Results in Materials最新文献

In this study, the hot processing map was drawn to study the hot formability of high strength automotive steel Docol 1500 Bor. The quenching microstructure of the test steel was observed under optical microscope and EBSD and the deformed PA (parent austenite) was reconstructed under different conditions according to KS (Kurdjumov–Sachs) OR (orientation relationship). The results indicate that the optimal deformation conditions in the stable region are strain rates less than 1s⁻¹ and temperatures higher than 900 °C. Overall, the fine-grained martensite structure with a larger Schmid factor has a better deformation ability for subsequent service. The texture component {011} <100> appears in the PA at the strain rate of 5 s⁻¹ and the temperature of 1000 °C, while the dynamic recrystallization is significantly inhibited. The quenched martensite is found coarse. In the stable region, the recrystallized austenite grains with certain deformation transforms into the martensite grains with low cumulative misorientation values and higher Schmid factors. In the unstable region, the austenite grains are smaller in size, in which severe cumulative misorientation caused by higher strain rates leads to poor plasticity.

This study delves into the intricate interaction between multi-walled carbon nanotubes (MWCNTs) and the Sn–Ag–Cu solder system, highlighting its relevance in lead-free soldering applications. Reflow and isothermal aging induce the formation of intermetallic layers at the joint interface, including Cu₆Sn₅, Cu₃Sn, and irregularly shaped Ag₃Sn particles. The addition of MWCNTs leads to the flattening of Cu₆Sn₅ grains, restraining their growth and potentially improving mechanical strength. Notably, MWCNTs exhibit a relatively high affinity with Ag₃Sn. Grain size distribution analysis indicates that MWCNTs reduce particle size, effectively suppressing intermetallic compound growth. Over time, grain size increases due to simultaneous coarsening and growth during isothermal aging. In the growth kinetics analysis of intermetallic compounds in SAC305-MWCNTs solder joints, stable behavior is observed for Cu₃Sn growth, driven by solid-state diffusion between Cu₆Sn₅ and Cu. In contrast, Cu₆Sn₅ exhibits significant variations in growth behavior with temperature changes. Furthermore, the evaluation of activation enthalpy for Cu₃Sn growth in the Cu/(SAC305-MWCNTs) and Cu/SAC305 diffusion couples reveals similar n and k values of the power function for the layer growth, indicating a comparable rate-controlling process for Cu₃Sn growth. The presence of MWCNTs in the solder does not significantly influence the rate-controlling process or activation enthalpy for Cu₃Sn growth, contrasting with the observed effects on Cu₆Sn₅ growth. This study provides valuable insights into the interactions within the SAC305-MWCNTs solder system, offering significant implications for lead-free soldering applications.

Heteroatom doping has been demonstrated as an efficient method to increase the fluorescence quantum yield efficiency of carbon dots. Co-doping with heteroatoms leads to additional active sites on carbon dots, both extending their use in sensing systems and improving the sensitivity of detection. In this study, the synthesis of nitrogen and sulfur co-doped carbon dots (N, S-CDs) through a single step hydrothermal process was reported, utilizing citric acid and thiourea as sources of carbon, nitrogen, respectively. This N, S-CDs was composited with silver nanoparticles (AgNPs) to detect mercury ions (Hg²⁺) with reabsorption principle. The fluorescence intensity of the carbon dots was vanished by AgNPs due to the reabsorption effect due to overlap between emission spectrum of N, S-CDs and absorption spectrum of AgNPs, and it is recovered by the addition of Hg²⁺ due to formation Ag/Hg amalgam. As a result, composite of N, S-CDs-AgNPs can be used as a fluorescence "turn-on" probe for rapid and highly sensitive detection of Hg²⁺. The lowest limit of detection (LOD) of Hg²⁺ is 10 nM with linear detection in the range of 1 nM - 1.0 μM. This LOD is improved three-order of magnitude as compared to the N, S-CDs only with detection limit in 10 μM. This result proves that the composite of N, S–CDs-AgNPs is a very sensitive fluorescence probe for mercury ions detection. This work will also provide ideas for creating and building novel fluorescence probes for similar applications.

The corrosion behaviour of two cobalt-based coatings (ULTIMET™ and STELLITE™ 6) with zero, 0.3 and 0.6 wt% ruthenium were studied and compared with two cobalt-based bulk alloys (ULTIMET™ and STELLITE™ 6B) in synthetic mine water (pH values of 6, 3 and 1) using potentiodynamic polarisation. The coatings demonstrated wider ranges of passivation behaviour (from −250 mV to 750 mV) than the bulk alloys. The corrosion potential became more positive and the active-passive transition reduced with increased Ru. The best coating was STELLITE™ 6 with 0.6 wt% Ru, which exhibited the lowest corrosion rates: 3.6 μm/y at pH 6 and 6.4 μm/y at pH 3.

The realization of a circular economy calls for maximum utilization of existing resources with no recoverable waste after the process cycle. During fast pyrolysis of biomass to produce bio-oil for energy purposes, solid residues in form of bio-char are generated. In this study, residual char after pyrolytic-oil extraction from rice husks was activated using steam at 800 °C to produce activated carbon (AC). The formed AC was characterized and evaluated for removal of heavy metals from contaminated water. Box Behnken Design of Response Surface Methodology was used to optimize the removal of Cu²⁺, Co²⁺, Zn²⁺, Pb²⁺, and Ni²⁺ from water. The process conditions were: adsorbent dose (2–12 g/L), contact time (30–180 min) and temperature (25–70 °C). Characterization of AC revealed surface area and pore volume of 407 m²g^-1 and 0.22 m³g^-1, respectively. For all developed models, adsorbent dose, and contact time were the most significant terms. A linear model best fits Cu²⁺ remediation, while quadratic models best-fit removals of Co²⁺, Zn²⁺, Pb²⁺, and Ni ²⁺. Heavy metal removal efficiency increased with increasing adsorbent dose, contact time and temperature. Optimum treatment parameters were: adsorbent dose (11.90 g/L), contact time (172.5 min), temperature (54 °C) with removal efficiencies of 98.2%, 84.1%, 75.3%, 98.1%, 75.7% for Cu^2+, Co²⁺, Zn²⁺, Pb²⁺, and Ni²⁺, respectively. Adsorption data best fitted Langmuir isotherm and pseudo second order models. These results confirm the applicability of AC from pyrolytic-oil residual char for adsorption of heavy metals. Use of AC from residual char in water treatment contributes to circular economy.

Additively manufactured sheet networks with low relative density show significant load-bearing capabilities while fulfilling additional requirements such as conducting gases. Introducing sheet networks as a core structure in sandwich panels requires fastening points for panel installation. This study develops, manufactures and mechanically investigates fastening points for triply periodic minimal surface sheet networks. While two concepts for Gyroid sheet networks are derived from an existing Honeycomb concept, a third concept improves the load-to-weight ratio by functionally grading the Gyroid's relative density. Pull-out tests were conducted to compare the performance of the insert concepts integrated into the Honeycomb and Gyroid sandwich specimens. The tests showed that only the functionally graded Gyroid concept reaches a significantly higher load-to-weight ratio than the Honeycomb concept, suggesting that its modified structure is effective. A numerical comparison of the Honeycomb's and Gyroid's unit cells shows equal moments of area for equal relative densities, thereby underlining the same load-bearing capabilities for similar insert concepts. In contrast to the Honeycomb fastening points, the Gyroid fastening points show a significant load-bearing capacity after the initial failure, which results in a residual load-bearing capability and, therefore, increased system robustness.

The corrosion inhibition performance of ornidazole was investigated as an eco-friendly option during the acid cleaning of carbon steel using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in combination with density functional theory (DFT) simulations. The inhibition efficiency was noted to rise with a rise in ornidazole concentration and exposure time. The maximum inhibition efficiency after 0, 1 and 7 days were attained at 1.6 g/L with values of 93.8, 96.2 and 98.7 %, respectively. Potentiodynamic polarization revealed that indazole is a mixed-type corrosion inhibitor. EIS indicates and increase in corrosion resistance with ornidazole concentration. SEM/EDX were consistent with the electrochemical results and indicate that ornidazole inhibits steel corrosion by surface adsorption which was consistent with Langmuir adsorption isotherm (R² = 0.9999). The values of K_ads indicate that ornidazole is more strongly adsorbed with an increase in concentration of ornidazole. The values of ΔGads (−5.69 to −11.75 kJ/mol) indicate that the adsorption is spontaneous. The inhibitory properties were found to be related to the molecular properties indicated by theoretical insights from DFT simulations which revealed susceptible adsorption sites on the ornidazole molecules from the deduced quantum descriptors, natural population analysis, density of states and molecular electrostatic potential. The results herein indicate that ornidazole is a suitable corrosion retardant for carbon steel in acidic environments.

The stress-free misfit strain obtained from simulation, neglecting the constraint from the matrix phase, serves as the inhomogeneity eigenstrain. On the other hand, the experimentally measured misfit strain under the constraint of the matrix phase serves as the constrained strain. This study demonstrates two ways to calculate the equivalent eigenstrain for precipitates through Eshelby inclusion theory: the inhomogeneity eigenstrain way (IEW) and the constrained strain way (CSW).

Novel High Entropy Alloy (HEA) coatings in the Al0.1-0.5CoCrCuFeNi and MnCoCrCuFeNi multi-materials systems on Mg substrate were prepared from mechanical alloyed HEA powder feedstocks and by three different Cold Spray (CS) process gas (N2) temperatures (650, 750 and 850 °C). Macro and microstructural characterization of mechanically alloyed and cold sprayed HEA coatings were carried out by macro photography, OM, SEM + EDS study, micro-hardness testing, roughness, and porosity measurements.

Mechanical alloying (MA) caused plastic deformation and fracture in harder particles. Relatively soft and ductile A1 phase and Cu-rich region particles were coarser and globular in shape. Some separate Cu-rich regions were also observed apart from A1 particles. Mn-HEA powder showed a different trend with finer particle sizes due to the more brittle nature of the powder and acicular shape. During MA, a loose structure with lots of gaps, cracks, plastic deformation signs, and small particles adhering to the particle surface is generated.

Based on the experimental data obtained, it cannot be concluded that the chemical composition of the high entropy alloy influences the roughness of the coating. The deposited volume increases with temperature only for Al_0.1 and Mg-based HEA, while for the other Al-based HEA no noticeable influences can be observed. The micro-hardness of a coating depends significantly on its chemical composition: as the percentage of aluminum increases in the samples micro-hardness increases. The hardness of the coating is significantly higher than that of the substrate, and the hardness measured at the interface is intermediate between the two values.

This study offers an idea of investigating the temperature and humidity effect on salt crystallization in burned clay brick when it is subjected to a saline environment. It has been investigated that salt may be carried into masonry pores structures by moisture. As moisture production and movement are affected by temperature and humidity, the mechanism of salt crystallization is affected as well. Uniaxial Salt crystallization in burned clay bricks at different temperatures (20 °C, 30 °C, and 40 °C) and humidity (70%, 80%, and 90%) has been investigated, considering all other parameters to be constant. Analyzing the data derived from the experiment, two equations have been developed (one for temperature effect analysis and another for humidity effect analysis). Results indicate that the salt crystallization in burned clay bricks increases when the temperature of samples and sodium sulfate (Na₂SO₄) solution increases. However, the salt crystallization in burned clay bricks goes down when the relative humidity of the surrounding environment of samples decreases.