Doped Powders Research Articles

A Versatile Route for Converting n-Type ZnO into p-Type: Phosphorus Doping of Nanostructures and Powders

A Versatile Route for Converting n-Type ZnO into p-Type: Phosphorus Doping of Nanostructures and Powders

Study on the hydration characteristics and mechanical properties of recycled powder-slag powder-cement system

This study systematically investigated the influence of different blending ratios of recycled powder and slag powder on hydration heat evolution and mechanical properties. Various modern microscopic testing techniques were employed to quantitatively characterize hydration products and microstructures, revealing their hydration mechanisms. The results indicate that both recycled powder and slag powder can accelerate the early hydration rate. When recycled powder and slag powder are co-blended, their early hydration rate and cumulative heat release surpass those of specimens with single additions of recycled powder. Moreover, the mechanical properties in the later stage are superior to those of specimens with single additions of recycled powder. At 60d, the PRS70–1–2 in the multi doped recycled powder and slag powder system even exceeds that of the uni doped SL system, but is much higher than that of the uni doped RP system，the compressive strength of the multi doped recycled powder and slag powder system increased by 25.5 %, 37.1 % and 36.9 %, respectively, compared with that of the uni doped RP system. Specimens with single additions of recycled powder and slag powder have a relatively high proportion of harmful and very harmful pores. At 28d, the porosity of the multi doped recycled powder and slag powder system decreased by 19.2 %, 24.2 % and 14.8 %, respectively, compared with that of the uni doped RP system. However, when recycled powder and slag powder are co-blended, the proportion of harmful and very harmful pores decreases, while the proportion of less harmful and harmless pores increases. This leads to an overall reduction in porosity and an improvement in mechanical properties.

Flexible Terahertz Broadband Absorber Based on a Copper Composite Film.

Terahertz absorbers play a crucial role in terahertz detectors, radar stealth, electromagnetic shielding, and other fields. However, the design and fabrication of flexible terahertz broadband absorbers remain a challenge at present. Here, we demonstrated a terahertz broadband absorber based on a copper composite film (CCF) consisting of a copper foam and an organic silica gel doped with Fe3O4 powder. The CCF can be fabricated by the infiltration method. The influence of the thickness and the pore size of the copper foam and the mass fraction of doped Fe3O4 powder on the absorption bandwidth were investigated. When the thickness of the CCF is 1.5 mm, the pore size of the copper foam is 95 pores per inch (ppi), and the mass fraction of Fe3O4 is 1%; a broadband absorption is achieved in the range of 0.11-3.5 THz. It is noted that the mass fraction of Fe3O4 has a significant impact on the absorption bandwidth. In addition, the thickness of the CCF and the pore size of the copper foam also have an impact on the absorption. The impedance matching theory is introduced to understand the mechanism of broadband absorption. This flexible broadband absorber has potential application in terahertz stealth, shielding, and the sixth-generation (6G) broadband wireless communication in the future.

Manganese doping in zinc based hybrid metal halides to realize highly stable efficient green emission and flexible radiation detection

Extensive studies have been conducted on hybrid metal halides due to their application in radiation detection, solid-state lighting, and solar cells. Here, we present an environmentally friendly zero-dimensional halide, (C9H15N3)ZnBr4, which crystallizes in the P21/c space group. This compound is highly thermally stable, and doping Mn2+ results in a bright green light emission, with an impressive internal quantum efficiency of 52.9 % and an external quantum efficiency of 45.9 % for (C9H15N3)Mn0.3Zn0.7Br4. Combining spectroscopic analysis with first-principles density functional theory (DFT), it is concluded that the high external quantum efficiency arises from efficient energy transfer from the organic component to the [MnBr4]2-. Notably, the (C9H15N3)Mn0.3Zn0.7Br4 luminescence intensity maintains 50 % of its room temperature level even at 400 K. Moreover, these doped powders display exceptional scintillation performance, higher than Bi4Ge3O12. Finally, the radioluminescence intensity of (C9H15N3)Mn0.3Zn0.7Br4@polydimethylsiloxane flexible films is about three times that of Bi4Ge3O12. These features position Mn:(C9H15N3)ZnBr4 as an ideal material for X-ray detection and an efficient green photoluminescent material.

W–CeO2 Core–Shell Powders and Macroscopic Migration of the Shell via Viscous Flow during the Initial Sintering Stage

To retard the mutual contact of W grains to inhibit their growth, in this study, CeO2·2H2O was first coated on the surface of pure W (undoped) particles by a weight percentage of 4% using a wet chemical method to prepare CeO2·2H2O-doped W-based (doped) powders, with W particles as the core and CeO2·2H2O as the shell (W–CeO2·2H2O core–shell structure), without hydrogen reduction treatment. The undoped and doped powders were subsequently sintered using a spark plasma sintering (SPS) apparatus to fabricate bulk materials. The macroscopic migration of the CeO2 shell in the core–shell W–CeO2 system via viscous flow during the initial sintering stage was studied through simulations and experiments. The results showed that a core–shell structure with W particles as the core and CeO2·2H2O as the shell was successfully prepared. The doped powder contained approximately 3.97% CeO2, consistent with the designed content of 4%. The shell materials migrated among the selected four sintered powders, filling the pores and contributing to the improvement in the relative density of the sintered bulk.

Direct mechanochemical synthesis of CaMoO4 and Dy3+ doped CaMoO4 nanoparticles and their photoluminescent properties

Calcium molybdate (CaMoO4) and Dy3+ doped CaMoO4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO4 and Dy3+ doped CaMoO4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO4 samples contain absorption peaks corresponding to the MoO4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO4 and Dy3+ doped CaMoO4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F9/2 → 6H11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO4 nanoparticles can find application in different optical instruments.

Investigating the Effect of Carbonyl Iron Powder Doping on the Microstructure and Magnetic Properties of Soft Magnetic Composites

This study proposes the thermal decomposition of salt compounds and doping of carbonyl iron powders (CIPs) to optimize the preparation of an insulating layer through the solid-phase interface reaction. First, (Fe–Si–Cr + CIPs)/ZnSO4 composite powders were synthesized using the hydrothermal method and (Fe–Si–Cr + CIPs)/ZnO·SiO2·Cr2O3 SMCs with a ZnO·SiO2·Cr2O3 composite insulation layer were prepared through heat treatment and cold pressing. The effect of the CIP doping content on the microstructure and magnetic properties of the (Fe–Si–Cr + CIPs)/ZnO·SiO2·Cr2O3 SMCs were then investigated. During the heat treatment, ZnSO4 decomposed into solid ZnO and gaseous SO2 and O2. The O2 drives the solid-phase reaction, prompting the migration of nonmagnetic Si and Cr atoms from the interior of the Fe–Si–Cr soft magnetic powder to the surface insulation layer, finally forming the ZnO·SiO2·Cr2O3 insulation layer. The doped CIPs also show good plasticity during the coating process, combining with the coating layer to fill the internal pores of SMCs. Moreover, as the particles are small with a high surface area, they increase the number of reaction sites for ZnSO4 decomposition and facilitate the growth of the composite insulation layer, promoting its uniform distribution on the surfaces of the soft magnetic powders and CIPs. The lattice mismatch between the insulation layer and soft magnetic powder is reduced while the magnetic-phase content is increased, allowing the effective doping of CIPs sin the insulation layer. The magnetic properties of SMCs can be precisely regulated by changing the doping amount of CIPs. Unlike other insulating layer–preparation strategies based on the interfacial solid-phase reaction, the proposed method exploits the high plasticity and specific surface area of CIPs and removes the lattice mismatch between the insulation layer and soft magnetic powder.

Microstructures and properties of Al2O3 dispersion-strengthened Cu10Sn oil bearings prepared by solid-liquid doping and reactive synthesis method

To modify the shortcomings of Cu10Sn oil bearing in mechanical performance, this work proposes to prepare the Al2O3 oxide dispersion strengthened (ODS) Cu10Sn oil bearings by reactive synthesis using elemental Sn and Al2O3 ODS-Cu powder, among which the uniformly doped Al2O3 ODS-Cu powder was synthesized through a solid-liquid doping of Al(NO3)3 in CuO powders followed with hydrogen reduction. The effects of Al2O3 content on the microstructure and properties of ODS-Cu powder and ODS-Cu10Sn oil bearings were investigated in details. The results showed that an increase in Al2O3 amount from 0 to 1.5 wt% leads to a decrease in the average particle size of the reduced ODS-Cu powders, and contributes to the significant improvement of radial compressive strength, and Vickers microhardness. The appropriate sintering temperature is approximately 800 °C, which can result in the evenly distributed Al2O3 and well-developed porosity in oil bearing sample after sintering. The corresponding compressive strength and microhardness of ODS1.5-Cu10Sn oil bearing can reach 305 MPa and 208 HV respectively.

Hot corrosion resistance of oxide‐doped yttria‐stabilized zirconia powder in V2O5 molten salt

AbstractThe hot corrosion resistance of 8 wt.% yttria‐stabilized zirconia (8YSZ) powder, modified with CaO, MgO, Ta2O5, and TiO2 at concentrations of 5, 10, and 15 wt.%, was systematically investigated in a molten vanadium pentoxide (V2O5) environment at 900°C and 1100°C for 48 h. The modified 8YSZ samples, coated with V2O5, underwent thermal cycling totaling 12 cycles. Results revealed susceptibility to hot corrosion for all doped 8YSZ powders, attributed to tetragonal ZrO2 destabilization, forming monoclinic ZrO2. Remarkably, 8YSZ/CaO demonstrated exceptional resistance to hot corrosion when exposed to a temperature of 900°C. The corrosion product found in the 8YSZ/Ta2O5 material was determined to be tetragonal Zr0.66Y0.17Ta0.17O2. Although, 8YSZ/TiO2 undergoes deterioration at 900°C, it exhibits improved resistance at 1100°C, resulting in the formation of TiVO4.

Structure and Ionic Conductivity of Ga and Nb Dual Doped LLZO Synthesized by Sol-Gel Method

More and more attention has been focused on Li7La3Zr2O12 (LLZO) because of the high ionic conductivity and excellent chemical stability. It is great significance to find suitable dopants for locking cubic LLZO and improving the conductivity of Li+ ions. The uniform nano powder can be obtained by the sol gel synthetic method, which is conducive to maintaining high sintering activity. In this work, Ga and Nb dual doped LLZO solid electrolyte powders were synthesized via sol gel method, and Ga and Nb dual doped LLZO solid electrolyte ceramic were obtained via traditional solid state sintering method. The phase and microstructure of Ga and Nb co-doped LLZO solid electrolyte were analyzed by combine X-ray diffraction with scanning electron microscope. The impedance of Ga and Nb dual doped LLZO (Li6.8-3xGaxLa3Zr1.8Nb0.2O12 (0≤x≤0.3)) solid electrolyte was measured by the electrochemical workstation, and then the conductivity was calculated. The results show that when the doping amount of Ga is x=0.2, it is a pure cubic LLZO structure with the highest conductivity value of 3.7×10-4 S cm-1 (tested at room temperature) due to the sample has a high relative density and reaches the optimal Li+ vacancy concentration.

A facile in‐situ fabrication of black polyimide films with ultrahigh electrical properties

AbstractConsidering the ongoing evolution of flexible printed circuit boards and the importance of safeguarding the intellectual property of circuit designs, there exists an imperative demand for the development of a black film exhibiting exceptional electrical properties and remarkable light‐shielding capabilities. Consequently, this work employs a straightforward strategy to enhance the opacity of polyimide films by incorporating carbon black (CB) and manganese dioxide (MnO2) as black fillers using an in situ doping method. Rigorous tests are conducted, analyzing properties such as dielectric constant, dielectric loss, breakdown field strength, current density, and ferroelectric energy storage. The optimal ratio of CB to MnO2 (mass fraction) is determined as 1:5, with a total powder doping amount of 6 wt%, providing the best ratio relative to the matrix resin. This ratio ensures an optimal powder dispersion state, resulting in an outstanding breakdown field of 147.4 kV/mm and ultralow dielectric constants, measuring less than 3.78 at 103 Hz. This composite film is anticipated to find applications as a cutting‐edge material for electronic devices and the semiconductor industry.

An efficient red light-emissive process from Eu3+ doped amorphous-derived CaAl2Si2O8 ceramic powders: Down-shifted luminescence with high thermal stability under 532 nm excitation

The present study reveals the luminescence performance of Eu3+ doped amorphous powders derived from calcium aluminum silicate (CaAl2Si2O8) ceramic host prepared by the combustion synthesis method assisted with urea as a fuel. The structure and phase development of the Eu3+ doped CaAlSiO material were investigated using XRD spectroscopy. The samples present an amorphous character after heat treatment at 800 °C and exhibit intense red fluorescence when stimulated by CW laser radiation at λ ∼532 nm. The excited samples displayed the emission peaks of Eu3+ corresponding to Eu3+: 5D0→7FJ (J = 0, 1, 2, 3, 4) optical transitions, with the red emission at 613 nm originating from the 5D0→7F2 transition being the most intense. Using the fluorescence intensity emissions derived from 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions, the optical intensity parameters Ωλ (λ = 2, 4) of the Eu3+ in the amorphous host were calculated. The refractive index n of the amorphous powders was also estimated in the framework of Judd-Ofelt theory. Finally, the temperature-dependent emission spectra of the CaAlSiO: (3.0 mol%)Eu3+ amorphous sample were collected in the range 298–573 K. By inspecting the fluorescence behavior of the red emission as a function of temperature, the considered phosphor was found to have high thermal stability, as evidenced by the luminous intensity maintained at around 99.2% at 423 K compared to the intensity at ambient temperature (298 K) with an activation energy of 0.34 eV. These results indicate that the Eu3+ doped CaAlSiO amorphous phase system can be potentially used for high-quality lighting applications. Finally, in order to assess the thermometric characteristics, the thermal sensing capabilities of the amorphous host have been evaluated, and the relative sensitivity, estimated by the peak-valley ratio method, was 0.23% K−1 at 298 K, validating the phosphor for temperature sensing purposes.

Synergistic Zinc(II) and Formate Doping of Perovskites: Thermal Phase Stabilization of α-FAPbI3 and Enhanced Photoluminescence Lifetime of FA0.8MA0.2PbI3 up to 3.7 µs.

Adding zinc (II) cations and formate anions improves the thermal phase stability of α-FAPbI3 materials, and the spin-coated thin films of such doped FAPbI3 (produced using MACl) show an increased emission lifetime of up to 3.7 μs on quartz (for FA0.8MA0.2PbI3). This work investigates the effects of zinc and formate on the phase stability and time-resolved photoluminescence of FAPbI3 perovskites for solar cell applications. Perovskite samples with varying concentrations of zinc and formate were made by incorporating different amounts of zinc formate and zinc iodide and were characterized with XRD. Doping levels of 1.7% Zn(II) and 1.0% formate (relative to Pb) seem optimal. The thermal phase stability of the doped perovskite powders (FAPbI3) and thin films (FA0.8MA0.2PbI3) was assessed. XRD of the thin films after 6 months shows only the alpha-phase. The time-resolved photoluminescence spectroscopy of the doped spin-coated perovskite samples (FA0.8MA0.2PbI3 produced using MACl) is reported. The results show that synergy between an anionic and a cationic dopant can take place, making the perovskite thermally more phase-stable (not converting to the yellow delta-phase) with a longer charge carrier lifetime. In order to produce good thin films by spin coating, the use of MACl was essential.

Influence of Ho spontaneous aggregation on the coercivity and magnetic domain movement of sintered NdY-Fe-B magnets

Development of NdY-Fe-B magnets not only reduces the cost of Nd-Fe-B type magnets but also promotes the balanced utilization of rare-earth resources. However, the lower coercivity of NdY-Fe-B magnets hinders their further development. This study investigated the coercivity of NdY-Fe-B magnets via intergranular doping of Ho76Al12Ga12 powders. Although this process improved the coercivity, the remanence substantially deteriorated with the increasing content of the Ho76Al12Ga12 alloy. A coercivity of 1.37 T was achieved in a NdY-Fe-B magnet with a Ho76Al12Ga12 alloy doping of 7 wt%, showing a coercivity increment (ΔHcj) of 0.64 T compared to the original magnet. This can be attributed to the observed microstructural and elemental distributions, as well as the analysis of the magnetic domain wall movement. An abnormal Ho-biased layer is observed between the Y-rich core and the Ho-rich shell in the matrix grains, exhibiting a higher anisotropy field compared than the shell layer. Further analysis revealed that the movement of magnetic domain wall movement was obstructed by the Ho-biased layer, demonstrating a domain-wall pinning effect within the matrix grains. Additionally, the formation of a Ho-rich shell in the outer area of the 2:14:1 matrix grain and the presence of a continuous uniform grain boundary phase were found to be important for improving both coercivity and thermal stability.

Enhancing infrared emissivity of GdCoO3 with Ca doping: Potential for advanced thermal control materials

The high infrared emissivity material Gd1-xCaxCoO3 was synthesized using the sol-gel method. The structure and composition of Gd1-xCaxCoO3 were investigated through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), specific surface area analysis, Brunauer-Emmett-Teller (BET) method for void analysis, and Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) diffuse reflection spectrum were employed to analyze the surface morphology, elemental composition, specific surface area, pore size distribution, and band gap of the prepared powders. The average infrared emissivity of samples with different doping concentrations at various temperatures (8-14 μm and 3-5 μm) was determined using a dual-band emissivity meter. At room temperature, the infrared emissivity of the doped powders is generally higher, exceeding 0.75 in comparison to the undoped sample powder. As the test temperature increases, the infrared emissivity of all samples shows a significant rise. The infrared emissivity of all samples surpasses 0.91 at 500 °C, with the emissivity of the samples reaching as high as 0.988-14μm (0.993-5μm) with a Ca doping concentration of 5 %. These findings indicate that Ca-doped GdCoO3 powder represents a promising high-emissivity material with broad potential in spacecraft thermal control applications.

Synthesis, photo- and thermo-luminescent properties of Mg2P2O7:Tm3+ phosphors

In this work, both undoped and Thulium (Tm3+) doped (0.3–10 mol%) magnesium pyrophosphate (Mg2P2O7) powders were synthesized by the solvent evaporation method to study their photo-and thermoluminescent properties. Two crystalline phases were observed in the powders by X-Ray diffraction (XRD), the main phase being Mg2P2O7 and the second one thulium phosphate (TmPO4). The superficial morphology was analyzed by scanning electron microscopy (SEM), which revealed that the powders are agglomerates with an undefined form and grains with non-uniform size distribution. The photoluminescence (PL) emission spectra of Tm3+ doped powders show the 1D2 → 3F4 transition, associated with Tm3+ ions, at 452 and 458 nm. The thermoluminescence (TL) properties were analyzed in the undoped and Tm3+ doped powders exposed to 90Sr beta source. The TL glow curve of Tm3+ doped powders exhibits three maxima at about ⁓64–66 °C, ⁓198–202 °C, and ⁓301 °C. The TL dose-response is sub-linear from 0.11 to 0.54 Gy, linear between 0.79 and 24.95 Gy, and supra-linear from 34.99 to 599.95 Gy. Acceptable repeatability with a coefficient of variation of ∼1% was obtained after ten cycles of irradiation and readout. At 63 d of storage, the powders show fading of 30%, and at 1.6 years (585 d), the integrated TL intensity decays by 47%. The kinetic parameters of activation energy and frequency factor were evaluated using the Initial Rise, Booth, Bohum, and Porfianovitch (BBP) and Hoogenstraaten methods and Glow Curve Deconvolution with a general order kinetic model.

Rapid photocatalytic degradation of organic pollutants by Al3+ doped CuO powders under low power visible light and natural sunlight

The photocatalytic degradation of organic pollutants is a promising approach to deal with dye industry wastes released into water bodies. However rapid, inexpensive, and low power visible light photocatalytic degradation of water pollutants is challenging. This study tries to address these constraints by using inexpensive doped CuO Powders under low-power visible household LED light. Also, direct illumination of sunlight to achieve better photocatalytic degradation, reducing device and operational costs. Further, photocatalytic degradation is enhanced by doping of Al3+ in CuO. Under several optimized conditions, rapid and almost complete degradation of three different dyes, Methylene Blue (MB), Rhodamine B (RhB), and Methyl Orange (MO) were achieved within 6 min of light irradiation under household LED and within 30 min of direct irradiation of sunlight. Even after five times of repeated use of the catalyst, no significant decrease in the photocatalytic activity was observed indicating its stability and sustainability.

Orange persistent luminescence of LuBaZn3GaO7: Bi3+ phosphor based on defect induction for optical thermometer and multi-mode anti-counterfeiting

In this study, the Bi3+ doped LuBaZn3GaO7 fluorescent powder was produced using a high-temperature solid-state technique, and its long afterglow luminescence and dynamic anti-counterfeiting capabilities were thoroughly examined. Under the ultraviolet (UV) light excitation, the LuBaZn3GaO7 host exhibits broadband self-activated emission band peak at 594 nm, attributed to the O-vacancies. Upon Bi3+ doping, the phosphor produces a narrow emission band in the 350–450 nm wavelength range, which is caused by the 3P1–1S0 transition of the Bi3+ ions in the Ba2+ site. Remarkably, oxygen vacancy-induced electronic localization around the Bi3+ ions increases the emission intensity of LuBaZn3GaO7:0.01Bi3+ around ten times that of LuBaZn3GaO7 between 450 and 850 nm wavelength. With the variation in excitation light wavelength, the intensity of the two emission bands of LuBaZn3GaO7: Bi3+ changed accordingly, exhibiting multi-color luminescence. While the excitation was removed after 3-min irradiation, LuBaZn3GaO7: Bi3+ phosphors continued to emit for 10 min. Moreover, the phosphor emission has good temperature-sensitive characteristics based on the fluorescence intensity ratio (FIR) of the emission bands of Bi3+ ions and host. Hence, an optical thermometry with high-temperature sensitivity was constructed. Consequently, it can be concluded that fluorescent powder has the potential to be applied in the fields of fluorescence temperature measurement and anti-counterfeiting.

Preparation of Ni–B composite coating doped with hydrothermally modified synthetic WC@MoS2 powders via ultrasonic-assisted jet electrodeposition for corrosion protection

This work aims to improve nanoparticle agglomeration, which hinders the application of nanoparticles in enhancing coating properties. Superhydrophobic and corrosion-resistant Ni–B– MoS2@WC composite coatings were prepared with the help of a simple and inexpensive combination of hydrothermal and electrodeposition techniques. Hydrothermal treatment at 180°C for 24h greatly reduced the specific surface area and improved the hydrophobicity of WC@MoS2 powder. The WC@MoS2 powder showed good dispersion stability in the electrolyte solution. Ni–B/WC@MoS2 composite coatings were prepared through codeposition with metallic Ni2+ under the action of ultrasonic waves. WC@MoS2 powder doping induced the coatings to exhibit a selective orientation of the (111) crystal plane. Ultrasound-induced cavitation increased the participation of nanopowders in the adsorption codeposition of Ni ions. After WC@MoS2 powder doping, the surface roughness of the prepared composite coatings furthered significantly, facilitating the wettability transition. This work investigated the relationship between the surface wettability of the coatings prepared via jet electrodeposition and WC@MoS2 powder doping under auxiliary ultrasonic power. In addition, the effect of surface hydrophobicity on corrosion resistance was examined through electrochemical corrosion tests. The enhanced corrosion resistance of the composite coatings benefits from their enhanced surface roughness and superhydrophobicity. This research offers a proven strategy for improving nanopowders' wettability and composite coatings' corrosion resistance.

Promoting the optical limiting behavior in poly(methyl methacrylate)/α-MnO2 nanocomposite films through modulation of in-gap states by metal doping

Nonlinear optical (NLO) materials are becoming increasingly popular due to their wide range of applications in sub-bandgap photoelectric detection, photonic diodes, Q-switched/mode-locked pulse laser production, optical limiting, and optical switching. In this study, bare and doped (Co, Cu) alpha manganese dioxide (α-MnO2)/poly (methyl methacrylate) (PMMA) nanocomposite films were fabricated to investigate the effect of the in-gap states modulation triggered nonlinear absorption (NA) mechanisms on optical limiting. The structural characterization of bare and doped powders proved the successful incorporation of dopant metals into the α-MnO2 lattice. Linear absorption measurements revealed that the nanocomposite films have two distinct bands at around 230 nm and above 400 nm attributed to PMMA and bare, Co and Cu doped α-MnO2 nanoparticles, respectively. While the localized defect states of PMMA decreased with the addition of the nanoparticles, the localized defect states of the α-MnO2 increased with Co and Cu dopants. To reveal the NA behaviors and mechanisms of the nanocomposite films, open aperture Z-scan experiments were performed at 532 nm with 4 ns pulsed laser at various input intensities. The saturable absorption effect on the NA behavior of the nanocomposite films was observed with increasing input intensity due to the filling of the defect states of the nanoparticles by one photon absorption (OPA). Considering the bandgap energies and localized defect states of the nanocomposite films, it was revealed that the PMMA/MnO2 and PMMA/MnO2:Co nanocomposite films had the same NA mechanisms which are OPA, sequential two photon absorption, free carrier absorption and excited state absorption (ESA). Among these NA mechanisms, the ESA between the conduction band of MnO2:Cu nanoparticles and localized defect states of PMMA did not occur due to inconvenient energy differences between these states in PMMA/MnO2:Cu nanocomposite film. Therefore, this nanocomposite film had weaker NA behavior than other nanocomposite films. On the other hand, the larger number of localized defect states of the PMMA/MnO2:Co nanocomposite as compared to PMMA/MnO2 film caused stronger NA behavior. The PMMA/MnO2:Co nanocomposite film had stronger optical limiting feature than other nanocomposite films. In light of all results, these materials are potentially useful for constructing saturable absorbers and optical limiters by modulating in-gap states.