Two-step Reaction Method Research Articles

Development of Air–Ti Gas-Surface Reaction Mechanisms and Rate Calculations

Gas-surface reaction mechanisms and rates were developed for an air–titanium surface to support finite-rate catalytic surface reaction models used in computational fluid dynamics. For the surface dissociation/recombination reactions, a two-step reaction method was applied based on the assumption that two atoms must be positioned in adjacent cells to recombine. Transition state theory was used to calculate the surface reactions for adsorbed diatomic molecules to dissociate to the adjacent unit cell or atoms located in the adjacent cells to recombine into diatomic molecules. For the second step, atoms located in the adjacent cells are allowed to further dissociate to another cell (total separation), or totally separated atoms recombine into the adjacent cells. A stochastic gas-surface kinetics simulation code, STOKIN, was developed to simulate gas-surface reactions and to calculate the equilibrium constants of second molecular dissociation ⇌ recombination processes. Thermodynamic properties of the adsorbates (enthalpies, entropies, and heat capacities) were calculated using density functional theory along with statistical mechanics assuming no rotational and translational contributions to the entropies and heat capacities due to the adsorbates’ inability to freely move or rotate on the surface.

O2-H2O2 high-efficient co-oxidation of carbohydrate biomass to formic acid via Co3O4/C nanocatalyst

The conversion of biomass to chemicals/fuels has emerged as a valuable solution that offers both environmental and economic benefits, with the transformation of carbohydrate into formic acid garnering escalating scholar interest. However, the relative limited efficiency of catalyzed-oxidation or expensive cost of H2O2 and alkali in wet hydrothermal oxidation impose limitations on industrialization. This paper proposed a new idea for formic acid production by O2-H2O2 co-oxidation of carbohydrate. A two-step reaction method was developed, where the initial step is engineered to regulate the carbon chain cleavage of carbohydrates to augment the production of active intermediate. Oxygen was employed in the subsequent step as effective oxidant through free radical mechanism, resulting in a formic acid yield of 82.6%. Theoretical calculation, intermediates detection and real time EPR confirmed the reaction mechanism. Finally, the universality of the reaction was verified by using disaccharides and polysaccharides such as cellulose as substrates.

Controllable reduction of absorbance and two-step reaction for 3D-printed SiC ceramics with micron-level periodic structure

Digital light processing (DLP) is increasingly widely used to manufacture high-precision complex structural ceramic components quickly and efficiently. However, due to the high absorbance of silicon carbide (SiC) micron fine powder and the high refractive index difference between the powder and the photosensitive resin, it is extremely challenging to DLP print SiC with high precision complex structure. Here, the surface of SiC powder was coated with SiO2 nano-layer of different thickness by controllable oxidation coating method, thus realizing the photocurable printing of SiC@SiO2 green bodies with structural precision up to 80 μm. Through the two-step reaction method of carbothermal reduction combined with gas-phase siliconizing (GSI), not only the SiO2 coated layer was effectively removed, but also the reaction-bonded silicon carbide (RB-SiC) ceramics with 80–300 μm periodic structure was successfully realized. Ultimately, the comprehensive performance of the RB-SiC samples is effectively improved by chemical vapor infiltration of silicon carbide (CVI-SiC). It is noteworthy that the maximum elastic modulus and hardness of the ultima SiC specimens (RB-SiC@CVI-SiC) are as high as 394.599 GPa and 50.241 GPa, respectively. Shockingly, the nanomechanical properties of postgenetic RB-SiC bound to initial α-SiC on the cross-section of ultima specimens were much higher than those of CVI-SiC on the surface. This study fills the gap that liquid-phase siliconizing (LSI) or pyrolysis process could not achieve high-performance SiC ceramics with micron-level periodic structure.

Cerium-doped nickel phosphide (Ni2P): Highly efficient electrocatalyst for hydrogen evolution reaction

Here, cerium-doped nickel phosphide is introduced as a novel electrocatalyst for HER. Nickel phosphide doped with different cerium contents was synthesized by a two-step vapor-solid reaction method. The electrocatalysts were characterized by various physical and electrochemical analyses. The physical characterization results indicated that cerium doping decreased the crystallite size and subsequently the average particle size of pure Ni2P. Also, electrochemical measurements showed that cerium doping generally bettered the performance of pure Ni2P in HER by improving its electrochemical characteristics e.g. electrochemical hydrogen adsorption, energy efficiency, number of active sites, intrinsic activity, and charge transfer behavior. The effects of cerium doping were also examined theoretically using density functional theory (DFT) calculations, which provided an in-depth understanding of cerium doping. The optimum amount of cerium dopant was found at 3 %mol where Ce0.03Ni2P with the onset potential of 73.3 mV, and an overpotential of 150.0 mV at a current density of 10 mAcm2, and Tafel slope of 76.7 mVdec. in 1.0 M KOH showed the highest activity. Such a high activity, along with stable and durable performance, introduces Ce0.03Ni2P as an efficient electrocatalyst for HER.

One-pot two-step cross-dehydrogenative-coupling polycondensation for synthesis of tetrafluorobenzene-based conjugated polymer

Polycondensation of 1,2,4,5-tetrafluorobenzene (1) with 3,3′-dihexyl-2,2′-bithiophene via Pd/Ag dual-catalyzed cross-dehydrogenative coupling was examined. In situ deprotonation-metalation of 1 with Ag salt proceeded smoothly at 25 °C, and the subsequent transmetalation with a Pd catalyst provided a cross-coupling product. The sequential one-pot two-step reaction method effectively suppressed undesired homo-coupling defects during polymerization. The obtained highly regioregular polymer had a packing structure and exhibited strong fluorescence in the film state, which was also evaluated for use as an emitting material in organic light-emitting diodes.

Synthesis of Ti3C2T x /MnO2 composites for synergistic catalytic/photothermal-based bacterial inhibition.

Human inflammation caused by bacterial infection threatens global public health. The abuse of antibiotics often leads to the development of drug resistance in bacteria. To address this issue, nanozymes with peroxidase-like (POD-like) activity have often been reported for bacteriostasis with the assistance of catalytic substrate hydrogen peroxide (H2O2). However, it is difficult to achieve efficient bactericidal outcomes only through exertion of the POD-like activity of nanozymes. Here, MnO2 loaded Ti3C2T x (Ti3C2T x /MnO2) was prepared by a two-step reaction method, in which MnO2 showed high oxidase-like (OXD-like) activity to elevate the levels of reactive oxygen species (ROS) without H2O2 and Ti3C2T x exhibited high photothermal conversion efficiency to induce hyperthermia. Thus, the obtained Ti3C2T x /MnO2 realized synergistic catalytic/photothermal-based bacterial inhibition, including for Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and methicillin-resistant Staphylococcus aureus. Importantly, Ti3C2T x /MnO2 with near-infrared light irradiation successfully promoted Staphylococcus aureus-infected wound healing in mouse models, representing an alternative treatment to fight against bacterial infection.

PS-C23-2: GUT MICROBIOTA AND SUBCLINICAL CORONARY ARTERY CALCIFICATION IN A GENERAL POPULATION OF JAPANESE MEN

Objective: The gut microbiota of patients with coronary artery disease is being shown to differ from that of healthy individuals. However, it is unclear whether it is altered before the onset of the disease. The aim of this study is to investigate the association between gut microbiota and subclinical coronary artery calcification (CAC) in general Japanese men. Design and method: We randomly selected men from the general Japanese population, who underwent computed tomography and gut microbiology tests between 2010 and 2016. Among participants who underwent both tests, excluding those with myocardial infarction history, leaving a sample size of 653 participants in the analysis. DNA was extracted from fecal samples, the bacterial 16S ribosomal RNA gene was amplified using a two-step tail polymerase chain reaction method, and DNA sequencing was performed on a MiSeq System, followed by data analysis using QIIME2 algorithm. Agatston scores > = 100 was defined as the presence of CAC. LEfSe identified different taxa between with and without CAC, and Poisson regression analysis examined them when logarithmic LDA score was > = 3.5 and phylogenetic levels > = 3. Each taxon was ranked in quartiles (Q1–4) and the relative risk (RR) of CAC was calculated. Adjustment factors were age, smoking, drinking, body mass index, use of medication to treat hypertension, dyslipidemia, or diabetes, and history of cardiovascular events. Sensitivity analysis also delimited Agatston scores by 0 or 10. Results: Mean age of the participants was 68.3 years, and 215 (32.9%) participants had a CAC score > = 100. Relative abundance of phylum level was 55.1% and 53.2% for Firmicutes, and 32.4% and 34.3% for Bacteroidetes among participants with versus without CAC score > = 100, respectively. Among taxa identified by LEfSe, Poisson regression analysis revealed the genus Bacteroides was inversely associated and genus Ruminococcus was positively associated with CAC after multivariable adjustment (Bacteroides: RR [95%CI] = 0.62 [0.45–0.86] (Q4) vs. ref (Q1)) (Ruminococcus: RR [95%CI] = 1.69 [1.25–2.29] (Q4) vs. ref (Q1)). Sensitivity analysis showed similar results. Conclusions: The ratio of Firmicutes to Bacteroidetes was high from the beginning of atherosclerosis. Higher genus Ruminococcus and lower genus Bacteroides were associated with a CAC score > = 100 in general Japanese men.

Torrefaction of low-value agro-industrial wastes using macro-TGA with GC-TCD/FID analysis: Physicochemical characterization, kinetic investigation, and evolution of non-condensable gases

Two low-value agro-industrial residues, passion fruit peel waste (PF) and pineapple peel waste (PA), were considered in this study as feedstocks to produce solid biofuels by torrefaction. The experiments were conducted in a macro-TGA with GC-TCD/FID analysis to investigate their torrefaction characteristics. The GC-TCD/FID analysis allowed quantifying the non-condensable gases, including CO, CO2, CH4 and H2. The impacts of pretreatment with torrefaction on the physicochemical properties were investigated by using proximate analysis, ultimate analysis, and calorific values. The torrefaction of PF and PA was investigated at three different temperatures (200, 250, and 300 °C) and two residence times (15 and 60 min). The torrefaction pre-treatment led to higher levels of elemental carbon, fixed carbon, HHV and energy density than in the raw biomass. Experimental results showed that the most favorable torrefaction condition for producing a solid biofuel with a high energy density is a moderate temperature of 250 °C and 15 min of residence time. Two models were applied to the torrefaction kinetics of the two agro-industrial wastes: one with the one-step method and the other with the two-step method. The two-step reaction method was the most appropriate for describing the torrefaction behavior of the two agro-industrial wastes in all conditions studied. As determined by the two-step reaction method, the torrefaction activation energies ranged from 17.9 to 199.9 kJ mol−1 for PF and 5.3–84.0 kJ mol−1 for PA. Findings from this study are potentially valuable for the design of large-scale equipment for the torrefaction of PF and PA residues.

Syntheses, in vitro, and in silico studies of rhodanine-based schiff bases as potential α-amylase inhibitors and radicals (DPPH and ABTS) scavengers.

A two-step reaction method was used to synthesize a series of rhodanine-based Schiff bases (2-33) that were characterized using spectroscopic techniques. All compounds were assessed for α-amylase inhibitory and radical scavenging (DPPH and ABTS) activities. In comparison to the standard acarbose (IC50 = 9.08 ± 0.07µM), all compounds demonstrated good to moderate α-amylase inhibitory activity (IC50 = 10.91 ± 0.08-61.89 ± 0.102µM). Compounds also demonstrated significantly higher DPPH (IC50 = 10.33 ± 0.02-96.65 ± 0.03µM) and ABTS (IC50 = 12.01 ± 0.12-97.47 ± 0.13µM) radical scavenging activities than ascorbic acid (DPPH, IC50 = 15.08 ± 0.03µM; ABTS, IC50 = 16.09 ± 0.17µM). The limited structure-activity relationship (SAR) suggests that the position and nature of the substituted groups on the phenyl ring have a vital role in varying inhibitory potential. Among the series, compounds with an electron-withdrawing group at the para position showed the highest potency. Kinetic studies revealed that the compounds followed a competitive mode of inhibition. Molecular docking results are found to agree with experimental findings, showing that compounds reside in the active pocket due to the main rhodanine moiety.

Preparation of Al4SiC4 with higher aspect ratio by a novel two-step method

Based on excellent comprehensive properties, aluminum silicon carbide (Al4SiC4) becomes a promising candidate as antioxidant for MgO–C refractories. However, its addition tends to reduce the densification of corresponding refractories due to the plate structure with low aspect ratio, which aggravates the slag corrosion and oxidation during the practical application. Increasing the aspect ratio of Al4SiC4 grains is a feasible approach to fabricate dense Al4SiC4-containing refractories. In this work, a strategy to fabricate Al4SiC4 grains with higher aspect ratio based on a novel two-step solid reaction method was proposed. Firstly, Al4SiC4 seeds was synthesized using Al4C3 and SiC as raw materials at 1700 °C for 6 h. Secondly, the mixture of Al4C3 and SiC with Al4SiC4 seeds added was resintered. The aspect ratio of final Al4SiC4 grains reaches up to 0.44 with the added proportion to be 50%. The growth mechanism follows the Ostwald ripening principle. This work can lay a good foundation for the practical application of Al4SiC4.

Hierarchical ZnO/MXene composites and their photocatalytic performances

MXene with low band gap and excellent metallic conductivity is a novel ultrathin two-dimensional transition metal carbide, and has been widely used as the photocatalytic carrier of semiconductor material. Herein, ZnO/MXene composites were fabricated by a facile two-step chemical reaction method and their structures and photocatalytic performances were investigated systematically. At lower growth temperatures, ZnO particles were dispersed on the Ti3C2 layers whereas ZnO microrods covered the Ti3C2 layers at higher growth temperatures. Especially, ZnO microrods/MXene composites show good photocatalytic performances. Under UV irradiation, about 97.5% Rhodamine B was degraded by the composite within 18 min and retained more than 90% of the photocatalytic efficiency after 7 cycles. Therefore, ZnO microrods/MXene composites can be regarded as a potential candidate for applications in waste water treatment and environmental protection.

Synergistic effect in ultrafine PtNiP nanowires for highly efficient electrochemical hydrogen evolution in alkaline electrolyte

Platinum-based catalysts play an important role in electrochemical hydrogen evolution reaction, which is a renewable and clean way to produce H2. Herein, we have successfully synthesized the ultrafine PtNiP NWs with diameter less than 5 nm via a simple two-step hydrothermal reaction method. Impressively, the PtNiP NWs exhibit one of the best electrocatalytic activity toward HER under alkaline conditions, which can reach current density of 500 mA cm−2 only at the −0.153 V vs RHE with Tafel slop of only 30 mV dec−1. The DFT calculation results show synergistic effect of Pt, Ni and P atoms, where Ni atoms are conducive to the adsorption of H2O and P atoms are helpful for the dissociation of H2O, significantly improving kinetic processes of hydrogen evolution reaction. This work could be instructive and meaningful to design highly efficient and stable HER catalyst in alkaline condition for practical applications.

Preparation of Hexagonal SrMnO₃ High-Quality Target for Magnetron Sputtering.

In recent years, the optical behavior of complex oxides are being increasingly used in light-harvesting applications. Perovskites are promising candidates for photovoltaic, photocatalytic, and optoelectric applications because of tunable band gaps and other unique properties such as fer-roelectricity To study the optical behavior of ferromagnetic-ferroelectric oxides, SrMnO₃ (SMO₃) targets intended for use in magnetron sputtering were prepared using SrCO₃ (99.99%) and Mn₂O₃ (99.99%) powders by a two-step solid reaction method. Experiments were performed at various temperatures to determine the optimum calcination temperature of the SMO₃ powder (1000 °C) and optimum sintering temperature of the prepared target (1300 °C), in an effort to optimize the preparation process of the target at the laboratory scale and reduce the cost of the target by more than 20-fold. Samples of the ground powder were calcined at 800, 1000, 1200, and 1300 °C for 10 h, and the resultant targets were pressed into 1 -in molds after grinding and subsequently sintered at the same temperatures at which the corresponding powders were calcined, i.e., at 800, 1000, 1200, and 1300 °Cfor 48 h. The microcrystalline state of the powders was observed by scanning electron microscopy. The prepared targets were analyzed by X-ray diffraction, and the results were compared with the powder diffraction file card of hexagonal SMO₃ to determine the optimum calcination temperature and sintering temperature of the powder formulation. Finally, the Vickers hardness values of the targets were measured, and the optimum target preparation process was determined.

The effects of different plant extracts on bile salt hydrolase activity of Lactobacillus strains isolated from the gastrointestinal tract of poultry

The bile salt hydrolysis (BSH) enzyme weakens fat metabolism through bile salt deconjugation and reduces poultry performance, in order to cope with the antibacterial properties of the bile. Therefore, reducing the activity of this enzyme through the use of feed additives is probably a promising alternative to antibiotics for improving poultry performance. Plant extracts have long been used as feed additives for promoting poultry growth. In the current experiment, five Lactobacillus strains including Lactobacillus animalis, Lactobacillus acidophillus, Lactobacillus gallinarum, Lactobacillus lactis, and Lactobacillus returi were obtained from the poultry hindgut and were used as the probiotic application. A plate test and two-step enzymatic reaction method were used for deconjugation activity determination of the Lactobacillus strains. Further, four plant extracts (i.e., the aerial parts of Rosemary (Rosmarinus officinalis), Roselle calyx (Hibiscus sabdariffa), Berberis vulgaris root, and Green tea) were examined in terms of BSH enzyme inhibitors using the cell-free extracts as the potential antibiotic alternative. Furthermore, the gallbladders of the broilers were freshly collected from the poultry slaughterhouses, and their contents were extracted. The results showed that all Lactobacillus strains could hydrolyze the taurocholate acid (TCA) and chicken bile salt mixture (CBSM) to unconjugated bile acid. Moreover, ethanolic extracts of B. vulgaris root and Green tea relatively reduced the activity of the BSH enzyme that could potentially be investigated as an appropriate alternative in poultry feed in vivo. In conclusion, all five Lactobacillus strains were resistant to bile salts (i.e. TCA and CBSM) by BSH activity, and the addition of Green tea and B. vulgaris root extracts to the bacterial medium demonstrated inhibitory effects against the BSH enzyme.

Enhanced UV Photoresponsivity of ZnO Nanorods Decorated with Ag2S/ZnS Nanoparticles by Successive Ionic Layer Adsorption and Reaction Method.

Recently, different kinds of energy band structures have been utilized to improve the photoelectric properties of zinc oxide (ZnO). In this work, ZnO nanorods were prepared by the hydrothermal method and then decorated with silver sulfide (Ag2S)/zinc sulfide (ZnS) via two-step successive ionic layer adsorption and reaction method. The photoelectric properties of nanocomposites are investigated. The results show that ZnO decorated with Ag2S/ZnS can improve the photocurrent of photodetectors from 0.34 to 0.56 A at bias of 9 V. With the immersion time increasing from 15 to 60 minutes, the photocurrent of photodetectors increases by 0.22 A. The holes in the valence band of ZnO can be transferred to the valence band of ZnS and Ag2S, which promotes the separation and suppresses the recombination of hole-electron pairs generated in ZnO. Moreover, electrons excited by ultraviolet (UV) light in Ag2S can also be injected into the conduction band of ZnO, which causes the photocurrent to increase more than the ZnO photodetector.

Study on two-step hydrothermal liquefaction of macroalgae for improving bio-oil

In this work, the conversion of Enteromorpha clathrata into bio-oil through hydrothermal liquefaction (HTL) was investigated under different preparation conditions. A two-step reaction method was compared with single-step reaction. At a high temperature, bio-oil produced through the two-step hydrothermal reaction displayed slight changes in yield, but solid residue rate was low. The liquid-to-material ratio of the optimal preparation condition was 40/4 (mL/g). Bio-oil produced in each experiment at this ratio was further analyzed using GC/MS. Furthermore, density functional theory (DFT) quantitative calculation was used in analyzing and proving the possible reaction path of the conversion of furan compounds to aromatic compounds during a direct high-temperature liquefaction process. Results revealed that the two-step method can ensure a high bio-oil yield, while preventing the occurrence of side reactions caused by long-term high-temperature reactions, and improve the bio-oil quality.

Look ahead: understanding cognitive anticipatory processes based on situational characteristics in dynamic traffic situations

Understanding the intentions of other road users increases subjective certainty, improves one's own performance and contributes to enhanced traffic safety. The perception and processing of situational characteristics are pivotal to develop an appropriate situation model as the basis of anticipation in dynamic traffic situations. To gather further insights into the process of situation comprehension, different situational characteristics were tested in a laboratory experiment using urban traffic scenarios. Participants had to indicate, in a two-step reaction method, the initial supposition and certain anticipation of another car merging into their own lane while being cognitively distracted (high versus low). Retrieval cues that enable the formation of causal relations and the development of a coherent mental representation increased the probability of anticipation. Furthermore, different situational characteristics were identified based on distinct underlying processing patterns. Cues that imply a close relationship with the target's behaviour (target cues) are assumed to require fewer inferences. They were less affected by increased cognitive load compared to other situational characteristics (context cues). These findings enhance the understanding of human anticipation and are discussed regarding the methodological approach and the generalisation of the proposed situational cues.

ZnO2 films by successive ionic layer adsorption and reaction method and their conversion to ZnO ones for p-Si/n-ZnO photodiode applications

In this work, we report the properties of ZnO2 thin films deposited at room temperature by a two-step successive ionic layer adsorption and reaction (SILAR) method. The thermal evolution of the as-deposited ZnO2 films into ZnO ones was analyzed by in-situ XRD measurements at different temperatures and thermogravimetric analysis (TGA). The results show that the crystalline phase transition from ZnO2 with cubic structure into ZnO with hexagonal one takes place at around 200 °C. Then, ZnO2 films deposited at different cycles were thermal annealed at 300 °C, 400 °C and 500 °C to obtain hexagonal-structured ZnO films. After analyzing the properties of the ZnO films, they were used to assemble p–n heterostructures employing p-Si wafers. For this, ZnO2 films were deposited by the SILAR method on p-Si wafers and converted to n-ZnO by thermal treatment at 500 °C. The analysis of the electrical current versus voltage curves, in dark and under illumination, of the p-Si/n-ZnO heterostructure shows photodiode characteristics with well-defined current rectification of several orders. The photosensitivity of the assembled photodiode was determined in the visible spectral region. Transient photocurrents were recorded at several voltages under illumination with several light intensities.

In-situ growth of vertically aligned nickel cobalt sulfide nanowires on carbon nanotube fibers for high capacitance all-solid-state asymmetric fiber-supercapacitors

Fiber-supercapacitors (FSCs) are promising power sources for miniature portable and wearable electronic devices. However, the development and practical application of these FSCs have been severely hindered by their low volumetric capacitance and narrow operating voltage. In this work, vertically aligned nickel cobalt sulfide (NiCo 2 S 4 ) nanowires grown on carbon nanotube (CNT) fibers were achieved through an in-situ two-step hydrothermal reaction method. The as-prepared NiCo 2 S 4 @CNT fiber electrode exhibits a high volumetric capacitance of 2332 F cm−3, benefiting from its superior electric conductivity, large surface area, and rich Faradic redox reaction sites. Furthermore, a NiCo 2 S 4 @CNT//VN@CNT (vanadium nitride nanosheets grown on CNT fibers) asymmetric fiber-supercapacitor (AFSC) was successfully fabricated. The device exhibits an operating voltage up to 1.6 V and a high volumetric energy density of 30.64 mWh cm−3. The device also possesses outstanding flexibility as evidenced by no obvious performance degradation under various bending angles and maintaining high capacitance after 5000 bending cycles. This work promotes the practical application of flexible wearable energy-storage devices. © 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences

Preparation of Fe<sub>3</sub>O<sub>4</sub> nanospindle composites and high performance microwave absorption

<p indent="0mm">With the development of electronic communication technology, microwave absorption and shielding are becoming increasingly important in information security, electronic warfare and human body protection. Especially with the rapid development of device integration and multi-band radar technology, the demand for ultra-thin broadband absorbing materials is highly urgent. Magnetic material is easier to achieve impedance matching with air due to their high permeability, which is beneficial to increase the absorbing bandwidth and decrease the thickness of materials. Therefore, it is the first choice for low-frequency microwave absorbing materials. But the microwave permeability is drastically lowered above the resonance frequency, resulting in deterioration of absorbing properties at high frequency, due to Snoek's limit. Therefore, research on magnetic absorbing materials have focused on increasing the permeability and resonance frequency. The Snoek's limit of magnetic materials can be broken by increasing the magnetic anisotropy of materials, including magnetocrystalline anisotropy, shape anisotropy, and surface/interface anisotropy, to increase the permeability and magnetic loss in the radar band. A one-dimensional nanomaterial with strong magnetic anisotropy is proved to be able to significantly increase the natural resonance frequency, thereby enhancing the absorbing properties of the magnetic materials in the high-frequency radar band. In this paper, Fe₃O₄ nanospindle was prepared by a two-step chemical reaction method. First of all, Fe₂O₃ nanospindle was synthesized by hydrothermal method using FeCl₃·6H₂O and NaH₂PO₄·2H₂O as raw materials. Then, Fe₃O₄ nanospindle was obtained by activated carbon reduction in Fe₂O₃ nanospindle. The spindle structure of α-Fe₂O₃ is clearly observed in scanning electron microscope (SEM) image, and Fe₃O₄ holds the same nanostructure and size in transmission electron microscope (TEM) images as α-Fe₂O₃. The X-ray diffraction (XRD) pattern shows that the lattice constants of α-Fe₂O₃ are <italic>a</italic><sc>=5.032 Å</sc> and <italic>c</italic><sc>=13.762 Å,</sc> and Fe₃O₄ is <italic>a</italic><sc>=8.387 Å.</sc> The electromagnetic parameters of the samples were tested by a vector network analyzer in the frequency range <sc>2−18 GHz.</sc> With the increase of concentration of Fe₃O₄, both <italic>ε</italic>′ and <italic>ε</italic>″ increase at the same frequency. The <italic>ε</italic>′ for each sample slightly decreases with increasing frequency owing to the behavior of Debye relaxation. Compared with Fe₃O₄ nanoparticle, the natural resonance frequency of Fe₃O₄ nanospindle shifts to the higher frequency <sc>4.5 GHz</sc> due to strong shape anisotropy, resulting in higher magnetic loss in the range of <sc>2−18 GHz.</sc> The peaks of RL move to lower frequency with the increase in thickness. At the same concentration, Fe₃O₄ nanospindle has better absorbing properties than Fe₃O₄ nanoparticle. The Fe₃O₄ nanospindle composites have a maximum bandwidth of <sc>3.54 GHz</sc> and a minimum reflectivity of <sc>-41 dB</sc> at 70 wt% concentration. Furthermore, the material can achieve good impedance matching at various thicknesses, which is critical for broadband design of microwave absorption. The Fe₃O₄ nanospindle composites achieve strong microwave absorption of 90% covering a wide frequency range of <sc>2.8−17.0 GHz</sc> by designing double-layer structure at 80 wt% concentration. The broadband microwave absorption is mainly associated with the multiple <italic>λ</italic>/4 resonances. In conclusion, Fe₃O₄ nanospindle was prepared by two-step chemical reaction method. The complex permittivity and permeability, and microwave absorption for Fe₃O₄ nanospindle were investigated. Due to the strong magnetic anisotropy, Fe₃O₄ nanospindle exhibits a higher natural resonance frequency <sc>(4.5 GHz)</sc> than Fe₃O₄ nanoparticle, resulting in higher magnetic loss in radar band. Fe₃O₄ nanospindle composites can achieve a maximum bandwidth of <sc>3.54 GHz</sc> and a minimum reflectivity of <sc>-41 dB</sc> with excellent impedance matching. Fe₃O₄ nanospindle composites can achieve strong microwave absorption in the range of <sc>2.7−17.0 GHz</sc> by designing double-layer structure.