α-Fe2O3 Nanowires Research Articles

Enhanced hydrogen sulfide sensing properties of Pt-functionalized α-Fe2O3 nanowires prepared by one-step electrospinning

Pure α-Fe2O3 nanowires (NWs) and 0.5, 1 and 3mol% Pt-functionalized α-Fe2O3 nanowires have been successfully synthesized via simple homotaxial electrospinning methods. The nanostructures and morphologies of the as-obtained nanowires were characterized through various experimental techniques. The morphologies of the as-obtained samples and the chemical state of Pt element were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectrum (XPS). Furthermore, comparative gas sensing investigations about the series of Pt-functionalized α-Fe2O3 nanowires and pure α-Fe2O3 nanowires were performed to demonstrate the superior sensing properties of the Pt-functionalized samples. According to the experimental results, the sensor with 1mol% Pt-functionalized α-Fe2O3 nanowires exhibited the highest response (157–10ppm H2S) and noticeable selectivity at 175°C, which could be attributed to the chemical sensitization (catalytic oxidation) of Pt on α-Fe2O3, and the porous structure of the nanowires.

Thermal oxidation synthesis of crystalline iron-oxide nanowires on low-cost steel substrates for solar water splitting

Iron-oxide and in particular its crystallographic phase hematite (α-Fe2O3) is a promising candidate for non-toxic, earth abundant and low cost photo-anodes in the field of photo-electrochemical water splitting. We report here on the synthesis of α-Fe2O3 nanowires by thermal oxidation of low-cost steel substrates. Nanowires grown in this manner exhibit often a blade-like shape but can also possess a wire-like geometry partly decorated at their tip with an iron-rich ellipsoidal head consisting also of crystalline iron-oxide. We show furthermore that these ellipsoidal heads represent suitable growth sites leading in some cases to an additional growth of so-called antenna nanowires. Besides nanowires also nanoflakes were frequently observed at the surface. We discuss the influence of the oxidation temperature and other synthesis parameters as well as dispute the current growth models. Finally, we show that our α-Fe2O3 nanostructures on steel are also photo-electrochemically active supporting in principle their use as photo-anode material.

Calcination-temperature-dependent gas-sensing properties of mesoporous α-Fe2O3 nanowires as ethanol sensors

The mesoporous α-Fe2O3 nanowires (NWs) were successfully synthesized by changing the calcination temperature from 550 to 750 °C (marked NWs-550, NWs-650 and NWs-750) via using SBA-15 silica as the hard templates with the nanocasting method. The characterization results indicated that the bandgap of the as-prepared samples hardly changed and the high BET surface areas changed a little with the calcination temperature from 550 to 750 °C. Mesoporous α-Fe2O3 NWs had been found to possess the remarkable gas-sensing performance to ethanol gas. The gas-sensing behavior indicated that α-Fe2O3 NWs-650 exhibited the higher response than that of α-Fe2O3 NWs-550 and α-Fe2O3 NWs-750. The calcination-temperature-dependent gas-sensing properties were mainly attributed to the competition of surface defects and body defects by the crystallization temperature. The lower calcination temperature could create more surface defects to improve the gas-sensing response, while the higher temperature would reduce the body defect and make the charge carriers transport easily. As the result, the suitable calcination temperature was desired to optimize the defects of nanostructures to improve the gas sensitivity.

Localized Synthesis of Iron Oxide Nanowires and Fabrication of High Performance Nanosensors Based on a Single Fe2 O3 Nanowire.

A composed morphology of iron oxide microstructures covered with very thin nanowires (NWs) with diameter of 15-50 nm has been presented. By oxidizing metallic Fe microparticles at 255 °C for 12 and 24 h, dense iron oxide NW networks bridging prepatterned Au/Cr pads are obtained. X-ray photoelectron spectroscopy studies reveal formation of α-Fe2 O3 and Fe3 O4 on the surface and it is confirmed by detailed high-resolution transmission electron microscopy and selected area electron diffraction (SAED) investigations that NWs are single phase α-Fe2 O3 and some domains of single phase Fe3 O4 . Localized synthesis of such nano- and microparticles directly on sensor platform/structure at 255 °C for 24 h and reoxidation at 650 °C for 0.2-2 h, yield in highly performance and reliable detection of acetone vapor with fast response and recovery times. First nanosensors on a single α-Fe2 O3 nanowire are fabricated and studied showing excellent performances and an increase in acetone response by decrease of their diameter was developed. The facile technological approach enables this nanomaterial as candidate for a range of applications in the field of nanoelectronics such as nanosensors and biomedicine devices, especially for breath analysis in the treatment of diabetes patients.

The enhancement of the magnetic properties of α-Fe2O3 nanocatalyst using an external magnetic field for the production of green ammonia

Hematite nanocatalysts with improved magnetic properties were synthesized using electrical resistive heating under the presence of a magnetic field and a gaseous environment containing oxygen and nitrogen. The synthesis temperature was varied from 500–850°C in the absence and presence of a static magnetic field of 0.25T. VSM hysteresis results showed that there is a clear improve in the magnetic properties of the nanocatalysts when an external magnetic field was used during the synthesis. It also showed that the nanowires amongst other shapes hold the highest saturation magnetization value. The produced α-Fe2O3 nanocatalysts were used for ammonia synthesis under an external magnetic field strength ranging between 0.4–2T. Correspondingly, (24.174mmolh−1gcat−1) ammonia was yielded by applying an external magnetic field of 1.2T and using the α-Fe2O3 nanowires synthesized at 700°C with the highest saturation magnetization value of 189.43emu/g.

Deformations of the α-Fe2O3 rhombohedral lattice across the Néel temperature

High-resolution synchrotron radiation powder diffraction patterns of α-Fe2O3 measured between room temperature and 1100 K, i.e. above the Néel temperature T N = 950 K, have been analyzed. The integral breadths of the Bragg peaks show a hkl-dependent anisotropy, both below and above T N. This anisotropy can be quantitatively described by using a statistical peak-broadening model [Stephens (1999). J. Appl. Cryst. 32, 281]. Model calculations show that the rhombohedral α-Fe2O3 lattice is deformed and the deformation leads to a monoclinic lattice with the unique monoclinic axis along the hexagonal [110] direction both below and above T N. The monoclinic symmetry of bulk α-Fe2O3 is compatible with α-Fe2O3 nanowire growth along the [110] direction reported in Fu et al. [Chem. Phys. Lett. (2001), 350, 491].

Nanocasting synthesis, magnetic interaction and gas-sensing properties of dispersed, bundled and assembled α-Fe2O3 nanowires

The α-Fe2O3 (hematite) nanowires were synthesized with the nanocasting route using the hard template of SBA-15, and then were divided into the dispersed α-Fe2O3 nanowires (DNWs), bundled α-Fe2O3 nanowires (BNWs) and assembled α-Fe2O3 nanowires (ANWs) by the centrifugation technique. All samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm, UV–vis spectrum and superconducting quantum interference device (SQUID). All results indicated that all synthesized samples with the same nanowires diameter presented the much different interwires distance. Magnetic measurements showed that Ms of α-Fe2O3 ANWs and BNWs was smaller than that of α-Fe2O3 DNWs, while Hc and TC were larger than α-Fe2O3 DNWs. These should be attributed to the magnetic interaction from the surface spin coupling for the smaller interwires distance between the neighboring nanowires of α-Fe2O3 ANWs and BNWs. The gas-sensing behavior indicated that the as-obtained α-Fe2O3 ANWs, BNWs and DNWs exhibited the excellent gas-sensing performance to ethanol, resulting from the wide bandgap of α-Fe2O3 nanowires. Furthermore, it was proved that the sensitivity increased with the specific surface area, and the sensitivity of α-Fe2O3 DNWs based sensors was higher than those of α-Fe2O3 BNWs and ANWs. The α-Fe2O3 ANWs, BNWs and DNWs based sensors presented the rapid response and recovery times (only 7 s and 1 s) and the excellent gas sensitivity at low concentration.

Green urea synthesis catalyzed by hematite nanowires in magnetic field

The catalytic activity of hematite (α-Fe2O3) nanowires under the influence of magnetic field on urea synthesis is considered green. The adsorption and subsequent dissociative reaction of hydrogen, nitrogen and carbon dioxide gases on the α-Fe2O3 (111) nanowires were investigated using the density functional theory (DFT) method. The average adsorption energy is −4.12kcal/mole at different sites. The adsorption of gases resulted in a difference in density and net spin of electrons from 68 to 120 and 0–21 respectively. In addition, it induces magnetic moment value of 36.33µB, which confirms the enhanced magnetic behaviour of hematite. α-Fe2O3 nanowires (NWs) synthesized by heating iron wire in a box furnace at (750−800)°C and as synthesized α-Fe2O3 nanoparticles (NPs) were received to use as a catalyst in the magnetic reaction of urea synthesis. X-ray Diffractometer (XRD) confirms the peaks of rhombohedral structure of α-Fe2O3 and Raman spectrum analyses confirms the α-Fe2O3 peaks at 410cm−1, 500cm−1 and 616cm−1. The needle-like shape of hematite nanowires with length ranging from 16–25) μm and diameter from 74 to 145nm confirmed by Field emission scanning electron microscopy (FESEM). The magnetic properties of the nanowires exhibited different levels of saturation magnetization, for α-Fe2O3 perpendicularly aligned direction (13.18emu/g) and random direction (10.73emu/g). Urea synthesis was done under magnetic field ranges from 0.0 to 2.5T. The activation energy of α-Fe2O3 NWs for urea production is lower than NPs in the range of 0–1T, whereas it is reversed for higher magnetic induction values. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of urea at the peaks of 1690–1600cm−1. This green urea employing magnetically induced method could be a contender to the Haber-Bosch process currently used by the current industry which utilizes high temperature and high pressure.

The effect of saturation magnetization of nanocatalyst and oscillating magnetic field for green urea synthesis

Hematite and cupric oxide nanowires have been synthesized using the oxidation method for green urea production. Hematite nanowires were obtained by the oxidation of an iron wire at a temperature of 650°C and ambient pressure in the presence of N2 and O2 gases. Cupric oxide nanowires were obtained by the same method at 700°C, using a copper wire. The X-ray diffraction results show the formation of rhombohedral structure of α-Fe2O3 and monoclinic phase of CuO. FE-SEM results reveal the formation of nanowires with dimensions ranging between 5–15µm and 4–12µm in length and a diametere ranging between 50–150nm and 50–250nm for α-Fe2O3 and CuO respectively. The VSM results show that the saturation magnetization values for hematite and cupric oxide were 132.8700 and 0.0124emu/g, respectively. The nanowires were used as catalyst for green urea synthesis in the presence of an oscillating and a static magnetic fields. The use of nanocatalyst with high saturation magnetization gives a higher yield of urea due to the increase in the singlet to triplet conversion. The highest yield of urea 11243ppm was achieved by applying an oscillating magnetic field of frequency 0.5MHz and using α-Fe2O3 nanowires as nanocatalyst.

Electrochemical analysis of nanostructured iron oxides using cyclic voltammetry and scanning electrochemical microscopy

Iron oxides in general and especially hematite, α-Fe2O3, have become promising materials for the alkaline water electrolysis and photoelectrochemical water splitting, respectively. In the present study electrocatalytic electrodes with a thin film of α-Fe2O3 and with vertically aligned α-Fe2O3 nanowires were prepared. Cyclic voltammograms of the α-Fe2O3 nanowires revealed differences including a series of three unreported cathodic signals when compared to previously published voltammograms for polycrystalline iron oxides. The generation-collection mode of scanning electrochemical microscopy (SECM) using nanostructured Pt microdisc probes was exploited to detect soluble reaction products formed at the voltammetric peaks of the α-Fe2O3 electrode. SECM tip-substrate voltammetry unexpectedly showed that the reduction of FeVI to FeIII on the cathodic sweep is accompanied by significant O2 evolution.

Atomic Structural Evolution during the Reduction of α-Fe2O3 Nanowires.

The atomic-scale reduction mechanism of α-Fe2O3 nanowires by H2 was followed using transmission electron microscopy to reveal the evolution of atomic structures and the associated transformation pathways for different iron oxides. The reduction commences with the generation of oxygen vacancies that order onto every 10th [Formula: see text] plane. This vacancy ordering is followed by an allotropic transformation of α-Fe2O3 → γ-Fe2O3 along with the formation of Fe3O4 nanoparticles on the surface of the γ-Fe2O3 nanowire by a topotactic transformation process, which shows 3D correspondence between the structures of the product and its host. These observations demonstrate that the partial reduction of α-Fe2O3 nanowires results in the formation of a unique hierarchical structure of hybrid oxides consisting of the parent oxide phase, γ-Fe2O3, as the one-dimensional wire and the Fe3O4 in the form of nanoparticles decorated on the parent oxide skeleton. We show that the proposed mechanism is consistent with previously published and our density functional theory results on the thermodynamics of surface termination and oxygen vacancy formation in α-Fe2O3. Compared to previous reports of α-Fe2O3 directly transformed to Fe3O4, our work provides a more in-depth understanding with substeps of reduction, i.e., the whole reduction process follows: α-Fe2O3 → α-Fe2O3 superlattice → γ-Fe2O3 + Fe3O4→ Fe3O4.

Topotaxial growth of α-Fe2O3 nanowires on iron substrate in thermal annealing method

A detail cross-sectional transmission electron microscopy of as-grown α-Fe2O3 nanowire sample, synthesized on iron substrate by thermal annealing method, was carried out to understand the mechanism of growth in this system. Iron undergoes sequential oxidation to form a layered structure of Fe/FeO/Fe3O4/α-Fe2O3. α-Fe2O3 nanowires grow on to the top of α-Fe2O3 layer. It was found that subsequent oxide layers grow topotaxially on the grains of iron, which results in a direct orientation relationship between the α-Fe2O3 nanowire and the parent grain of iron. The results also showed that the grains of α-Fe2O3 layer, which were uniquely oriented in [110] direction, undergo highly anisotropic growth to form the nanowire. This anisotropic growth occurs at a twin interface, given by (−11−1), in the α-Fe2O3 layer. It was concluded that the growth at twin interface could be the main driving factor for such anisotropic growth. These observations are not only helpful in understanding the growth mechanism of α-Fe2O3 nanowires, but it also demonstrates a way of patterning the nanowires by controlling the texture of iron substrate.

Wide bandgap mesoporous hematite nanowire bundles as a sensitive and rapid response ethanol sensor

In this study, α-Fe2O3 nanowires were synthesized using mesoporous SBA-15 silica as the hard templates with the nanocasting method, and then mesoporous α-Fe2O3 nanowire bundles (NWBs) were separated from the well-dispersed α-Fe2O3 nanowires (NWs) by the centrifugation technique. Both samples were characterized by x-ray diffraction, transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherm and UV-vis spectra. All results indicated that the α-Fe2O3 NWBs with mesoporous structure presented a higher BET surface area (95 m2 g−1) and wider bandgap (2.08 eV) than those of α-Fe2O3 NWs (32 m2 g−1 and 1.91 eV). The bandgap of α-Fe2O3 NWBs was in accordance with the bulk α-Fe2O3, while the BET surface area was much higher. The results from the gas-sensing measurement revealed that the α-Fe2O3 NWBs based gas sensor exhibited a high sensitivity of 21.7, fast response-recovery of 7.5 s and 1 s, and good selectivity to ethanol at 340 °C. The sensitivity (21.7) for ethanol of α-Fe2O3 NWBs was much better than that of the α-Fe2O3 NWs (12.2), which should be attributed to the higher BET surface area and wider bandgap of α-Fe2O3 NWBs.

Relationship of magnetic behavior and surface spin coupling in Hematite nanowires bundles

Hematite (α-Fe2O3) nanowires were synthesized using mesoporous SBA-15 silica as the hard templates, and then the well-dispersed α-Fe2O3 nanowires (NWS) were separated from the ordered α-Fe2O3 nanowires bundles (NWBS) by the centrifugation technique. X-ray diffraction (XRD), transmission electron microscopy (TEM) and surperconducting quantum interference device (SQUID) were used to characterize the microstructure and magnetic properties of the as-prepared samples. All results indicated that the α-Fe2O3 NWS and NWBS with the different interwires distance presented the same diameter for nanowires, which was possible to reveal the exchange interaction between α-Fe2O3 NWBs. Both samples showed ferromagnetism and α-Fe2O3 NWS presented superparamagnetism at high temperature. The magnetic results indicated the surface spin between the neighboring nanowires of α-Fe2O3 NWBs coupled each other. The saturation magnetization of α-Fe2O3 NWBS was lower than that of α-Fe2O3 NWS, while the coercivity and Curie temperature were larger. It was concluded that the surface spin coupling could weaken the surface effect on the magnetic properties for nanostructures.

Flat-panel light source with lateral-gate triode structure and urchin-like α-Fe2O3 microspheres as field emitters

Urchin-like α-Fe2O3 microspheres (radial α-Fe2O3 nanowires on α-Fe2O3 microspheres) are used as field emitters for a flat-panel lighting device with a lateral-gate-electrode structure. The urchin-like α-Fe2O3 microspheres are in situ grown on the cathode electrode via thermal oxidation at 350 °C for 12 h after the screen-printing of pattern Fe microspheres on the cathode electrode. The lateral-gate triode structure comprises an Ag cathode and a pair of Ag gate electrodes screen-printed laterally on both sides of the cathode. The role of the gate electrodes is to enhance the emission current and increase luminance uniformity and that of the anode electrode is to control the luminance intensity. The radial nanowire emitters on the spheres ensure good field emission performance without any pretreatment and in situ growth of the material enhances the contact between the electrode and the material. The microspheric emitters and the lateral-gate structure, which covers a small part (4.32%) of the printed area over the entire panel (3.5 cm × 5 cm) leads to, high luminance, excellent luminance uniformity and tunable luminance characteristics of the field-emission light source. A maximum luminance of 8330 cd/m2 and a luminance uniformity of 92.4% are achieved with a gate voltage of 500 V, an anode voltage of 4000 V, and the anode current of 1.32 mA.

Structure versus properties in α-Fe2O3 nanowires and nanoblades

We report structure/property relationships in bicrystalline α-Fe2O3 nanowires (NWs) and nanoblades (NBs), synthesized by thermal oxidation of iron foils with different surface roughness. The electrical properties of individual nanostructures were studied by in situ transmission electron microscopy. Current–voltage (I–V) measurements using gold electrodes showed that a Schottky contact forms between α-Fe2O3 NWs whereas an ohmic contact forms between α-Fe2O3 NBs. The difference in transport properties is attributed to the existence of oxygen vacancies in the coincidence-site-lattice boundary region of α-Fe2O3 NBs. Magnetic measurements indicate that the temperature-dependent zero-field-cooled magnetization rises more rapidly near the Morin transition temperature for α-Fe2O3 NBs than that for NWs. The distinct magnetic properties of the NBs are ascribed to the enhanced magnetic order induced by the structural order in the two-dimensional NBs. These α-Fe2O3 NBs are promising building blocks for electronic and magnetic devices since their 2D geometries facilitate integration into devices with realistic pathways to manufacturing. In addition, our study shows that boundary engineering is an effective approach for tailoring the physical properties of nanomaterials.

Enhanced Performance of Photoelectrochemical Water Splitting with ITO@α-Fe2O3 Core-Shell Nanowire Array as Photoanode.

Hematite (α-Fe2O3) is one of the most promising candidates for photoelectrodes in photoelectrochemical water splitting system. However, the low visible light absorption coefficient and short hole diffusion length of pure α-Fe2O3 limits the performance of α-Fe2O3 photoelectrodes in water splitting. Herein, to overcome these drawbacks, single-crystalline tin-doped indium oxide (ITO) nanowire core and α-Fe2O3 nanocrystal shell (ITO@α-Fe2O3) electrodes were fabricated by covering the chemical vapor deposited ITO nanowire array with compact thin α-Fe2O3 nanocrystal film using chemical bath deposition (CBD) method. The J-V curves and IPCE of ITO@α-Fe2O3 core-shell nanowire array electrode showed nearly twice as high performance as those of the α-Fe2O3 on planar Pt-coated silicon wafers (Pt/Si) and on planar ITO substrates, which was considered to be attributed to more efficient hole collection and more loading of α-Fe2O3 nanocrystals in the core-shell structure than planar structure. Electrochemical impedance spectra (EIS) characterization demonstrated a low interface resistance between α-Fe2O3 and ITO nanowire arrays, which benefits from the well contact between the core and shell. The stability test indicated that the prepared ITO@α-Fe2O3 core-shell nanowire array electrode was stable under AM1.5 illumination during the test period of 40,000 s.

Ionic Liquid Based Synthesis of α-Fe2O3 nanocrystallite and Its Application in Lithium Ion Battery

Hematite (α-Fe2O3), which is the most stable iron oxide with n-type semiconducting properties under ambient conditions, is of great scientific and technological importance. Especially in the energy storage field, it has attracted considerable interest because of their low cost and excellent electrochemical properties in rechargeable lithium ion batteries (LIBs).[1,2] Stimulated by both the promising applications of iron oxides and the novel properties of nanoscale materials, considered efforts have been made in the synthesis of α-Fe2O3 nanoparticles, nanorods, nanowires and nanotubes. However, most of the synthesis approaches are complicated and beyond the large scale production. Herein, we report the preparation of α-Fe2O3 nanocrystalline using ionic liquid (BMIBF4) as morphology tuning agent through a facile, one step solvethermal method. The role of ionic liquid (IL) played in the preparation process was investigated and a possible formation mechanism was proposed. Fig. 1 showed the morphologies of the products with and without ionic liquid in the reaction system. From which, we can see that uniform nanocrystallites were obtained with the addition of ionic liquid, demonstrating it a good morphology controllable agent for the products. Fig.2 showed that ionic liquid did not affect the phase of the products.A series of experiments about the formation process ofα-Fe2O3 nanocrystallites have been carried out by changing the reaction temperature and time. The results showed that the product obtained at 180 °C for 36 hours exhibited the most homogenous morphology and the best dispersibility. The electrochemical performances of them were examined in rechargeable lithium batteries. Due to the poor conductivity of them, graphene nanosheets (GNSs) were used to composite with them to improve the electrochemical performance. As Fig.3 demonstrated, α-Fe2O3 nanocrystallites were successfully dispersed on the surface of GNS (Fig. 3a,b). It exhibited an initial discharge capacity as high as 1900 mAh g-1, which is much higher than that of primitiveα-Fe2O3 electrode of 1600 mAh g-1in Fig. 3c.Figure 1. SEM image (a) and TEM image (b) of the product obtained at 180°C for 36 h with IL; SEM image (c) and TEM image (d) of the product obtained at 180°C for 36 h without IL.Figure 2. XRD patterns of the product obtained at 180°C for 36 h with and without IL.Figure 3. SEM images (a,b) of GNS supportedα-Fe2O3 nanocrystallites and the first charge-discharge curves of the electrodes at a current density of 50 mA g-1 in LIBs (c).

Syntheses and Structural Control of Silicide, Oxide and Metallic Nano-Structured Materials

The structural control and morphological modification of a series of silicide, oxide and Ag metal nanostructures have been further discussed with reviews of nanostructure syntheses, such as CrSi2 nanowire bundles dendrites, MoSi2 nanosheets, α-Fe2O3 nanowires nanobelts, CuO/Cu2O nanowire axial heterostructures, ZrO2/SiOx and CrSi2/SiOx core/shell nanowires. In addition, the syntheses of Ag three-dimensional dendrites, two-dimensional dendrites, two-dimensional fractal structures, particles and nanowires also were discussed. Moreover, the structural and morphological properties of the nanostructures were examined. The structural control and morphological modifications of the nanostructures have been successfully demonstrated by the appropriate thermal treatments with specific starting materials. A large volume of silicide nanowire bundles, large area of oxide nanowire arrays and large area Ag nanostructure coatings were successfully fabricated.

Growth of hematite nanowire arrays during dense pentlandite oxidation

A simple synthesis method is proposed for producing aligned and uniform single-crystal one-dimensional hematite (α-Fe2O3) nanostructures on pentlandite. Pentlandite is the most common terrestrial iron-nickel sulfide and the principal ore mineral of nickel. In this study, a pentlandite sample was synthesized from pure components Fe, Ni and S. Oxidation makes the chemical potential of iron reduce more than that of nickel. Iron migrated rapidly to the surface of dense pentlandite and was oxidized preferentially to form an oxide layer. Several micrometers long α-Fe2O3 nanowires grown along the [110] direction were achieved. The ordered oxygen vacancies which lie parallel to the growth direction were observed. Hematite (α-Fe2O3) and magnetite including Ni (NixFe3−xO4) are major components of the oxide layer. Three kinds of morphology are included in this layer: nanowires, dense and porous oxides. The Ni-rich pentlandite coexists with NiS, hexagonal pyrrhotite (Fe1−xS) and/or godlevskite (Ni7S6). This work provides a new strategy to inexpensively and efficiently synthesize nanostructures directly from ore minerals.