Zn-Sn共掺杂Mg_(2)TiO_(4)微波介电陶瓷的制备与表征

本研究分别用微量Zn^(2+)与Sn^(4+)取代Mg_(2)+与Ti^(4+),通过固相反应法制备了Zn-Sn共掺杂Mg_(2)TiO_(4)微波介电陶瓷,并采用阿基米德法、XRD、SEM、EDS及网络分析仪等手段,分析了材料的基本物性和介电特性。基本物性分析结果表明,烧结温度、Zn掺杂量x、Sn掺杂量y等因素对Mg_(2)TiO_(4)的晶体结构无明显影响,烧结致密性随烧结温度的升高呈先增大后减小的趋势,其中在1300℃下烧结所得的(Zn_(0.05)Mg_(0.95))2(Sn_(0.05)Ti_(0.95))O_(4),烧结致密性最佳,达到98%。微波介电特性分析结果表明,Zn-Sn共掺杂Mg_(2)TiO_(4)的介电常数εr与品质因数Q×f值,均随烧结温度的升高而呈先增大后减小的趋势,且其谐振频率温度系数τf具有较好的稳定性,其中在1300℃下烧结所得的(Zn_(0.05)Mg_(0.95))2(Sn_(0.05)Ti_(0.95))O4,εr≈15.55,Q×f≈319690GHz,此时τf≈-52.06×10^(-6)·℃^(-1)。与前人的研究结果比较后可知,本研究制备的(Zn_(0.05)Mg_(0.95))2(Sn_(0.05)Ti_(0.95))O_(4)不仅将烧结温度大幅下降至1300℃,还能将品质因子提升至319690GHz,使其微波介电性能得到有效改善。

Realizing Cd and Ag codoping in p-type Mg_(3)Sb_(2)toward high thermoelectric performance

Mg_(3)Sb_(2)has attracted intensive attention as a typical Zintl-type thermoelectric material.Despite the exceptional thermoelectric performance in n-type Mg_(3)Sb_(2),the dimensionless figure of merit(zT)of p-type Mg_(3)Sb_(2)remains lower than 1,which is mainly attributed to its inferior electrical properties.Herein,we synergistically optimize the thermoelectric properties of p-type Mg_(3)Sb_(2)materials via codoping of Cd and Ag,which were synthesized by high-energy ball milling combined with hot pressing.It is found that Cd doping not only increases the carrier mobility of p-type Mg_(3)Sb_(2),but also diminishes its thermal conductivity(κ_(tot)),with Mg_(2.85)Cd_(0.5)Sb_(2)achieving a lowκtot value of∼0.67 W m^(−1)K^(−1)at room temperature.Further Ag doping elevates the carrier concentration,so that the power factor is optimized over the entire temperature range.Eventually,a peak zT of∼0.75 at 773 K and an excellent average zT of∼0.41 over 300−773 K are obtained in Mg_(2.82)Ag_(0.03)Cd_(0.5)Sb_(2),which are∼240%and∼490%higher than those of pristine Mg_(3.4)Sb_(2),respectively.This study provides an effective pathway to synergistically improve the thermoelectric performance of p-type Mg_(3)Sb_(2)by codoping Cd and Ag,which is beneficial to the future applications of Mg_(3)Sb_(2)-based thermoelectric materials.

Band gap narrowing of TiO_2 by compensated codoping for enhanced photocatalytic activity

In this study, we have performed first-principles screened exchanged hybrid density function theory with the HSE06 function calculations of the C-Mo, C-W, N-Nb and N-Ta codoped anatase TiO2 systems to investigate the effect of codoping on the electronic structure of TiO2. The calculated results demonstrate that （W（s）＋C（s）） codoped TiO2 narrows the band gap significantly, and have little influence on the position of conduction band edges, therefore, enhances the efficiency of the photocatalytic hydrogen generation from water and the photodegradation of organic pollutants. Moreover, the proper oxygen pressure and temperature are two key factors during synthesis which should be carefully under control so that the desired （W（s）＋C（s）） codoped TiO2 can be obtained.

Revisiting the Electron-Doped SmFeAsO:Enhanced Superconductivity up to 58.6 K by Th and F Codoping

In the iron-based high-To bulk superconductors, Tc above 50 K was only observed in the electron-doped 1111-type compounds. Here we revisit the electron-doped SmFeAsO polycrystals to make a further investigation for the highest Tc in these materials. To introduce more electron carriers and less crystal lattice distortions, we study the Th and F eodoping effects into the Sm-O layers with heavy electron doping. Dozens of Sm1-xThx FeAsO1-yFy samples are synthesized through the solid state reaction method, and these samples are carefully characterized by the structural, resistive, and magnetic measurements. We find that the codoping of Th and F clearly enhances the superconducting Tc more than the Th or F single-doped samples, with the highest record Tc up to 58.6K when x = 0.2 and y=0.225. Further element doping causes more impurities and lattice distortions in the samples with a weakened superconductivity.

Upconversion Luminescence Properties of NaY0.92Yb0.05Er0.03F4 Enhanced by Zr^4＋ Codoping

In this paper we present a novel report on the upconversion luminescence performance of NaY0.92Yb0.05Er0.03F4 enhanced by Zr^4＋ codoping. The luminescence intensity of the tridoped hexagonal NaYF_4 synthesized by a hydrothermal method increased to the maximum, about seven times of the non-Zr^4＋ sample when the Zr^4＋ codoping concentration rose to 6 mol%, while the luminescence lifetime was also prolonged by Zr^4＋ codoping. To explore the relationships between the microstructure and upconversion properties, X-ray powder diffraction, field emission scanning electron microscope, electron energy-dispersive spectroscopy and upconversion emission spectroscopy were employed. From these characterizations, we found that the codoping of Zr^4＋ could modulate the crystal microstructure of NaYF_4 for higher upconversion luminescence intensity and longer lifetime. This study may be helpful for the design and synthesis of high-performance upconversion materials.

Waste to wealth: Oxygen-nitrogen-sulfur codoped lignin-derived carbon microspheres from hazardous black liquors for high-performance DSSCs

Carbon materials are effective substitutes for Pt counter electrodes(CEs) in dye-sensitized solar cells(DSSCs). However, many of these materials, such as carbon nanotubes and graphene, are expensive and require complex preparation process. Herein, waste lignin, recycled from hazardous black liquors,is used to create oxygen-nitrogen-sulfur codoped carbon microspheres for use in DSSC CEs through the facile process of low-temperature preoxidation and high-temperature self-activation. The large number of ester bonds formed by preoxidation increase the degree of cross-linking of the lignin chains, leading to the formation of highly disordered carbon with ample defect sites during pyrolysis. The presence of organic O/N/S components in the waste lignin results in high O/N/S doping of the pyrolysed carbon,which increases the electrolyte ion adsorption and accelerates the electron transfer at the CE/electrolyte interface, as confirmed by density functional theory(DFT) calculations. The presence of inorganic impurities enables the construction of a hierarchical micropore-rich carbon structure through the etching effect during self-activation, which can provide abundant catalytically active sites for the reversible adsorption/desorption of electrolyte ions. Under these synergistic effects, the DSSCs that use this novel carbon CE achieve a quite high power-conversion efficiency of 9.22%. To the best of our knowledge, the value is a new record reported so far for biomass-carbon-based DSSCs.

Effect of the codoping of N-H-O on the growth characteristics and defects of diamonds under high temperature and high pressure

Diamond crystals were synthesized with different doping proportions of N-H-O at 5.5 GPa-7.1 GPa and 1370℃-1450℃. With the increase in the N-H-O doping ratio, the crystal growth rate decreased, the temperature and pressure conditions required for diamond nucleation became increasingly stringent, and the diamond crystallization process was affected. [111] became the dominant plane of diamonds;surface morphology became block-like;and growth texture,stacking faults, and etch pits increased. The diamond crystals had a two-dimensional growth habit. Increasing the doping concentration also increased the amount of N that entered the diamond crystals as confirmed via Fourier transform infrared spectroscopy. However, crystal quality gradually deteriorated as verified by the red-shifting of Raman peak positions and the widening of the Raman full width at half maximum. With the increase in the doping ratio, the photoluminescence property of the diamond crystals also drastically changed. The intensity of the N vacancy center of the diamond crystals changed, and several Ni-related defect centers, such as the NE1 and NE3 centers, appeared. Diamond synthesis in N-H-O-bearing fluid provides important information for deepening our understanding of the growth characteristics of diamonds in complex systems and the formation mechanism of natural diamonds, which are almost always N-rich and full of various defect centers. Meanwhile, this study proved that the type of defect centers in diamond crystals could be regulated by controlling the N-H-O impurity contents of the synthesis system.

Phase transformation and morphology tuning of β-NaYF_4:Yb^(3+),Er^(3+) nanocrystals through K^+ ions codoping

In this work, a simple method to modulate the crystal phase and morphology with a large amount of K＋ions codoping is proposed. The phase changes to the mixture of β-Na YF4 and β-KYF4 with increasing the content of K^＋ions to 80 mol%.When it exceeds 80 mol%, β-Na YF4 disappears gradually and β-KYF4 dominates with a poor crystalline. In addition, the morphology changes from nanosphere to nanoplate, and then to nanoprism, which indicates that a higher content of K^＋ions favors the growth rates along [0001] than the [10-10] of the nanocrystals. Additionally, the upconversion（UC） luminescence properties and the ratio of red/green（R/G） UC intensity of samples with different phases and morphologies are detected,which makes it possible to tune the UC fluorescence by varying the concentration of K^＋ions.

N/S codoping modification based on the metal organic frameworkderived carbon to improve the electrochemical performance of different energy storage devices

Carbon-based materials have become a research hotspot in the field of energy storage devices in recent years due to their abundant resources,low cost,and environmental friendliness.However,the low capacity and poor high rate performance still constitute great challenges.Metal organic framework-derived carbon has been widely researched because of its high porosity,tunable structure,and good conductivity.In this work,N/S codoped hierarchical porous carbon microspheres were prepared by a high-temperature heat treatment and atomic doping process using a zinc-based organic framework as the precursor.When used as a potassium-ion battery anode,it has a high reversible specific capacity(435.7 mAh g^(-1)),good rate performance(133.5 mAh g^(-1)at 10,000 m A g^(-1)),and long-term cycling stability(73.2%capacity retention after the 2500th cycle).The potassium storage mechanism of the derived carbon was explained by various electrochemical analysis methods and microstructure characterization techniques,and the relationship between the structural characteristics and electrochemical properties was researched.In a supercapacitor,the porous carbon material exhibits a specific capacitance of 307.2 F g^(-1)at a current density of 0.2 A g^(-1)in a KOH aqueous solution and achieves a retention rate of 99.88%after 10,000 cycles.The assembled symmetric supercapacitor device delivers a high energy density of 6.69 Wh kg^(-1),with a corresponding power density of 2500 W kg^(-1).In addition,density functional theory calculations further confirmed that N/S codoping can improve the adsorption capacities of potassium and hydroxyl ions in the derived carbon.

Zn-Sn复合氧化物的制备及其电化学性能

采用液相沉淀法制备ZnSn（OH）6前驱体。在不同温度下热处理前驱体，得到Zn-Sn复合氧化物。通过差热／热重分析（TG／DTA）、XRD分析前驱体和Zn-Sn复合氧化物的结构，运用恒流充放电研究了Zn-Sn复合氧化物作为锂离子电池负极材料的电化学性能。结果表明：在300℃和500℃下热处理前驱体得到的是非晶态的ZnSnO3，在670℃、720℃和800℃下热处理得到的是晶态的ZnSnO3和尖晶石型Zn2SnO4。若从容量和循环寿命综合考虑，在发生相变的温度范围（670～720℃）内热分解，得到的产物的电化学性能较差。

机械镀Zn-Sn合金镀层锡还原沉积法工艺研究

为丰富和发展机械镀合金化镀层沉积方法及制备工艺,在机械镀Zn-Sn合金镀层工艺过程中,采用还原沉积活化剂替代金属锡粉,在复合的活化液作用下,锌粉以吸附沉积为主,锡的添加以还原沉积为主的镀层形成环境,可以在钢铁制品表面上形成机械镀Zn-25%Sn合金镀层.镀层性能测试结果表明:由于不使用金属锡粉作为原料,镀层中无粗大锡粉颗粒;在同样的运动和冲击条件下,还原沉积工艺方法使得机械镀Zn-25%Sn合金镀层的形成过程向着致密化和平整化的方向改变,得到的镀层平整、光亮、均匀性好,同时也有利于提高有色金属的使用率,降低生产成本.

电沉积Zn-Sn合金工艺的研究

在电解铜箔上采用碱性焦磷酸盐体系电镀Zn-Sn合金,可改善铜箔表面的综合性能。研究了配位剂、pH值、温度、电流密度等对镀层质量的影响,选择了合适的添加剂,并对其极化行为进行了研究,优化确定了电镀Zn-Sn合金的镀液组成和工艺条件。经过处理后的电解铜箔耐蚀性、耐热性和粘合强度等性能均有明显提高。

碳布支撑Sn^(2+)/Sn^(4+)共掺杂的ZnIn_(2)S_(4)柔性光催化剂用于高效降解盐酸四环素

本文采用一步溶剂热法制备了Sn^(2+)/Sn^(4+)共掺杂的ZnIn_(2)S_(4)/碳布柔性光催化剂(CC/ZIS-Sn),二维片状ZIS-Sn均匀地排列在碳布表面。通过降解盐酸四环素(TCH)溶液来评价所制备样品的光催化活性。结果表明,CC/ZIS-Sn_(0.09)复合光催化剂具有高效的光催化活性,40 min对TCH溶液(50 mL,20 mg/L)的降解率高达93.3%。适量的Sn掺杂和碳布协同作用能够调整电子结构,缩小光捕获带隙,增强ZIS光生载流子的分离和转移效率。自由基捕获实验证明空穴是光催化降解过程中的主要活性物质。此外,CC/ZIS-Sn光催化剂还具有良好的可回收性和稳定性,循环测试4次后,对TCH溶液的去除率仍达83.1%。

Cu对Zn-Sn合金微观组织和力学性能的影响

研究了添加少量Cu元素对Zn-35%Sn流行饰品合金微观组织和力学性能的影响。结果表明,在Zn-35%Sn合金中加入0～3.0%Cu,金相组织中的ε相会明显增加;合金伸长率从11.2%下降为9.8%左右,然后再上升到12.6%;抗拉强度从100 MPa上升为150 MPa,又下降到120 MPa。断口分析表明,含Cu量较低时,断口处存在疏松缺陷,随着Cu含量的增加,缺陷逐渐消失;Cu元素的添加,可以细化Zn合金的晶粒,但对合金伸长率的影响不大。Zn-Sn合金中Cu的适宜添加量为1.5%～2.5%。

Heteroatom tuning in agarose derived carbon aerogel for enhanced potassium ion multiple energy storage

The incorporation of heteroatoms into carbon aerogels(CAs)can lead to structural distortions and changes in active sites due to their smaller size and electronegativity compared to pure carbon.However,the evolution of the electronic structure from single-atom doping to heteroatom codoping in CAs has not yet been thoroughly investigated,and the impact of codoping on potassium ion(K+)storage and diffusion pathways as electrode material remains unclear.In this study,experimental and theoretical simulations were conducted to demonstrate that heteroatom codoping,composed of multiple heteroatoms(O/N/B)with different properties,has the potential to improve the electrical properties and stability of CAs compared to single-atom doping.Electronic states near the Fermi level have revealed that doping with O/N/B generates a greater number of active centers on adjacent carbon atoms than doping with O and O/N atoms.As a result of synergy with enhanced wetting ability(contact angle of 9.26°)derived from amino groups and hierarchical porous structure,ON-CA has the most optimized adsorption capacity(−1.62 eV)and diffusion barrier(0.12 eV)of K^(+).The optimal pathway of K^(+)in ON-CA is along the carbon ring with N or O doping.As K^(+)storage material for supercapacitors and ion batteries,it shows an outstanding specific capacity and capacitance,electrochemical stability,and rate performance.Especially,the assembled symmetrical K^(+)supercapacitor demonstrates an energy density of 51.8 Wh kg^(−1),an ultrahigh power density of 443Wkg^(−1),and outstanding cycling stability(maintaining 83.3%after 10,000 cycles in 1M KPF6 organic electrolyte).This research provides valuable insights into the design of highperformance potassium ion storage materials.

钨镍共掺杂V_(2)O_(5)薄膜的光电特性研究

利用溶胶–凝胶旋涂法和后退火工艺在FTO导电玻璃上制备了钨镍共掺杂V_(2)O_(5)薄膜,研究了薄膜在不同温度和不同偏压下的光电特性和相变特性。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)测试了钨镍共掺杂V_(2)O_(5)薄膜的晶体结构、表面形貌和组分,分析了不同钨镍共掺杂浓度对V_(2)O_(5)薄膜相变光电特性的影响。结果表明,当钨和镍的掺杂质量分数分别为3%和1.5%时,钨镍共掺杂的V_(2)O_(5)薄膜的相变温度为218.5℃,在可见光范围内有较高的透过率,在近红外1310 nm波长处的光学透过率达48.83%,与未掺杂V_(2)O_(5)薄膜的光学透过率相比提高了10.29%,薄膜电阻降低了30.53%,热致回线宽度收窄为15℃,说明钨镍共掺杂的V_(2)O_(5)薄膜具有良好的可逆相变光电特性,有望在新型光电器件领域得到较好的应用。

室温固相反应助力制备氮硫共掺杂碳限域的FeCoS_(2)复合物用于高性能钠离子电池负极

利用室温固相自组装反应制备Co和Fe双席夫碱配合物,随后在硫粉存在下中温热处理,使该配合物同时发生热解碳化和固相硫化反应,从而获得N、S共掺杂碳限域的FeCoS_(2)纳米复合物(记为FeCoS_(2)■NSC)。通过粉末X射线衍射、透射电镜、X射线光电子能谱和热重分析技术分别对纳米复合物的物相、形貌结构、组分和含量等进行物理表征,并通过循环伏安、恒电流充放电技术测试其电化学储钠性能。研究结果表明,最优化条件下制备的复合物(FeCoS_(2)■NSC-7001)中FeCoS_(2)粒子的平均尺寸约为3.4 nm,且被均匀限域在N、S共掺杂的碳基体中;该复合物作为钠离子电池负极时,在0.1 A·g^(-1)的电流密度下经过300次充放电循环,其可逆充电比容量仍高达310.4 mAh·g^(-1);即使在5 A·g^(-1)的大电流密度下,其充电比容量也高达146.0 mAh·g^(-1),呈现优异的电化学储钠性能。

First-principles study of the electronic and optical properties of the (Y,N)-codoped anatase TiO_2 photocatalyst

First-principles plane-wave pseudopotential calculations are performed to study the geometrical structures, for- mation energies, and electronic and optical properties of Y-doped, N-doped, and （Y, N）-codoped Ti02. The calculated results show that Y and N codoping leads to lattice distortion, easier separation of photogenerated electron-hole pairs and band gap narrowing. The optical absorption spectra indicate that an obvious red-shift occurs upon Y and N codoping, which enhances visible-light photocatalytic activity.

Electrochemical performance of C-La^(3+) codoped LiFePO_4 synthesized by microwave heating

La3+ was selected to elevate the lattice electronic conductivity of LiFePO4,and LiFePO4/(C+La3+) cathode powders were synthesized by microwave heating using a domestic microwave oven for 35 min. The microstructures and morphologies of the synthesized materials were investigated by XRD and SEM. The electrochemical performances were evaluated by galvanostatic charge-discharge. The electrochemical performance of LiFePO4 with different La3+ contents was studied. Results indicated that the initial specific discharge capacity of LiFePO4/(C+La3+) composites with 2% La3+ (116.3 mAh/g) was better than that of LiFePO4/C (105.4 mAh/g). The addition of La3+ further improved the electrochemical properties. So the codoping is an effective method to improve the electrochemical performance.