Iron-rich Particles Research Articles

A non-invasive technique for sorting of alumina-rich iron ores

This paper describes an Infrared (IR) thermography based technique for sorting of iron ores consisting of alumina-rich particles of relatively low thermal absorptivity as compared to iron-rich particles in the ores. The technique primarily consists of selection of iron ores with Fe compositions ranging from 59 to 69wt.% and alumina (Al2O3) from 0.35 to 8.85wt.%, crushing the ores up to the particle size range around 10mm. The iron ore fines are uniformly heated using heat source of wavelength ranging from 10−2 to 10−6m for a period of time sufficient to create a difference in infrared emission between the ore particles. The thermal image of the heated ores is captured by IR thermography. The alumina-rich iron ore particles are heated up less as the thermal absorptivity of these ores is less than the ores with high iron content. Thus, the alumina-rich iron ore particles can be identified by observing the temperature profile and/or thermal image of these ores. This technique of ore recognition can be useful in improving the feed quality of iron ore to the blast furnace in iron and steel industries by rejecting the alumina-rich ores through modification in the presently existing processes.

Iron-Coated Particles from Condensed Aalenian-Bajocian Deposits: Evolutionary Model (Iberian Basin, Spain)

Condensed intervals provide a framework to study evolution of iron-coated particles. This study examines the ironrich particles contained in the condensed carbonate deposits spanning from uppermost Toarcian to lower Bajocian in the northwestern Iberian Range (northern Spain), to unravel the controls on geochemical changes in the basin by determining variation in mineralogy and REY (rare earth elements and yttrium) as potential predictors of provenance. The articles are composed mostly of the ferrous phyllosilicate berthierine, and by Fe-oxyhydroxide goethite. Depositionally, iron-rich particles occur at specific horizons, and display changes in character, from iron cortoids (Stage 1) in lowest Aalenian sediments, passing to small-sized iron ooids (Stage 2) in early Aalenian strata and to more complex iron-grain aggregates and larger iron ooid–oncoid mixed particles (Stage 3) in the middle–upper Aalenian succession. In the lower Bajocian sediments that represent the most condensed interval, diagenetic processes strongly affected previously iron-coated particles. The genesis of the diverse suite of iron-rich particles is explained by petrographic and mineralogic studies revealing oscillation in redox conditions. Berthierine genesis is linked with suboxic conditions below the water–sediment interface. Subsequent periods of low rates of sediment accumulation allowed the exhumation of particles, and exposing them to oxic conditions that favored goethite formation. Definitive burial led to the development of isopachous circumgranular berthierinic cement rims and dissolution and replacement. Studies of REY and comparison with iron-rich samples of diverse provenance suggest a conceptual model for geochemical evolution of these deposits. The lack of both contemporaneous soil deposits and evidence of subaerial exposure in this arid paleoclimatic setting rule out weathering processes as the main source of iron. Instead, geochemical indexes (Y/Nb and Y/La ratios) suggest that coeval Iberian volcanism was the most plausible iron source. The sedimentological, mineralogical, and chemical attributes of these iron deposits provides proxies to interpret redox and geochemical fluctuations and integrate all the data in an evolutionary model. Variations in REY patterns offer a framework for correlation at both local and subregional scales. Likewise, as this study provides new geochemical data for the Aalenian period, including the Fuentelsaz GSSP worldwide reference section, it enhances knowledge of the evolution of the westernmost Tethyan basins and the significance of widely distributed oolitic ironstones. The data collectively reveal how the REY signature of condensed sediments can be used to obtain detailed information on the geochemical and paleoceanographic conditions of depositional basins.

Iron-rich particles in heavily contaminated multicrystalline silicon wafers and their response to phosphorus gettering

Heavily contaminated multicrystalline silicon wafers have been studied using a scanning synchrotron x-ray fluorescence micro-probe, revealing the presence of iron-rich particles located along grain boundaries. These particles were found to be partially dissolved and removed during phosphorus gettering treatments at 900 or 1000 °C for times of up to 100 min, with increased gettering efficiency at higher temperatures and times. Annealing without the phosphorus gettering layer present at the wafer surfaces resulted in no discernible reduction in particle coverage, showing that the gettering layer is essential in such heavily contaminated wafers, in order to reduce the dissolved Fe concentration below the solubility limit, and therefore allow dissolution to proceed.

Inhibition of self-corrosion in magnesium by poisoning hydrogen recombination on iron impurities

A volumetric measurement of evolved hydrogen is used to quantify rates of corrosion occurring on unpolarized samples of commercially “pure” magnesium immersed in 5% (w/v) aqueous sodium chloride electrolyte. This approach is used to compare rates of uninhibited corrosion with rates occurring in the presence of arsenate and phosphate corrosion inhibitor species dissolved in the experimental electrolyte at concentrations between 10−4 and 10−2moldm−3. The effective cathode in commercially pure magnesium comprises a population of micron and submicron size iron-rich particles widely dispersed in the magnesium matrix. It is shown that arsenate, but not phosphate, acts to poison the hydrogen atom recombination reaction as it occurs on the surface of these cathodic particles. It is shown that because hydrogen evolution is the predominant cathodic process the onset of H-atom recombination poisoning results in greatly reduced rates of magnesium corrosion. Additional mechanistic information regarding the effect of phosphate and arsenate corrosion inhibitors is obtained through systematically investigating the effect of solution pH on inhibitor efficiency.

Characterisation of the coke formed during the metal dusting of low alloy steels

The deposition of carbon from carbonaceous gas mixtures onto the surface of critical components is of particular concern to the petrochemical and chemical industry. In highly carbonaceous atmospheres, a type of corrosion occurs by which the metal (Fe, Ni or Co) disintegrates into a dust of fine metal-rich particles and graphite. This is called metal dusting.In this project, low alloy 1Cr 0.5Mo ferritic steels were exposed to a 50% CO and 50% H2 (vol.%) gas mixture at temperatures between 500°C and 650°C for times up to 100 hours. Metal dusting occurred on all the test samples. Analysis of cross-sections through the samples in a scanning electron microscope (SEM) showed the formation of a cementite layer together with a layer of coke/graphite deposited on the surface after short times. The amount deposited on the alloy’s surface increased with both time and temperature over the temperature range studied.High levels of sample coking were observed after 100 hour tests. Deposited carbon from these tests was characterised by SEM, X-ray diffraction, and (scanning) transmission electron microscopy, S(TEM). TEM of the carbon deposit/coke on selected samples showed a complex convoluted network of carbon filaments with small iron-rich particles at their tips. High resolution TEM was used to study these carbon filaments in greater detail and showed that there were two completely different orientation relationships between the catalyst particles and the graphite.

Iron-rich complexes in human spleen in hereditary spherocytosis

Tissue iron plays an important role in the development of certain diseases. Although it is one of biogenic elements, its excess induces the reactive oxygen species (ROS) formation. The aim of the present work is to examine the protection against free or loosely bound iron from the view of morphology and chemical composition of iron-rich complexes in human spleen tissues with hereditary spherocytosis (HS) by scanning and transmission electron microscope with energy-dispersive microanalysis (EDX). The examination of human spleen tissues by scanning and transmission electron microscope showed covering of iron-rich particles. EDX revealed many iron-rich complexes of multi-element composition in HS samples with sulphur and phosphorus as the major elements. Detection was negative in the reference samples. The covering of iron-rich particles can be explained by elimination and isolation of ferritin/iron complexes from surrounding environment to prevent the ROS formation. Sulphur, phosphorus and their compounds are probably the most significant elements that influence the ROS formation (Fig. 5, Ref. 16). Full Text in PDF www.elis.sk.

Study of the structural and magnetic properties of metallic iron-hematite particles for use in magnetorheological fluids

Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few μm to about 200 μm and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and Mossbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20 μm (sample A) and in the range of 20–38 μm (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3 h, using different values of rotational speed/time: 200 rpm for one hour, a pause of 10 s, 140 rpm for one hour, pause 10 s and then 175 rpm during the last hour. These powders were sieved to obtain particles smaller than 20 μm (sample C). According XRD results, in all samples, only α-Fe (lattice parameter a = 2,867(2) A) and Fe2O3 (lattice parameter a = 5,037(1) A and c = 13,755(8) A) were present. The Mossbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to α-Fe and the second one to Fe2O3 in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.

Pelagic boundary conditions affect the biological formation of iron‐rich particles (iron snow) and their microbial communities

We studied the formation of iron‐rich particles at steeply opposing gradients of oxygen and Fe(II) within the redoxcline of an acidic lignite mine lake (pH 2.9). Particles formed had a diameter of up to 380 μm, showed high sedimentation velocity (∼ 2 m h‐1), and were dominated by the iron mineral schwertmannite. Although the particles were highly colonized by microbial cells (∼ 1010 cells [g dry weight]‐1), the organic carbon content was below 11%. Bathymetry and the inflow of less acidic, Fe(II)‐rich groundwater into the northern basin of the lake results in two distinct mixing regimes in the same lake. The anoxic monimolimnion of the northern basin had higher pH, Fe(II), dissolved organic carbon, and CO2 values compared with the more central basin. Particles formed in the northern basin differed in color, were smaller, had higher organic carbon contents, but were still dominated by schwertmannite. Microcosm incubations revealed the dominance of microbial Fe(II) oxidation. Comparison of bacterial clone libraries suggested that pH was a major driving force, shaping the microbial communities responsible for the oxidation of Fe(II) in both basins. Acidophilic Ferrovum spp. and Chlorobia‐related bacteria were present in the central basin, whereas neutrophilic Sideroxydans spp. dominated the northern basin. Snow‐like particles had a high sinking velocity and acted as a carrier for organic carbon, microorganisms, trace metals, and Fe(III) to the sediment. Because these particles are fundamentally different from organic‐rich “snows” from lakes, rivers, and oceans, we propose a new term, “iron snow.”

Characterization of Irreversible Black Soiling Layer Formation on Historic Unglazed Terracotta Substrates Using Analytical Scanning Electron Microscopy (ASEM) with Energy Dispersive X-Ray (EDX) Analysis

The increased use of architectural terracotta in the smoke-ridden cities of Victorian Britain was largely attributed to its ‘self-cleaning’ nature. However, it quickly became apparent that use of the material in urban areas often resulted in its affliction with certain soiling characteristics. Previous research has largely overlooked thorough investigation of the very mechanisms by which the soiling becomes so tenaciously bonded to the facade of terracotta in the first place. The manufacturing process and the properties of architectural terracotta have been reviewed along with current theories surrounding soiling and adhesion mechanisms. Both soiled and unsoiled samples were characterized using reflected light optical microscopy and analytical scanning electron microscopy (ASEM) with energy dispersive x-ray (EDX) analysis. The soiling layer was a uniformly thin amorphous layer that appeared to be brittle in nature and formed in-situ by external influences. It contained crystalline gypsum inclusions and submicron iron-rich particles.

Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling

Iron-rich smectite is commonly described in the diagenetic fraction of deep-sea sediment, as millimeter to centimeter aggregates dispersed in the sediment, or as a coating on sedimentary particles or nodules. This study examines several factors to elucidate formation mechanisms of a particular iron-rich smectite and its potential transformation to glauconite. The study combines a detailed mineralogical investigation on natural samples and a chemical modeling approach to assess mineralogical reactions and pathways. Transmission electron microscopy (TEM) observations and analytical electron microscopy (TEM–AEM) analyses were conducted on microtomed samples of millimeter- to centimeter-long green grains. These grains are widespread in pelagic calcareous sediment from the Costa Rica margin. They are composed of pyrites that are partially dissolved and are surrounded by amorphous or very poorly crystallized iron-rich particles. Iron-rich montmorillonite grows from an amorphous precursor and its formation requires the input of Si, O, Mg, K, Na and Ca; our results suggest that these inputs are supported by the dissolution of sedimentary phases such as volcanic glasses, siliceous fossils and silicates. Thermodynamic modeling of fluid–sediment interactions was conducted with the geochemical computer code PhreeqC, using mineralogical and pore fluid compositions from sediment samples and calculated estimates for thermodynamic constants of smectites that are not maintained by the computer code. Simulations confirm the possibility that the green grains are the product of pyrite alteration by seawater under oxidizing conditions. The extent of smectite production is controlled by the kinetics of pyrite dissolution and fluid migration. The absence of aluminum in the Costa Rica margin system explains the formation of an iron-rich montmorillonite instead of glauconite, whereas the presence of calcite that buffers the system explains the formation of an iron-rich montmorillonite instead of iron oxides.

Assessment of heavy metals in the particulate matter of two Brazilian metropolitan areas by using Tillandsia usneoides as atmospheric biomonitor

The aims of this paper were to quantify the heavy metals (HM) in the air of different sites in Rio de Janeiro (RJ) and Salvador (SA) using Tillandsia usneoides (Bromeliaceae) as a biomonitor, and to study the morphology and elemental composition of the air particulate matter (PM) retained on the Tillandsia surface. Tillandsia samples were collected in a noncontaminated area and exposed to the air of five sites in RJ State and seven in SA for 45days, in two seasons. Samples were prepared to HM quantification by flame atomic absorption spectrophotometry, while morphological and elemental characterizations were studied by using scanning electron microscopy. HM concentrations were significantly higher when compared to control sites. We found an increasing metal concentration as follows: Cd < Cr < Pb < Cu < Zn. PM exhibited a morphology varying from amorphous- to polygonal-shaped particles. Size measurements indicated that more than 80% of particles were less than 10μm. PM contained aluminosilicates iron-rich particles, but Zn, Cu, Cr, and Ba were also detected. HM input in the atmosphere was mainly associated with anthropogenic sources such as vehicle exhaust. Elemental analysis detected HM in the inhalable particles, indicating that those HMs may intensify the toxic effects of PM on human health. Our results indicated T. usneoides as an adequate biomonitor of HM in the PM belonging to the inhalable fraction.

Intracellular and extracellular mineralization of a microbial community in the Edmond deep-sea vent field environment

Microbial biomineralization in submarine hydrothermal environments provides an insight into the formation of vent microfossils and the interactions between microbes, elements and minerals throughout the geological record. Here, we investigate microbial biomineralization of a deep-sea vent community in the Edmond vent field and provide ultrastructural evidence for the formation of microfossils and biogenic iron-rich minerals related to Archaea and Bacteria. Environmental scanning electron microscopy (ESEM) analysis shows that filamentous and spiral microbes are encrusted by a non-crystalline silica matrix and minor amounts of iron oxides. Examination by transmission electron microscopy (TEM) reveals acicular iron-rich particles and aggregates that occur either intracellularly or extracellularly. A culture-independent molecular phylogenetic analysis demonstrates a diverse range of Bacteria and Archaea, the majority of which are related to sulfur metabolism in the microbial mats. Both Archaea and Bacteria have undergone silicification, in a similar manner to microorganisms in some terrestrial hot springs and indicating that silicification may be driven by silica supersaturation and polymerization. Formation mechanisms of intracellular and extracellular iron oxides associated with microbes are discussed. These results enhance our understanding of microbial mineralization in extreme environments, which may be widespread in the Earth's modern and ancient hydrothermal vent fields.

Characterization of individual airborne particles in Taiyuan City, China

Taiyuan, the capital of Shanxi province, China, is one of the most polluted cities in the world. To characterize the ambient particulate pollution, samples of particulates with aerodynamic diameter less than 10 µm (PM10) were collected during a 6-day campaign. Individual particles were analyzed by Scanning Electron Microscope with Energy-Dispersive Spectrometer (SEM-EDS) to determine their chemical composition. Meanwhile, photomicrographs were obtained from SEM to aid in particles’ source identification. The lumped data from SEM-EDS were subjected to hierarchical cluster analysis (HCA) to sort out particle types chemically. HCA combined with SEM photomicrographs allowed us to identify 20 different particle types, namely (in order of particle frequency), soil/fly ash particles, coal-burning, sulfur-rich, and iron-rich particles, gypsum, syngenite, quartz, cement, silicon sulfide, siliconferro alloy, calcium-rich particles, ferrochromium alloy, ammonium sulfate and chloride, iron-zinc, ammonium chloride, molybdenum-rich, potassium sulfate, dolomite, lead sulfate, and copper-rich particles. Their possible origins and pathways are suggested. The majority of the particles seem to originate from coal combustion, which conforms to Taiyuan’s industrial structure.

Evaluation and application of biomagnetic monitoring of traffic-derived particulate pollution

Inhalation of particulate pollutants below 10 μm in size (PM 10) is associated with adverse health effects. Here we use magnetic remanence measurements of roadside tree leaves to examine levels of vehicle-derived PM around Lancaster, UK. Leaf saturation remanence (SIRM) values exhibit strong correlation with both the SIRM and particulate mass of co-located, pumped-air samples, indicating that these leaf magnetic values are an effective proxy for ambient PM 10 concentrations. Biomagnetic monitoring using tree leaves can thus provide high spatial resolution data sets for assessment of particulate pollution levels at pedestrian-relevant heights. Leaf SIRM values not only increase with proximity to roads with higher traffic volumes, but are also ∼100% higher at 0.3 m than at ∼1.5–2 m height. Magnetic and SEM data indicate that the particle populations are dominated by spherical, iron-rich particles ∼0.1–1 μm in diameter, with fewer larger, more angular, silica-rich particles. Comparison of the roadside leaf-calculated PM 10 concentrations with PM 10 concentrations predicted by a widely-used atmospheric dispersion model indicates some agreement between them. However, the model under-predicts PM 10 concentrations at ‘urban hotspots’ such as major–minor road junctions and traffic lights. Conversely, the model over-predicts PM 10 concentrations with distance from the road wherever one tree is screened by another, indicating the filtering/protective effect of roadside trees in leaf.

The chiton stylus canal: An element delivery pathway for tooth cusp biomineralization

A detailed investigation of the stylus canal situated within the iron mineralized major lateral teeth of the chiton Acanthopleura hirtosa was undertaken in conjunction with a row-by-row examination of cusp mineralization. The canal is shown to contain columnar epithelial tissue similar to that surrounding the mineralized cusps, including the presence of iron rich particles characteristic of the iron storage protein ferritin. Within the tooth core, a previously undescribed internal pathway or plume is evident above the stylus canal, between the junction zone and mineralizing posterior face of the cusp. Plume formation coincides with the appearance of iron in the superior epithelium and the onset of mineralization at tooth row 13. The plume persists during the delivery of phosphorous and calcium into the tooth core, and is the final region of the cusp to become mineralized. The presence of the stylus canal was confirmed in a further 18 chiton species, revealing that the canal is common to polyplacophoran molluscs. These new data strongly support the growing body of evidence highlighting the importance of the junction zone for tooth mineralization in chiton teeth, and indicate that the chemical and structural environment within the tooth cusp is under far greater biological control than previously considered.

In situ X-ray diffraction of pyrolite to 40 GPa using Kawai-type apparatus with sintered diamond anvils: possibility for the existence of iron-rich metallic particles in the lower mantle

We investigated phase relations in pyrolite at ∼33–40 GPa and ∼1800–2150 K by in situ X-ray diffraction using Kawai-type apparatus with sintered diamond anvils. The results demonstrated that MgSiO3-rich orthorhombic perovskite (mpv), CaSiO3-rich cubic perovskite (cpv) and (Mg,Fe)O ferropericlase (fp) are the stable phases in pyrolite bulk composition at the conditions corresponding to the lower mantle. However, chemical analyses of a run product recovered from ∼ 34 GPa by an analytical transmission electron microscope showed the coexistence of metallic iron particles with mpv, fp, and SiO2-rich amorphous phase. Also, Fe/Mg partitioning coefficient between mpv and fp was found to be 0.66(31), which is consistent with previous results for pyrolite bulk composition at 26–30 GPa and ∼1900 K. These results indicate that iron-rich metallic particles can exist in the lower mantle as a stable phase to the depth of at least ∼900 km.

Particulate matter analysis at elementary schools in Curitiba, Brazil

The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence (EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition associations. Five classes were identified based on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average 42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine fraction showed a deposition rate of approximately 18% for both deposition levels.

Magnetoreception in birds: two receptors for two different tasks

Birds can use the geomagnetic field as a source of navigational information in different ways: the magnetic vector provides a compass; magnetic intensity and/or inclination play a role as a component of the navigational 'map', and magnetic conditions of certain regions act as 'sign posts' or triggers, eliciting specific responses. Two hypotheses on magnetoreception are currently under dis- cussion. One proposes a chemical compass based on a radical pair mechanism involving direction-dependent reactions in specialized photopigments; the other postulates processes involving iron-rich particles, such as magnetite. Behavioral evidence suggests that birds use both mecha- nisms, with radical pair processes in the right eye providing directional information and an iron-based mechanism in the upper beak providing information on position as a component of the navigational 'map'. Electrophysiological data support this view. The interactions of the two mech- anisms, however, are still poorly understood.

Spatial variation in vehicle-derived metal pollution identified by magnetic and elemental analysis of roadside tree leaves

Exposure to metal-rich particulate pollution is associated with adverse health outcomes. In particular, lead has recently been shown to be toxic in young children even at low levels previously considered ‘safe’. Lead poisoning from vehicle pollution has been addressed internationally by removal of leaded petrol but toxic blood lead levels in children continue to be reported in urban areas, the source suggested to be resuspended roadside soil, enriched in lead due to previous leaded fuel usage. Here, we use paired geochemical and magnetic analyses of natural biomonitors—kerbside tree leaves—and of air sample filters to examine contemporary sources of particulate pollution, and show that co-associated, fine (<1 μm) lead- and iron-rich particles are emitted as vehicle-derived pollutants. Higher and strongly correlated lead, iron and magnetic remanence values were found closer to roads and on the road-proximal rather than road-distal sides of trees. Critically, highest pollutant values occurred on tree leaves next to uphill rather than downhill road lanes. The lead content of the leaf particulates was associated only with sub-micrometre, combustion-derived spherical particles. These results indicate that vehicle exhaust emissions, rather than resuspended soil dust, or tyre, brake or other vehicle wear are the major source of the lead, iron and magnetic loadings on roadside tree leaves. Analysis of leaves at different heights showed that leaf particulate lead and iron concentrations are highest at ∼0.3 m (i.e. small child height) and at 1.5–2 m (adult head height) above ground level; monitoring station collectors placed at 3 m above the surface thus significantly under-estimate kerbside, near-surface lead concentrations. These results indicate that vulnerable groups, especially young children, continue to be exposed to fine, lead- and iron-rich, vehicle-derived particulates.

Synthesis, Characterization, and Surface Properties of Iron-Doped Boehmite Nanofibers

Iron-doped boehmite nanofibers with varying iron contents have been prepared at low temperatures using hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resulting nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray analysis, and N2 adsorption. TEM images showed that the resulting nanostructures are predominantly nanofibers when the doped iron content is less than 5% (mol/mol); in contrast, nanosheets were formed when iron doping was above 4%. Nanotubes instead of nanofibers and iron-rich particles were observed in samples with 20% added iron. A detailed characterization and discussion on the iron-doped nanofibers is presented.