微细电解加工用中空电极的制备

为了改进加工间隙内电解产物的排出条件和加速电解液的更新,提出了一种嵌套式微细中空电极的精确可控焊接制备工艺。仿真分析了电极的过流特性,优化了电极长度,并进行了性能测试及加工实验。通过穿丝、黏结、嵌套尺寸及位置调整和焊接工序,制备出加工段内径为65μm、外径为130μm、长3.25mm左右,后段便于装夹和连通的嵌套式中空电极。在供液压力为1.15 MPa时,其出口流速可达10m/s左右。利用制备的中空电极,开展微细孔电解加工实验,在0.5mm厚不锈钢片上加工出最小入口孔径约为157μm,出口孔径约为133μm的微细孔,并将其延伸应用于微结构加工中,铣削出了长554μm、宽160μm、深224μm的微细T型槽。实验结果表明:制备的微细中空电极有效提高了加工间隙内电解液的流动特性,且连/导通可靠、装夹方便,适用于高深宽比微结构的电解加工。

双极性电泳法的微细中空电极侧壁绝缘层制备

针对孔径(100~200)μm高深宽比微细孔电解加工中,电极侧壁绝缘层在电解液冲击和气泡撕裂中易损伤/脱落等问题,提出一种基于丙烯酸环氧树脂双极性电泳法的微细中空电极侧壁绝缘制备工艺。通过工艺参数优化后,利用所制备的侧壁绝缘电极,开展加工对比实验,结果表明双极性电泳法所制备的侧壁绝缘层,具有较高的致密性、均匀性、耐久性和一致性,其性能符合微细电解加工对电极侧壁绝缘层的特殊要求。最后,在500μm厚304钢片上加工出入口约168.4μm、出口约165.8μm、锥度约为0.15°的高深宽比微细孔,其锥度降低了约60%以上,基本为直孔,可满足实际需求,进而验证了本方法的应用可行性。

直流钢包炉中空电极喷吹Ar-H_2混合气体对钢水温度的影响

在100kg多功能直流钢包炉(DC-LF)上,通过LF中空石墨电极喷吹Ar-H2混合气体进行了精炼低碳钢的实验研究。实验结果表明,与实心电极冶炼相比,通过LF中空石墨电极喷吹Ar和Ar-H2气体后,熔池的升温速率明显加快。随着Ar-H2混合气体中H2体积分数的增加,体系粒子数密度增大,升温速率增大。喷吹??(Ar)=80%和??(H2)=20%的混合气体的平均升温速率最大,是采用实心电极冶炼时平均升温速率的6.92倍。通过LF中空石墨电极喷吹Ar或Ar-H2混合气体时,电弧电流不变,电压降低。

微细电解加工中空电极侧壁绝缘层的制备工艺研究

针对孔径100~200μm高深宽比微细孔电解加工中,电极侧壁绝缘层在电解液冲击和气泡撕裂中易损伤/脱落等问题,本文提出一种丙烯酸环氧树脂电泳法的中空电极侧壁绝缘制备工艺。通过优化工艺参数并开展加工实验,比较加工孔尺寸及形貌、加工后电极表面形态,结果表明丙烯酸环氧树脂电泳法制备的中空电极侧壁绝缘层,具有较高的致密性、均匀性、耐久性和一致性。最后,在500μm厚304不锈钢片上加工出入口180.6μm、出口173.8μm、深宽比约为3的微细阵列孔,其锥度比非侧壁绝缘电极加工的孔减少了约70%以上,基本为直孔,可满足实际需求,进而验证了本方法的应用可行性。

微细中空电极流速测试及侧壁绝缘层制备工艺比较

针对孔径100~200μm、采用中空供液工艺的高深宽比微细电解加工中,中空电极流速难以在线测量,侧壁绝缘层易出现损伤、脱落等问题,利用不同压力下流速雾化现象在光照下的差异性,建立压力-流速-雾化面积比关系曲线,实现在线流速测试并优化了初始供液压力。通过比较加工孔和加工后电极表面形貌,优选出丙烯酸环氧树脂绝缘层制备工艺,并在304不锈钢片上加工出入口直径180.6μm、出口直径173.8μm、锥度约0.78°的阵列孔,验证了方法应用的可行性。

电石炉中空电极控制技术的研究

本文给出了基于S7-300型PLC、Profibus-DP现场总线、ET200和WINCC组态软件构成的中空电极控制系统的设计,并介绍了系统的主要硬件配置、通信网络构成、WINCC组态画面。

中空电极钛渣电弧炉内电弧特性的模拟

钛渣电弧炉内电弧特性对炉料融化以及还原过程具有重要影响。采用流体力学耦合电磁场的方法,建立了钛渣电弧炉内电弧区域的数学模型,对电弧区内的多物理场进行了模拟,研究了中空电极对电弧区域内的流场、温度场及电磁场的影响,并对比分析了实心电极与中空电极的差异。结果表明,与实心电极相比,中空电极的温度场仍呈“钟罩型”分布,但由于洛伦兹力和压力导致中空区域附近出现较大的负速度,阻碍了中空电极处的进料。进一步研究发现,中空电极内径的大小会影响电弧区域电流密度分布,继而决定了洛伦兹力和压力的分布特征,揭示了中空电极对电弧特性的影响机制。

薄型中空电极振动电解切割TB6钛合金

TB6钛合金由于具有优越的性能,广泛地用于航空航天领域。然而从大余量的TB6钛合金锻铸件毛坯加工成复杂结构的零件,其加工效率低,刀具和机床成本高,造成了极大的浪费。为解决这一问题,提出了一种利用薄型中空电极进行快速大余量去除的电解加工(ECM)方法,即将零件与多余材料切割分离,有望较大程度提高加工效率,降低加工成本。为改善电解加工流场特性,提高加工精度,对电极施加振动,并对薄型中空电极的振动切割进行了建模分析和试验研究。试验结果表明,合适的振动幅值和频率(A=0.05mm,f=50Hz)可以使得各处电解液电导率趋于一致,从而提高加工的精度、稳定性和效率。复杂结构件的成功切割证明了薄型中空电极振动电解切割加工技术具有一定的适用性。

中空、实心电极电炉熔炼钛渣过程中电弧特性的对比研究

为了深入探究中空电极技术在钛渣电炉冶炼工艺中的优势所在,以25.5 MW钛渣电炉实际电极尺寸为基础,分别建立了中空和实心电极电弧的数学模型,模拟得到中空、实心电极电弧的电磁场、温度场和流场分布特性,研究了电流大小和电弧长度对熔池表面温度分布的影响规律。结果表明,电弧内电流密度、焦耳热值、速度和温度的较大值位于阴极斑点附近,中空电极是内外径中心线下方区域,实心电极是中心轴线附近区域。采用中空电极时,周围的电弧会向中轴线汇聚,该现象有利于提高电弧加热物料的效率。当电流值由34 kA增大到54 kA,两种情形下的熔池表面平均温度分别提升了708 K和109 K。当电弧长度由0.3 m缩短到0.1 m,两种情形下的熔池表面平均温度分别提升了2 500 K和46 K。相比于实心电极,中空电极更适合采用大电流和短弧长的运行方式,且合理控制弧长对提高中空电极电弧加热效率的效果更显著。

采用电补偿方案的新一代立式计算电容装置

针对立式计算电容最大不确定度来源的端部效应误差,中国计量科学研究院经过多年改进,研制出的最优中空电补偿电极在计算电容模型装置上,没有采用加装钉子头进行补偿的电补偿方案,并完成了诸如端部效应误差的补偿效果、偏心效应误差等电气性能验证试验,成功应用在新一代立式计算电容装置上。实验结果表明,采用电补偿方案的新一代立式计算电容装置复现1 pF电容单位的相对标准不确定度为1.0×10^-8。

基于间隙阻抗的微细孔电解加工伺服控制

为提高直径在100~200μm微细孔的电解加工效率,从间隙控制的角度出发,采用侧壁绝缘电极、高压中空冲液和高频脉冲电源的加工工艺下,建立微细孔加工模型,提出了基于间隙阻抗的微细孔电解加工的伺服控制方法,并对比恒速进给模型、平均电压电流的伺服控制方法,对微细孔的电解加工间隙进行控制。实验表明,基于间隙阻抗的微细孔模型伺服控制方法加工时间短、加工效率高,所得孔的出、入口尺寸小。

石化行业成为低碳经济践行者

目前我国在石化行业已经有多项技术取得了突破，包括干法乙炔技术，大型密闭式电石炉、中空电极和炉气综合利用技术，黄磷电除尘技术和尾气综合利用技术，铬盐无钙焙烧技术，氮肥生产污水零排放技术和氮肥节能技术等。这些技术的突破，为我国石化产业的低碳发展提供了很好的基础。

采用矿热电炉-立磨机技术利用金川冶炼弃渣生产合金铁低硅硅铁和矿渣微粉可行性探讨

金川集团公司镍冶炼系统每年产出160万t镍熔融渣,渣场堆存冷渣5000万t。采用中空电极等离子矿热电炉,处理冷渣和部分热渣,生产合金铁、低硅硅铁,工艺技术成熟,技术经济指标较好,大中型矿热电炉设备制造完全国产化,投资省效益好;二次渣成分与高炉渣接近,采用辊式立磨机生产矿渣微粉,性能优异成本低,是全部综合利用冶炼弃渣的有效途径。

用等离子炬提高钒在铁渣间的还原率

用中空单石墨电极等离子体感应炉研究了在等离子条件下钒在渣铁间的还原规律。试验证明，在等离子条件下，Ｓｉ－Ｖ耦合反应的平衡能向高温方向移动，ＶＯ还原速度急剧提高，存在着用碳还原法代替金属热还原法冶炼钒铁和类似的铁合金的可能性。

Investigation of Cathode Catalysts for Intermediate-temperature H2S-Air Fuel Cells

Abstract Cathode catalysts comprising composite NiO, NiO-Pt, or LiNiO2 have been developed for electro- chemical oxidation of hydrogen sulfide in intermediate-temperature solid oxide fuel cells （ITSOFCs）. All catalysts exhibited good electrical conductivity and catalytic activity at operating temperature. Composite NiO catalysts were found to be more active and have lower over potential and higller current density than pure Pt although the electrical conductivity of NiO itself is lower than that of Pt. This problem has been overcome by either admixing as high as 10% （by mass）Ag powder into NiO_ cathode layer or using composite NiO c atalysts such as NiO-Pt and LiNiO2 catalysts. Composite catalysts like NiO with Ag, electrolyte and starch admixed, NiO-Pt, which was prepared from a mixture of NiO and Pt powders, by admixing electrolyte and starch, and LiNiO2, which is derived from the reaction of LiOH-H2O and NiO with electrolyte and starch admix_ed have been shown to be feasible and effective in an intermediate-temperature H2S-air fuel cell. A fuel cell using Li2SO4-based proton-conducting membrane as electrolyte, metal sulfides as anode catalysts, and composite NiO as cathode catalysts produced a maximum current density about 300mA·cm^-2 and maximum power density over 80 mW-cm-2 at 680℃.

用等离子体炬提高钒在铁渣间的还原率

作者用中空石墨电极等离子体感应炉研究了在等离子体条件下钒在铁渣间还原的规律。研究结果证实，在等离子体条件下，Ｓｉ－Ｖ耦合反应能迅速达到平衡，ＶＯ的还原速率急剧提高，存在着用碳还原法代替昂贵的金属热还原法来冶炼钒铁和类似的铁合金的可能性。

Ni3S2@S-carbon nanotubes synthesized using NiS2 as sulfur source and precursor for high-performance sodium-ion half/full cells

Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2(abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source.No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g^-1 at 0.1 A g^-1 after 100 cycles with exceptional capacity retention of 98.6%.Furthermore, they maintained excellent rate capability of 318 mA h g^-1 even at elevated current density of 5 A g^-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3(NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte,enhanced surface ion storage performance(capacitive effect),and improved structural stability of electrode materials.

Self-template synthesis of hierarchically structured Co3O4@NiO bifunctional electrodes for selective nitrate reduction and tetrahydroisoquinolines semidehydrogenation

The rational design and synthesis of hierarchically hollow nanostructures with controlled spatial architecture and composition are significant in electrocatalysis owing to their abundant active sites and the expedited electron/mass transfer.Electrocatalytic nitrate reduction to ammonia is of great interest from the points of environmental protection and energy saving.However,the development of this technology is hindered by the lack of efficient nitrate-toammonia electrocatalysts and the kinetically sluggish oxygen evolution reaction at the anode.Herein,a novel self-template conversion method was developed for the synthesis of Co3O4@Ni O hierarchical nanotubes(Co3O4@Ni O HNTs)with Ni O porous nanosheets assembled on Co3O4nanotubes.The as-obtained Co3O4@Ni O HNTs exhibited an outstanding performance for both the cathodic nitrate electroreduction to ammonia reaction and the anodic tetrahydroisoquinolines(THIQs)semi-dehydrogenation to dihydroisoquinolines(DHIQs).Importantly,a two-electrode system of Co3O4@Ni O HNTs||Co3O4@Ni O HNTs was constructed for the simultaneous synthesis of ammonia and DHIQs with high selectivity and robust stability.

SnO2@Co3O4 hollow nano-spheres for a Li-ion battery anode with extraordinary performance

SnO2@Co3O4 hollow nano-spheres have been prepared using the template-based sol-gel coating technique and their electrochemical performance as an anode for lithium-ion battery （LIB） was investigated. The size of synthesized hollow spheres was about 50 nm with the shell thickness of 7-8 nm. The fabricated SnO2@Co3O4 hollow nano-sphere electrode exhibited an extraordinary reversible capacity （962 mAh-g-1 after 100 cycles at 100 mA-g-1）, good cyclability, and high rate capability, which was attributed to the Co-enhanced reversibility of the Li20 reduction reaction during cycling.

Hollow and hierarchical Na_2Li_2Ti_6O_(14) microspheres with high electrochemical performance as anode material for lithium-ion battery

Relying on a solvent thermal method, spherical Na2Li2Ti6O14 was synthesized. All samples prepared by this method are hollow and hierarchical structures with the size of about 2-3 μtm, which are assembled by many primary nanoparticles （-300nm）. Particle morphology analysis shows that with the increase of temperature, the porosity increases and the hollow structure becomes more obvious. Na2Li2Ti6Ol4 obtained at 800℃ exhibits the best electro- chemical performance among all samples. Charge-discharge results show that Na2Li2Ti6O14 prepared at 800℃ can delivers a reversible capacity of 220.1, 181.7, 161.6, 144.2, 118.1 and 97.2 mA h g-1 at 50, 140, 280, 560, 1400, 2800 mA g-1. How- ever, Na2Li2Ti6O4-bulk only delivers a reversible capacity of 187, 125.3, 108.3, 88.7, 69.2 and 54.8 mA h g-1 at the same current densities. The high electrochemical performances of the as-prepared materials can be attributed to the distinctive hollow and hierarchical spheres, which could effectively reduce the diffusion distance of Li ions, increase the con- tact area between electrodes and electrolyte, and buffer the volume changes during Li ion intercalation/deintercalation processes.