A process methodology has been adopted to transfer GaN thin films grown on sapphire substrates to Si substrates using metal bonding and laser lift-off techniques. After bonding, a single KrF （248 nm） excimer laser p...A process methodology has been adopted to transfer GaN thin films grown on sapphire substrates to Si substrates using metal bonding and laser lift-off techniques. After bonding, a single KrF （248 nm） excimer laser pulse was directed through the transparent sapphire substrates followed by low-temperature heat treatment to remove the substrates. The influence of bonding temperature and energy density of the excimer laser on the structure and optical properties of GaN films were investigated systemically. Atomic force microscopy, X-ray diffraction and photoluminescence measurements showed that （1） the quality of the GaN film was higher at a lower bonding temperature and lower energy density; （2） the threshold of the energy density of the excimer laser lift-off GaN was 300 mJ/cm^2. The root-mean-square roughness of the transferred GaN surface was about 50 nm at a bonding temperature of 400 ℃.展开更多
The precise identification of metal-metal bonds is critical to fully understanding the nature of metal-metal bonding but remains a fundamental challenge.Herein,we show the essence of Sc-Sc bonds with a metal-metal dis...The precise identification of metal-metal bonds is critical to fully understanding the nature of metal-metal bonding but remains a fundamental challenge.Herein,we show the essence of Sc-Sc bonds with a metal-metal distance of 3.36 Å in a C_(3v)(8)-C_(82) fullerene cage using crystallography.展开更多
The porcelain fracture caused by low metal-ceramic bond strength is a critical issue in porcelain fused to metal（PFM） restorations. Surface roughening methods, such as sand blasting, acid etching and alkaline degrea...The porcelain fracture caused by low metal-ceramic bond strength is a critical issue in porcelain fused to metal（PFM） restorations. Surface roughening methods, such as sand blasting, acid etching and alkaline degreasing for the metal matrix are used to increase bond strength. However, the metal matrix of PFM processed by selective laser melting（SLM） has natural rough surface. To explore the effect of the original roughness on metal-ceramic bond strength, two groups of specimen are fabricated by SLM. One group of specimen surface is polished smooth while another group remains the original rough surface. The dental porcelain is fused to the specimens＇ surfaces according to the ISO 9693：1999 standard. To gain the bond strength, a three-point bending test is carried out and X ray energy spectrum analysis（EDS）, scanning electron microscope（SEM） are used to show fracture mode. The results show that the mean bond strength is 116.5 16 MPa of the group with rough surface（Ra= 17.2）, and the fracture mode is cohesive. However, when the surface is smooth （Ra =3.8）, the mean bond strength is 74.5 MPa _＋ 5 MPa and the fracture mode is mixed. The original surface with prominent structures formed by the partly melted powder particles, not only increases surface roughness but also significantly improves the bond strength by forming strong mechanical lock effect. Statistical analysis （Student＇s t-test） demonstrates a significant difference （p〈0.05） of the mean value of bond strength between the two groups. The experiments indicate the natural rough surface can enhance the metal-ceramic bond strength to over four times the minimum value （25 MPa） of the ISO 9693：1999 standard. It is found that the natural rough surface of SLM-made PFM can eliminate the porcelain collapse defect produced by traditional casting method in PFM restorations.展开更多
Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of micros...Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of microstructure and the distribution of the diffused elements in the bonding interface area are studied by means of SEM, EDX and XRD, and the influence of the technological factors on the bonding process is also studied. The model of 'metal-oxides-glass' of bonding structure and ions diffusion and bonding in the condition of electrical field-assisted are indicated.展开更多
The reaction of 5, 10, 15, 20-tetra-(4-pyridyl) porphyrin 1 with triruthenium dodecacarbonyl [Ru3(CO)12], zinc(II) acetate, copper(II) acetate, cobalt(II) acetate afforded complexes 2a?2d respectively. Treatment of 2a...The reaction of 5, 10, 15, 20-tetra-(4-pyridyl) porphyrin 1 with triruthenium dodecacarbonyl [Ru3(CO)12], zinc(II) acetate, copper(II) acetate, cobalt(II) acetate afforded complexes 2a?2d respectively. Treatment of 2a?2d with Merrifield’s peptide resin obtained 3a?3d. The compounds 3a?3d reacted with methyl iodide respectively gave 4a?4d. New complexes 4a?4d have been identified by IR, UV-visible spectra, and AES.展开更多
The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process...The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid diffusion (stage 1), dissolution of interlayer and base metal (stage 2), isothermal solidification (stage 3) and homogenization (stage 4). The microstructure of the joint depends on the joint formation process (distinct stages). The plastic deformation and solid diffusion in stage 1 favoure the intimate contact at interfaces and liquid layer formation. The microstructure of joint consists of aluminium solid solution, alumina particle, Al 2Cu and MgAl 2O 4 compounds in stage 2. The most pronounced feature of joint microstructure in stage 3 is the alumina particle segregation in the center of the joint. The increase of joint shear strength with increasing bonding temperature is mainly attributed to improving the fluidity and wettability of liquid phase and decreasing the amount of Al 2Cu brittle phase in the joint. The principal reason of higher bonding temperature (>600 ℃) resulting in lowering obviously the joint shear strength is the widening of alumina particle segregation region that acts as a preferential site for failure. The increase of joint shear strength with increasing holding time is mainly associated with decreasing the amount of Al 2Cu brittle phase and promoting homogenization of joint.展开更多
Intermetallics TiAl was diffusion-bonded to steel 40Cr in vacuum furnace with interlayer V/Cu. The results show that infinite sosoloid that made for bond performance is formed at the interface of V/Cu and Cu/40Cr, and...Intermetallics TiAl was diffusion-bonded to steel 40Cr in vacuum furnace with interlayer V/Cu. The results show that infinite sosoloid that made for bond performance is formed at the interface of V/Cu and Cu/40Cr, and three acting layers are formed at the interface of TiAl/V including Ti 3Al layer at TiAl side, intermittent V 5Al 8 layer in the middle and Ti-V sosoloid at V side. Fragile reactors V 5Al 8 arising at the interface lead to bad performance of joints, and the strength of the joint is 200 MPa, while it was still higher than the strength of the joint intermetallics TiAl to 40Cr steel diffusion-bonded directly. Intermetallic TiAl and 40Cr steel are diffusion-bonded successfully by using a composite isolation layer V/Cu.展开更多
Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the ...Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).展开更多
Aromatic bond including metallic atom (Ni) is investigated by EHMO calculation.The NMR spectra and the mechanism for hydrolysis are discussed on the ground of results of computation.
Based on ANSYS FEM software, the distribution of residual stress in the diffusion bonding joints between Ti（ C,N） metallic ceramic/interlayer/4OCr steel was calculated and experimentally ver^ed. The results showed t...Based on ANSYS FEM software, the distribution of residual stress in the diffusion bonding joints between Ti（ C,N） metallic ceramic/interlayer/4OCr steel was calculated and experimentally ver^ed. The results showed that the trend on the distribution of residual stress field in the joints was not changed with the use of interlayer. The maximum residual stress was always located in metallic ceramic with area ranging from 1 mm to 4 mm to the interlayer. The maximum residual stress in the joints was also affected by diffusion temperature. The satellite pulse current during the initial stage on diffusion bonding can promote the formation of liquid film at the interface, by which diffusion temperature and loading pressure can be greatly decreased. The crack initiation was easily produced at the corner of Ti （ C, N） metallic ceramic close to the interlayer. If a higher residual stress produced in the joints, the crack was propagated into the whole ceramic.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
RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, sp...RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, space group I43d (No.220), Pearson code cI40. The unit cell parameters are: Nd 3Cu 3Sb 4: a =0 96749(1) nm, V =0 90561(3) nm 3; Sm 3Cu 3Sb 4: a =0 96145(1) nm, V =0 88875(3) nm 3; Tb 3Cu 3Sb 4: a =0 95362(1) nm, V =0 86721(3) nm 3; Dy 3Cu 3Sb 4: a =0 95088(1) nm, V =0 85975(3) nm 3; Ho 3Cu 3Sb 4: a =0 9488(2) nm, V =0 8541(5) nm 3; Z =4. The structures are characterized by covalent bonded Cu Sb tetrahedra which form three dimensional networks by sharing corners. The rare earth atoms are distributed in the cages. The formula with the charge balance can be written as RE 3+ 3Cu 1+ 3Sb 3- 4 which are metallic Zintl phases having the weak metallic conductivity. The bonds have typical transitional features. General atomic coordination environment rules are followed. The unit cell parameters show the lanthanide contraction.展开更多
Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times fro...Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times from 5 min to 50 min at bonding temperature of 510 ℃ , the average concentration of copper in the bonded zone decreased, the microstructure in the zone changed from Cu, α-Mg and CuMg2 to α-Mg, CuMg2 and TiC, and mechanical properties of the joint increased. The shear strength of the joint bonded at 510 ℃ for 50 min reached 64 MPa due to the metallurgical bonding of the joint and improving its homogeneity of composition and microstructure. It is favorable to increase the bonding time for improving mechanical properties of TLP bonded magnesium MMC joint.展开更多
Field assisted diffusion bonding applied in the joining of solid electrolyte borosilicate glass, β ″ Al 2O 3, Y 2O ZrO 2 to monocrystal silicate and aluminum were proceeded with bonding machine in the assistance of ...Field assisted diffusion bonding applied in the joining of solid electrolyte borosilicate glass, β ″ Al 2O 3, Y 2O ZrO 2 to monocrystal silicate and aluminum were proceeded with bonding machine in the assistance of static electric field. TEM, SEM, XRD and other means were applied to investigate and analyze microstructure of interface. It is supposed that the interfacial area is a model of metal oxides ceramic, and the joining mechanism is solid diffusion joining and static electric bonding. The process of ions migration and accumulation under electric field is the most essential factor for the anodic oxidation and interfacial joining. Temperature and voltage are the basic factors of the solid diffusion bonding of interfacial oxidation. And voltage, temperature, pressure and the condition of surface are the most important factors that govern the bonding process.展开更多
The reaction of pyrrole with 4-hydroxybenzaldehyde and 4-pyridinecarboxaldehyde afforded new porphyrin ligand 1. Treatment of 1 with copper( II ) acetate, cobalt ( II ) acetate gave complexes 2-3 respectively. 2 and 3...The reaction of pyrrole with 4-hydroxybenzaldehyde and 4-pyridinecarboxaldehyde afforded new porphyrin ligand 1. Treatment of 1 with copper( II ) acetate, cobalt ( II ) acetate gave complexes 2-3 respectively. 2 and 3 reacted with Merrifield's peptide resin produced 4 and 5. Complexes 4 and 5 reacted with methyl iodide respectively gave 6-7. The new compounds 1-7 have been identified by H-1 NMR, IR, MS and UV-visible spectra, elemental analysis and AES.展开更多
The diffusion bonding was carried out to join Ti alloy （Ti-6Al-4V） and tin-bronze （ ZQSn10-10 ） with Ni and Ni ＋ Cu interlayer. The microstructures of the diffusion bonded joints were analyzed by scanning electr...The diffusion bonding was carried out to join Ti alloy （Ti-6Al-4V） and tin-bronze （ ZQSn10-10 ） with Ni and Ni ＋ Cu interlayer. The microstructures of the diffusion bonded joints were analyzed by scanning electron microscope （SEM）, energy dispersive spectroscopy （ EDS ） and X-ray diffraction （ XRD ）. The results show that when the interlayer is Ni or Ni ＋ Cu transition metals both could effectively prevent the diffusion between Ti and Cu and avoid the formation of the Cu-Ti intermetallic compounds （Cu3Ti, CuTi etc. ）. But the Ni-Ti intermetallic compounds （NiTi, Ni3Ti） are formed on the Ti-6Al-4V/Ni interface. When the interlayer is Ni, the optimum bonding parameters are 830 ℃/10 MPa/30 min. And when the interlayer is Ni ＋ Cu, the optimum bonding parameters are 850 ℃/10 MPa/20 min. With the optimum bonding parameters, the tensile strength of the joints with Ni and Ni ＋ Cu interlayer both are 155.8 MPa, which is 65 percent of the strength of ZQSn10-10 base metal.展开更多
Some functional lanthanide metal complexes, such as acetylacetonato complexes, ethylenediaminetetraacetato complexes, were successfully applied for diagnostic technique. The authors are interested in investigating the...Some functional lanthanide metal complexes, such as acetylacetonato complexes, ethylenediaminetetraacetato complexes, were successfully applied for diagnostic technique. The authors are interested in investigating the structure and bonding in lanthanide and actinide metal complexes using 166Er, t55Gd, and 237Np Mtissbauer spectroscopies in connection with single-crystal and/or powder X-ray diffraction, making clear the differences on their structures as well as the differences in the participation of 4f and 5f orbitals in the chemical bonds. In this article, the crystal structures of two novel Gd（Ⅲ） acetylacetonato complexes, Gd（pta）3 · 2H2O （pta = 1,1,1 -trifluoro-5,5-dimethy 1-2,4-hexanedione） and Gd（bfa）3 · 2H2O （bfa = 1, 1, 1 -trifluoro-4-phenyl-2-4-butanedione） were reported. Though both of them were dihydrate and had distorted square antiprismatical structure, Gd（pta）3 · 2H2O crystallizes in the P 2 1/n （#14） monoclinic space group and its lattice parameters are a = 1.4141（6） nm, b = 1.0708（3） nm, c =2.2344（4） nm, β =952.4（2）°, and Gd（bfa）3· 2H2O crystallizes in P 212121 orthorhombic space group and its lattice parameters were a = 1.322 （1） nm, b = 2.295 （1） nm, c = 1. 0786（8） nm. In the meantime, the authors had finished a systematic investigation on the ^155Gd Mossbauer isomer shift （δ） of various Gd（Ⅲ） metal complexes having a different coordination number （C.N.） and different ratios coordinating oxygen to nitrogen. A tendency for the 6 value to decrease with an increase in the C.N, and the number of the nitrogen atom coordinating to Gd was confirmed. This indicated that the Gd-O and/or Gd-N bond in the investigated Gd（Ⅲ） metal complexes had a small covalent contribution, which was possible to be deduced from the O and/or N atoms of the lisands donating electrons to 6s, 5d, and 4f orbitals of Gd.展开更多
The geometric and electronic structures of scandium carbonitride endofullerene Sc3CN@C2n （2n=68, 78, 80, 82, and 84） and Sc（Y）NC@C76 have been systematically investigated to identify the preferred position of inte...The geometric and electronic structures of scandium carbonitride endofullerene Sc3CN@C2n （2n=68, 78, 80, 82, and 84） and Sc（Y）NC@C76 have been systematically investigated to identify the preferred position of internal C and N atoms by density functional theory （DFT） calculations combined with statistical mechanics treatments. The CN bond orientation can generally be inferred from the molecule stability and electronic configuration. It is found that Sc3CN@C2n molecules have the most stable structure with C atom locating at the center of Sc3CN cluster. The CN bond has trivalent form of[CN]3- and connects with adjacent three Sc atoms tightly. However, in Sc（Y）NC@C76 with[NC]-, the N atom always resides in the center of the whole molecule. In addition, the stability of Sc3CN@C2n has been further compared in terms of the organization of the corresponding molecular energy level. The structural differences between Sc3CN@C2n and Sc3NC@C2n are highlighted by their respected infrared spectra.展开更多
基金supported by the National Natural Science Foundation of China(Nos.50672079,60676027,60837001,60776007)the State Key Development Program for Basic Research of China(No.2007CB613404)+1 种基金the Natural Science Foundation of Fujian Province (No.2008J 0221)the Science and Technology Program of the Educational Office of Fujian Province(No.JB08215)
文摘A process methodology has been adopted to transfer GaN thin films grown on sapphire substrates to Si substrates using metal bonding and laser lift-off techniques. After bonding, a single KrF （248 nm） excimer laser pulse was directed through the transparent sapphire substrates followed by low-temperature heat treatment to remove the substrates. The influence of bonding temperature and energy density of the excimer laser on the structure and optical properties of GaN films were investigated systemically. Atomic force microscopy, X-ray diffraction and photoluminescence measurements showed that （1） the quality of the GaN film was higher at a lower bonding temperature and lower energy density; （2） the threshold of the energy density of the excimer laser lift-off GaN was 300 mJ/cm^2. The root-mean-square roughness of the transferred GaN surface was about 50 nm at a bonding temperature of 400 ℃.
基金Financial support for this research was provided by the National Natural Science Foundation of China(nos.92061204,21771152,and 21721001).
文摘The precise identification of metal-metal bonds is critical to fully understanding the nature of metal-metal bonding but remains a fundamental challenge.Herein,we show the essence of Sc-Sc bonds with a metal-metal distance of 3.36 Å in a C_(3v)(8)-C_(82) fullerene cage using crystallography.
基金supported by the Royal Academy of Engineering Research Exchanges with China and UK(Grant No.2012-P02)National Key Technology R&D Program of Ministry of Science and Technology of China(Grant No.2012BAF08B03)National Natural Science Foundation of China(Grant No.51375189)
文摘The porcelain fracture caused by low metal-ceramic bond strength is a critical issue in porcelain fused to metal（PFM） restorations. Surface roughening methods, such as sand blasting, acid etching and alkaline degreasing for the metal matrix are used to increase bond strength. However, the metal matrix of PFM processed by selective laser melting（SLM） has natural rough surface. To explore the effect of the original roughness on metal-ceramic bond strength, two groups of specimen are fabricated by SLM. One group of specimen surface is polished smooth while another group remains the original rough surface. The dental porcelain is fused to the specimens＇ surfaces according to the ISO 9693：1999 standard. To gain the bond strength, a three-point bending test is carried out and X ray energy spectrum analysis（EDS）, scanning electron microscope（SEM） are used to show fracture mode. The results show that the mean bond strength is 116.5 16 MPa of the group with rough surface（Ra= 17.2）, and the fracture mode is cohesive. However, when the surface is smooth （Ra =3.8）, the mean bond strength is 74.5 MPa _＋ 5 MPa and the fracture mode is mixed. The original surface with prominent structures formed by the partly melted powder particles, not only increases surface roughness but also significantly improves the bond strength by forming strong mechanical lock effect. Statistical analysis （Student＇s t-test） demonstrates a significant difference （p〈0.05） of the mean value of bond strength between the two groups. The experiments indicate the natural rough surface can enhance the metal-ceramic bond strength to over four times the minimum value （25 MPa） of the ISO 9693：1999 standard. It is found that the natural rough surface of SLM-made PFM can eliminate the porcelain collapse defect produced by traditional casting method in PFM restorations.
基金This project is supported by Foundation of Taiyuan University of Technology "211" Project, China (No.20304006).
文摘Investigations of technological characteristics and bonding mechanism of field-assisted bonding are done, which are for bonding of electrolytes (Pyrex glass) to monocrystal silicon and aluminum. The features of microstructure and the distribution of the diffused elements in the bonding interface area are studied by means of SEM, EDX and XRD, and the influence of the technological factors on the bonding process is also studied. The model of 'metal-oxides-glass' of bonding structure and ions diffusion and bonding in the condition of electrical field-assisted are indicated.
文摘The reaction of 5, 10, 15, 20-tetra-(4-pyridyl) porphyrin 1 with triruthenium dodecacarbonyl [Ru3(CO)12], zinc(II) acetate, copper(II) acetate, cobalt(II) acetate afforded complexes 2a?2d respectively. Treatment of 2a?2d with Merrifield’s peptide resin obtained 3a?3d. The compounds 3a?3d reacted with methyl iodide respectively gave 4a?4d. New complexes 4a?4d have been identified by IR, UV-visible spectra, and AES.
文摘The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid diffusion (stage 1), dissolution of interlayer and base metal (stage 2), isothermal solidification (stage 3) and homogenization (stage 4). The microstructure of the joint depends on the joint formation process (distinct stages). The plastic deformation and solid diffusion in stage 1 favoure the intimate contact at interfaces and liquid layer formation. The microstructure of joint consists of aluminium solid solution, alumina particle, Al 2Cu and MgAl 2O 4 compounds in stage 2. The most pronounced feature of joint microstructure in stage 3 is the alumina particle segregation in the center of the joint. The increase of joint shear strength with increasing bonding temperature is mainly attributed to improving the fluidity and wettability of liquid phase and decreasing the amount of Al 2Cu brittle phase in the joint. The principal reason of higher bonding temperature (>600 ℃) resulting in lowering obviously the joint shear strength is the widening of alumina particle segregation region that acts as a preferential site for failure. The increase of joint shear strength with increasing holding time is mainly associated with decreasing the amount of Al 2Cu brittle phase and promoting homogenization of joint.
文摘Intermetallics TiAl was diffusion-bonded to steel 40Cr in vacuum furnace with interlayer V/Cu. The results show that infinite sosoloid that made for bond performance is formed at the interface of V/Cu and Cu/40Cr, and three acting layers are formed at the interface of TiAl/V including Ti 3Al layer at TiAl side, intermittent V 5Al 8 layer in the middle and Ti-V sosoloid at V side. Fragile reactors V 5Al 8 arising at the interface lead to bad performance of joints, and the strength of the joint is 200 MPa, while it was still higher than the strength of the joint intermetallics TiAl to 40Cr steel diffusion-bonded directly. Intermetallic TiAl and 40Cr steel are diffusion-bonded successfully by using a composite isolation layer V/Cu.
文摘Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).
文摘Aromatic bond including metallic atom (Ni) is investigated by EHMO calculation.The NMR spectra and the mechanism for hydrolysis are discussed on the ground of results of computation.
基金The authors are grateful to the financial support for this research from National Natural Science Foundation of China （Grant No. 51175259） , Jiangsu Science and Technology Planning Project （No. BK2011494） and University Science Research Project of Jiangsu Province （ 11KJAd30005 ）.
文摘Based on ANSYS FEM software, the distribution of residual stress in the diffusion bonding joints between Ti（ C,N） metallic ceramic/interlayer/4OCr steel was calculated and experimentally ver^ed. The results showed that the trend on the distribution of residual stress field in the joints was not changed with the use of interlayer. The maximum residual stress was always located in metallic ceramic with area ranging from 1 mm to 4 mm to the interlayer. The maximum residual stress in the joints was also affected by diffusion temperature. The satellite pulse current during the initial stage on diffusion bonding can promote the formation of liquid film at the interface, by which diffusion temperature and loading pressure can be greatly decreased. The crack initiation was easily produced at the corner of Ti （ C, N） metallic ceramic close to the interlayer. If a higher residual stress produced in the joints, the crack was propagated into the whole ceramic.
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.
文摘RE 3Cu 3Sb 4(RE=Nd, Sm, Tb, Dy, Ho) was synthesized by arc melting method and their crystal structures were characterized by powder X ray method. The compounds crystallize in cubic system, Y 3Au 3Sb 4 type, space group I43d (No.220), Pearson code cI40. The unit cell parameters are: Nd 3Cu 3Sb 4: a =0 96749(1) nm, V =0 90561(3) nm 3; Sm 3Cu 3Sb 4: a =0 96145(1) nm, V =0 88875(3) nm 3; Tb 3Cu 3Sb 4: a =0 95362(1) nm, V =0 86721(3) nm 3; Dy 3Cu 3Sb 4: a =0 95088(1) nm, V =0 85975(3) nm 3; Ho 3Cu 3Sb 4: a =0 9488(2) nm, V =0 8541(5) nm 3; Z =4. The structures are characterized by covalent bonded Cu Sb tetrahedra which form three dimensional networks by sharing corners. The rare earth atoms are distributed in the cages. The formula with the charge balance can be written as RE 3+ 3Cu 1+ 3Sb 3- 4 which are metallic Zintl phases having the weak metallic conductivity. The bonds have typical transitional features. General atomic coordination environment rules are followed. The unit cell parameters show the lanthanide contraction.
文摘Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times from 5 min to 50 min at bonding temperature of 510 ℃ , the average concentration of copper in the bonded zone decreased, the microstructure in the zone changed from Cu, α-Mg and CuMg2 to α-Mg, CuMg2 and TiC, and mechanical properties of the joint increased. The shear strength of the joint bonded at 510 ℃ for 50 min reached 64 MPa due to the metallurgical bonding of the joint and improving its homogeneity of composition and microstructure. It is favorable to increase the bonding time for improving mechanical properties of TLP bonded magnesium MMC joint.
文摘Field assisted diffusion bonding applied in the joining of solid electrolyte borosilicate glass, β ″ Al 2O 3, Y 2O ZrO 2 to monocrystal silicate and aluminum were proceeded with bonding machine in the assistance of static electric field. TEM, SEM, XRD and other means were applied to investigate and analyze microstructure of interface. It is supposed that the interfacial area is a model of metal oxides ceramic, and the joining mechanism is solid diffusion joining and static electric bonding. The process of ions migration and accumulation under electric field is the most essential factor for the anodic oxidation and interfacial joining. Temperature and voltage are the basic factors of the solid diffusion bonding of interfacial oxidation. And voltage, temperature, pressure and the condition of surface are the most important factors that govern the bonding process.
文摘The reaction of pyrrole with 4-hydroxybenzaldehyde and 4-pyridinecarboxaldehyde afforded new porphyrin ligand 1. Treatment of 1 with copper( II ) acetate, cobalt ( II ) acetate gave complexes 2-3 respectively. 2 and 3 reacted with Merrifield's peptide resin produced 4 and 5. Complexes 4 and 5 reacted with methyl iodide respectively gave 6-7. The new compounds 1-7 have been identified by H-1 NMR, IR, MS and UV-visible spectra, elemental analysis and AES.
基金The work was supported by National Natural Science Foundation of China(No50375065)State Key Laboratory of Advanced Welding Production Technology(No04005)
文摘The diffusion bonding was carried out to join Ti alloy （Ti-6Al-4V） and tin-bronze （ ZQSn10-10 ） with Ni and Ni ＋ Cu interlayer. The microstructures of the diffusion bonded joints were analyzed by scanning electron microscope （SEM）, energy dispersive spectroscopy （ EDS ） and X-ray diffraction （ XRD ）. The results show that when the interlayer is Ni or Ni ＋ Cu transition metals both could effectively prevent the diffusion between Ti and Cu and avoid the formation of the Cu-Ti intermetallic compounds （Cu3Ti, CuTi etc. ）. But the Ni-Ti intermetallic compounds （NiTi, Ni3Ti） are formed on the Ti-6Al-4V/Ni interface. When the interlayer is Ni, the optimum bonding parameters are 830 ℃/10 MPa/30 min. And when the interlayer is Ni ＋ Cu, the optimum bonding parameters are 850 ℃/10 MPa/20 min. With the optimum bonding parameters, the tensile strength of the joints with Ni and Ni ＋ Cu interlayer both are 155.8 MPa, which is 65 percent of the strength of ZQSn10-10 base metal.
基金Project supported by the Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan andin Part by the Inter-University Joint Research Program for the Common Use of JAERI (Japan Atomic Energy Research Institute)Facilities
文摘Some functional lanthanide metal complexes, such as acetylacetonato complexes, ethylenediaminetetraacetato complexes, were successfully applied for diagnostic technique. The authors are interested in investigating the structure and bonding in lanthanide and actinide metal complexes using 166Er, t55Gd, and 237Np Mtissbauer spectroscopies in connection with single-crystal and/or powder X-ray diffraction, making clear the differences on their structures as well as the differences in the participation of 4f and 5f orbitals in the chemical bonds. In this article, the crystal structures of two novel Gd（Ⅲ） acetylacetonato complexes, Gd（pta）3 · 2H2O （pta = 1,1,1 -trifluoro-5,5-dimethy 1-2,4-hexanedione） and Gd（bfa）3 · 2H2O （bfa = 1, 1, 1 -trifluoro-4-phenyl-2-4-butanedione） were reported. Though both of them were dihydrate and had distorted square antiprismatical structure, Gd（pta）3 · 2H2O crystallizes in the P 2 1/n （#14） monoclinic space group and its lattice parameters are a = 1.4141（6） nm, b = 1.0708（3） nm, c =2.2344（4） nm, β =952.4（2）°, and Gd（bfa）3· 2H2O crystallizes in P 212121 orthorhombic space group and its lattice parameters were a = 1.322 （1） nm, b = 2.295 （1） nm, c = 1. 0786（8） nm. In the meantime, the authors had finished a systematic investigation on the ^155Gd Mossbauer isomer shift （δ） of various Gd（Ⅲ） metal complexes having a different coordination number （C.N.） and different ratios coordinating oxygen to nitrogen. A tendency for the 6 value to decrease with an increase in the C.N, and the number of the nitrogen atom coordinating to Gd was confirmed. This indicated that the Gd-O and/or Gd-N bond in the investigated Gd（Ⅲ） metal complexes had a small covalent contribution, which was possible to be deduced from the O and/or N atoms of the lisands donating electrons to 6s, 5d, and 4f orbitals of Gd.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21503208,61604104,and 51002102)the Natural Science Foundation of Shanxi Province,China(Grant Nos.2015011034,201601D202034,and 201601D202029)the Natural Science Foundation Project of Chongqing Science and Technology Commission,China(Grant No.cstc2014jcyj A00032)
文摘The geometric and electronic structures of scandium carbonitride endofullerene Sc3CN@C2n （2n=68, 78, 80, 82, and 84） and Sc（Y）NC@C76 have been systematically investigated to identify the preferred position of internal C and N atoms by density functional theory （DFT） calculations combined with statistical mechanics treatments. The CN bond orientation can generally be inferred from the molecule stability and electronic configuration. It is found that Sc3CN@C2n molecules have the most stable structure with C atom locating at the center of Sc3CN cluster. The CN bond has trivalent form of[CN]3- and connects with adjacent three Sc atoms tightly. However, in Sc（Y）NC@C76 with[NC]-, the N atom always resides in the center of the whole molecule. In addition, the stability of Sc3CN@C2n has been further compared in terms of the organization of the corresponding molecular energy level. The structural differences between Sc3CN@C2n and Sc3NC@C2n are highlighted by their respected infrared spectra.
