Property Testing Research Articles

Nondestructive evaluation of microstructure and mechanical property of post-processing annealed selective laser melted 316L stainless steel by laser ultrasonics

By using the laser ultrasonics nondestructive technology, combined with the microstructure and mechanical property of post-processing annealed selective laser melted 316L stainless steel characterized by scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and mechanical property testing, selective laser melted 316L stainless steel after post-processing annealing was evaluated. The results show that the frequency domain attenuation coefficient of ultrasonic waves is positively correlated with the average grain size; the time domain attenuation coefficient of ultrasonic waves is negatively correlated with the low angle boundary content. The tensile strength has a good correlation with the time domain attenuation coefficient and wave speed, the correlation coefficients R2 are 0.95 and 0.89 respectively; the yield strength correlates with the time domain attenuation coefficient, the correlation coefficient R2 is 0.76; the elongation has a good correlation with the frequency domain attenuation coefficient and wave speed, the correlation coefficient R2 is 0.90 and 0.86 respectively.

Effect of Voltage variation on the Geotechnical Properties and Removal Efficiency of Heavy Metal Contaminants from Contaminated Soil using Electrokinetic Remediation Technique

A lot of research work has shown that despite the effectiveness of the electrokinetic remediation technology in decontaminating heavy metal contaminated soils, more work is still required to fully understand the role of voltage in the remediation process. There is need to establish the optimum voltage that would best remove heavy metals from such contaminated soil and its attendant effect on the geotechnical properties of the remediated soil. Effect of voltage variation on the removal efficiency of lead, copper and the geotechnical properties of remediated heavy metal contaminated soil using electrokinetic remediation technique was investigated in this research. The contaminated soil was remediated by applying direct current (DC) to the remediation setup at 0.5V/cm, 1.0V/cm, 1.5V/cm and 2.0V/cm. The concentration of the heavy metals after remediation were determined using the Oxford Instrument Analyzer to evaluate removal efficiency, geotechnical properties tests were also conducted on the soil specimens at each phase of remediation. The results showed that the lead removal efficiency was highest at 2.0V/cm (86%) with the shortest remediation time of 5days and lowest at 0.5V/cm (39%) at 9days. 52% of copper was removed at 2.0V/cm in 5days and 29% at 0.5V/cm after 9days of remediation. At 1.0V/cm, the lead and copper removal efficiency are 75% and 40% respectively. There was no significant change in the Specific Gravity of all the soil samples with the test results lying between 2.0 and 2.2. The soil is generally silty fine sand with not less than 40% passing the sieve no.200 (75micron). 45% passed through sieve 75micron for unremediated soil and slightly reduced to 40%, 40.4% and 40.2% for 30V, 45V and 60V respectively. The soil is non-plastic with the liquid limit of between 25.8% and 29.5% belonging to the A-4 group of soil. The maximum dry density improved across all the three compactive efforts, from 1.8390g/cm3 to 1.8480g/cm3 with WAS compactive effort and from 1.8000g/cm3 to 1.8320g/cm3 with BSL method with an average optimum moisture content of 10%. The CBR values increases with increase in voltage applied. The unsoaked CBR values averagely increased with 31%, 18% and 7% for BSH, WAS and BSL compactive efforts respectively. The durability index with resistances of 89% and 90% to loss in strength was recorded at 1.0V/cm and 1.5V/cm respectively, this, when compared to the resistance to loss in strength of 71% in unremediated soil has respectively 25.3% and 26.8% durability advantages. There was also a consistent increase in the UCS values, from 381kN/m2 to 474kN/m2 and from 351kN/m2 to 447kN/m2 when WAS and BSL methods of compaction were used. Generally, there was improvement in the geotechnical properties of the remediated soil. These improvements are maximum at 1.0V/cm and 1.5V/cm with little or no further improvement at 2.0V/cm. It is recommended that 1.0V and 1.5V are suitable for remediation purpose since it requires low energy consumption.

Composite fluorescence probe towards a smart coating for early corrosion detection of carbon steel

Herein, a composite fluorescent probe was developed as a smart indicator in acrylic resin-based coatings for the early detection of steel corrosion. The Fe3+-sensitive Rhodamine B derivative probe (Rxbxja) was synthesized, and the SiO2 nanoparticle-supported probe S-Rxbxja was prepared through the hydrolysis of tetraethyl orthosilicate (TEOS). The successful synthesis of S-Rxbxja was confirmed using a variety of techniques i.e. SEM and FTIR. A fluorescence microscope was utilized to assess the self-reporting performance of coatings. EIS and seawater immersion tests were employed to evaluate the corrosion resistance of the coating. The fluorescence test results revealed the absence of premature fluorescence in the composite coating, owing to the exceptional compatibility between S-Rxbxja and the coating. The scratched area in the 0.5 wt% sensor-doped coatings exhibited fluorescent and colorimetric dual-channel signals after soaking in 3.5 wt% NaCl solution for 2 h before any visible corrosion phenomenon. The EIS results demonstrated that the |Z|0.01Hz value of composite coating maintained 107 Ω cm2 even after being immersed in a 3.5 wt% NaCl solution for 7 days, indicating the excellent anti-corrosion properties of the S-Rxbxja coating. Moreover, mechanical property tests showed that the S-Rxbxja coating had excellent mechanical properties due to the introduction of SiO2 nanoparticles.

Numerical Simulation and Microstructure Analysis of 30CrMnMoRe High-Strength Steel Welding.

Welding experiments were conducted under different currents for single-pass butt welding of high-strength steel flat plates. The microstructure of welded joints was characterized using OM, SEM, and EBSD, and the welding process was numerically simulated using a finite element method. According to the grain size obtained by electron microscope characterization and the temperature data obtained by simulation, the microstructure and mechanical properties of coarse grain and fine grain areas of the heat-affected zone were predicted by using the material microstructure and property simulation software. Finally, the results of mechanical properties simulation were verified through mechanical property testing.

Three-dimensional indentation test system for observing the distribution of internal mechanical properties in materials

This paper describes the development of a three-dimensional (3D) indentation test system capable of observing the distribution of mechanical properties in structural materials. Serial sectioning with destructive treatment has traditionally been used as a method for observing microstructure within materials in three dimensions. The serial sectioning methods using precision cutting has attracted particular attention as it enables the observation of large sample volumes. However, those methods can only observe the microstructure as image, not the mechanical properties such as hardness and elastic modulus. To measure the 3D distribution of the mechanical properties of the material, it is effective to combine repeated cutting and indentation tests on each cutting surface. Morever, combining the image observation and mechanical property tests could allow a more sophisticated analysis of the interior of material. To implement this method, we have constructed an indentation test system on a precision machine using a Berkovich indenter, micro-force sensor, and micro-movement stage.In order to achieve a 3D indentation test, it is considered necessary to unify the measurement positions in the depth direction. Furthermore, the unloading rate needs to be controlled in order to carry out stable indentation tests. Therefore, we propose a method of 3D indentation test that can precisely control the maximum depth of indentation and unloading speed.In this paper, we devise a method for driving the constructed system and a method for obtaining data and confirm the accuracy of these methods by experiment. In addition, we determine indentation depth and unloading speed which are suitable for our method by performing indentation tests on a block for ultra-microhardness. Finally, we practice 3D indentation test in which the cutting and indentation tests are repeated on specimens with different mechanical properties in the depth direction. Experimental results show that our indentation test system is appropriate to measure three-dimensional mechanical properties inside the material.

Effect of diammonium hydrogen phosphate coated with silica on flame retardancy of epoxy resin.

Epoxy resin has become one of the most widely used polymers owing to their excellent comprehensive properties. However, the inherent inflammability of epoxy resin (EP) has seriously limited its application in a range of fields with high fire safety requirements. Herein, a novel shell-core hierarchy architecture (DAP@SiO2) was prepared, composed of diammonium hydrogen phosphate (DAP) and in situ grown silica, and its structure and morphology were characterized by electron microscopy and infrared spectroscopy. The results indicated that silica particles were uniformly coated onto the surface of DAP. The modified DAP was used to reinforce the epoxy resin. The thermal stability of the EP blends was studied with the use of thermogravimetric analysis. The diammonium phosphate in DAP@SiO2 flame retardant produces pyrolysis gases such as NH3 and N2 during decomposition, diluting the concentration of oxygen and flammable volatile products around the flame. Secondly, silica migrates to the surface of epoxy resin to form a shielding layer, forming compounds containing Si-O-Si and O-Si-C structures, which can be cross-linked with other condensed phase products, greatly improving the thermal stability of the carbon layer. Fire behavior was evaluated using the limiting oxygen index (LOI), vertical burning test, and the cone calorimetry, and the flame retardancy mode of action was explained. With 12% of DAP@SiO2 involved, the EP blend passes UL-94 V-0 level, and its limiting oxygen index (LOI) reaches 33.2%. The incorporation of DAP@SiO2 in an EP matrix showed a slight reduction in the heat release and smoke production. The flame retardant mode of the EP polymer shows that its flame retardant and smoke suppression characteristics are related to the interaction of flame retardants in the gas phase and condensed phase. The mechanical properties test results illustrated that the tensile strength, elastic modulus and impact strength of EP/3%DAP@SiO2 are improved compared with pure EP. This is due to the crosslinking reaction between a large number of amino groups on the surface of DAP@SiO2 and the epoxy group on the epoxy resin, which significantly enhances the interfacial compatibility between DAP@SiO2 and epoxy resin, making the combination of DAP@SiO2 and epoxy resin closer.

4D printing of the ferrite permanent magnet BaFe12O19 and its intelligent shape memory effect

4D printing of the barium ferrite permanent magnets provides new opportunities for intelligent structure and process innovation of permanent magnets. In this paper, the preparation, filament manufacture, and intelligent printing methods with shape memory/recovery effect are studied for the barium ferrite permanent magnet. Firstly, the PLA/TPU/BaFe12O19 composite materials are developed by adding different contents of ferrite permanent magnet BaFe12O19 powders into the PLA/TPU (polylactic acid/thermoplastic polyurethane) matrix. The weight percentage of the BaFe12O19 is 10–40 wt% with an interval of 10 wt%. Secondly, the composites are pelletized and further extruded to manufacture composite filaments with different BaFe12O19 contents. Scanning electron microscope (SEM) is used for the microstructural analysis. The BaFe12O19 particles are uniformly distributed in the PLA/TPU matrix, and the slight particle agglomeration phenomenon occurs in the composite filaments with 30 and 40 wt% BaFe12O19. The thermal properties of PLA/TPU/BaFe12O19 composite filaments are analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After adding the barium ferrite particles, the glass transition temperature of the composite filaments changes within a small range from 53.5 °C to 55 °C. Thirdly, the filaments are successfully manufactured to magnet parts by the fused deposition modeling (FDM) 3D printing for the tests of mechanical, magnetic, and shape recovery properties. With the increase of the barium ferrite content, the magnetic properties show a rising trend, proving the feasibility of using 3D printing technology to make magnets. The shape memory effects of the printed parts are excellent and the shape recovery ratios show a rising trend, from 85.6 % to 88.9 % under heat contact stimulus and from 88.9 % to 97.8 % under electromagnetic induction non-contact stimulus. Relatively, the parts hold fast response speed due to direct contact with the heat source under the heat stimulus, and the parts hold higher shape recovery ratios due to more heats produced under the electromagnetic induction stimulus. The addition of magnetic particles is helpful to improve the heat transfer ability and provide the possibility of non-contact heat transfer. The magnetic parts with complex structure and intelligent shape memory/recovery effect can be achieved for special application requirements. As a result, the research of this paper expands preparation methods of new magnetic composite materials, explores the manufacture process for intelligent magnets and lays a solid foundation for the development of new permanent magnet devices.

Development of highly stable low supercooling paraffin nano phase change emulsions for thermal management systems

Current research on thermal management systems focuses on aspects such as structural optimization of liquid cooling channels, with less research on the development of cooling media. Phase change emulsions, as latent heat functional fluids with significant potential, enhance heat transfer efficiency and temperature control in thermal management systems. However, the issues of significant supercooling and poor stability have hindered the further development of phase change emulsions. In this study, a highly stable, low-supercooling paraffin nano emulsion was successfully prepared by ultrasonication using SDBS, Span80, and Tween80 as composite surfactants and titanium dioxide nanoparticles as nucleating agents. It was found that the emulsion maintained excellent stability for 180 days of static stability and 200 thermal cycles without significant stratification. Subsequently, thermophysical property tests showed that the emulsion had a latent heat of phase transition of 45.48 J·g−1, and maintained good electrical insulating properties. The successful dispersion of 0.9 wt% titanium dioxide nanoparticles in the presence of SDBS resulted in a 77 % reduction in supercooling and a 20.5 % increase in thermal conductivity. Meanwhile, no instability was observed in the emulsion over 90 days of static stability test and 200 thermal cycles. The titanium dioxide-modified paraffin nano emulsions are characterized by high energy storage density, low supercooling, excellent stability, high thermal conductivity, and good electrical insulating properties, which give them significant potential as a cooling medium in thermal management systems.

Enhancing vacuum surface flashover voltage of alumina insulator by self-assembly of fluorine-containing molecule

In this study, a fluorocarbon chain was grafted on the surface of the alumina insulator through the molecule self-assembly of perfluorododecyl trichlorosilane to enhance the vacuum surface flashover voltage. A hydrocarbon chain with the same molecular structure, devoid of fluorine element, was also grafted through the self-assembly of dodecyl trichlorosilane to enable comparison. The surface state examination of the self-assembled alumina insulators shows that both the molecules are attached to the alumina surface. The arrangement of the molecules on the surface is regular. Surface property tests reveal that the fluorocarbon chain endows the surface of alumina with a lower secondary electron emission yield and a lower gas adsorption volume than the hydrocarbon chain. Correspondingly, the surface flashover voltage of the fluorocarbon chain grafted insulator is higher than that of the hydrocarbon chain. This implies that the surface flashover voltage can be improved through surface fluorination, which converts hydrocarbon bonds to fluorocarbon bonds. The study demonstrates this possibility at the molecule level.

Study on the thermo-mechanical properties of adaptive thermal control anchoring materials in high-geothermal tunnels

The heat conduction of the rock in high-geothermal tunnels can damage the grout during the initial hardening process, which directly affects the effectiveness of the anchoring support of the surrounding rock. This paper proposed the incorporation of phase change materials in grout to provide the new modified grouting material with the ability to control temperature by exploiting the phase change absorption and exothermic properties of the material. The changes in thermomechanical parameters of anchoring grout containing microencapsulated phase change material (m-PCM) under high geothermal environment were investigated. The influences of m-PCM content on the temperature control effect and mechanical properties of modified grout under different high geothermal environments were explored through macro-mechanical, micro-structural, and thermo-physical property tests on the specimens. The results indicated that m-PCM can effectively control the early hydration temperature of the grout in a high temperature environment, which can slow down the rate of change of the hydration temperature and reduce the peak temperature. The temperature control performance of modified grouts improved as the phase-change content increased, but the mechanical properties showed a significant decline after the initial increase. The results of the scanning electron microscope (SEM) analysis indicated that the high curing temperature had a negative impact on the internal structural integrity of the grout. The addition of a small amount of m-PCM reduced the fractal dimension and irregularity of the pore space in the grouting material, ultimately improving the strength of the grout body. The addition of a certain amount of m-PCM could significantly reduce the thermal conductivity of the grout, with the thermal conductivity of the specimens decreasing as the temperature increased. These study results provided valuable experimental data and theoretical support for the design of cement-based grouting materials in high-geothermal tunnels.

Deformation and microstructure radial gradient evolution of AZ31 magnesium alloy bar during three-roll skew rolling

AZ31 magnesium alloy bar with radial gradient microstructure was prepared by three-roll skew rolling process (TRS), and achieving an excellent combination of ductility and strength. To elucidate the formation mechanism of this gradient microstructure, the deformation behavior during rolling was analyzed through experiments and simulations. The simulation results indicated that the metal flow of the bar in a spatial helical trajectory during rolling, with the trajectory inclination angle gradually decreasing from the center to the surface, promoting dynamic recrystallization in the surface and near-surface regions. The radial equivalent strain decreased from 1.5 at the surface to 0.01 at the center, and the shear strain decreased from 0.051 at the surface to 0.00012 at the center. Experimental results showed that the grain size of the bars decreased from 49.77 µm at the center to 19.72 µm at the surface, and the tensile twin volume fraction decreased from 34.1 % to 19.4 %. Dynamic recrystallization predominantly occurred in the outer ring region of the bars, while significant {10−12} tensile twin activation was observed in the central region, with twin-induced dynamic recrystallization observed at the twin boundaries. Mechanical property tests demonstrated that the gradient structure endowed the bars with a favorable combination of strength and elongation, with hardness significantly increasing from 50 HV at the center to 90 HV at the surface. This indicates that the three-roll skew rolling technology effectively promotes dynamic recrystallization at the surface, and the resulting gradient microstructure achieves an excellent combination of strength and plasticity in magnesium alloy bars.

Mesoscale simulation method for preplaced aggregate concrete based on physics engine

Preplaced aggregate concrete (PAC) has up to 60 % aggregate volume content, making mesoscale modelling difficult. A novel mesoscale simulation method based on physics engine was proposed in this study to accurately simulate the coarse aggregate skeleton of PAC. Unlike in conventional mesoscale simulations, point-to-point contacts between aggregates were formed due to virtual gravity in the physics engine. To verify this novel method, mechanical property and shrinkage behavior tests of PAC were conducted under different aggregate gradings and with different expansive agents. For the mechanical property test, the simulation results were compared with the test results in terms of the aggregate stacking state, failure mode, stress–strain curve, and mechanical property parameters. Repeatability and aggregate shape analyses were performed using finite element (FE) model. A similar comparison between the simulation and test results was also performed for the shrinkage behavior. A shrinkage coefficient reflecting the relationship between grout and PAC shrinkage was proposed. This novel mesoscale simulation method based on physics engine is particularly suitable for PAC. However, it is not limited to PAC and can be applied to the simulation of conventional concrete, thus solving the problem of traditional simulation methods that struggle to achieve a high aggregate fraction.

Compressive mechanical performance and microscopic mechanism of basalt fiber-reinforced recycled aggregate concrete after elevated temperature exposure

To improve the mechanical properties of recycled aggregate concrete (RAC) after elevated temperature exposure, this study employed basalt fiber (BF) as reinforcing material incorporated into RAC. The replacement ratio of recycled coarse aggregate (RCA), the content of BF, and the temperature were utilized as the change parameters, and 27 groups of basalt fiber reinforced recycled aggregate concrete (BFRRC) specimens were designed to carry out the compressive strength test after elevated temperature. The heating rate was set at 2.5 °C/min to avoid any possible explosion of the cylindrical specimen during the heating process. The specimens were treated for 6h after reaching the desired temperature, and then the furnace door was opened for natural cooling to room temperature. After observing the physical properties of the specimens, the basic mechanical properties test was carried out, and the microscopic mechanism was analyzed in depth by electron microscopy. The results showed that the defects inherent in RCA and the continuous accumulation of elevated temperature damage gradually reduced the compressive mechanical performance of BFRRC but that the toughening and cracking-resistance action of BF effectively improved the compressive mechanical performance of BFRRC. BF enhanced the compressive mechanical performance of RAC through bridging and crack resistance action mechanisms, but the higher the temperature became, the smaller the enhancement was. The cube compressive strength and axial compressive strength of the specimens decreased with the increase of temperature. With the same replacement ratio and fiber dosage, increasing the temperature from 300 °C to 600 °C, the decrease in cube compressive strength and axial compressive strength was the most significant, which was between 36.4 %–48.1 % and 51.1 %–62.6 %, respectively.

Experimental investigations on characterizing the uniaxial mechanical property variations along the thickness of hydrogenation reactor welded joints by spherical indentation tests

To meet the demands for non-destructive testing of uniaxial mechanical properties of welded joints of thick-wall hydrogenation reactors, this study provides an experimental investigation on whether the spherical indentation tests (SITs) can accurately characterize the uniaxial mechanical property variations along the thickness of welded joints. The phenomenologically summarized empirical method (i.e., the Kwon method) and the semi-analytical method (i.e., the simplified-IIEM) were selected as representatives, and their reliability was judged from the viewpoints of stress-strain prediction, the inversion accuracy and repeatability of strength, and the ability to characterize the variation of uniaxial mechanical properties along the thickness of welded joints. Characteristics of the inverse predictions were analyzed, and the source of errors in each method were extensively investigated. This study provides a theoretical and technical guidance for the engineering application and promotion of SITs.

Surface Layer Performance of Low-Cost 3D-Printed Sliding Components in Metal-Polymer Friction

Abstract The paper presents the results of contact strength and tribological property tests of spare parts made of a popular resin using a 3D DLP printing technology. Two printer models by the same manufacturer were used in the study. The post-processing technique, which shapes the final functional properties, was diversified. Surface performance properties were compared, i.e. Shore hardness, indentation hardness, Martens hardness, elastic modulus, and parameters related to surface creep and relaxation. Tribo-logical durability in rotary motion and tribological wear in reciprocating linear motion were also evaluated using micro- and nanotribometers. This was followed by surface analyses of the friction track of the analysed materials using microscopic methods: a scanning electron microscope, a WLI interferometric microscope, and an optical microscope. The results were statistically processed and the relationship between the parameters determined in the indentation test was determined.

A preliminary study of the mechanical properties of 3D-printed personalized mesh titanium alloy prostheses and repair of hemi-mandibular defect in dogs.

This study is a preliminary investigation exploring the mechanical properties of three-dimensional (3D)-printed personalized mesh titanium alloy prostheses and the feasibility of repairing hemi-mandibular defects. The ANSYS 14.0 software and selective laser melting (SLM) were used to produce personalized mesh titanium alloy scaffolds. Scaffolds printed using different parameters underwent fatigue property tests and scanning electron microscopy (SEM) of the fracture points. Models of hemi-mandibular defects (encompassing the temporomandibular joint) were created using beagle dogs. Freeze-dried allogeneic mandibles or 3D-printed personalized mesh titanium alloy prostheses were used for repair. Gross observation, computed tomography (CT), SEM, and histological examinations were used to compare the two repair methods. The prostheses with filament diameters of 0.5 and 0.7 mm could withstand 14,000 times and >600,000 cycles of alternating stresses, respectively. The truss-structure scaffold with a large aperture and large aperture ratio could withstand roughly 250,000 cycles of alternating forces. The allogeneic mandible graft required intraoperative shaping, while the 3D-printed mesh titanium alloy prostheses were personalized and did not require intraoperative shaping. The articular disc on the non-operated sides experienced degenerative changes. No liver and kidney toxicity was observed in the two groups of animals. The 3D-printed mesh titanium alloy prostheses could effectively restore the shape of the mandibular defect region and reconstruct the temporomandibular joint.

Failure Analysis of Bypass Rupture of Flowmeter in Steam Pipeline

Abstract A petrochemical company’s pipeline ruptured in the flowmeter bypass of the main steam pipeline during a steam blowdown before commissioning, resulting in material failure and inoperability. The cause of the pipe rupture needed to be detected experimentally. To study the failure in the steam pipeline of a flowmeter of bypass rupture, visual inspection, mechanical properties testing, chemical composition analysis, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Mechanical property. The experiments confirmed the reason for the bypass rupture of the 15CrMoG steam pipeline: improper heat treatment transforms the material’s structure, and the pearlite spheroidization (PC) leads to the deterioration of the material’s mechanical properties. The main manifestations are as follows: the grains in the superheated zone of the welding exhibit a coarse morphology, and a distinctive superheated Widmanstatten structure is formed due to rapid cooling, resulting in a significant reduction in material plasticity and impact toughness. High-temperature oxidation occurs, accompanied by localized enrichment of Cr-element in certain areas, while other regions experience Cr depletion, resulting in the deterioration of material properties.

Passive battery thermal management and thermal safety protection based on hydrated salt composite phase change materials

Lithium-ion batteries (LIBs) are progressing towards higher energy densities, extended lifespans, and improved safety. However, battery thermal management systems are facing increased demand owing to high-rate charging and discharging, dynamic operating conditions, and heightened thermal safety concerns. Therefore, this paper proposes a novel composite phase change material (CPCM) comprising Na2SO4-10H2O as the core phase change material (PCM) and expanded graphite as the thermal conductivity enhancer. The CPCM offers high latent heat, superior thermal conductivity, and a two-stage temperature control function for battery thermal management and safety. The optimal mass CPCM ratio, determined through comprehensive characterization and thermal property tests, resulted in a melting point of 29.05°C, latent heat of 183.7 J.g−1, and high thermal conductivity of 3.926 W.m−1.K−1. During normal LIB operations, the CPCM efficiently absorbs and transfers heat, reducing the peak LIB temperature from 66 to 34°C at 15°C ambient temperature during a 3.7C high-rate discharge. Under dynamic conditions, the peak temperatures across the three cycles were consistently controlled at 36.7, 36.4, and 35.8°C, respectively. In a thermal runaway state, the thermochemical heat storage of hydrated salt dehydration effectively slowed LIB temperature increase, delaying the time to reach 130°C by 187 s. Suppression of the temperature rise outside the CPCM, combined with an extended dehydration plateau of up to 320 s, prevented the occurrence and propagation of thermal runaway in the battery.

Cultivation of chlorella vulgaris using aquaculture wastewater: Assessing its viability as a promising resource for biodiesel production

This study investigates the viability of utilizing Chlorella vulgaris cultivated in aquaculture wastewater as a feedstock for biodiesel production. The research involved scaling up the algal culture from 10 ml to 10 liters in a photobioreactor, optimizing growth conditions, and analyzing the water parameters of the aquaculture wastewater medium. The results showed successful growth of the algal culture, with the highest growth rate achieved on day 15 in the 10-liter reactor. The harvested biomass was converted into biodiesel through direct transesterification, and the produced biodiesel was characterized using Fourier-transform infrared spectroscopy (FTIR) and fuel property tests. The FTIR analysis confirmed the presence of functional groups indicative of esterification, validating the successful conversion of the wet biomass into biodiesel. The fuel property tests revealed that the algal biodiesel exhibited marginally higher kinematic viscosity but a favourable flash point compared to established standards. Emission tests demonstrated an increase in CO2 and hydrocarbon emissions with higher engine loads, aligning with combustion principles. The findings highlight the potential of utilizing aquaculture wastewater as a sustainable medium for cultivating Chlorella vulgaris and producing biodiesel, contributing to the development of more resource-efficient and environmentally friendly biofuel production methods.

High-temperature tensile rupture property of (Nb,W) co-alloying TiAl-based alloys

In order to explore whether (Nb,W) co-alloying TiAl-based alloys with relatively higher W addition have better high-temperature tensile rupture property, Ti-44Al-4Nb-1 W-0.1B alloy is designed and prepared. Ti-44Al-8Nb-0.1B alloy and Ti-44Al-7.2Nb-0.2 W-0.1B alloy are also prepared for comparative study. The rupture property testing is carried out at 800 °C and different tensile stresses. The property data, macro/microstructure evolution, fracture surface, W content, crack failure behaviors are studied. The results show that the (Nb,W) co-alloying alloys have better rupture property than the pure Nb alloying alloy. For the (Nb,W) co-alloying alloys, the higher W contained Ti-44Al-4Nb-1 W-0.1B alloy has the better property under lower tensile stress, and the lower W contained Ti-44Al-7.2Nb-0.2 W-0.1B alloy has the better property under higher tensile stress. The relationships of rupture life t and stress σ for the three alloys are given. All the three alloys have a coupling fracture mode of ductile fracture and brittle fracture. The ductile fracture exhibits the typical dimple characteristics. The brittle fracture exhibits the typical trans-granular cleavage, river-like pattern and trans-lamella fracture characteristics. The higher the stress, the more brittle fracture characteristics there are. After rupture property testing, the (α2 + γ) lamella colony sizes of the three alloys all decrease, indicating that DRX and grain boundary slip occur not only along (α2 + γ) lamella colony boundary, but also inside it. The colony boundary regions have the stress concentration, where the B2 phase produces the better buffering and coordination, and as well as the dislocation tangles, DRX and grain boundary slip can be found by EBSD and TEM. EPMA results show that the more W added in the alloy, the more W content is in the (α2 + γ) lamella matrix, which is beneficial for the rupture property. However, more W addition will also lead to the formation of more B2 phase in the initial as-cast microstructure. So that, under higher tensile stress, when the stress intensity factor K is higher, the crack failure is more likely to occur.