复合烧结剂对高铝质干式料烧结性能的影响

以粒度3～5mm,1～3mm,≤1mm,≤0.088mm的高铝矾土为主要原料,以粒度≤0.1mm的硼酸(H3BO3>99.6%)、粒度≤0.05mm的粘土、粒度≤0.1mm的钾长石和粒度≤0.1μm的硅灰(SiO2>90%)为复合烧结剂,按m(骨料)∶m(细粉)=65∶35的配比配料。将混合料在陶瓷模具中手工捣打成型,将成型好的试样分别在600℃、700℃、800℃、900℃和1000℃下均保温2h后脱模。测量热处理后各试样的耐压强度和显气孔率;采用XRD分析了试样的物相组成。结果表明:复合烧结剂中钾长石和硼酸在中温、低温下具有良好的烧结作用,在700～800℃热处理后,试样耐压强度和显气孔率明显增加。硼酸含量为2%的试样,在800～1000℃热处理后,显气孔率增幅较大。添加硅灰可以降低钾长石烧结温度;而复合烧结剂中的粘土在中温、低温下不利于干式料的烧结,低于800℃热处理后的试样,耐压强度和显气孔率没有随粘土含量增加而变化;900～1000℃热处理后的试样,耐压强度随粘土含量的增加而降低,显气孔率增加不大。     

Synthesis of a foam ceramic based on ceramic tile polishing waste using SiC as foaming agent

Due to the large amount of ceramic tile polishing waste generated in China, the recycling of this waste residue becomes important. Herein a foam ceramic was successfully produced by using ceramic tile polishing waste as main raw material. In this research, SiC was added as the foam agent, and the foaming mechanism was also investigated. The results showed that the best dosage of SiC was 1%. Furthermore, in order to obtain a foam ceramic with better structure, the sodium phosphate was added in raw materials as foam stabilizer. The influence of this addition on the microstructure and properties of foam ceramic was investigated. It was found that the optimum additive amount of sodium phosphate is 2–3%.     

结合中国专利申请浅析泡沫玻璃中发泡剂的应用及发展

分析了近年来,与泡沫玻璃发泡剂相关的中国专利申请,探讨了泡沫玻璃中发泡剂的应用及发展。     

Reaction-bonded robust SiC ceramic membranes sintered at low temperature with coal gangue

Herein, we report an in-situ reaction-bonded SiC membrane sintered at low temperature using a solid waste (i.e. coal gangue) as the sintering aid to form strong neck connections. The effects of sintering temperature and coal gangue proportion on their properties regarding pore size, open porosity, bending strength and pure water permeability were investigated. The single-channel tubular SiC membrane sintered at 1300 °C with a coal gangue proportion of 12 wt% was optimal, exhibiting an average pore size of 2.78 μm, a open porosity of 47.08%, a bending strength of 34.01 ± 1.3 MPa and a high water permeability of 83967 L m⁻² h⁻¹ bar⁻¹. The membrane could completely reject D₅₀ = 0.87 μm SiC solids and presented a steady-state water permeability of 458 L m⁻² h⁻¹·bar⁻¹. The SiC membrane could be regenerated through ultrasonication and its steady-state water permeability was almost unchanged for 3 cycles, proving its mechanical robustness. This work may appeal to the practical low-cost production of high-performance SiC membranes.     

Mechanical properties of graphene platelet-reinforced alumina ceramic composites

Alumina (Al₂O₃) ceramic composites reinforced with graphene platelets (GPLs) were prepared using Spark Plasma Sintering. The effects of GPLs on the microstructure and mechanical properties of the Al₂O₃ based ceramic composites were investigated. The results show that GPLs are well dispersed in the ceramic matrix. However, overlapping of GPLs and porosity within ceramics are observed. The flexural strength and fracture toughness of the GPL-reinforced Al₂O₃ ceramic composites are significantly higher than that of monolithic Al₂O₃ samples. A 30.75% increase in flexural strength and a 27.20% increase in fracture toughness for the Al₂O₃ceramic composites have been achieved by adding GPLs. The toughening mechanisms, such as pull-out and crack deflection induced by GPLs are observed and discussed.     

Effect of binder on the structure and mechanical properties of lightweight bubble alumina ceramic

The effect of binders such as ammonium aluminum sulphate, phosphoric acid and composite binder on the properties of lightweight bubble alumina ceramic was studied. The composite binder was composed of ammonium aluminum sulphate and phosphoric acid. Ammonium aluminum sulphate solution can improve compressive strength of alumina bubbles effectively but can not improve that of lightweight bubble alumina ceramic due to the fewer nano-alumina powders in situ decomposed of ammonium alumina sulphate. Trans-ball fractures occurred in thermal shock test. Phosphoric acid solution can improve compressive strength of alumina bubble ceramic because of promoting sintering properties of aluminum phosphate in situ produced by phosphoric acid and alumina component during sintering but decrease that of alumina bubbles. Along-ball fractures occurred in thermal shock test. The composite binder combined with the advantages of ammonium alumina sulphate and phosphoric acid and improved the compressive strength of both alumina bubbles and lightweight bubble alumina ceramic, and effectively reduce the amount of the binders and lower the product cost. At the sintering temperature of 1700 °C, with composite ammonium alumina sulphate and phosphoric acid as binder, the density of lightweight bubble alumina ceramic was between 1.20 and 1.60 g/cm³, and the compressive strength was 18-42 MPa.     

改性ADC发泡剂的研究进展与市场前景

作者介绍了目前传统ADC发泡剂存在的问题,重点综述了改性ADC发泡剂产品的研究进展,包括合成工艺的改进及添加促进剂对ADC发泡剂性能的改进;同时分析了ADC发泡剂的市场情况,并对其前景进行了展望.     

Effect of particle size on mechanical properties of alumina ceramic processed by photosensitive binder jetting with powder spattering technique

As an Additive Manufacturing technique, Binder Jetting enables the fabrication of customized and complex ceramic parts. However, the insufficiency of powder packing in green parts restricts the final products’ densifications and strengths. To form a layer of ceramic green parts, Photosensitive Binder Jetting with powder spattering technique provides entrapment of ceramic powder by printing of photo-curable resin and recoating by releasing the powder through a vibrating mesh. This recoating technique enables the processing of fine alumina powders, the average particle sizes of which are 3 μm, 1.65 μm, and their mixtures. Apparent densities, porosities, mechanical properties, and microstructures of the sintered parts were investigated. The alumina sample with the apparent density of 3.70 g/cm³, the compressive strength of 94.87 MPa, the biaxial strength of 50.06 MPa, and the porosity of 41.01 % was attained by the mixture with 70:30 wt.% of the 3 μm and 1.65 μm powders respectively.     

Enhanced mechanical and sintering properties of MgO-TiO2 ceramic composite via digital light processing

In this work, MgO was applied to modify the titania ceramic slurry, which could realize the high-quality DLP printing of titania ceramic by promoting the grain growth during sintering. Combining the phase and element analysis, it was revealed that the reduced stress concentration and improved mechanical property were attributed to the formation of MgTi₂O₅ in solid-state reaction between MgO and TiO₂. When MgO content increased beyond 10 wt.%, the microstructure pinning effects showed a negative impact on ceramic grain growth. Among all the samples, 5%MgO/TiO₂ has exhibited the best bending strength of 71.9 MPa and the densification of 85%, while its sintering temperature reduced by 200 °C. Meanwhile, the compressive property of representing porous TiO₂ samples reached 18.2 MPa, which was similar to those of porous ceramics produced by conventional manufacturing routes. Overall, MgO-TiO₂ composite ceramic prepared in this study have potential application in field of monolithic catalysts and tissue engineering scaffold.     

Influence of debinding holding time on mechanical properties of 3D-printed alumina ceramic cores

Herein, alumina green bodies are fabricated by three dimensional (3D) printing technology, then, the influence of debinding holding time under vacuum and argon on mechanical properties is systematically investigated by comparing the changes in microstructure, bulk density, open porosity, grain connection situation and flexural strength of ceramics. The flexural strength of alumina ceramics acquired the maximum values of 26.4 ± 0.7 MPa and 25.1 ± 0.5 MPa after debinding under vacuum and argon for 120 min and 180 min, respectively. However, the alumina ceramics rendered the flexural strength of 19.4 ± 0.6 MPa and 9.5 ± 0.4 MPa under vacuum and argon without extended holding time, respectively. The relatively low mechanical properties can be mainly attributed to the weak interlayer binding force, which is caused by layer-by-layer forming mode during 3D printing process and anisotropic shrinkage during the sintering process. Moreover, the alumina ceramics exhibited moderate bulk density and open porosity of 2.4 g/cm³ and 42% after the sintering process, respectively, which are mainly influenced by the microstructural evolution of alumina ceramics during thermal treatment. Also, the diffusion of gases is achieved by curing of photosensitive resin and influenced by different holding times during debinding, affecting the mechanical properties of sintered ceramics. The mechanical properties of as-sintered ceramics are suitable for the utilization of ceramic cores in the manufacturing of hollow blades.     

Effect of elaboration parameters of a membrane ceramic on the filtration process efficacy

The formation of the flat membrane from kaolin and potassium phosphate was investigated with a particular focus on the appropriate elaboration parameters and the effect of their separation performance. The first step consisted in the fabrication of flat ceramic membrane supports from mechanochemicaly-treated kaolin (K) and starch (S). The mechanical properties, permeability and porosity of these supports were studied as a function of the milling time of kaolin, the starch content, the sintering temperature and time. The optimization of the elaboration parameters led to the fabrication of supports from kaolin milled for 30 min and 5% starch at sintering temperature of 1100 °C and sintering time of 1 h. In the second step, the potassium phosphate was added as a binder in the kaolin- 5% starch mixture. In this case, we noted the improvement of the permeability without reduction of the mechanical strength and porosity. Also, the separation performances and the fouling of membranes elaborated with different potassium phosphates were evaluated using Bovine Serum Albumin (BSA) solution.     

Asymmetric TiO2 hybrid photocatalytic ceramic membrane with porosity gradient: Effect of structure directing agent on the resulting membranes architecture and performances

Asymmetric TiO₂ hybrid photocatalytic ceramic membranes with porosity gradient have been fabricated via acid-catalyzed sol–gel method. Different structure directing agents (SDAs) i.e. Pluronic P-123, Triton X-100, Tween 20 and Tween 80 were incorporated in the preparation of TiO₂ sol to obtain a porous multilayered TiO₂ coated on the alumina ceramic support. Six different SDA-modified membrane specimens were fabricated. Four of which were coated with the TiO₂ sols prepared using only one type of SDA. The remaining two specimens were fabricated via multilayer coating of different TiO₂ sols prepared using different types of SDAs. Physico-chemical and morphological properties of different TiO₂ layers were thoroughly investigated. The membrane M1 which had the most porous TiO₂ sub-layers showed a high pure water permeability of 155 L m⁻² h⁻¹ bar⁻¹. The membrane showed a relatively high Rhodamine B (RhB) removal of 2997 mg m⁻² over 8 h treatment duration in the batch photoreactor, second only to the Pluronic-based TiO₂ membrane (specific RhB removal of 3050 mg m⁻²). All membrane specimens exhibited good performances while operated in the flow-through photocatalytic membrane reactor. Over 91% of RhB removal capability was retained after 4 treatment cycles. All membranes also showed self-cleaning property by retaining >90% of initial flux after 4 treatment cycles. The flexibility of optimizing membrane performances by fine-tuning the porosity gradient configuration of the photocatalytic layer has also been demonstrated.     

Fabrication and characterization of mini alumina ceramic turbine rotor using a tailored gelcasting process

A mini alumina ceramic turbine rotor has been successfully fabricated using a tailored colloidal process based on gelcasting technology. A specialized forming, drying and sintering approach was developed for the complex-shaped component with both large volume (90 mm in diameter and 20 mm in height) and submillimeter geometry (0.42 mm at the blade tip with curvature), to assure a highly dense product without warpage and cracks. The effects of solid content and temperature on the rheological behaviors of the prepared slurry were investigated to identify the best pourability. A novel approach using radius of curvature and overlapped area was adopted to compare the blade contour similarity under different sintering strategies and solid contents. In addition, the different physical and mechanical properties between main body and blade regions were discussed and their microstructures were analyzed. The preparation route for highly dense alumina rotor with minimum contour distortion was finally summarized.     

Effect of phase composition of natural quartz raw material on characterization of microfiltration ceramic membranes

The results of development of multi-layer ceramic membranes on the basis of natural quartz raw material from Mongolia are presented. The influence of the phase composition and temperature of calcination on the porosity, morphology and mechanical strength of large-porous ceramic support obtained by the method of isostatic pressing was studied. It was established that multi-layer ceramic membranes obtained by the application of water suspension of high-disperse quartz sand of Mongolia and alumosilicate binder with the addition of 15–35 wt% of quartz are characterized by optimal properties. The developed tubular ceramic membranes with the average pore size 5.3 µm, coefficient of air permeability (4.17–4.41)×10⁻¹³ m², productivity by water 46.3–48.0 m³/(h×m²×bar) and mechanical strength 2.27–2.53 MPa are perspective for wide use in microfiltration processes.     

助剂对聚烯烃发泡母粒性能的影响

将不同含量助剂添加到聚烯烃发泡母粒中,通过对样品进行力学性能测试,表明当分散剂聚乙烯蜡用量为5份、成核剂TiO_2用量为7.5份、填充剂改性碳酸钙用量为7.5份时,聚烯烃发泡材料的力学性能最好,材料内部泡孔大小均一,且分布均匀。     

Gelcasting of alumina suspension using gellan gum as gelling agent

As one of the excellent colloidal ceramic forming methods for fabricating complex shaped ceramic components, gelcasting has been extensively investigated in the past two decades. In this article, a novel nontoxic system for gelcasting of ceramics was investigated using gellan gum as gelling agent. The rheological and gelling properties of gellan gum solutions with different types of cations and different concentrations of divalent magnesium ions were studied. Influences of concentration of gellan gum and solid loading of alumina suspension on the rheological properties and gelling properties of alumina suspension were investigated. The rheological properties of concentrated alumina suspension mixing with gellan gum and magnesium chloride were evaluated. Dense ceramics prepared by gellan gum gelation showed homogeneous microstructure and good mechanical properties.     

Effect of Sintering Additive on the Properties of Sialon-SiC by Gelcasting

Sintering additivesto gelcasting Sialon‘SiC were decided by the optimizing experiments , The resuhs show that Sialon-SiC can be sintered under 1450℃ and sintering temperature dcreases by 100℃，when 2%～3% TiO2 or Guangxi clay is used as sintering additive.     

Effect of sintering temperature on microstructure and mechanical properties of zirconia-toughened alumina machinable dental ceramics

This study investigated the effect of sintering temperature on the microstructure and mechanical properties of dental zirconia-toughened alumina (ZTA) machinable ceramics. Six groups of gelcast ZTA ceramic samples sintered at temperatures between 1100 °C and 1450 °C were prepared. The microstructure was investigated by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The mechanical properties were characterized by flexural strength, fracture toughness, Vickers hardness, and machinability. Overall, with increasing temperature, the relative density, flexural strength, fracture toughness, and Vickers hardness values increased and more tetragonal ZrO₂ transformed into monoclinic ZrO₂; on the other hand, the porosity and pore size decreased. Significantly lower brittleness indexes were observed in groups sintered below 1300 °C, and the lowest values were observed at 1200 °C. The highest flexural strength and fracture toughness of ceramics reached 348.27 MPa and 5.23 MPa m^1/2 when sintered at 1450 °C, respectively. By considering the various properties of gelcast ZTA that varied with the sintering temperature, the optimal temperature for excellent machinability was determined to be approximately 1200–1250 °C, and in this range, a low brittleness index and moderate strength of 0.74–1.19 µm^−1/2 and 46.89–120.15 MPa, respectively, were realized.     

Gas permeation properties in a composite mesoporous alumina ceramic membrane

In this study, the effect of different chemical interactions on the gas permeation properties were investigated in the composite mesoporous ceramic membrane prepared with γ-alumina on the surface of a macroporous ceramic membrane. In the permeation results, the gas permeance of the strongly adsorbing gas species increased in the mesoporous ceramic membranes. It is considered that the permeation of the adsorbing gas species increased through preferential adsorption on the membrane pore surface. It was shown in this study that the modified mesoporous ceramic membrane could increase the permeation performance in the presence of the adsorbing gas species due to the surface diffusion mechanism.     

Effect of sintering temperature on the microstructure and performance of a ceramic coating obtained by the slurry method

In this paper, SiO₂, Cr₂O₃, Al₂O₃, and MgO were used as ceramic aggregates, and a small amount of Al powder was added. A ceramic coating was prepared on a Q235 steel substrate. The effect of the sintering temperature on the coating microstructure, phase structure and wear resistance was studied by Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and friction and wear testing. The results show that the tensile strength of the ceramic coating is increased after sintering, the structure becomes dense, and the size of coated micropores is increased to release the internal tensile stress. With the increase of the sintering temperature and tensile stress, the micropores begin to release the excess tensile stress in the form of crack initiation and expansion. The mineralization of MgO, Cr₂O₃, nMgO and mSiO₂ phases can be achieved by sintering the coating at 200?°C; the oxygen in the atmosphere migrates along the micropores in the coating to react with Fe in the steel substrate, forming FeO, and the resulting FeO reacts with the SiO₂ in the coating to form the Fe₂SiO₄ phase. The coating has the best wear resistance after being sintered at 400?°C, and the abrasion resistance of the sample is 6.7 times higher than that of the sample dried at room temperature.