熔融碳酸盐燃料电池电极用镍粉浆料的流变学研究

流延成型法是目前制备熔融碳酸盐燃料电池电极板的主要工艺。本文以环己酮 丁醇为溶剂 ,三油酸甘油酯为分散剂 ,以聚乙烯醇缩丁醛为粘结剂 ,聚乙烯乙二醇为增塑剂 ,通过球磨工艺制备了非水基羰基镍粉浆料。详细研究了分散剂用量 ,粘结剂 分散剂用量及其比例对镍粉浆料流变学性能的影响 ,并将浆料流延成型 ,研究了素坯的密度、力学性能和微观结构与浆料流变学行为的相关性     

Tape casting aqueous alumina suspensions containing a latex binder

The tape casting of ceramic membrane substrates of 1 mm thickness has been studied using two grades of ammonium polymethylacrylate (PMA) as a dispersing agent, dibutylphthalate as a plasticizer and polyvinylacetate (PVAc) latex as a binder. The colloidal stability of the alumina particles in the precursor slip was characterized using zeta potential measurements and the rheological behaviour of the slips. After tape casting, the density, strength and flexibility of the green tapes were studied in terms of changes in the plasticizer concentration and pH of the slip. The results indicated that alumina particles could be stabilized at pH 6–10 at a PMA15 concentration of 10 mg g^–1. The slips prepared with the polyelectroyte also displayed a strong shear thinning effect, which is important for tape casting. With the proper addition of plasticizer and adjustment of pH, it was found that a PVAc latex-based system can yield green alumina tapes with high green strength and flexibility.     

Aqueous tape casting of yttria stabilized zirconia

Tape casting process was used to produce yttria stabilized zirconia (YSZ) substrates in an aqueous system with poly(vinylalcohol) (PVA) and glycerine as binder and plasticizer, respectively. Various compositions of YSZ slips with different amounts of PVA and glycerine and consequently different solid/liquid ratios were prepared. The influence of the slip composition on the rheological properties of the slips was studied. In addition, the effect of the slip composition on the properties of the green and sintered tapes was investigated. PVA and glycerine did not affect the dispersion properties of the YSZ powder. Glycerine additions enhanced the flexibility of the green tapes but also produced a decrease in the tensile strength. The increase in the PVA content increased the tensile strength but resulted in a markedly decrease in the green density of the tapes. A correlation between the green and sintered density was found. The anisotropic sintering shrinkage parallel and perpendicular to the casting direction increased with increasing the PVA content. The slip compositions with 5 wt% PVA produced green tapes with satisfactory tensile strength. They had the highest sintered density, the lower sintering shrinkage and the lesser shrinkage anisotropy.     

Preparation of porous nickel electrodes for molten carbonate fuel cells by non-aqueous tape casting

The casting behaviour, ultimate tensile strength and the sintering process of tapes consisting of nickel powder, ethanol, po!yvinylbutyral as the binder, polyethylene glycol (molecular weight 200, PEG2) or dibutyl phthalate (DBP) as the plasticizer, and glycerol trioleate as the dispersant agent, were studied. On increasing powder content in the slurry the packing factor of nickel in the green increased, but the ultimate tensile stress and strain to failure decreased. Increasing binder to total binder ratio caused the green density and strain to failure to decrease, but the ultimate tensile stress increased for both PEG2 and DBP. The maximum strain to failure (about 35% for both PEG2 and DBP) in the case of DBP was obtained with an amount of plasticizer lower than that of PEG2. When tapes having different composition were sintered at various temperatures, a linear relation was found between packing factor and fired density, independently of the kind of binder and plasticizer used.     

氧化锆粉末特性和有机添加剂对流延法制膜的影响

用四种不同粒径的、全稳定的ZrO2粉料进行了燃料电池电解质厚膜的流延实验．结果表明，流延成膜的最佳料浆组成随粉料粒径有很大变化，随着粉料粒径的减少；所需要的分散剂用量相应增加，同时；所需要的粘结剂与塑性剂用量也必须增加，以确保素坯膜有足够的强度与韧性．此外，料浆粘度对成膜的影响也很大，在所研究的料浆系统中，为了得到好的素坯膜，适中的料浆粘度应控制在400～600mpas（剪切速率为350s-1）范围以内．     

Modification of tape casting slurry via effective plasticization by butyl benzyl phthalate of CaO–SiO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass–ceramics

This present work aimed to attain a high-performance tape for LTCC application by using butyl benzyl phthalate as plasticizer in tape casting slurry of CaO–SiO₂–B₂O₃ glass–ceramics. The plasticizing mechanism of butyl benzyl phthalate in suspensions was demonstrated in depth. Dried droplets of binder were prepared to preliminarily judge the compatibility of binder and plasticizer, and the optimal additive amount was determined by rheological characteristic. In addition, a series of qualitative and quantitative methods were carried out to assess the tensile strength and elongation of green tapes, microwave properties and densification of sintered bodies. The experimental results revealed that when the addition of BBP was up to 45 wt%, tape casting slurries had the optimal fluidity and green tapes obtained the excellent performance with density at 1.65 g/cm³, tensile strength at 1.43 MPa and elongation at 13.4%. Meanwhile, sintered bodies fired at 850 °C achieved the highest density at 2.42 g/cm³ with ε_r?=?5.94 and tanδ?=?10?×?10^?4 at 10 GHz.     

Tape casting of AlN/glass composites for LTCC substrate

AlN/glass composite is low-fired substrate material for microelectronic packaging material. In this work, AlN/glass sheets were prepared by tape casting process. The dispersion, stabilization and the rheological properties of the slurry were studied. The optimum drying condition and mechanisms of debinding were also investigated. The results showed that powder size influenced the optimum content of dispersant and the viscosity of slurry. The slurry for tape casting exhibited a typical shear-thinning behavior. Smooth green tape without cracking was acquired after it was dried at solvent atmosphere. The binder was fully burned out at 600°C at low heating speed. The lamination with uniform microstructure was achieved by hot-pressed at 900°C.     

Dispersion and tape casting of silicon carbide through aqueous route

Dispersion behaviour of SiC in aqueous media was studied using four different dispersants and as a function of pH. The slurry was characterized in each case by sedimentation, viscosity and rheological studies. The best dispersant was selected and its optimum amount was determined. For this system, the pH was varied over a range of 2–11. The slurry displayed the minimum viscosity as well as near-Newtonian behavior at pH range 8–11. SiC tapes were obtained by Double doctor blade tape-casting process, with polyvinyl alcohol as binder and PEG and BBP as plastisizers. The stability of the tape casting slurry was determined by rheological characteristics. As-cast tapes were dried in air at room temperature. The results show that it is possible to obtain homogenous defect-free green tapes of 57.7% solid loading and 53% green density with smooth surface using the optimized tape casting slurry.     

Effect of the molecular weight of poly(ethylene glycol) on the plasticization of green sheets composed of ultrafine BaTiO3 particles and poly(vinyl butyral)

The effect of the molecular weight (MW) of poly(ethylene glycol) (PEG) on the plasticization of poly(vinyl butyral) (PVB) binder in green BaTiO₃ sheets prepared with PEG with MW values of 400 and 1530 was investigated. The MW of PEG had a profound effect on the rheological properties of the suspension as well as the physical properties of the green sheet. The suspension viscosity decreased with decreasing MW of PEG for shear rates above 4 s⁻¹. PEG 400 gave rise to a higher degree of plasticization of the green sheet than PEG 1530. This was due to the reduction in hydrogen bonding between the vinyl alcohol units in the PVB binder in the green BaTiO₃ sheet, as identified by FT-IR spectroscopy. As the MW of the PEG decreased, the green BaTiO₃ sheets exhibited a lower glass transition temperature, and a noticeably more ductile behavior. These results indicate that the green sheets became more flexible due to a higher plasticizing effect. However, laminated green BaTiO₃ sheets prepared with PEG 1530 showed delamination defects that were observed at a cut surface, which arose because of the low plasticization. This suggests that PEG 1530 has limited utilization as a plasticizer for the BaTiO₃/PVB binder system.     

Dispersion and rheological studies of Y-PSZ tape casting slurry

Different solvent systems in combination with three different dispersants were tried to find out the suitable solvent-dispersant combination, which give optimum dispersion of PSZ. Based on sedimentation, viscosity and rheology characteristics, zeotropic ethanol : xylene with a ratio of 50 : 50 along with 0.5 wt% phosphate ester was found to be the best solvent and dispersant combination. Optimized tape casting slurry was prepared using PEG 600 and BBP as plasticizers and PVB as the binder. Cyclohexanone was used as the homogenizer. The optimized slurry composition with 58% solid loading exhibited shear-thinning pseudoplastic rheological behaviour. Y-PSZ tapes of ∼ 50 Μm thickness free from visible defects were cast with a green tape density of 55%.     

Application of alginate gelation to aqueous tape casting technology

This work deals with a novel forming process for manufacturing ceramic tapes in an aqueous medium, that combines tape casting and gel-casting technologies. Aqueous tape casting suspensions of Al₂O₃ are prepared to a solid loading of 57 vol.% (84 wt.%) by adding 15 wt.% of a binder system consisting of acrylic emulsions and a small concentration (≤0.5 wt.%) of alginate. The as-cast tape is immersed in a CaCl₂ solution and the alginate undergoes gelation. This allows releasing of the tape from the carrier film so that no sticking occurs and crack formation is avoided. Sintered densities are ∼97% of theoretical, similar to those obtained by conventional aqueous tape casting.     

Study of cracking and microstructural evolution during drying of tape-cast aluminium nitride sheets

The influence of organic phases on the drying of tape-cast aluminium nitride green sheets was studied. The cracking during drying and the microstructure of green tapes are sensitive to the inorganic to organic and binder to plasticizer ratios. A high amount of a plasticizer-rich organic phase promotes a low-speed shrinkage of the green tape during drying and prevents it from cracking. The apparent density and the porosity of the green tapes decrease whereas the total shrinkage of the green tapes increases when the organic content increases. The apparent density increases whereas the porosity and the shrinkage decrease when the plasticizer content increases.     

流延法制备SOFC阳极支撑体基片

系统地研究了流延法制备SOFC阳极支撑体基片过程中影响流延浆料粘度和素坯质量的主要因素, 分析了球磨时间、有机混合溶剂类型、分散剂添加量、增塑剂/粘结剂比例(R)等参数以及除泡工艺对浆料流变性能的影响. 研究发现: 混合溶剂乙醇/二甲苯(体积比1:1)对粉料的湿润性能最好, 粉体的悬浮性能和浆料流变性能最佳; 分散剂添加量为1.8wt%时, 浆料的粘度最低; 研磨时间为24h制备的浆料流变性接近最佳状态; 浆料的粘度随R值的增大而急剧减小, 当R为1时粘度达到最佳值, 流变性能得到明显改善; 少量的除泡剂和真空搅拌对消除浆料制备过程中所产生的气泡极为有效.     

Cold laser machining of nickel-yttrium stabilised zirconia cermets: Composition dependence

Cold laser micromachining efficiency in nickel-yttrium stabilised zirconia cermets was studied as a function of cermet composition. Nickel oxide-yttrium stabilised zirconia ceramic plates obtained via tape casting technique were machined using 8-25 ns pulses of a Nd: YAG laser at the fixed wavelength of 1.064 μm and a frequency of 1 kHz. The morphology of the holes, etched volume, drill diameter, shape and depth were evaluated as a function of the processing parameters such as pulse irradiance and of the initial composition. The laser drilling mechanism was evaluated in terms of laser-material interaction parameters such as beam absorptivity, material spallation and the impact on the overall process discussed. By varying the nickel oxide content of the composite the optical absorption (-value is greatly modified and significantly affected the drilling efficiency of the green state ceramic substrates and the morphology of the holes. Higher depth values and improved drilled volume upto 0.2 mm³ per pulse were obtained for substrates with higher optical transparency (lower optical absorption value). In addition, a laser beam self-focussing effect is observed for the compositions with less nickel oxide content. Holes with average diameter from 60 μm to 110 μm and upto 1 mm in depth were drilled with a high rate of 40 ms per hole while the final microstructure of the cermet obtained by reduction of the nickel oxide-yttrium stabilised zirconia composites remained unchanged.     

添加BCB助烧剂的CLST陶瓷流延浆料流变性能研究

研究了有机物对CLST陶瓷流延浆料性能的影响.结果表明:体积比为1∶3的乙醇与氮-氮二甲基甲酰胺为混合溶剂对粉料的湿润性能最好,以聚乙烯醇缩丁醛( PVB)为粘结剂,邻苯二甲酸二丁酯为增塑剂,蓖麻油为分散剂配制了CLST陶瓷流延浆料.当w(分散剂)为0.8％,w(粘结剂)为8％,固相体积分数为50％,R(增塑剂:粘结剂...     

Ba2Ti9O20陶瓷流延浆料的流变性能和流延成型研究

以BaCO3和TiO2粉末为原料,采用固相反应法合成Ba2Ti9O20的粉体,并以此粉体为主要原料添加适量的分散剂、粘结剂及塑性剂,采用流延法制备Ba2Ti9O20陶瓷膜片。研究了不同种类和配比的溶剂、不同种类和含量的分散剂对Ba2Ti9O20流延浆料的流变特性的影响。结果表明,当选用异丙醇和甲苯(体积比为75:25)为溶剂,固含量Ba2Ti9O2054wt%,分散剂蓖麻油0.5wt%,粘结剂聚乙烯醇缩丁醛5wt%,塑性剂聚乙二醇5wt%时,流延浆料的流变性能较好,浆料的粘度为9.1Pa.s。     

Tape casting and dielectric properties of SiO2-filled glass composite ceramic with an ultra-low sintering temperature

The tape casting and the dielectric properties of the suitability of dielectric ceramics made of silicon dioxide-filled zinc borate glass with an ultra-low sintering temperature (650 °C) were investigated. The effects of the dispersion, the binder and the plasticizer amounts on the slurry were found to obtain an optimum composition for tape casting. The sintering temperature dependence on dielectric properties of the tape was reported. In addition, electrodes on a multilayer module made on laminated tapes were prepared using Ag paste and post-firing, followed by scanning electronic microscope to verify the chemical compatibility under the co-firing process. The results show that the composition is well suitable for the tape process for low temperature co-fired ceramic technology.     

A novel method to regulate the density of BaTiO3 ceramics for positive temperature coefficient resistance via tape casting

BaTiO₃ ceramics for positive temperature coefficient resistance (PTCR) were fabricated via tape casting technique and reduction/reoxidation process. A novel method was used to regulate the density of the ceramics via changing binder amount in tape casting green bodies. The influences of different amounts of the binder on density, electrical properties, and microstructure of ceramics were investigated. The BaTiO₃ ceramic monolith without internal electrodes with an addition of binder of 0.84 wt% was sintered in reducing atmosphere at 1150 °C and reoxidized at 800 °C for 1 h showed a resistivity of 56 Ω·cm and a PTCR jump about 3.2 orders of magnitude. The green and sintered density of the samples decreased with the increasing binder amount. The room temperature resistivity increased monotonically with the binder amount. However, the correlation of the PTCR jump with binder amount showed a contrary tendency. These electrical properties can be explained by the Jonker model. The influences of sintering temperature on the density of BaTiO₃ ceramics with different binder amount were also discussed. In addition to the ceramic monoliths without internal electrodes, multilayer elements with internal electrodes were also prepared.     

Silica moulds built by stereolithography

In this work the production of ceramic moulds for aluminium casting using a stereolithographic apparatus is presented. Suspensions of silica powders in a photoreactive resin were used in standard STL equipment in order to build green parts. UV curable pre-ceramic suspensions have been studied using photocalorimetric and rheological characterizations. Thermogravimetry was used to analyse the behaviour of the pre-ceramic green during thermal treatment. Stereolithgraphy apparatus (SLA) was modified in order to fabricate ceramic green. Silica objects were obtained by pyrolysis of the organic binder and subsequent sintering at high temperature. A characterization of mechanical properties of the green and sintered ceramic materials was performed. Finally moulds for investment casting of aluminium were built by stereolithography and used for casting as a green as well as after sintering.     

Properties of tape-cast Y-substituted strontium titanate for planar anode substrates in SOFC applications

This work evaluates the use of fine-grained yttrium-substituted strontium titanate powders for the preparation of planar anode supported solid oxide fuel cells. Starting from a submicron-sized powder of Y-substituted strontium titanate Sr_0.895Y_0.07TiO₃ (SYT), which was synthesised via spray pyrolysis followed by a grinding process, suspensions of high solid concentration were prepared by steric stabilisation. From these suspensions, tape casting slurries of up to 25 vol% were produced and further processed to ceramic green tapes using the doctor blade technique. The rheological behaviour of the slurries was investigated in dependence on the content of solids and organic additives. Furthermore, the binder burnout and sintering behaviour of the green sheets were characterised. After firing, crack-free substrates of high planarity were obtained. The achieved properties of the sintered tapes such as density, porosity, warping, mechanical strength, and electrical conductivity were determined in dependence on sintering temperature.