Bonding of Si 3N 4 ceramic was performed with Y 2O 3 Al 2O 3 SiO 2(YAS) X glass solders,which were mixed with TiO 2 (YT) and Si 3N 4 (YN), respectively. The effects of bonding conditions and interfacial r...Bonding of Si 3N 4 ceramic was performed with Y 2O 3 Al 2O 3 SiO 2(YAS) X glass solders,which were mixed with TiO 2 (YT) and Si 3N 4 (YN), respectively. The effects of bonding conditions and interfacial reaction on the joint strength were studied. The joint strength in different bonding conditions was measured by four point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that with the increase of bonding temperature and holding time, the joint strength increases reaching a peak, and then decreases. When TiO 2 is put into YAS solder,the bonding interface with Si 3N 4/(Y Sialon glass+TiN)/TiN/Y Sialon glass is formed. When YAS solder is mixed with Si 3N 4 powder, the interfacial residual thermal stress may be decreased, and then the joint strength is enhanced. According to microanalyses, the bonding strength is related to interfacial reaction.展开更多
Diffusion bonding of refractory Nb–Si-based alloy was performed with Ni/Al and Ti/Al nanolayers under the condition of 1473 K/30 MPa/60 min.The NbSS/Nb5Si3 in situ composite with the nominal composition of Nb–22 Ti...Diffusion bonding of refractory Nb–Si-based alloy was performed with Ni/Al and Ti/Al nanolayers under the condition of 1473 K/30 MPa/60 min.The NbSS/Nb5Si3 in situ composite with the nominal composition of Nb–22 Ti–16 Si–3 Cr–3 Al–2 Hf was used as the parent material.The joint microstructures were examined by using a scanning electron microscope equipped with an X-ray energy dispersive spectrometer.Shear test was conducted for the bonded joints at room temperature.Within the joint bonded with Ni/Al multilayer,element diffusion occurred between the base metal and the nanolayer,with the reaction products of AlNb2+Ni3 Al,NiAl and AlNi2 Ti phases.The average shear strength was 182 MPa.While using Ti/Al multilayer,the interface mainly consisted of TiAl,(Ti,Nb)Al and(Ti,Nb)2 Al phases,and the corresponding joints exhibited an increased strength of 228 MPa.In this case,the fracture mainly took place in the TiAl phase and presented a typical brittle characteristic.展开更多
Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced ...Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced using different processing parameters, including powder size, laser power, scanning speed and hatch distance. Results showed that the pre-alloyed powders ranging from 45 to 75 lm were more applicable to SLM with less balling tendency, in comparison with those between 75 and 180 lm. The increase in linear energy density（LED） resulted in the decrease in contact angle and the increase in the width of single track as well as its penetration depth into the substrate. Smaller hatch distance leaded to a larger remelted part of the former track and a higher volumetric laser energy density. With a thickness of 75.6 lm, an interfacial intermediate layer, enriched in Ti and depleted in Nb, Si, Cr and Al, was formed between the SLM part and the Ti6Al4V substrate. The mechanisms of the elimination of balling phenomenon by employing a higher LED and the interfacial bonding characteristics between Nb–Si-based alloys via SLM and the Ti6Al4V substrate were discussed.展开更多
The bonding performance between synthetic diamond grit and adhesive ( Co-Si alloy) in polycrystalline diamond compact ( PDC) has been investigated. The results indicate that the carbide-forming element Si diffuses tow...The bonding performance between synthetic diamond grit and adhesive ( Co-Si alloy) in polycrystalline diamond compact ( PDC) has been investigated. The results indicate that the carbide-forming element Si diffuses towards the diamond grit and the quantity of Si element in the inter layer of diamond grit-adhesives is about two times higher than that in the other area. New compound SiC exists in the inter layer of diamond-adhesives. The formation of SiC enhances the strength and prolongs the service life of PDC. The sintering time is important to the formation of SiC.展开更多
A new set of technique was adopted in bonding Si-Si by using Ge (Ⅳ element),which is used as the substitute for the common hydrophilic method. The bond layer has no holes, and the edge bond-rate amounts to above 98%,...A new set of technique was adopted in bonding Si-Si by using Ge (Ⅳ element),which is used as the substitute for the common hydrophilic method. The bond layer has no holes, and the edge bond-rate amounts to above 98%, and the bond strength is above 2156 Pa. By doping the same kind of dopant with low-resistance in Ge, the stress compensation was realized.展开更多
Liquid bonding of Si 3N 4 ceramic composite was carried out with RE 2O 3 Al 2O 3 SiO 2 glass solders. The effect of bonding conditions and interfacial reaction on the joint strength was studied. The joint st...Liquid bonding of Si 3N 4 ceramic composite was carried out with RE 2O 3 Al 2O 3 SiO 2 glass solders. The effect of bonding conditions and interfacial reaction on the joint strength was studied. The joint strength under different bonding conditions was measured by four point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that the liquid glass solders react with Si 3N 4 at interface, forming the Si 3N 4/Si 2N 2O/Y(La) sialon glass/Y(La) sialon glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increased reaching a peak, and then decreased. According to microanalyses, LaYO 3 precipitated from joint glass improves joint strength at room and high temperature.展开更多
Solid liquid state pressure bonding of Si 3N 4 ceramics with aluminum based alloys, which contain a small amount of intermetallic compounds Al 3Ti or Al 3Zr, was investigated. With this new method, the heat resistant ...Solid liquid state pressure bonding of Si 3N 4 ceramics with aluminum based alloys, which contain a small amount of intermetallic compounds Al 3Ti or Al 3Zr, was investigated. With this new method, the heat resistant properties of the bonding zone metal are improved, and the joints’ strengths at high temperature is increased. The joints’ shear strength at room temperature and at 600 ℃ reach 126～133 MPa and 32～34 MPa, respectively, with suitable bonding pressure. The reaction between aluminum and Si 3N 4 ceramics, which produces Al Si N O type compounds is the dominant interfacial reaction, while the reactions between the second active element Ti or Zr in the aluminum based alloys and Si 3N 4 ceramics also occur to some extend. [展开更多
This paper reports a study on the reconstruction of broken Si O Si bonds in iron ore tailings (IOTs) in concrete. Limestone and IOTs were used to investigate the influence of different types of coarse aggregates on th...This paper reports a study on the reconstruction of broken Si O Si bonds in iron ore tailings (IOTs) in concrete. Limestone and IOTs were used to investigate the influence of different types of coarse aggregates on the compressive strengths of concrete samples. The dif- ferences in interfacial transition zones (ITZs) between aggregate and paste were analyzed by scanning electron microscopy (SEM) and ener- gy-dispersive spectroscopy (EDS). Meanwhile, X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to study microscopic changes in limestone and IOTs powders in a simple alkaline environment that simulated cement. The results show that the compressive strengths of IOTs concrete or paste are higher than those of limestone concrete or paste under identical conditions. The Ca/Si atom ratios in the ITZs of IOTs con- crete samples are lower than those of limestone concrete;the diffraction peak of the calcium silicate phase at 2θ = 29.5°, as well as the bands of Si O bonds shifting to lower wavenumbers, indicates reconstruction of the broken Si-O-Si bonds on the surfaces of IOTs with Ca(OH)2.展开更多
Three kinds of polysilanes containing Si-H bond, ■CH_3SiCH_3■_x■CH_3SiH■_y■_n and■PhSiPh■_π■CH_3SiH■_y■CH_3SiCH_3■, have been synthesized. The structures of these copolymers were investigated by IR, ~1H-NM...Three kinds of polysilanes containing Si-H bond, ■CH_3SiCH_3■_x■CH_3SiH■_y■_n and■PhSiPh■_π■CH_3SiH■_y■CH_3SiCH_3■, have been synthesized. The structures of these copolymers were investigated by IR, ~1H-NMR and ^(13)C-NMR and their molecular weights were measured.展开更多
Seven unsymmetrical diaminodimethylsilanes were prepared. The reactions of these silylamine with benzoyl chloride indicated that in comparison with electronic, the steric effect played more important role on the react...Seven unsymmetrical diaminodimethylsilanes were prepared. The reactions of these silylamine with benzoyl chloride indicated that in comparison with electronic, the steric effect played more important role on the reactivity of Si-N bond. As a new method, unsymmetrical diamide can produced by the reaction of the title compounds with diacid chloride.展开更多
The effect of metallic cations on the Si-O(br) bond and the Si-O(ter) bond was studied with CNDO/2 MO calculations. The characteristics of them were discussed, which were found to vary with the bonding and coordi nati...The effect of metallic cations on the Si-O(br) bond and the Si-O(ter) bond was studied with CNDO/2 MO calculations. The characteristics of them were discussed, which were found to vary with the bonding and coordi nation situation of oxygen as well as the effect of metallic cations on oxygen. The conclusions obtained may be well used in the fields of mineralogy, geochemistry, silicate materials, pyrometallurgy and so on.展开更多
基金National Natural Science Foundation of China(Nos.62004087,12164051)Natural Science Foundation of Fujian Province(No.2020J01815)the Natural Science Foundation of Zhangzhou(No.ZZ2020J32).
文摘Bonding of Si 3N 4 ceramic was performed with Y 2O 3 Al 2O 3 SiO 2(YAS) X glass solders,which were mixed with TiO 2 (YT) and Si 3N 4 (YN), respectively. The effects of bonding conditions and interfacial reaction on the joint strength were studied. The joint strength in different bonding conditions was measured by four point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that with the increase of bonding temperature and holding time, the joint strength increases reaching a peak, and then decreases. When TiO 2 is put into YAS solder,the bonding interface with Si 3N 4/(Y Sialon glass+TiN)/TiN/Y Sialon glass is formed. When YAS solder is mixed with Si 3N 4 powder, the interfacial residual thermal stress may be decreased, and then the joint strength is enhanced. According to microanalyses, the bonding strength is related to interfacial reaction.
基金financially supported by the Beijing Municipal Science & Technology Commission (No. Z171100002217048)the National Natural Science Foundation of China (No. 51705489)
文摘Diffusion bonding of refractory Nb–Si-based alloy was performed with Ni/Al and Ti/Al nanolayers under the condition of 1473 K/30 MPa/60 min.The NbSS/Nb5Si3 in situ composite with the nominal composition of Nb–22 Ti–16 Si–3 Cr–3 Al–2 Hf was used as the parent material.The joint microstructures were examined by using a scanning electron microscope equipped with an X-ray energy dispersive spectrometer.Shear test was conducted for the bonded joints at room temperature.Within the joint bonded with Ni/Al multilayer,element diffusion occurred between the base metal and the nanolayer,with the reaction products of AlNb2+Ni3 Al,NiAl and AlNi2 Ti phases.The average shear strength was 182 MPa.While using Ti/Al multilayer,the interface mainly consisted of TiAl,(Ti,Nb)Al and(Ti,Nb)2 Al phases,and the corresponding joints exhibited an increased strength of 228 MPa.In this case,the fracture mainly took place in the TiAl phase and presented a typical brittle characteristic.
基金supported financially by the National Natural Science Foundation of China (Nos. 51471013 and 51571004)
文摘Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced using different processing parameters, including powder size, laser power, scanning speed and hatch distance. Results showed that the pre-alloyed powders ranging from 45 to 75 lm were more applicable to SLM with less balling tendency, in comparison with those between 75 and 180 lm. The increase in linear energy density（LED） resulted in the decrease in contact angle and the increase in the width of single track as well as its penetration depth into the substrate. Smaller hatch distance leaded to a larger remelted part of the former track and a higher volumetric laser energy density. With a thickness of 75.6 lm, an interfacial intermediate layer, enriched in Ti and depleted in Nb, Si, Cr and Al, was formed between the SLM part and the Ti6Al4V substrate. The mechanisms of the elimination of balling phenomenon by employing a higher LED and the interfacial bonding characteristics between Nb–Si-based alloys via SLM and the Ti6Al4V substrate were discussed.
文摘The bonding performance between synthetic diamond grit and adhesive ( Co-Si alloy) in polycrystalline diamond compact ( PDC) has been investigated. The results indicate that the carbide-forming element Si diffuses towards the diamond grit and the quantity of Si element in the inter layer of diamond grit-adhesives is about two times higher than that in the other area. New compound SiC exists in the inter layer of diamond-adhesives. The formation of SiC enhances the strength and prolongs the service life of PDC. The sintering time is important to the formation of SiC.
文摘A new set of technique was adopted in bonding Si-Si by using Ge (Ⅳ element),which is used as the substitute for the common hydrophilic method. The bond layer has no holes, and the edge bond-rate amounts to above 98%, and the bond strength is above 2156 Pa. By doping the same kind of dopant with low-resistance in Ge, the stress compensation was realized.
文摘Liquid bonding of Si 3N 4 ceramic composite was carried out with RE 2O 3 Al 2O 3 SiO 2 glass solders. The effect of bonding conditions and interfacial reaction on the joint strength was studied. The joint strength under different bonding conditions was measured by four point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that the liquid glass solders react with Si 3N 4 at interface, forming the Si 3N 4/Si 2N 2O/Y(La) sialon glass/Y(La) sialon glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increased reaching a peak, and then decreased. According to microanalyses, LaYO 3 precipitated from joint glass improves joint strength at room and high temperature.
文摘Solid liquid state pressure bonding of Si 3N 4 ceramics with aluminum based alloys, which contain a small amount of intermetallic compounds Al 3Ti or Al 3Zr, was investigated. With this new method, the heat resistant properties of the bonding zone metal are improved, and the joints’ strengths at high temperature is increased. The joints’ shear strength at room temperature and at 600 ℃ reach 126～133 MPa and 32～34 MPa, respectively, with suitable bonding pressure. The reaction between aluminum and Si 3N 4 ceramics, which produces Al Si N O type compounds is the dominant interfacial reaction, while the reactions between the second active element Ti or Zr in the aluminum based alloys and Si 3N 4 ceramics also occur to some extend. [
基金financially supported by the National Natural Science Foundation of China (Nos. 51678049 and 51834001)
文摘This paper reports a study on the reconstruction of broken Si O Si bonds in iron ore tailings (IOTs) in concrete. Limestone and IOTs were used to investigate the influence of different types of coarse aggregates on the compressive strengths of concrete samples. The dif- ferences in interfacial transition zones (ITZs) between aggregate and paste were analyzed by scanning electron microscopy (SEM) and ener- gy-dispersive spectroscopy (EDS). Meanwhile, X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to study microscopic changes in limestone and IOTs powders in a simple alkaline environment that simulated cement. The results show that the compressive strengths of IOTs concrete or paste are higher than those of limestone concrete or paste under identical conditions. The Ca/Si atom ratios in the ITZs of IOTs con- crete samples are lower than those of limestone concrete;the diffraction peak of the calcium silicate phase at 2θ = 29.5°, as well as the bands of Si O bonds shifting to lower wavenumbers, indicates reconstruction of the broken Si-O-Si bonds on the surfaces of IOTs with Ca(OH)2.
文摘Three kinds of polysilanes containing Si-H bond, ■CH_3SiCH_3■_x■CH_3SiH■_y■_n and■PhSiPh■_π■CH_3SiH■_y■CH_3SiCH_3■, have been synthesized. The structures of these copolymers were investigated by IR, ~1H-NMR and ^(13)C-NMR and their molecular weights were measured.
文摘Seven unsymmetrical diaminodimethylsilanes were prepared. The reactions of these silylamine with benzoyl chloride indicated that in comparison with electronic, the steric effect played more important role on the reactivity of Si-N bond. As a new method, unsymmetrical diamide can produced by the reaction of the title compounds with diacid chloride.
文摘The effect of metallic cations on the Si-O(br) bond and the Si-O(ter) bond was studied with CNDO/2 MO calculations. The characteristics of them were discussed, which were found to vary with the bonding and coordi nation situation of oxygen as well as the effect of metallic cations on oxygen. The conclusions obtained may be well used in the fields of mineralogy, geochemistry, silicate materials, pyrometallurgy and so on.
