PHYSICAL CHEMISTRY CHEMICAL PHYSICS
·
2019
·Vol. 21
·期 32
·17801-17810
·
IF 3.567
Qiushi Song,Zheng Zhang,Hongwei Xie,Huayi Yin,Zhiqiang Ning
The carbonization of transition metals in molten salts was performed to study the effect of electrochemical polarization and molten salt medium on the carbonization process. The carbonization of niobium (Nb) has been systemically investigated in Ar atmosphere and molten salts. The effect of particle size and structure of the starting materials, molten salt medium, and electric field on the formation of NbC was studied to reveal the dynamic barriers in the carbonization process. A native oxide layer and/or niobate derivatives generated on the Nb particles are the main barriers for the mass transfer of carbon and Nb towards each other. The results showed that molten salts can accelerate the formation of NbC by enhancing the diffusion of carbon, and the kinetic barrier can be effectively eliminated by supplying negative polarization to the cathode in molten salts to remove the oxide barriers, thereby enhancing carbonization. Besides Nb, tungsten (W), molybdenum (Mo), titanium (Ti), and tantalum (Ta) can also be carbonized in molten salts with the assistance of an applied electric field.
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高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2019
·
IF 14.229
Zizheng Ai,Yongliang Shao,Bin Chang,Lei Zhang,Jianxing Shen,Yongzhong Wu,Baibiao Huang,Xiaopeng Hao
As a metal-free polymeric semiconductor, graphitic carbon nitride (g-C 3 N 4 ) is a promising candidate for photocatalytic water splitting but suffers from the insufficient optical absorption and sluggish utilization of photocarriers. Herein, based on the energy band engineering theory, a new design philosophy of tunable p-n homojunction is proposed and realized in a novel P-doped g-C 3 N 4 (PCN) material. Through regulating the tendency of transformation in p-n homojunction, a strong internal electric field is built and integrated with two secondary internal electric fields by further decorating with Ti 3 C 2 , leading to the formation of a triple-internal electric field system. Thus the spatial separation efficiency of photocarriers is improved and their lifetime is prolonged. The specific photocatalyst exhibits excellent overall water splitting performance in pure water with a notable quantum yield. This work presents a peculiar concept of adjustable p-n homojunction and holds great significance for the rational design of advanced photocatalyst in water splitting.
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高影响因子
Journal of Advanced Ceramics
·
2017
·Vol. 7
·期 1
·41-49
·
IF 1.198
Peng Le,Zhang Kuibao,He Zongsheng,Yin Dan,Xue Jiali,Xu Chen,Zhang Haibin
In this research, Zr-doped Gd 2 Ti 2 O 7 pyrochlores, with the composition of Gd 2 (Ti 1- x Zr
x
) 2 O 7 , were firstly synthesized by self-propagating high-temperature synthesis plus quick pressing (SHS/QP) using CuO as the oxidant and Ti as the reductant. To improve the radiation resistance of titanate–pyrochlore, up to 35 at% Zr was incorporated to substitute the Ti site of Gd 2 Ti 2 O 7 pyrochlore (Gd 2 (Ti 0.75 Zr 0.35 ) 2 O 7 ). XRD and SEM microstructural characterizations showed the formation of a composite ceramic with the major pyrochlore phase and the minor Cu phase. The generated temperature of samples decreased from 1702 to 1011°C with increasing Zr content. The effects of sintering temperature and pressure time on phase composition and microstructure were systematically studied. Besides, the influence of thermal transmission on the whole combustion process was also explored. The pyrochlore-based waste form possessed high bulk density of 6.25 g/cm 3 and Vickers hardness of 10.81 GPa. The MCC-1 leaching test showed the normalized elemental leaching rates (42 d) of Cu, Gd, and Zr are 1.27×10 -2 , 1.33×10 -3 , and 8.44×10 -7 g·m -2 ·d -1 , respectively.
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高影响因子
JOURNAL OF ELECTRONIC MATERIALS
·
2017
·Vol. 47
·期 6
·3248-3253
·
IF 1.579
Chen Jun-Liang,Liu Chengyan,Miao Lei,Gao Jie,Zheng Yan-yan,Wang Xiaoyang,Lu Jiacai,Shu Mingzheng
With excellent high-temperature stability (up to 1000 K) and favorable electrical properties for thermoelectric application, TiNiSn-based half-Heusler (HH) alloys are expected to be promising thermoelectric materials for the recovery of waste heat in the temperature ranging from 700 K to 900 K. However, their thermal conductivity is always relatively high (5–10 W/mK), making it difficult to further enhance their thermoelectric figure-of-merit ( ZT ). In the past decade, introducing nano-scale secondary phases into the HH alloy matrix has been proven to be feasible for optimizing the thermoelectric performance of TiNiSn. In this study, a series of TiNiSn-based alloys have been successfully synthesized by a simple solid-state reaction. The content and composition of the heterogeneous phase (TiNi 2 Sn and Sn) is accurately regulated and, as a result, the thermal conductivity successfully reduced from 4.9 W m −1 K −1 to 3.0 Wm −1 K −1 (750 K) due to multi-scale phonon scattering. Consequently, a ZT value of 0.49 is achieved at 750 K in our TiNiSn-based thermoelectric materials. Furthermore, the thermal stability of TiNiSn alloys is enhanced through reducing the Sn substance phase.
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高影响因子
ACS Nano
·
2017
·
IF 13.942
Guodong Zou,Qingrui Zhang,Carlos Fernandez,Gang Huang,Jianyu Huang,Qiuming Peng
Rational design of heterogeneous electrode materials with hierarchical architecture is a potential approach to significantly improve their energy densities. Herein, we report a tailored microwave-assisted synthetic strategy to create heterogeneous hierarchical Ti3SiC2@C-containing Na2Ti7O15 (MAX@C-NTO) composites as potential anode materials for high-performance sodium storage in a wide temperature range from 25 to 80 °C. This composite delivers first reversible capacities of 230 mAh g–1 at 200 mA g–1 and 149 mAh g–1 at 3000 mA g–1 at 25 °C. A high capacity of ∼93 mAh g–1 without any apparent decay even after more than 10 000 cycles is obtained at an ultrahigh current density of 10 000 mA g–1. Moreover, both a high reversible capacity and an ultralong durable stability are achieved below 60 °C for the same composites, wherein a 75.2% capacity retention (∼120 mAh g–1 at 10 000 mA g–1) is achieved after 3000 cycles at 60 °C. To the best of our knowledge, both the sodium storage performances and the temperature tolerances outperform those of all the Ti-based sodium storage materials reported so far. The superior sodium storage performances of the as-synthesized composites are attributed to the heterogeneous core–shell architecture, which not only provides fast kinetics by high pseudocapacitance but also prolongs cycling life by preventing particle agglomeration and facilitates the transportation of electrons and sodium ions by large micro/mesopore structure.
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高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Jiale Zhang,Jianjun Chen,Jinyu Guo,Hao Chen,Longbo Xue,Chenyu Li
In this study, silicon nitride (Si 3 N 4 ) powders with high α-phase content and rod-like crystal morphologies were synthesized via self-propagating high-temperature synthesis (SHS) in a low-pressure nitrogen atmosphere (0.2 MPa), using silicon and Si 3 N 4 powders as reactants, with magnesium powder serving as an igniter. The influence of different ratios of silicon to silicon nitride on the phase composition, crystal morphology, and sintering activity of the synthesized Si 3 N 4 powders was systematically investigated. The results demonstrated that controlling the silicon-to-silicon nitride ratio under low-pressure conditions significantly affects the formation of α-phase Si 3 N 4 and the resulting microstructure of the powders. A low-pressure nitrogen atmosphere was adopted based on kinetic and thermodynamic analyses, providing a feasible environment for SHS. Notably, in situ formation of magnesium nitride (MgSiN 2 ) during the reaction not only acted as an effective sintering aid but also improved the thermal conductivity of the resulting Si 3 N 4 ceramic. The powder produced from a reaction using a raw material composition of 65% Si minimizes both silicon infiltration and melting to the greatest extent, and consequently, the sintered silicon nitride ceramics exhibit the highest thermal conductivity. The low-pressure environment effectively moderated the reaction rate and temperature, promoting the formation of fine α-phase Si 3 N 4 particles with rod-like morphologies. This innovative method offers a cost-effective and environmentally friendly approach for producing high-quality Si 3 N 4 powders with high sintering activity.
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JOURNAL OF MATERIALS SCIENCE
·
2016
·Vol. 52
·期 6
·3535-3544
·
IF 2.302
Gao Xiufeng,Chen Shaoping,Dong Feng,Hu Lifang,Yang Renyao,Wang Wenxian,Munir Zuhair A.
The diffusion bonding between Ti and Ni was investigated in the presence and absence of an imposed electric current. Bonding was carried out over the temperature range of 873–1123 K and the current density range of 255–350 A/cm 2 . The formation and sequence of evolution of the three intermetallic phases, TiNi 3 , TiNi, and Ti 2 Ni, were investigated and discussed in light of calculations of Gibbs free energies of formation and interfacial energies associated with their nucleation. Within the experimental times and in the presence of a current, the growth of the three phases was parabolic. The evolution of the TiNi phase required an incubation period, while the relatively high growth rate of TiNi 3 suggests the possibility of another mechanism. The growth of all phases was enhanced by the application of a direct current, with no apparent dependence on its direction.
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CERAMICS INTERNATIONAL
·
2016
·
IF 2.758
Wei-Ming Guo,Zhi-Lin Zhang,Jing-Xi Li,Yang You,Shang-hua Wu,Hua-Tay Lin
Al 2 O 3 –B 4 C ceramics had poor densification, due to the formation of Al 18 B 4 O 33 phase by reaction between Al 2 O 3 and B 2 O 3 on the surface of B 4 C. In the present work, Y 2 O 3 or Ti additive together with ZrO 2 from milling media were introduced into Al 2 O 3 –B 4 C ceramics. Results showed that Y 2 O 3 reacted with B 2 O 3 to produce YBO 3 phase, and removed Al 18 B 4 O 33 phase, resulting in the improved densification and the coarse microstructure. However, Ti and ZrO 2 reacted with B 2 O 3 to produce hard TiB 2 and ZrB 2 phases, removed the most of Al 18 B 4 O 33 phase, refined microstructure by pinning effect of hard particles, and improved densification and mechanical properties .
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高影响因子
Journal of Materiomics
·
2017
·
IF 0
Haiqiang Liu,Hongan Ma,Taichao Su,Yuewen Zhang,Bing Sun,Binwu Liu,Lingjiao Kong,Baomin Liu,Xiaopeng Jia
We present the work about the initiative fabrication of multi-scale hierarchical TiO 2-x by our strategy, combining high pressure and high temperature (HPHT) reactive sintering with appropriate ratio of coarse Ti to nanosized TiO 2 . Ubiquitous lattice defects engineering has also been achieved in our samples by HPHT. The thermoelectric performance was significantly enhanced, and rather low thermal conductivity (1.60 W m −1 K −1 ) for titanium oxide was reported here for TiO 1.76 . Correspondingly, a high dimensionless figure of merit ( zT ) up to 0.33 at 700 °C was realized in it. As far as we know, this value is an enhancement of 43% of the ever best result about nonstoichiometric TiO 2 and the result is also exciting for oxide thermoelectric materials. The moderate power factor, the significantly reduced thermal conductivity and the remarkable synergy between electrical properties and thermal conductivity are responsible for the excellent thermoelectric performance. We develop a facile strategy for preparing multi-scale hierarchical TiO 2-x and its superior ability to optimize thermoelectric performance has been demonstrated here.
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MATERIALS & DESIGN
·
2016
·
IF 3.997
Jianjun Sha,Jian Li,Shouhao Wang,Zhaofu Zhang,Yongchang Wang,Jixiang Dai
ZrC-based ceramic composites doped with 20 vol.% titanium (Ti) and 3 vol.% carbon nanotubes (CNTs) were prepared by hot pressing. The densification behavior, microstructural evolution and mechanical properties of the composites were studied. The results indicated that the sinterability of the composites was significantly improved, resulting in highly dense matrix (98.27%) at reduced sintering temperature (1600 °C). In addition to the main phase of (Zr, Ti)C, the composites also contained a certain amount of TiC, which was shown to be beneficial for the improvement of mechanical properties. As a result, the flexural strength of the composites was measured to be 415 MPa at room temperature and 647 MPa at 800 °C, respectively. Moreover, the composites showed a high fracture toughness of 5.27 MPa m 1/2 , which increased by 32% compared with the monolithic ZrC (4 MPa m 1/2 ). The improved fracture toughness was attributed to crack deflection, crack bridging and crack branching.
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Nanoscale
·
2016
·Vol. 8
·期 38
·16963-16968
·
IF 7.76
Guoqiang Zhang,Wenshuai Jiang,Shixin Hua,Haifeng Zhao,Ligong Zhang,Zaicheng Sun
Defects (Ti3+ or oxygen vacancies) have been demonstrated to promote the charge separation process in TiO2 based photocatalysts. Particularly, the bulk defects within a certain concentration can give a great enhancement for both light absorption and charge separation efficiency. In this report, we explored a one-step molten salts route to synthesize SrTiO3 nanocubes with bulk defects (Ti3+ doped) by using SrCO3 as a Sr source, and TiO2 and Ti powder as Ti sources. The amount of defects can be tuned by changing the molar ratio of Ti/TiO2. The corresponding bandgap of SrTiO3 can be changed from 3.29 to 2.73 eV with the increase of defects. X-ray diffraction and electron microscopy disclose that SrTiO3 is highly crystalline and has a cubic morphology. X-ray photoelectron spectroscopy and electron paramagnetic resonance indicate that the as-prepared SrTiO3 is close to the Ti3+ doped SrTiO3. Surface photovoltage spectroscopy (SPS) and field-induced SPS confirm that Ti3+ doping in the SrTiO3 turns it from an n-type semiconductor to p-type. The SrTiO3 with an optimal amount of defects exhibits highly enhanced photocatalytic performance. An excess amount of defects results in a weak SPS response and photocatalytic performance.
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高影响因子
ACS Applied Materials & Interfaces
·
2016
·
IF 7.145
Guodong Zou,Zhiwei Zhang,Jianxin Guo,Baozhong Liu,Qingrui Zhang,Carlos Fernandez,Qiuming Peng
A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge–discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g–1 at 1 C (theoretical value being ∼320 mAh·g–1), 260 mAh·g–1 at 10 C, and 150 mAh·g–1 at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1–50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process.
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高影响因子
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