whether there was a synergistic effect in the co-pyrolysis process. The surface morphology of pyrolytic coke was evaluated by the fractal dimension method. The results show that congruent–mass thermogravimetric analysis can compare the interactions in the co-pyrolysis process more intuitively and reduce the influence of initial mass on the determination of interaction relationship. Synergistic effect appears in co-pyrolysis of coal and biomass. With the increase of heating rate, the thermogravimetric hysteresis appeared and the thermogravimetric curve gradually moved to the high temperature region. With the increase of carrier gas flow rate, the synergistic effect weakens. The kinetics of different reaction stages was analyzed by Coats–Redfern method; the results show that the activation energy required in the main co-pyrolysis stage of the mixture is lower than that in the pyrolysis stage alone. The micromorphology shows that biomass coke has a more developed pore structure than coal, and the box dimension indicates that co-pyrolysis increases the surface irregularity of coke. It is of great significance to judge the interaction mechanism of two or even multiple mixed samples in the process of co-pyrolysis.

Study on Mechanism of Glass Molding Process for Fingerprint Lock Glass Plates

Curved glass is widely used in 3C industry, and the market demand is increasing gradually. Glass molding process (GMP) is a high-precision, high-efficiency 3D glass touch panel processing technology. In this study, the processing parameters of fingerprint lock glass panels were deeply analyzed. This paper first introduces the molding process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Firstly, it introduces the forming process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Secondly, the simulation model of a fingerprint lock glass plate was simulated by MSC. Marc software. The stress relaxation model and structure relaxation model are used in the model, and the heat transfer characteristics of glass mold are combined to accurately predict the forming process of glass components. The effects of molding temperature, heating rate, holding time, molding pressure, cooling rate and other process parameters on product quality characteristics (residual stress and shape deviation) were analyzed through simulation experiments. The results show that, in a certain range, the residual stress is inversely proportional to the bending temperature and heating rate, and is directly proportional to the cooling rate, while the shape deviation decreases with the increase of temperature and heating rate. When the cooling rate decreases, the shape deviation first decreases and then increases. Furthermore, a verification experiment is designed to verify the reliability of the simulation results by measuring and calculating the surface roughness of the formed products.

Nonisothermal dissolution kinetics on Mg17Al12 intermetallic in Mg-Al alloys

In this work, nonisothermal dissolution of intermetallic Mg17Al12 in Mg-Al alloy has been firstly studied via Differential Scanning Calorimetry-DSC, X-Ray Diffraction-XRD and Scanning Electron Microscope-SEM as well as CALPHAD_based dissolution models and molecular dynamics simulation. The size and volume fraction of Mg17Al12 phase could be predicted via the present kinetic dissolution model and agree well with experimental results. Also, the data-driven screening calculation shows that there is a range of temperature for significantly dissolving Mg17Al12 phase, which could be increased with the increase of heating rate. The evolution of structural order for Mg17Al12 phase has also been performed via molecular dynamics simulation with LAMMPS. The simulated results indicate that the structural order of Mg17Al12 phase during heating is mainly affected by the Al-contained atomic pairs (Al-Al and Al-Mg), suggested that Mg atoms are thermodynamically and kinetically more active than Al atoms in Mg17Al12 phase during heating, which has also been approved via the calculated atomic mobility of Mg and Al atoms in Mg17Al12 phase in this work. Therefore, the atomic mobility of Mg atoms is mainly attributed to the interdiffusion coefficient of Mg17Al12 phase which determines the dissolution of Mg17Al12 phase during heating. The fundamental principle in this work could be used for other intermetallics and offers the greatly valuable information for optimizing the thermal processing in application of metal structural materials.

Thermal Analysis and Kinetic Study of Indian Almond Leaf by Model-Free Methods

ABSTRACT Thermogravimetric analysis of Indian almond leaf was carried out at four different heating rates such as 5°C/min, 10°C/min, 15°C/min and 20°C/min. The kinetic study was performed using model free methods and the kinetic parameters were calculated by Kissinger, Friedman, KAS and FWO models. Thermogravimetric analysis resulted that the Indian almond leaf showed four stages of decomposition. Most of the mass loss occurred at stage II (188–460°C) owing to the simultaneous decomposition of cellulose, hemicellulose, and lignin. The shifting of pyrolysis curve occurred with increase of heating rate due to the limitation of heat transfer. The rate of mass loss decreased while increasing the heating rate due to the presence of more inert content i.e. ash and less volatile matters. The mean activation energy calculated by Kissinger, Friedman, KAS, and FWO showed as 52.67, 45.53, 73.73, and 72.28 kJ/mole. The mean activation energy of different leaves reported by earlier researcher was compared with the activation energy of Indian almond leaf and concluded that it stick to the range of activation energy of reported leaves.

Representation by two climate models of the dynamical and diabatic processes involved in the development of an explosively deepening cyclone during NAWDEX

Abstract. The dynamical and microphysical properties of a well-observed cyclone from the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX), called the Stalactite cyclone and corresponding to intensive observation period 6, is examined using two atmospheric components (ARPEGE-Climat 6.3 and LMDZ6A) of the global climate models CNRM-CM6-1 and IPSL-CM6A, respectively. The hindcasts are performed in “weather forecast mode”, run at approximately 150–200 km (low resolution, LR) and approximately 50 km (high resolution, HR) grid spacings, and initialised during the initiation stage of the cyclone. Cyclogenesis results from the merging of two relative vorticity maxima at low levels: one associated with a diabatic Rossby vortex (DRV) and the other initiated by baroclinic interaction with a pre-existing upper-level potential vorticity (PV) cut-off. All hindcasts produce (to some extent) a DRV. However, the second vorticity maximum is almost absent in LR hindcasts because of an underestimated upper-level PV cut-off. The evolution of the cyclone is examined via the quasi-geostrophic ω equation which separates the diabatic heating component from the dynamical one. In contrast to some previous studies, there is no change in the relative importance of diabatic heating with increased resolution. The analysis shows that LMDZ6A produces stronger diabatic heating compared to ARPEGE-Climat 6.3. Hindcasts initialised during the mature stage of the cyclone are compared with airborne remote-sensing measurements. There is an underestimation of the ice water content in the model compared to the one retrieved from radar-lidar measurements. Consistent with the increased heating rate in LMDZ6A compared to ARPEGE-Climat 6.3, the sum of liquid and ice water contents is higher in LMDZ6A than ARPEGE-Climat 6.3 and, in that sense, LMDZ6A is closer to the observations. However, LMDZ6A strongly overestimates the fraction of super-cooled liquid compared to the observations by a factor of approximately 50.

Pyrolysis characteristics and non-isothermal kinetics of waste wood biomass

The evaluation of thermochemical characteristics and the development of kinetic model for pyrolysis of waste biomass are more challenging. In this study, the mass losses, intermediates evolved and products formed during pyrolysis of waste wood biomass were determined by coupling DSC/TGA-DTG/GC-MS/FTIR to improve the understanding of conversion processes and decomposition characteristics. The improved non-isothermal kinetics method was proposed by introducing the function of mechanisms, the activation energies and pre-exponential factors were estimated iteratively by regression to enhance modeling accuracy. The results indicated the gases of CO, CO2, CH4, H2 and the liquids of N-containing organics, esters, ketons and carboxylic acids were the most dominated products evolved. The pyrolysis of waste wood biomass could be divided into three phases, and with the increase of heating rates, the caloric requirement for pyrolysis was greatly increased. The random nucleation and one-dimensional diffusion predicted accurately the main (second) and third phases in the pyrolysis of waste wood biomass and waste camphor presented lower activation energies than waste bamboo.

Effect of heating rate on gasification and phosphorus recovery for palm oil mill effluent in supercritical water

This study investigated the effects of the heating rate on the simultaneous production of gas and inorganic phosphorus (IP) from palm oil mill effluent in supercritical water (600 °C, 25 MPa). The heating rate was controlled by modulating the preheater lengths (1, 2, and 4 m) and flow rates (2 and 3 g/min). Faster heating rates were obtained using shorter-length preheaters, even at identical flow rates. Although the increased heating rate resulted in a higher carbon gasification efficiency and lower hydrogen content, it also reduced the amount of precipitated IP. As the effect of flow rate, which determined the residence time in the reactor, was much smaller than that of the heating rate, it can be concluded that the primary reactions of this process are completed in the preheater. This finding can help to guide the optimization of the POME recycling process.

Thermal and mechanical properties of polyethylene-starch based film incorporated with crude palm oil

The present study reports the changes in thermal degradation, thermal properties, and mechanical performance of polyethylene (PE) - thermoplastic starch (TPS) based film incorporated with crude palm oil (CPO) as a plasticizer. The films were prepared using the melt-blending and hot-press technique. Then, it was characterized using a Thermogravimetric analyzer, Differential Scanning Calorimetry, and Universal Testing machine to determine the film’s thermal degradation, thermal properties, and mechanical properties. TPS in PE film had reduced the thermal stability; however, CPO gives small changes to it. The amorphous phase of TPS reduced PE film’s crystallinity. Besides, CPO provided a lubricating effect and improved the crystallinity of PE/TPS film. Unfortunately, the tensile strength and elongation at break keep decreased with an increase of CPO content. The thermal decomposition and kinetic analysis using a thermogravimetric analyzer on one film (PE/TPS/CPO) at three different heating rates (7.5, 10.0, and 12.5 °C/min) were investigated. Friedman isoconversional model-free method was used to calculate the activation energy of the film. The thermal decomposition of materials in the film increased with the increasing heating rate, and the average computed activation energy obtained was 364.68 kj/mol.