Acetylene-oxygen Flame Research Articles

Reinforced compressive and ablative properties of phenolic aerogel by in-situ polycarbosilane-derived ceramic

Lightweight ablative materials owing to their low density, high efficiency heat insulation and excellent designability, which are considered as the most promising candidate materials in the field of aerospace ablative thermal protection. In this work, a polycarbosilane (PCS) in-situ reinforced carbon felt/phenolic (PR/Cf) aerogel composite is reported. The surface of aerogel and carbon fiber was coated with PCS protective layer by sol gel method and secondary vacuum impregnation process. The aerogel composite material possesses low density (0.264–0.307 g/cm3), hydrophobic, low thermal conductivity (0.121–0.178 W/(m·K)) and significant high compressive strength (12.89 MPa). When the oxygen acetylene flame with high heat flow density ablates for 20 s, it shows high efficiency in heat protection and insulation, and the linear ablation rate is as low as 0.089 mm/s. The PL/PR/Cf aerogel composite shows competitive and broad application prospects in the field of ablation heat protection in the future.

A novel Hf0.75Zr0.25N solid solution coating with high mechanical strength: Ablation protection application above 2200°C

Obtaining coatings with excellent ablation resistance is a longstanding challenge for the ablation protection of carbon/carbon (C/C) composites. In this work, a single phase Hf0.75Zr0.25N solid solution ultra-high temperature ceramic (UHTC) coating was proposed, and prepared on the surface of C/C composites by chemical vapor deposition (CVD) for the first time. The results revealed that the hardness and Young's modulus of Hf0.75Zr0.25N coating are higher than those of HfN and ZrN coatings, reaching 33.35 GPa and 316.42 GPa, respectively. After ablation for 180 s under oxygen acetylene flame with a temperature exceeding 2200 °C, the Hf0.75Zr0.25N coating retained its structural integrity and exhibited lower ablation (Rm: 0.26 mg/s; Rh: 0.32 μm/s). This is mainly attributed to the formation of the dense Hf-Zr-O oxide scale promoted by the oxidation sintering reaction during ablation. The above results indicate the nitride solid solution UHTC has great potential as ablation resistance coating at ultra-high temperatures.

Research on the technology of flame spraying aluminum coating for composite material

Aluminum coating was prepared on composite material surface by using oxygen-acetylene flame spraying technology. The H01-103H sealants were used to seal the thermal sprayed aluminum coatings. The characteristics of the aluminum coatings with and without H01-103H sealant, including surface morphologies, phase composition, and bonding strength, were investigated by means of SEM, EDS, and mechanical testing machine. Thermal shock experiment and low temperature cooling test were also used to examine the thermal shock resistance and frost resistance of the Al coatings. Electrical conductivity and electromagnetic shielding properties were then tested according to four-probe measurement principle and GJB 5239-2004, respectively. The results showed that the bond strength was 7.36 MPa and the surface porosity was about 5.21% for Al coating without H01-103H sealant, in addition, the H01-103H sealants could fill into the pores, reducing the porosity and increasing the bond strength of the coating. Furthermore, the main component of the coating was Al, the oxygen content was only 1.43%. Flame sprayed aluminum coating, with surface electrical resistance 0.89 mΩ and 5–18 GHz electromagnetic shielding effectiveness above 35 dB, was an ideal candidate for electromagnetic shielding utilization. The Al coating remained intact, compact, no cracks, peeling, layering under 50–200°C and −30°C, which showed good thermal shock resistance and frost resistance.

Enhanced ablative resistance of C/C composites with densified ZrB2-based ceramics by incorporation of Mo as interface layer

ZrB2-ZrC-SiC-Mo-C/C (ZZS-Mo-C/C) composites with dense composite ceramic coating and excellent interfacial bonding are synthesised using reaction spark plasma sintering (RSPS). Furthermore, the densification process, interfacial bonding, ablative properties and underlying mechanism of ZZS-Mo-C/C composites are investigated. Before and after ablation, the composite exhibits excellent interfacial bonding, indicating that the presence of Mo-foil transition layer enables an optimal connection between ZZS and C/C. Additionally, SEM analysis reveals that the ZZS ceramics have a dense structure, thereby preventing oxygen from diffusing further into the matrix. And the ablation results indicate that ZZS-Mo-C/C exhibits superior oxidation resistance when exposed to an oxygen-acetylene flame.

Influence of Substrate Surface Roughness on Synthesized Diamond Films by Flame Combustion on Ti Substrate for Dental Implants

The flame combustion method enables the synthesis of diamonds via acetylene-oxygen gas flame combustion in ambient air, and this method has various advantages over other methods. However, most diamond films synthesized by this method delaminate because of thermal stress during cooling. Titanium (Ti) has recently been utilized as a dental implant in the dental industry. In this study, to improve the strength, wear resistance, and biocompatibility of dental implant surfaces, diamond films were synthesized on a Ti substrate, a dental implant material, by the flame combustion method. Moreover, to obtain high-quality diamond films and achieve good adhesion on the Ti substrate, as a pretreatment of the substrate to prevent delamination, scratch processing, in which a substrate is ground with emery paper in one direction, was performed to roughen the surface. The surface roughness of the Ti substrates was varied by scratching with emery paper of #180, #400, and #1500 grain sizes. According to these results, diamond films were synthesized on the Ti substrate surface by flame combustion. The surface morphology of the synthesized films could be altered by varying the scratching process using emery paper. Delamination of the synthesized films during the scratching process with emery paper #180 (Case A) and #400 (Case B) grain size was completely prevented. However, delamination occurred during the scratching process with a grain size of emery paper #1500 (Case C). To investigate the reason for this result, the surface roughness of the pretreated Ti substrate was observed, and it affected the surface roughness of pretreated Ti substrate affected the surface morphology and delamination of the synthesized diamond films.

Оценка разрушения газовых баллонов от действия пламени горизонтального факела при расчете пожарного риска

The paper considers potential hazard of block placement of the cylinders with hydrogen and acetylene at the open technological site. The piping of the cylinders of the unit and shut-off and reducing valves are not considered. Analysis of the possibility of cylinders destruction in the block from the action of a horizontal torch during a jet outflow of gas from an emergency cylinder is presented. At the design stage, the prerequisites are considered for excluding from the fire risk calculation the scenario associated with the cascaded destruction of neighboring gas cylinders from the action of a horizontal torch. In the calculation of fire risk, the action of a horizontal torch on the adjacent cylinders leads to their destruction along the entire length of the burning torch. The main parameters of the jet outflow of hydrogen and acetylene from the holes of various diameters in the cylinder body are calculated. Graphical dependences of the maximum value of the thermal radiation of horizontal and vertical torches during the combustion of hydrogen and acetylene at different distances from the source were obtained by a numerical method. Based on the video material of the fire in the warehouse of acetylene cylinders, a qualitative assessment of the duration of the onset of cascaded destruction of cylinders in blocks is presented. Various methods of testing and fire effects on gas cylinders are analyzed to identify the minimum duration before the hull depressurization. The factors that can cause damage to the acetylene cylinder body without destruction are presented. The parameters of the acetylene-oxygen flame used for cutting metals of various thicknesses are evaluated and compared with the flare outflow from the cylinder. The minimum duration of flame exposure to the cylinder body, for through-burning, is substantiated, depending on the design and the stored gas. Additional ways of protecting gas cylinders in the block from possible exposure to the flame of a horizontally flowing gas jet are proposed.

Improving the technological process of increas-ing the durability of the working tool of hydrau-lic hammers by detonation spraying

The development of modern technology places increasing demands on the performance of the hydraulic hammer parts. In a complex of problems of increasing their reliability and durability the question of wear resistance occupies a special place. Insufficient wear resistance limits the productivity of hydraulic hammers and their service life, increases the cost of repair and purchase of spare parts. Goal. The purpose of this work is to scientifically substantiate and experimentally confirm the effectiveness of strengthening the critical parts of the hydraulic hammer by detonation spraying. Methodology. Detonation spraying with hard alloy powder VK 25 (80 %) and the binder material PT-NA-01 (Ni 91 %, Al 9%) was performed on a cleaned surface without pre-treatment. VK 25 powder is a tungsten-cobalt carbide (WC-Co) containing up to 25% cobalt, and is used for work in conditions of fretting corrosion, abrasive wear at normal and elevated (up to 650 ° C) temperatures. A granular powder of 20 – 100 μm was used, which was melted in an oxygen-acetylene flame and gas flow and was transferred to the surface of the part. The thickness of the sprayed layer was 0.1 mm. The surface roughness of the parts before spraying was Ra 0.35–2.5. As a result of spraying, the roughness of the working surfaces of the parts increased to the values of Ra 4.8–5.4. Results. The composition of the coating based on tungsten carbide was chosen to strengthen the surface of the investigated parts by detonation spraying. Detonation spraying modes were selected. The conditions for hardening treatment were determined. The nature of damage to parts after detonation spraying was established. Originality To solve the problem of improving the performance of the working tool of hydraulic hammers, the use of the detonation method of coating was proposed. Practical value. The test results of the details strengthened by detonation spraying showed that the increase of wear resistance by 1,8 times in comparison with an initial variant was reached.

Influence of flame straightening on the properties of welded joints made of X2CrNi22-2 duplex steel

Abstract The study investigates the optimal conditions associated with flame straightening of welded joints in duplex steel grade X2CrNi22-2. The research aimed to assess the influence of heat, applied during flame straightening of welded structures in X2CrNi22-2 grade steel, on the properties of the welded joints. Based on the macroscopic, microscopic, and strength tests conducted on welding joints in X2CrNiN22-2-grade duplex steel that have been subjected to flame straightening, it was ascertained that post-welding flame straightening of this grade of steel, at a treatment temperature of 730°C, should not take place for >1 min. The temperature of 730°C has been chosen as a reference because of the assumption that the welded joints are heated to the temperature of 700–730°C during straightening with an acetylene-oxygen flame. The paper scrutinizes the questions of (i) what changes occur in the welded joints as a result of flame straightening carried out in this temperature range and (ii) what impact those changes have on the joint strength. The results of our study indicate that the duration of post-welding flame straightening of X2CrNiN22-2-grade duplex steel, at a treatment temperature of 730°C, should not exceed 1 min.

Cracking in the translucent alumina ceramic during flame thermal shock

Crack measurement after thermal shock is usually considered as a replacement because real-time observation of thermal shock experiments is difficult to achieve. This paper presents an experimental approach for real-time displaying thermal shock cracking using oxygen-acetylene flame and high-speed imaging of translucent ceramic. We capture the crack propagation process, calculate the crack propagation speed, discuss the effect of sample size and flame heat flux on the crack propagation, and analyze the difference between the crack propagation under cold shock and hot shock. This paper further improves the mechanism of thermal shock damage of ceramic materials.

Synthesis of Nanomaterials in a Coaxial Flame

The paper presents the results of experimental studies of the synthesis of fullerenes C60 in a coaxial flame of benzene and acetylene at low pressures; of the synthesis of graphene in a coaxial flame of ethanol and propane, benzene, and acetylene; of the soot formation process in the coaxial flame of propane and ethanol. It has been established that the optimum temperature of a coaxial flame for the formation of fullerenes C60 is 970‒1000 °C with the carbon to oxygen ratio in the internal benzene-oxygen flame C/O ≈ 0.9 ÷ 1. The C/O ratio in an external acetylene-oxygen flame was maintained at a stoichiometric ratio. It was found that the preliminary (before feeding into the burner) treatment of the benzene-oxygen mixture using ultraviolet (UV) radiation with a wavelength of 254 nm promotes an increase in the yield of fullerenes. The synthesis conditions were optimized for: 5‒10 layers graphene in a coaxial flame of acetylene and ethanol; graphene containing more than 10 layers in a coaxial flame of propane and ethanol; one and two-layer graphene in a coaxial flame of ethanol and benzene. The possibility of a significant reduction of the formation of soot particles in the diffusion flame of propane by organizing its coaxial combustion with ethanol is shown.

Microstructure and Corrosion Behavior of Aluminum Coatings Prepared by High-Efficiency Supersonic Plasma Spraying and Oxygen–Acetylene Flame Spraying

Thermal spraying aluminum coatings have been widely used in the corrosion protection of mild steel in seawater. In this study, high-efficiency supersonic plasma spraying (HESP) and oxygen–acetylene flame spraying (FS) were used to prepare aluminum coatings. The micromorphology of the coatings was analyzed by a scanning electron microscope equipped with an energy-dispersive x-ray spectrometer. The phase identification of the coatings was conducted by an x-ray diffractometer. The Vickers hardness and bonding strength of the coatings were measured by an HMV-2000 Vickers hardness tester and MTS809 universal tensile tester. The corrosion resistance of the coatings was tested by an IM6ex electrochemical workstation. The results show that the aluminum coatings prepared by HESP have a denser structure, higher microhardness, higher bonding strength, and better corrosion resistance than those prepared by the traditional FS. After 480-h immersion in 3.5 wt.% NaCl solution, a dense corrosion product formed on the surface of aluminum coatings prepared by HESP prevents further corrosion of the coatings, but the aluminum coatings sprayed by FS demonstrate a serious pitting phenomenon.

Influence of LBE Temperatures on the Microstructure and Properties of Crystalline and Amorphous Multiphase Ceramic Coatings

An Al2O3–TiO2 amorphous composite coating with a thickness of 100–120 μm was fabricated on China low activation martensitic steel (CLAM steel) by oxygen acetylene flame spraying technology and the laser in-situ reaction method. We investigated the microstructures and mechanical properties of the coating after liquid lead-bismuth eutectic (LBE) alloy corrosion under different temperatures for 300 h and found that the corrosion temperature of the LBE had no observable effect on the microstructure and chemical phase of the Al2O3–TiO2 amorphous composite coatings. However, the mechanical properties (micro-hardness and shear strength) of the Al2O3–TiO2 multiphase coating deteriorated slightly with the increase in the immersion temperature of the LBE. As a result of oxygen acetylene flame spraying and laser in-situ reaction technology, it was found that the Al2O3–TiO2 amorphous composite coating exhibits an excellent LBE corrosion resistance, which is a candidate structural material for the accelerator-driven subcritical system (ADS) to handle nuclear waste under extreme conditions.

Mechanical, thermal, and ablative properties between graphene oxide and graphitic carbon nitride based carbon/phenolic composites: a comparative study

In this article, we investigated the interfacial, thermal and ablative properties of two nanofillers‐filled carbon/phenolic (CF/PR) composites. In particular, graphene oxide (GO) and graphitic carbon nitride (g‐C3N4) were used to produce lowly loaded (0.1 wt%) composites. The ablative properties of the composites were researched through an oxygen–acetylene flame torch test and were characterized through analysis of the post‐burning morphology, ablation depth and width. GO‐ and g‐C3N4‐filled composites showed 62.02 and 22.36% improvement in ablation resistance compared with the pristine, respectively, even with different mechanisms. The proposed mechanism of GO‐filled composite is that GO may significantly contribute to increasing the graphitization of the fiber surface and further improving the thermal resistance to high‐temperature ablation. However, thicker fiber diameter and charred layer of ablative zone in g‐C3N4‐filled composite can dissipate the flammable gases and improve the anti‐oxidation. POLYM. COMPOS., 39:E1928–E1938, 2018. © 2018 Society of Plastics Engineers

Spheroidizing mechanisms and simulation of spherical silica in Oxygen-Acetylene flame

In order for heat transferring and spheroidizing mechanisms of silica powders in Oxygen-Acetylene flame to be observed, the experiments were conducted and the Finite Element (FE) simulation method was employed. It has been certified that powder spheroidization occurred only at molten states, primarily depending on two major factors: melting time and particle size. Various particle sizes and various process parameters were studied systematically, whereas following the spheroidization mechanisms were concluded. At a flow rate of 40 L/min, the spheroidization rate percentage of 20 μm silica powders reached the maximum value. At a flow rate of 45 L/min, melting time of all particles were lower than 0.08 s, where it was difficult for 40 μm sized or larger powders to be spheroidized, also sharp corners of bigger powders were still observed. SEM results also revealed that powder spheroidization was affected by flow rate. The silica particle heat transfer time inside the gas flame furnace was reported and compared to SEM results. Through comparative analysis, the simulation results were in agreement with experimental results. The numerical model was capable of particle melting time calculation and can be used in spheroidizing results prediction to a certain extent.

Fabrication and Characterization of Carbon-Based Nanofluids through the Water Vortex Trap Method

This study designed an efficient one-step method for synthesizing carbon-based nanofluids (CBNFs). The method employs the vortex trap method (VTM) and an oxygen-acetylene flame, serving as a carbon source, in a manufacturing system of the VTM (MSVTM). The flow rate ratio of O2 and C2H2 was adjusted to form suitable combustion conditions for the reduced flame. Four flow rate ratios of O2 and C2H2 were used: 1.5 : 2.5 (V1), 1.0 : 2.5 (V2), 0.5 : 2.5 (V3), and 0 : 2.5 (V4). The morphology, structure, particle size, stability, and basic physicochemical characteristics of the obtained carbon-based nanomaterials (CBNMs) and CBNFs were investigated using transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, Raman spectrometry, ultraviolet–visible–near-infrared spectrophotometry, and a particle size-zeta potential analyzer. The static positioning method was utilized to evaluate the stability of the CBNFs with added EP dispersants. The evaluation results revealed the morphologies, compositions, and concentrations of the CBNFs obtained using various process parameters, and the relation between processing time and production rate was determined. Among the CBNMs synthesized, those obtained using the V4-0 flow rate ratio had the highest stability when no EP dispersant was added. Moreover, the maximum enhancement ratios of the viscosity and thermal conductivity were also obtained for V4-0: 4.65% and 1.29%, respectively. Different types and concentrations of dispersants should be considered in future research to enhance the stability of CBNFs for further application.

Experimental Parameter Calculation of Welding Deformation Correction by Flame Straightening

In order to study the method of oxygen-acetylene flame straightening parameter design for welding deformation correction, flame straightening experiment and calculation of welding deformation of the T-shaped structure of double bottom plate and stiffened plate on the 110000 tons refined oil products/crude oil ship are completed. The results show that: Flexure deformation is formed between the two adjacent stiffened plate after welding process; The deformation is largest on the free edge of bottom plate; When the thickness of stiffened plate remains unchanged, smaller thickness of the bottom plate leads to larger the flexural deformation of both bottom plate between stiffened plates and the free edge of the bottom plate. The calculation method of oxygen-acetylene flame parameter based on welding heat input is feasible, and the calculated oxygen-acetylene flame parameters can be used to eliminate flexure deformation of T-shaped structure.

Flexible NO 2 gas sensors based on sheet-like hierarchical ZnO 1− x coatings deposited on polypropylene papers by suspension flame spraying

Abstract 2D sheet-like ZnO coatings composed of nanoparticles were deposited on flexible polypropylene papers equipped with gold electrodes in three steps. Firstly, sheet-like ZnO powder was synthesized by direct precipitation method. Then, the as-synthesized powders were dispersed in anhydrous ethanol to form feedstock suspension. At last, the feedstock suspension was injected into the acetylene-oxygen flame to deposit ZnO coatings. X-ray diffraction and field-emission microscopy results revealed that the coatings were hexagonal phase and porous hierarchical structure. With an increase in spray distance, the coatings exhibited a morphology with smaller particle size and sheet thickness. Photoluminescence and X-ray photoelectron spectra indicated that large amounts of oxygen vacancies were introduced into the coatings, and oxygen vacancy concentration increased with the spray distance. UV–vis spectra showed that the light absorption of the coatings was extended to visible light region, and wider absorption range was obtained when the spray distance was increased. The ZnO coatings exhibited good responses to sub-ppm level NO2 at room temperature under white LED light illumination, and the coating deposited with longer spray distance presented a better NO2 sensing performance.

Fabrication and Characterization of Nanocarbon-Based Nanofluids by Using an Oxygen-Acetylene Flame Synthesis System.

In this study, an oxygen–acetylene flame synthesis system was developed to fabricate nanocarbon-based nanofluids (NCBNFs) through a one-step synthesis method. Measured in liters per minute (LPM), the flame’s fuel flows combined oxygen and acetylene at four ratios: 1.5/2.5 (P1), 1.0/2.5 (P2), 0.5/2.5 (P3), and 0/2.5 (P4). The flow rate of cooling water (base fluid) was fixed at 1.2 LPM to produce different nanocarbon-based materials (NCBMs) and various concentrations of NCBNFs. Tests and analyses were conducted for determining the morphology of NCBMs, NCBM material, optical characteristics, the production rate, suspension performance, average particle size, zeta potential, and other relevant basic characteristics of NCBNFs to understand the characteristics and materials of NCBNFs produced through different process parameters (P1–P4). The results revealed that the NCBMs mainly had flaky and spherical morphologies and the diameters of the spherical NCBMs measured approximately 20–30 nm. X-ray diffraction and Raman spectroscopy revealed that the NCBMs contained graphene oxide (GO) and amorphous carbon (AC) when the oxygen flow rate was lower than 1.0 LPM. In addition, the NCBMs contained reduced GO, crystalline graphite (graphite-2H), and AC when the oxygen flow rate was higher than 1.0 LPM. The process parameters of P1, P2, P3, and P4 resulted in NCBMs produced at concentrations of 0.010, 0.013, 0.040, and 0.023 wt%, respectively, in NCBNFs. All the NCBNFs exhibited non-Newtonian and shear-thinning rheological properties. The P4 ratio showed the highest enhancement rate of thermal conductivity for NCBNFs, at a rate 4.85 % higher than that of water.

Numerical simulation of silica particle trajectory in flow field and silica particle spheroidizing in oxygen–acetylene flame spheroidization process

A numerical simulation was developed for particle trajectory in flow field and spheroidizing of silica particle in oxygen–acetylene flame spheroidization process. Gas flow field and silica particle behavior in oxygen–acetylene flame spheroidization process was simulated using a Computational Fluid Dynamics (CFD) package FLUENT. A model was proposed for optimizing spheroidization process of silica particle. Oxygen gas and acetylene gas were used as the continuous phase. Silica particle was used as the dispersed phase. The three-dimensional, steady and isothermal flow field was showed for illustrating the continuous phase and the dispersed phase. Conservation equations of mass and momentum for each phase were solved using the finite volume numerical technique. Various gas conditions were discussed systematically. The injected silica particle trajectories were simulated by using dispersed particle surface trajectory. The trajectories and spheroidizations of different size particles were analyzed. The results of numerical simulation reveal that the flame length was reasonable and overall temperature was highest when acetylene gas flow rate was 10L·min−1, oxygen gas flow rate was 20L·min−1 and powder carrying gas flow rate was 5L·min−1 and 40μm silica particles were difficult to finish spheroidizing within 5×10−4s. The comparison shows that temperature distribution, velocity distribution, particle trajectories, and deformation which were predicted by simulation, were in good agreement with the corresponding experimental results.

Improving a Brazed Joint Structure, with a New Ecological Brass

In the frame of the Romania-Republic of Serbia IPA Cross-border Cooperation Programme, in the Project Ecosolder, the National Research & Development Institute for Welding and Material Testing - ISIM Timisoara, Romania, has elaborated a brazing procedure with a new ecological brass of the type B-Cu60ZnSnSiMn, elaborated by the Mining and Metallurgy Institute - MMI Bor, Serbia. The brazing test was carried out according to the standard EN 13134:2000 related to the brazing procedure approval. The applied process is oxygen-acetylene flame brazing of steel sheets, with the sizes of 87 mm x 80 mm, thickness of 1.0 mm and overlap 7 mm. Images of the execution of the brazing procedure are presented, with comments on every phase. The appearance of the joint is adequate, by the visual examination. By the metallographic analysis, the constituents of the deposited filler metal are dendritic solid solution, with fine particles of Sn, Si and Mn. No defects have been revealed. The values of the hardness are 91-133 HV1. The results of the specific shear test comply with the requirements. The technological, ecological, structural and mechanical characteristics of this filler alloy are adequate. Some applications of brazing with the new ecological brass are recommended.