Investigation of the structure and dielectric properties of doped barium titanates.

This work examined the influence of zirconium concentration on barium titanate (BZT) BaZrxTi1-xO3, with (x = 0, 0.15, 0.50, 0.75, and 1), produced by the tartrate precursor technique. The Fourier transform infrared (FTIR) spectra support the X-ray diffraction (XRD) results regarding formation of the perovskite structure. Grain size grows with Zr concentration, suggesting that the presence of Zr ions enlarges the grains. The transmission electron microscopy (TEM) images demonstrated that, due to their nano size, nanocrystallites are agglomerated in most images with irregular morphologies and average particle sizes from 20.75 nm to 63.75 nm. Increasing Zr content diminished the piezoelectric coefficient (d33) and the grain size. The value of d33 decreases by increasing Zr content, and there is an inverse relationship between grain size and d33. The remnant polarization of BZT increases with increasing Zr4+ content, which may be suitable for permanent memory device applications.

Growing crystals and studying structure and electronic properties of Cu2ZnGe(SÑ Se1-x)4 compositions.

Single crystals of Cu2ZnGeSe4 and Cu2ZnGeS4 solid solutions were developed and successfully obtained using the chemical vapor transfer method, with iodine acting as a transporter. The structure, compositional dependences of lattice parameters, pycnometric and X-ray densities and microhardness were determined. The chemical composition determined by the X-ray microanalysis satisfactorily corresponds to the nominal one with a tolerance of ±5 %. The XRD analysis showed that all the obtained compounds and their solid solutions have unit cell described by tetragonal symmetry. The attice parameters were found to be а = 5.342 ± 0.005 Å, с = 10.51 ± 0.01 Å for the Сu2ZnGeS4 compound and а = 5.607 ± 0.005 Å, с = 11.04 ± 0.01 Å for the Cu2ZnGeSe4, respectively. Structural studies confirmed the validity of the Vegard's law in relation to the obtained samples. The pycnometric densities of ∼4.28 g/cm3 for the Cu2ZnGeS4 and ∼5.46 g/cm3 for the Cu2ZnGeSe4 were found to be slightly less than their X-ray densities of ∼4.32 g/cm3 and ∼5.52 g/cm3, respectively. The maximum microhardness of ∼398 kg/mm2 for these solid solutions corresponds to x = 0.60. The melt point of the solid solutions increases from ∼1180 °C for the Сu2ZnGeSe4 up to ∼1400 °C for the Сu2ZnGeS4. Based on X-ray fluorescence analysis and DTA data, the phase diagram of the Cu2ZnGeSe4-Cu2ZnGeS4 system was constructed. Analysis of the obtained diagram indicates its first type according to Rozbom's classification.

Heavy alloy based on tungsten and bismuth: fabrication, crystal structure, morphology, and shielding efficiency against gamma-radiation.

W-Bi2O3 composites were fabricated using the hot isostatic pressing technique for the first time. The duration of the samples sintering was 3 minutes under conditions of high pressure and temperature. The study of microstructural features and chemical composition of sintered samples was carried out using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The effect of temperature on the quality of the obtained W-Bi2O3 composites is determined. The densest samples were obtained at a pressure of 5 GPa and temperatures of 25 °C and 500 °C, the densities of which were 18.10 and 17.85 g cm-3, respectively. It is presented that high temperature exposure during sintering adversely affects both the composite density and microstructure due to the redox reaction accompanied by the reduction of Bi and the oxidation of W. The results of the W-Bi2O3 structure study using X-ray diffraction analysis showed that all samples included the main bulk-centered cubic W phase. The presence of the WO2 phase is noted only when the sintering temperature is increased up to 850 °C, which is confirmed by the appearance of diffraction peaks that correspond to 111 and 22-2 crystallographic planes. The shielding efficiency of the W-Bi2O3 composite against gamma radiation using the Phy-X/PSD software was evaluated. A Co60 isotope with an energy of 0.826-2.506 MeV was used as a source of gamma radiation. The calculation results were compared with those for Pb and Bi. Key shielding parameters such as the linear attenuation coefficient, half-value layer, tenth-value layer, mean free path, and effective atomic number are determined. The calculation results revealed that the W-Bi2O3 composite surpasses Pb and Bi in its shielding properties, which makes it promising for use as a prospective material for radiation shielding applications.

Preparation, phase stability, and magnetization behavior of high entropy hexaferrites.

The polycrystalline SrFe12O19 samples deeply substituted up to at.67% by Al3+, Ga3+, In3+, Co3+, and Cr3+ cations with a high configurational mixing entropy were prepared by solid-phase synthesis. Phase purity and unit cell parameters were obtained from XRD and analyzed versus the average ionic radius of the iron sublattice. The crystallite size varied around ∼4.5 µm. A comprehensive study of the magnetization was realized in various fields and temperatures. The saturation magnetization was calculated using the Law of Approach to Saturation. The accompanying magnetic parameters were determined. The magnetic crystallographic anisotropy coefficient and the anisotropy field were calculated. All investigated magnetization curves turned out to be nonmonotonic. The magnetic ordering and freezing temperatures were extracted from the ZFC and FC curves. The average size of magnetic clusters varied around ∼350 nm. The high values of the configurational mixing entropy and the phenomenon of magnetic dilution were taken into account.

First principles calculation to investigate the effect of Mn substitution on Cu site in CeCu3-x Mn x V4O12 (x = 0, 1, 2 and 3) system.

Structural, electronic, elastic and magnetic properties of CeCu3-x Mn x V4O12 (x = 0, 1, 2 and 3) system have been carried out through DFT using GGA, GGA+U and HF potential. The investigation of structural optimization reveals that lattice parameters of the understudy system is reliable with the reported results and are increasing with the Mn substitution due to their greater atomic radii as compare to Cu atom. Both the cohesive energy and the enthalpy show that CeCu3V4O12 is the most thermodynamically stable among these compounds. When Mn is replaced by Cu in these compounds, not only it become semi-metals, but the host compound also changes from non-magnetic to anti-ferromagnetic and their electrical resistance provides further credence to their electronic behavior. Mechanical stability, anisotropy, and ductility are all demonstrated through the elastic characteristics of these compounds. Due to anti-ferromagnetic ductile nature of the Mn base compounds, it is expected that the compounds in the system may use for spintronic application and in magnetic cloaking devices.

Mechanism of bubbles formation and anomalous phase separation in the CoNiP system.

This study announces the anomalous phase separation in CoNiP alloy electroplating. The observed phenomenon of the formation of magnetic bubbles was described for the first time for this triple CoNiP system. This study briefly covers all stages of magnetic bubble formation, starting from the formation of an amorphous phosphor-rich sublayer, followed by nucleation centers, and finally cobalt-rich bubbles. An explanation for the anomalous mechanism of bubble formation was found in the effects of additives and the phenomena of depolarization and superpolarization.

Electro-oxidation reconstitution of aluminium copper MOF-derived metal oxyhydroxides for a robust OER process.

It is common knowledge that the O2 evolution reaction (OER) is a crucial half-reaction in the electrolysis of water. However, it is currently difficult to create inexpensive OER electrode materials in a way that is efficient, simple, and environmentally friendly. In this research, metal oxy-hydroxides with numerous oxygen defects (M-OOHv) are created at surface of Cu foam (CF) using a unique, straightforward electro-oxidation reconstitution (ER) process. Different spectroscopic and microscopy methods are used to analyse the electrode characteristics of Al2Cu-MOF@M-OOHv-ER/CF; electrochemical measurements display a lower overpotential (η) of 366 mV @ 10 mA cm-2 and a Tafel slope of 95.2 mV dec-1 in 1.0 M KOH. X-Ray diffraction (XRD), scanning electron microscopy (SEM), and Raman studies confirm the phase transition of the metal-organic framework (MOF) to the M-OOH, which acts as the active site to boost the OER activity. Through spectroscopic and microscopic investigations, it is determined that the efficiency of bimetallic electrode materials and oxygen vacancies in the M-OOHv have an impact on the electron power density. The manufactured electrode material additionally showed good durability for 50 hours. As a result, the newly developed Al2Cu-MOF@M-OOHv-ER/CF nanomaterial has greater potential for both electrolysis of water and other energy storage equipment.

Microstructure and high frequency electromagnetic parameters of the soft/soft (CoFe2O4) x : (Ni0.4Cu0.2Zn0.4Fe2O4) y nanocomposites.

The soft/soft (CoFe2O4) x : (Ni0.4Cu0.2Zn0.4Fe2O4) y (CFO x /NCZO y ) nanocomposites (NCs) based on spinel ferrites were produced by the sol-gel method with varying phase's ratio (x : y = 0 : 1; 1 : 1; 2 : 1; 3 : 1; 1 : 3; 1 : 2 and 1 : 0). All NCs consisted of 2 single phases (initial spinels) without any impurities and the absence of chemical interaction between phases. Structural features were investigated and analyzed. The varying of the structural parameters was non-linear and correlated well with the lattice parameter for initial components. There were two maxima observed for all NCs on particle size distribution. It was demonstrated that an increase in the CFO content leads to an increase in the most probable size of the coarse fraction and a decrease in the most probable grain size of the fine fraction. An increase in the NCZO content leads to a decrease in the average size of both fine and coarse fractions. This is obviously due to the large number of defects in the NCZO crystal lattice. The high frequency electromagnetic parameters (real and imaginary parts of the permittivity and permeability, reflection losses) were analyzed in the range of 2-10 GHz. The increase of the energy losses with frequency increase was observed. The nature of the attenuation of the reflected energy associated with the electromagnetic absorption processes due to magnetic losses. Maximal values of the electromagnetic absorption were observed for CFO2/NCZO1 (-18.9 dB). This correlates with the lattice parameters of the composites. The result of the electromagnetic characteristics opens broad perspectives for practical applications such kind of NCs for antenna technology (5G technology) and for electromagnetic absorbing coatings.

Mechanically Stable Magnetic Metallic Materials for Biomedical Applications.

The structural, electrical, and magneto-elastic properties of lanthanide base nitride (Ln = Dy-Lu) anti-perovskites were investigated using density functional theory (DFT). The reported structural outcomes are consistent with the experiment and decrease from Dy to Lu due to the decrease ofatomic radii of Ln atoms. According to the electronic band profile, the metallic characteristics of these compounds are due to the crossing over of Ln-f states at the Fermi level and are also supported by electrical resistivity. The resistivity of these compounds at room temperature demonstrates that they are good conductors. Their mechanical stability, anisotropic, load-bearing, and malleable nature are demonstrated by their elastic properties. Due to their metallic and load-bearing nature, in addition to their ductility, these materials are suitable as active biomaterials, especially when significant acting loads are anticipated, such as those experienced by such heavily loaded implants as hip and knee endo-prostheses, plates, screws, nails, dental implants, etc. In thesecases, appropriate bending fatigue strength is required in structural materials for skeletal reconstruction. Magnetic properties show that all compounds are G-type anti-ferromagnetic, with the Neel temperatures ranging from 24 to 48 K, except Lu3Nin, which is non-magnetic. Due to their anti-ferromagnetic structure, magnetic probes cannot read data contained in anti-ferromagnetic moments, therefore, data will be unchanged by disrupted magnetic field. As a result, these compounds can be the best candidates for magnetic cloaking devices.

Impact of Nd3+ Substitutions on the Structure and Magnetic Properties of Nanostructured SrFe12O19 Hexaferrite.

In this study, SrFe12-xNdxO19, where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5, was prepared using high-energy ball milling. The prepared samples were characterized by X-ray diffraction (XRD). Using the XRD results, a comparative analysis of crystallite sizes of the prepared powders was carried out by different methods (models) such as the Scherrer, Williamson-Hall (W-H), Halder-Wagner (H-W), and size-strain plot (SSP) method. All the studied methods prove that the average nanocrystallite size of the prepared samples increases by increasing the Nd concentration. The H-W and SSP methods are more accurate than the Scherer or W-H methods, suggesting that these methods are more suitable for analyzing the XRD spectra obtained in this study. The specific saturation magnetization (σs), the effective anisotropy constant (Keff), the field of magnetocrystalline anisotropy (Ha), and the field of shape anisotropy (Hd) for SrFe12-xNdxO19 (0 ≤ x ≤ 0.5) powders were calculated. The coercivity (Hc) increases (about 9% at x = 0.4) with an increasing degree of substitution of Fe3+ by Nd3+, which is one of the main parameters for manufacturing permanent magnets.

Features of Galvanostatic Electrodeposition of NiFe Films with Composition Gradient: Influence of Substrate Characteristics.

NiFe films with a composition gradient are of particular interest from the point of view of fundamental science and practical applications. Such gradient magnetic structures may exhibit unique functional properties useful for sensory applications and beyond. The issue surrounds the anomaly concerning the compositional gradient formed near the substrate in electrolytically deposited binary and ternary iron-containing alloys, which has not previously been clearly explained. In this work, light is shed on this issue, and a clear relationship is found between the structure and surface properties of the substrate, the initially formed NiFe layers and the film composition gradient.

Modeling and X-ray Analysis of Defect Nanoclusters Formation in B4C under Ion Irradiation.

In the presented work, B4C was irradiated with xenon swift heavy ions at the energy of 167 MeV. The irradiation of the substrate was done at room temperature to a fluence of 3.83 × 1014 ion/cm2. The samples were then analyzed with the X-ray diffraction technique to study the structural modification, as it can probe the region of penetration of xenon atoms due to the low atomic number of the two elements involved in the material under study. The nano-cluster formation under ion irradiation was observed. Positron lifetime (PLT) calculations of the secondary point defects forming nanoclusters and introduced into the B4C substrate by hydrogen and helium implantation were also carried out with the Multigrid instead of the K-spAce (MIKA) simulation package. The X-ray diffraction results confirmed that the sample was B4C and it had a rhombohedral crystal structure. The X-ray diffraction indicated an increase in the lattice parameter due to the Swift heavy ion (SHI) irradiation. In B12-CCC, the difference between τ with the saturation of H or He in the defect is nearly 20 ps. Under the same conditions with B11C-CBC, there is approximately twice the value for the same deviation.

Impact of Ga3+ Ions on the Structure, Magnetic, and Optical Features of Co-Ni Nanostructured Spinel Ferrite Microspheres.

Co-Ni ferrite is one of the crucial materials for the electronic industry. A partial substitution with a rare-earth metal brings about modification in crystal lattice and broadens knowledge in the discovery of new magnetic material. Current work reports a Ga3+ substitution in the Co-Ni ferrite with composition Co0.5Ni0.5Fe2-xGaxO4 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0), herein referred to as spinel ferrite microspheres (CoNiGa-SFMCs). The samples were crystallized hydrothermally showing a hollow sphere morphology. The crystal phase, magnetic, morphology, and optical behaviour were examined using various microscopy and spectroscopic tools. While the XRD confirmed the phase of SFMCs, the crystallite size varied between 9 and 12 nm. The Tauc plot obtained from DRS (diffuse reflectance spectroscopy) shows the direct optical energy bandgap (Eg) of the products, with the pristine reading having the value of 1.41 eV Eg; the band gap increased almost linearly up to 1.62 eV along with rising the Ga3+ amount. The magnetic features, on the other hand, indicated the decrease in coercivity (Hc) as more Ga3+ is introduced. Moreover, there was a gradual increase in both saturation magnetization (Ms) and magnetic moment (nB) with increasing amount of Ga3+ till x = 0.6 and then a progressive decline with increases in the x content; this was ascribed to the spin-glass-like behavior at low temperatures. It was detected that magnetic properties correlate well with crystallite/particle size, cation distribution, and anisotropy.

The Interrelation of Synthesis Conditions and Wettability Properties of the Porous Anodic Alumina Membranes.

The results of studies on the wettability properties and preparation of porous anodic alumina (PAA) membranes with a 3.3 ± 0.2 µm thickness and a variety of pore sizes are presented in this article. The wettability feature results, as well as the fabrication processing characteristics and morphology, are presented. The microstructure effect of these surfaces on wettability properties is analyzed in comparison to outer PAA surfaces. The interfacial contact angle was measured for amorphous PAA membranes as-fabricated and after a modification technique (pore widening), with pore sizes ranging from 20 to 130 nm. Different surface morphologies of such alumina can be obtained by adjusting synthesis conditions, which allows the surface properties to change from hydrophilic (contact angle is approximately 13°) to hydrophobic (contact angle is 100°). This research could propose a new method for designing functional surfaces with tunable wettability. The potential applications of ordinary alumina as multifunctional films are demonstrated.

Flowery ln2MnSe4 Novel Electrocatalyst Developed via Anion Exchange Strategy for Efficient Water Splitting.

Oxygen and hydrogen generated by water electrolysis may be utilized as a clean chemical fuel with high gravimetric energy density and energy conversion efficiency. The hydrogen fuel will be the alternative to traditional fossil fuels in the future, which are near to exhaustion and cause pollution. In the present study, flowery-shaped In2MnSe4 nanoelectrocatalyst is fabricated by anion exchange reaction directly grown on nickel foam (NF) in 1.0 M KOH medium for oxygen evolution reaction (OER). The physiochemical and electrical characterization techniques are used to investigate the chemical structure, morphology, and electrical properties of the In2MnSe4 material. The electrochemical result indicates that synthesized material exhibits a smaller value of Tafel slope (86 mV/dec), lower overpotential (259 mV), and high stability for 37 h with small deterioration in the current density for a long time. Hence, the fabricated material responds with an extraordinary performance for the OER process and for many other applications in the future.

Combined Effect of Microstructure, Surface Energy, and Adhesion Force on the Friction of PVA/Ferrite Spinel Nanocomposites.

Nanocomposite films based on spinel ferrite (Mg0.8Zn0.2Fe1.5Al0.5O4) in a PVA matrix were obtained. An increase in the spinel concentration to 10 wt.% caused an avalanche-like rise in roughness due to the formation of nanoparticle agglomerates. The lateral mode of atomic force microscopy (AFM) allowed us to trace the agglomeration dynamics. An unexpected result was that the composite with 6 wt.% of filler had a low friction coefficient in comparison with similar composites due to the successfully combined effects of low roughness and surface energy. The friction coefficient decreased to 0.07 when the friction coefficient of pure PVA was 0.72. A specially developed method for measuring nano-objects' surface energy using AFM made it possible to explain the anomalous nature of the change in tribological characteristics.

Isostatic Hot Pressed W-Cu Composites with Nanosized Grain Boundaries: Microstructure, Structure and Radiation Shielding Efficiency against Gamma Rays.

The W-Cu composites with nanosized grain boundaries and high effective density were fabricated using a new fast isostatic hot pressing method. A significantly faster method was proposed for the formation of W-Cu composites in comparison to the traditional ones. The influence of both the high temperature and pressure conditions on the microstructure, structure, chemical composition, and density values were observed. It has been shown that W-Cu samples have a polycrystalline well-packed microstructure. The copper performs the function of a matrix that surrounds the tungsten grains. The W-Cu composites have mixed bcc-W (sp. gr. Im 3¯ m) and fcc-Cu (sp. gr. Fm 3¯ m) phases. The W crystallite sizes vary from 107 to 175 nm depending on the sintering conditions. The optimal sintering regimes of the W-Cu composites with the highest density value of 16.37 g/cm3 were determined. Tungsten-copper composites with thicknesses of 0.06-0.27 cm have been fabricated for the radiation protection efficiency investigation against gamma rays. It has been shown that W-Cu samples have a high shielding efficiency from gamma radiation in the 0.276-1.25 MeV range of energies, which makes them excellent candidates as materials for radiation protection.

Creation and Magnetic Study of Ferrites with Magnetoplumbite Structure Multisubstituted by Al3+, Cr3+, Ga3+, and In3+ Cations.

Multisubstituted barium ferrites with a magnetoplumbite structure were obtained by the method of solid-phase reactions with ferritization and pre-firing. Three-charged, mainly diamagnetic cations Al3+, Cr3+, Ga3+, and In3+ were chosen as substituents for the Fe3+ iron cations, the proportion of which in solid solutions did not exceed 50%. The values of the configurational mixing entropy were calculated for all the compositions. A slight deviation of the chemical composition of the obtained solid solutions from the nominal value was established by the energy-dispersive X-ray spectroscopy method. The phase purity and values of the unit cell parameters were refined from X-ray scattering data using full-profile analysis in the Rietveld method. A non-monotonic behavior of the unit cell parameters as a function of the B-sub-lattice average ionic radius of the magnetoplumbite structure was found. A minimum unit cell volume of ~667.15 Å3 was found for the composition BaFe6.11Al1.56Cr2.17Ga2.16O19 with a B-sub-lattice average ionic radius of ~7.449 Å. The average crystallite size varied within 5.5-6.5 µm. The temperature and field dependencies of the magnetization have been measured. The values of the saturation magnetization, residual magnetization, hysteresis loop squareness, and coercivity at 50 K and 300 K were extracted from the experimental data. Using the Law of Approach to Saturation, the magnetic crystallographic anisotropy coefficient and anisotropy field were calculated. Multisubstitution leads to a significant decrease in such magnetic parameters as the magnetic ordering temperature and spontaneous magnetization at both temperatures. The maximum magnetic ordering temperature of ~297.7 K was found for the composition BaFe5.84Ga6.19O19 with a B-sub-lattice average ionic radius of ~7.586 Å in a field of 500 Oe. A maximum saturation magnetization of ~24.7 emu/g was found for the composition BaFe5.84Ga6.19O19 with a B-sub-lattice average ionic radius of ~7.586 Å at 50 K. A maximum hysteresis loop squareness of ~0.72 was found for the composition BaFe6.11Al1.56Cr2.17Ga2.16O19 with an average ionic radius of ~7.449 Å at 50 K. A maximum magnetic crystallographic anisotropy coefficient of ~2.09 × 105 Erg/g was found for the composition BaFe6.19Al1.25Cr1.57Ga1.74In1.26O19 with a B-sub-lattice average ionic radius of ~7.706 Å at 50 K. The frustrated magnetic state including the nano-sized clusters with an average diameter in the range of 50-200 nm was established from the results of measuring the ZFC and FC temperature magnetizations. The interpretation of the obtained experimental data is carried out taking into account the increased stability of high-entropy phases and regular changes in the intensity of the Fe3+(Al3+, Cr3+, Ga3+, In3+)-O2--Fe3+(Al3+, Cr3+, Ga3+, In3+) indirect superexchange interactions as a result of magnetic dilution of the iron sub-lattice in the magnetoplumbite structure.

Structure, Morphology and Electrical/Magnetic Properties of Ni-Mg Nano-Ferrites from a New Perspective.

Using the auto combustion flash method, Ni1-x+2Mgx+2Fe2+3O4 (x = 0, 0.2, 0.6, 0.8 and 1) nano-ferrites were synthesized. All samples were thermally treated at 973 K for 3 h. The structural analysis for the synthesized samples was performed using XRD, high-resolution transmission electron microscopy (HRTEM), and FTIR. Scanning electron microscopy (SEM) was undertaken to explore the surface morphology of all the samples. The thermal stability of these samples was investigated using thermogravimetric analysis (TGA). XRD data show the presence of a single spinel phase for all the prepared samples. The intensity of the principal peak of the spinel phase decreases as Mg content increases, showing that Mg delays crystallinity. The Mg content raised the average grain size (D) from 0.084 µm to 0.1365 µm. TGA shows two stages of weight loss variation. The vibrating sample magnetometer (VSM) measurement shows that magnetic parameters, such as initial permeability (µi) and saturation magnetization (Ms), decay with rising Mg content. The permeability and magnetic anisotropy at different frequencies and temperatures were studied to show the samples' magnetic behavior and determine the Curie temperature (TC), which depends on the internal structure. The electrical resistivity behavior shows the semi-conductivity trend of the samples. Finally, the dielectric constant increases sharply at high temperatures, explained by the increased mobility of charge carriers, and decreases with increasing frequency.

Eco-Friendly NiO/Polydopamine Nanocomposite for Efficient Removal of Dyes from Wastewater.

The rapid development of industries discharges huge amounts of wastewater that contain surface water. For this reason, we used NiO/polydopamine (NiO/PDA) nanocomposite as an efficient material for the removal of Methyl violet 2B from water. It was synthesized and then characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Brunauer-Emmett-Teller (BET). The EDX analysis confirmed the presence of O, Ni, N, and C. The composite has an average particle size of 18 nm. Its surface area is 110.591 m2/g. It was found that the efficiency of dye removal by adsorption on NiO/PDA exceeded that of bare NiO. The adsorption capacity of NiO and NiO/PDA are 126 and 284 mg/g, respectively. The effects of adsorbent dose, dye concentration, and pH on the removal efficiency were examined. The efficiency increased with increasing the adsorbent dose and pH, but dropped from 85 to 73% within 30 min as the initial dye concentration was increased from 0.984 to 4.92 mg/L. Such a drop in the removal efficiency is due to the blocking of the surface-active sites of NiO/PDA, with the high population of dye molecules derived from the continuous increase in dye concentration. The adsorption results of the dye fitted well with the pseudo-second-order kinetics and Langmuir isotherm. The reusability data showed that NiO/PDA was stable across three adsorption-regeneration cycles, thus it can be considered a good recyclable and efficient adsorbent. Because of these results, it can be considered that this method can be applied for the treatment of wastewater.