先进陶瓷快速无模成型技术的研究与进展

系统综述了先进陶瓷快速无模成型技术及其最新研究进展,其中主要包括熔融沉积成型技术、喷墨打印成型技术、三维打印成型技术、分层实体成型技术、激光选区烧结成型以及立体光刻成型技术。最后论述了陶瓷快速无模成型技术所具有的独特优势和当前研究工作中面临的问题和挑战。     

高性能陶瓷成型工艺进展

本文论述了高性能陶瓷成型工艺的和重要性，重点介绍了陶瓷胶态成型工艺的研究进展及陶瓷成型工艺的最新动向，提出了瓷成型工艺研究中必须重视和加强的若干研究领域。     

陶瓷成型方法研究进展

成型技术是制备陶瓷材料的一个重要环节。本文简单回顾了陶瓷成型方法的发展历程,着重综述了９０年代产生的几种新的成型技术,最后展望了陶瓷成型方法的发展趋势。     

陶瓷成型技术的新进展

提高成型技术是提高陶瓷产品可靠性的关键步骤。本文介绍了陶瓷胶态成型技术方面的最新发展情况，并对它们的应用情况做了简要的分析。     

复杂陶瓷卫生洁具新产品开发的数字化方法——无模砂型快速制造

本文介绍了应用无模砂型快速制造技术开发复杂陶瓷卫生洁具新产品的方法,该技术具有生产周期短、效率高、成本低等特点,为复杂陶瓷卫生洁具的产品开发提供了一个崭新的方向。     

陶瓷材料成型工艺研究新进展

陶瓷制造经历数千年历史，当前阻碍陶瓷材料进一步发展的关键之一是成型工艺技术没有突破。本文介绍了胶态成型，固体无模成型工艺及气态成型，对上述工艺的原理、工艺过程及特点进行比较，提出了陶瓷成型工艺的关键问题。并介绍了水基非塑性浆料的注射成型新工艺。     

计算机辅助无模成型陶瓷部件坯体的工艺

本专利涉及陶瓷材料制造技术。其特征在于首先将海藻酸钠制备成水溶液,然后加入陶瓷粉料和分散剂混合球磨,球磨后的陶瓷浆料室温下除泡。将浆料以一定的厚度铺展在成型工作平台上,在计算机指令下按照部件的CAD模型有选择地在浆料上喷上凝胶剂,引发浆料局部凝胶,然后在已经凝胶的浆料层上通过刮刀再铺上一层新的浆料。不断重复上述过程,直到整个陶瓷部件坯体建造完成。陶瓷坯体经过清洗、干燥后,烧结得到成品。利用本发明工艺成型的陶瓷部件不需要模具,自动化程度高,尺寸准确,工艺周期短,坯体有机物含量低,密度高,内部均匀性好,采用的原料…     

陶瓷材料成型工艺研究新进展

陶瓷制造经历数千年历史,当前阻碍陶瓷材料进一步发展的关键之一是成型工艺技术没有突破。本文介绍了固体无模成型工艺及气态成型,并对上述工艺的原理、工艺过程及特点进行比较,提出了陶瓷成型工艺的关键问题。并介绍了水基非塑性浆料的注射成型新工艺。     

高压陶瓷电容器凝胶注模成型研究

凝胶注模成型是九十年代初发明的一种新型成型技术.它是传统陶瓷工艺和高分子化学结合的产物.这种方法具有素坯密度高、密度均匀、强度大,可成型复杂形状近净尺寸的大型陶瓷制品等特点,应用前景十分广阔.本文报告了高压陶瓷电容器凝胶注模成型研究结果.     

高温合金精密铸造用陶瓷型芯成型技术研究进展

介绍了高温合金在航空发动机部件中的重要地位,以及高温合金熔模铸造用陶瓷型芯的应用背景,概述了陶瓷型芯成型技术的研究现状和重要意义。系统综述了先进陶瓷型芯成型技术的发展历史、特点及其最新研究进展,其中包括注射冷冻成型技术、无模成型技术、负复型技术以及充芯材料灌浆成型技术。重点介绍了立体光刻成型和三维打印成型等无模成型技术,并分析了目前无模成型技术所具有的独特优势和当前产业化所面临的问题与挑战。     

Pressureless fabrication of dense monolithic SiC ceramics from a polycarbosilane

This paper presents the pressureless preparation of dense and crack-free near stoichiometric SiC monoliths via cross-linking and pyrolysis of a polycarbosilane, followed by polymer-infiltration-pyrolysis cycles. The composition and the porosity of the samples strongly depend on the processing temperature. Thus, at 1050–1100 °C, the SiC monoliths are X-ray amorphous and exhibit low amounts of oxygen and excess carbon; their porosity was rather high (>10%). Higher processing temperatures induced the crystallization of β-SiC. The removal of oxygen and excess carbon due to CO release allowed for obtaining near-stoichiometric compositions at 1700 °C. However, the residual porosity of the samples increased. The use of the PIP technique led already after six cycles to dense monoliths (residual porosity ca. 0.5%).The present study emphasizes the potential of the polymer processing technique for the fabrication of near stoichiometric and dense SiC monoliths, which might be used for structural applications in harsh conditions.     

The fabrication of porous mullite ceramics based on the different sizes of aluminum hydroxide

In this research, for studying the influence of size and heat treatment temperature of initial Al(OH)₃ on the physical properties of porous mullite ceramics, porous mullite ceramics were prepared by in situ reaction sintering of amorphous silica and treated Al(OH)₃. The transition phases χ-Al₂O₃, к-Al₂O₃, and stable phase α-Al₂O₃ can be obtained in turn when the treatment temperature of raw Al(OH)₃ is 500, 1000, and 1500°C, respectively. The coarser the raw Al(OH)₃, the higher the strength of porous mullite ceramics. When the sintering temperature is 1500°C, the bending strengths of PS500-C, PS1000-C, and PS1500-C (PSx-C represents that the specimen was prepared by the coarse grade Al(OH)_3, which was previously treated at x°C) are 40.3 ± 2.1, 54.9 ± 5.2, and 64.8 ± 4.8 MPa, respectively. In addition, although the activated Al₂O₃ can decrease the formation temperature (∼100°C) of porous mullite ceramics, the strength and density of porous mullite ceramics prepared by activated Al₂O₃ will decrease at the same sintering temperature. It is believed that the increase of defects and pores during the phase transformation should be responsible for this phenomenon.     

Effects of fiber aspect ratio and fabrication temperature on the microstructure and mechanical properties of elastic fibrous porous ceramics by press-filtration method

The inherent brittleness of fibrous porous ceramics (FPCs) results in their fragility, limiting their application in thermal protection. In this paper, a novel elastic fibrous porous ceramic (EFPCs) with quasi-layered structure were successfully prepared by facile press-filtration method. To further investigate the characteristics of EFPCs, the effect of fiber aspect ratio and fabrication temperature on the microstructures and properties were studied. Results demonstrated that both fiber aspect ratio and fabrication temperature had influence on the microstructure and mechanical properties on EFPCs. The prepared EFPCs exhibited low density (0.124–0.181 g cm^?3), relatively high compressive stress (0.096–0.377 MPa) compared to flexible fibrous ceramics, high porosity (91.73%–94.86%) and low thermal conductivity (～0.03 W m^?1 k^?1). According to these excellent properties, the EFPCs may have potential use in thermal insulation fields.     

Three-parameter (3P) weibull distribution for characterization of strength of ceramics showing R-Curve behavior

Strength distribution of advanced ceramics is commonly characterized by two-Parameter (2P) Weibull distribution. However, deviation of strength distribution from 2P-Weibull distribution may occur in ceramics due to various mechanisms. R-curve behavior is one of these mechanisms where increase of fracture resistance with the extension of crack occurs. In such cases, 2P-Weibull distribution may not be the best fitting distribution function based on the goodness-of-fitness tests. This article examines the effectiveness of three-parameter (3P) Weibull distribution function for fitting the strength variation due to R-curve effect by using experimental and virtual strength data. The effect of Weibull parameters, degree of increase in crack resistance and number of samples on effectiveness of fitting via 3P-Weibull distribution is investigated. It is reported that 3P-Weibull distribution function fits the strength distribution better than 2P-Weibull distribution function for materials showing R-curve behavior when the crack resistance curve is steep and Weibull modulus is high. Furthermore, it is shown that at least 100 samples should be used for a reliable estimate when the material exhibits R-curve behavior.     

Synthesis of platelike CaTiO3 particles by a topochemical microcrystal conversion method and fabrication of textured microwave dielectric ceramics

Platelike CaTiO₃ particles with an orthorhombic perovskite structure have been synthesized by topochemical microcrystal conversion (TMC) from platelike precursor particles of the layer-structured CaBi₄Ti₄O₁₅ at 950 °C. The CaTiO₃ particles inherited and retained the shape of the precursor particles with a thickness of approximately 0.3 μm, and a width of 2–6 μm. XRD analysis showed that in the TMC reaction, the crystallographic {0 0 1} plane of CaBi₄Ti₄O₁₅ is converted into the {1 0 0} plane of CaTiO₃. Using the platelike CaTiO₃ particles as templates in the templated grain growth method, dense {1 0 0} grain-oriented CaTiO₃ ceramics having a {1 0 0} orientation could be fabricated at sintering temperatures between 1350 and 1500 °C. The maximum orientation factor reached 99.7% at 10% of template. It was found that texturing improves microwave dielectric low-loss properties, providing a 1.55 times higher Q_f value of 9310 GHz in textured ceramics compared to that of 6005 GHz in non-textured ceramics.     

Spark plasma sintering of SiAlON ceramics

Investigated was the spark plasma sintering (SPS) of sialon ceramics from SHS-produced powders. Experimentally established were (a) sintering temperatures that ensure a required density, phase composition, and microstructure of sintered multicomponent sialon ceramics, (b) individual stages of the SPS process, and (c) the effect of starting powder composition on the phase composition and microstructure of sintered sialon ceramics.      

Fabrication of hierarchical lattice structures from zirconia stabilized ceramics by micro-SLA 3D printing approach

The need for the new materials and advanced manufacturing techniques for achieving the highest characteristics of energy devices is an obvious trend. One of the possible ways to create structures for energy applications is to introduce complex geometries and promising features with additive manufacturing (AM). Using this approach, it is possible to create complex geometry and moreover decrease the weight of materials. In this paper, we developed the layer-by-layer fabrication approach of ceramic hierarchical lattice structures via the (micro-SLA) technology. As a feedstock material, the novel composition of partly stabilized-zirconia ceramics (6ScSZ, 8YSZ) was developed. Materials were selected as a solid slurry component due to high ionic conductivity at the working temperature of modern solid oxide fuel cells (SOFCs). For the sintering, the green body heat treatment process was optimized to one step, which decrease the time and production cost. The data from scanning electron microscopy and micro-CT shows that 112-layer samples of the octet truss did not show any critical defects, and the achieved relative density was close to the theoretical one. Totally, 22 samples with the total size of 6.5 mm * 6.5 mm * 2.8 mm and the diameter of struts in the range of 240–250 μm were fabricated at a rate of only 56 min per sample, using two modifications of advanced doped zirconia-ceramics. This study opens new opportunities for the development and transfer to the production of additive manufacturing of ceramics to build energy systems devices such as solid oxide fuel cells.     

Pressureless synthesis of fully dense and crack-free SiOC bulk ceramics via photo-crosslinking and pyrolysis of a polysiloxane

This paper presents the pressureless preparation of fully dense and crack-free SiOC ceramics via direct photo-crosslinking and pyrolysis of a polysiloxane. Elemental analysis revealed the presence of high levels of carbon in the SiOC ceramics. Thus, the samples showed the highest content (78-86 mol%) of segregated “free” carbon reported so far. XRD investigations indicated that the materials prepared at 1100 °C were X-ray amorphous, whereas the sample prepared at 1400 °C contained a turbostratic graphite-like phase and silicon carbide as crystalline phases, as additionally confirmed by TEM and Raman spectroscopy. Vickers hardness was measured to be 5.5-8.6 GPa. The dc resistivity of the prepared material at 1100 °C was 0.35 Ω m, whereas the ceramic pyrolyzed at 1400 °C showed a value of 0.14 Ω m; both values are much lower than those of other known SiOC materials. This latter feature was attributed to the presence of a percolating carbon network in the ceramic.     

Electric field assisted solid-state interfacial joining of TaC-HfC ceramics without filler

The application of ultra-high-temperature ceramics (UHTCs) demands effective ways of joining in overcoming the problems associated with the fabrication of complex-shaped components. In this study, we choose to investigate a new method of rapidly joining pre-sintered TaC and HfC ceramics without any filler material using the spark plasma sintering (SPS) technique. A well-bonded TaC–HfC interface was observed with no apparent cracking and porosity at the joint. The joining mechanisms were predominantly driven by solid-state diffusion and localized plastic deformation. The nanomechanical properties of the TaC-HfC joint are better than the HfC while comparable to that of the TaC. High-load indentation (up to 200 N) results suggest that the TaC–HfC interface is stronger than the parent UHTCs with no crack propagating at the interface. Upon comparison with the parent UHTCs, the damaged area and the average crack length at the interface, reduced up to ~94% and ~56%, respectively. This study shows that the SPS technique can also apply to joining other UHTCs without any filler, resulting in the new field of developing complex components for the thermal protection system (TPS).     

Microstructure and broadband dielectric properties of Zn2SiO4 ceramics with nano-sized TiO2 addition

Zn₂SiO₄ ceramics with nano-sized TiO₂ addition (ZST) were synthesized by conventional solid state method. The association between the new composite's microstructures and dielectric properties reveals that reduced pores, increased density and average grain sizes with increasing sintering temperatures, have contributed to the increased permittivities at kHz and microwave bands; the decrease of the permittivities at 1275 °C is due to the form of twin planes. At the terahertz band, the competition of generating oxygen vacancies and forming them into twin crystallographic shear planes dominates the change of permittivities: the crystallographic shear planes decrease the permittivity at the sintering temperature 1225 °C and 1250 °C, and the high-rate generation of oxygen vacancies at 1275 °C increases the permittivities. The ZST ceramics demonstrate stable permittivity and low dielectric losses (<10^–3 from 10 kHz to microwave band; and <10^–2 at THz range); and the temperature coefficient of resonant frequency is optimized to close zero. These advanced dielectric properties and low sintering temperature (<1300 °C) provide the ZST ceramics great potential in designing microwave and THz devices.