In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, ...In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.展开更多
In this study, production and mechanical properties of polymer composite materials obtained by using Al2O3, SiO2, MgO and TiO2 hard ceramic fillers were studied. Epoxy resin was used as the matrix material, and four d...In this study, production and mechanical properties of polymer composite materials obtained by using Al2O3, SiO2, MgO and TiO2 hard ceramic fillers were studied. Epoxy resin was used as the matrix material, and four different ceramic powders were mechanically mixed into the resin at 3% and 5% as reinforcement. The mechanical properties of the polymer composite materials were then characterized. For this purpose, flexural modulus and flexural strength of composite materials were determined by using three point bending test and impact toughness of the materials were determined by Charpy impact test. In addition, the hardness values of the samples were determined by Shore D hardness test.展开更多
Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, follo...Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, followed by individual corrosion resistance examination. Microstructural characterization showed that the levels of micro-void and micro-crack at the bonding interface （between coating and substrate） depended on the proportions of different ceramic particles. Meanwhile, a significantly enhanced corrosion resistance was reproducibly observed in one group of as-coated samples that have the optimal combination of given ceramic powders. Furthermore, the mechanism of corresponding enhanced corrosion resistance was discussed. It was found that the optimal ceramic powders for the present thermal-sprayed coating should contain 30.2 wt% SiO2, 54 wt% Cr2O3, 6.8 wt% Al2O3, 4.8 wt% CaO and 1.8 wt% TiO2. The corrosion velocities of such samples in the 3.5 vol.% HCl, 15 wt% NaOH and 5 wt% NaCl solutions were 3.74, 2.98 and 0.50 g h-1 m-2 for 168, 336 and 336 h, respectively.展开更多
This paper presents an innovative approach to reusing waste tile granules(TG) and ceramic polishing powder(PP) to produce high performance ceramic tiles.We studied formulations each with a TG mass fraction of 25.0% an...This paper presents an innovative approach to reusing waste tile granules(TG) and ceramic polishing powder(PP) to produce high performance ceramic tiles.We studied formulations each with a TG mass fraction of 25.0% and a different PP mass fraction between 1.0% and 7.0%.The formulations included a small amount of borax additive of a mass fracton between 0.2% and 1.2%.The effects of these industrial by-products on compressive strength,water absorption and microstructure of the new ceramic tiles were investigated.The results indicate that the compressive strength decreases and water absorption increases when TG with a mass fraction of 25.0% are added.Improvement of the compressive strength may be achieved when TG(up to 25.0%) and PP(up to 2.0%) are both used at the same time.In particular,the compressive strength improvement can be maximized and water absorption reduced when a borax additive of up to 0.5% is used as a flux.Scanning electron microscopy reveals that a certain amount of fine PP granules and a high content of fluxing oxides from borax avail the formation of glassy phase that fills up the pores in the new ceramic tiles,resulting in a dense product with high compressive strength and low water absorption.展开更多
A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed w...A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed with a water-soluble agent to produce slurry. The slurry was then injected into an epoxy mold with inverse diamond lattice, fabricated by the stereolitographic rapid prototyping process. To increase the density of the green compact, cold isostatic pressing was applied on the unit. Using thermal debinding, the water-soluble agent and the epoxy were extracted at 360 and 650 K, respectively. Sintering was immediately done at 950 K for 5 h and the desired three-dimensional ceramic structure was obtained. The calculated band diagram for this structure indicated the existence of an absolute photonic bandgap for all wave vectors. At 14.7-18.5 GHz, a complete band gap was located with a maximum attenuation of 30 dB at 17 GHz, when transmission was measured in the 〈100〉 direction between 10 and 20 GHz.展开更多
Face centred cubic（FCC） TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives（ECAs） with the polymer matrix.Electrically conductive ...Face centred cubic（FCC） TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives（ECAs） with the polymer matrix.Electrically conductive properties of the ceramic ECAs were studied.The bulk electrical resistivity varied with the powder content of the FCC-TiB in ECAs.The FCC-TiB filled ECAs also showed the percolation behavior that usually occurred for the metal-filled ECAs,the percolation threshold was located at the content of 60%FCC-TiB.A minimum value of 0.1 Ω·cm was obtained at a content of 75%FCC-TiB.In order to check the reliability of mechanical property,tensile test was done to measure the shear strength,and the shear strength dropped with increasing the content of FCC-TiB powders.It is about 12.26 MPa at the content of 70%TiB powders.The Cu filled ECAs were also prepared for comparison.The properties of the oxidation resistance of the two ECAs were evaluated.The results show that the ceramic ECAs have excellent oxidation resistance and better stability compared with the Cu filled ECAs.展开更多
The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influenc...The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.展开更多
The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle ...The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle were demonstrated by observing the TGA and DTA plots of AlN green specimens and analyzing the microstructure at different temperatures. By adding HDPE into the PW EVA binder used in powder injection molding AlN can effectively reduce the mass lose rate in debinding process and improve the shape retention ability. At last, aluminum nitride ceramic with high room temperature thermal conductivity of 162.5?W·m -1 ·K -1 was produced. [展开更多
Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as oper...Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as operation pressure, cross-flow velocity, and slurry concentration, were examined and optimized. The shape and size of particles influenced the structure of the filter cake, leading to different permeation flux for different systems. The results demonstrated that washing using ceramic membranes is superior to the traditional plate-and-frame filtration and could be considered an advanced technique for ultra-fine powder preparation by wet-chemical method.展开更多
A model of the thermal dissociation process has been developed for the numerical simulation of ceramic powder processing in a d. c. plasma reactor. The temperature histories of zircon grains were calculated based on t...A model of the thermal dissociation process has been developed for the numerical simulation of ceramic powder processing in a d. c. plasma reactor. The temperature histories of zircon grains were calculated based on this model. Comparisons were carried out to determine the effects of plasma gas (N_2 and Ar), free stream temperature (6000-15000K) and Reynolds number (0.0-1.0) as well as particle diameter (20-200μm) on the zircon dissociation process. The influences of proper Nusselt number correlation and variable transport properties were discussed in detail.展开更多
基金financially supported by the National Natural Science Foundation of China(grant no.51204028)
文摘In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.
文摘In this study, production and mechanical properties of polymer composite materials obtained by using Al2O3, SiO2, MgO and TiO2 hard ceramic fillers were studied. Epoxy resin was used as the matrix material, and four different ceramic powders were mechanically mixed into the resin at 3% and 5% as reinforcement. The mechanical properties of the polymer composite materials were then characterized. For this purpose, flexural modulus and flexural strength of composite materials were determined by using three point bending test and impact toughness of the materials were determined by Charpy impact test. In addition, the hardness values of the samples were determined by Shore D hardness test.
文摘Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, followed by individual corrosion resistance examination. Microstructural characterization showed that the levels of micro-void and micro-crack at the bonding interface （between coating and substrate） depended on the proportions of different ceramic particles. Meanwhile, a significantly enhanced corrosion resistance was reproducibly observed in one group of as-coated samples that have the optimal combination of given ceramic powders. Furthermore, the mechanism of corresponding enhanced corrosion resistance was discussed. It was found that the optimal ceramic powders for the present thermal-sprayed coating should contain 30.2 wt% SiO2, 54 wt% Cr2O3, 6.8 wt% Al2O3, 4.8 wt% CaO and 1.8 wt% TiO2. The corrosion velocities of such samples in the 3.5 vol.% HCl, 15 wt% NaOH and 5 wt% NaCl solutions were 3.74, 2.98 and 0.50 g h-1 m-2 for 168, 336 and 336 h, respectively.
基金Funded by a grant from the Key Technologies R & D Program of Guangzhou (No. 2004440003110013)
文摘This paper presents an innovative approach to reusing waste tile granules(TG) and ceramic polishing powder(PP) to produce high performance ceramic tiles.We studied formulations each with a TG mass fraction of 25.0% and a different PP mass fraction between 1.0% and 7.0%.The formulations included a small amount of borax additive of a mass fracton between 0.2% and 1.2%.The effects of these industrial by-products on compressive strength,water absorption and microstructure of the new ceramic tiles were investigated.The results indicate that the compressive strength decreases and water absorption increases when TG with a mass fraction of 25.0% are added.Improvement of the compressive strength may be achieved when TG(up to 25.0%) and PP(up to 2.0%) are both used at the same time.In particular,the compressive strength improvement can be maximized and water absorption reduced when a borax additive of up to 0.5% is used as a flux.Scanning electron microscopy reveals that a certain amount of fine PP granules and a high content of fluxing oxides from borax avail the formation of glassy phase that fills up the pores in the new ceramic tiles,resulting in a dense product with high compressive strength and low water absorption.
基金This work was financially supported by the Major State Basic Research Development Program of China (No.2004CB719802).
文摘A novel process, which was based on powder injection molding, was investigated for the fabrication of ceramic photonic bandgap structure with three-dimensional diamond lattice. The SiO2-TiO2 ceramic powder was mixed with a water-soluble agent to produce slurry. The slurry was then injected into an epoxy mold with inverse diamond lattice, fabricated by the stereolitographic rapid prototyping process. To increase the density of the green compact, cold isostatic pressing was applied on the unit. Using thermal debinding, the water-soluble agent and the epoxy were extracted at 360 and 650 K, respectively. Sintering was immediately done at 950 K for 5 h and the desired three-dimensional ceramic structure was obtained. The calculated band diagram for this structure indicated the existence of an absolute photonic bandgap for all wave vectors. At 14.7-18.5 GHz, a complete band gap was located with a maximum attenuation of 30 dB at 17 GHz, when transmission was measured in the 〈100〉 direction between 10 and 20 GHz.
基金Project (51172088) supported by the National Natural Science Foundation of China
文摘Face centred cubic（FCC） TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives（ECAs） with the polymer matrix.Electrically conductive properties of the ceramic ECAs were studied.The bulk electrical resistivity varied with the powder content of the FCC-TiB in ECAs.The FCC-TiB filled ECAs also showed the percolation behavior that usually occurred for the metal-filled ECAs,the percolation threshold was located at the content of 60%FCC-TiB.A minimum value of 0.1 Ω·cm was obtained at a content of 75%FCC-TiB.In order to check the reliability of mechanical property,tensile test was done to measure the shear strength,and the shear strength dropped with increasing the content of FCC-TiB powders.It is about 12.26 MPa at the content of 70%TiB powders.The Cu filled ECAs were also prepared for comparison.The properties of the oxidation resistance of the two ECAs were evaluated.The results show that the ceramic ECAs have excellent oxidation resistance and better stability compared with the Cu filled ECAs.
基金Item Sponsored by Provincial Natural Science Foundation of Jiangsu of China(BK2000012)
文摘The composite coating was prepared by thermal spray welding after making composite powder,which is composed of Ni-based self-melted alloy and AlOceramic powder including nano,sub-micron and micron powders.The influences of contents and sizes of AlOon the structure and wearability were investigated.The results show that the wear resistance of the coating would be increased greatly by adding AlO,but the spray weldability decreases with increasing AlOcontent.So there is an optimal content of AlOpowder.The composite coating with AlOnano or sub-micron powder of 0.5% has the best abrasive resistance,while the optimal content of AlOmicron powder is 1 %.
文摘The thermal degradation behaviors of AlN green specimens were studied by thermogravimetry analysis during the ceramic powder injection molding debinding process. The optimum binder composition and the debinding cycle were demonstrated by observing the TGA and DTA plots of AlN green specimens and analyzing the microstructure at different temperatures. By adding HDPE into the PW EVA binder used in powder injection molding AlN can effectively reduce the mass lose rate in debinding process and improve the shape retention ability. At last, aluminum nitride ceramic with high room temperature thermal conductivity of 162.5?W·m -1 ·K -1 was produced. [
基金financially supported by the Ministry of Science and Technology of China (Contract No. 2003CB615700)the Foundation of Science and Technology of the Educational Office of Anhui province, China (Contract No. 2005kj138)
文摘Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as operation pressure, cross-flow velocity, and slurry concentration, were examined and optimized. The shape and size of particles influenced the structure of the filter cake, leading to different permeation flux for different systems. The results demonstrated that washing using ceramic membranes is superior to the traditional plate-and-frame filtration and could be considered an advanced technique for ultra-fine powder preparation by wet-chemical method.
文摘A model of the thermal dissociation process has been developed for the numerical simulation of ceramic powder processing in a d. c. plasma reactor. The temperature histories of zircon grains were calculated based on this model. Comparisons were carried out to determine the effects of plasma gas (N_2 and Ar), free stream temperature (6000-15000K) and Reynolds number (0.0-1.0) as well as particle diameter (20-200μm) on the zircon dissociation process. The influences of proper Nusselt number correlation and variable transport properties were discussed in detail.
