Physical Mixing Method Research Articles

Thermal properties and thermal conductivity enhancement of composite phase change material using sodium acetate trihydrate–urea/expanded graphite for radiant floor heating system

For heat exchanger used as latent heat storage system, heat storage capacity and thermal conductivity of phase change material are key indicators to determine its performance. In this paper, sodium acetate trihydrate-urea non-eutectic mixture as phase change material and expanded graphite as thermal conductivity enhancer, a sodium acetate trihydrate-urea/expanded graphite composite phase change material (CPCM) with both high latent heat and thermal conductivity for heat exchanger was developed by physical mixing method. The mass fractions of urea in the mixture and expanded graphite in CPCM were optimized. The crystalline phase and morphology of the obtained CPCM were characterized by X-ray diffraction and scanning electron microscope, and its thermal properties were investigated systematically. The results showed that the prepared CPCM containing 8% urea and 8% expanded graphite had a suitable phase change temperature (47.84 °C), high latent heat (223.1 kJ·kg−1), low supercooling degree (1.54 °C) as well as a satisfactory thermal conductivity (2.076 W·m−1·K−1). Moreover, the CPCM possessed a good shape stability and comparable thermal reliability. The results indicate that the obtained CPCM is an up-and-coming candidate for heat exchanger.

The effect of mesoporous silica impregnation on tribo-electrification characteristics of flurbiprofen

Tribo-electrification is a common occurrence within the pharmaceutical industry where solid dosage forms constitute majority of pharmaceutical formulations. Tribo-electrification of powders leads to a range of complications such as adhesion of particulate material to the processing equipment resulting in segregation, affecting the content uniformity. Flurbiprofen, a highly charging material, was used as a model drug to investigate the tribo-electrification and adhesion characteristics by impregnating the model drug inside a mesoporous silica matrix. The model drug was impregnated using i) solvent loading, and ii) physical mixing methods, at varying degree of silica to drug ratio (5–20% w/w). The resulting mixtures were tribo-charged using a custom built device based on a shaking concept inside a stainless steel capsule, consisting of a Faraday cup and connected to electrometer. The electrostatic charge and the percentage adhesion of Flurbiprofen were reduced in both drug loading methods. The solvent impregnation method using acetone was more successful at reducing the electrostatic charge build up on flurbiprofen than physical powder mixing. The percentage adhesion to the shaking capsule was reduced notably as a result of loading the drug in the SBA-15 porous network. The results illustrate that the incorporation of highly charged model drug inside a low-charging pharmaceutical carrier system to be an effective approach in control the induction of tribo-electrification phenomena during powder processing.

FORMULATION AND EVALUATION OF SOLID DISPERSION OF TADALAFIL

Tadalafil is used for the treatment of the erectile dysfunction (ED) and pulmonary arterial hypertension. It is having low aqueous solubility thus it shows poor bioavailability of about 28% by after oral administration. To improve its solubility and dissolution profile solid dispersions (SDPs) of Tadalafil was prepared by physical mixing and solvent evaporation method using polyvinyl pyrollidone-K30 (PVP-30) as a hydrophilic polymeric carrier in different proportions with respect to drug (drug to polymer ratio 1:1 to 1:5). Drug and polymer compatibility studies were performed using FTIR study. The best suitable ratio and method was selected on the basis of enhanced aqueous solubility of drugs. Further selected SDPs were evaluated for various parameters like DSC analysis, percentage yield, percent drug content, saturation solubility, percent drug dissolution and stability studies. FTIR study indicated no incompatibility between Tadalafil and PVP-K30. SDPs prepared with drug to polymer ratio 1:3 and solvent evaporation method was found to be best as they shown significant increased (up to 10 fold) in aqueous solubility in comparison with that of others. DSC study also suggested the depression in the crystalline nature of Tadalafil. Selected SDPs exhibited good stability up to 3 months at 25 ± 2°C /60 ± 5% RH. Based on the results it can be concluded that, SDPs shown remarkable increase in the aqueous solubility and dissolution of Tadalafil and it may improve oral bioavailability of drug as compared with plain drug.

FORMULATION AND EVALUATION OF SOLID DISPERSION OF TADALAFIL

Tadalafil is used for the treatment of the erectile dysfunction (ED) and pulmonary arterial hypertension. It is having low aqueous solubility thus it shows poor bioavailability of about 28% by after oral administration. To improve its solubility and dissolution profile solid dispersions (SDPs) of Tadalafil was prepared by physical mixing and solvent evaporation method using polyvinyl pyrollidone-K30 (PVP-30) as a hydrophilic polymeric carrier in different proportions with respect to drug (drug to polymer ratio 1:1 to 1:5). Drug and polymer compatibility studies were performed using FTIR study. The best suitable ratio and method was selected on the basis of enhanced aqueous solubility of drugs. Further selected SDPs were evaluated for various parameters like DSC analysis, percentage yield, percent drug content, saturation solubility, percent drug dissolution and stability studies. FTIR study indicated no incompatibility between Tadalafil and PVP-K30. SDPs prepared with drug to polymer ratio 1:3 and solvent evaporation method was found to be best as they shown significant increased (up to 10 fold) in aqueous solubility in comparison with that of others. DSC study also suggested the depression in the crystalline nature of Tadalafil. Selected SDPs exhibited good stability up to 3 months at 25 ± 2°C /60 ± 5% RH. Based on the results it can be concluded that, SDPs shown remarkable increase in the aqueous solubility and dissolution of Tadalafil and it may improve oral bioavailability of drug as compared with plain drug.

Synthesis of novel hard/soft ferrite composites particles with improved magnetic properties and exchange coupling

SrFe12O19/Zn0.4Co0.2Ni0.4Fe2O4 hard/soft ferrite composite particles with 20, 40, 60 and 80 wt.% of soft phase were prepared by one-pot sol-gel auto-combustion and physical mixing methods. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to characterize the structural and magnetic properties of the samples. XRD spectrum revealed the formation of mixed ferrite phases in the composite particles. The hysteresis loops of the samples showed the presence of exchange coupling between the hard and soft ferrites. The composite particles with 20 and 60 wt.% of the soft phase demonstrated the highest Mr/Ms ratio, i.e. 0.29 and 0.28, respectively. In addition, the highest Ms, Mr and Hc were achieved in the composite particles with 40, 60 and 20 wt.% of the soft phase, respectively. Compared to the physical mixing method (PM), the composite particles prepared by the sol-gel auto-combustion method (OP) demonstrated better magnetic properties. The exchange coupling interaction between the hard and soft ferrite phases was similar in both methods. These composite particles exhibited magnetically single phase behaviour, however, the saturation magnetization was lower in the physical mixing pared to that of the one-pot method.

Removal of volatile odorous organic compounds over NiAl mixed oxides at low temperature

In this paper, a series of NiAl hydrotalcite–like compounds (HTLCs) were prepared by the urea–decomposition method. Removal of carbonyl sulfide (COS) and methyl mercaptan (CH4S) over the hydrotalcite–derived oxides (HTO) at low temperature was studied. The Ni3Al-HTO exhibited higher catalytic activities than Ni3Al mixed oxides prepared by physical mixing method (Ni3Al-PM) or impregnation/calcination method (Ni3Al-IC). Based on the characterization, it was found that desulfurization activities are closely tied to the surface acid-base properties of catalysts. CO2-TPD indicates that the basic characteristic of the Ni3Al-HTO is prominent. XPS results showed that there was a strong interaction between Ni and Al element on Ni3Al-HTO. The first principle calculation based on density function theory was applied with the aim to study the change of basic sites. The results showed that Ni3Al-HTO presents a half-metallic characteristic. Electron transfer from the Al and O atom to the Ni atom was observed, which is helpful for the transfer of electrons from the surface and improves the catalytic activity. Analysis of the DRIFT spectra suggests that sulfate species was formed by the action of surface basic sites, resulting in the formation of H2O on the surface.

In-situ hydrothermal synthesis of CeO2/SnS2 heterojunction for use as a new efficient visible-light-driven photocatalyst

This communication reports a pioneering study on the synthesis and properties of CeO2/SnS2 composite. CeO2/SnS2 heterojunction was synthesized via the hydrothermal reactions of SnCl4·5H2O and thioacetamide in the presence of CeO2 nanoparticles at 170 °C for 12 h. The composition, structure, and optical properties of the as-synthesized CeO2/SnS2 heterojunction were characterized by X-ray diffraction, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra and photoluminescence spectra. The photocatalytic properties of the as-synthesized CeO2/SnS2 heterojunction were evaluated in the reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation, and compared with those of SnS2, CeO2, and CeO2/SnS2 nanocomposite prepared by physical mixing method (CeO2/SnS2-PM). The results demonstrated that the as-synthesized CeO2/SnS2 heterojunction had exceptionally higher visible-light-driven photocatalytic activity than SnS2, CeO2, and CeO2/SnS2-PM. The possible reasons underlying the photocatalytic results were proposed.

APPLICATION OF SOLID DISPERSION TECHNIQUE IN SOLUBILITY AND DISSOLUTION RATE ENHANCEMENT OF NATEGLINIDE

Objective: Nateglinide (NTG) is a potent short-acting biopharmaceutical classification system class II antidiabetic medication. The primary objective of the present investigation was to prepare and evaluate solid dispersions of NTG to enhance the component solubility and immediate release (IR) profile. The secondary objective was to formulate sustained release (SR) matrix layer of NTG for prolonging its effect in the body and to decrease oscillations in plasma concentration level.Methods: NTG (270 mg) SR layer was formulated using release retardant polymers such as Carbopol, ethyl cellulose (EC), hydroxy EC, hydroxypropyl methylcellulose (HPMC), Kollidon, and locust bean gum at concentrations of 15% and 30%. IR layer of NTG (60 mg) was formulated using drug: Polymer inclusion complexes (1:1 and 1:2) of β-cyclodextrin (CD), HP β-CD, polyvinylpyrrolidone (PVP) K-15, and PVP K-30 by physical mixing and kneading methods (KMs).Results: Among the all the carriers tested HP β-CD at 1:2 ratio prepared by KM (I3) gave highest enhancement of dissolution rate and dissolution efficiency with acceptable f1 (10.5) and f2 (51.0) values in comparison to marketed IR tablets (Starlix-60®). The SR formulation S12 was able to show a minimum amount of drug release (15%) within 1 hr comparatively, with a complete and sustained effect on drug release.Conclusion: Thus, HPMC K-100M at a concentration of 30% in the SR layer in combination with HP β-CD (1:2) solid dispersions in the IR layer may be used in the design of oral controlled drug delivery system for NTG.

Izod impact performance of hybrid carbon nanotube-alumina filled epoxy nanocomposites

In this paper, multi-walled carbon nanotube (CNT) was hybridized with alumina (Al2O3) particles via chemical vapour deposition using nickel as a metal catalyst. The purpose of hybridization between CNT and Al2O3 particles is to prevent the agglomeration of the CNT due to van der Walls forces as well as to improve the impact performance of the epoxy nanocomposites. The Al2O3 particles work as “transport” for the CNT to homogenously disperse within the epoxy matrix. As a comparative study, the CNT-Al2O3 was also prepared through a physical mixing method. The assessment showed that the CNT–Al2O3 hybrid filler produced more homogeneous dispersion in the epoxy matrix with a higher Izod impact strength than the physically mixed CNT–Al2O3 filler. The izod impact strength of epoxy nanocomposites at 5 % wt of CNT–Al2O3 hybrid has increased up to 32 % compared to the neat epoxy.

A novel La2NiO4+δ-La3Ni2O7-δ-Ce0.55La0.45O2-δ ternary composite cathode prepared by the co-synthesis method for IT-SOFCs

A novel La2NiO4+δ-La3Ni2O7−δ-Ce0.55La0.45O2−δ (L2N1-L3N2-LDC) ternary composite with a weight ratio of 0.3:2.5:2.2 was prepared by a one-step co-synthesis method and employed as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). X-ray diffraction (XRD) profiles confirmed the successful synthesis of the composite consisted of L2N1, L3N2 and LDC phases, without any other impurity. Compared with the cathode prepared by the physical mixing method, the co-synthesized composite cathode possessed a porous microstructure with the smaller particle size and more uniform distribution of various elements. The ternary composite cathode on Sm0.2Ce0.8O1.9 (SDC) electrolyte revealed improved electrochemical performance, achieving the polarization resistance value of 0.06 Ω cm2 at 800° C in stationary air. Electrochemical impedance spectra under various oxygen partial pressures indicated the charge transfer process was the rate limiting step for oxygen reduction reaction. Furthermore, a SDC electrolyte (about 350 μm) supported single cell with L2N1-L3N2-LDC as cathode and Ni-SDC as anode demonstrated a maximum power density of 253 mW cm−2 at 800° C. These results confirmed that L2N1-L3N2-LDC ternary composite prepared by co-synthesized method is a very promising cathode material for IT-SOFCs.

Effects of Annealing Temperature on Exchange Spring Behavior of Barium Hexaferrite/Nickel Zinc Ferrite Nanocomposites

(BaFe12O19)1−x/(Ni0.6Zn0.4Fe2O4)x magnetic nanocomposites with various molar ratios (x = 0.0, 0.1, 0.2, 0.3) have been synthesized by a physical mixing method at different temperatures (T = 700°C to 900°C) and their structure, morphology, and magnetic properties investigated using x-ray diffraction analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and vibrating-sample magnetometry. The results prove that their magnetic properties were strongly influenced by the sintering temperature as well as the molar ratio of hard to soft phase. The magnetization and switching field distribution curves for the nanocomposites sintered above 800°C showed a single smooth hysteresis loop, suggesting the existence of the exchange spring phenomenon. The variation of the coercivity, saturation magnetization, and ratio of remanence to saturation magnetization (Mr/Ms) with the hard-to-soft weight ratio can be explained based on the role of exchange and dipole interactions in the nanocomposites. High maximum energy product (BH)max was obtained for the (BaFe12O19)0.9/(Ni0.6Zn0.4Fe2O4)0.1 sample annealed at 800°C.

Fluorescence Sensing of Nitrite Ions on Polyvinylpyrrolidone/Zinc Oxide Composites Prepared by Impregnation Method

A series of polyvinylpyrrolidone/zinc oxide (PVP/ZnO) composites with different loading amounts of PVP was prepared by an impregnation method. Successful formation of the composites was analyzed by the Fourier transform infrared (FTIR), diffuse reflectance ultraviolet-visible (DR UV-Vis) and fluorescence spectroscopies. Prepared composites were then further tested as fluorescence sensors by conducting quenching studies in the presence of nitrite ions (NO2−). Among the prepared composites, the ZnO with 1% PVP exhibited the highest sensing performance for the NO2−detection (Ksv = 0.07 µM-1). The efficiency of the composite was ca. 1.7 and 1.4 times higher than the bare ZnO and the best composite prepared by the physical mixing method, respectively. These results suggested that impregnation method is a suitable method to prepare the PVP/ZnO composites as fluorescence sensor for the NO2−detection.

Enhanced dielectric properties and energy discharge efficiency of dopamine modified (In0.05Nb0.05)Ti0.9O2 in poly(vinylidene-fluoride) composites

Dopamine@(In0.05Nb0.05)Ti0.9O2/poly(vinylidene-fluoride) (DA@INTO/PVDF) composites are fabricated via a physical mixing method followed by heat treatment. TEM results show that DA is uniformly coated on the surface of INTO particles with a thickness of 10nm. SEM results show that the DA@INTO particles are homogeneously dispersed in PVDF. Compared with INTO/PVDF composites, DA@INTO/PVDF composites exhibit excellent dielectric constant and energy discharge efficiency, which is due to the improved interfacial polarization and reduced leakage current. DA plays an important role in the enhanced dielectric properties of DA@INTO/PVDF composites.

High-performance SOFCs with impregnated Sr2Fe1.5Mo0.5O6-δ anodes toward sulfur resistance

High-performance Sr2Fe1.5Mo0.5O6-δ-Gd0.1Ce0.9O2-δ (SFM-GDC) anode-supported solid oxide fuel cells (SOFCs) have been fabricated by low temperature co-sintering and wet impregnation techniques. Crack-free GDC electrolyte layer was obtained by sintering at low temperature of 1150 °C under Li2O sintering aid. With impregnated SFM nano-catalyst, the cell polarization resistance is significantly reduced compared with that prepared by traditional physical mixing method. Using Ba0.9Co0.7Fe0.2Nb0.1O3-δ (BCFN) cathode, the maximum power densities of the as-prepared SOFCs can reach 445 mW cm−2 at 700 °C when using H2 as fuel and ambient air as oxidant. In addition, the as-prepared SFM-GDC anode exhibits excellent sulfur tolerance toward H2 with 100 ppm H2S. The relatively weak sulfur adsorption on surface and limited lattice interstitial sites within perovskite structure might be the possible sulfur tolerant mechanism of SFM anodes.

Effects of preparation method on the properties of cobalt supported β-zeolite catalysts for Fischer-Tropsch synthesis

The effect of preparation method on the properties of Co supported β-zeolite catalysts was examined in this study. Co-supported β-zeolite catalysts (20wt.% Co as Co3O4) were prepared by impregnation (IMP20), incipient wetness (IW20), physical mixing (PHY20) and precipitation (PCT20) methods and were characterized by various methods including N2 adsorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2 thermal programmed reduction (H2-TPR), and transmission electron microscopy (TEM). Fischer-Tropsch (FT) synthesis was carried out over these catalysts at 230°C and 1MPa in a fixed-bed flow-type reactor. XPS and H2-TPR analyses suggest that the catalysts can be ranked in terms of metal-support interactions: PCT20>IMP20≅IW20>PHY20. On the other hand, based on reducibility, the catalysts were ordered as follows: PHY20>IMP20≅IW20>PCT20. The catalytic activity and product selectivity during FT synthesis were also found to depend on the catalyst preparation method. The catalyst prepared by the incipient wetness method exhibited the highest CO conversion with high liquid production, whereas the physically mixed catalyst showed the lowest CO conversion. All the catalysts produced gasoline-range liquid hydrocarbons (C5–C11) mainly and the selectivity towards i-paraffins was more than 60% in the case of the catalyst prepared by precipitation. Furthermore, the composition of liquid products produced over catalysts prepared by the impregnation and incipient wetness methods were similar to each other. Thus, the results of the study clearly show that the physico-chemical properties of the catalysts as well as catalytic activities and product selectivity during the FT reaction strongly depend on the catalyst preparation method.

Effect of nitrocellulose (NC) on morphology, rheological and mechanical properties of glycidyl azide polymer based energetic thermoplastic elastomer/NC blends

As a new kind of propellants binder, energetic thermoplastic elastomer (ETPE) can make propellant recyclability and environment friendly disposal. The rheological behavior of ETPE binder could be beneficial to identify suitable and safe conditions for processing ETPE propellants. In this paper, ETPE/NC blends with different mass ratios of NC to ETPE were prepared by physical mixing method. The heat of explosion, morphological, thermal, mechanical and rheological properties of the resulted blends were systematically studied. It was found that the heat of explosion of ETPE/NC blends increased with the increasing of NC content. The scanning electron microscopic (SEM) images showed that the NC domains in the blends changed from tiny pieces to fibers with the NC mass ratio increasing, which indicates phase separation in the blends. The tensile mechanical properties of the blends had a peak value when the NC content was 10 wt.%, and then increased with the increasing addition of NC. The thermal behavior made clear that the ETPE and NC were partially miscible. Rheological studies on dynamic strain sweep and frequency sweep demonstrated that the content of NC of the blends had a monotonically effect on the rheological properties of the blends at 130 °C. Rheological studies also showed that the rheology of blends is dependent on temperature. The Cole-Cole and Han plots also confirmed phase separation in the blends.

Facile preparation of hydrogen-bonded supramolecular polyvinyl alcohol-glycerol gels with excellent thermoplasticity and mechanical properties

Facile preparation of tough hydrogels with excellent processability is of great practical importance, but it remains a great challenge. A novel type of hydrogen-bonded supramolecular PVA-glycerol gels is prepared with a very simple physical mixing method, in which glycerol molecules connect PVA chains into bundles by forming many H-bonds. The PVA-glycerol gels show much higher transparency than common PVA gels, due to their lower crystallinities and nanosized microstructures. The physical crosslinking nature and easy gelation at room temperature endow the gels with excellent moldability and thermoplasticity. The easy breaking of the H-bonding provides an effective energy-dissipating mechanism, leading to the high tensile strengths (up to more than 2 MPa), moduli, toughness and fracture energies of the gels. The PVA-glycerol gels also exhibit weaker temperature-dependent mechanical behaviors and excellent cold-resistance. The easy preparation and excellent properties of these gels should facilitate the practical applications of tough gels in many fields.

In Vitro and In Vivo Evaluation of Casein as a Drug Carrier for Enzymatically Triggered Dissolution Enhancement from Solid Dispersions.

Due to its unique properties, such as biodegradability, biocompatibility, high amphiphilic property, and micelle formation, casein (CS) has been increasingly studied for drug delivery. We used CS as a drug carrier in solid dispersions (SDs) and evaluated the effect of its degradation by trypsin on drug dissolution from the dispersions. SDs of CS and mefenamic acid (MA) were prepared by physical mixing, kneading, and coprecipitation methods. In comparison to pure MA, the dispersions were evaluated for drug-protein interaction, loss of drug crystalinity, and drug morphology by differential scanning calorimetry, X-ray diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy. Drug dissolution from the dispersions was evaluated in simulated intestinal fluid as enzyme free and trypsin-enriched media. Furthermore, in vivo drug absorption of MA from CS-MA coprecipitate was evaluated in rats, in comparison with a reference SD of polyethylene glycol and MA (PEG-MA SD). Relative to other CS preparations, CS-MA coprecipitate showed the highest loss of drug crystallinity, drug micronization, and CS-MA interaction. CS remarkably enhanced the dissolution rate and extent of MA from the physical and kneaded mixtures. However, the highest dissolution enhancement was obtained when MA was coprecipitated with CS. Trypsin that can hydrolyze CS during dissolution resulted in further enhancement of MA dissolution from the physical and kneaded mixtures. However, a corresponding retardation effect was obtained for the coprecipitate. In correlation with in vitro drug release, CS-MA coprecipitate also showed significantly higher MA bioavailability in rats than PEG-MA SD.

La0.5Sr0.5CoO2.91@RGO nanocomposites as an effective counter electrode for dye-sensitized solar cells

The role of the counter electrode (CE) in dye-sensitized solar cell (DSSC) is to collect electrons from the external circuit and reduce I 3 − to I − in the electrolyte. In this paper, the perovskite-phase La0.5Sr0.5CoO2.91 (LSCO) nanoparticles were synthesized through a sol–gel method and used as the CE for DSSC. The cell showed a power conversion efficiency (PCE) of 3.24 %. To further improve the PCE of CE of the LSCO nanoparticles, the nanocomposites of the LSCO nanoparticles with reduced graphene oxide (LSCO@RGO) have been prepared via a simply physical mixing method and served as the efficient CE for DSSC. The LSCO@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the positive synergetic effect between LSCO nanoparticles and RGO sheets. As a consequence, the DSSC with the LSCO@RGO nanocomposites CE yielded a PCE of 6.32 %, which is observably higher than that of using pristine LSCO CE (3.24 %) or RGO CE (4.54 %) alone, and up to 88 % of the Pt CE (7.18 %).

Effects of ZnO Addition on Fe<sub>2</sub>O<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> Oxygen Carriers on CH<sub>4</sub> Reduction for Chemical Looping Combustion

Fe2O3/Al2O3/ZnO oxygen carriers with small content ZnO (5 wt% to 10 wt%) were prepared by physical mixing method and were evaluated its capability as an oxygen carrier in a chemical looping combustion. The combustion was conducted by using CH4 as a fuel gas. The reduction process of Fe2O3/Al2O3/ZnO oxygen carrier was carried out in a fixed bed reactor. The solid reduction products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope with EDS Attachment (SEM-EDS). The results show that the reactivity of Fe2O3/Al2O3/ZnO oxygen carriers is greater than that of Fe2O3/Al2O3 which is implied the synergetic effect between ZnO and Fe2O3. XRD results show that the iron oxide in the oxygen carriers is reduced to metallic iron. SEM-EDS also shows that the iron agglomeration is prevented. Consequently, the suitable content of ZnO in oxygen carriers is ranged from 5 wt% to 10 wt%.