Properties Of Composites Research Articles

Preparation and thermal performance study of a novel hydrated salt composite PCM for space heating

In order to effectively address the mismatch between thermal energy supply and demand in buildings, latent heat storage (LHS) based on phase change material (PCM) stands out as a key technology. While hydrated salt has emerged as a promising PCM, it encounters common issues such as substantial supercooling, phase separation, and low thermal conductivity, hindering its development. To mitigate these limitations, this study focused on modifying Ba(OH)2·8H2O by incorporating various nucleating agents and thickening agents to reduce supercooling, enhancing the composite PCM's thermal properties by introducing expanded graphite (EG) to elevate thermal conductivity. Subsequently, the thermal stability of the PCM was evaluated through accelerated thermal cycling tests, encompassing the assessment of critical thermal parameters, including supercooling degree, enthalpy, and thermal conductivity of the composite PCM. Experimental findings unveiled the effectiveness of incorporating 2 wt% BaCl2·2H2O and 1 wt% CMC to Ba(OH)2·8H2O, effectively diminishing the supercooling degree from 14 °C to 1.42 °C. Further integration of 3.5 wt% EG led to a substantial decrease in the supercooling degree to 0.24 °C. Simultaneously, the addition of EG resulted in an improvement in thermal conductivity, elevating it from 0.62 W/(m·K) to 1.03 W/(m·K), while the enthalpy decreased from 283.68 J/g to 252.81 J/g. Notably, the composite PCM exhibited notable thermal reliability with a latent heat drop of 15.9 % following 1000 accelerated cycles of testing. Moreover, the composite PCM demonstrated superior thermal storage density, measuring at 2.36 times that of traditional paraffin wax, yet with a thermal storage cost merely a quarter of paraffin wax, rendering it more favorable for extensive deployment in building energy systems.

Extracellular matrix stiffness mediates insulin secretion in pancreatic islets via mechanosensitive Piezo1 channel regulated Ca2+ dynamics

The pancreatic islet is surrounded by ECM that provides both biochemical and mechanical cues to the islet β-cell to regulate cell survival and insulin secretion. Changes in ECM composition and mechanical properties drive β-cell dysfunction in many pancreatic diseases. While several studies have characterized changes in islet insulin secretion with changes in substrate stiffness, little is known about the mechanotransduction signaling driving altered islet function in response to mechanical cues. We hypothesized that increasing matrix stiffness will lead to insulin secretion dysfunction by opening the mechanosensitive ion channel Piezo1 and disrupting intracellular Ca2+ dynamics in mouse and human islets. To test our hypothesis, mouse and human cadaveric islets were encapsulated in a biomimetic reverse thermal gel (RTG) scaffold with tailorable stiffness that allows formation of islet focal adhesions with the scaffold and activation of Piezo1 in 3D. Our results indicate that increased scaffold stiffness causes insulin secretion dysfunction mediated by increases in Ca2+ influx and altered Ca2+ dynamics via opening of the mechanosensitive Piezo1 channel. Additionally, inhibition of Piezo1 rescued glucose-stimulated insulin secretion (GSIS) in islets in stiff scaffolds. Overall, our results emphasize the role mechanical properties of the islet microenvironment plays in regulating function. It also supports further investigation into the modulation of Piezo1 channel activity to restore islet function in diseases like type 2 diabetes (T2D) and pancreatic cancer where fibrosis of the peri-islet ECM leads to increased tissue stiffness and islet dysfunction.

Sm-doped ZnO with enhanced photocatalytic performance toward destruction of RhB

In this work, Sm-doped ZnO was prepared by a Sol-Gel method. The structure, morphology, composition and optical properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), surface photovoltage spectrum (SPS) and X-ray photoelectron spectros­copy (XPS). Sm-doping results in high specific surface area and boosted photogenerated carriers separation efficiency, and produces more active free radicals to participate in the photocatalytic reaction. Photocatalytic activities of the samples toward removal of rhodamine B(RhB) were evaluated under UV light irradiation, the results display that Sm-doped ZnO shows higher photocatalytic activity than the reference ZnO.

The structural and optical properties of PVA/CMC copolymer cured by UV irradiation for different times

Poly(vinyl alcohol) (PVA)/carboxymethylcellulose (CMC) blend films with equal amounts (0.25 g) of both polymers were prepared through a simple and low-cost comparative casting method. Then, the PVA/CMC blend films were exposed to ultraviolet (UV) radiation for varied time intervals (1, 12, 26, 32, 40 and 48 h). The UV-irradiation effect on the physical properties of as-prepared films, including the structure, morphology, composite and optical properties (transmittance, absorbance and band gap (E g)), was examined. Field-emission scanning electron microscopy images showed that UV irradiation had a strong effect on the shape of PVA/CMC blend films. The X-ray diffraction patterns showed various crystalline qualities in the microstructure of as-synthesized samples. The Fourier transform infrared spectra showed that the UV-irradiation time and CMC film had a positive impact on the blend polymer structure since covalent connections were formed between CMC and PVA. Furthermore, the analysis results of optical inspections showed that the absorbance of the PVA/CMC films improved with an increment in irradiation time from 1 to 40 h. Important tuning of the E g values of blend films was realized. It showed a slight increase from 4.64 to 4.84 eV with increasing irradiation time from 1 to 40 h. The E g value (3.21 eV), however, displayed an inverted behavior due to an increased irradiation time of 48 h. This reduction could be ascribed to the creation of defects inside the blend band gap. Finally, the physical property modification of PVA/CMC blend film using UV irradiation made it an amazing contender in the optoelectronic field.

Effect of post-weld heat treatment on the microstructure, phase composition and mechanical properties of dissimilar Al-Mg-Li/Al-Cu-Li laser welded joints

Butt joints of the V-1461 and 1424 heat treated aluminum–lithium alloys of the third generation were welded with a CO2 laser and studied in detail for the first time. In particular, spatial distributions of the formed phases and their evolution upon post-weld heat treatment (PWHT), determining the mechanical properties of the joints, were investigated. The PWHT included quenching and subsequent artificial aging. The key factors, affecting the metallurgical processes in a weld pool, were the following: 1) the alloying elements and the thermal properties of the alloys, 2) the dynamics of the local non-equilibrium melting, the convective transfer of the molten metal in the weld pool and its subsequent solidification, 3) the cooling rate, and 4) the PWHT procedure. By using synchrotron radiation and scanning electron microscopy, new θ(Al2Cu), T1(Al2CuLi) and S1(Al2MgLi) phases were found in the weld metal that were absent in both base metals. This phenomenon reduced the mechanical properties of the joints to the levels, corresponding to about 50 % of the 1424 alloy as the weakest one. Quenching contributed to the formation of the δ′(Al3Li) strengthening phase in the weld metal. As a result, the ultimate tensile strength increased up to 70 % and elongation up to 95 % of the corresponding levels of the 1424 alloy. Artificial aging made it possible to form the T1(Al2CuLi) strengthening phase, to increase the content of the δ′(Al3Li) one, as well as to improve the mechanical properties of the joint. In this case, the ultimate tensile strength was 411 MPa, the yield point was 327 MPa and elongation was 1.7 %. These values were close to those for the 1424 alloy (about 80 %, 89 % and 23 %, respectively).

Determination of Mechanical Properties of Hybrid Composite

Abstract: Manufacturing of composite laminates is the peculiar member of science that encounter its immense utilization in various industrial areas such as sporting, automotive, aerospace and marine industries. The superior properties of composites such as stiffness, better mechanical properties, low density, and lightweight make it a candidate in engineering applications. The continuous research in this area is due to the need for seeking alternative materials with increased performance. In this report, the basalt fiber E-glass reinforced composite mechanical properties has investigated. The basalt fiber E-glass composite was formulated with hand layup moulding technique. Mechanical properties such as tensile, flexural strength and impact strength of the basalt fiber E-glass composite have been analysed

GARLIC: Nature's potent antifungal and antibacterial ally - cream formulation and evaluation

In the pursuit of effective and safe treatments for infectious diseases, herbal remedies have garnered significant attention due to their diverse phytochemical composition and potential therapeutic properties. This study aimed to explore the phytochemical profile and evaluate the antibacterial and antifungal properties of herbal garlic extracts. Traditional natural products continue to be sought after for their bioactive compounds, which offer promising avenues for therapeutic intervention in both human and veterinary medicine. Our investigation not only sheds light on the regional variation of stomach disease occurrence, highlighting the role of dietary factors, but also underscores the importance of herbal preparations in medicinal practice. By combining various plant classes, herbal formulations can exert localized effects upon application, penetrating the skin or mucous membranes to target underlying conditions. The effectiveness of these combined medications may lie in their synergistic mechanisms, offering a comprehensive therapeutic approach. This research contributes valuable insights into the potential of herbal remedies as adjuncts or alternatives to conventional treatments, paving the way for further exploration in infectious disease management and prevention strategies.

Bioinspired poly-dopamine/nano-hydroxyapatite: an upgrading biocompatible coat for 3D-printed polylactic acid scaffold for bone regeneration.

Poly-lactic acid (PLA) has been proposed in dentistry for several regenerative procedures owing to its biocompatibility and biodegradability. However, the presence of methyl groups renders PLA hydrophobic, making the surface less ideal for cell attachment, and it does not promote tissue regeneration. Upgrading PLA with inductive biomaterial is a crucial step to increase the bioactivity of the PLA and allow cellular adhesion. Our purpose is to evaluate biocompatibility, bioactivity, cellular adhesion, and mechanical properties of 3D-printed PLA scaffold coated with poly-dopamine (PDA) and nano-hydroxyapatite (n-HA) versus PLA and PLA/n-HA scaffolds. The fused deposition modelling technique was used to print PLA, PLA with embedded n-HA particles, and PLA scaffold coated with PDA/n-HA by immersion. After matrices characterization for their chemical composition and surface properties, testing the compressive strength was pursued using a universal testing machine. The bioactivity of scaffolds was evaluated by monitoring the formation of calcium phosphate compounds after simulated body fluid immersion. The PLA/PDA/n-HA scaffold showed the highest compressive strength which was 29.11 ± 7.58 MPa with enhancing calcium phosphate crystals deposition with a specific calcium polyphosphate phase formed exclusively on PLA/PDA/n-HA. With cell viability assay, the PDA/n-HA-coated matrix was biocompatible with increase in the IC50, reaching ⁓176.8 at 72 without cytotoxic effect on the mesenchymal stem cells, promoting their adhesion and proliferation evaluated by confocal microscopy. The study explored the biocompatibility, bioactivity, and the cell adhesion ability of PDA/n-HA coat on a 3D-printed PLA scaffold that qualifies its use as a promising regenerative material.

Item performance of the scale for the assessment and rating of ataxia in rare and ultra-rare genetic ataxias.

The Scale for the Assessment and Rating of Ataxia (SARA) is widely used for assessing the severity and progression of genetic cerebellar ataxias. SARA is now considered a primary end point in several ataxia treatment trials, but its underlying composite item measurement model has not yet been tested. This work aimed to evaluate the composite properties of SARA and its items using item response theory (IRT) and to demonstrate its applicability across even ultra-rare genetic ataxias. Leveraging SARA subscores data from 1932 visits from 990 patients of the Autosomal Recessive Cerebellar Ataxias (ARCA) registry, we assessed the performance of SARA using IRT methodology. The item characteristics were evaluated over the ataxia severity range of the entire ataxia population as well as the assessment validity across 115 genetic ARCA subpopulations. A unidimensional IRT model was able to describe SARA item data, indicating that SARA captures one single latent variable. All items had high discrimination values (1.5-2.9) indicating the effectiveness of the SARA in differentiating between subjects with different disease statuses. Each item contributed between 7% and 28% of the total assessment informativeness. There was no evidence for differences between the 115 genetic ARCA subpopulations in SARA applicability. These results show the good discrimination ability of SARA with all of its items adding informational value. The IRT framework provides a thorough description of SARA on the item level, and facilitates its utilization as a clinical outcome assessment in upcoming longitudinal natural history or treatment trials, across a large number of ataxias, including ultra-rare ones.

Thermo‐mechanical properties of epoxy composites filled with inorganic particulate fillers for robust solder mask application

AbstractFiller components play a crucial role as thermo‐mechanical reinforcement to the epoxy‐based solder mask, ensuring effective insulation and passivation. This study investigates the impact of different inorganic filler types (talc, silica (SiO2), boron nitride (BN) and barium sulfate (BaSO4)) and loadings (5 and 15 wt%) on the tensile and thermal properties of the epoxy composites. The composites were blended, cast and thermally cured. Of these composites, only 15 wt% SiO2/epoxy composite exhibits notable increments in both tensile strength and modulus, surpassing unfilled epoxy by 11.65% and 31.9%, respectively. It also displays the highest elongation at break, supported by small particle size, high specific surface area and minimal void volume fraction. For thermal tests, the addition of all fillers increases the storage modulus in both glassy and rubbery regions, especially 15 wt% talc/epoxy composite with 30.09% increment at 25 °C. Additionally, all fillers raise the glass transition temperature (Tg), notably improving it by 9 °C in the 15 wt% BN/epoxy composite. Moreover, their inclusion generally enhances the onset decomposition temperature (Tonset) and reduces weight loss during decomposition. © 2024 Society of Chemical Industry.

Effect of Layered Double Hydroxide and Its Localization on the Structure and Properties of PBAT/PPC Composites

AbstractThe blends of poly(butylene adipate‐co‐terephthalate) (PBAT), poly(propylene carbonate) (PPC), chain extender (ADR) and layered double hydroxides (LDH) are prepared by different extrusion methods. Effects of LDH and its distribution on rheology, phase morphology, mechanical properties, water vapor barrier properties and food preservation properties are investigated. Results show that when PBAT, PPC and LDH are mixed directly, LDH is preferentially distributed in the PBAT phase. When LDH are mixed with PPC firstly and then further with PBAT, LDH mostly migrates to the interface of PBAT and PPC. The epoxy groups of ADR react with the terminal groups of the polymers to improve the interfacial compatibility. Adding LDH, the mechanical properties and barrier properties of the materials are improved and by premixing of PPC and LDH, properties of composites are further improved. Compared with PBAT/PPC blends, the tensile strength and elongation at break of PBAT/PPC(LDH‐0.5)/ADR increased by 25.2% and 15.3%, respectively. The banana packaged in PBAT/PPC/LDH films maintains good freshness. It illustrates that PBAT/PPC(LDH)/ADR composites have a good application prospect in the field of barrier and food packaging based on their excellent mechanical, barrier and preservation properties.This article is protected by copyright. All rights reserved

Evaluating the Impact of Environmental and Operational Conditions on the Characteristics of CFRP Epoxy Composites

The purpose of this study is to determine the material properties of CFRP composites in the form of a fabric for the construction of racing car bodywork. This work focused on the determination of the strength and tribological properties as well as investigating the effects of the operating environment on the developed material. Three material variants, differing in the number of layers used to produce the reinforcement, were used in this study. The tests were carried out on two-/three-/four-layer sheets produced by infusion. Due to the later use of the tested composites for the sheathing of a racing car, the results obtained were analysed in terms of the most favourable strength properties while keeping the weight as low as possible. In this study, the hardness, impact strength, and tensile and bending stresses of the developed composites were examined. In addition to the strength properties, the density, the effects of immersion in water, and the composite’s resistance to staining and friction in the presence of aggressive media were also checked. The structure and the breakthroughs resulting from the strength tests were observed using a stereoscopic microscope. The material’s resistance to sunlight and UVB was also tested.

An Experimental Study of the Properties of Carbon Fiber/Epoxy Composites Mixed with Rubber Granules

In this research work, the mechanical properties of hybrid composites reinforced with woven carbon fiber mats particulated with natural rubber powders as fillers in the epoxy resin matrix were investigated. The specimens were prepared by the hand-layup process followed by a vacuum bag moulding process. The vacuum moulding reduces the voids or cavities in the hybrid composites. The natural rubber powder was added in different weight proportions (5%, 10%, 15%, and 20%), and carbon fiber is added in 20% for all the specimens. Experiments such as tension testing, flexural testing, water absorption/acid corrosion/base corrosion tests, dynamic mechanical analysis (DMA), and scanning electron microscopic (SEM) analysis were conducted to evaluate the epoxy carbon rubber (ECR) composites. The tensile and flexural test findings demonstrated that the addition of 10% natural rubber particles gave better results as compared with other proportions. The water/acid/base absorption test findings reveal that the ECR composites are not affected by water/acid/base. The DMA teat findings show that ECR composites having 10% natural rubber have higher damping factor, storage, and loss modulus. The SEM analysis shows that ECR hybrid composites with 10% rubber particles contained a uniform distribution of rubber particles over reinforcement, and also, there were no cracks and voids. According to this research findings, ECR hybrid composites with 10% natural rubber particles prepared during the vacuum bag moulding process can be used to prepare aerospace interior components.

Effect of holmium oxide nanoparticle on the mechanical properties of epoxy resin composites

In this study, holmium oxide/epoxy resin (Ho2O3/EP) nanocomposites were prepared by using different additions of Ho2O3 nanoparticles as nanofiller. The surface-modification treatment of Ho2O3 was applied with a silane coupling agent (SCA) to improve the interfacial combination between Ho2O3 and EP. The effect of SCA treatment on the chemical structure of Ho2O3 was investigated using Fourier transform infrared spectroscopy (FTIR). The effects of Ho2O3 nanoparticle and SCA treatment on the mechanical properties of the nanocomposites were studied. The fracture morphology of the EP nanocomposites was observed by scanning electron microscopy (SEM) to explore the failure mechanism of the EP nanocomposites with Ho2O3 nanoparticle. The experimental results show the tensile and flexural strengths of the nanocomposites are improved when Ho2O3 content is 1 wt. %. The tensile and flexural strengths were increased to 73.42 MPa and 130.85 MPa, respectively. But on further increase in Ho2O3 content of 1.5 wt. %, the tensile and flexural strengths were reduced. The SCA treatment could increase the interfacial bonding by containing C-H and Si-O functional groups, promoting the tensile properties, flexural properties, impact toughness, and fracture properties of the nanocomposites.

Microstructure and tribological properties of aluminum matrix composites reinforced with ZnO–hBN nanocomposite particles

Abstract In this study, pure and hBN-doped ZnO nanoparticles were synthesized by sol–gel method. ZnO–hBN nanoparticles were mixed with pure aluminum powders and samples were prepared using powder metallurgy processing parameters. It was observed that Al, ZnO, and hBN nanocomposite particles formed homogeneously. With the addition of ZnO–hBN, significant changes occurred in hardness, wear, and friction coefficient values compared to pure Al samples. The highest hardness value in the samples is mesh. It was obtained as 105 HB in 10 wt.% hBN added sample. In the wear tests, it is seen that the wear resistance is seven times higher in the 1 wt.% hBN added sample compared to the pure Al sample, while the friction coefficient decreases with the increase of the hBN additive.

Polyamide 6/carbon fibre composite: An investigation of carbon fibre modifying pathways for improving mechanical properties

Carbon fibre-reinforced polyamide 6 (PA6) composites exhibit exceptional mechanical properties, making them a highly attractive material option for various industries. Their ability to combine the advantages of carbon fibres with the versatility of PA6 provides opportunities for lightweight, high-performance applications. This work presented the fabrication of a PA6/carbon fibre composition with carbon fibre was modified by two different chemicals: nitric acid and diglycidil ether bisphenol A (DGEBA). The tensile strength at break, flexural strength, Rockwell hardness and Izod impact were measured to compare the mechanical properties of composites based on the PA6 matrix with two different modified carbon fibres. The morphology of PA6-based composite with different modified carbon fibres was observed by scanning electron microscopy. The results showed that PA6 is more compatible with acid-modified carbon fibre than DGEBA-modified carbon fibre and unmodified carbon fibre. In comparison to composite materials containing unmodified carbon fibre and DGEBA-modified carbon fibre, composite containing acid-modified carbon fibre increase tensile strength (16–38% and 7–15%, respectively), flexural strength (18–66% and 51–70%, respectively), Izod impact (23–65% and 32–78%, respectively) and Rockwell hardness (50–400% and equivalence, respectively).

Diaminodiphenylmethane modified zirconium phosphate: A new strategy for trace addition to improve flame retardancy, smoke inhibition, and compatibility of epoxy resins

AbstractHigh‐efficient flame retardants (ZrP‐DDM) were synthesized successfully via ion‐exchange method, using diaminodiphenylmethane (DDM) modified layered zirconium phosphate (α‐ZrP). Trace addition of ZrP‐DDM in epoxy resins (EP) can enhance the flame‐retardant, smoke‐inhibition, mechanical, and thermal stability properties of EP composites. As shown in the results, ZrP‐DDM exhibits a better synergistic effect than α‐ZrP, and the EP composites containing 0.5 wt% ZrP‐DDM (EP/0.5ZrP‐DDM) show excellent flame‐retardant and smoke‐inhibition properties. Especially, EP/0.5ZrP‐DDM possesses a limiting oxygen index (LOI) of 33.7% with UL94 V‐1 rating, while the EP composites containing 0.5 wt% ZrP (EP/0.5ZrP) has a LOI of 30.1% and fails to achieve the UL94 rating. Furthermore, the peak heat release rate (PHRR), total heat release rate (THR), and smoke density rating of EP/0.5ZrP‐DDM decrease by 10.2%, 3.7%, and 8.2% compared with EP/0.5ZrP. Based on condensed‐phase product analysis, EP/ZrP‐DDM sample provides a gas source for intumescent char layer, and produces a stable phosphorus‐rich crosslinking structures during combustion, thus decreasing the fire hazard of the composite material. Meanwhile, the introduction of ZrP‐DDM has a less impact on tensile strength of EP composites compared with α‐ZrP, suggesting the addition of ZrP‐DDM effectively enhances the compatibility with the EP matrix, thereby maintaining excellent mechanical properties of the EP matrix.

Study on the Optimization of the Preparation Process of ZM5 Magnesium Alloy Micro-Arc Oxidation Hard Ceramic Coatings and Coatings Properties

Hard ceramic coatings were successfully prepared on the surface of ZM5 magnesium alloy by micro-arc oxidation (MAO) technology in silicate and aluminate electrolytes, respectively. The optimization of hard ceramic coatings prepared in these electrolyte systems was investigated through an orthogonal experimental design. The microstructure, elemental composition, phase composition, and tribological properties of the coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and tribological testing equipment. The results show that the growth of the hard ceramic coatings is significantly influenced by the different electrolyte systems. Coatings prepared from both systems have shown good wear resistance, with the aluminate electrolyte system being superior to the silicate system in performance. The optimized formulation for the silicate electrolyte solution has been determined to be sodium silicate at 8 g/L, sodium dihydrogen phosphate at 0.2 g/L, sodium tetraborate at 2 g/L, and potassium hydroxide at 1 g/L. The optimized formulation for the aluminate electrolyte solution consists of sodium aluminate at 5 g/L, sodium fluoride at 3 g/L, sodium citrate at 3 g/L, and sodium hydroxide at 0.5 g/L.

Enhancing gamma radiation shielding properties of iron metal and natural rubber composites

AbstractA comparative study was conducted to investigate the gamma and neutron radiation shielding properties of composites made from iron metal (micro and nano) dispersed within natural rubber (NR). The aim was to attenuate neutron and γ‐rays. The study utilized the gamma spectroscopy technique and the Monte Carlo FLUKA code. To assess the gamma ray shielding, a 3×3 Nal (Tl) detector and radioactive point sources were employed. Two comparative studies were carried out, one using Fe loaded NR (Fe/NR) composites in microsize and the other using Fe/NR composites in nanosize. The objective was to determine the impact of iron nanoparticles on the shielding ability of the composites. The findings revealed that the Fe/NR composites in nanosize exhibited superior gamma radiation shielding ability compared with the Fe/NR composites in microsize. These results were supported by the FLUKA Monte Carlo code, which demonstrated good agreement with both the experimental and theoretical XCOM data.

Photorefractivity and photocurrent dynamics of triphenylamine-based polymer composites

The photorefractive properties of triphenylamine polymer-based composites with various composition ratios were investigated via optical diffraction, response time, asymmetric energy transfer, and transient photocurrent. The composite consisted of a photoconductive polymer of poly((4-diphenylamino)benzyl acrylate), a photoconductive plasticizer of (4-diphenylamino)phenyl)methanol, a sensitizer of [6,6]-phenyl-C61-butyric acid methyl ester, and a nonlinear optical dye of (4-(azepan-1-yl)-benzylidene)malononitrile. The photorefractive properties and related quantities were dependent on the composition, which was related to the glass transition temperature of the photorefractive polymers. The quantum efficiency (QE) of photocarrier generation was evaluated from the initial slope of the transient photocurrent. Transient photocurrents were measured and showed two unique peaks: one in the range of 10−4 to 10−3 s and the other in the range of 10−1 to 1 s. The transient photocurrents was well simulated (or reproduced) by the expanded two-trapping site model with two kinds of photocarrier generation and recombination processes and two different trapping sites. The obtained photorefractive quantity of trap density was significantly related to the photoconductive parameters of QE.