Cerium Oxide Ceramic Parts

The phase transition from γ-Al2O3 to α-Al2O3 is characterized by a reduction in surface area. Cerium oxide ceramic parts are used to prevent alpha-alumina phase transitions, helping to effectively maintain a high surface area under reducing conditions at temperatures up to 1000°C. Alumina-ceria composites are widely used in catalytic converters.

Zhongwei Precision is committed to providing domestic and foreign customers with advanced ceramics with high strength, high toughness, wear resistance, corrosion resistance and high temperature resistance. It is a high-tech enterprise integrating R&D, production and sales of industrial precision advanced ceramic products in the field of precision ceramics. With a variety of modern high-precision equipment, it has independently realized the completion of the entire production process of ceramic parts from ceramic powder preparation, green body molding, high temperature sintering to ceramic material finishing.

Product Description

1. Implementation standards: the company strictly implements ISO9001 certification, and the products have passed ROHS, FDA EU certification, etc.

2. Product material standards: ISO, GB, ASTM, SAE, EN, DIN, BS, AMS, JIS, ASME, DMS, TOCT, GB

3. Main processes: grouting, injection molding, tape casting, isostatic pressing, 3D printing

4. Available materials for ceramics:

It mainly produces finished ceramic rods, ceramic tubes, ceramic rings, ceramic plates, ceramic suction cups, ceramic blades and other special-shaped ceramic structures. The main ceramic materials are alumina, zirconia, silicon carbide, silicon nitride, and aluminum nitride ceramics. High temperature resistance, wear resistance, corrosion resistance, acid and alkali resistance, anti-magnetic, pressure resistance. And 3D printing, etc. are customized according to customer requirements.

Combined tube, its high wear resistance effectively resists material wear and impact.

Application

Cerium oxide ceramic parts (ceriaceramics) refers to ceramics with cerium oxide as the main component.

Properties: The specific gravity of this product is 7.73 and the melting point is 2600℃. It will become Ce2O3 under reducing atmosphere, and the melting point will drop from 2600℃ to 1690℃. The resistivity is 2 x 10 ohm cm at 700°C and 20 ohm cm at 1200°C. At present, the commonly used process technologies for industrial production of cerium oxide in my country are as follows:

1) Chemical oxidation method, including air oxidation method and potassium permanganate oxidation method;

2) roasting oxidation method;

3) Extraction separation method.

application:

1) It can be used as heating element, crucible for melting metal and semiconductor, thermowell, etc.;

2) Cerium oxide ceramic parts can be used as a sintering aid for silicon nitride ceramics, and can also be used to modify aluminum titanate composite ceramics, and CeO2 is an ideal toughening stabilizer;

3) Rare earth tricolor phosphors added with 99.99% CeO2 are luminescent materials for making energy-saving lamps, with high luminous efficiency, good color rendering and long service life;

4) The high cerium polishing powder made of CeO2 with a mass fraction of more than 99% has high hardness, small and uniform particle size, and the crystal has edges and corners, which is suitable for high-speed polishing of glass;

5) Using 98% CeO2 as a glass decolorizer and clarifying agent can improve the quality and performance of the glass and make the glass more practical;

6) Cerium oxide ceramics have poor thermal stability and strong sensitivity to atmosphere, which limits its use to a certain extent.

γ-Al2O3 has a large surface area, but due to the limited temperature range in which the phase transition can play an effective role, Alessandro et al. investigated the thermal and structural stability of Al2O3/CeO2 composites with a CeO2 content of 2% to 25% in different atmospheres. Sex has been studied. It is said that cerium oxide as a stabilizer for γ-Al2O3 almost completely fails under oxidizing conditions, and its effect is significantly improved under reducing conditions. The formation of Ce3+ (mainly CeAlO3) under reducing conditions can prevent crystal growth and prevent the formation of α-Al2O3 which leads to a decrease in surface area. Damyanova et al. prepared Al2O3/CeO2 mixed oxides with different CeO2 contents (ranging from 0.5 to 12 wt.%). The samples were calcined at 500°C and 800°C and characterized by different methods. Experiments show that with different CeO2 content and calcination temperature, the types of cerium oxide formed on the surface of the samples are different. When the CeO2 content is higher than 6wt.%, nano-cerium oxide is formed on the surface of alumina, and when the concentration of cerium oxide is low, it is amorphous. If 1 wt.% CeO2 is added, the strong interaction between alumina and ceria leads to the formation of surface CeAlO3-like phases. Sayle et al. studied the effect of cerium peroxide coating on alumina and analyzed interfacial defects. The interfacial oxygen vacancies are said to be less stable to the Al2O3 interfacial CeO2 monolayer. According to Holles et al., alumina-cerium oxide composites (Pd/CeOx/Al2O3 and Rh/CeOx/Al2O3) with metallic platinum were used as catalytic converters to remove carbon monoxide, nitrogen oxides, and undesired emissions from automobiles. Exhaust gas such as burning hydrocarbons. It has also been reported that the presence of ceria can improve the performance of catalytic converters. Zhang et al. prepared composite oxide powders from CeO2, Al2O3 and GdO2 powders by a conventional method, and sintered them at 1550 °C for 5 hours in the atmosphere. Measurements of microhardness and indentation fracture toughness show that the Ce0.8Gd0.2O2 ceramic has a Wicker hardness of 9.23GPa and an indentation fracture toughness of 1.47MPam1/2. If the Al2O3 content of the samples is higher than 10%, the hardness and fracture toughness are significantly improved.

95 wt. % alumina powder and 5 wt. % cerium oxide powder with an average particle size of 1.2 μm and 5 μm, respectively, were mixed. The alumina-cerium oxide mixture was mixed with polyvinyl alcohol and cold-pressed unidirectionally into a diamond-shaped blade at a pressure of 200 MPa. The green body was sintered in the atmosphere at 1600°C for 2.5 hours. For comparison, pure alumina powder was cold-pressed and sintered under the same conditions as described above. The sintered samples were finished on a grinding machine with a diamond wheel. The final shape and dimensions of the inserts meet the requirements of the international standard ISO CNGN120708. The density of the alumina-cerium oxide green body is 62% of the theoretical density, and the density of the sintered sample is 96% of the theoretical density. The density of the pure alumina green body is 59% of the theoretical density, and the density of the sintered sample is 92% of the theoretical density. The XRD (X-ray diffraction) pattern of the sintered alumina-ceria inserts confirmed the presence of α-Al2O3 (corundum) and CeO2 (cerianite) in the sintered alumina-ceria inserts. The hardness of alumina-cerium oxide inserts is 1680HV, while the hardness of pure alumina inserts is 1650HV. Alumina-cerium oxide inserts are slightly harder than pure alumina inserts due to their increased densification. The fracture toughness of the alumina-cerium oxide insert is 4.7MPam1/2, while the fracture toughness of the pure alumina insert is 3.4MPam1/2. The fracture toughness value of alumina-cerium oxide is higher than that of pure alumina due to the particle toughening of the composite. Kim et al. believe that the improved mechanical properties such as hardness, fracture toughness, elastic modulus, and strength of the composite are due to the improved sintered density.

Cutting tests were performed on grey cast iron workpieces (hardness 170BHN) on a precision lathe with newly developed alumina-cerium oxide ceramic inserts prepared in the laboratory. For comparison, the cutting test also used laboratory-made pure alumina inserts and commercial zirconia-toughened alumina (ZTA) inserts. Industrial ZTA inserts contained 96.5 wt.% alumina and 3.5 wt.% zirconia. Its density is higher than 99% of the theoretical density. The hardness of ZTA is 1730HV and the fracture toughness is 4.5MPam1/2. Because ceramics are generally used to machine cast iron, gray cast iron is selected for cutting test. Cutting amount: cutting speed 120, 170, 270m/min, feed rate 0.12mm/r, cutting depth 0.5mm, processing time 15min, dry cutting. The shank specification is ISO CCLNR 2525 M 1207. The performance of ceramic inserts is evaluated by measuring the wear behind the insert and the surface finish of the machined workpiece.

Tool wear has an adverse effect on tool durability, surface quality and dimensional accuracy, thereby affecting the economic benefits of cutting. Among different forms of tool wear, rear wear is an important measure of tool wear because it affects the dimensional accuracy of the workpiece. It can be seen from the graph of the change of wear on the back of the ceramic insert with the machining time and the graph of the change of the wear on the back of the ceramic insert with the cutting speed, the back wear of the alumina-cerium oxide insert is comparable to that of the industrial ZTA insert, and lower than that of the pure alumina insert. The main wear mechanisms in the latter wear are abrasive wear and adhesive wear. The back wear of ceramic tools increases with cutting speed. As with other ceramic tools, the rear wear of alumina-cerium oxide ceramic inserts is also progressive, and no severe wear pattern is observed when machining gray cast iron under the given machining conditions. The rear wear resistance of the newly developed alumina-cerium oxide inserts is superior to pure alumina inserts due to improved mechanical properties.

The surface finish of Cerium oxide ceramic parts affects not only the dimensional accuracy of the workpiece, but also its properties. Turning maintains both dimensional accuracy and surface quality. The dimensional accuracy is controlled by the rear wear of the turning tool, and the surface quality is mainly determined by the shape stability of the tool tip. The ideal tool in turning can fully reproduce its cutting edge on the workpiece surface, so the surface quality of the turning workpiece is largely determined by the shape stability of the cutting edge. It can be seen from the relationship between the surface roughness Ra and the cutting speed of the ceramic blade after 15min processing that the surface finish processed by the ceramic blade improves with the increase of the cutting speed. Alumina-cerium oxide inserts produce a surface finish comparable to industrial ZTA inserts and better than pure alumina inserts. The surface finish of alumina-cerium oxide ceramic inserts on the machined workpiece is better than that of pure alumina inserts, which is due to the improved mechanical properties that improve the shape stability of the tool tip.

Process After Sintering

Processing equipment: equipped with CNC engraving machine, centerless grinding, internal and external cylindrical grinding, surface grinding, CNC lathe machining center, wire cutting, turning, milling, grinding and other high-precision production and testing equipment.

Moulds and Inspection Fixtures

1. Mold service life: usually semi-permanent. (except for lost foam).

2. Mold delivery time: 10-25 days, (according to product structure and product size).

3. Tooling and mold maintenance: Zhongwei is responsible for precision parts.

Quality Control

1. Quality control: the defective rate is less than 0.1%.

2. Samples and trial run will be 100% inspected during production and before shipment, sample inspection for mass production according to ISDO standards or customer requirements.

3. Test equipment: roundness measuring instrument, three-coordinate measuring instrument, image coordinate measuring instrument, Hexagon three-coordinate measuring instrument, image measuring instrument, density measuring instrument, smoothness measuring instrument, micro Vickers hardness tester.