p型透明导电氧化物CuCr1–xMgxO2的制备及光电性能研究

采用溶胶–凝胶法制备了CuCr1–xMgxO2粉末,压制烧结形成了CuCr1–xMgxO2陶瓷样品,研究了Mg2+掺杂量和压制压强对CuCrO2粉末和陶瓷的相组成、显微结构及光电性能的影响。结果表明:随着Mg2+掺杂量从0.01增加到0.07,所制CuCr1–xMgxO2粉末对紫外–可见光的吸收度增加,光学带隙宽度由3.25 eV逐渐减小到2.86 eV。随着Mg2+掺杂量或压制压强的增加,其相应陶瓷样品的电导率均先增大后减小。当Mg掺杂量x为0.03,压制压强为550 MPa时,制备的CuCr0.97Mg0.03O2陶瓷样品的电导率达到最大值,为19.8 S/cm。     

Dy~(3+)掺杂LiZnMg铁氧体的制备及其电磁性能研究

采用sol-gel燃烧法制备了稀土Dy3+掺杂的LiZnMg铁氧体[Li0.1Zn0.8Mg0.06(Fe2.04–xDyx)O4]。借助XRD、SEM和Agilent 8722ET网络分析仪等表征手段,研究了Dy3+掺杂量对其显微结构及电磁性能的影响。结果表明,当Dy3+掺杂量x为0.01时,其晶格常数a由未掺杂时的0.84478nm增加到0.84494nm;μ'和tanδ峰值分别由未掺杂时的0.307和0.53增加到0.330和0.61。     

钴掺杂多孔锰氧化物自组装花球制备及其超电容特性研究

通过水热法制备了掺杂不同含量钴离子的多孔结构MnO_2纳米花球,研究了锰氧化物掺杂前后的实际放电比容量,从而比较钴离子含量对其电化学性能的影响。对不同样本做了结构、形貌及电化学性能方面的测试。通过XRD谱说明钴离子均一地掺杂到了锰氧化物的中间。通过SEM照片可以看到产品的微观形貌均是由纳米片层状结构组装成的纳米花球。在未掺杂钴时,纳米花球的颗粒大小不均一,而掺杂摩尔分数10%的钴离子后,大大降低了自组装结构的尺寸,并且使得材料的微观表面更加疏松,这种减小的尺寸使得电解液的进入更加容易,从而使得材料的利用率大大增加。通过恒电流充放电测试显示,当钴掺杂量为摩尔分数10%时,锰氧化物比容量最大可达410.158 F·g~(–1)。     

掺杂Li_2CO_3低温烧结ZnO-TiO_2系介质陶瓷的研究

用传统工艺合成了Li2CO3掺杂的ZnO-TiO2系微波介质陶瓷,系统研究了其烧结行为、显微结构和介电性能。结果表明:掺杂质量分数1%的Li2CO3可使ZnO-TiO2陶瓷的烧结温度从1100℃降到980℃;掺杂3%Li2CO3时,在950℃保温2h烧结,于6～8GHz测试试样的介电性能为:εr约为20,Q·f约为40000GHz,τf约为–14×10–6℃–1。     

Co、Mn的掺杂形式对低压氧化锌压敏陶瓷电性能的影响

研究了Co、Mn的不同掺杂形式对低压ZnO压敏电阻显微结构和电性能的影响。发现以Co(NO3 ) 2 、Mn (NO3 ) 2 溶液代替CoO、MnO2 掺杂 ,可以降低压敏电压 ,增大非线性系数。这主要与钴的高价态有关 ,利于压敏电阻的低压化。     

稀土掺杂钴铁氧体的制备与性能研究

本文采用钴铁氧体最常用的溶胶法在添加稀土化合物的情况下制备稀土掺杂钴铁氧体。通过对制备的样品进行性能研究得如下结论:到稀土掺杂是改善钴铁氧体的有效手段,其生成的产物各项性能都有所改善,为钴铁氧体这中材料应用提供了更广阔的思路     

铜掺杂量对钴酸钙热电性能的影响研究

采用sol-gel法制备了掺Cu的钴酸钙(Ca3Co4O9)热电材料,研究了Cu掺杂量对其物相、电导率σ、Seebeck系数S和功率因子P的影响。结果表明:随着Cu掺杂量的增加,试样中Ca3Co4O9的含量下降,但试样的电导率增加;试样的Seebeck系数和功率因子先增加后下降。试样(Ca0.90Cu0.10)3Co4O9在973 K时的功率因子最大,为15.3×10–4 W.m–1.K–2。     

20号钢表面激光熔覆层的电子显微分析

用DX-3型扫描电镜和JEOL-733型电子探针对20号钢表面钴基激光熔覆层的显微结构和掺杂元素的分布作了观察与分析。结果指出,表面形成了良好的冶金结合,涂料元素基本上不进入基材。     

Cu掺杂对CoFe_2O_4结构与磁性能的影响

为了系统地研究Cu掺杂对于CoFe_2O_4结构与磁性能的影响及其影响机制,采用柠檬酸-溶胶凝胶法制备了Co_(1–x)Cu_xFe_2O_4(x=0,0.2,0.4,0.6,0.8,1)磁性纳米颗粒。分别用X射线衍射仪,透射电子显微镜,振动样品磁强计对样品的晶体结构、形貌、磁学性质进行了表征和测试。结果发现所制备的钴铜铁氧体的纳米颗粒直径在50~60 nm,适量的Cu~(2+)掺杂,铜钴铁氧体依然保持面心立方结构,且可以有效降低其饱和磁感应强度和居里温度。但是掺杂量达到x=0.8后,会引起Jahn Teller效应,铜钴铁氧体发生晶格畸变,由面心立方相转变为面心四方相,饱和磁感应强度、居里温度随之增加。     

CuO掺杂BFS基厚膜热敏电阻的研制

以固相法制备的BaFe1–xSnxO3(BFS)材料为功能相、BaBiO3为粘结相、CuO为掺杂剂,制备了新型BFS基厚膜热敏电阻浆料,并用此浆料制备了BFS基厚膜热敏电阻。借助SEM和ρ-t特性测试仪,研究了CuO掺杂量对所制电阻显微结构及电性能的影响。结果表明:随着CuO掺杂量的增加,BFS基厚膜热敏电阻的方阻逐渐降低,其B25/85值则先缓慢上升,接着迅速降低,而后又逐渐增加。当CuO质量分数为14%时,所得电阻样品性能较好且具有明显的NTC特性,其方阻、B25/85值及电阻温度系数αR分别为:2.8×105?·□–1,3285K和3.69×10–2℃–1。     

CoMo2S4 with Superior Conductivity for Electrocatalytic Hydrogen Evolution: Elucidating the Key Role of Co

CoMo₂S₄ 2D nanosheets are constructed by a hard template-limited domain strategy, meanwhile the hydrogen evolution reaction (HER) properties and the function of Co in CoMo₂S₄ are systematically investigated. Electrochemical tests show that CoMo₂S₄ possesses high HER performance with an overpotential of 55 and 150 mV at 10 and 100 mA cm⁻², respectively, outperforming Pt/C (20%) and the state of art Mo–S, Co–S, and Co–Mo–S-based materials. An in-depth mechanism study reveals that the main active site of CoMo₂S₄ is Mo rather than Co, whereas Co plays a key role in improving the electrical conductivity of the catalyst and thus improving the HER performance. X-ray photoelectron spectroscopy and density of state tests demonstrate that the introduction of Co leads to electron delocalization in the catalyst, making the electrons transport easier and finally endowing the catalyst with better conductive performance. It is believed this is the first time that the effect of Co on improving the bulk conductivity of Co–Mo–S catalyst is proposed, which highlights the potency of Co in improving the electrocatalytic HER activity of Mo–S-based materials.     

固相反应法制备NiO-Co_3O_4复合物及其超级电容器性能

采用固相反应法合成了摩尔比为4∶1的NiO-Co3O4复合物,用XRD和SEM表征了样品的相结构和形貌,采用循环伏安(CV)法和恒流充放电测试两种方法研究了纯NiO、纯Co3O4和NiO-Co3O4复合物电极的电化学性能。结果表明:所得复合物样品为立方相结构,Co3O4的掺入增加了NiO样品的孔穴率。在6mol.L–1的KOH电解液中,复合物的比电容达到了476F.g–1,远高于纯NiO(约93F.g–1)和纯Co3O4的比电容(约148F.g–1)。在充放电1000次后,NiO-Co3O4的比容量仅衰减了3.4%,显示出该复合物的电化学性能明显优于纯NiO和纯Co3O4。     

Al含量对Ho-Co合金吸波性能的影响

通过高温电弧合金熔炼技术制备了Ho2Co17–xAlx(x=0,0.4,0.8,1.2,1.6)合金微粉,采用XRD和SEM分析了所制合金微粉的组成相和微结构,使用网络矢量分析仪研究了其吸波性能。结果表明:其所制样品均由Ho2Co17相组成;在吸波涂层厚度d=1.5 mm时,随x的增大,Ho2Co17–xAlx合金微粉的反射率最小值从–11.4 dB(x=0)降低到–49.8 dB(x=1.6)。同时,Al的添加会使Ho2Co17的吸收峰向高频移动,吸收峰频率从7.28 GHz(x=0)升高到14.32 GHz(x=1.6)。     

Co_2O_3掺杂对0.965MgTiO_3-0.035SrTiO_3微波介质陶瓷性能的影响

采用传统电子陶瓷制备方法研究了Co2O3(1.5%～5.0%,质量分数)掺杂的0.965MgTiO3-0.035SrTiO3(MST0.035)微波介质陶瓷,分析了Co2O3含量对MST0.035陶瓷的烧结性能、晶相结构、显微形貌以及微波介电性能的影响。结果表明:Co2O3的掺杂促进了MST0.035陶瓷的烧结。随着Co2O3掺杂量的增加,陶瓷介电常数略有下降,谐振频率温度系数以及品质因数增加,同时中间相MgTi2O5逐渐减少直至完全消失。当Co2O3掺杂量为质量分数3.0%时,MST0.035陶瓷的烧结温度由1 380℃降低到1 290℃,其烧结所得的样品具有优良的微波介电性能:谐振频率温度系数τf=–2.53×10–6/℃,高的品质因数Q·f=19 006 GHz和介电常数εr=20.5。     

Cobalt–titanium multilayer thin films: Effect of thickness of titanium spacer layer on impedance properties

We investigated the impedance parameters of cobalt–titanium (Co–Ti) multilayer thin films deposited on native oxidized Si (100) substrate under ultra-high vacuum (4×10⁻⁸ mbar) by magnetron sputtering at room temperature. Electrical properties of Co/Ti/Co multilayer films were analyzed depending on the thickness of Ti spacer layer with the impedance spectroscopy as a function of frequency. Co/Ti multilayer films exhibited dielectric relaxation in both real and imaginary part of dielectric constants at the kilohertz frequency region and piezoelectric properties at the megahertz frequency region. We determined that the fabricated multilayer films have complex and super imposed type behavior when DC conductivity is used at lower frequency, resonance event and relaxation properties.     

Optical properties of undoped and cobalt doped ZnS nanophosphor

In the present study, the optical properties of ZnS and cobalt (Co) doped ZnS nanoparticles were investigated at room temperature. ZnS and ZnS:Co nanophosphors were prepared through chemical route, namely the chemical precipitation method and the formation of the nanoparticles were confirmed by X-ray diffraction and field emission scanning electron microscope (FESEM). Band gap energy of the prepared samples is determined by using a UV–vis–NIR spectrophotometer. The photoluminescence property of ZnS and ZnS:Co sample is determined by fluorescence spectroscopy. The sizes of as prepared nanoparticles are found to be in the 8–9 nm range. The FESEM morphology shows the formation of nanostructure of ZnS samples. The value of optical band gap has been found to be in the range 4.30–4.03 eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, Co²⁺ doped ZnS samples show enhanced visible light emissions under the same UV excitation wavelength of 310 nm.     

Use of thin film of a Co<Subscript>15</Subscript>Ti<Subscript>40</Subscript>N<Subscript>35</Subscript> alloy for CVD catalytic growth of carbon nanotubes

It is shown that multiwalled carbon nanotubes can be grown on the catalytic surface of a Co–Ti–N alloy with low (~10 at %) cobalt content by the conventional method of chemical deposition from acetylene. Adding nitrogen to the composition of the Co–Ti contributes the formation of the TiN compound and extrusion of Co onto the surface where it makes a catalytic effect for CNT growth. It was found that the tubes begin growth at a temperature of 400°C. It is shown by studies using Raman spectroscopy that the quality of CNT improves with increasing temperature.     

2D Dual‐Metal Zeolitic‐Imidazolate‐Framework‐(ZIF)‐Derived Bifunctional Air Electrodes with Ultrahigh Electrochemical Properties for Rechargeable Zinc–Air Batteries

Here first a 2D dual‐metal (Co/Zn) and leaf‐like zeolitic imidazolate framework (ZIF‐L)‐pyrolysis approach is reported for the low‐cost and facile preparation of Co nanoparticles encapsulated into nitrogen‐doped carbon nanotubes (Co‐N‐CNTs). Importantly, the reasonable Co/Zn molar ratio in the ZIF‐L is the key to the emergence of the encapsulated microstructure. Specifically, high‐dispersed cobalt nanoparticles are fully encapsulated in the tips of N‐CNTs, leading to the full formation of highly active Co–N–C moieties for oxygen reduction and evolution reactions (ORR and OER). As a result, the obtained Co‐N‐CNTs present superior electrocatalytic activity and stability toward ORR and OER over the commercial Pt/C and IrO₂ as well as most reported metal‐organic‐framework‐derived catalysts, respectively. Remarkably, as bifunctional air electrodes of the Zn–air battery, it also shows extraordinary charge–discharge performance. The present concept will provide a guideline for screening novel 2D metal‐organic frameworks as precursors to synthesize advanced multifunctional nanomaterials for cross‐cutting applications.     

Understanding the Diffusion-Dominated Properties of MOF-Derived Ni–Co–Se/C on CuO Scaffold Electrode using Experimental and First Principle Study

Batteries and supercapacitors continue to be one of the most researched topics in the class of energy storage devices. The continuous development of battery and supercapacitor cell components has shown promising development throughout the years—from slabs of pure metal to porous and tailored structures of metal-based active materials. In this direction, metal–organic frameworks (MOFs) serve great advantages in improving the properties and structure of the derived metal-based active materials. This research provides a novel electrode material, Ni–Co–Se/C@CuO, derived from Ni–Co-MOF integrated with pre-oxidized Cu mesh. The superior electrochemical performance of Ni–Co–Se/C@CuO over Ni–Co-MOF@CuO is evident through its higher specific capacity, lower resistivity, richer redox activity, and more favorable diffusion-dominated storage mechanism. When assembled as a hybrid supercapacitor (HSC), the hybrid device using rGO and Ni–Co–Se/C@CuO as electrodes exhibits a high energy density of 42 W h kg⁻¹ at a power density of 2 kW kg⁻¹, and maintains its capacity retention even after 20 000 cycles. The improved capacity performance is also evaluated using first-principle investigations, revealing that the unique and preserved heterostructure of Ni–Co–Se/C@CuO portrays enhanced metallic properties. Such evaluation of novel electrodes with superior properties may benefit next-generation electrodes for supercapacitor devices.     

Self-Standing Nanofiber Electrodes with Pt–Co Derived from Electrospun Zeolitic Imidazolate Framework for High Temperature PEM Fuel Cells

Expedited conversion of O₂ to H₂O with minimal amounts of Pt is essential for wide applicability of PEM fuel cells (PEMFCs). Therefore, it is imperative to develop a process for catalyst management to circumvent unnecessary catalyst loss while improving the Pt utilization, catalytic activity, and durability. Here, the fabrication of a self-standing nanofiber electrode is demonstrated by employing electrospinning. This film-type catalyst simultaneously contains Pt–Co alloy nanoparticles and Co embedded in an N-doped graphitized carbon (Co–N_x) support derived from the electrospun zeolitic imidazolate frameworks. Notably, the flexible electrode is directly transferrable for the membrane-electrode assembly of high temperature PEMFC. In addition, the electrodes exhibit excellent performance, maybe owing to the synergistic interaction between the Pt–Co and Co–N_x as revealed by the computational modeling study. This method simplifies the fabrication and operation of cell device with negligible Pt loss, compared to ink-based conventional catalyst coating methods.