锆英粉型壳与DD6单晶合金的界面反应

采用扫描电镜、能谱分析等手段研究了DD6单晶合金与锆英粉型壳的界面反应。结果表明,DD6高温合金与锆英粉型壳的界面反应产物为Al_2O_3、HfO_2、Nb/Ta氧化物和单质Si。由于锆英粉的主成分ZrSiO_4高温易分解,界面反应有局部加剧的趋势,反应产物粘附在型壳表面,导致界面处型壳侧生成5~8μm厚的Al_2O_3层,合金表面出现缺陷坑。通过分析"Al元素氧化-ZrSiO_4分解-低熔点富Si液相形成-Al_2O_3颗粒析出"的反应过程,建立了"反应坑"型的界面反应模型。     

一种镍基定向凝固高温合金与陶瓷铸模的界面反应研究

采用扫描电子显微镜和能谱等分析手段研究了某镍基定向凝固高温合金与SiO_2基陶瓷型壳以及Al_2O_3基陶瓷型芯的界面反应。实验结果表明,该镍基定向凝固合金与SiO_2基陶瓷型壳会发生较严重的界面反应,在合金与SiO_2基型壳之间有一层约3~5μm厚的白色HfO_2层和一层稀薄的Al_2O_3层,反应产物的富集可以抑制界面反应的进一步进行;而与Al_2O_3基型芯几乎不发生界面反应,只有微量的HfO_2在界面处零星分布。同时,这一结果符合了界面反应的热力学关系。虽然Al_2O_3基型芯能有效减少界面反应,但Al_2O_3基型芯存在较多的空隙,合金熔液在凝固时渗入其中增加了合金表面的粗糙度,提高Al_2O_3基铸型的致密度有利于提高合金铸件表面品质。     

CeN3O9.6H2O对镁空气电池负极性能的影响

通过动电位极化法和电化学阻抗谱法,研究了在8%NaCl电解液中,六水合硝酸铈(CeN_3O_9·6H_2O)对AZ31负极抗腐蚀性能的影响。结果表明:电解液中加入Ce N_3O_9·6H_2O,在AZ31镁合金表面形成Ce(OH)_3保护膜,提高镁合金的耐腐蚀性。随着CeN_3O_9·6H_2O浓度的增大,Ce(OH)_3保护膜逐渐致密,AZ镁合金的腐蚀速率降低。当Ce N_3O_9·6H_2O浓度达到1.0 g/L时,镁合金的腐蚀速率最低,其缓蚀率为70.4%。然而当加入的Ce N_3O_9·6H_2O浓度大于1.0 g/L时,由于Ce(OH)3保护膜被溶解而导致镁合金的腐蚀速率增大。由浸泡50 h AZ合金的SEM图发现CeN_3O_9·6H_2O的添加在镁合金表面形成Ce(OH)_3保护膜,抑制阳极反应。从等效电路图得到Mg~(2+)电荷转移阻力增大了69.5?,改善了镁合金的耐腐蚀性能。通过放电测试得到加入CeN_3O_9·6H_2O提高电池的放电性能,放电时间延长40 min。     

Al_2O_3型壳与DZ22合金的界面反应研究

为解决Al2O3陶瓷型壳与DZ22合金的界面反应问题,通过浇注试验制得试样,借助光学显微镜、SEM、EDS等手段对所得试样的形貌、成分、界面等进行了研究。结果表明,DZ22合金与Al2O3型壳的反应产物表面呈现粉红色,产物主要是Cr2O3;金属-型壳界面处为白色的HfO2反应层;随着Al2O3型壳成分中杂质含量的增加,界面反应的程度逐渐增加。     

单晶高温合金/Al2O3型壳界面行为研究

采用直接浇注法制备金属型壳界面行为试样，其金属为单晶高温合金DD3、DD6，型壳为Al2O3。通过金相显微镜、扫描电镜及能谱分析对试样表面进行研究。结果表明，采用Al2O3型壳铸造出的DD3、DD6单晶铸件外表面光洁，Al2O3型壳可用于DD3、DD6单晶高温合金的熔模铸造工艺。     

DZ22B高温合金与Al_2O_3陶瓷型壳的界面反应

采用真空感应熔炼与惰性气体保护相结合,研究了不同熔炼温度及接触时间条件下DZ22B高温合金与Al_2O_3陶瓷型壳的界面反应发生及形成规律,探讨了界面反应对铸件表面粘砂缺陷的影响。结果表明,高温合金中Hf元素活性大,易与Al_2O_3发生界面反应,合金表面形成HfO_2。当接触15min后,界面反应随熔炼温度的提高而增强,在1 400℃时未出现界面反应,1 500℃时发生微弱界面反应,1 600℃时界面反应加剧,并出现粘砂现象。由于型壳面层中物理渗透层的形成以及应力集中的出现,界面反应的存在导致面层材料发生脱落,其中在接触30 min,浇注温度为1 600℃时粘砂最为严重,合金表面形成厚1mm的面层粘砂产物。     

陶瓷颗粒含量对Cr-Al_2O_3复合镀活塞环摩擦磨损性能的影响

为了研究陶瓷颗粒含量对Cr-Al_2O_3复合镀活塞环摩擦磨损性能的影响,采用镀铬活塞环和4种Al_2O_3陶瓷颗粒含量不同的Cr-Al_2O_3活塞环与CuNiCr合金铸铁缸套组成配对副,对其进行摩擦磨损试验,对比各配对副摩擦因数及磨损量。结果表明,镀铬活塞环-缸套配对副摩擦因数较大,约为其它4种含Al_2O_3陶瓷颗粒的Cr-Al_2O_3活塞环-缸套配对副的1.2倍,磨损也比其它4种配对副严重,摩擦副的表面均已经发生严重的粘着磨损现象;其它4种含陶瓷颗粒的Cr-Al_2O_3活塞环-缸套配对副的摩擦因数相近,缸套的磨损量也相近,活塞环的磨损量随着陶瓷含量的增加而先减小后增加。陶瓷颗粒的镶嵌提高了活塞环的耐磨性能,陶瓷含量过少,活塞环表面承载能力不足;陶瓷颗粒含量过多,陶瓷颗粒易脱落,这些都会增大活塞环的磨损量。     

TC4合金表面Ni-SiC-Y2O3复合镀层的摩擦磨损性能

为提高TC4合金表面耐磨性能,采用复合镀方法在其表面制备Ni-SiC-Y_2O_3复合镀层,研究镀层的组织结构及其在常温和高温下(600℃)下的摩擦磨损行为。结果表明,所制备的Ni-SiC-Y_2O_3复合镀层组织致密且与基体结合紧密,主要由Ni基体和弥散分布其中的SiC颗粒及微量Y_2O_3混合组成。镀层的硬度明显高于TC4基体合金,且由表向内呈梯度降低趋势。与GCr15对摩时,Ni-SiC-Y_2O_3复合镀层在常温和600℃均具有一定程度的减磨作用,并且耐磨性能明显优于TC4基体合金。镀层在常温下的磨损失重显著低于TC4基体合金,此时其磨损机制可以归结为疲劳磨损和轻微的氧化磨损;随磨损温度升高至600℃,镀层的磨损失重明显增大,此时的磨损机制为严重的氧化磨损、削层磨损和疲劳磨损。     

Al2O3陶瓷/AgCuTi/GH99高温合金的钎焊接头力学性能

采用AgCuTi钎料对Al₂O₃陶瓷与GH99高温合金进行了钎焊连接,研究了工艺参数(连接温度、保温时间)的变化对接头力学性能的影响,并分析了不同参数下接头的断裂位置,结果表明：保温5min时,在不同的连接温度下进行钎焊,随着连接温度的升高,接头的抗剪强度先增后减,在900℃时取得最大值,为127.24MPa,连接温度较低时,主要断裂于Al₂O₃/钎料侧,随着温度的升高,接头TiNi₃反应层增厚,因此还有部分断裂于TiNi₃反应层/钎料界面;在连接温度为900℃时,随着保温时间的延长,接头的抗剪强度逐渐降低,保温时间较短时,主要要断裂于Al₂O₃/钎料界面,保温时间过长,TiNi₃反应层延伸入钎料中部且厚度大大增加,在该反应层中产生微裂纹,造成接头强度大大降低,此时部分断裂于钎料中部及TiNi₃反应层中。     

Fe2O3-CaO-TiO2 体系下铁酸钙的合成过程及TiO2 和CaTiO3 的影响

为了确定高钛型钒钛磁铁矿烧结过程中铁酸钙的生成是受TiO₂还是TiO₂和CaO形成的CaTiO₃影响,首先利用Fe₂O₃和CaO的纯试剂合成了铁酸钙,并研究了TiO₂和CaTiO₃对钛铁酸钙 （FCT） 形成的影响。在Factsage 7.0软件进行热力学计算的基础上,通过在空气气氛下进行烧结,获得了在1023~1423 K温度范围内、不同烧结时间的不同样品。通过X射线衍射和扫描电镜-能谱分析等表征手段,对烧结样品的物相转变和微观结构变化进行了表征。发现FCT的形成过程主要分为2个阶段：前一阶段为1023~1223 K温度范围内Fe₂O₃与CaO之间的反应,合成产物为Ca₂Fe₂O₅,反应方程式为“Fe₂O₃(s)+ 2CaO(s)= Ca₂Fe₂O₅(s)”;后一阶段为1223~1423 K温度范围内Ca₂Fe₂O₅和Fe₂O₃的反应,主要产物为CaFe₂O₄,反应为“Ca₂Fe₂O₅(s)+ Fe₂O₃(s)= 2CaFe₂O₄(s)”,该阶段尤其是温度为1423 K时,反应速率显著加快,随温度的升高CaTiO₃显著增加。然而,Ti元素在铁酸钙中的固溶很难实现,TiO₂与铁酸钙之间的反应不是形成FCT的有效途径。随着保温时间的延长,CaTiO₃和FCT相界中Fe元素含量增加。FCT主要是通过Fe组分在CaTiO₃中固溶形成的,主要反应是“Fe₂O₃+CaTiO₃(s)=FCT(s)”。     

改进型镁扩散法制备高临界电流密度MgB2超导体性能研究

本文采用一种改进型镁扩散法成功制备出密度达到1.95g/cm₃的MgB₂超导块材。论文研究了不同的热处理条件对MgB₂块材的超导转变温度(T_c)和临界电流密度(J_c)性能的影响。采用最佳热处理条件制备的MgB₂超导体T_c和J_c分别达到了38.1K和0.53MA/cm₂(10K,自场)。为了改进镁扩散法MgB₂超导体中弱的高场磁通钉扎性能,本文还研究了nano-Pr₆O₁₁和C掺杂对MgB₂超导体的临界电流密度和不可逆场(H_irr)的影响。结果表明C掺杂的MgB₂超导体临界电流密度在10K,6T下达到了10₄A/cm₂,该结果比未掺杂MgB₂超导体在同样条件下性能提高了两个量级,甚至比固态反应法制备的nano-C掺杂MgB₂超导体性能更好。利用该方法制备的nano-Pr₆O₁₁掺杂的MgB₂超导体在10K,2T下也比未掺杂样品J_c提高达9.4倍。根据大量的实验结果和理论分析我们提出基于改进型镁扩散法和化学掺杂,包括纳米粒子和C掺杂,很有可能是一种制备高性能MgB₂超导体非常有效的途径。     

废旧锂离子电池中Li, Fe和V的回收及xLiFePO4-yLi3V2(PO4)3的制备

由于LiFePO_4和Li_3V_2(PO_4)_3材料的特征相近,制备方法类似,提供了一种从废旧LiFePO_4和Li_3V_2(PO_4)_3混合电池中回收Li、Fe和V,再制备xLiFePO_4-yLi_3V_2(PO_4)_3的方法。在空气气氛中600℃热处理1h后,去除粘结剂PVDF使活性物质与集流体分离。调节Li、Fe、V和P摩尔比,球磨、锻烧,配制不同比例的xLiFePO_4-yLi_3V_2(PO_4)_3(x:y=5:1,7:1,9:1)复合电极材料。表征了其形貌、结构和电化学性能,结果表明,回收制备的复合材料将同时具备LiFePO_4和Li_3V_2(PO_4)_3两种材料的电化学性能,能显著改善LiFePO_4的倍率性能。     

Improved capacity and rate capability of Ru-doped and carbon-coated Li4Ti5O12 anode material

Pure Li₄Ti₅O₁₂, modified Li₄Ti₅O₁₂/C, Li₄Ru_0.01Ti_4.99O₁₂ and Li₄Ru_0.01Ti_4.99O₁₂/C were successfully prepared by a modified solid-state method and its electrochemical properties were investigated. From the XRD patterns, the added sugar or doped Ru did not affect the spinel structure. The results of electrochemical properties revealed that Li₄Ru_0.01Ti_4.99O₁₂/C showed 120 and 110 mAh/g at 5 and 10 C rate after 100 charge/discharge cycles. Li₄Ru_0.01Ti_4.99O₁₂/C exhibited the best rate capability and the highest capacity at 5 and 10 C charge/discharge rate owing to the increase of electronic conductivity and the reduction of interface resistance between particles of Li₄Ti₅O₁₂.It is expected that the Li₄Ru_0.01Ti_4.99O₁₂/C will be a promising anode material to be used in high-rate lithium ion battery.     

Preparation and characteristic of spherical Li3V2(PO4)3

Spherical Li₃V₂(PO₄)₃ was synthesized by using N₂H₄ as reducer. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that single-phase, spherical and well-dispersed Li₃V₂(PO₄)₃ has been successfully synthesized in our experimental process. Electrochemical behaviors have been characterized by charge/discharge measurements. The initial discharge capacities of Li₃V₂(PO₄)₃ were 123 mAh g⁻¹ in the voltage range of 3.0–4.3 V and 132 mAh g⁻¹ in the voltage range of 3.0–4.8 V.     

Synthesis of lanthanum carbonate nanoparticles via sonochemical method for preparation of lanthanum hydroxide and lanthanum oxide nanoparticles

Lanthanum carbonate nanoparticles were synthesized from the reaction of lanthanum acetate and Na₂CO₃ under sonication via sonochemical method. Lanthanum hydroxide nanoparticles were prepared by facial hydrothermal processing from the resulted product at 110 °C for 24 h. The role of surfactant, calcination temperature and sonication time were investigated on the morphology and particle size of the products. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and Fourier transform infrared (FT-IR) spectra. La₂O₃ nanoparticles were obtained by calcinations of the nanoparticles of lanthanum carbonate at 600 °C.     

Effects of K2O-Li2O doping on surface and catalytic properties of Fe2O3/Cr2O3 system

The effects of K₂O and Li₂O-doping (0.5, 0.75 and 1.5 mol%) of Fe₂O₃/Cr₂O₃ system on its surface and the catalytic properties were investigated. Pure and differently doped solids were calcined in air at 400-600 °C. The formula of the un-doped calcined solid was 0.85Fe₂O₃:0.15Cr₂O₃. The techniques employed were TGA, DTA, XRD, N₂ adsorption at −196 °C and catalytic oxidation of CO oxidation by O₂ at 200-300 °C. The results revealed that DTA curves of pure mixed solids consisted of one endothermic peak and two exothermic peaks. Pure and doped mixed solids calcined at 400 °C are amorphous in nature and turned to α-Fe₂O₃ upon heating at 500 and 600 °C. K₂O and Li₂O doping conducted at 500 or 600 °C modified the degree of crystallinity and crystallite size of all phases present which consisted of a mixture of nanocrystalline α- and γ-Fe₂O₃ together with K₂FeO₄ and LiFe₅O₈ phases. However, the heavily Li₂O-doped sample consisted only of LiFe₅O₈ phase. The specific surface area of the system investigated decreased to an extent proportional to the amount of K₂O and Li₂O added. On the other hand, the catalytic activity was found to increase by increasing the amount of K₂O and Li₂O added. The maximum increase in the catalytic activity, expressed as the reaction rate constant (k) measured at 200 °C, attained 30.8% and 26.5% for K₂O and Li₂O doping, respectively. The doping process did not modify the activation energy of the catalyzed reaction but rather increased the concentration of the active sites without changing their energetic nature.     

Low temperature sintering and microwave dielectric properties of (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics with BaCu(B2O5) additions

The effects of BaCu(B₂O₅) additives on the sintering temperature and microwave dielectric properties of (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics were investigated. The (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics were not able to be sintered below 1000 °C. However, when BaCu(B₂O₅) were added, they were sintered below 1000 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B₂O₅) was formed during the sintering and assisted the densification of the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics at low temperature. BaCu(B₂O₅) powders were produced and used to reduce the sintering temperature of the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics. Good microwave dielectric properties of Q × f = 35,000 GHz, ?_r = 18.5.0 and τ_f = −51 ppm/°C were obtained for the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics containing 7 wt.% mol% BaCu(B₂O₅) sintered at 950 °C for 4 h.     

固相-水热法制备LiFePO4-Li3V2（PO4）3复合材料及其电化学性能（英文）

分别采用固相-水热法和球磨法制备磷酸亚铁锂-磷酸钒锂复合正极材料(LiFePO4-Li3V2(PO4)3)。电化学性能测试表明,LiFePO4-Li3V2(PO4)3复合正极材料的电化学性能远远高于 LiFePO4和 Li3V2(PO4)3单独作为正极材料的性能,并且以固相-水热法制备的复合材料性能优于以球磨法制得的复合材料。研究发现 LiFePO4-Li3V2(PO4)3复合材料有 4 个氧化还原峰,相当于 LiFePO4 和 Li3V2(PO4)3 氧化还原峰的叠加。采用固相-水热法制备的LiFePO4-Li3V2(PO4)3 复合材料形貌较为规则,且有新相物质产生,这是导致其电化学性能较好的原因。     

Effects of Mo and Al Additions on the Sulfidation Behavior of 310 Stainless Steel

The high-temperature sulfidation behavior of 310stainless steel (310SS) with Mo and Al additions (up to10 at.%) was studied over the temperature range700-900°C in pure-sulfur vapor over the range of 10^-3 to 10^-1 atm. Thecorrosion kinetics followed the parabolic rate law inall cases and the sulfidation rates increased withincreasing temperature and sulfur pressure. Thesulfidation rates decreased with increasing Mo and Al contents and it wasfound that the addition of 10 at.% Mo resulted in themost pronounced reduction among the alloys studied. Thescales formed on 310SS with Mo additions were complex, consisting of an outer layer of ironsulfide (with dissolved Cr), (Fe,Ni)₉S₈, andCr₂S₃/Cr₃S₄(with dissolved Fe), and an inner heterophasic layer ofFe_1-xS,Cr₂S₃/Cr₃S₄,NiCr₂S₄,Fe_1.25Mo₆S_7.7, FeMo₂S₄, andMoS₂. The scales formed on 310SS with Mo andAl additions had a similar mixture as above, except thatAl_0.55Mo₂S₄ was alsoobserved in the inner layer. The formation ofMoS₂ andAl_0.55Mo₂S₄ partly blocked the transport of cations throughthe inner scale, resulting in the reduction of thesulfidation rates compared to 310SS.     

Alloyed W–(Co,Ni,Fe)–C phases for reaction sintering of hardmetals

It has been shown that W–Co–C phases could dissolve a substantial amount of metals such as V, Cr and Ta, which are known to positively influence the microstructure of hardmetals with respect to uniform grain size distribution and fine grain size. This offers a tool to circumvent the conventional doping of hardmetals with individual carbides. In the present study we used double- and triple-alloyed κ-W₉Co₃C₄ (i.e. κ-(W,V,Cr)₉Co₃C₄ and κ-(W,V,Cr,Ta)₉Co₃C₄) and applied a variety of sintering experiments to obtain WC–Co, WC–(Ti,Ta,Nb)C–Co and WC–(Ti,Ta,Nb)(C,N)–Co hardmetals. We also prepared κ-W₉Fe₃C₄, alloyed κ-W₉Ni₃C₄, and κ-W₉(Fe/Ni)₃C₄, and used the latter for sintering.