The dependence of Ni-Fe bioxide composites nanoparticles on the FeCl2 solution used

BACKGROUND: Ni(2)O(3)- γ-Fe(2)O(3) composite nanoparticles coated with a layer of 2FeCl(3)·5H(2)O can be prepared by co-precipitation and processing in FeCl(2) solution. Using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) diffraction techniques, the dependence of the preparation on the concentration of the FeCl(2) treatment solution is revealed. RESULTS: The magnetization of the as-prepared products varied non-monotonically as the FeCl(2) concentration increased from 0.020 M to 1.000 M. The Experimental results show that for the composite nanoparticles, the size of the γ-Fe(2)O(3) phase is constant at about 8 nm, the Ni(2)O(3) phase decreased and the 2FeCl(3)·5H(2)O phase increased with increasing concentration of FeCl(2) solution. The magnetization of the as-prepared products mainly results from the γ-Fe(2)O(3) core, and the competition between the reduction of the Ni(2)O(3) phase with the increase of the 2FeCl(3)·5H(2)O phase resulted in the apparent magnetization varying non-monotonically. CONCLUSIONS: When the concentration of FeCl(2) treatment solution did not exceed 0.100 M, the products are spherical nanoparticles of size about 11 nm; their magnetization increased monotonically with increasing the concentration of FeCl(2) solution due to the decreasing proportion of Ni(2)O(3) phase

Preparation of Magnetic Nanoparticles via a Chemically Induced Transition: Presence/Absence of Magnetic Transition on the Treatment Solution Used

The dependence of magnetic transition on the treatment solution used in the preparation of magnetic nanoparticles was investigated using as-prepared products from paramagnetic FeOOH/Mg(OH)2 via a chemically induced transition. Treatment using FeCl3 and CuCl solutions led to a product that showed no magnetic transition, whereas the product after treatment with FeSO4 or FeCl2 solutions showed ferromagnetism. Experiments revealed that the magnetism was caused by the ferrimagnetic γ-Fe2O3 phase in the nanoparticles, which had a coating of ferric compound. This observation suggests that Fe2+ in the treatment solution underwent oxidation to Fe3+, thereby inducing the magnetic transition. The magnetic nanoparticles prepared via treatment with an FeSO4 solution contained a larger amount of the nonmagnetic phase. This resulted in weaker magnetization even though these nanoparticles were larger than those prepared by treatment with an FeCl2 solution. The magnetic transition of the precursor (FeOOH/Mg(OH)2) was dependent upon treatment solutions and was essentially induced by the oxidation of Fe2+ and simultaneous dehydration of FeOOH phase. The transition was independent of the acid radical ions in the treatment solution, but the coating on the magnetic crystallites varied with changes in the acid radical ion

The extrinsic hysteresis behavior of dilute binary ferrofluids

We report on the magnetization behavior of dilute binary ferrofluids based on $\gamma$ - Fe2O3/Ni2O3 composite nanoparticles (A particles), with diameter about 11nm, and ferrihydrite ( Fe5O7(OH)·4H2O nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction $\phi_{A}$ = 0.2 % and B-particle volume fractions $\phi_{B}$ = 0.1 % and $\phi_{B}$ = 0.6 %, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single $\gamma$ - Fe2O3/Ni2O3 ferrofluids with $\phi_{A}$ = 0.2 % and binary ferrofluids with $\phi_{A}$ = 0.2 % and $\phi_{B}$ = 1.0 %, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with $\phi_{B}$ = 1.0 % has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains’ moments and a Néel rotation of the particles’ moments in the chains. The loss of magnetization for the ferrofluids with $\phi_{B}$ = 1.0 % is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system

Cu(I) Modification during γ-Fe2O3 Nanoparticles Synthesis and Subsequent Characterization

During the synthesis of the γ-Fe2O3 nanoparticles via the chemically induced transition method, Cu(I) modification has been attempted by adding CuCl/NaOH to the treatment solution. The experimental results showed that, under the condition of a NaOH content equal to 0.04 moles, when the content of CuCl is as low as 1.25×10-3 or 2.50×10-3 moles, the products are single γ-Fe2O3/Cu(I)FeO2/FeCl3·6H2O composite nanoparticles, whereas when the content of CuCl is higher, 5×10-2 moles, the product is a mixture consisting of γ-Fe2O3/Cu(I)FeO2/FeCl3·6H2O nanoparticles and Cu(II)(OH)Cl nanoparticles. For the γ-Fe2O3/Cu(I)FeO2/FeCl3·6H2O composite nanoparticles, the Cu(I)FeO2 interface layer is not thick enough to form one unit cell, but it can modify the formation of a FeCl3·6H2O surface layer and the effective magnetization of the γ-Fe2O3 core

Periodic Electro-Optical Characteristics of PDLC Film Driven by a Low-Frequency Square Wave Voltage

The electro-optical features of the PDLC films applied with a low-frequency square wave voltage were investigated. The transmittance curves indicated the double frequency of the applied voltage at 0–50 Hz, which resulted from the relaxation of an internal electric field polarized by ions in LC droplets. When the local electric field was reversed, the internal polarization electric field could be maintained and superimposed on the local electric field. The relaxation of the internal polarized electric field resulted in the relaxation of the transmittance. Furthermore, the transmittance curves changed with the frequency of the applied voltage

Periodic Electro-Optical Characteristics of PDLC Film Driven by a Low-Frequency Square Wave Voltage

The electro-optical features of the PDLC films applied with a low-frequency square wave voltage were investigated. The transmittance curves indicated the double frequency of the applied voltage at 0–50 Hz, which resulted from the relaxation of an internal electric field polarized by ions in LC droplets. When the local electric field was reversed, the internal polarization electric field could be maintained and superimposed on the local electric field. The relaxation of the internal polarized electric field resulted in the relaxation of the transmittance. Furthermore, the transmittance curves changed with the frequency of the applied voltage

Estimating Nutrient Uptake Requirements for Melon Based on the QUEFTS Model

Imbalanced and excessive fertilizer application has resulted in low yields and reduced nutrient use efficiency for melon production in China. Estimating nutrient requirements is crucial for effectively developing site-specific fertilizer recommendations for increasing yield and profit while reducing negative environmental impacts. Relationships between the yield and nutrient uptake requirements of above-ground dry matter were assessed using 1127 on-farm observations (2000–2020) from melon production regions of China. The quantitative evaluation of fertility of tropical soils (QUEFTS) model was used to estimate nutrient requirements. It predicted a linear increase in yield at balanced nutrient uptake levels until the yield reached approximately 60–80% of the potential yield. In order to produce 1000 kg of fruit, 2.9, 0.4 and 3.2 kg/ha of N, P and K (7.2:1.0:7.8), respectively, were required for above-ground parts, while the corresponding nutrient internal efficiencies were 345.3, 2612.6 and 310.0 kg per kg N, P and K, respectively, whereas 1.4, 0.2 and 1.9 kg of N, P and K were required to replace nutrients removed after harvest. The corresponding fruit absorption rates were 47.0%, 59.5% and 58.2%, respectively. Field validation experiments confirmed the consistency between observed and simulated uptake rates, indicating that this model could estimate nutrient requirements. These findings will help develop fertilizer recommendations for improving melon yield and nutrient use efficiency

Preparation of Magnetic Nanoparticles via a Chemically Induced Transition: Role of Treating Solution’s Temperature

Using FeOOH/Mg(OH)2 as precursor and FeCl2 as the treating solution, we prepared γ-Fe2O3 based nanoparticles. The FeCl2 treating solution catalyzes the chemical reactions, dismutation and oxygenation, leading to the formation of products FeCl3 and Fe2O3, respectively. The treating solution (FeCl2) accelerates dehydration of the FeOOH compound in the precursor and transforms it into the initial seed crystallite γ-Fe2O3. Fe2O3 grows epitaxially on the initial seed crystallite γ-Fe2O3. The epitaxial layer has a magnetically silent surface, which does not have any magnetization contribution toward the breaking of crystal symmetry. FeCl3 would be absorbed to form the FeCl3·6H2O surface layer outside the particles to form γ-Fe2O3/FeCl3·6H2O nanoparticles. When the treating solution’s temperature is below 70 °C, the dehydration reaction of FeOOH is incomplete and the as-prepared samples are a mixture of both FeOOH and γ-Fe2O3/FeCl3·6H2O nanoparticles. As the treating solution’s temperature increases from 70 to 90 °C, the contents of both FeCl3·6H2O and the epitaxial Fe2O3 increased in totality