Maximum Hysteresis Research Articles

Molecular dynamics simulation study of a polymer droplet transport over an array of spherical nanoparticles

The dynamic behavior of a partially wetting polymer droplet driven over a nanostructured interface is studied using molecular dynamics simulations. We consider the bead-spring model to represent a polymeric liquid that partially wets a rough surface composed of a periodic array of spherical particles. It is shown that at sufficiently small values of the external force, the droplet remains pinned at the particles’ surface, while above the threshold, its motion consists of alternating periods of pinning and rapid displacements between neighboring particles. The latter process involves large periodic variation of the advancing and receding contact angles due to attachment and detachment of the contact line. Finally, upon increasing external force, the droplet center of mass is displaced steadily but the oscillation amplitude of the receding contact angle as well as the maximum contact angle hysteresis remain relatively unaffected.

Predicting hardness profile of steel specimens subjected to Jominy test using an artificial neural network and electromagnetic nondestructive techniques

ABSTRACT Based on relationships between electromagnetic properties and microstructural changes in steel, the current paper describes the development of an electromagnetic technique to determine steel hardenability, non-destructively. Performing Jominy end-quench test, magnetic hysteresis loop and eddy current methods have been applied to SAE 4140 standard steel samples to explore applicability of the non-destructive techniques for determining hardenability. Different hysteresis loop parameters (maximum magnetic flux density, coercivity, hysteresis loss and maximum differential permeability) as well as eddy current outputs (induced voltage, normalised impedance and phase angle) as a function of distance from the end-quenched surface were investigated and the results show a clear agreement with data obtained by traditional hardness testing. In addition, taking advantage of a generalised regression neural network, magnetic data obtained from hysteresis loop and eddy current methods could be used to accurately estimate results in the hardness profile of a given sample, using a few training data points. This paper shows that coupling the proposed non-destructive methods to Jominy end-quench test facilitates accurate non-destructive hardenability determination of steel samples while reducing time and cost of the test process.

Magnetic Modification and the Mechanism of Tb‐Phthalocyanine Single Molecule Magnets Prepared by a High Yield Method

Lanthanide single‐molecule magnets are the most promising materials to be applied in the future spintronics applications. In this report, we firstly synthesize double‐decker Phthalocyanines (Pc), TbPc2 single‐molecule magnets and paramagnetic YPc2 by a straightforward solvothermal route with a yield up to 16 %, which is three times larger than that of conventional method. Their crystal structures and properties are systematically characterized by the matrix‐assisted laser desorption ionization–time‐off light mass spectrometry, X‐ray diffractometer, Ultraviolet–visible spectra, Fourier transform infrared spectra, X‐ray photoemission spectroscopy, near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy, Inductive Coupled Plasma Emission Spectrometer and magnetic measurements. The NEXAFS spectroscopy confirms that a strong peak at 401 eV emerges not YPc2 but TbPc2, clearly indicating the different electronic structures of YPc2 and TbPc2. A typical hysteresis loop of single molecule magnet is observed for TbPc2. While, YPc2 shows a paramagnetic character. The SMM property of TbPc2 modified by introducing YPc2 was studied in detail. The maximum hysteresis area appears for the sample with Tb/Y = 7:3, which obviously demonstrates the concentration of YPc2 affects magnetic relaxation process by varying the intermolecular interactions of TbPc2. The barrier energy fitted from the results of alternating‐current magnetic susceptibility is 740 K for TbPc2 and 781 K for the sample with Tb/Y = 7:3, further indicating that the isolation of neighbor Tb ions by Y ions could slow down the flip of magnetic dipole.

Symmetrical threshold model with independence on random graphs.

We study the homogeneous symmetrical threshold model with independence (noise) by pair approximation and Monte Carlo simulations on Erdős-Rényi and Watts-Strogatz graphs. The model is a modified version of the famous Granovetter's threshold model: with probability p a voter acts independently, i.e., takes randomly one of two states ±1; with complementary probability 1-p, a voter takes a given state, if a sufficiently large fraction (above a given threshold r) of individuals in its neighborhood is in this state. We show that the character of the phase transition, induced by the noise parameter p, depends on the threshold r, as well as graph's parameters. For r=0.5 only continuous phase transitions are observed, whereas for r>0.5 discontinuous phase transitions also are possible. The hysteresis increases with the average degree 〈k〉 and the rewriting parameter β. On the other hand, the dependence between the width of the hysteresis and the threshold r is nonmonotonic. The value of r, for which the maximum hysteresis is observed, overlaps pretty well with the size of the majority used for the descriptive norms in order to manipulate people within social experiments. We put the results obtained within this paper into a broader picture and discuss them in the context of two other models of binary opinions: the majority-vote and the q-voter model. Finally, we discuss why the appearance of social hysteresis in models of opinion dynamics is desirable.

Internal Bracing Augmentation for Scapholunate Interosseous Ligament Repair: A Cadaveric Biomechanical Study

Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. This study compared scapholunate interosseous ligament (SLIL) repair alone, SLIL repair with IB augmentation (RIBA), and native intact SLIL (NIS) in a biomechanical cadaveric model. We used 21 specimens of fresh-frozen wrists in this study (7 matched pairs, SLIL repair-only and SLIL RIBA groups; and 7 independent fresh-frozen wrists, NIS group). In the SLIL RIBA group, augmentation using IB was performed after the repair. The specimens were preloaded and cyclically loaded in tension. Maximum extension and hysteresis were measured in all specimens. The specimens were subsequently tested for load to failure. Failure load (yield point load, mean ultimate load, and load at clinical failure) and linear stiffness were calculated. In cyclic tensile testing, RIBA showed lower maximum extension and lower hysteresis than repair alone. In load to failure testing, the yield point load was statistically higher in the RIBA (59.3 N) group than in the repair-only (30.4 N) group but showed no significant difference compared with the NIS (90.7 N) groups. Moreover, the RIBA (98.5 N) group showed higher and lower mean ultimate loads than the repair-only (37.7 N) and NIS (211.8 N) groups, respectively. Load at clinical failure was higher with RIBA than with repair alone (3-mm extension: 70.0 vs 26.4 N; 4-mm extension: 84.1 vs 33.4 N). Repair alone and RIBA had comparable linear stiffness (38.2 vs 44.1 N/mm). Although SLIL RIBA did not recreate biomechanical properties equivalent to those of NIS, it demonstrated a significantly higher strength than repair alone. Repair with IB augmentation could serve as a novel surgical technique that enhances SLIL direct repair through biomechanical support.

A combined experimental and theoretical study of the magnetic properties of bulk CoFe2O4

This work is devoted to studying experimentally and theoretically the structural and magnetic properties of bulk cobalt spinel ferrite. Solid-state reaction with optimized synthesis conditions is used to prepare CoFe2O4. The crystallization of CoFe2O4 in the FCC structure was confirmed with the X-ray diffraction. The microstructural properties are performed using the scanning electron microscopy. The magnetic properties of the bulk cobalt ferrite were performed experimentally using the superconducting quantum interference device magnetometer (SQUID). Monte Carlo simulation with periodic boundary conditions was used to simulate bulk CoFe2O4 with a large enough size of the system. The obtained magnetization and susceptibility as a function of temperature show that CoFe2O4 exhibits a second-order transition to paramagnetic phase around 725 K. To carry out the maximum energy product, experimental and theoretical magnetic hysteresis loops at room temperature were performed. It is found that the synthesized CoFe2O4 has a high saturation magnetization of about 87.89 emu/g, which is close to the theoretical value of 97.13 emu/g. Lower coercivity–sugariness ratio was found which indicates that bulk cobalt spinel ferrite is a magnetic multi-domain in nature. To evaluate the efficiency of bulk CoFe2O4, the maximum energy product was calculated at room temperature. Our results demonstrate from a microscopic to the macroscopic scale the performance of CoFe2O4 as a promising magnetic material in the new energy technology generation.

Humidity dependent impedance characteristics of SbSeI nanowires

A humidity sensor has been successfully fabricated through a sonochemical synthesis of antimony selenoiodide (SbSeI) nanowires and their high pressure (100 MPa) compression at room temperature. For the first time, this nanomaterial has been investigated using impedance spectroscopy. The effect of water vapor on the impedance characteristics of the SbSeI sensor has been studied for different temperatures (293 K ÷ 343 K) in the range of relative humidity (RH) from 30% to 80%. Fabricated device has been also subjected to periodic humidity fluctuations. The transient characteristics of an impedance of the SbSeI sensor have been highly correlated to humidity input cycles. The response has exhibited an excellent repeatability, long-term stability, and a maximum hysteresis of 3.7% RH for humidity changing rate of 0.083%∙min−1. The least-square fitting of Nyquist characteristics of the sensor has allowed determining an equivalent electric model of SbSeI xerogel. The humidity sensing mechanism has been explained with reference to a proton hopping. Presented results demonstrate a great potential of SbSeI nanowires for humidity sensing applications.

Resistive- and capacitive-type humidity and temperature sensors based on a novel caged nickel sulfide for environmental monitoring

In this work for the first time, a new bis(4-benzylpiperazine-1-carbodithioato-k2S,Sʹ)nickel(II) complex (hereafter caged nickel sulfide) has been used to fabricate the capacitive-type and resistive-type sensor. The surface consisted of 2D plates, pores and pore-channels of various shapes and size. These 2D plates and pores played a pivotal role in the sensing mechanism of the sensor. The conduction mechanism is based on Von Grotthuss mechanism. In the relative humidity (RH) range 30–90%, the resistance of the sensor was decreased by two orders of magnitude (from 2.94 × 108 Ω at 30%RH to 2.34 × 106 Ω at 90%RH at operational frequency of 120 Hz). While at applied frequency of 120 Hz, capacitance of the sensor was increased from 15.95 pF to 38.1 pF in the range of 30–90%RH. At higher frequency (10 kHz) the capacitance of the sensor is reduced to 6.285 pF. The maximum hysteresis of 1.54% is noted which is less than the reported in the literature. The response and recovery time of the sensor were 25 and 30 s, respectively, which are either far smaller or greater than the response and recovery time of the various sensors reported in the literature.

Spatiotemporal characteristics of hydrothermal processes of the active layer on the central and northern Qinghai–Tibet plateau

The spatial and temporal variations of the seasonal freeze–thaw cycles are important in understanding the ecological and hydrological processes and biogeochemical cycle associated with permafrost degradation caused by climate change, although observational data on the soil hydrothermal dynamics within the active layer of the permafrost region at the central and northern Qinghai–Tibet Plateau (QTP) are extremely scarce. In this study, soil temperature and moisture date from 11 observational sites along the Qinghai–Tibet Highway from 2010 to 2014 were used to analyze the freeze-thaw cycles of the active layer. The results revealed that mean annual ground surface temperature (MAGST) and mean annual temperature at the top of permafrost (TTOP) were the most closely related to the onset dates of soil freezing and thawing. The onset dates of soil freezing from bottom to top did not occur earlier than those from top to bottom. The differences between the onset dates of the two freezing directions and the proportion of bottom-up freezing depth increased with decreasing TTOP. The unfrozen water content of the cooling process was always higher than that of the warming process during the freezing stage. The hysteresis effect of the unfrozen water content could also be observed in the field experiment, and the maximum hysteresis levels occurred at their corresponding soil freezing points. Soil organic matter and soil moisture associated with vegetation cover are essential for water-heat exchanges between atmosphere and permafrost beneath active layer. We suggest that a better protected plant ecosystem, helps preserving the underlying permafrost on the Qinghai–Tibet Plateau.

Scalable Fabrication of Highly Flexible Porous Polymer-Based Capacitive Humidity Sensor Using Convergence Fiber Drawing.

In this study, we fabricated a highly flexible fiber-based capacitive humidity sensor using a scalable convergence fiber drawing approach. The sensor’s sensing layer is made of porous polyetherimide (PEI) with its porosity produced in situ during fiber drawing, whereas its electrodes are made of copper wires. The porosity induces capillary condensation starting at a low relative humidity (RH) level (here, 70%), resulting in a significant increase in the response of the sensor at RH levels ranging from 70% to 80%. The proposed humidity sensor shows a good sensitivity of 0.39 pF/% RH in the range of 70%–80% RH, a maximum hysteresis of 9.08% RH at 70% RH, a small temperature dependence, and a good stability over a 48 h period. This work demonstrates the first fiber-based humidity sensor fabricated using convergence fiber drawing.

An Interdigital Capacitive Humidity Sensor With Layered Black Phosphorus Flakes as a Sensing Material

Black phosphorus (BP) atomic layers have received significant attention for chemical sensing applications due to its exceptional electrical, mechanical, and surface properties. However, they are known to undergo chemical degradation in ambient conditions. In this paper, an interdigital capacitive humidity sensor with layered BP flakes as a sensing material is reported. The BP flakes were prepared from crystal powders by the mechanical exfoliation and then deposited on the interdigital electrode (IDE) structures by a spin-coating method. The deposited BP flakes were characterized by the atomic force microscope (AFM) and Raman spectroscopy, which demonstrated the uniformity of highly crystalline BP flakes. The interdigital capacitive humidity sensors were measured under different relative humidity (RH) levels. The results obtained show that the capacitance increases gradually as the RH levels with the sensitivity of about 0.2pF/%RH at the low RH levels (<45%RH) while the capacitance increases rapidly as the RH levels with the high sensitivity of about 10pF%RH. The maximum hysteresis was measured to be about 3%RH. Stability measurement showed that the capacitance of the sensors increased in the first 15 hours and then tended to be stable. Good repeatability was observed in the measurement, suggesting that degradation was prevented. Oxide layers were formed on the surface instead and the inside layers of BP kept intact. The estimated response and recovery time of the capacitive sensors was about 17s and 4.7s, respectively. The equivalent RC networks model for the capacitive sensors is proposed to explain the mechanisms. The fast response and excellent sensitivity of the capacitive sensors at the high RH levels showed potential applications in high RH monitoring areas.

Realization of a micro composite based pressure sensor: Its performance study for linearity, hysteresis and sensitivity

The relevance of pressure sensors in daily life applications has been phenomenal in diversified disciplines such as engineering, bio-medical, automobile, aerospace etc. Making right choice of pressure sensors is crucial in any of these disciplines. Of late, the pursuit of making the pressure sensors applicable to various domains has spurred a variety of innovative activities. They are being fabricated using novel materials and unconventional fabrication methodology. Also, the advent of microelectromechanical systems has provided new horizons for a variety of realizations that led to the development of efficient and robust pressure sensors. The electromechanical characteristics of the sensing materials and the fabrication methodologies employed to realize the sensor have significant influence on performance of the sensor. This paper reports the micro composite based piezoresistive gauge pressure sensor performance study which was realized by screen printing technique. Graphite-PVC resin based dispersions are screen printed on flat, circular shaped, 1.98 mm thick stainless-steel diaphragm. The transducing layers are directly printed on the deforming polymer coated diaphragm so that the coupling factor is high, resulting in an efficient transfer of strain. Pressure cyclic study and its effect on linearity, hysteresis, sensitivity, stability etc. are investigated. The sensitivity is found to be 0.357 mV/bar. The maximum hysteresis and non-linearity are found to be less than 0.8% FSO. A fairly satisfactory sensitivity, linearity, hysteresis and stability are accomplished at a low cost. By observing the performance characteristics of the realized pressure sensor it can be used in commercial, industrial, automotive, aerospace and strategic fields. Some of the applications could be in tire pressure sensing, air filling in petrol bunks, petrol/diesel/oil/water tankers, water supply pipelines, oil/gas explorations, hydraulic jacks and mines etc.

Research on key technologies of bearing preload of spindle based on piezoelectric actuators

This study analysed the influence of bearing preload on the stiffness of spindle bearings. MATLAB/Simulink is used to calculate the vibration of simplified spindle system. The vibration of the simplified spindle system decreases with the increase of bearing preload. A kind of force output characteristics of piezoelectric actuators test device was designed. Experimental analysis of the maximum force output characteristic, hysteresis characteristic, creep characteristic and stability characteristic of PSt 150/4/7 VS9-type piezoelectric actuators under different initial loads, voltage frequencies, cycles working and voltage travel. The evaluating indexes are the maximum output force, average hysteresis, maximum deviation, drift amount and cycle delay. In conclusion that the piezoelectric actuator has better repeatability and stability under the initial load is around 150 N and low-voltage frequency. It is not suitable for multiple cycles working. The increment of output force is proportional to starting voltage at same voltage travel. MATLAB/Simulink is used to calculate the feasibility of variable bearing preload strategy based on a piezoelectric actuator. It provided scientific references for the research of high performance and intelligent spindle.

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO3) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO3 composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO3 composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO3 nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO3 composite film shows that as the concentration of BaTiO3 particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO3 composites. The maximum hysteresis of the capacitive PVDF-BaTiO3 (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.

Droplet Dynamics and Removal from Polymer Electrolyte Fuel Cell Channels Using Acoustic Pressure Waves

Liquid water management in polymer-electrolyte-membrane (PEM) fuel cell reactant channels is critical to system performance, stability, and lifespan. A balance between cathode catalyst layer water generation and removal must be maintained to ensure proper membrane hydration while preventing flooding. Liquid water transport through the gas-diffusion-layer (GDL) results in droplet formation in reactant channels that may be removed via flow gas drag forces. This work investigates the effect that acoustic wave transmission in reactant flow gases has on liquid water droplets growing on the GDL surface. While recent and past work has shown this method may be useful toward preventing liquid buildup in reactant channels, fundamental analysis of the droplet behavior is lacking [1-3]. In this study experiments were performed using a transparent ex-situ flow channel of 3.5 (h) x 3.7 (w) mm cross section as shown in Figure 1a. Water droplet formation was controlled using a digital syringe pump injected through a port on the backside of the GDL. Air and Hydrogen were used to simulate both cathode and anode flow conditions. A speaker was connected in series with the feed gas and flow channel whereby acoustic signals were generated and passed through the reactant channel. Transducers measured pressure upstream and downstream of the droplet while a high speed camera captured images of the droplets motion from the side (Figure 1b). Early results show that pressure waves effect droplets pinning behavior on the GDL surface. Previous work has shown that a maximum contact angle hysteresis exists for droplet removal from GDLs. While gas flow causes droplet contact angle hysteresis, this work shows that oscillations caused by the acoustic waves may shift the droplet over the max hysteresis tipping point enabling removal.

Carbon nanotubes immobilized on gold electrode as an electrochemical humidity sensor

Multi-walled carbon nanotubes (MWCNTs) were fabricated on a gold electrode to develop a resistance-sensing humidity sensor with low resistance. Core-shell-structured nanohybrids were prepared using Chitosan-MWCNT to obtain good hydrophilicity, resulting in a highly responsive humidity sensor. We also measured resistance, which changes due to hydrogen bonding between the amine group of chitosan and H2O. The structure of the fabricated chitosan-MWCNT core–shell-structured nanohybrid was measured. Furthermore, we determined the highest response and linearity of the CS-MWCNT25 nanohybrids based on the number of coats on the electrode and the composition ratio of chitosan and MWCNTs. The fabricated CS-MWCNT25 nanohybrid humidity sensor exhibited good electrical efficiency without voltage or frequency dependence and a low-temperature dependency with a temperature coefficient (RH/°C) of 0.187%. Finally, a fast recovery time of 40 s between 30% and 100% RH, a maximum humidity hysteresis of less than 0.300 ± 0.001%, and long-term stability for 2 months indicated that this is an excellent humidity sensor.

Numerical investigation of the deformation properties of rock materials subjected to cyclic compression by the finite element method

Rock materials, which are involved in a myriad of engineering projects, are often subjected to cyclic loading, such as earthquakes. Understanding the dynamic deformation properties of rock materials under cyclic loading is necessary for evaluating the stability of rock engineering structures. This study numerically investigated the influence of cyclic loading conditions (e.g., waveform, frequency, maximum loading stress and amplitude) on the deformation properties of rock samples using the finite element method (FEM). On the basis of the Drucker–Prager (D-P) yield criterion and sub-loading surface theory, a dynamic constitutive model for reproducing the hysteresis loops and the accumulative plastic deformation of rock materials subjected to cyclic loading was established, numerically implemented using FEM, and validated through comparison with experimental results on basalt and granite model materials. Then, cyclic uniaxial loading tests were simulated with a range of loading parameters, and the deformation properties of rock samples were analyzed. The results indicated that the hysteresis loops and accumulated plastic deformation of rock materials during the cyclic process can be numerically reproduced in an effective manner. The loading parameters significantly affected dynamic deformation properties such as the maximum strain, irreversible strain and hysteresis loop. The simulation results were almost consistent with the experimental results in the published literature. Therefore, through the proposed dynamic constitutive model, FEM can be used to numerically simulate the influence of cyclic loading conditions on the deformation properties of rock materials.

Effects of network robustness on explosive synchronization

Current studies have shown that there is a positive correlation between the network assortativity and robustness and that the assortativity also plays an important role in explosive synchronization. In this paper, taking the network robustness as a global property, we investigate its significance as well as the influence of its interaction with the assortativity on explosive synchronization. Our numerical results demonstrate that explosive synchronization is suppressed in extreme situations of both the robustness and assortativity. In addition, through appropriate adjustments of them, a maximum hysteresis area between the forward and backward transitions can be reached. Furthermore, our results might also provide reference for those who are interested in effects of network structure on synchronization, though this problem is still challenging as we show in the discussion.

Droplet Dynamics and Removal from Polymer Electrolyte Fuel Cell Channels Using Acoustic Pressure Waves

Liquid water management in polymer-electrolyte fuel cell (PEFC) reactant channels is critical to system performance, stability, and lifespan. This work investigates the effect that acoustic wave transmission in reactant flow gases has on liquid water droplets growing on the GDL surface. A speaker was connected in series with the feed gas and flow channel whereby acoustic signals were generated and passed through the reactant channel. Transducers measured pressure upstream and downstream of the droplet while a high speed camera captured images of the droplets motion from the side. Early results show that pressure waves effect droplets pinning behavior on the GDL surface. Previous work has shown that a maximum contact angle hysteresis exists for droplet removal from GDLs. While gas flow causes droplet contact angle hysteresis, this work shows that oscillations caused by the acoustic waves may shift the droplet over the max hysteresis tipping point enabling removal.

Morphology controllable Fe2O3 nanostructures derived from Fe-based metal-organic frameworks for enhanced humidity sensing performances

Porous metal oxides nanostructures with controlled shape have received great attention due to their promising applications in many fields. In the present investigation, three nano-sized (100～200 nm) Fe-based metal-organic frameworks (Prussian Blue) with different morphologies were synthesized. The morphologies of the Prussian Blue (PB) can evolve from cube, quasi-cube to sphere only by tuning the amount of PVP and the reaction temperature. And then, porous Fe2O3 nanostructures with the same shapes were obtained by calcining the PB templates at the optimal temperature 350 °C in air. The humidity sensing devices were fabricated by the three nanostructures. Humidity sensing tests reveal that the three sensors all displayed excellent humidity sensing performances, such as ultra-fast response, high response, good linear relationship, small humidity hysteresis. Among them, the quasi-cubic Fe2O3 nanostructures exhibited the best performance: the response time was less than 2 s, the response was 1568 in the humidity range of 11% ˜ 95%RH, the maximum humidity hysteresis was 0.59% and the value of the linearity fit correlation (R2) was 0.9922. Meanwhile, the sensor fabricated by the quasi-cubic nanostructures reveals that the capacitance change can reach 120% from 0% RH to 8%RH, demonstrating good potential to detect low humidity. Such outstanding humidity sensing performance of the sensor should be attributed to the synergic effect of the large specific surface area (169.7 m2/g) and highly porous structure of the quasi-cubic Fe2O3 nanostructures.