A hydrophobic coating of the silica fiber reinforced silica composites(SiO2f/SiO2) was synthesized by sol-gel method using methyltriethoxy-silane(MTES) and boric acid(B(OH)3) as raw materials. The relationship among b...A hydrophobic coating of the silica fiber reinforced silica composites(SiO2f/SiO2) was synthesized by sol-gel method using methyltriethoxy-silane(MTES) and boric acid(B(OH)3) as raw materials. The relationship among boron doping, chemical structure of precursors and durability of hydrophobic coatings was discussed. The Si-O-B and methyl groups were successfully introduced in the gel precursors according to the FT-IR and XPS results. The resins were filled in the internal and surface holes of the SiO2f/SiO2 composites partially or completely, which is beneficial to reduce the physical adsorption of the moisture. In addition, hydroxyl groups of the SiO2f/SiO2 composites reacted with the resins and hydrophobic methyl groups were introduced, leading to the reduction of the chemical adsorption of water. Also, the boron doping was beneficial to enhancing the physical cross-linking between the coating and the SiO2f/SiO2 composites, and improved the adhesion of the coating to the substrate. The results show that the optimal hydrophobic coating with contact angle 130.33°, moisture absorption 0.33% and adhesion level 1 is obtained when the molar ratio of MTES to B(OH)3 is 10:4. The real permittivity of M10B4 is constant in the range of 2.32–2.51 and the dielectric tangent loss is constant in the range of 5.5 × 10-4–8.7 × 10-3. The hydrophobic coating has excellent dielectric properties.展开更多
The effects of various SiO2 contents on both the microstructures and properties of Ca-Ba- A1-B-Si-O glass/Al2O3 cotrtposites were investigated by FTIR, DSC, XRD and SEM. The experimental results show that increasing S...The effects of various SiO2 contents on both the microstructures and properties of Ca-Ba- A1-B-Si-O glass/Al2O3 cotrtposites were investigated by FTIR, DSC, XRD and SEM. The experimental results show that increasing SiO2 content in the glass leads to the increase of [SIO4] units, increases the continuity of glass network, and decreases the trend to crystallization of composites. The shrinkage of samples rises rapid around the glass softening temperature and the final shrinkage of samples decreases with increasing SiO2 content in the glass. Borosilicate glass/Al2O3 composites with 60wt% SiO2 sintered at 875 ℃ for 15 min show better properties： a bulk density of 3.10 g,cm-3, a porosity of 0.23 %, a er value of 7.55 and a tan 8 value of 0.00053 （measured at 10 MHz） and a well matching with Ag electrodes.展开更多
Porous silica ceramics has been prepared with the starch consolidation casting method. Slurries with various fractions of starch added in were prepared by ball-milling. The evaluation of the microstructures was done t...Porous silica ceramics has been prepared with the starch consolidation casting method. Slurries with various fractions of starch added in were prepared by ball-milling. The evaluation of the microstructures was done through two techniques： Hg porosimetry and SEM investigation. The bending strength of the sintered samples varied within the range of 10 MPa-20 MPa and the low dielectric constant within the range of 2.0-2.4 correspondent with the porosity of 42%-56%. The ceramics holds a brilliant promise of being a kind of core material used in sandwich-like electromagnetic windows.展开更多
Geopolymers,such as phosphate-based geopolymer,are promising materials that have drawn extensive attentions as wave-transparent candidates with low dielectric loss factor.In this paper,multilayer SiO2fibers are introd...Geopolymers,such as phosphate-based geopolymer,are promising materials that have drawn extensive attentions as wave-transparent candidates with low dielectric loss factor.In this paper,multilayer SiO2fibers are introduced into phosphate-based geopolymer matrix to prepare composites.Crack generation and fracture behaviors during the three-point bending tests in as-prepared SiO2f/phosphate geopolymer composites are clarified by in situ observation Before high-temperature treatment,composite with 17 vol%fiber content exhibits the best mechanical properties.A decreasing mechanical strength is observed after being treated at higher temperature,which is attributed to the stronger interface binging between fibers and phosphatebased geopolymer matrix.Most importantly,the presence of SiO2fibers can strengthen mechanical properties of phosphate-based geopolymer matrix but shows negligible impact on its dielectric properties,achieving dielectric loss factor as low as 3.53910-3after being treated at 700°C.展开更多
In this paper, we present a compact low-temperature co-fired ceramic（LTCC） dual-band antenna by using the electromagnetic coupling effect concept for global positioning system（GPS） and universal mobile telecommuni...In this paper, we present a compact low-temperature co-fired ceramic（LTCC） dual-band antenna by using the electromagnetic coupling effect concept for global positioning system（GPS） and universal mobile telecommunication system（UMTS） applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line,total dimension of the proposed antenna is greatly reduced. With the 2.5： voltage standing wave ratio（VSWR） impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The proposed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator（HFSS）. And the antenna is manufactured by using the 0.95Zn2SiO4-0.05 CaTiO3ceramics（εr = 7.1, tanδ = 0.00038） that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern.展开更多
Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric i...Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delami- nation is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser- induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.展开更多
The effects of the Ca0.7Nd0.2Ti O3 ceramic addition on the crystallization,densification,and dielectric properties of CaO–B2O3–SiO2–(Al2O3)glass(C1:CaO–B2O3–SiO2 glass and C1A03:CaO–B2O3–SiO2–Al2O3 glass)for l...The effects of the Ca0.7Nd0.2Ti O3 ceramic addition on the crystallization,densification,and dielectric properties of CaO–B2O3–SiO2–(Al2O3)glass(C1:CaO–B2O3–SiO2 glass and C1A03:CaO–B2O3–SiO2–Al2O3 glass)for low-temperature co-fired ceramic(LTCC)applications are investigated.The cristobalite phase crystallized from C1 glass was inhibited by adding Al2O3.During sintering,Ca0.7Nd0.2TiO3 ceramic reacted with CaO–B2O3–SiO2–(Al2O3)glass to form the sphene(CaTiSiO5)phase.The amount of sphene phase increases with increasing sintering temperature.By adding 50–60 wt%C1 or C1A03 glass,Ca0.7Nd0.2TiO3 can be densified at 850–900℃.The relative dielectric constants for Ca0.7Nd0.2TiO3 added with C1 and C1A03 glasses were all 20–23.Ca0.7Nd0.2TiO3 added with C1 glass exhibited a lower dielectric constant than C1A03 glass due to cristobalite phase formation.For Ca0.7Nd0.2TiO3 ceramics added with 50 wt%glass,the variation in Q×f value presented the same trend as the sphene formation amount variation.The best Q×f value of 2380 GHz was achieved for Ca0.7Nd0.2TiO3 ceramics added with 50 wt%C1A03 glass sintered at 900℃due to the dense structure and greater amount of sphene.Ca0.7Nd0.2TiO3 ceramics added with50 wt%C1A03 glass sintered at 900℃exhibited a dielectric constant of 22.8 and Q×f value of2380 GHz,which are suitable for microwave LTCC applications.展开更多
The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric c...The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance-voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 ℃ for 30 min, while a large num- ber of effective dielectric charges are generated. The components at the SiO2/SiC interface are analyzed by X-ray photoelectron spectroscopy （XPS） testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process.展开更多
基金supported by the Taishan Scholar Project(No.ts201511080)the National Natural Science Foundation of China(Nos.51672059,51172050,51102060 and 51302050)the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology(No.HIT.NSRIF.2014129)
文摘A hydrophobic coating of the silica fiber reinforced silica composites(SiO2f/SiO2) was synthesized by sol-gel method using methyltriethoxy-silane(MTES) and boric acid(B(OH)3) as raw materials. The relationship among boron doping, chemical structure of precursors and durability of hydrophobic coatings was discussed. The Si-O-B and methyl groups were successfully introduced in the gel precursors according to the FT-IR and XPS results. The resins were filled in the internal and surface holes of the SiO2f/SiO2 composites partially or completely, which is beneficial to reduce the physical adsorption of the moisture. In addition, hydroxyl groups of the SiO2f/SiO2 composites reacted with the resins and hydrophobic methyl groups were introduced, leading to the reduction of the chemical adsorption of water. Also, the boron doping was beneficial to enhancing the physical cross-linking between the coating and the SiO2f/SiO2 composites, and improved the adhesion of the coating to the substrate. The results show that the optimal hydrophobic coating with contact angle 130.33°, moisture absorption 0.33% and adhesion level 1 is obtained when the molar ratio of MTES to B(OH)3 is 10:4. The real permittivity of M10B4 is constant in the range of 2.32–2.51 and the dielectric tangent loss is constant in the range of 5.5 × 10-4–8.7 × 10-3. The hydrophobic coating has excellent dielectric properties.
基金Funded by the National High Technology Research and Development Program("863"Program)of China(2007AA03Z0455)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institution,the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions+1 种基金Changjiang Scholars,the Innovative Research Team in University(PCSIRT),IRT1146the Innovation Foundation for Graduate Students of Jiangsu Province China(No.CXZZ12_0415)
文摘The effects of various SiO2 contents on both the microstructures and properties of Ca-Ba- A1-B-Si-O glass/Al2O3 cotrtposites were investigated by FTIR, DSC, XRD and SEM. The experimental results show that increasing SiO2 content in the glass leads to the increase of [SIO4] units, increases the continuity of glass network, and decreases the trend to crystallization of composites. The shrinkage of samples rises rapid around the glass softening temperature and the final shrinkage of samples decreases with increasing SiO2 content in the glass. Borosilicate glass/Al2O3 composites with 60wt% SiO2 sintered at 875 ℃ for 15 min show better properties： a bulk density of 3.10 g,cm-3, a porosity of 0.23 %, a er value of 7.55 and a tan 8 value of 0.00053 （measured at 10 MHz） and a well matching with Ag electrodes.
文摘Porous silica ceramics has been prepared with the starch consolidation casting method. Slurries with various fractions of starch added in were prepared by ball-milling. The evaluation of the microstructures was done through two techniques： Hg porosimetry and SEM investigation. The bending strength of the sintered samples varied within the range of 10 MPa-20 MPa and the low dielectric constant within the range of 2.0-2.4 correspondent with the porosity of 42%-56%. The ceramics holds a brilliant promise of being a kind of core material used in sandwich-like electromagnetic windows.
基金financially supported by the National Natural Science Foundation of China(Nos.518720635150205251832002 and 51621091)。
文摘Geopolymers,such as phosphate-based geopolymer,are promising materials that have drawn extensive attentions as wave-transparent candidates with low dielectric loss factor.In this paper,multilayer SiO2fibers are introduced into phosphate-based geopolymer matrix to prepare composites.Crack generation and fracture behaviors during the three-point bending tests in as-prepared SiO2f/phosphate geopolymer composites are clarified by in situ observation Before high-temperature treatment,composite with 17 vol%fiber content exhibits the best mechanical properties.A decreasing mechanical strength is observed after being treated at higher temperature,which is attributed to the stronger interface binging between fibers and phosphatebased geopolymer matrix.Most importantly,the presence of SiO2fibers can strengthen mechanical properties of phosphate-based geopolymer matrix but shows negligible impact on its dielectric properties,achieving dielectric loss factor as low as 3.53910-3after being treated at 700°C.
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20133718120009)the Natural Science Foundation of Shandong Provence,China(Grant Nos.ZR2013FQ002 and ZR2014FQ006)+2 种基金the China Postdoctoral Science Foundation(Grant No.2014M551935)the Qingdao Municipality Postdoctoral Science Foundation,Chinathe Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents,China(Grant Nos.2013RCJJ042 and 2014RCJJ052)
文摘In this paper, we present a compact low-temperature co-fired ceramic（LTCC） dual-band antenna by using the electromagnetic coupling effect concept for global positioning system（GPS） and universal mobile telecommunication system（UMTS） applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line,total dimension of the proposed antenna is greatly reduced. With the 2.5： voltage standing wave ratio（VSWR） impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The proposed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator（HFSS）. And the antenna is manufactured by using the 0.95Zn2SiO4-0.05 CaTiO3ceramics（εr = 7.1, tanδ = 0.00038） that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern.
基金supported by the National Natural Science Foundation of China under Grant Nos.11104293and 61308021
文摘Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delami- nation is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser- induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.
基金financially supported by “the Ministry of Science and Technology” (106-2923-E-006-009-MY3)
文摘The effects of the Ca0.7Nd0.2Ti O3 ceramic addition on the crystallization,densification,and dielectric properties of CaO–B2O3–SiO2–(Al2O3)glass(C1:CaO–B2O3–SiO2 glass and C1A03:CaO–B2O3–SiO2–Al2O3 glass)for low-temperature co-fired ceramic(LTCC)applications are investigated.The cristobalite phase crystallized from C1 glass was inhibited by adding Al2O3.During sintering,Ca0.7Nd0.2TiO3 ceramic reacted with CaO–B2O3–SiO2–(Al2O3)glass to form the sphene(CaTiSiO5)phase.The amount of sphene phase increases with increasing sintering temperature.By adding 50–60 wt%C1 or C1A03 glass,Ca0.7Nd0.2TiO3 can be densified at 850–900℃.The relative dielectric constants for Ca0.7Nd0.2TiO3 added with C1 and C1A03 glasses were all 20–23.Ca0.7Nd0.2TiO3 added with C1 glass exhibited a lower dielectric constant than C1A03 glass due to cristobalite phase formation.For Ca0.7Nd0.2TiO3 ceramics added with 50 wt%glass,the variation in Q×f value presented the same trend as the sphene formation amount variation.The best Q×f value of 2380 GHz was achieved for Ca0.7Nd0.2TiO3 ceramics added with 50 wt%C1A03 glass sintered at 900℃due to the dense structure and greater amount of sphene.Ca0.7Nd0.2TiO3 ceramics added with50 wt%C1A03 glass sintered at 900℃exhibited a dielectric constant of 22.8 and Q×f value of2380 GHz,which are suitable for microwave LTCC applications.
基金Project supported by the National Natural Science Foundation of China(Nos.51272202,61234006,61274079)
文摘The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance-voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 ℃ for 30 min, while a large num- ber of effective dielectric charges are generated. The components at the SiO2/SiC interface are analyzed by X-ray photoelectron spectroscopy （XPS） testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process.
