煅烧温度对高镍无钴LiNi0.90Mn0.10O2正极材料结构与电化学性能的影响

采用固相法在不同的煅烧温度下(725～825℃)合成了高镍无钴LiNi_0.90Mn_0.10O₂正极材料,并通过结构表征和电化学测试考察了煅烧温度对正极材料的结构和电化学性能的影响。结果表明,煅烧温度会改变材料的晶胞参数,在最佳煅烧温度775℃时所制得的正极材料Li⁺/Ni²⁺混排程度最低;该煅烧温度制备的样品首次放电比容量最高,同时倍率性能也表现最佳,并且在循环200圈后仍然保持着最高的放电比容量。     

喷雾干燥法制备Na2MnPO4F/C正极材料及其电化学性能研究

本文采用喷雾干燥法制备了Na₂MnPO₄F/C复合正极材料,研究了合成温度对样品的结构、形貌及电化学性能的影响。研究表明,600～750℃下均能合成出单一的Na₂MnPO₄F,各样品均无杂相,随着温度的升高样品的结晶度增大。SEM结果表明,在较低温度(600～650℃)下合成的样品颗粒细小且分布均匀,而较高温度(700～750℃)下合成的样品颗粒明显增大且团聚较为严重。电化学测试结果表明,650℃下合成的Na₂MnPO₄F/C具有最优的电化学性能,该样品在0.05和0.1 C下的首次放电比容量为52.1和25.5 mAh/g,且具有较好的倍率和循环性能。     

锂铝硅系统微晶玻璃的析晶及热处理工艺研究

制备了Li2O-Al2O3-SiO2系微晶玻璃,采用差热分析(DTA)、X衍射分析(XRD)和扫描电镜(SEM)等分析手段对该系统微晶玻璃的析晶过程和微观结构进行了研究。通过正交实验讨论了热处理温度及时间对微晶玻璃热膨胀性能的影响。结果表明:通过热处理工艺来控制晶相的析出,析晶初始温度下首先析出的晶相为β-石英固溶体,随晶化温度升高β-石英固溶体转变为β-锂辉石固溶体,可以使样品的热膨胀性能符合要求。获得较小热膨胀系数的热处理工艺为:核化温度620℃,核化时间1小时,晶化温度840℃,晶化时间3小时。所获得的微晶玻璃的热膨胀系数为9.510-7/℃,可作为低膨胀材料使用。     

超低膨胀微晶玻璃热处理工艺优化研究

采用熔融法制备了Li₂O-Al₂O₃-SiO₂系透明玻璃,以TiO₂、ZrO₂和P₂O₅为复合晶核剂对该玻璃进行热处理,获得了超低膨胀微晶玻璃。采用正交试验研究了热处理工艺参数对微晶玻璃热膨胀系数的影响,并通过计算分析获得了最优的热处理工艺参数,即核化温度为600 ℃,核化时间为3 h,晶化温度为820 ℃,晶化时间为5 h。在此热处理工艺制度下获得的微晶玻璃主晶相为β-石英固溶体,热膨胀系数为1.6×10^-8 ℃^-1。采用差热分析、X射线衍射分析、扫描电子显微镜分析、透射电子显微镜分析等手段研究了微晶玻璃的析晶情况和微观结构,并进一步分析了热处理工艺与微晶玻璃热膨胀性能和微观结构之间的对应关系。结果表明,微晶玻璃的热膨胀系数由晶相种类和含量决定,微晶玻璃内部晶相的尺寸和含量与热处理工艺密切相关。     

热处理对Al2O3/PSZ(3Y)陶瓷材料结构和性能的影响

将烧结的Al2O3/PSZ(3Y)陶瓷材料在不同温度和时间下进行热处理,对不同热处理制度下的试样致密性能和力学性能进行了测试,用X射线衍射分析了热处理前后材料中的各晶相的变化情况。结果表明:1560℃烧结的Al2O3/PSZ(3Y)陶瓷材料,经1100℃热处理6小时后其抗弯强度达到680MPa,比未处理试样的强度提高了近30%。热处理后基体中出现的不同晶格常数的四方氧化锆晶相对提高材料的力学性能有利。     

热处理温度对锂电池硅/炭负极材料的影响

以多巴胺为碳源,在纳米硅表面包覆炭层,制备了锂离子电池负极用硅/炭复合材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和锂离子电池性能测试等方法研究不同热处理温度对材料物相组成、结构形貌和电化学性能的影响。结果表明,热处理温度越高,材料的结构越利于提高其电化学性能。1 100℃处理的硅/炭复合材料的颗粒呈近球形且炭层更均匀,循环性能也更优异,首次充放电效率高达77.24%,在100 m A·g~(-1)电流密度下充放电循环20次后放电比容量仍有715.4 m A·h·g~(-1)。     

高炉渣含量与热处理制度对矿渣微晶玻璃性能的影响

运用DTA、XRD和SEM等现代分析技术对CaO(MgO)-Al2O3-SiO2系矿渣微晶玻璃的核化晶化温度、物相组成和显微结构进行了分析，探讨了高炉渣引入量和热处理制度的影响。试验结果表明，当高炉渣加入量为45wt％时，主晶相为普通辉石(CaSiO3)和透辉石(CaMg(SiO3)2)，材料结构均匀致密，性能良好。本文适宜的热处理工艺参数为：退火温度670℃；核化温度850℃，晶化温度970℃，各保温1h。     

高掺量煤矸石固废微晶玻璃结构与性能研究

本文通过XRD、SEM、TG-DSC、耐腐蚀性、密度、硬度、断裂韧性等测试,研究不同热处理制度和煤矸石掺量对微晶玻璃晶体结构、微观形貌、物化性能的影响。结果表明,该体系煤矸石微晶玻璃析出的主晶相为钙长石相(CaAl₂Si₂O₈),随着热处理晶化温度的升高,析出的主晶相数量变多,尺寸变大,但主晶相种类并未改变。当热处理制度为核化温度750 ℃保温1 h、晶化温度1 000 ℃保温1 h时,主晶相晶体尺寸大小约300~400 nm。在优化热处理制度下,当煤矸石掺量从44%(质量分数)增加到70%时,4种不同煤矸石掺量微晶玻璃的物化性能相差不大。综合考虑煤矸石固废利用率和样品的物化性能指标,煤矸石掺量为70%的样品综合性能最佳。本文设计的煤矸石微晶玻璃体系,对煤矸石固废的包容性好,消纳性强,可实现煤矸石固废的大掺量高值化利用,为解决煤矸石固废堆积、环境污染等问题提供了理论基础和实验依据。     

回火温度对LiNi0.5Mn1.5O4结构、形貌及电化学性能的影响

以LiNO₃、Ni(NO₃)₂·6H₂O、Mn(NO₃)₂为主要原料，尿素作燃料，采用低温燃烧法合成了亚微米级、电化学性能良好、单晶形貌的5 V锂离子电池正极材料LiNi_0.5Mn_1.5O₄。考察了不同回火温度对所合成产物的结构、形貌和电化学性能的影响，并通过X射线衍射、扫描电镜和充放电实验对不同回火温度下合成的产物进行了表征。实验结果表明，在不同回火温度得到的样品均具有尖晶石结构。但是在回火温度为800℃和900℃下合成的样品产生了较多的杂质相，随着回火温度的升高，合成产物的结晶度逐渐提高，粒径逐渐增大。在回火温度为850℃得到的样品成清晰的八面体外形，结晶良好，粒径适中，在3.5～4.9 V内0.1 C倍率下首次放电容量最高，30次循环后其容量保持率最好，其电化学性能最好。     

高炉渣含量与热处理制度对矿渣微晶玻璃性能的影响

运用DTA、XRD和SEM等现代分析技术对CaO(MgO)—A12O3—SiO2系矿渣微晶玻璃的核化晶化温度、物相组成和显微结构进行了分析，探讨了高炉渣引入量和热处理制度的影响。实验结果表明，当高炉渣加入量为45％时，主晶相为普通辉石(CaSiO3)和透辉石(CaMg(SiO3)2)，材料结构均匀致密，性能良好。此实验的热处理工艺参数为：退火温度670℃；核化温度850℃，晶化温度970℃，各保温1h。     

Electrochemical reduction of pyrite in aqueous NaCl solution

Optimum conditions for pyrite removal from a high-sulfur coal by electrochemical reduction during flotation are determined by orthogonal experiments. The electrochemical reduction process of pure pyrite is examined with XRD, electrochemical and chemical analysis. The results show that the electrochemical reduction products of pyrite are FeS and S²⁻. During this process, the reactions at cathode are: FeS₂+2e→FeS+S²⁻ and 2H⁺+2e→H₂. The corresponding electrode potentials and kinetic equation are determined. The conversion of hydrophobic pyrite to hydrophilic FeS and S²⁻ by electrochemical reduction is beneficial to desulfurization from coal in floatation process.     

Polymer-assistant ceramic nanocomposite materials for advanced fuel cell technologies

In this study,nanocomposites of LaCePr-oxide (LCP) and Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) with different contents of polyvinylidene fluoride (PVDF) were prepared and applied to solid oxide fuel cells. The composite materials were characterized by X-ray diffraction analysis (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and electrochemical impedance spectrum (EIS). The effect of PVDF concentration on the conductivity and performance of the fuel cells was investigated. It was found that PVDF plays a template role of pore forming in the nanocomposites, and the changed microstructure by as-formed pores greatly influences the electrochemical property of the nanocomposites. The cell with 3 wt% PVDF heat-treated at 210 °C achieved the highest power density of 982 mW cm⁻² at 520 °C, which enhanced performance by more than 57% than when no heat-treatment was implemented. It is 66% higher than the cell with no PVDF and no heat-treatment. Pores formed by PVDF after heat-treatment enlarged the triple phase boundary (TPB), which results in improved fuel cell performance.     

Charge storage mechanism of sonochemically prepared MnO2 as supercapacitor electrode: Effects of physisorbed water and proton conduction

The charge storage mechanism of nanostructured hydrated manganese dioxide, as a supercapacitor electrode, was investigated with respect to the role of amount of hydrates on the electrolyte cations diffusion. The MnO₂ materials (γ- and layered types), prepared by a novel ultrasonic aided procedure. Thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize the water content of the samples. The samples then were heat-treated in air for 2 h at 70, 100 and 150 °C to prepare different γ- and L-series of electrodes with various amounts of hydrates. To determine the role of the protonic conduction on the charge storage mechanism, the electrochemical properties of the electrodes were investigated in two different electrolyte pH values of 3.3 and 6.Compared to γ25, the higher specific capacitance of L25, especially in more acidic electrolytes, is attributed to the higher amount of physically adsorbed water molecules and their contribution in diffusion process. Furthermore, it is clearly demonstrated that the total electrochemical performance of the systems under consideration is also influenced by the crystalline structure of the prepared electrodes, especially when the size of the tunnels limits the intercalation of cations.Analyzing the results of cyclic voltammetry and electrochemical impedance spectroscopy for both series of the electrodes, revealed that, increasing the heat-treatment temperature makes the charge-transfer resistance increase and the Warburg impedance decrease. This effect can be attributed to the more amount of surface physisorbed water lost by the higher heat-treatment temperatures.     

X-ray absorption spectroscopy studies of nickel oxide thin film electrodes for supercapacitors

Nickel oxide films were synthesized by electrochemical precipitation of Ni(OH)₂ followed by heat-treatment in air at various temperatures (200-600 °C). Their structure and electrochemical properties were studied by cyclic voltammetry, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). XRD results showed that the nickel oxide obtained at 250 °C or above has a crystalline NiO structure. The specific capacitance of the oxide depends on the heat-treatment temperature, showing a maximum value at 300 °C. XAS results revealed that the non-stoichiometric nickel oxide (Ni_1−xO) approached the stoichiometric NiO structure with increasing heat-treatment temperature due to the defect healing effect. The defective nature of the nickel oxide could be utilized to improve its specific capacitance for supercapacitor application.     

溶胶-乳化-凝胶法制备TiO2纳米粉体的晶化过程

将乳化技术与溶胶-凝胶方法相结合,通过"微乳反应器"来控制钛酸丁酯的水解速率和凝胶化过程,从而制备出分散性好的TiO2纳米粉体.通过X射线衍射(XRD),热重-差热(TG-DSC)和傅立叶变换红外光谱(FT-IR)对制备的TiO2纳米粉体在热处理过程的物化变化进行分析,并用扫描电镜(SEM)对其形貌和颗粒大小进行表征.结果表明:随着热处理温度的升高,TiO2粉体晶型从无定型,经过锐钛矿最终转变成金红石.在热处理过程中,TiO2纳米粉体的失重率达到38%.制备的TiO2纳米粉体分散性好,纳米颗粒平均尺寸15 nm.     

超细FeS对五彩湾煤直接液化性能的影响

以硫酸亚铁为铁源,硫化钠为沉淀剂,采用液相沉淀法合成了超细FeS催化剂。以四氢萘为溶剂,反应温度430℃、氢初压6.0 MPa、反应时间60 min、溶煤比2∶1条件下,探讨超细FeS催化剂对五彩湾煤直接液化性能的影响。结果表明：硫酸亚铁基超细FeS粒子形貌均一,呈细棒状;五彩湾煤直接液化实验的油产率、液化率和转化率,以2.0%（wt,以活性金属元素计,相对于干燥无灰煤,下同）超细FeS为催化剂的实验分别达到56.15、73.29和81.21%（wt,相对于干燥无灰煤,下同）,高于相同条件下,以3.0%分析纯Fe2O3为催化剂的实验产率（分别是44.00、49.33和62.05%）。     

Lithium storage performance of FeS@graphene anode materials prepared in a deep eutectic solvent

FeS has received widespread attention due to advantages such as high capacity, low-budget, and friendly to the environment. But side reactions during the charging and discharging process result in volume expansion of FeS, which limits its application and further development. In this work, FeS@graphene composites were prepared by a single step pyrolytic sulfidation method using PEG as the carbon source, FeCl₃·6H₂O as the iron source, metal chloride and organic alcohol as a deep eutectic solvent. The prepared composites which were characterized by SEM and TEM exhibited a strong bond between FeS and graphene, graphene had a lamellar structure, and FeS nanoparticles formed a homogeneous dispersion. Among the prepared composite material electrodes, the FeS/G-550 electrode displayed the best electrochemical properties with a high specific capacitance (initial discharge capacity: 1200 mAhg^-1; current density: 0.1 A g^-1), excellent rate capability (discharge specific capacitance of 443 mAh·g^-1 at the current density of 5 A g^-1), and good cyclic stability (capacity retention rate: 91%).     

Cobalt based non-precious electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Cobalt based non-precious metal catalysts were synthesized using chelation of cobalt (II) by imidazole followed by heat-treatment process and investigated as a promising alternative of platinum (Pt)-based electrocatalysts in proton exchange membrane fuel cells (PEMFCs). Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize the synthesized CoN_x/C catalysts. The activities of the catalysts towards oxygen reduction reaction (ORR) were investigated by electrochemical measurements and single cell tests, respectively. Optimization of the heat-treatment temperature was also explored. The results indicate that the as-prepared catalyst presents a promising electrochemical activity for the ORR with an approximate four-electron process. The maximum power density obtained in a H₂/O₂ PEMFC is as high as 200 mW cm⁻² with CoN_x/C loading of 2.0 mg cm⁻².     

Effect of heat-treatment of the oxidizability of smooth platinum anodes

The effect of heat-treatment on the electrochemical oxidizability of a smooth platinum electrode that had previously been oxidized and then reduced was investigated.

The growth rate of the multilayer oxide film by the anodic oxidation at 2·18 V(nhe) decreased with increase of the pre-annealing temperature and time. On the well-annealed electrode surface, only a monolayer oxide film was formed and the multilayer oxide was not developed.

The variation of the oxidizability by the heat-treatment was interpreted in term of the change in surface structure of the electrode. By the oxidation and reduction pre-treatment, the superficial platinum layer may be disordered. The activation energy for the rearrangement of platinum atoms in the disordered layer to the stable lattice position was estimated to be 11 ± 1 kcal/mol on the assumption that the oxidizability is proportional to the coverage of the disordered atoms. This result is in harmony with values calculated on the basis of both the vacancy migration mechanism and the adatom migration mechanism.     

污泥热解炭脱除NO特性

以废水污泥热解产生的污泥热解炭为原料,通过酸洗、活化、负载Fe、H₂还原等方式考察不同污泥热解炭样品对脱硝性能的影响。结果表明,污泥原样中的Fe₂P、FeS等低价态的铁具有良好的脱硝性能,450～500℃时最大脱硝效率达到81%。经过HNO₃酸洗和KOH活化后的污泥热解炭,因为去除了Fe₂P、FeS等低价态的铁,脱硝效率大幅下降,在450～500℃的最大效率分别仅为30%和53%。而热解污泥负载样中的Fe主要以Fe₂O₃形式存在,其最大脱硝效率在450～500℃时只有50%。经过H₂还原后,负载样中的Fe₂O₃被还原为Fe₂P、FeS等低价态的铁,其最大脱硝效率在450～500℃时上升至94%。