Co-reporter:Fengrui Jiang, Laifei Cheng, Yiguang Wang, Xuanxuan Huang
Journal of the European Ceramic Society 2017 Volume 37(Issue 2) pp:823-832
Publication Date(Web):February 2017
DOI:10.1016/j.jeurceramsoc.2016.09.007
The hot corrosion behaviour of barium-strontium aluminosilicates (B1−xSxAS) attacked by Na2SO4 was investigated in the temperature range from 900 to 1100 °C and the weight change was measured as a function of the corrosion time. The surfaces and cross-sections of the corroded samples were observed by scanning electron microscopy in backscattered electron mode and energy-dispersive X-ray spectroscopy. The phase composition was characterized by X-ray diffraction. The results indicate that the hot corrosion of B1−xSxAS by molten Na2SO4 was controlled by a diffusion-reaction mechanism. The strontium and/or barium cations diffused out of their aluminosilicate network, and the vacant sites were filled by sodium cations diffusing into the structure to form a NaAlSiO4 on the top. Due to their smaller radius, the strontium atoms showed a faster diffusion rate than the barium atoms. The corrosion depth significantly increased with the temperature and the strontium concentration in the B1−xSxAS.
Co-reporter:Fengrui Jiang, Laifei Cheng, Yiguang Wang, Xuanxuan Huang
Ceramics International 2017 Volume 43(Issue 1) pp:212-221
Publication Date(Web):January 2017
DOI:10.1016/j.ceramint.2016.09.138
Abstract
In this study, the hot corrosion of barium–strontium aluminosilicate (B1−xSxAS) attacked by calcium–magnesium aluminosilicate (CMAS) was investigated at temperatures in the 1200–1400 °C range. Moreover, a corrosion mechanism based on the interdiffusion of Ba/Sr and Ca cations was also proposed. The proposed corrosion mechanism indicated the diffusion of Ba/Sr cations into the CMAS, and Ca cations into the B1−xSxAS during the hot corrosion process. At 1200 °C, a thin corrosion zone was formed at the interface of B1−xSxAS and CMAS due to weak diffusion of Ba/Sr and Ca cations. Further increase in the temperature led to an enhancement in the interdiffusion of Ba/Sr and Ca cations, thus significantly widening the corrosion zone. Moreover, oriental dendrites, identified as monoclinic B1−xSxAS, were found to precipitate in the molten CMAS. Attributed to the faster diffusion rate of Sr cations compared to that of the Ba cations, B1−xSxAS with a higher Sr content was found to be more prone to CMAS-induced corrosion due to the rapid loss of Sr.
Co-reporter:Zhenbao Li, Yiguang Wang, Linan An
Journal of the European Ceramic Society 2017 Volume 37(Issue 1) pp:61-67
Publication Date(Web):January 2017
DOI:10.1016/j.jeurceramsoc.2016.08.023
Compared to other methods, the fabrication of SiC from precursors allows designing the microstructure and thus the properties of the ceramic material by adjusting the microstructure of the precursor materials. In this study, we used a divinylbenzene (DVB) isomer mixture to modify the polycarbosilane (PCS) precursor via the chemical modification method. The ceramics derived from the modified precursors showed different thermal conductivities. The SiC prepared from PCS without DVB exhibited a very low thermal conductivity at low and at high temperatures. A proper doping with DVB led to clean SiC grain boundaries, resulting in the typical thermal conductivity behaviour of coarse SiC ceramics. An excess doping with DVB led to the precipitation of free carbon around the SiC grains, resulting in a still suitable thermal conductivity which was between the other two values. The results clearly demonstrate that adjusting the thermal properties by modifying the microstructure is a promising approach.
Co-reporter:Meng Zhu, Yanxia Su, Yibo Wu, Min Zhang, Yiguang Wang, Quan Chen, Nanwen Li
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.06.042
•Bulky phenyl and side chain are introduced in polyolefins-based AEMs.•Well defined hydrophilic–hydrophobic separation is exhibited in the AEMs.•The AEMs show high conductivity and excellent alkaline stability.Polyolefin-based anion exchange membranes (AEMs) with well-defined ionic domains for anion transport were synthesized by introducing bulky poly(4-phenyl-1-butene) (P4PB) moieties into quaternized polyolefinic copolymers via heterogeneous catalytic copolymerization of 4-phenyl-1-butene with 11-bromo-1-undecene over a Ziegler–Natta catalyst and subsequent quaternization. Well-defined hydrophobic-hydrophilic separation was observed for the as-obtained membranes, as confirmed by atomic force microscopy (AFM). The membranes showed high hydroxide conductivity (10.4 mS cm−1) despite their low ion exchange capacity (IEC, 0.98 meq g−1). When compared with membranes containing poly(4-methyl-1-pentene) (PMP) or polypropylene (PP) moieties, the membranes obtained herein showed lower conductivities under similar conditions at IEC values higher than 1.2 meq g−1. Excessive swelling of the P4PB membranes resulting from a high water uptake (WU) was assumed to decrease the ion concentration in the membrane. Thus, lower volumetric IEC values were observed for AEMs with IEC higher than 1.2 meq g−1. A maximum hydroxide conductivity of 18.9 mS cm−1 at room temperature was obtained for the P4PB-TMA-43 membrane (IEC = 2.17 meq g−1, WU = 262.4 wt%). Similar to our previous report on polyolefin-based AEMs with PMP or PP moieties, side chains with nine methylene units between the polymer backbone and the quaternary ammonium (QA) cations were very stable and showed no apparent degradation upon storage in a 10 M NaOH aqueous solution at 80 °C for 20 d. We demonstrated that a polyolefin-based molecular architecture combined with poly-QA side chains attached via flexible spacer units with bulky side chain moieties achieved AEMs with efficient phase separation and high alkaline stability characteristics.Download high-res image (355KB)Download full-size image
Co-reporter:Xuqin Li, Feng Chen, Yiguang Wang
Ceramics International 2017 Volume 43, Issue 15(Volume 43, Issue 15) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.ceramint.2017.05.337
The dielectric properties of a polymer-derived amorphous silicon carbonitride were measured at different frequencies and temperatures. The results revealed that the material underwent an interfacial-charge polarization process. This process resulted in an S-shaped frequency dependence of the dielectric constant that reached a colossal value of 2 × 104 at room temperature. With regard to the effect of the temperature on the dielectric properties of this material, the dielectric loss peak corresponding to the interfacial-charge polarization process shifted to higher frequencies with temperature by following a 3-dimentional (3D) hopping mechanism. The unique bi-phased amorphous structure of this material accounted for the observed results.
Co-reporter:Baisheng Ma, Yiguang Wang, Yigao Chen, Yan Gao
Ceramics International 2017 Volume 43, Issue 15(Volume 43, Issue 15) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.ceramint.2017.06.081
The dielectric behavior of polymer-derived amorphous silicon carbonitride was investigated. The material exhibited an interfacial polarization. Although such a polarization exhibited a sharp decrease in the dielectric constant with frequency, the loss peak from this mechanism was not clearly observed because DC conduction dominated the dielectric loss. On the other hand, a sharp increase in the dielectric constant and loss peak were observed at 350 °C at 1 kHz, indicating that the interfacial polarization enhanced at elevated temperatures. This interfacial polarization can be attributed to the migration and accumulation of charge carriers at the interface of matrix and free-carbon phases.
Co-reporter:Meng Zhu;Min Zhang;Quan Chen;Yanxia Su;Zhijie Zhang;Lei Liu;Linan An;Nanwen Li
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 13) pp:2074-2086
Publication Date(Web):2017/03/28
DOI:10.1039/C6PY02213H
N,N-Diethyl-3-(4-vinylphenyl) propan-1-amine (DVPPA), a new monomer bearing a trialkyl amine group, provides versatile functionality to polystyrene (PS) PSm-PDVPPA2n-PSm triblock copolymers. A controlled synthetic strategy minimized chain transfer reactions while enabling the preparation of high molecular weight ABA triblock copolymers with relatively narrow (1.30–1.35) polydispersity indexes (PDIs) via reversible addition–fragmentation chain transfer (RAFT) polymerization between the DVPPA monomer and a difunctional PS macroinitiator. The presence of a tertiary amine functionality and its quaternized derivatives in the central blocks of the triblock copolymers afforded midblock-quaternized triblock co-PSs bearing pendent quaternary ammonium groups. These groups linked to the aromatic backbone with an alkyl spacer chain (3 carbon atoms) serving as steric hindrance shielding ionic centers. This polymer electrolyte with a “side-chain-type” polymer structure was designed by combining phase-separation architecture domains (confirmed by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) analyses) and a crosslinking strategy with the aim to improve both the mechanical and alkaline stability properties. The side chain of this type of polyelectrolyte was incorporated by one quaternary ammonium group terminated with or without a crosslinkable unsaturated bond. After being simply heated at 80 °C for more than 18 h, crosslinked anion-exchange membranes (AEMs) exhibited enhanced tensile strength values (23.8–20.7 MPa) several times higher than those of conventional AEMs. An ionic conductivity of 26.1 mS cm−1 combined with low water uptake (16.5%) and swelling ratio (7.4%) values were achieved at room temperature for highly crosslinked membranes. Moreover, the membranes retained approximately up to 93.0% of their initial high hydroxide conductivity after the alkaline stability test (10 M aqueous NaOH, 80 °C, 20 d), thereby indicating excellent alkaline stability. Furthermore, in view of the good dimensional stability and satisfying mechanical properties of the resulting membranes, this approach that combines phase-separation architectures and crosslinking perfectly overcomes the obstacles blocking the development of AEMs, thereby having a great potential for practical applications.
Co-reporter:Meng Zhu;Min Zhang;Quan Chen;Yanxia Su;Zhijie Zhang;Lei Liu;Linan An;Nanwen Li
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 14) pp:2276-2276
Publication Date(Web):2017/04/04
DOI:10.1039/C7PY90053H
Correction for ‘Synthesis of midblock-quaternized triblock copolystyrenes as highly conductive and alkaline-stable anion-exchange membranes’ by Meng Zhu et al., Polym. Chem., 2017, DOI: 10.1039/c6py02213h.
Co-reporter:Liuyang Duan, Xing Zhao, Yiguang Wang
Ceramics International 2017 Volume 43, Issue 18(Volume 43, Issue 18) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.ceramint.2017.08.175
Carbon fiber reinforced silicon carbide-hafnium carbide (C/SiC-HfC) composites were prepared by reactive melt infiltration (RMI) and precursor infiltration and pyrolysis (PIP) routes. The ablation behaviors of the two composites were investigated and compared under an oxyacetylene torch flame. The C/SiC-HfC composites prepared by PIP showed a better ablation resistance than those synthetized by RMI. Microstructural observations revealed an island distribution of HfC for the sample prepared by RMI, which resulted in SiC being directly oxidized during the ablation process. In contrast, the PIP-prepared sample showed a uniform distribution of HfC, which resulted in SiC being oxidized via the Knudsen diffusion mechanism under ablation. The Knudsen diffusion of oxidants retarded the oxidation process, thereby increasing the ablation resistance of the C/SiC-HfC composites prepared by PIP.
Co-reporter:Xuqin Li, Yiguang Wang
Ceramics International 2017 Volume 43, Issue 16(Volume 43, Issue 16) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.ceramint.2017.07.062
Polymer-derived amorphous-SiCN pyrolyzed at 1200 °C was studied by impedance spectroscopy at different frequencies and temperatures. Obtained impedance spectra were analyzed by using equivalent circuit method. Results revealed that two relaxation effects were involved over the entire studied temperature range, which corresponded to free carbon phase at high frequency and the interface at low frequency. The impedance spectroscopy could be well-fitted by two parallel RC circuits in series. Interface behavior dominated the polarization relaxation process, which was controlled by the resistance as well as the capacitance of interface. All processes performed a 1/T1/4 behavior, which follows a three-dimensional (3D) random hopping mechanism. This paper further found that amorphous-SiCN ceramic materials underwent an interfacial charge polarization process over a frequency range from 0.05 Hz to 10 MHz at different temperatures from −50 to 300 °C.
Co-reporter:Zhenbao Li, Yiguang Wang
Journal of Alloys and Compounds 2017 Volume 709(Volume 709) pp:
Publication Date(Web):30 June 2017
DOI:10.1016/j.jallcom.2017.03.080
•C-SiC composites were successfully prepared from chemically modified precursors.•The composites show a good shielding effectiveness (SE) from RT to 600 °C in air.•The defects in the carbon phase more strongly affect the SE than the conductivity.In this study, we used divinyl benzene (DVB) to modify a polycarbosilane precursor via chemical modification in order to fabricate homogenous graphene-like carbon-silicon carbide (C-SiC) nanocomposites. The electromagnetic interference shielding effectiveness (EMI SE) of the composites was tested over the temperature range from room temperature (RT) to 600 °C in air. With increasing DVB content, the conductivity increased due to the lower degree of defects and the better connectivity of the carbon phase, whereas both the oxidation resistance and the EMI SE of the nanocomposites decreased. The results suggest that the degree of defects has a much stronger influence on the EMI SE than the conductivity. Possessing the highest degree of defects and best oxidation resistance, the C-SiC nanocomposites with a carbon mass percentage of 7.6 wt% showed the highest EMI SE both at RT and 600 °C, indicating that they are a promising candidate for an application as shielding material at high temperatures in air.
Co-reporter:Fengrui Jiang, Laifei Cheng, Yiguang Wang
Ceramics International 2017 Volume 43, Issue 12(Volume 43, Issue 12) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.ceramint.2017.04.045
Rare earth (RE) silicates have been applied as advanced environmental barrier coatings (EBCs) to protect silicon carbide fibers reinforced silicon carbide ceramic matrix from water vapor and molten salt corrosion in engines. This process, however, is limited by volcanic ash corrosion as assessment of ash-induced corrosion is anecdotal and quantitative data are insufficient. In this account, the corrosion behavior of RE monosilicates (RE2SiO5, RE = Y, Lu, Yb, Eu, Gd, and La) by calcium–magnesium–aluminosilicate (CMAS), with similar composition as volcanic ash, was comprehensively investigated. Results indicated that RE2SiO5 could react with CMAS at 1200 °C at the interface, where the products crystallized in CMAS glass. RE2Si2O7 was formed by the reaction between RE2SiO5 and silica (SiO2) in CMAS, which was followed by corrosion of RE2Si2O7 by CMAS. RE2SiO5 with Type B structure showed better resistance toward CMAS than RE2SiO5 with Type A structure. Moreover, RE2SiO5 with larger radii of RE3+ cations led to easy formation of oxyapatite phase; however, RE2SiO5 with smaller radii of RE3+ cations easily formed garnet phase. Besides, smaller radii RE3+ cations induced slower reactions. These findings can contribute to identifying, preventing, and minimizing the damage to matrix components with EBCs caused by volcanic ash.
Co-reporter:Wen Liu, Laifei Cheng, Xiaoqiang Li and Yiguang Wang
Nanoscale 2016 vol. 8(Issue 2) pp:762-765
Publication Date(Web):30 Nov 2015
DOI:10.1039/C5NR06659J
The microstructural effects of SiC swelling, mechanisms of He diffusion and aggregation in C-rich SiC are studied using an in situ helium ion microscope. The additive carbon interface provides improved swelling resistance in SiC to ∼270 nm, and defect formation is not observed until very high He implantation doses.
Co-reporter:Min Zhang, Lin Zhang, Meng Zhu, Yiguang Wang, Nanwen Li, Zhijie Zhang, Quan Chen, Linan An, Yuanhua Lin and Cewen Nan
Journal of Materials Chemistry A 2016 vol. 4(Issue 13) pp:4797-4807
Publication Date(Web):29 Feb 2016
DOI:10.1039/C5TA09949H
A new family of poly(4-methyl-1-pentene) ionomer [PMP-(NH3)xA-y] (x = 1, 2, 3 and A = Cl−, SO42−, PO43−, y = NH3 content) modified (NH3+)xAx− ionic groups has been synthesized. The ionomers were synthesised using either a traditional Ziegler–Natta or a metallocene catalyst for the copolymerisation of 4-methyl-1-pentene and bis(trimethylsilyl)amino-1-hexene. A systematic study was conducted on the effect of the subsequent work-up procedures that can prevent undesirable side reactions during the synthesis of the [PMP-(NH3)xA-y] ionomers. The resulting PMP-based copolymers were carefully monitored by a combination of nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, dielectric properties, and electric displacement–electric field (D–E) hysteresis loop measurements. Our results reveal that the [PMP-(NH3)xA-y] ionomer films show a significantly enhanced dielectric constant (∼5) and higher breakdown field (∼612 MV m−1) as compared with pure PMP films. Additionally, these PMP-based films show good frequency and temperature stabilities (up to 160 °C). A reliable energy storage capacity above 7 J cm−3 can be obtained, and is twice the energy storage capacity of state-of-the-art biaxially oriented polypropylene films, which can be attractive for technological applications for energy storage devices.
Co-reporter:Lei Luo, Yiguang Wang, Liping Liu, Liuyang Duan, Guolin Wang, Yonghong Lu
Carbon 2016 Volume 103() pp:73-83
Publication Date(Web):July 2016
DOI:10.1016/j.carbon.2016.02.085
The ablation behavior is crucial to the application of carbon fiber reinforced silicon carbide (C/SiC) composites in thermal protection systems of spacecraft to enter the atmosphere or to cruise hypersonically in near space. Plasma wind tunnel is a suitable tool to simulate the service conditions of space vehicles. In this study, we systematically studied the ablation behaviors of C/SiC composites in plasma wind tunnel. The oxidation behavior of C/SiC composites in plasma is discussed. The results indicated that the oxidation under atomic oxygen condition dominated at low heat flux and stagnation pressure; however, rapid recession mechanism by sublimation and decomposition of SiC was observed at high heat flux and stagnation pressure. The temperature jump phenomenon during the ablation performed under high heat flux and stagnation pressure was attributed to the exposure of the carbon fibers to the plasma flow after consumption of the SiC coatings.
Co-reporter:Lei Luo, Yiguang Wang, Liuyang Duan, Liping Liu, Guolin Wang
Journal of the European Ceramic Society 2016 Volume 36(Issue 15) pp:3801-3807
Publication Date(Web):November 2016
DOI:10.1016/j.jeurceramsoc.2016.03.017
In order to satisfy the requirements for the thermal protection system to serve at ultrahigh temperatures, carbon fiber reinforced silicon carbide-hafnium carbide (C/SiC-HfC) composites were fabricated by reactive melt infiltration method. The ablation behaviors of C/SiC-HfC composites were examined in plasma wind tunnel. The results indicated that ablation was controlled by the oxidation of HfC-SiC under dissociated oxygen conditions at low heat flux and stagnation pressure. However, a sudden temperature jump caused by the change in the catalytic surface from silica to hafnia was observed at high heat flux and stagnation pressure during ablation. The increase in surface temperature was further accelerated by the burning of carbon fiber and recombination of carbon and nitrogen on it.
Co-reporter:Jiabei He, Yiguang Wang, Lei Luo, Linan An
Journal of the European Ceramic Society 2016 Volume 36(Issue 15) pp:3769-3774
Publication Date(Web):November 2016
DOI:10.1016/j.jeurceramsoc.2016.02.037
ZrB2–SiC(Al/Y) ceramic composites were prepared by hot-pressing a mixture of ZrB2 and polymer-derived SiC doped with either aluminium or yttrium (SiC(Al/Y)). The obtained composites were oxidized at 1700 °C in air. The weight change as a function of the oxidation time was measured to study the oxidation kinetics. It was found that the ZrB2–SiC(Al/Y) composites exhibited significantly improved oxidation resistance, as compared to the composite of ZrB2 with un-doped SiC. The structure of the oxide resulted from the oxidation of the composites was characterized by scanning electron microscopy and X-ray diffraction. The results suggested that the improvement can be attributed to the formation of yttrium/aluminium-doped silica and/or yttrium disilicate, which effectively protect the composites.
Co-reporter:Wen Liu, Laifei Cheng, Yiguang Wang, Hongji Ma
Journal of the European Ceramic Society 2016 Volume 36(Issue 16) pp:3901-3907
Publication Date(Web):December 2016
DOI:10.1016/j.jeurceramsoc.2016.06.033
The development of reaction-bonded SiC (RB-SiC) for an application in nuclear reactor environments has been suspended for many years because of the possible swelling mismatch between SiC and Si under irradiation. Therefore, we studied the residual stresses in RB-SiC due to the irradiation-induced swelling mismatch and the mismatch between the coefficients of thermal expansion. The maximum irradiation-induced swelling stress for the amorphous state was obtained by irradiation with 2 MeV Au2+ ions (1 × 1016 ions/cm2) at room temperature. Utilizing Raman piezo-spectroscopy, nanoindentation tests and thermal expansion coefficient measurements, we demonstrate that the irradiation-induced swelling stress is remarkably high at low temperatures, whereas the thermal stress becomes the dominant residual stress at medium (415 °C < T < 700 °C) or higher temperatures. By optimizing the residual Si content in the RB-SiC, the thermal stress and the irradiation-induced swelling stress can be adjusted and the initiation of cracks can be prevented.
Co-reporter:Dianguang Liu, Yan Gao, Jinling Liu, Kai Li, Fangzhou Liu, Yiguang Wang, Linan An
Journal of the European Ceramic Society 2016 Volume 36(Issue 8) pp:2051-2055
Publication Date(Web):July 2016
DOI:10.1016/j.jeurceramsoc.2016.02.014
SiC whisker-reinforced ZrO2 composite is prepared by flash sintering. The density of the composite obtained at the optimal conditions is close to the theoretical value. SEM observations reveal that the whiskers with well-preserved original morphology are uniformly distributed within the matrix and strongly bonded with ZrO2. The composite exhibits a fracture toughness value higher than SiC–ZrO2 (with 6 mol% Y2O3) made by conventional hot-pressing. These results clearly demonstrate that the flash-sintering can prepare SiCw/ZrO2 composites more effectively.
Co-reporter:Min Zhang, Jinling Liu, Yiguang Wang, Linan An, Michael D. Guiver and Nanwen Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 23) pp:12284-12296
Publication Date(Web):30 Apr 2015
DOI:10.1039/C5TA01420D
A series of novel quaternized polypropylene (PP) membranes with ‘side-chain-type’ architecture was prepared by heterogeneous Ziegler–Natta catalyst mediated polymerization and subsequent quaternization. Tough and flexible anion exchange membranes were prepared by melt-pressing of bromoalkyl-functionalized PP (PP-CH2Br) at 160 °C, followed by post-functionalization with trimethylamine (TMA) or N,N-dimethyl-1-hexadecylamine (DMHDA) and ion exchange. By simple incorporation of a thermally crosslinkable styrenic diene monomer during polymerization, crosslinkable PP-AEMs were also prepared at 220 °C. PP-AEM properties such as ion exchange capacity, thermal stability, water and methanol uptake, methanol permeability, hydroxide conductivity and alkaline stability of uncrosslinked and crosslinked membranes were investigated. Hydroxide conductivities of above 14 mS cm−1 were achieved at room temperature. The crosslinked membranes maintained their high hydroxide conductivities in spite of their extremely low water uptake (up to 56.5 mS cm−1 at 80 °C, water uptake = 21.1 wt%). The unusually low water uptake and good hydroxide conductivity may be attributed to the “side-chain-type” structures of pendent cation groups, which probably facilitate ion transport. The membranes retained more than 85% of their high hydroxide conductivity in 5 M or 10 M NaOH aqueous solution at 80 °C for 700 h, suggesting their excellent alkaline stability. It is assumed that the long alkyl spacer in the ‘side-chain-type’ of 9 carbon atoms between the polymer backbone and cation groups reduces the nucleophilic attack of water or hydroxide at the cationic centre. Thus, PP-based AEMs with long “side-chain-type” cations appear to be very promising candidates with good stability for use in anion exchange membrane fuel cells (AEMFCs).
Co-reporter:Baisheng Ma, Yiguang Wang, Kewei Wang, Xuqin Li, Jinling Liu, Linan An
Acta Materialia 2015 Volume 89() pp:215-224
Publication Date(Web):1 May 2015
DOI:10.1016/j.actamat.2015.02.020
Abstract
The AC conductive behavior of a polymer-derived amorphous silicon carbonitride ceramic was systemically studied. The conductivity exhibited a frequency-dependent switch: at low frequencies, the conductivity is constant and independent of frequency; while at high frequencies, the conductivity increases with frequency, showing a strong relaxation process. Both the frequency-independent conductivity and the characteristic frequency for the relaxation follow the Arrhenius relation with respect to the annealing temperature and follow a band-tail hopping process with respect to the testing temperature. XPS analysis revealed that a sp3–sp2 transition took place in the free-carbon phase of the material with increasing annealing temperature. The activation energy of the transition is similar to those for the Arrhenius relations. The following conductive mechanisms were proposed to account for the observed behaviors: the frequency-independent conductivity in the low frequency region is dominated by a long-distance transport of charge carriers via matrix-free carbon path, enhanced by an electric-field concentration effect; while the frequency-dependent conductivity in the high frequency region is dominated by a interfacial polarization process governed by charge carrier relaxation within the free-carbon phase.
Co-reporter:Xiaoqian Wang, Kewei Wang, Jie Kong, Yiguang Wang, Linan An
Journal of Materials Science & Technology 2015 Volume 31(Issue 1) pp:120-124
Publication Date(Web):January 2015
DOI:10.1016/j.jmst.2014.04.008
In this paper, we reported a novel method for synthesis of non-oxide porous ceramics by using random copolymers as precursors. A silazane oligomer and styrene monomer were used as starting materials, which were copolymerized at 120 °C to form random polysilazane–polystyrene copolymers. The copolymers were then pyrolyzed at 500 °C to obtain porous ceramics by completely decomposing polystyrene (PS) and converting polysilazane (PSZ) into non-oxide Si–C–N ceramics. The obtained material contained a bi-model pore-structure consisting of both micro-sized and nano-sized pores with very high surface area of more than 500 m2/g. We also demonstrated that the pore structure and surface area of the materials can be tailored by changing the ratio of the two blocks. Current results suggest a promising simple method for making multi-scaled porous non-oxide materials.
Co-reporter:Jinling Liu, Ke Zhao, Min Zhang, Yiguang Wang, Linan An
Materials Letters 2015 Volume 143() pp:287-289
Publication Date(Web):15 March 2015
DOI:10.1016/j.matlet.2014.12.099
•Planetary ball milling and spark plasma sintering were combined to synthesize a heterogeneous Mg-based nanocomposite successfully.•A continuous hard phase and an isolated soft phase was confirmed to form the heterogeneous nanocomposite together.•The heterogeneous nanocomposite exhibited significantly increased strength and retained malleability as compared to pure Mg.A heterogeneous Mg-based nanocomposite reinforced with SiC nanoparticles was synthesized by planetary ball milling and subsequently spark plasma sintering. The material has two distinguished phases: a continuous hard phase consisting of Mg and uniformly distributed SiC particles and an isolated soft phase consisting of pure Mg. Mechanical test revealed that the nanocomposite exhibited significantly increased strength and retained malleability as compared to pure Mg. The results also highlight a new strategy for designing Mg-based composites for high performances.
Co-reporter:Kaiyuan Li, Juan Jiang, Yiguang Wang
Materials Science and Engineering: A 2015 627() pp: 241-248
Publication Date(Web):
DOI:10.1016/j.msea.2015.01.009
Co-reporter:Kewei Wang, Baisheng Ma, Xuqin Li, Yiguang Wang, and Linan An
The Journal of Physical Chemistry A 2015 Volume 119(Issue 4) pp:552-558
Publication Date(Web):December 9, 2014
DOI:10.1021/jp5093916
The detailed structural evolutions in polycarbosilane-derived carbon-rich amorphous SiC were investigated semiquantitatively by combining experimental and analytical methods. It is revealed that the material is comprised of a Si-containing matrix phase and a free-carbon phase. The matrix phase is amorphous, comprised of SiC4 tetrahedra, SiCxOx–4 tetrahedra, and Si–C–C–Si/Si–C–H defects. With increasing pyrolysis temperature, the amorphous matrix becomes more ordered, accompanied by a transition from SiC2O2 to SiCO3. The transition was completed at 1250 °C, where the matrix phase started to crystallize by forming a small amount of β-SiC. The free-carbon phase was comprised of carbon nanoclusters and C-dangling bonds. Increasing pyrolysis temperature led to the transition of the free carbon from amorphous carbon to nanocrystalline graphite. The size of the carbon clusters decreased first and then increased, while the C-dangling bond content decreased continuously. The growth of carbon clusters was attributed to Ostwald ripening and described using a two-dimensional grain growth model. The calculated activation energy suggested that the decrease in C-dangling bonds is directly related to the lateral growth of the carbon clusters.
Co-reporter:Jia Liu, Litong Zhang, Qiaomu Liu, Laifei Cheng, Yiguang Wang
Journal of the European Ceramic Society 2014 Volume 34(Issue 8) pp:2005-2012
Publication Date(Web):August 2014
DOI:10.1016/j.jeurceramsoc.2013.12.049
The elastic-modulus-graded environmental barrier coatings (EMG-EBCs) were designed and fabricated to resist crack propagation in this study. The cracks were introduced on the surface of EMG-EBCs by an indentator at room temperature to simulate the damages by foreign object impact. As a comparison, two single-layer coatings of Sc2Si2O7 and barium strontium aluminosilicate (BSAS) were also fabricated and cracks were introduced on their surface with the same conditions of the EMG-EBCs. The results showed that the EMG-EBCs could resist the cracks from propagating through them due to the variation in elastic modulus along the depth beneath the surface, and thus could protect the composites from water-vapour corrosion, while the cracks could cross the single Sc2Si2O7 or BSAS coating to provide channels for oxidative gas diffusing and attacking the composites inside. It is indicated that the EMG-EBCs could effectively resist the foreign object damage.
Co-reporter:Zhibo Lei, Ke Zhao, Yiguang Wang, Linan An
Journal of Materials Science & Technology 2014 Volume 30(Issue 1) pp:61-64
Publication Date(Web):January 2014
DOI:10.1016/j.jmst.2013.04.022
The thermal expansion behavior of aluminum matrix composites reinforced with hybrid (nanometer and micrometer) Al2O3 particles was measured between 100 and 600 °C and compared to theoretical models. The results revealed that the nanoparticle concentration had significant effect on the thermal expansion behavior of the composites. For the composites with lower nanoparticle concentration, their coefficient of thermal expansion (CTE) is determined by a stress relaxation process. While for the composites with higher nanoparticle concentration, their CTE is determined by a percolation process.
Co-reporter:Yiguang Wang, Lei Luo, Jing Sun, Linan An
Corrosion Science 2013 Volume 74() pp:154-158
Publication Date(Web):September 2013
DOI:10.1016/j.corsci.2013.04.037
•ZrB2–SiC(Al) was prepared by hot-pressing the mixture of SiC(Al) and ZrB2.•ZrB2–SiC(Al) has better oxidation resistance than the conventional ZrB2–SiC.•Al doping in SiC could suppress the active oxidation of SiC.•Suppressing active oxidation of SiC improves oxidation resistance of ZrB2–SiC(Al).In this paper, we study the oxidation behaviour of a ZrB2/Al-doped SiC composite at 1500 °C. The composite was prepared by hot-pressing the mixture of ZrB2 and polymer-derived SiC(Al). The oxidation behaviour was studied by measuring the weight change as a function of oxidation time and by observing the structure of the oxide layer. It is shown that the ZrB2–SiC(Al) exhibits different oxidation behaviour and improved oxidation resistance as compared to the conventional ZrB2–SiC without Al-doping. The improvement in oxidation resistance is attributed to that Al-doping could increase the bond strength of the Si–O and suppress the active oxidation of SiC.
Co-reporter:Jia Liu, Litong Zhang, Fei Hu, Juan Yang, Laifei Cheng, Yiguang Wang
Journal of the European Ceramic Society 2013 Volume 33(Issue 2) pp:433-439
Publication Date(Web):February 2013
DOI:10.1016/j.jeurceramsoc.2012.08.032
Yttrium silicate environmental barrier coatings (EBCs) on C/SiC composites were fabricated by using polysiloxanes-derived ceramic process. In order to reduce the free silica in the resultant ceramic coatings, Y2O3 was added as an active filler. The materials with different weight ratios of polysiloxanes to Y2O3 were synthesized. Their coefficient of thermal expansion (CTE) and water-vapor resistance were tested. The results indicated that the composition of 50% Y2O3–50% polysiloxanes (Y50) was suitable to be the EBCs for C/SiC composites. The C/SiC composites coated with Y50 were tested in the water-vapor environments at 1400 °C for 200 h. The results revealed that such a coating could effectively protect the C/SiC composites.
Co-reporter:Jia Liu, Litong Zhang, Qiaomu Liu, Laifei Cheng, Yiguang Wang
Journal of the European Ceramic Society 2013 Volume 33(15–16) pp:3419-3428
Publication Date(Web):December 2013
DOI:10.1016/j.jeurceramsoc.2013.05.030
Environmental barrier coatings (EBCs) are used to prevent oxidation of underlying ceramic matrix composite (CMC) structural components in gas turbines. When the siliceous minerals deposit on the surface of EBCs, a glassy melt of calcium–magnesium–aluminosilicate (CMAS) will be formed, leading to the EBCs degradation. In this study, seven rare-earth disilicates (RE2Si2O7, RE = Yb, Lu, La, Gd, Eu, Sc, and Y) were fabricated to analyze their CMAS corrosion behaviors. The results indicated that the RE2Si2O7 could react with the CMAS in the temperature range of 1250–1350 °C. Reaction zones formed at the interfaces. For the Yb2Si2O7, Lu2Si2O7, La2Si2O7, Eu2Si2O7 and Gd2Si2O7, the reaction zones dissolved into the molten CMAS and separated from the RE2Si2O7. As for the Sc2Si2O7 and Y2Si2O7, the reaction zones could stay at the interface. They could effectively block the molten CMAS to penetrate into the RE2Si2O7 and protect them from CMAS corrosion.
Co-reporter:Jia Liu, Litong Zhang, Juan Yang, Laifei Cheng, Yiguang Wang
Journal of the European Ceramic Society 2012 Volume 32(Issue 3) pp:705-710
Publication Date(Web):March 2012
DOI:10.1016/j.jeurceramsoc.2011.09.029
SiCN–Sc2Si2O7 environmental barrier coatings were fabricated on the surface of C/SiC composites at low temperatures by adding Li2CO3 as sintering aids. With this addition, the fabrication temperature could be lowered about 100–200 °C. The shrinkage of the polysilazane–Sc2Si2O7 bars with and without Li2CO3 was tested by dilatometer. The results indicate that the shrinkage speed of the polysilazane–Sc2Si2O7 bar with Li2CO3 is faster than the one without Li2CO3, indicating that the Li2CO3 greatly promotes the sintering of polysilazane–Sc2Si2O7. Water-vapor corrosion behavior of the SiCN–Sc2Si2O7 coated C/SiC composites was carried out at 1250 °C. The results reveal that the SiCN–Sc2Si2O7 coatings can effectively protect the C/SiC composites. The corrosion resistance of SiCN–Sc2Si2O7 coatings is not degraded by adding Li2CO3.
Co-reporter:Yiguang Wang, Juan Yang, Jia Liu, Shangwu Fan, Laifei cheng
Surface and Coatings Technology 2012 207() pp: 467-471
Publication Date(Web):
DOI:10.1016/j.surfcoat.2012.07.050
Co-reporter:Qiaomu Liu, Litong Zhang, Fengrui Jiang, Jia Liu, Laifei Cheng, Hui Li, Yiguang Wang
Surface and Coatings Technology 2011 205(17–18) pp: 4299-4303
Publication Date(Web):
DOI:10.1016/j.surfcoat.2011.03.039
Co-reporter:Qiaomu Liu, Litong Zhang, Laifei Cheng, Yiguang Wang
Materials Letters 2010 Volume 64(Issue 4) pp:552-554
Publication Date(Web):28 February 2010
DOI:10.1016/j.matlet.2009.12.002
Zirconium carbide and silicon carbide hybrid whiskers were codeposited by chemical vapour deposition using methyl trichlorosilane, zirconium chloride, methane and hydrogen as the precursors. The zirconium carbide and silicon carbide whiskers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The results indicate that the codeposition process is more effective in the presence of methane than in the absence of methane. The codeposition process and the growth of zirconium carbide in the whiskers can be accelerated at high temperature in the presence of methane. A growth model was proposed based on the deposition model of carbon, zirconium carbide and silicon carbide.
Co-reporter:Q. M. Liu;L. T. Zhang;J. Liu;Y. G. Wang
Inorganic Materials 2010 Volume 46( Issue 10) pp:1090-1095
Publication Date(Web):2010 October
DOI:10.1134/S0020168510100110
Thermodynamic equilibrium condensed phases for chemical vapor deposition of ZrC-SiC from the MTS-ZrCl4-CH4-H2 system were calculated by FactSage programs based on Gibbs free energy minimization of the reaction system. The deposition phase diagrams, which indicated the condense phases, were constructed according to the calculation results. The effects of temperature and partial pressure of precursors on the final condensed phases were studied. The results indicate that the codeposition is more effective in the presence of an independent carbon source, CH4, with a reasonable partial pressure than in the absence of CH4. The experimental results are in good agreement with the thermodynamic calculation results.
Co-reporter:Miao Zhu, Yiguang Wang
Materials Letters 2009 Volume 63(Issue 23) pp:2035-2037
Publication Date(Web):30 September 2009
DOI:10.1016/j.matlet.2009.06.041
ZrB2–SiC ceramics are prepared by pressureless sintering using ZrB2 powders and liquid polycarbosilane (LPCS) precursors. The LPCS can effectively reduce the sintering temperature. The phases of the sintered ceramics are characterized by X-ray diffraction, and their morphologies are observed by scanning electron microscopy. From these results, it is learned that LPCS can provide free carbon and silicon at high temperatures. Therefore, the oxides on the ZrB2 surface can be removed by free carbon, and the densification process can be promoted by silicon. These coupled effects make it possible to pressureless sinter the ZB2–SiC ceramics at low temperatures.
Co-reporter:Houbu Li;Litong Zhang;Laifei Cheng;Haitao Kang
Applied Organometallic Chemistry 2009 Volume 23( Issue 1) pp:44-49
Publication Date(Web):
DOI:10.1002/aoc.1469
Abstract
The UV curing process in both air and nitrogen atmosphere for the highly branched polycarbosilane system was investigated by differential scanning photo calorimeter. The UV cured products were characterized by Fourier-transform infrared spectrometry (FTIR). By comparison with the FTIR results of the uncured liquid mixture and the cured samples, the possible cross-linking reactions were determined. The kinetics of the curing systems was studied. The rate constant k was calculated based on the experimental results. The activation energies in different curing conditions were obtained. According to these results, it was learned that the mechanism for the UV curing in nitrogen was controlled by the photolysis of photoinitiator. Comparably, the UV curing process in air was complicated. It was affected by not only the photolysis of photoinitiator, but also oxygen and tripropane glycol diacrylate. Copyright © 2008 John Wiley & Sons, Ltd.
Co-reporter:Qiaomu Liu;Litong Zhang;Laifei Cheng
Journal of Coatings Technology and Research 2009 Volume 6( Issue 2) pp:269-273
Publication Date(Web):2009/06/01
DOI:10.1007/s11998-008-9117-5
Zirconium carbide films were grown on graphite slices by chemical vapor deposition using methane, zirconium tetrachloride, and hydrogen as precursors. The growth rate of zirconium carbide films as a function of temperature was investigated. The morphologies of these films at different temperatures were also observed by scanning electron microscopy. The results indicated that the deposition of zirconium carbide was dominated by gas nucleation at temperatures below 1523 K, and by surface process at temperatures higher than 1523 K. By comparison of the deposition activation energies for zirconium carbide and deposited carbon, it was determined that the carbon deposition was the controlled process during the growing of zirconium carbide films. The effect of temperatures on the morphologies of zirconium carbide films was also discussed, based on the carbon deposition process.
Co-reporter:Yiguang Wang, Wen Liu, Laifei Cheng, Litong Zhang
Materials Science and Engineering: A 2009 524(1–2) pp: 129-133
Publication Date(Web):
DOI:10.1016/j.msea.2009.07.005
Co-reporter:Yiguang Wang;Qiaomu Liu;Litong Zhang
Journal of Coatings Technology and Research 2009 Volume 6( Issue 3) pp:413-417
Publication Date(Web):2009 September
DOI:10.1007/s11998-008-9129-1
Niobium films were deposited on silicon carbide by chemical vapor deposition using niobium chloride and hydrogen at a temperature range of 900–1300°C. The solid-state reactions between the deposited niobium and silicon carbide matrix were studied by examining the obtained films using X-ray diffraction and energy dispersion spectroscopy. The results indicated that niobium silicides could be formed at the beginning, which blocked further reactions between carbon and niobium to form niobium carbides. When the deposition temperature was increased, silicon would diffuse outward, which allowed the formation of niobium carbides. The reaction process and mechanism are discussed based on the thermodynamics and kinetics.
Co-reporter:Houbu Li;Litong Zhang;Laifei Cheng;Haitao Kang
Journal of Materials Science 2009 Volume 44( Issue 4) pp:970-975
Publication Date(Web):2009 February
DOI:10.1007/s10853-008-3216-7
The UV curing behavior of a highly branched polycarbosilane (HBPCS) was studied by differential scanning photo calorimeter (DPC) measurements. 2-Hydroxy-2-Methyl-Phenyl-Propane-1-one (Photocure-1173) was selected as photoinitiator. In order to accelerate the curing reaction rate of polycarbosilane, acrylic reactive diluent tripropane glycol diacrylate (TPGDA) was also added to the polymer system. The effect of TPGDA content, photoinitiator concentration, temperature, light intensity, and the curing atmosphere was investigated. The results indicated that the TPGDA greatly enhanced the reaction rate of the HBPCS system. The TPGDA content, photoinitiator concentration, temperature, and light intensity had their own optimal values to get the maximum ultimate conversion percentage and the reaction rate. The oxygen atmosphere helped to increase the final conversion percentage though it could retard the reaction rate.
Co-reporter:Yiguang Wang;Linan An;L. V. Saraf;C. M. Wang
Journal of Materials Science 2009 Volume 44( Issue 8) pp:2021-2026
Publication Date(Web):2009 April
DOI:10.1007/s10853-009-3269-2
Multilayer thin film of Gd-doped ceria and zirconia have been grown by sputter-deposition on α-Al2O3 (0001) substrates. The films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The Gd-doped ceria and zirconia layers had the fluorite structure and are highly textured such that the (111) plane of the films parallel to the (0001) plane of the α-Al2O3. The epitaxial relationship can be written as \( ( 1 1 1)_{{{\text{ZrO}}_{ 2} /{\text{CeO}}_{ 2} }} //(000 1)_{{{\text{Al}}_{2} {\text{O}}_{3} }} \) and \( [ 1 1{-}2]_{{{\text{ZrO}}_{2} /{\text{CeO}}_{2} }} //[ - 2 1 10]_{{{\text{Al}}_{2} {\text{O}}_{3} }} \), respectively. The absence of Ce3+ features in the XPS spectra indicates that the Gd-doped ceria films are completely oxidized. The ionic conductivity of this structure shows great improvement as compared with that of the bulk crystalline material. This research provides insight on designing of material for low temperature electrolyte applications.
Co-reporter:Fengrui Jiang, Laifei Cheng, Jiaxin Zhang, Yiguang Wang
Journal of Materials Science & Technology (February 2017) Volume 33(Issue 2) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.jmst.2016.12.002
Barium-strontium aluminosilicate (BSAS) and Si/BSAS coatings were fabricated on the surface of C/SiC composites via a two-step laser cladding process. The microstructure, mechanical properties, and the water vapor corrosion behavior of the samples were investigated. The BSAS coating was found to be tightly bonded to the substrate and only a few pores and microcracks were observed. The introduction of a silicon middle layer was revealed to reduce thermal stress and promote the healing of defects formed during the laser cladding process. To evaluate the corrosion resistance, the BSAS and Si/BSAS-coated C/SiC composites were exposed to an atmosphere of 50% H2O and 50% O2 at 1250 °C. The resulting weight change and flexural strength were measured as a function of the corrosion time. The addition of the silicon middle layer below the BSAS top layer resulted in a better resistance to water vapor corrosion. Furthermore, the Si/BSAS-coated samples showed a lower weight loss and a smaller reduction in flexural strength than the BSAS-coated and the uncoated samples during water vapor corrosion. Thus, laser cladding is demonstrated to be an effective and feasible method to fabricate high-quality ceramic coatings on C/SiC composites. The introduction of a silicon middle layer can inhibit defect formation during the laser cladding process and protect the composite from water vapor corrosion.
Co-reporter:Min Zhang, Jinling Liu, Yiguang Wang, Linan An, Michael D. Guiver and Nanwen Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 23) pp:NaN12296-12296
Publication Date(Web):2015/04/30
DOI:10.1039/C5TA01420D
A series of novel quaternized polypropylene (PP) membranes with ‘side-chain-type’ architecture was prepared by heterogeneous Ziegler–Natta catalyst mediated polymerization and subsequent quaternization. Tough and flexible anion exchange membranes were prepared by melt-pressing of bromoalkyl-functionalized PP (PP-CH2Br) at 160 °C, followed by post-functionalization with trimethylamine (TMA) or N,N-dimethyl-1-hexadecylamine (DMHDA) and ion exchange. By simple incorporation of a thermally crosslinkable styrenic diene monomer during polymerization, crosslinkable PP-AEMs were also prepared at 220 °C. PP-AEM properties such as ion exchange capacity, thermal stability, water and methanol uptake, methanol permeability, hydroxide conductivity and alkaline stability of uncrosslinked and crosslinked membranes were investigated. Hydroxide conductivities of above 14 mS cm−1 were achieved at room temperature. The crosslinked membranes maintained their high hydroxide conductivities in spite of their extremely low water uptake (up to 56.5 mS cm−1 at 80 °C, water uptake = 21.1 wt%). The unusually low water uptake and good hydroxide conductivity may be attributed to the “side-chain-type” structures of pendent cation groups, which probably facilitate ion transport. The membranes retained more than 85% of their high hydroxide conductivity in 5 M or 10 M NaOH aqueous solution at 80 °C for 700 h, suggesting their excellent alkaline stability. It is assumed that the long alkyl spacer in the ‘side-chain-type’ of 9 carbon atoms between the polymer backbone and cation groups reduces the nucleophilic attack of water or hydroxide at the cationic centre. Thus, PP-based AEMs with long “side-chain-type” cations appear to be very promising candidates with good stability for use in anion exchange membrane fuel cells (AEMFCs).
Co-reporter:Min Zhang, Lin Zhang, Meng Zhu, Yiguang Wang, Nanwen Li, Zhijie Zhang, Quan Chen, Linan An, Yuanhua Lin and Cewen Nan
Journal of Materials Chemistry A 2016 - vol. 4(Issue 13) pp:NaN4807-4807
Publication Date(Web):2016/02/29
DOI:10.1039/C5TA09949H
A new family of poly(4-methyl-1-pentene) ionomer [PMP-(NH3)xA-y] (x = 1, 2, 3 and A = Cl−, SO42−, PO43−, y = NH3 content) modified (NH3+)xAx− ionic groups has been synthesized. The ionomers were synthesised using either a traditional Ziegler–Natta or a metallocene catalyst for the copolymerisation of 4-methyl-1-pentene and bis(trimethylsilyl)amino-1-hexene. A systematic study was conducted on the effect of the subsequent work-up procedures that can prevent undesirable side reactions during the synthesis of the [PMP-(NH3)xA-y] ionomers. The resulting PMP-based copolymers were carefully monitored by a combination of nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, dielectric properties, and electric displacement–electric field (D–E) hysteresis loop measurements. Our results reveal that the [PMP-(NH3)xA-y] ionomer films show a significantly enhanced dielectric constant (∼5) and higher breakdown field (∼612 MV m−1) as compared with pure PMP films. Additionally, these PMP-based films show good frequency and temperature stabilities (up to 160 °C). A reliable energy storage capacity above 7 J cm−3 can be obtained, and is twice the energy storage capacity of state-of-the-art biaxially oriented polypropylene films, which can be attractive for technological applications for energy storage devices.
