Degree Of Lattice Distortion Research Articles

Neuroevolution machine learning potential to study high temperature deformation of entropy-stabilized oxide MgNiCoCuZnO5

Entropy stabilized oxide of MgNiCoCuZnO5, also known as J14, is a material of active research interest due to a high degree of lattice distortion and tunability. Lattice distortion in J14 plays a crucial role in understanding the elastic constants and lattice thermal conductivity within the single-phase crystal. In this work, a neuroevolution machine learning potential (NEP) is developed for J14, and its accuracy has been compared to density functional theory calculations. The training errors for energy, force, and virial are 5.60 meV/atom, 97.90 meV/Å, and 45.67 meV/atom, respectively. Employing NEP potential, lattice distortion, and elastic constants is studied up to 900 K. In agreement with experimental findings, this study shows that the average lattice distortion of oxygen atoms is relatively higher than that of all transition metals in entropy-stabilized oxide. The observed distortion saturation in the J14 arises from the competing effects of minimum site distortion, which increases with increasing temperature due to enhanced thermal vibrations, and maximum site distortion, which decreases with increasing temperature. Furthermore, a series of molecular dynamics simulations up to 900 K are performed to study the stress–strain behavior. The elastic constants, bulk modulus, and ultimate tensile strength obtained from these simulations indicate a linear decrease in these properties with temperature, as J14 becomes softer owing to thermal effects. Finally, to gain some insight into thermal transport in these materials, with the so-developed NEP potential, and using non-equilibrium molecular dynamics simulations, we study the lattice thermal conductivity (κ) of the ternary compound MgNiO2 as a function of temperature. It is found that κ decreases from 4.25 W m−1 K−1 at room temperature to 3.5 W m−1 K−1 at 900 K. This suppression is attributed to the stronger scattering of low-frequency modes at higher temperatures.

Microstructure and wear resistance of laser cladding AlCoCrFeNiSiB high-entropy alloy with high boron content

In this study, a wear-resistant coating of high boron content Al1.5CoCr2Fe1.5NiSi0.5B2 high-entropy alloy (HEA) was prepared on X65 pipeline steel by laser cladding. The coating underwent microhardness testing, wear performance testing, and analyses including scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The results revealed a dual-phase structure of body-centered cube (BCC) and face-entered cube (FCC) in the coating, with the presence of Fe1.1Cr0.9B0.9 phase distributed within the BCC. Utilizing high-resolution transmission electron microscopy (HRTEM) characterization, irregular atomic arrangement regions within the BCC structure were observed. Through the calculation of the α2 and ε parameters of the coating, the degree of lattice distortion in the BCC and FCC phases was quantitatively described. The results suggested that the addition of a substantial amount of boron could strengthen the lattice distortion effect, leading to improved hardness and wear resistance of the coating. The average microhardness of the coating was 912 HV, about 5 times higher than X65 substrate, improved by more than 10 % compared with other AlCoCrFeNi-based high-entropy alloys and B-containing high-entropy alloys. The wear rate was 4.78 × 10−6 mm/N·m, wear performance is nearly 10 times higher than other AlCoCrFeNi HEA without boron, 2 times higher than HEA with born. The wear mechanism of the coating was identified as abrasive and oxidative wear.

Synthesis, characterization, and double shielding performance for ultraviolet and short-wave blue light of ceria-based materials

In order to extend the photo-shielding range of ceria from the ultraviolet (UV) region (≤400 nm) to the high-energy short-wave blue light (BL) region (400–450 nm), three groups of ceria-based materials, including ceria nanoparticles (nano-CeO2), cerium-oxygen-sulfur (Ce-O-S) composites and samarium-cerium-oxygen-sulfur (Sm-Ce-O-S) composites, were prepared from the perspectives of improving the preparation method, non-metal doping and metal/non-metal co-doping. Although the three groups of as-prepared samples have similar phase composition, morphology and pore structure, the Sm-Ce-O-S composites show remarkable double shielding performance for UV light and short-wave BL. Compared with nano-CeO2 and Ce-O-S composites, Sm-Ce-O-S composites that retains the characteristics of n-type semiconductor exhibits a greater degree of lattice distortion, higher concentrations of Ce3+ (41.17 %) and oxygen vacancy (77.29 %), and narrower band gap (2.71 eV). Through the comparison of the three groups of samples, the order of modification degree from high to low is as follows: metal/non-metal co-doping > non-metal doping > improving the preparation method. This paper provides experimental and theoretical support for breaking through the bottleneck of ceria in the fields of UV shielding agents and catalysts.

Lattice distortion and strain induced crack formation in Y-doped BaZrO3

Proton conducting ceramics are promising solid electrolytes for protonic ceramic fuel cells. However, the presence of cracks remains a challenge before successful commercialization of the proton ceramic devices. This study investigates the impact of internal strain and lattice distortion on the crack formation in BaZr0.8Y0.2O3-δ. During sintering, pellets are covered with controlled amount of sacrificial powder 2 or 3 times of the pellet mass, and the effects of adding BaCO3 in the sacrificial powder is studied. The pellets sintered with 2 times sacrificial powder remain intact when dried, yet 53 % show cracks after hydration in 0.03 atm water vapor pressure. All pellets fracture into pieces when sintered with additional BaCO3 in sacrificial powder, in which 0.07 mol% excessive Ba is observed in the actual composition. These Ba excess pellets show larger lattice constant compared to those prepared under other conditions. Strain analysis indicates that 0.14 % to 0.15 % micro strain is observed in the batches with cracks. Raman spectra reveal higher degree of lattice distortion in the BO6 octahedra in the cracked batches. The findings highlight the role of lattice distortion in internal strain, and crack formation. This work may contribute to the processing of solid electrolytes in protonic ceramic fuel cells.

Probing the thermophysical property mechanism of Mg2+-doped high-entropy oxide ceramics

To create thermal barrier coatings (TBCs) with superior thermal characteristics and high-temperature stability, understanding the microscopic process of heat transfer in high-entropy solid solutions is crucial. In this study, novel (Zr0.2(1-x)Ce0.2(1-x)Pr0.2(1-x)Y0.2(1-x)Ho0.2(1-x)Mgx)O2-δ single-phase high-entropy fluorite-structured oxides with varying Mg elemental contents were successfully synthesized at 1600 °C. Given the unique ionic radius and valence nature of Mg2+, the effects of varying the Mg doping amount on the thermophysical properties and microstructures were explored. Furthermore, the mechanism influencing high-temperature thermal conductivity was studied at the microscopic scale using first-principles calculations to clarify the nature of the thermal conductivity behavior. On one hand, an increase in oxygen vacancies leads to an enhancement of the lattice distortion degree and phonon scattering level. On the other hand, divalent Mg2+ activates the lattice via unequal substitutions, thereby reducing the thermal conductivity. The experimental and simulation results revealed that as Mg doping increases, the content of oxygen vacancies significantly increases, the degree of lattice distortion increases, phonon scattering is enhanced (19.54–21.37 THz), high-temperature thermal conductivity progressively decreases (1.91-1.20 w·m−1·K−1), and the coefficient of thermal expansion progressively increases (11.70 × 10−6-12.31 × 10−6 K−1). These results offer a novel approach for designing doped high-entropy strategies that can satisfy the performance requirements of TBCs.

Investigation of phase separation mechanism in AlCoCrFeMo0.05Ni2 high-entropy alloy by first-principles calculations

AlCoCrFeMo0.05Ni2 high-entropy alloy (HEA) has great potential for high-temperature applications. However, its FCC matrix will decompose during annealing, which seriously limits its high-temperature applications. Here, the lattice distortion, Gibbs free energy change, phonon spectra, density of states, and bond length distribution of the FCC matrix were calculated by first-principles calculations. The findings indicate that the primary barrier to the formation of a single homogeneous solid solution in the alloy is more closely associated with Gibbs free energy rather than the degree of lattice distortion. The vibration frequency of Al is not in sync with the overall structure, making it prone to desolvation at elevated temperatures. Furthermore, an analysis of bond lengths reveals that the Al–Ni bond length is significantly shorter than the theoretical value, facilitating the formation of a (Ni, Al)-rich phase. In contrast, the longer bond lengths of Al–Cr and Al–Mo facilitate the detachment of Cr and Mo from the (Ni, Al)-rich phase, resulting in the formation of (Cr, Mo)-rich phase. This in-depth investigation sheds light on the phase decomposition mechanism of high-entropy alloys, offering valuable insights for future research in this field.

Lattice distortion dependent physical and mechanical properties of VCoNi multi-principal element alloys

Multi-principal element alloys (MPEAs) have garnered widespread recognition owing to their remarkable mechanical properties. Among alloying elements, the vanadium (V) element exhibits unique characteristics and has a high strengthening effect in the face-centered cubic Co-Ni-V MPEAs family owing to its large atomic radius. Here, first-principle calculations are utilized to examine the physical and mechanical characteristics of extensively researched VCoNi MPEAs. The objectives of this work are to give guidance on the design of MPEAs with desirable capabilities and fresh insight for understanding the role of lattice distortion described by atomic size difference on lattice parameters, binding energy, generalized stacking-fault energy, elastic properties, and electronic properties. A high degree of lattice distortion can lead to an increase in lattice constants, a more stable structure, and enhanced plasticity. These trends are attributed to a shortened pseudo-energy gap, large variations in charge density difference, and compact band overlap with increasing lattice distortion. The above results aim to serve as a point of reference for exploring the physical and mechanical attributes of MPEAs.

Phonon Properties and Lattice Dynamics of Two- and Tri-Layered Lead Iodide Perovskites Comprising Butylammonium and Methylammonium Cations-Temperature-Dependent Raman Studies.

Hybrid lead iodide perovskites are promising photovoltaic and light-emitting materials. Extant literature data on the key optoelectronic and luminescent properties of hybrid perovskites indicate that these properties are affected by electron-phonon coupling, the dynamics of the organic cations, and the degree of lattice distortion. We report temperature-dependent Raman studies of BA2MAPb2I7 and BA2MA2Pb3I10 (BA = butylammonium; MA = methylammonium), which undergo two structural phase transitions. Raman data obtained in broad temperature (360-80 K) and wavenumber (1800-10 cm-1) ranges show that ordering of BA+ cations triggers the higher temperature phase transition, whereas freezing of MA+ dynamics occurs below 200 K, leading to the onset of the low-temperature phase transition. This ordering is associated with significant deformation of the inorganic sublattice, as evidenced by changes observed in the lattice mode region. Our results show, therefore, that Raman spectroscopy is a very valuable tool for monitoring the separate dynamics of different organic cations in perovskites, comprising "perovskitizer" and interlayer cations.

Microstructure, mechanical, and thermal properties of (MoTaTiVW)CX high entropy ceramics with different carbon stoichiometries

In present work, high entropy (MoTaTiVW)CX ceramics with different carbon stoichiometries (X = 3–6) were produced using spark plasma sintering. The microstructure, mechanical properties, and thermal properties of (MoTaTiVW)CX with different carbon stoichiometries were studied. At X = 3, the carbon deficiency resulted in a multiphase structure of the sample, (MoTaTiVW)C3 with a Mo-rich carbide phase. At X = 3.5, the single-phase rock salt structure was formed despite carbon vacancies of up to 30 %. The relative density of (MoTaTiVW)CX gradually decreases as the carbon stoichiometry increases from X = 3 to X = 6. The concentration of carbon vacancies affects the sintering activation energy, which can enhance mass transfer and promote the densification process. The Vickers hardness of (MoTaTiVW)CX shows an overall decreasing trend as the carbon stoichiometry increases from X = 3.5 to X = 6, peaking at 20.4 ± 0.4 GPa at X = 3.5. The fracture toughness increases and then decreases, peaking at 4.4 ± 0.2 MPa m1/2 at X = 4. The thermal conductivity of (MoTaTiVW)CX gradually increases, then decreases and finally increases with the increase of carbon stoichiometry. At room temperature, the maximum value of thermal conductivity is 6.35 ± 0.29 W/m·K of (MoTaTiVW)C5 and the minimum value is 5.32 ± 0.35 W/m·K of (MoTaTiVW)C5.5. At 1000 °C, the thermal conductivity of (MoTaTiVW)CX ranges from 15.94 ± 0.37 W/m·K to 19.56 ± 0.45 W/m·K. As the concentration of carbon vacancies decreases, the decrease in point defect concentration will reduce the degree of lattice distortion, thereby reducing phonon scattering and affecting thermal conductivity. The study suggests that carbon stoichiometry can be used to adjust the microstructure, mechanical properties, and thermal properties of high entropy carbide ceramics.

Effects of deoxidation methods on the inclusion characteristics and corrosion behaviour of high-strength low-alloy steels in marine environments

The effects of deoxidation methods on the inclusion characteristics and corrosion behaviour of high-strength low-alloy steels were examined in marine environments using various microcharacterisation techniques and first-principles calculations. After Ca treatment, MnS–MgO–Al2O3 inclusions were modified to CaS–MgO–Al2O3 and microcrevices were existed at the interface between inclusions and Fe. After Zr–Ti-RE deoxidation, spherical CaS + TiN + ZrO2+MgAl2O4+(Ca, La) Al3O7 inclusions appeared. (Ca, La)Al3O7 in steel displayed similar mechanical properties to Fe, reducing the degree of lattice distortion and the formation of microcrevices around the inclusions. Micro-galvanic corrosion between Fe and MnS accelerated the localised corrosion rate and promoted the formation of large pits on the surface. However, the chemical activity of CaS resulted in dissolution of the inclusion, which relatively inhibited the localised corrosion propagation. The enrichment of Cr in the rust layer after Zr–Ti-RE deoxidation improved the compactness, contributed to a reduction in the localised corrosion rate and long-term corrosion rate. Finally, the underlying mechanism influencing corrosion behaviour was established.

Lattice distortion effects induced by Li+ co-doping on ZnO:Tb3+ phosphors: Photoluminescence and unusual hypersensitive ⁵D₄ → ⁷F₀ transition

A series of Tb3+, Li+ co-doped ZnO phosphors were prepared using a precipitation method. X-ray diffraction (XRD) analysis indicated the successful incorporation of Tb3+ into the ZnO lattice. The influence of Tb3+ doping content and Li+ charge compensator on the photoluminescence (PL) properties of ZnO:Tb3+ was investigated. Under UV excitation, emissions corresponding to electron transitions 5D4→7FJ (J = 0,1,2,3,4,5,6) were observed from Tb3+ ions, including an unusual emission transition at 673 nm, which significantly enriches our understanding of Tb3+ luminescence. The critical concentration quenching of Tb3+ in ZnO:Tb3+ occurs at 7 mol%, as explained by the Van Uitert equation, which attributes this phenomenon to dipole-dipole interactions. Surprisingly, incorporating Li+ for charge balancing led to a reduction in the luminescence intensity of ZnO:7 mol%Tb3+, x%Li+ phosphors (x = 0.01 and 0.07) at 544 nm. This reduction highlights an increased degree of lattice distortion due to Li⁺ inclusion. Furthermore, CIE chromaticity analysis showed that the optimal doping concentration of 0.07 Tb³⁺ shifted the color coordinates towards vivid green, with a color temperature of approximately 6241 K, indicating of neutral white light.

Microstructure, mechanical properties and wear resistance of TiNbCrMo[formula omitted] refractory multi-principal element alloys

The advancement of refractory multi-principal element alloys, exhibiting superior mechanical properties and wear resistance, is of paramount importance in materials engineering. This study introduces a novel series of refractory multi-principal element alloys, designated as TiNbCrMox (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0), and methodically explores the impact of varying molybdenum (Mo) content on their microstructural characteristics, phase composition, mechanical performance, and wear resistance. Empirical analyses reveal that these alloys are primarily composed of body-centered cubic (BCC) and Laves phases. The yield strength at ambient temperature is observed to span a range from 1572.8 MPa to 1902.5 MPa. Notably, the strategic addition of Mo in controlled proportions has been found to significantly enhance the hardness and ductility of the TiNbCrMox alloys. This improvement is attributed to the modification in the Laves phase concentration and the degree of lattice distortion. Moreover, the study identifies a marked increase in the hardness of the alloys, which, in conjunction with the formation of a lubricative oxide film, substantially reduces their wear rate. Specifically, the TiNbCrMo0.6 variant demonstrates a notably low wear rate, measured at 9.05 × 10−5 mm3/(N m). This investigation offers invaluable insights into the design and development of high-strength, wear-resistant metallic materials, highlighting their potential for diverse industrial applications.

Effects of Mo content on the microstructure and mechanical properties of laser cladded FeCoCrNiMox (x = 0.2, 0.5) high-entropy alloy coatings

The laser cladding additive manufacturing technology and high-entropy alloys can serve as ideal techniques and materials for the surface repair of high-speed train axles. Coatings of FeCoCrNiMox (x = 0.2, 0.5) were prepared on EA4T axle steel using laser cladding technology, and their phase, structure, and mechanical properties were analyzed using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) characterization techniques. Additionally, the mechanical properties of the coatings were tested, and first-principles calculations were used to verify and calculate the material's mechanical performance. The research findings indicate that an increase in Mo content leads to a greater degree of lattice distortion, causing a leftward shift in diffraction peak positions. Significant differences in the microstructure from the substrate to the coating surface were observed, with columnar grain structure at the bottom of the cladding layer and equiaxed dendrites dominating the coating surface. The increase in Mo content promotes the formation of σ phase while also refining the grain size. ECCI results show that both types of coatings consist of a high-density dislocation cell structure and Mo-rich particles. With an increase in Mo content, the peak hardness of the coating increased from 456.5 HV to 469.4 HV, while the impact energy decreased from 56 J to 16 J, attributed to the increase in dislocation density and the greater quantity of σ phase. First principles calculations verified that the comprehensive mechanical properties of FeCoCrNiMo0.2 are superior, providing theoretical guidance for the optimization and design of the coatings.

Effects of manganese doping on the lattice structure and iron ion states in La2/3Ca1/3Fe1-xMnxO3-δ

In this paper, La2/3Ca1/3Fe1-xMnxO3-δ(x = 0–0.6) nano particles have been prepared by the sol-gel method. X-ray diffraction (XRD) analysis revealed that with the increase of Mn doping content, the main diffraction peak shifted to the right, the lattice parameters decreased overall, and the degree of lattice distortion gradually reduced. X-ray photoelectron spectroscopy (XPS) analysis indicates that the valence states of Fe and Mn in the system coexist as trivalent and tetravalent, and with the increase in Mn doping, the ratio of Fe3+/Fe4+ decreases, while the ratio of Mn3+/Mn4+ slightly increases. The results of Mössbauer spectrum analysis revealed that as the Mn doping content increased, some Fe ion valence states in the system gradually changed from Fe3+ to Fe4+, and the presence of the paramagnetic phase became increasingly prominent. Furthermore, with the increase of Mn doping content, the degree of lattice distortion in the system decreased, which is consistent with the results obtained from the XRD analysis. This work will provide a reference for future research on the effects of manganese doping in similar systems.

Effect of Aging Time on Microstructure and Properties of Cold-Rolled Ni-W-Co-Ta Medium–Heavy Alloy

A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation (Ni4W), which persists under various aging times, increases from 13.7% (2 h) to 28.7% (32 h) with the extension of aging time. Meanwhile, the microstructure after aging treatment is still dominated by dislocation entanglement and dislocation walls, although the degree of lattice distortion and dislocation density attributed to heavy deformation decreases. The maximum tensile strength, yield strength, and microhardness (2286 MPa, 1989 MPa, 766 HV) of the cold-rolled Ni-W-Co-Ta medium–heavy alloy under the 16 h aging treatment at 700 °C are reached, respectively. The ductile–brittle mixed fracture morphology is maintained in the fracture morphology of the medium–heavy alloy before and after aging treatment.

A Ce/hopcalite catalyst for low-temperature oxidation of CO:Preparation, performance and mechanism

The utilization of atomic-scale doping in catalysts has been recognized as an effective strategy for enhancing CO oxidation catalytic activity. This work adjusted the lattice structure of hopcalite (CuMnOx) catalysts via Ce-doping. Ce species was uniformly dispersed on the surface of amorphous porous catalysts, which built abundant interfaces along with many active sites. The lattice distortion degree can be regulated by changing Ce dosage. The modified catalysts with 7.5 wt%Ce-doping exhibited the optimal intrinsic activity for CO oxidation. Compared with the original sample, the CO conversion increased by 50 % at room temperature, and the reaction rate was eight-fold faster, superior to most reported hopcalite catalysts. Integrating with the various characterizations, the enhancing of low-temperature activity mainly originates from the weakened binding of oxygen atoms by lattice distortions. Moreover, the experiments and characterization results revealed that the reactivity of both adsorbed and lattice oxygen is enhanced on Ce-modified samples at low temperature. This work provides new insights into the rational modulation of reactive oxygen species and reinforces the utility of hopcalite catalysts for oxidizing CO at low temperature.

Tailoring the performances of Ti-V-Al base shape memory alloys by defects engineering

In the present study, various defects such as dislocations were controlled in Ti-V-Al-based shape memory alloy by thermomechanical treatment and introduction of interstitial oxygen (O) atom to optimize the performances. The results revealed that the Ti-V-Al-O shape memory alloys gradually evolved from α” martensite phase to the β parent phase with increasing annealing temperature. Moreover, the degree of lattice distortion can be tailored by changing annealing temperatures. Upon the annealing temperature reached 900 °C, masses of ω precipitates and a nano-sized ordered domain, characteristic of strain glass, can be found. As a result of suppression effect of multiple varieties of defects to the martensitic transformation, no obvious endothermic and exothermic peaks were observed in differential scanning calorimetry curves. The yield strength and maximum tensile fracture strength of the Ti-V-Al-O shape memory alloy increased with the increase of annealing temperatures. Meanwhile, Ti-V-Al-O shape memory alloys annealed at 900 °C possessed superior strain recovery characteristics and corrosion resistance. The excellent performances in Ti-V-Al-O shape memory alloys annealed at 900 °C can be attributed to the formation nanoscale nanodomain.

Elinvar-Like Effect Induced by High Lattice Distortion in Zr 6 Ta 2 O 17 Ceramics

Super strength and toughness, excellent deformation resistance, and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings (TBCs). The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength–plasticity and the reduction of service performance. Introducing preexisting twin boundaries and stacking faults (SFs) or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics. However, due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature, the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs. In this paper, the deformation behavior of high configuration entropy Zr 6 Ta 2 O 17 ceramics at 25 to 1,200 °C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment. A remarkable Elinvar-like effect appears in the Zr 6 Ta 2 O 17 ceramic. More interestingly, mechanical deformation dominates the severe lattice distortion (deformation twins, SFs) and the disorder–order transition of chemical order at the atomic scale, while temperature can further enhance the degree of lattice distortion and ordering of Zr 6 Ta 2 O 17 ceramics. Furthermore, the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr 6 Ta 2 O 17 ceramics.

Efficient 1O2 production from H2O2 over lattice distortion controlled spinel ferrites

Iron-based materials are difficult to produce single oxygen (1O2) efficiently from H2O2. Herein, we demonstrate that 1O2 production from H2O2 can be manipulated by regulating the lattice distortion degrees of spinel ferrite through controlling the contents of Co and Ni in Co1−xNixFe2O4. Typically, NiFe2O4, which owns the lowest lattice distortion degree, can produce 1O2 as the dominated reactive oxygen species with·O2- as the intermediate. Due to the production of 1O2, the NiFe2O4/H2O2 system removes bisphenol A (BPA) completely within 180 min but removes only ∼ 4% of benzoic acid. In addition, the system demonstrates significant resistance to water matrix interference, as 50 mM of Cl-, NO3-, H2PO4-, and humic acid inhibited the BPA degradation by only ∼0%, ∼2%, ∼40%, and ∼3%, respectively. Our work may shed light for regulating the formation of 1O2 from H2O2 through the rational design of iron-based catalysts for Fenton-like reactions.

Multilayer synergistic design of NbSi2/Nb2O5-SiO2/MoSi2 ceramic coating on niobium alloys for multiple thermal protection properties

A novel NbSi2/Nb2O5-SiO2/MoSi2 multilayer thermal protection ceramic coating is designed and fabricated via halide-activated pack cementation and liquid-plasma-assisted particle deposition and sintering technology, endowing the coating with multiple high-temperature protective properties. The incorporation of MoSi2 nanoparticles not only gives superior high-temperature oxidation resistance/hot corrosion resistance of coating by forming a dense SiO2 barrier layer, but also promotes passive radiative heat dissipation. When NbSi2/Nb2O5-SiO2/MoSi2 coating was prolonged exposure to air at 1250 °C for 50 h of oxidation and at 900 °C for 100 h of corrosion, the mass gains are only 0.37 mg/cm2 and − 0.52 mg/cm2, respectively. The multilayer coating exhibits enhanced emissivity (>0.88) over the thermal infrared range of 3–20 µm, due to the lattice vibrational absorption-matching synergy of Nb2O5, SiO2, and MoSi2, as well as the mutual doping of SiO2/Nb2O5, mismatch of atoms at the interface, and a high degree of lattice distortion within the coating.