铁酸镍基金属陶瓷的强化烧结与熔盐腐蚀行为

采用气氛烧结方法制备NiFe2O4基金属陶瓷材料,并进行960℃的铝电解腐蚀实验.通过分析烧结体的显微结构和物相组成、电解试样的表层形貌与成分以及电解质和阴极铝的杂质含量等,研究BaO、Yb2O3和CoO的添加以及金属相的组成对NiFe2O4基金属陶瓷烧结性能的影响;表征J该金属陶瓷强化烧结体作为铝电解惰性阳极的电解腐蚀性能;并对材料强化烧结机制和熔盐腐蚀行为进行探讨.结果表明烧结过程中,BaO和Yb2O3与该金属陶瓷中的陶瓷相反应生成新的物相,CoO与陶瓷相形成固溶体,并加快烧结致密化进程;以Cu-Ni取代纯Cu和纯Ni作为金属陶瓷的金属相,可提高材料的相对密度;NiFe2O4基金属陶瓷的高致密度可抑制电解过程中金属相的流失和陶瓷相的腐蚀,阳极表层也转变为致密的NiFe2O4相.     

17（Cu-10Ni）-（NiFe2O4-10NiO）基金属陶瓷在铝电解过程中的相演变（英文）

采用冷压气氛烧结制备17(Cu-10Ni)-(NiFe2O4-10NiO)金属陶瓷,并作为阳极在960°C下分别进行10和40h的铝电解试验。对电解前后金属陶瓷的显微结构、物相成分进行分析检测。对电解质及阴极金属中的杂质含量进行分析,研究阳极组成中Fe、Ni和Cu元素的腐蚀行为。研究发现:在电解过程中,在材料表面形成NiFe2O4相致密层,该致密层随电解时间的延长而增厚。在NiFe2O4相致密层形成与增厚过程中,出现NiFe2O4相吞噬NiO相和金属相氧化的现象,金属陶瓷中Cu元素优先腐蚀溶解。并着重讨论NiFe2O4相致密层形成与增厚过程中金属相的腐蚀形式及NiO相向NiFe2O4相的转变机制。     

大尺寸NiFe2O4-10NiO/17Ni型金属陶瓷惰性阳极的制备

研究以PVA为主要成分的粘结剂体系的热分解特性对大尺寸粉末压坯脱脂行为的影响，发现PVA的不均匀热分解是造成大尺寸粉末压坯脱脂失效的原因之一，开发一种具有稳定热分解反应特性的新型粘结剂体系，实现大尺寸粉末压坯的无缺陷热脱脂；研究烧结气氛、金属相的添加对NiFe2O4-10NiO致密化行为的影响。结果表明：N2气氛烧结及加入Ni可有效提高NiFe2O4-10NiO陶瓷基体的烧结致密度，1350℃时于N2气氛中烧结的NiFe204．10NiO／5Ni型金属陶瓷材料的相对密度达到97．28％。采用优化工艺实现d120mmX140mm深杯状NiFe2O4-10NiO／17Ni金属陶瓷惰性阳极脱脂预烧坯的烧结，所得烧结坯平均相对密度为95．21％。     

气氛对NiFe2O4陶瓷烧结致密化的影响

采用不同的烧结工艺制备了NiFe2O4陶瓷材料,研究了真空、大气、N2 3种气氛对NiFe2O4陶瓷材料烧结致密度的影响,解决了烧结过程中NiFe2O4陶瓷的离解问题.结果表明:在制备NiFe2O4陶瓷过程中,烧结气氛严重影响着陶瓷的离解和致密化;真空烧结将导致NiFe2O4陶瓷的离解,N2气氛保护烧结所制备出的NiFe2O4陶瓷样品的密度较大气气氛烧结所制备出的样品的密度高出14.6%～32.6%.分析结果表明:因NiFe2O4陶瓷高温失氧所带来的表面能和晶体缺陷的差异是影响其致密化的关键;无论在何种气氛下烧结,提高烧结温度都有利于提高NiFe2O4样品的烧结密度.     

Co添加对17Ni-(10NiO-NiFe_2O_4)金属陶瓷的致密化及力学性能的影响

为了改善17Ni-(10NiO-NiFe2O4)金属陶瓷惰性阳极中金属相的分布,在原料中添加不同含量的Co,以Co-Ni取代纯Ni作为金属相,采用真空烧结方法制备17(x Co-Ni)-(10NiO-NiF e2O4)金属陶瓷,并研究Co添加量对金属陶瓷物相组成、显微组织、致密度及力学性能的影响。结果表明:烧结样品主要由Co-Ni、Ni Fe2O4、Ni O组成,部分Co与陶瓷基体反应生成CoO与Fe2O3。添加适量Co可以改善金属相在陶瓷相的分布和形貌,使团聚孤立的金属相分布均匀,且部分球状金属相变为长条状金属相;同时,添加适量Co还可以促进烧结,提高试样的致密度。适量Co的添加还能降低晶粒尺寸,大幅提高金属陶瓷材料强度与韧性。当Co质量分数为金属相的20%时,金属陶瓷的综合性能最好,致密度、抗弯强度、断裂韧性及硬度分别达到96.87%、163.65 MPa、8.38 MPa/m1/2和820.81HV。     

Yb2O3或Y2O3掺杂Cu-(NiFe2O4-10NiO)惰性阳极的导电性和耐蚀性

在氧分压约为100 Pa的氮气氛下烧结制备了掺杂Y2O3、Yb2O3的10Cu-(NiFe2O4-10NiO)金属陶瓷,并对其进行导电性能测试和10h(Na3A1F6-Al2O3体系中)铝电解实验.采用XRD、SEM和EDS分析稀土氧化物以及其与陶瓷基体反应产物的分布,考查电解实验后材料表层显微结构变化尤其是金属相的流失情况,评价稀土氧化物的添加对金属陶瓷电解初期腐蚀行为的影响.结果表明:掺杂稀土氧化物均使NiO相呈连通迹象,掺杂Yb2O3金属陶瓷晶粒较未掺杂的粗大,其与陶瓷相反应生成物成点线状分布于NiFe2O4相晶界,Y2O3与陶瓷相反应生成物则分布于NiO与NiFe2O4相间;所制备材料具有半导体特征,随着稀土氧化物的掺杂,材料导电性呈下降趋势;掺杂稀土氧化物尤其是Yb2O3有利于提高材料的耐蚀性能.     

铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极的耐腐蚀性能

制备铝电解用NiFe2O4-10NiO基金属陶瓷惰性阳极,并在实验室电解槽中考察其电解腐蚀性能。结果表明,电解过程中虽然惰性阳极在960°C熔盐电解质中表现出优异的耐腐蚀性能,但采用XRD、SEM/EDX和金相分析其物相组成和微观结构后发现,电解后阳极中的金属相发生了优先腐蚀,在阳极表面产生大量孔洞。NiFe2O4相中的 Fe 元素的优先溶解可能导致 NiFe2O4晶粒的不均匀腐蚀。溶解在电解液中的 Al2O3与阳极中的 NiO 或FeO 发生反应生成的 NiFe2O4-NiAl2O4-FeAl2O4相对 NiO 相的吞并以及体积膨胀,阳极表面形成致密的NiFe2O4-NiAl2O4-FeAl2O4保护层。因此,致密的NiFe2O4-NiAl2O4-FeAl2O4保护层可以阻挡阳极表面金属相的损失和陶瓷相的腐蚀。     

铝电解惰性阳极用Ni-Zn铁氧体的固态合成

采用固态合成法分别在惰性气氛和空气下，制备不同成分的Ni(l-x)ZnxFe2O4铁氧体尖晶石。对反应产物的物相、粒度和形貌的检测表明：在Ar气保护下煅烧主要发生氧化物的离解反应，反应物无法得到目标物相；采用反应烧结法制备铝电解金属陶瓷惰性阳极时，须保持一定的氧分压，以避免金属氧化物的离解和金属相的氧化；在空气中，通过固态反应可制备出理想的铝电解惰性阳极用Ni(l-x)ZnxFe2O4尖晶石，其粒度细，且符合标准正态分布，烧结温度低，在1150℃下保温6h即实现完全反应。     

Yb_2O_3掺杂对15(20Ni-Cu)/(NiFe_2O_4-10NiO)金属陶瓷性能的影响

采用冷压-烧结技术制备NiFe2O4-10NiO基金属陶瓷材料;通过对烧结体的显微结构和物相组成、电导率、电解试样的表层形貌、电解质和阴极铝的杂质增量等的分析检测,研究Yb2O3掺杂对15(20Ni-Cu)/NiFe2O4-10NiO金属陶瓷致密度、导电率和耐腐蚀性能的影响。结果表明:1 300℃烧结的0.5%Yb2O3-15(20Ni-Cu)/(NiFe2O4-10NiO)金属陶瓷具有较好的性能,相对密度为98.53%,960℃时的电导率为53.06 S/cm,电解腐蚀后金属腐蚀层厚度为20~30μm,总杂质增量为0.079 g。     

烧结气氛对5Ni/(10Ni-NiFe_2O_4)金属陶瓷物相组成及力学性能的影响(英文)

在不同烧结气氛下采用冷压烧结法制备5Ni/(10NiO-NiFe2O4)金属陶瓷,通过XRD研究其物相组成,SEM研究其显微结构,并用三点抗弯测试和抗热震实验检测其力学性能。结果表明:在真空气氛及氧含量分别为2×10-5、2×10-4和2×10-3的气氛中均可获得Ni/(10NiO-NiFe2O4)金属陶瓷,但气氛中氧含量对物相含量影响较大。在真空气氛中NiO含量相对较高。材料中NiFe2O4和Ni的含量分别随着气氛中氧含量的上升而增加和减小;在真空烧结气氛中,可获得晶粒尺寸为3.90μm的5Ni/(10NiO-NiFe2O4)金属陶瓷,其抗弯强度可达138.59MPa,且在960°C实验条件下平均抗热震循环次数可达6.67次,具有相对较好的力学性能。     

Development and characterisation of direct laser sintering Cu-based metal powder

Direct laser sintering of metal powder is a promising manufacturing process to produce rapid moulds (or rapid tooling) because complex three-dimensional (3-D) metal parts can be created directly from computer-aided design (CAD) data without machining or use of additional tooling. However, material and process are still the crucial issues that restrict its wider adoption although the technology has been introduced more than 7 years. This paper characterises a self-developed Cu-based metal powder used for direct laser sintering. The material system is Cu-based alloy metal powder, which consists of two metal powders: high-purity Cu powder and pre-alloyed SCuP metal powder. The scanning electron microscope (SEM), XRD and energy dispersive X-ray (EDX) analyses show that the bonding mechanism of this process is liquid-phase sintering. The pre-alloyed SCuP metal powder with lower melting point (645 °C) acts as the binder during laser sintering, while the Cu powder with higher melting point (1083 °C) acts as the structure. The element phosphorus in the powder can act as flux to protect the Cu oxidisation. A case study on fabricating the inserts of a mobile phone cover mould was also carried out. The inserts were created in ambient atmosphere at room temperature. The total sintering time is 40 h. Sixty five percent relative theoretical density and average surface roughness R_a 14–16 μm were achieved with negligible distortion and curling. Epoxy infiltration was employed as post-process to improve the density and the strength of the sintered tooling. The mould inserts were used to inject ABS-PC mobile phone cover after polishing. No defects were found after moulding of 500 components.     

Densification of Ni-NiFe_2O_4 cermets for aluminum electrolysis

1INTRODUCTION Aluminumelectrolysisconsumesenormous energyandresources,andtheconsumptionwillbeconsiderablydecreasedbyintroductionofinert anodeandwettablecathode.However,underthe toughworkingconditionofaluminumelectrolysis,i.e.highlycorrosiveNa3AlF6Al2O3moltensalts athightemperature(940960℃),theinert anodesnecessaryforthesuccessfulproductionofaluminummighthavethefollowingproperties:be insolubleinafluoridemelt,beresistanttowards anodeoxygen,havegoodelectricalconductivity,possessadequatestr…     

AlON粉体的合成

以α-Al_2O_3和AlN为原料,利用高温固相反应在氮气气氛下常压合成了AlON粉体.研究了成分配比、合成温度、保温时间对合成AlON粉体含量的影响,并通过热分析测试了合成过程热流和质量的变化.结果表明,当原料Al_2O_3和AlN的质量比为81:18、合成工艺为1750 ℃, 2 h时,得到AlON相的含量达到95%以上.     

La~(3+)掺杂Y_2O_3透明陶瓷制备及发光性能

以Y2O3为基质材料,掺杂不同含量的La3+,采用机械力化学法制备纳米粉,粉体压制后在真空度1×10-3Pa下烧结得到La3+掺杂Y2O3透明陶瓷。采用透射电子显微镜(TEM)观察粉体一次颗粒形貌,扫描电镜(SEM)观察样品表面形貌,HV-1000型维氏硬度计测定样品硬度和断裂韧性,阿基米德法测定烧结后试样的相对密度,自动记录分光光度计测定试样透过率。结果表明:制备的La3+∶Y2O透明陶瓷透光率可达80%,掺杂La3+可以显著降低La3+∶Y2O3透明陶瓷的烧结温度;随着La2O3添加量的提高,样品透光率逐渐提高,但La2O3添加量过大会造成点阵畸变严重;随着La2O3添加量的提高,样品相对密度、维氏硬度和断裂韧性均逐渐提高,最后趋于平稳;随着保温时间延长,样品透光率也逐渐增大,继续增大保温时间,透光率趋于平缓。结合样品的透光率、相对密度、维氏硬度和断裂韧性考虑可知La2O3适合掺杂量、烧结温度和保温时间分别为10at%、1550℃和3h。     

Effect of BaO addition on electric conductivity of xCu/10NiO-NiFe2O4 cermets

The effects of BaO addition on the phase composition, relative density and electric conductivity of xCu/10NiO-NiFe2O4 （x=5, 10） eermets were studied, which were prepared with cold isostatic pressing-sintering process. The results show that the relative densities of 5Cu/10NiO-NiFe2O4 cermet doped with 1% BaO （mass fraction） and 10Cu/10NiO-NiFe2O4 cermet doped with 1% BaO sintered at 1 473 K in nitrogen atmosphere, are increased by about 9.86% and 9.75% compared with the undoped BaO cermets, respectively. And the electric conductivities 22.79 S/cm of 5Cu/10NiO-NiFe2O4 cermets adding 1% BaO and 23.10 S/cm of 10Cu/10NiO-NiFe2O4 cermets adding 1% BaO are obtained, which are 2.21 times and 1.47 times of those of undoped samples, respectively. Moreover, the 10Cu/10NiO-NiFe2O4 cermets doped with 1% BaO have a maximum σ0 of 58.91 S/cm and electric conductivity of 23.10 S/cm at 1 233 K. Maybe low melting-point phases of BaFe2O4 and Ba2Fe2O5 have an excellent electric conductivity in xCu/10NiO-NiFe2O4 （x=5, 10） cermets at 1 233 K.     

NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>-based cermet inert anodes for aluminum electrolysis

Recent developments in the preparation, sintering process, mechanical properties, and thermal shock resistance of cermet inert anodes for aluminum electrolysis are reviewed in this paper. To obtain the desired technologies of low-temperature activated sintering of cermet inert anodes, the effects of material composition, sintering atmosphere, sintering temperature, and sintering aids on the densifi cation and microstructure of NiFe₂O₄-10NiO- based ceramics and cermets were studied. To obtain the toughening and strengthening technology of the cermet, the effects of material composition including ceramic and metallic phases are discussed. The cermet inert anodes with high density and mechanical properties were prepared through adjustment of material composition and sintering technology and selection of feasible sintering aids.     

烧结温度对Micro-FAST制备钛微型齿轮致密化的影响

将新颖的多物理场活化烧结微成形技术(Micro-FAST)引入到钛微型齿轮的制备中,研究了烧结温度对Micro-FAST制备钛微型齿轮致密化的影响。结果表明,在1200℃烧结保温4 min,体系的相对密度即可达到90.5%。Micro-FAST的烧结致密化过程大致可分为4个阶段:预热阶段、低温保温阶段、快速升温阶段和烧结保温阶段,钛粉末的致密化过程主要发生在快速升温阶段。对烧结体系的收缩动力学曲线研究发现,在电场、力场和温度场的耦合作用下,粉末体系在450℃发生了塑性变形,在1032℃生成了局部液相。研究表明,与传统烧结法相比,多物理场活化烧结法是一种新型和高效的制备钛微型零件的良好方法。     

Preparation and preliminary testing of cermet inert anode for aluminum electrolysis

1　INTRODUCTIONAluminumhasthelargest productivityamongthenonferrousmetals ,2 4Mtperyearintheworld .Whilegreatprogresshavebeenmadeintheprimaryaluminum production ,theindustrycontinuestopur sueresearchtosolvesomeformidablechallenges ,suchas quitealargeenergyintensity(14 0 0 0 15 0 0 0kW·hpertonaluminum) ,highcon sumptionofcarbonanode(5 0 0 6 0 0kgpertonalu minum) ,significantemissionsofgreenhousegas(1.71tpertonaluminum )andotherdetrimentalgases ,highcapitalinvestmentandcost[1] .Inertelectr…     

Effects of sintering processes on the mechanical properties and microstructure of Ti(C,N)-based cermet cutting tool materials

In this study, two types of Ti(C_0.7,N_0.3)-based cermet cutting tool materials (Ti(C,N)–Mo–Ni–Co, named as TMNC, and Ti(C,N)–WC–Mo–Ni–Co–TaC–HfC, named as TWMNCTH) were fabricated by the hot pressed sintering process at different temperatures (from 1380 °C to 1500 °C) for different holding times (from 30 min to 60 min) in a vacuum atmosphere and at a compressive stress of 32 MPa. The polished surface and the fracture surface of the two types of cermets were observed by a scanning electron microscope (BSE/SEM) and energy dispersive spectrometry (EDS), and the relationships among sintering processes, mechanical properties and microstructure were discussed. The experimental results showed that the sintering temperature and holding time both had a great influence on the flexural strength and a small effect on the hardness and the fracture toughness of the two types of cermets. The two cermets both had the optimal comprehensive mechanical properties when they were sintered at 1400 °C for 30 min. The sintering temperature and holding time also had a great influence on the microstructure of the two cermets, and the grain sizes increased when the sintering temperature varied from 1400 °C to 1500 °C and the holding time varied from 30 min to 60 min. The properties and microstructure of the two cermets were also compared. The results indicated that the cermet TWMNCTH had a lower flexural strength, a similar value of fracture toughness, a higher hardness and a thicker rim in the microstructure.