共查询到20条相似文献,搜索用时 15 毫秒
1.
Yan Liu 《Electrochimica acta》2009,54(17):4180-2671
A simple approach to synthesize Co3O4 in mass production by using hexamethylenetetramine (HMT, C6H12N4) as a precipitator via hydrothermal treatment has been developed. The samples were calcinated at different temperatures ranging from 300 to 600 °C and characterized by XRD and SEM. The structure became agglomerative and collapsed with an increase in calcination temperature. Evaluation of the electrochemical performance in combination with SEM and BET analysis suggests that there is an optimum calcination temperature for Co3O4. It is found that the retention capacity of well crystallized Co3O4 hollow microspheres has a higher specific surface area at 300 °C and is almost above 94% after the 5th cycle at different current densities of 40 and 60 mA g−1, which shows good long-life stability and favorable electrochemical behaviors. Using EIS analysis, we demonstrated that lithium-ion conduction inside the SEI layers and charge transfer at the electrode/electrolyte interface became hindered with an increased calcination temperature, which was in good agreement with the electrochemical behaviors of three Co3O4 electrodes. It is proposed that drastic capacity fading and the variation of resistive components (SEI layers and charge transfer) can be influenced by morphologies due to the calcination temperature. 相似文献
2.
《Ceramics International》2022,48(20):29659-29668
A simple strategy for synthesizing porous Co3O4 nanostructures through a hydrothermal process with subsequent thermal decomposition of the obtained Co(CO3)0·35Cl0·20(OH)1.10 precursors was introduced. To understand the growth mechanism of the Co(CO3)0·35Cl0·20(OH)1.10 precursors and realize morphology control of the resultant Co3O4 nanomaterials, a series of controlled experiments were carried out by varying CO(NH2)2 dosages, hydrothermal temperatures and time. The Co3O4 nanorods obtained under optimized synthesis conditions demonstrated porous structural features, which were constructed by well-connected nanograins, leaving many pores composed of the space between nanograins. The ethanol-sensing behaviors of these Co3O4 nanostructures were evaluated, showing the highest response (19.581) and a short response and recovery time (1 s/10 s) to 100 ppm ethanol. Moreover, the Co3O4 sensor demonstrated excellent anti-interference ability toward several interfering gases such as methanol, benzene hexane, and dichloromethane. The stability of the Co3O4 sensor was further confirmed by 14 days of continuous testing. Compared with previously reported works, this Co3O4 sensor still demonstrated outstanding gas sensing properties due to its unique advantages such as 1D porous nanostructures, high BET surface area, abundant oxygen vacancies, and active cobalt sites. 相似文献
3.
4.
Jingtong Xie Congmian Zhen Lu Liu Li Ma Denglu Hou Hanqing Pang Dewei Zhao 《Ceramics International》2021,47(9):11993-12001
A series of FeCo2O4 powders was initially synthesized using a hydrothermal method and subsequently calcined at various temperatures to produce the final product. Pure phase FeCo2O4 powders can only be formed in the temperature range of 950–1050 °C. In this work, we study the cation occupation, cation valence, bond length and bond angle changes of the pure phase FeCo2O4 powders formed in such a narrow temperature range. Octahedral lattice distortion in the pure phase FeCo2O4 samples has been observed. More tetrahedral Fe3+ and octahedral Co2+ are excited and exchanged their sites as the calcination temperature increases from 950 °C to 1000 °C, and part of Co3+ ions are reduced to Co2+ in the sample calcined at 1050 °C. The structure of the sample calcined at 1000 °C is close to that of the ideal FeCo2O4 spinel. Magnetic measurements show that ferrimagnetism and anti-ferromagnetism coexist in the pure phase FeCo2O4 samples. Interaction changes between ferrimagnetism and antiferromagnetism caused by the structural changes of the samples have been studied. Due to the pinning of the local anti-ferromagnetism to ferrimagnetism in the sample, the sample shows a Barkhausen jump below 150 K. As the measurement temperature increases further, the system enters into a reentrant spin glass state. 相似文献
5.
Ritesh Verma Ankush Chauhan Khalid Mujasam Batoo Rajesh Kumar Muhammad Hadhi Emad H. Raslan 《Ceramics International》2021,47(3):3680-3691
Bismuth Ferrite (BiFeO3) is one such materials which has shown very promising multiferroic and excellent optical properties. In this paper, we report effect of annealing temperature on the structural, morphological and optical properties of BiFeO3 nanoparticles synthesised through sol-gel auto-combustion method. Nanoparticles prepared were calcined at three different temperatures, 400 °C, 500 °C and 600 °C, and named as BFO1, BFO2 and BFO3, respectively. X-ray diffraction confirmed the rhombohedral structure with R3c space group as a primary phase. However, a secondary phase Bi2Fe4O9 was also observed which decreases with increasing temperature. The crystallite sizes were found to increase with increasing temperature with BFO2 as anomaly. Field emission scanning electron microscopy (FESEM) shows clear grain formation for all the samples. TEM micrographs and SAED patterns show crystalline grains with rhombohedral structure. All the functional groups observed in the Fourier infrared spectroscopy (FTIR) measurement are indexed. The FTIR spectra shows presence of two prominent vibrational modes in the wave number range 447 and 560 cm-1 corresponding to the stretching of Fe-O bonds. Raman analysis shows presence of a peak at ~527 cm-1 for (BFO3) which was absent in other two samples. Also, the intensity of the A1-1 mode was found stronger than that of A1-2 mode in all the samples which confirmed the stability of the structure, except for BFO1. 相似文献
6.
以共沉淀法制备出的球形Ni0.5Co0.3Mn0.2(OH)2为前驱体,以碳酸锂为锂源,通过高温固相法合成了球形LiNi0.5Co0.3Mn0.2O2正极材料。通过热重分析(TGA/DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)、粒度分布、以及电化学性能的测试考查了不同烧结温度对LiNi0.5Co0.3Mn0.2O2的物理性能及电化学性能的影响。结果表明,900℃下烧结得到的LiNi0.5Co0.3Mn0.2O2晶体结构完整、球形形貌规则、粒度分布均匀,并表现出了优异的电化学性能,0.2 C首次放电容量达到了166.7 mA.h/g;1 C首次放电容量为151.6 mA.h/g,20次循环后,容量保持率高达97.9%。 相似文献
7.
《Ceramics International》2019,45(15):18965-18971
Different calcination atmospheres of air, 50% oxygen (vs. N2) and pure oxygen have been used to prepare special LiNi0.8Co0.1Mn0.1O2 cathode materials to observe the influence of oxygen composition. To investigate the structure and electrochemical property of the samples using different oxygen compositions, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cycling performance tests and electrochemical impedance spectroscopy (EIS) were carried out. XRD, SEM, and XPS results show that the sample made using higher oxygen composition has less cation mixing and lower levels of Ni2+. However, both samples have almost the same oxygen environments on their surfaces as well as micro-morphology and size. The sample with a higher oxygen composition shows better electrochemical performance. Interestingly, the electrochemical performance of the sample made using 50% oxygen is similar to that made with pure oxygen and much better than the sample made with air. It has a specific capacity of 202.4 mAh g−1 at 0.1C and a capacity retention of 85.2% after 300 cycles at 1C, which may be meaningful for balancing cost and performance. 相似文献
8.
《Ceramics International》2022,48(17):24935-24942
Methods of preparation and application of zinc oxide nanoparticles doped with Mn(II) and Co(II) ions are presented and discussed in the paper. Part one shows the results of the solvothermal synthesis of zinc oxide nanoparticles doped with Mn(II) and Co(II) ions. The effect of process parameters on the properties of doped nano zinc oxide has been identified. We also examined the impact of annealing in argon atmosphere of doped zinc oxide nanoparticles on physicochemical properties. Morphology analysis was performed using scanning microscopy and molecular analysis was performed using by inductively coupled plasma - optical emission spectrometry. The zeta potential was measured for samples annealed in argon atmosphere and for samples not annealed. Phase analysis was performed by x-ray diffraction. Based on this analysis, the lattice parameters were determined. 相似文献
9.
《Ceramics International》2020,46(3):2780-2785
In order to improve the performance of the anode of solid oxide fuel cells, the cermet anodes were synthesized by employing a carbonate co-precipitation method and calcined at different temperatures (500 °C-800 °C). The fabrication of pellet from calcined powder was done by uniaxial pressing. These pellets were then characterized to investigate the effect of calcination temperature on their microstructure, thermal behavior, porosity, and carbonate bonding along with conductivity. The carbonates formed within the synthesis process has shown a strong effect over the properties of the Ni-SDC. It is observed that Ni-SDC maintained its chemical compatibility during each process. The thermal gravimetric analysis showed that more weight loss occurred for the specimen calcined at low temperature. Due to the porosity increases with calcination electronic conductivity and performance will also be enhanced. 相似文献
10.
TiO2 hollow nanoparticles were prepared by the solvothermal method, calcined at different temperatures and characterized by XRD, BET, SEM, PL and FT-IR. The effects of morphology, size and calcination temperature on the photocatalytic activity of the prepared materials were discussed in detail. It was found that the calcination temperature altered the crystallinity, morphology, surface area, and the porous structure. The photocatalytic activity of the TiO2 powders evaluated through photocatalytic degradation of gaseous acetone under UV-light irradiation, showed TiO2 calcined at 250 °C to exhibit a higher photocatalytic activity than commercial powders (Degussa P25). 相似文献
11.
《Ceramics International》2017,43(10):7682-7689
Herein, we report a sustainable production of magnetic cobalt ferrite nanoparticles by conventional (CHM) and microwave heating (MHM) method. Hibiscus rosa-sinensis extract was used as both reducing and stabilizing agent. Using plant extracts to synthesize nanoparticles has been considered as an eco-friendly method, since it avoids noxious chemicals. The plethora of plant extract mediated nanoparticles were compared by techniques, such as XRD, Rietveld, FT-IR, SEM, EDX, UV-Visible DRS, PL and VSM were carried out to analyze and understand their crystallite size, functional groups, morphology, optical and magnetic properties. The crystalline structure of cobalt ferrite nanoparticles revealed the cubic structure and the microwave heating of nanoparticles showed smaller crystallite size compared to the conventional heating, which was then confirmed by XRD analysis. To analyze the presence of functional groups and the phytochemical involvement of the plant extract was confirmed by FT-IR studies. Spherical morphology with less than 100 nm sized particles was confirmed by SEM and EDX analysis confirm the existence of Co, O, and Fe elements present in the samples. UV-Visible DRS studies were carried out to calculate the band gap of the as-synthesized nanoparticles, estimated from the Kubelka-Munk function, as 2.06, and 1.87 eV for CHM and MHM, respectively. Photoluminescence emission spectrum of the nanoparticles showed two different bands at 494 and 620 nm, which explores the optical properties of the nanoparticles, due to the quantum confinement effect. VSM analysis showed better ferromagnetic behavior, which can be used for magnetic applications. 相似文献
12.
Amalia Mesaros Cristina D. Ghitulica Mihaela Popa Raluca Mereu Adriana Popa Traian Petrisor Jr. Mihai Gabor Adrian Ionut Cadis Bogdan S. Vasile 《Ceramics International》2014
Zn1−xCoxO (x==0.05, 0.10, 0.15) nanoparticles have been synthesized by an alternative wet-chemical synthesis route using the SimAdd technique. The as-obtained powders were investigated by FT-IR spectroscopy, X-ray diffraction and thermal analysis correlated with evolved gas analysis (TG–DTA–FT-IR) in order to determine their chemical nature, crystalline structure and to establish the decomposition sequences. The precipitates are generally amorphous, but low-intensity reflection peaks assigned both to the zinc oxalate dihydrate, and zinc hydroxide can be observed in the recorded patterns, indicating that hydroxy-oxalate precipitates were obtained. The structure, morphology and magnetic properties of the thermally treated samples have been investigated by X-ray diffraction, FT-IR, HRTEM, SAED, UV–vis and EPR. XRD studies reveal a hexagonal wurtzite-type structure for all Zn1−xCoxO samples. TEM investigations show particle size between 28 and 37 nm, with spherical and polyhedral shapes and with tendency to form aggregates. The presence of a Co3O4 secondary phase was evidenced by XRD, UV–vis and EPR for the Zn0.85Co0.15O sample. The ferromagnetic behavior of the samples was revealed. The paper highlights that by varying the cobalt concentration it is possible to modulate the structural, morphological, optical and magnetic properties. 相似文献
13.
《Ceramics International》2019,45(16):19925-19933
Herein, a low–toxic N, N–dimethylacrylamide (DMAA) system was used in preparation of porous Si3N4 ceramics by aqueous gelcasting, and variations in microstructure and properties with solid loading and calcination temperature were systematically investigated. In the considered solid loading range of 28–44 vol%, all the slurries exhibited superior rheological properties (≤145 mPa⋅s at 95.40 s−1 for 44 vol% solid loading) perfectly suitable for casting. With increasing solid loading, a decreased bulk density (1.71–1.69 g/cm3), volume shrinkage (37.73–13.77%) and flexural strength (46.56–26.75 MPa) of green bodies were obtained, exhibiting better mechanical properties than those derived from the conventional acrylamide (AM) system. Regarding Si3N4 ceramics with various solid loadings, the increase in calcination temperature favored the phase transformation α→β–Si3N4 and β–Si3N4 growth, however, the increased solid loading exhibited an inhibiting effect on those since mass transport in gas phase was blocked due to the disruption of pore connectivity. The resulting microstructure changes imparted Si3N4 ceramics increasing flexural strength (110.36–367.88 MPa), fracture toughness (2.54–5.03 MPa⋅m1/2), as well as decreasing porosity (54.21–41.05%) and pore size (0.38–0.33 μm). This work demonstrates the potential research value of DMAA system in preparing high–performance porous Si3N4 ceramics through gelcasting technique. 相似文献
14.
Øyvind Borg Edd A. Blekkan Sigrid Eri Duncan Akporiaye Bente Vigerust Erling Rytter Anders Holmen 《Topics in Catalysis》2007,45(1-4):39-43
The effect of calcination temperature and atmosphere on the properties of γ-Al2O3 supported cobalt Fischer-Tropsch catalysts has been investigated. One common precursor for all the catalysts was prepared
by incipient wetness impregnation of γ-Al2O3 with an aqueous solution of cobalt nitrate hexahydrate. It was subjected to four different calcination atmospheres (air/50%
steam: 30 mL/min, air: 30 mL/min, air: 50 mL/min, N2: 30 mL/min) and eight different calcination temperatures (range: 473–723 K), making the total number of samples 32. Both
the post calcination nitrogen content and the cobalt dispersion were measured. The results demonstrated that in order to maximise
the cobalt dispersion, it is necessary to use low calcination temperatures and remove the precursor decomposition products
(NO, NO2, H2O) efficiently. The Fischer-Tropsch synthesis performance of two catalysts calcined at the same temperature, but at different
air flow rates was evaluated. No significant effect of the air flow rate was found on the turnover frequency or C5+ selectivity, but a high flow rate resulted in 30% higher activity per gram catalyst. 相似文献
15.
《Ceramics International》2017,43(2):2069-2075
It is very important to develop a new synthetic route for lanthanide metal oxides with novel morphologies and having different fundamental properties and application performances. Here, we report Er2O3 nanorods and nanosheets prepared by a facile hydrothermal method followed by post-thermal annealing treatment. Thermal treatment of Er4O2(OH)8(HNO3) and Er2O5H4 was carried out to form the nanorods and nanosheets, respectively. Their physicochemical properties were evaluated by field-emission scanning electron microscopy, X-ray diffraction crystallography, high-resolution transmission electron microscopy, Fourier transform infrared (IR) spectroscopy, Ultraviolet-visible-near IR absorption spectroscopy, and X-ray photoelectron spectroscopy. The synthesis method and novel fundamental properties provide valuable information for the development of Er complexes and oxides. 相似文献
16.
ZrO2 nanoparticles (NPs) were prepared by a simple, versatile, and an efficient methodology based on microwave. The synthesized NPs were calcined at temperatures ranging from 100 °C to 600 °C. The samples were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), FT-IR spectroscopy, Far-IR spectroscopy, Raman spectroscopy, and UV-vis absorption spectroscopy. The results clearly showed the presence of purely monoclinic phase of zirconia when the calcination temperature exceeds 400 °C. The experimental results showed that the viscosity of zirconia NPs in ethylene glycol (EG) increases with increasing the particle volume fraction and decreases with increasing temperature. 相似文献
17.
18.
《Journal of Industrial and Engineering Chemistry》2014,20(3):818-823
In this investigation, the normal nano-crystalline cobalt-aluminate spinel has been successfully synthesized by the combustion technique. In order to study the colorant behavior of powders after heat treatment, quantitative and qualitative experiments such as color spectroscopy, X-ray and Raman spectroscopy were applied. Transmission electron microscopy technique was used to estimate the particle size and observe the morphology of pigments. The green powder was identified as an inverse spinel structure whereas a normal spinel corresponding to blue color was produced at higher temperatures. For obtaining powder with the high colorant efficiency, it is better to carry out calcination at 1000 °C. 相似文献
19.
AbstractThe calcination temperature (Cal-Temp) plays a vital role in the performance of supported metal catalysts. In this work, the alumina supported Ni, NiMo, Co, and CoMo catalysts were prepared at different Cal-Temp. The catalysts were characterized by various techniques to identify the catalytically active different surface species to correlate their role in the hydrodeoxygenation of stearic acid. With increasing Cal-Temp, the metal dispersion was increased for Ni, NiMo, and CoMo catalyst (up to 973 K) and decreased for Co catalyst. With increasing Cal-Temp, the catalytic activity was thus increased for Ni and NiMo catalyst and decreased for Co catalyst. The activity of CoMo catalyst was, however, enhanced with rising Cal-Temp up to 973 K and declined slightly after that. The optimum Cal-Temp for Ni, NiMo, Co, and CoMo catalyst was found to be 1023 K, 973 K, 773 K, and 973 K. The reaction followed the decarbonylation route over active metallic centers (Ni and Co) and the HDO route over oxophilic M2+?MoO2 (M = Ni/Co) and reducible cobalt oxide species. The C17 alkane was thus the principal product over Ni catalyst, whereas C18 alkane was the primary product over CoMo and NiMo catalyst. In contrast, both C17 and C18 alkanes were significant over Co catalyst. 相似文献
20.
Mohd Hizami Mohd Yusoff 《Chemical Engineering Communications》2018,205(4):506-518
Sulfated zirconia on SBA-15 catalysts with different calcination temperatures (450, 550, 600 and 650°C) were synthesized through urea hydrolysis method. The catalysts were characterized using N2 adsorption–desorption analysis, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, thermogravimetric analysis, temperature-programmed desorption of ammonia (NH3–TPD), X-ray diffraction, and determination of surface acidity by HCl titration method. The catalyst’s characteristics and their correlation with the catalytic activity in the esterification of palmitic acid with glycerol were particularly investigated. The characterization results revealed that the morphology of all catalysts remained virtually unaffected with increasing calcination temperature but the surface area and pore volume of the catalysts showed some reduction. Pore diameter was not significantly affected by the calcination temperature which indicated the stability of the porous catalysts. Furthermore, the increase in the calcination temperature exceeding 600°C would reduce the catalytic activity toward monopalmitin due to a decrease in the active acid sites concentration and acidic strength of the catalyst as a result of sulfur decomposition. 相似文献