Thermogravimetric Tests Research Articles

Influence of the carbonization atmosphere on the development of highly microporous adsorbents tailored to CO2 capture

Two microporous activated carbons (ACs) tailored to CO2 capture were developed from Prosopis ruscifolia sawdust. The ACs were obtained through a two-stage process. The first consisted in the carbonization of the precursor, while the second involved chemical activation employing KOH solution as activating agent. The influence of the atmosphere involved in the carbonization stage (N2 flow at 773 K or air flow at 573 K) on the chemical and textural-morphological characteristics of the resulting ACs and on their CO2 removal capacity was analyzed. The ACs presented similar properties with a predominance of microporous structures, BET surface areas slightly larger than 1000 m2 g−1, and micropore volumes of ∼0.43 cm3 g−1 on average. Both ACs also showed a predominance of surface acidic functionalities over basic ones. The adsorbed amounts of CO2 as determined from the isotherms were 5.6 and 5.3 cm3 g−1, for the ACs developed from the precursor carbonized under N2 and air flow, respectively. From thermogravimetric tests to assess adsorption kinetics, values of the CO2 removal (101.325 kPa and 303 K) reached at equilibrium conditions were 1.15 and 1.04 mmol g−1, respectively. Present results demonstrated that the carbonization atmosphere did not have a pronounced effect on chemical and textural characteristics of the resulting ACs and, consequently, on their CO2 adsorption capacity. Accordingly, the use of air instead of N2 in the carbonization stage of the activation process may represent an interesting alternative because of the lower operating temperature involved, leading to reduce energy consumption and operating costs without sensibly affecting ACs performance.

The Ratio Optimization and Strength Mechanism of Composite Cementitious Material with Low-Quality Fly Ash.

To resolve the limited large-scale methods of disposal of low calcium fly ash with poor activity, based on the double excitation principle, clinker and desulfurized gypsum are used as alkali/salt activators to activate fly ash and slag, avoiding the inconvenience of strong alkali activating fly ash in industry. Firstly, the strength test of a filling body with multiple ratio composite cementing material is carried out, and the weight coefficient of each material to strength is analyzed by grey correlation degree. The composition of the hydration products, microstructure, and pore structure of the filling body was analyzed by X-ray diffractometer, scanning electron microscope, thermogravimetric test, and mercury compression test. The strength mechanism of the cemented body was confirmed. The results show that cemented backfill prepared by composite cementitious material, which contained high content and low-quality fly ash, can meet the strength requirements of subsequent backfill in a mine. The degree of composite cementitious material influence on 7 d strength is slag > desulfurized gypsum > fly ash > clinker; the degree of influence on 28 d strength is: fly ash > slag > desulfurized gypsum > clinker. The main hydration products of the composite cementable material with high content low-quality fly ash are C–S–H gel and ettringite, and the unreacted fly ash particles can still be seen at 28 d. As the curing age grows, the difference in the number of hydration products under different proportioning conditions has a weaker effect on the strength, while the influence of raw materials and product morphology on the pore structure determines the development trend of the strength. Therefore, the threshold pore size can be used to characterize the strength advantages and disadvantages reasonably.

Ammonium Polyphosphate Intercalated Yttrium-Doped Layered Double Hydroxides to Enhance the Thermal Stability and Flame Retardancy of Poly(Lactic Acid)

The flammability of the biodegradable plastic PLA limits its application in industrial fields with high flame-retardant requirements. This paper provides a novel strategy for constructing refractory and thermostable PLA composites using layered double hydroxides (LDHs) chemically modified with ammonium polyphosphate (APP). XRD, FT-IR, SEM-EDS, and TEM confirm that the goal of LDHs has been successfully prepared. The thermal stability and combustion behavior of PLA composites were evaluated by the thermogravimetric analysis (TGA) and cone calorimetry tests (CCT). The crystallization behavior and tensile performances were also examined. The results showed that the incorporation of 15 wt% MgAlY-APP-LDHs practically makes the PLA composites reach the UL-94 V-0 grade. There were 43% and 20% reduction in the PHRR and THR of PLA/15APP-LDHs respectively due to the catalytic effect of Y elements and barrier effects of LDHs, which was a major performance against fire hazards. Furthermore, the increase in crystallinity and the decrease in mechanical strength of PLA composites are attributed to the nucleation of LDHs. In short, this research introduces the production of multifunctional PLA composites through APP intercalation of LDHs, which are deemed as prospective candidates for the next generation of sustainable plastics products.

Comparison of Pyrolysis and Combustion Processes of Vinyl Floor Panels Using Thermogravimetric Analysis (TG-FTIR) in Terms of the Circular Economy

The article analyzes the thermal degradation in the inert and oxidative atmosphere of waste vinyl panels, the main component of which is PVC. Both pyrolysis and incineration of plastic waste are difficult, complex and multifaceted processes due to several physical and chemical phenomena occurring during their performance. The coupled TG-MS (thermogravimetry-mass spectrometry) analysis combined with the Fourier transform infrared spectrometry (TG-FTIR) analysis was used to identify the decomposition mechanisms of waste vinyl panels. Thermogravimetric tests were carried out for two heating rates of 5 and 20 K/min in the temperature range of 40–1000 °C, mass losses were determined, and products resulting from thermal degradation were identified. It was found that the individual components decompose at different temperatures depending on the heating rate and the choice of an inert or oxidative atmosphere. Vinyl floor panels were treated in terms of secondary raw material, which, in the light of the circular economy, may constitute a potential energy or chemical resource.

Design and application of molecularly imprinted polymers for adsorption and environmental assessment of anti-inflammatory drugs in wastewater samples.

In this study, a series of molecularly imprinted polymers (MIPs) have been synthesized using separately diclofenac, naproxen, and ibuprofen as templates with three different polymerization approaches. Two functional monomers, methacrylic acid (MAA) and 2-vinylpyridine (2-VP), were tested and ethylene glycol dimethacrylate (EGDMA) was used as crosslinker; also, template-free polymers (NIPs) were synthesized. It was found that the MIP with the highest retention percentage for diclofenac was the one prepared by the emulsion approach and with MAA (98.3%); for naproxen, the one prepared by the bulk polymerization with MAA (99%); and for ibuprofen, the one synthesized by bulk with 2-VP (97.7%). These three MIPs were characterized by scanning electron microscopy, thermogravimetric test, Fourier transform infrared, specific area measurements, and surface charge. It was found that the emulsion method allowed particle size control, while the bulk method gave heterogeneous particles. The three evaluated MIPs exhibited thermal stability up to 300 °C, and it was observed that 2-VP confers greater stability to the material. From the BET analysis, it was demonstrated that the MIPs and NIPs evaluated are mesoporous materials with a pore size between 10 and 20 nm. In addition, the monomer influenced the surface charge of the material, since the MAA conferred an acidic point of zero charge (PZC), while the 2-VP conferred a PZC of basic character. Through adsorption isotherms, it was determined that there is a higher adsorption capacity of the MIPs at acidic pH following a pseudo-second-order kinetic model. Finally, the MIPs were used to determine the non-steroidal anti-inflammatory drugs (NSAIDs) understudy in San Luis Potosí, México, wastewater, finding concentrations of 0.642, 0.985, and 0.403 mg L-1 for DCF, NPX, and IBP, respectively.

Application of kinetic pyrolysis models to the analysis of flax chipboards under fire

This study presents a three-dimensional finite element model to describe the thermomechanical behaviour of flax chipboards under fire conditions. The model is based on kinetic models considering the thermal degradation during the pyrolysis phase and the evolution of the physico-mechanical properties as functions of temperature. The numerical model is integrated into Abaqus via user subroutines (Umat and Umatht) and applied to the analysis of the fire behaviour of panels made of flax chipboards. Thermogravimetric tests are performed on flax particles to serve for the identification of the kinetic parameters of the pyrolysis models. Once these kinetic parameters are determined, they are integrated into a complete numerical model to simulate the behaviour under fire of flax chipboards on small and large scales. The obtained trends in the predicted values indicate good agreements when compared to the measured values. The simulations show that the numerical model is capable of accurately modelling the thermomechanical transfers taking place within the material during exposure to fire.

Fire structural performance of thermo-mechanically compressed spruce timber by means experiments and a three-step multi-reactions pyrolysis 3D-finite element modelling

This paper presents experimental and numerical investigations to access the relative fire structural resistance of thermo-mechanically compressed (or densified) spruce wood. First of all, thermal characterization, including thermal conductivity and specific heat, has been undertaken on both compressed and uncompressed spruce wood. The thermal degradation of both compressed and uncompressed wood has been analysed by means thermogravimetric tests using different heating rates. Both compressed and uncompressed spruce samples of dimensions of 100 mm × 100 mm × 19 mm have been subjected to fire in a cone calorimeter under 20 kW/m2 and 75 kW/m2. Finally, a predictive finite element model based on three-step multi-reactions of pyrolysis is proposed for the thermal transfer and degradation analyses of timber material. The simulated thermal profiles, the mass loss as well as the charring depths were compared to the experimentally recorded results showing a fairly good agreement.

Mechanical and visco elastic analysis of Sal tree gum incorporated epoxy bio composite

The impact of Sal tree (Shorea Robusta) gum powder on the mechanical, visco elastic, and thermal characteristics of epoxy resin was studied. Using the hand layup technique, composite specimens were created by adding bio filler (Sal tree gum powder) at various volume percentages in epoxy resin. Experiments were carried out to assess the epoxy composite's mechanical, thermogravimetric, and viscoelastic characteristics. Results showed that the bio filler had a substantial impact on the mechanical, thermal, and dynamic mechanical characteristics of the samples. Better mechanical and dynamic mechanical properties were obtained at 16% v/v of Sal Tree gum powder. The inclusion of the bio filler, on the other hand, had no appreciable impact on the flexural and tensile strengths of the composite. The morphological features of a tensile cracked specimen were investigated using scanning electron microscopy (SEM) images of the specimen. The homogeneity of the bio composite was also examined by using the Cole Cole plot. According to the findings, the composite specimens containing the bio filler showed uniform features. It was observed that the composite specimens incorporated with the bio filler exhibited homogeneous characteristics. The thermal stability of the composite was investigated using thermogravimetric (TGA) test, and it was found that the inclusion of filler enhanced the thermal stability of the composite, with the composite remaining stable up to 431 °C after the addition of filler. The results of dynamic mechanical analysis (DMA) tests showed that the inclusion of bio filler resulted in an increase in storage modulus, suggesting that the composite is capable of greater energy absorption within the elastic limit. The glass transition temperature was calculated to be 110 °C.

The Potential of Al2O3\u2013ZrO2-Based Composites, Formed via CSC Method, in Linear Infrastructure Applications Based on Their Mechanical, Thermal and Environmental performance

Ceramic-ceramic composites have been prepared using the centrifugal slip casting method (CSC). The method has so far been mainly utilized in making ceramic-metal composites. Al2O3–ZrO2 composites have been obtained with different shares of ZrO2, i.e., 15, 50 and 75 vol pct, respectively. Prior to sintering the composite samples, the rheological properties of the casting slips were investigated and thermogravimetric tests were performed. Upon sintering, all three series of the ceramic composites showed a density close to 100 pct and no microcracks or delamination. Phase, microstructural and mechanical investigations were carried out to determine what effect the share of ceramics has on the composites produced. An increase in the share of ZrO2 in the Al2O3–ZrO2 composite leads to a reduction in the growth of Al2O3 grains and a decrease in the average hardness. Cross-sectional hardness testing of the composites showed no evident gradient in any of the samples. Life cycle analysis (LCA) results indicate that the further optimization of the composite formation process, including up-scaling, allows to obtain Al2O3–ZrO2-based pipes possessing more favorable environmental characteristics compared with materials conventionally used for linear infrastructure, which is important in light of the global transformation toward sustainable construction and the circular economy.Graphical abstract

A novel thermally-activated delayed fluorescent probe based on hydroxyl as identify group for detection of iron ions

A thermally-activated delayed fluorescent (TADF) probe TPA-SOOH was designed and synthesized for the detection of iron ions, which based on triphenylamine sulfoxide as luminescence nucleus and the hydroxyl as identification group. Low temperature phosphorescence spectroscopy indicated that the probe possesses a small singlet and triplet splitting (ΔEST) of 0.16 eV, which ensured the reverse intersystem crossing (RISC) for TADF process. Thermogravimetric test results demonstrated that the probe has good thermal stability with glass transition temperature above 70 °C. Fluorescence testing revealed that the probe is obvious characteristics of iron ion response and the limit of detection is 13 nM obtained by titration experiment. Moreover, the probe had good fluorescence stability in different acid-base environments, which benefited for its practical application. This study firstly proved that TADF material can be used as fluorescence probe for ion detection, which would further expand the material system of fluorescent probe.

Thermal Analysis of a Metal-Organic Framework ZnxCo1-X-ZIF-8 for Recent Applications.

Zeolitic imidazolate frameworks (ZIFs) are interesting materials for use in several aspects: energy storage material, gas sensing, and photocatalysis. The thermal stability and pyrolysis process are crucial in determining the active phase of the material. A deep understanding of the pyrolysis mechanism is in demand. Therefore, the thermodynamics and combustion process with different heating rates was examined, and the kinetic parameters were computed employing thermogravimetric tests. Based on the TG analysis of combustion, pyrolysis moves to the high-temperature region with an increase in heating rate. The decomposition process can be separated into the dehydration (300–503 K) and the pyrolysis reaction (703–1100 K). Three points of the decomposition process are performed by dynamical analysis owing to shifts of slopes, but the combustion process has only one stage. The Zeolitic imidazolate framework’s structure properties were examined using TDDFT-DFT/DMOl3 simulation techniques. Dynamical parameters, for instance, the possible mechanism, the pre-exponential factor, and the apparent activation energy are obtained through comparison using the Kissinger formula. The thermodynamics analysis of the Zn1-xCox-ZIF-8 materials is an effective way to explore the temperature influence on the process of pyrolysis, which can benefit several environment purifications, photocatalyst, and recent applications.

Towards the use of acrylic acid graft-copolymerized plant biofiber in sustainable fortified composites: Manufacturing and characterization

Abstract In this study, the impact of particle form of the Cannabis indica plant biofibers and the fiber’s surface tailoring on the physical, thermal, dielectric, and mechanical properties of unsaturated polyester composite specimens manufactured utilizing nonconventional materials were investigated. The mechanical properties such as compressive, flexural, and tensile strengths of the composite specimens were noticed to increase after functionalization of biofiber with acrylic acid and maximum enhancement was found at 20% of biofiber sacking. The physical characterization was concentrated on the assurance of the dielectric constant, dielectric strength, dielectric loss, moisture absorption, chemical resistance, percentage of swelling, limiting oxygen index, and biodegradation of polymer composites under red soil. An increase in dielectric strength from 28 to 29 kV, limiting oxygen index values from 19% to 23%, and moisture/water absorption behavior was noted for resulted bio-composites after surface tailoring of biofiber. To assess the deterioration of the polymeric materials with the temperature, differential scanning calorimetric and the thermogravimetric tests were carried out and enhancement in thermal stability was noted after fortification of polyester composites with functionalized biofiber.

A predictive model for the industrial air-impingement drying of resin impregnated paper

Industrial drying lines of resin-impregnated paper are formed by contiguous furnaces where hot air jets impinge on the surface of the moving paper sheet. The number of production parameters that conditions the process is very high, making the final drying prediction, and the optimal adjustment of the production parameters, very complex tasks. A novel numerical tool for the fast prediction of this industrial drying is presented. The model, obtained from local mass and energy equations for the paper sheet, and fed with results from three-dimensional computational fluid dynamic simulations and thermo-gravimetric tests, determines the evolution of the paper weight along the line for any given combination of production parameters: paper velocity, furnaces air temperatures and mass flows, among others. The model is validated in an industrial line with 11 furnaces, 2 impregnation stages, and more than 150 adjustable operational input parameters, leading to relative errors in the predicted paper temperature evolution and final paper weight of less than 7% and 1%, respectively. Likewise, the model coupling with an optimization tool is also presented to show its capabilities on selecting the best production parameters for prescribed conditions, making the model a useful tool in the framework of the increasingly relevant role of mathematical models in industry.

Superhydrophilic polyethersulfone (PES) membranes with high scale inhibition properties obtained through bionic mineralization and RTIPS

Reverse thermally induced separation (RTIPS) was used to obtain a separation membrane with a better internal structure for a higher water flux and a surface that could easily form a hydration layer. In comparison to the traditional modification method, this work focused on the aspect that the internal structure obtained by changing the membrane-making method provided easier adhesion conditions for the dopamine/TiO2 hybrid nanoparticles (DA/TiO2 HNPs) obtained by biomimetic mineralization. It provided a basis for exploring the variation in adhesion with the water bath temperature and the amount of titanium added through the study of turbidity point, SEM images, water contact angle, thermogravimetric test, EDX, AFM, XPS, FTIR and other test results. The SEM images proved that the membrane obtained through the RTIPS method had a porous surface and spongy internal structure, furthermore, additional polymers were adsorbed. Use of EDX demonstrated that biomimetic mineralization prevented the production of agglomerated titanium dioxide. XPS and FTIR spectra confirmed the introduction and immobilization of HNP aggregation. Moreover, a decrease in the surface roughness and water contact angle further suggested an improvement in the hydrophilicity of the modified membrane. The introduction of HNP at a higher water bath temperature helped increase the water flux up to ten times, moreover, the oil-water separation efficiency could still reach over 99.50%. Lastly, a cycle test of the modified membrane under the optimal conditions helped confirm that the membrane forming conditions at this time could provide a better environment for the formation of the hydrophilic layer, which was conducive to the recycling of the separation membrane. In summary, more fixed more hydrophilic particles could be obtained through the RTIPS method based on biomimetic mineralization to prevent the accumulation of titanium dioxide, thus helping improve permeability and anti-fouling of the membrane.

The Oxidation of Copper in Air at Temperatures up to 100 °C

The aim of this study was to investigate the oxidation kinetics of copper at low temperatures (60 °C to 100 °C) in air by isothermal thermogravimetric analysis (TGA) and quartz crystal microbalance (QCM). The weight change in thermogravimetric tests showed periodic weight increase and decrease. In thermogravimetric tests the mass of the copper sample increased until the oxidation gradually slowed down and finally started to decrease due to cracking and spalling of the oxide formed on the surface. In QCM tests using electrodeposited copper film, the weight change was rapid at the beginning but slowed to a linear relationship after few minutes. Temperature and exposure time appeared to have a large effect on oxide film thickness and composition. With QCM, oxidation at 60–80 °C produced less than 40 nm films in 10 days. Oxidation at 90–100 °C produced 40 nm thick films in a day and over 100 nm films in a week. Although SEM-EDS analyses in TGA tests indicated that oxygen was adsorbed on the copper surface, neither XRD patterns nor Raman spectroscopy measurements showed any trace of Cu2O or CuO formation on the copper surface. Electrochemical reduction analysis of oxidized massive copper samples indicated that the oxide film is mostly Cu2O, and CuO develops only after several days at 90–100 °C.

Characterization of Thermal Bio-Insulation Materials Based on Oil Palm Wood: The Effect of Hybridization and Particle Size.

Oil palm wood is the primary biomass waste produced from plantations, comprising up to 70% of the volume of trunks. It has been used in non-structural materials, such as plywood, lumber, and particleboard. However, one aspect has not been disclosed, namely, its use in thermal insulation materials. In this study, we investigated the thermal conductivity and the mechanical and physical properties of bio-insulation materials based on oil palm wood. The effects of hybridization and particle size on the properties of the panels were also evaluated. Oil palm wood and ramie were applied as reinforcements, and tapioca starch was applied as a bio-binder. Panels were prepared using a hot press at a temperature of 150 °C and constant pressure of 9.8 MPa. Thermal conductivity, bending strength, water absorption, dimensional stability, and thermogravimetric tests were performed to evaluate the properties of the panels. The results show that hybridization and particle size significantly affected the properties of the panels. The density and thermal conductivity of the panels were in the ranges of 0.66–0.79 g/cm3 and 0.067–0.154 W/mK, respectively. The least thermal conductivity, i.e., 0.067 W/mK, was obtained for the hybrid panels with coarse particles at density 0.66 g/cm3. The lowest water absorption (54.75%) and thickness swelling (18.18%) were found in the hybrid panels with fine particles. The observed mechanical properties were a bending strength of 11.49–18.15 MPa and a modulus of elasticity of 1864–3093 MPa. Thermogravimetric analysis showed that hybrid panels had better thermal stability than pure panels. Overall, the hybrid panels manufactured with a coarse particle size exhibited better thermal resistance and mechanical properties than did other panels. Our results show that oil palm wood wastes are a promising candidate for thermal insulation materials.

Thermochemical liquefaction of wheat straw and its effectiveness as an extender for asphalt binders: Characterization of liquefied products and potential opportunities

Numerous attempts have been carried out to develop potential substitutes for petroleum asphalt binders from various biomass resources. This research aims to investigate the effectiveness of partially replacing asphalt binders with thermochemical liquefied products (LPs) of wheat straw. The LPs were obtained by acid-catalyzed liquefaction in organic solvents, based on which nine kinds of bio-asphalt binders distinguished by the type and content of LPs were prepared by mechanical stirring. To evaluate the physicochemical properties of the LPs, the Fourier transform infrared (FTIR) spectroscopy test, gel permeation chromatography (GPC) test, thermogravimetric (TG) test and rotational viscosity (RV) test were conducted. The potential advantages of bio-asphalt binders were explored by the RV test, dynamic shear rheometer (DSR) test, scanning electronic microscopy (SEM) test and FTIR test. The results demonstrate that LPs consist of 79%–88% bio-oils with low molecular weight and a small amount of solid residues. Compared with asphalt binders, more polar groups (e.g. hydroxyl, carbonyl and alcohol, etc.) with low boiling points are found in LPs, resulting in a lower volatilization and degradation temperature. There is a high chance for the fusion of LPs and asphalt binders to be physical integration. Further, the non-Newtonian flow behavior of asphalt binders is deepened by LPs. Nevertheless, better low-temperature cracking resistance and high-temperature performance are found from different types of bio-asphalt binders. It should be noted that the relationship between performances of bio-asphalt binders and the content of LPs needs more attention in further researches.

High-Temperature Dielectric and Microwave Absorption Property of Atmospheric Plasma Sprayed Al2O3-MoSi2-Cu Composite Coating

Al2O3-MoSi2 coating has excellent high-temperature stability. On this basis, Al2O3-MoSi2-Cu composite high-temperature absorbing coating was prepared by atmospheric plasma spraying method. The phase transition characteristics of Al2O3-MoSi2-Cu spraying feedstock under high temperatures were analyzed by thermogravimetric test, the phase analysis of coating was performed by an in situ XRD test at different temperatures, and the microstructure of the coating was characterized by SEM. The test results of high-temperature microwave absorption performance show that, in high-temperature air atmosphere, the Cu in the coating is gradually transformed into Cu2O by oxygen atom diffusion, and the microwave absorption performance of the coating gradually increases with the increase in temperature. The 1.7 mm-thick coating at 500 °C has the best absorbing performance with a reflection loss (RL) value of −17.96 dB and an effective absorbing bandwidth (RL < −10 dB) in X-band of 2.42 GHz. The prepared Al2O3-MoSi2-Cu composite high-temperature absorbing coating takes into account the dual advantages of high-temperature stability and high-temperature absorbing properties.

PHYSICAL, THERMAL AND TENSILE ANALYSIS OF SANSIVERIA ROXBURGHIANA LEAF FIBER

ABSTRACT In this research work, the fibers were extracted from the leaf of the Sansevieria roxburghiana plant through a mechanical decortication process. The morphological structure of the fiber was analyzed using a scanning electron microscope and optical microscope. The chemical composition and crystallinity of the fiber were analyzed using Fourier transforms infrared, and X-ray diffraction techniques. The physical and tensile properties of the fibers were measured and compared with the cotton, sisal, and other varieties of sansevieria fibers. The average length of the fiber was around 7.6 cm and the density of the fiber was found as 1.41 g/cc. The thermal properties of the fiber were analyzed using Thermogravimetric (TGA) analysis. TGA tests showed that the fiber is stable below 220◦C temperature. The crystallinity of the fiber was measured as 46.42%. It is understood that Sansevieria roxburghiana can be suitably considered to use as reinforcement in green composite materials and other technical textiles sectors.

Composite auto-ignition criterion for PMMA (Poly methyl methacrylate) exposed to linearly declining thermal radiation

This contribution experimentally studies auto-ignition of thermally thick PMMA (Poly methyl methacrylate) subjected to linearly declining heat flux (HF) radiated from a cone heater. Thermogravimetric tests (TGA) were conducted to derive the kinetics of PMMA by model fitting method. A numerical model dealing with heat transfer and pyrolysis is utilized to simulate the experimental measurements. Results show that auto- and no-ignition regions are separated by a critical decreasing rate of HF which is quantitively determined by numerical results. Measured surface temperatures are compared with the analytically and numerically estimated ones, and it is found both ignition time and critical decreasing rate are sensitive to critical temperature. These senilities are also confirmed by numerical model through parametric study. In no-ignition region near the critical condition, the maximum mass flux is higher than the measured critical value, 4.26 g/m2s, indicating critical mass flux is not a credible ignition criterion. Measured critical temperature increases with higher initial HF and yields an average value of 641 K. A composite auto-ignition criterion combining both critical mass flux and critical temperature is found valid in estimating ignition time. Meanwhile, the different affecting mechanisms of decreasing HF on auto-ignition between this work and literature is reasonably interpreted.