Ni Ferrite Powders Research Articles

Study of the performance of Co and Ni ferrites after several cycles involved in water-splitting thermochemical cycles

Water splitting thermochemical cycles based on metal oxide systems and using concentrated solar energy is a promising and sustainable clean process for hydrogen production. In this work, the capability of Ni and Co powder ferrites for hydrogen production via two step redox processes has been tested. In order to avoid decreasing of the hydrogen release with the number of cycles due to powder sintering, a simple handmade pellet preparation has been used. Then, samples in the forms of pellets or powders were tested for the water splitting reaction under the same experimental conditions, and the amount of hydrogen generated in each case has been compared. Results show that pellet samples maintain their shape after the cycling process, although higher hydrogen production rate is obtained for Ni ferrite powder samples. This study also includes a thorough chemical, structural and morphological characterization of the samples after thermochemical cycling.

Structure and properties of nanosize NiFe2O4 prepared by template and precipitation methods

Nanosize NiFe2O4 was prepared by template method and precipitation process using same starting materials. The use of soluble starch in both synthesis routes was investigated. The amount of the used precipitating agent (Na2CO3) for the precipitation approach was selected according to two adopted scenarios based on theoretical and average yield of possible side reaction expressed by the degree of substitution (DS). The results of SEM microstructural analysis of the prepared Niferrite powders demonstrate evident influence of the applied preparation method whereas high-magnification FE-SEM images show very similar fine-grained structures characterized by different size of particles. According to the results of XRD analysis, the obtained ferrite powders exhibit only slight differences in phase composition with calculated crystallite size for template sample dXRD = 36 nm and for the both precipitation route samples dXRD = 21 nm. Additional sample characterization using 57Fe M?ssbauer spectroscopy supports the findings of the microstructural and XRD analysis. The ?clearest? spectrum was obtained for the template sample while the strongest influence of nanocrystalline component was observed for the sample prepared with maximal amount of precipitation agent (DS=3). The room temperature magnetic hysteresis loops, recorded using vibrating sample magnetometer (VSM), are very similar and exhibit characteristic shape with values of magnetic properties within expected range for this type of material.

Fabrication of Co0.5Ni0.5CrxFe2−xO4 materials via sol–gel method and their characterizations

Co0.5Ni0.5CrxFe2−xO4 nanoparticles have been designed by the sol–gel auto combustion method, using nitrates of the respective metal ions, and citric acid as the starting materials. The process takes only a few minutes to obtain as-received Cr-substituted Co–Ni ferrite powders. X-ray diffraction (XRD), vibrational sample magnetometer (VSM), transmission electron microscopy (TEM) are utilized in order to study the effect of variation in the Cr3+ substitution and its impact on particle size, lattice constant, specific surface area, cation distribution and magnetic properties. Lattice parameter, particle size found to decrease with increasing Cr3+ content, whereas specific surface area showed increasing trend with the Cr3+ substitution. Cation distribution indicates that the Cr, Co and Ni ions show preference toward octahedral [B] site, whereas Fe occupies both tetrahedral (A) and octahedral [B] sites. Saturation magnetization (MS) decreased from 65.1 to 40.6emu/g with the increase in Cr3+ substitution. However, Coercivity increased from 198 to 365Oe with the Cr3+ substitution.

Ni-페라이트 분말을 이용한 CO2분해 특성

본 연구의 목적은 연소 배기가스로부터 포집된 이산화탄소를 다시 일산화탄소 또는 탄소로 전환하여 산업에 다시 활용하고자 하는 탄소순환형 기술개발이다. 이산화탄소는 화학적으로 안정한 분자로써 쉽게 분해되지 않기 때문에 낮은 온도에서 반응이 일어날 수 있는 적합한 금속계 산화물(활성화제)의 선택이 필요하다. 따라서 본 연구에서는 Ni-Fe 전이금속산화물을 사용하여 <TEX>$CO_2$</TEX>를 CO나 C로 전환하고자 하였다. 시료는 고상법과 수열합성을 이용해 제조된 분말을 사용하여 각각 이산화탄소 분해특성 연구를 수행하였다. 이산화탄소의 분해 특성을 관찰하기 위해 TPR/TPO와 TGA 장치를 사용하였다. TPR/TPO를 이용한 수소의 환원면적은 NiO의 함량이 15wt%일 때 높게 나타났고, <TEX>$CO_2$</TEX>에 의한 흡착분해 곡선면적은 NiO의 함량이 5wt%일 때 우수한 성능을 나타내었다. 그러나 TGA를 이용한 실험결과에서는 고상법에 의해 제조된 시료 중 NiO의 함량이 2.5wt%일 때 수소에 의한 흡착환원이 28.47wt% 발생하였고, <TEX>$CO_2$</TEX>에 의한 산화량의 경우 26.95wt%로 가장 높게 나타났다. 그리고 이산화탄소의 분해효율이 94.66%로 우수한 산화 환원 특성을 나타내었다. The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose <TEX>$CO_2$</TEX> because <TEX>$CO_2$</TEX> is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of <TEX>$CO_2$</TEX> at low temperature. Metal oxides, which converts <TEX>$CO_2$</TEX> to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of <TEX>$CO_2$</TEX>. As the results, the reduction area of <TEX>$H_2$</TEX> was high value at 15 wt% of NiO and the decomposition area of <TEX>$CO_2$</TEX> was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of <TEX>$H_2$</TEX> was 28.47wt% and oxidation area by <TEX>$CO_2$</TEX> was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. <TEX>$CO_2$</TEX> decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.

Malonic acid: A potential reagent in decontamination processes for Ni-rich alloy surfaces

The ability of malonic acid as a dissolution agent toward synthetic Ni ferrite and Alloy 600 and 800 corrosion products was explored. Its performance in the dissolution kinetics of Ni ferrite powders was compared with the one of oxalic acid. Kinetic parameters were obtained and the dependency on external Fe(II) was modelled. Oxidized samples used in descaling tests were prepared by exposure of coupons of both alloys to lithiated aqueous solutions, under hydrothermal conditions and hydrogen overpressure, simulating PHWR conditions. Oxide layer morphology, the influence of exposure time to corrosive medium and LiOH concentration on its thickness were characterized. Descaling tests consisting on a two-stage method (a first oxidizing step with alkaline permanganate followed by a reducing step with oxalic or malonic acid were carried out). Results were compared to those obtained with a well known chemical cleaning formulation (APAC: Alkaline Permanganate Ammonium Citrate) used in decontamination of several reactors and loops and the competitiveness of malonic acid was demonstrated.

Neutron depolarization study on the magnetic correlation length of nickel ferrite with different packing densities

Abstract The magnetic correlation length of a mixed nickel ferrite powder was studied by a newly commissioned depolarized neutron beamline at the W3 port of Tsing Hua Open Pool Reactor (THOR). In this work, Ni ferrite powder samples with different packing densities were studied. The magnetic correlation lengths of the sample were observed to be 2 μm at virgin state and about 3.1 μm at remanent state from the packing density of 20–60%. This magnetic domain size is smaller than particle size. No significant change of domain size at this packing density implies the domain wall motion is hindered by the porosity effectively up to at least 60% of packing density.

Fabrication of Nano-Sized Powders from Waste Solution by Spray Pyrolysis Process

In order to efficiently recycle the Fe-Ni waste acid solution resulting from shadow mask processing, a spray pyrolysis process was used to fabricate the nano-sized Ni-ferrite powder with the average particle size below lOOnm. The properties of the nano-powder were investigated as function of reaction temperature, concentration and injection speed of raw material solution. As the reaction temperature increases from 800 to 1100°C, the average particle size of the powder increased accordingly, the microstructure of it gradually became solid which is close to the theoretical density, and the surface area of it decreased significantly. Along with the temperature rise, the formation rate of NiFe 2 O 4 phase also increased. As the concentrations of iron and nickel elements in waste solution increased, the average particle size became larger, the particle size distribution became more irregular, the surface area of the powder decreased. Along with the increase of the concentration, the formation rate of NiFe 2 O 4 phase increased significantly. As the air pressure increases up to 1 kg/cm 2 , the average particle size of the powder decreased slightly, yet the ratio of the Ni-ferrite phase kept almost unchanged. As the air pressure increases up to 3 kg/cm 2 , the average particle size and the ratio of the Ni-ferrite phase decreased significantly, yet the particle distribution size appears much more uniform.

A self-propagating high-temperature synthesis method for Ni-ferrite powder synthesis

Ni-ferrite (NiFe 2O 4) powder was synthesized by a self-propagating high-temperature synthesis (SHS) process using Fe, Fe 2O 3 and various Ni-containing species (Ni-CSs) as reactants. The reactants were thoroughly mixed and pressed into a cylindrical compact. The compact was ignited by electrical heating under oxygen partial pressures varying between 0.02 and 1.5 MPa. The effects of the type of Ni-containing species, the reactant composition, the oxygen pressure on the combustion temperature, and the product conversion were investigated. X-ray diffraction (XRD) analysis showed that oxygen pressure promoted product conversion. Among several Ni-containing species tested, Ni 2O 3 was found to give the highest conversion. The product conversion increased with increasing iron content and then decreased with further increase in iron content. Scanning electron microscope (SEM) observations showed that the product synthesized is mostly in the form of agglomerated fine particles with submicron size (0.1–0.5 μm). Hysteresis behavior analysis showed that the product as synthesized possessed better soft magnetic properties when compared with commercial Ni-ferrite prepared by the solid reaction method.

새도우마스크 제조공정 중 발생되는 폐액으로부터 니켈 페라이트 나노 분말 제조

Nano-sized Ni-ferrite powder was fabricated by spray pyrolysis process using the waste solution resulting from shadow mask processing. The average particle size of the powder was below 100 nm. The effects of the concentration of raw material solution, the nozzle tip size and air pressure on the properties of powder were studied. As the concentration increased, the average particle size of the powder gradually increased and its specific surface area decreased, but size distribution was much wider and the fraction of the Ni-ferrite phase greatly increased as the concentration increasing. As the nozzle tip size increased from 1 mm to 2 mm, the average particle size of the powder decreased. In case of 3 mm nozzle tip size, the average particle size of the powder increased slightly. On the other hand, in case of 5 mm nozzle tip size, average particle size of the powder decreased. Size distribution of the powder was unhomogeneous, and the fraction of the Ni-ferrite phase decreased as the nozzle tip size increasing. As air pressure increased up to 1 kg/<TEX>$cm^2$</TEX>, the average particle size of the powder decreased slightly, on the other hand, the fraction of the Ni-ferrite phase was almost constant. In case of 3kg/<TEX>$cm^2$</TEX> air pressure, average particle size of the powder and the fraction of the Ni-ferrite phase remarkably decreased, but size distribution was narrow.

Preparation of Al-substituted Ni ferrite powders via mechanochemical processing

Single-phase NiAlFeO 4 fine particles were prepared via high-energy ball milling (HEBM) and subsequent heat treatments. X-ray diffraction (XRD) of the as-milled powder indicates that a dominant spinel phase forms after 60 h of milling. A complete single phase of NiAlFeO 4 was formed by subsequent heat treatments of the as-milled powder at 950°C, which is lower than the temperature associated with the conventional ceramic technique. XRD, EDS, DTG/M/ and magnetic observations were used to discuss mechanism of the ferrite formation by HEBM and subsequent heat treatments.

Preparation and Characterization of Ni Ferrite Powders by Urea Decomposition

The effects of process parameters such as concentration ratio of urea and nickel(II) iron(II, III) salt solutions, period of aging and the pH of the solution on the synthesis of Ni ferrite from aqueous solutions by decomposition of urea was investigated to develop ferrite-containing porous ceramic fiber materials. The XRD patterns of the precipitation showed that at pH value lower than six both akagenite (β-FeOOH) and Ni ferrites were formed simultaneously. At pH above six, Ni ferrite single phase could be obtained. The precipitates heat treated at 300 °C under nitrogen atmosphere result in a fine powder with BET areas ranging from 8.9 to 22.8 m 2 g -1 . The morphology of Ni ferrite shows agglomerates of spherical particles ranging in the size 50-200 nm.

Temperature Influence on the Composition of Ni-Ferrite Powders Obtained from Complex Compounds with Acetylacetonato-Ligands

The conditions for the synthesis of ultra fine Ni-ferrites powder were investigated. The basic components were Fe(III) and Ni(II) complex compounds with acetylacetonato- (2,4 pentadione) ligands. Nanometrics powders were obtained by annealing the homogeneous mixture of the basic components in protected nitrogen atmosphere at different temperatures. The annealing temperature varied from 100 to 700°C and the heating rate was 10°C/min. The temperature effects on the composition and particles size of Ni-ferrites powders synthesized at 300, 400. 500 and 600°C were investigated using X-ray analysis and transmission electron microscopy. Nanometrics Ni-ferrites powder was produced with less then 20 nm average particles size at 500 C.

Preparation and characteristics of Ni-ferrite powders obtained in the presence of fused salts

This paper describes Ni-ferrite formation in the presence of Li2SO4-Na2SO4 molten salts, and in particular the effects of the raw materials, amount of salts, heating temperature and time on the size and shape of the ferrite powders, as well as on the rate of ferrite formation. The molten salts accelerate ferrite formation and complete ferrite formation is attained at lower temperatures than in solid state reactions. Ferrite powders with two types of shapes are obtained from NiO with different particle sizes and aggregation states; one is similar to the starting Fe2O3 particles and the other has an octahedral crystal habit. The difference follows from the different dissolution rates of Fe2O3 and NiO. Growing particles in molten salts have a crystal habit, but the most stable particle shape is rounded.