The silica sand deposit located at km 55 Jalan Pantai Kuala Terengganu-Kuala Besut in the District of Setiu, North Terengganu consists of loose sand of fine to coarse grain size which is developed over the raised beac...The silica sand deposit located at km 55 Jalan Pantai Kuala Terengganu-Kuala Besut in the District of Setiu, North Terengganu consists of loose sand of fine to coarse grain size which is developed over the raised beaches of marine origin. The underlying bedrock is believed to be either metasediment of Late Paleozoic age or intrusive granitic rocks. The average content of SiO2 is 99.3% while for the Fe2O3, Al2O3 and TiO2, their average content are 0.1%, 0.3% and 0.2% respectively. The screen analyses show that more than 90 percent of the silica sand is within 150 to 1,180 micron size range. The total area underlain by potential silica sand is about 1.9 million sq. metres with total measured reserve about 2.6 million tonnes. According to Malaysian Standard, MS 701:1981 and British Standard BS 2975:1988, silica sand for making crystal glass should meet the grade B specification in which the purity of silica sand is not less than 99.5% with only a small amount of iron oxide (0.015%), alumina (0.05%), chromium oxide (maximum 2 ppm) and other mineral oxides. In the production of crystal glass, a front loading furnace was used and maximum melting temperature was 1400 ℃. After melting process, physical evaluation on the crystal glass products were performed pertaining to complete accomplishment of melting such as existing of bubbles inside crystal glasses. In order to ensure that crystal glass quality meets the international standard, specification for crystal glass published by British standard BS 3828:1973 was taken as a guideline. Some of the parameters are density, surface hardness and refractive index. In general, silica sand from Gong Belibis, Setiu Terengganu is suitable as a raw material for making crystal glass product.展开更多
Sm2O3 containing zinc-borosilicate glass and glass ceramics were prepared by melt quenching method, and the effect of Sm2O3 and micro-crystallization on the chemical stability of borosilicate glass was explored. DTA a...Sm2O3 containing zinc-borosilicate glass and glass ceramics were prepared by melt quenching method, and the effect of Sm2O3 and micro-crystallization on the chemical stability of borosilicate glass was explored. DTA analysis showed that the endothermic peak and exothermic peak of basic glass changed from 635 ℃ and 834 ℃ to 630 ℃ and 828 ℃ respectively as a result of the doping of Sm2O3. XRD analysis showed the promoting effect of Sm2O3 on crystallization ability of this glass. The cumulative mass loss of base glass, Sm2O3 containing glass, glass ceramic and Sm2O3 containing glass ceramic was 0.289, 0.253, 0.329, 0.269 mg/mm2 respectively after 26 days corrosion in alkali solution, and 1.293, 1.290, 0.999, 1.040 mg/mm2 respectively in acidic erosion medium. Micro-crystallization decreased and improved the alkali and acid resistance of borosilicate glass respectively, the addition of Sm2O3 increased the alkali resistance of base glass and glass ceramics, and the slight effect of Sm2O3 on the acid resistance of borosilicate glass was also observed.展开更多
BaO is the most common consideration in the preparation of newcrystal glass for getting rid of lead content in the glass andceramic wares to protect hu- man health and environment. But forkeeping the glass products...BaO is the most common consideration in the preparation of newcrystal glass for getting rid of lead content in the glass andceramic wares to protect hu- man health and environment. But forkeeping the glass products' properties to meet the requirements ofthe tradi- tional crystal glass, B_2O_3, Al_2O_3, TiO_2, SrO and ZnOetc (at a special ratio) had been researched with BaO to con- stitutea mixture to replace the lead content in the glass compositions.展开更多
The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specro...The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specrometer) and so on. Computer pattern recognition is applied to optimize the heat-treatment schedules. The experimental results show that the base glass containing more than 1 .5 % (mass fraction) Cr2O3 can be nucleated internally and converted to spheroidal crystal glass materials. The spheroidal crystal consisted of fibrous wollastonite crystals radiating from a center. The residual glass phase filled in the interstices between the fibers and between the spherulites. During heat treatment process, the valence states ofchromium changed from Cr6- to Cr3-, and the Cr-spinel solidsolution [CaCr2O4] precipitated followed this valence change. At the primary stage of crystallization, the Cr-spinel could act as a nucleating center on which the principal or}stalline phase β-CaSiO3 grew epitaxially.展开更多
In this paper the experimental results associated until the phase separation and nucleation and crystallization of chalcogenidc glasses are described. Experi-ments demonstrate that the phas separation may be affected ...In this paper the experimental results associated until the phase separation and nucleation and crystallization of chalcogenidc glasses are described. Experi-ments demonstrate that the phas separation may be affected by small amount of additives. It has been found that some chalcogenide glasses could be converted into glass-ceramics without phase separation. The different mechanisms of nucleated crystallization of chalcogenide glasses are discussed and propossed.展开更多
A micromechanism in an atomic level of crystallization of transition metal-metalloid TM(80)M(20) metallic glass is thermodynamically proposed by taking Bernal polyhedra as the starting structure of metallic glass. It ...A micromechanism in an atomic level of crystallization of transition metal-metalloid TM(80)M(20) metallic glass is thermodynamically proposed by taking Bernal polyhedra as the starting structure of metallic glass. It is composed of two competitively processes: (i) densification process of atom cluster leads to the formation of the precursor in amorphous matrix; (ii) the growth of atom cluster leads to the decreasing packing density. The preferential precipitation sequence of metastable phase is bcc, bet, cpc (close-packed crystal, hcp or fee structure). A metastable phase decomposition (Fe,Mo)(23)B-6 (fcc)-Fe2B highly strained bet phase was observed during crystallization of (Fe(0.99)M(0.01))(78)Si9B13 metallic glass, which is related to the occurrence of nanocrystalline.展开更多
B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells....B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells. The effects of Al_2O_3 content on the structures, thermal properties, and sintering behaviors of the B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass were investigated in detail. The Al_2O_3 content largely influenced the structures and thermal properties of the glass. When the Al_2O_3 content 5mol%, the transition temperature of the glass decreased with the Al_2O_3 content, while the crystallization temperature increased with the Al_2O_3 content. However, higher Al_2O_3 content degraded the stability of the glass. The B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with 5 mol% Al_2O_3 content exhibits the optimal sintering densification characteristics and can be used as glass sealants for solid oxide fuel cells.展开更多
Based on the designed As2Se3 and As2S3 chalcogenide glass photonic crystal fiber(PCF) and the scalar nonlinear Schrdinger equation,the effects of pump power and wavelength on modulation instability(MI) gain are co...Based on the designed As2Se3 and As2S3 chalcogenide glass photonic crystal fiber(PCF) and the scalar nonlinear Schrdinger equation,the effects of pump power and wavelength on modulation instability(MI) gain are comprehensively studied in the abnormal dispersion regime of chalcogenide glass PCF.Owing to high Raman effect and high nonlinearity,ultra-broadband MI gain is obtained in chalcogenide glass PCF.By choosing the appropriate pump parameter,the MI gain bandwidth reaches 2738 nm for the As2Se3 glass PCF in the abnormal-dispersion region,while it is 1961 nm for the As2S3 glass PCF.展开更多
The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(...The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(100 ﹣ x)SiO<sub>2</sub> (where x = 23.4, 26.0, 29.1, and 33.5 mol% Li<sub>2</sub>O) has been studied. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which make it possible to provide a maximum dehydration and removal of bubbles from the glass melt. The parameters of nucleation and growth of phase separated in homogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I<sub>st</sub> of lithium disilicate crystals in the 23.4Li<sub>2</sub>O·76.6SiO<sub>2</sub>, 26Li<sub>2</sub>O·74SiO<sub>2</sub> and 29.1Li<sub>2</sub>O·70.9SiO<sub>2</sub> glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I<sub>st</sub> for the glass of the stoichiometric lithium disilicate composition 33.51Li<sub>2</sub>O·66.5SiO<sub>2</sub>. It has been found that the crystal growth rate has a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li<sub>2</sub>O-SiO<sub>2</sub> system is compared with that in the glass of the stoichiometric lithium disilicate composition. The conclusion has been made that the phase separation weakly affects the nucleation parameters of the lithium disilicate and has a strong effect on the crystal growth.展开更多
Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce...Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce:LuAG ceramics exhibit a light yield much lower than the expected theoretical value due to the inevitable presence of LuAl antisite defects at high sintering temperatures.This work demonstrates a low-temperature(1100℃)synthetic strategy for elaborating transparent LuAG–Al_(2)O_(3) nanoceramics through the crystallization of 72 mol%Al_(2)O_(3)–28 mol%Lu_(2)O_(3)(ALu28)bulk glass.The biphasic nanostructure composed of LuAG and Al_(2)O_(3) nanocrystals makes up the whole ceramic materials.Most of Al_(2)O_(3) is distributed among LuAG grains,and the rest is present inside the LuAG grains.Fully dense biphasic LuAG–Al_(2)O_(3) nanoceramics are highly transparent from the visible region to mid-infrared(MIR)region,and particularly the transmittance reaches 82%at 780 nm.Moreover,LuAl antisite defect-related centers are completely undetectable in X-ray excited luminescence(XEL)spectra of Ce:LuAG–Al_(2)O_(3) nanoceramics with 0.3–1.0 at%Ce.The light yield of 0.3 at%Ce:LuAG–Al_(2)O_(3) nanoceramics is estimated to be 20,000 ph/MeV with short 1μs shaping time,which is far superior to that of commercial Bi_(4)Ge_(3)O_(12)(BGO)single crystals.These results show that a low-temperature glass crystallization route provides an alternative approach for eliminating the antisite defects in LuAG-based ceramics,and is promising to produce garnet-based ceramic materials with excellent properties,thereby meeting the demands of advanced scintillation applications.展开更多
The construction of scintillating ceramics is of great technological importance for various fundamental applications, including medical diagnostic, security inspection, resource exploration and particle physics. The c...The construction of scintillating ceramics is of great technological importance for various fundamental applications, including medical diagnostic, security inspection, resource exploration and particle physics. The chief challenge is the facile and scalable synthesis of scintillating ceramics with the desirable combination of pore-free, reliable mechanical properties and excellent scintillating performance. Here we present a pressureless glass crystallization strategy for the construction of scintillating composite with high crystallinity. The fabricated scintillating composites are featured by small optical turbidity, excellent mechanical properties, and efficient scintillating luminescence with the scintillating light yield of 15,000 pH/MeV and about 2.46 times higher than that of the commercial BGO single crystal. Moreover, the scintillating composite derived radiation detector device is successfully elaborated. The practical application for monitoring gamma ray is demonstrated and the precision of the device is less than that of the tolerable deviation of 30%. Our results suggest an innovative approach for expanding the category of scintillating material candidates, pointing to practical application in the field of radiation detection.展开更多
An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photoni...An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photonic crystal fibers pumped with 1.0 μm femtosecond lasers up to chalcogenide step-index and microstructured fibers pumped from optical parametric amplifiers tuned to mid-infrared wavelengths. In particular, silica and silicatebased all-normal dispersion(ANDi) photonic crystal fibers have been demonstrated for pumping with femtosecond lasers operating at 1.56 μm with the recorded spectra covering 0.9–2.3 μm. This matches amplification bands of robust fiber amplifiers and femtosecond lasers. The review therefore focuses specifically on this wavelength range, discussing glass and nonlinear fiber designs, experimental results on supercontinuum generation up to the fundamental limit of oxide glass fiber transmission around 2.8 μm, and various limitations of supercontinuum bandwidth and coherence. Specifically, the role of nonlinear response against the role of dispersion profile shape is analyzed for two different soft glass ANDi fibers pumped at more than 2.0 μm. A spatio-temporal interaction of the fundamental fiber mode with modes propagating in the photonic lattice of the discussed ANDi fibers is shown to have positive effects on the coherence of the supercontinuum at pump pulse durations of 400 fs. Finally, the design and development of graded-index, nanostructured core optical fibers are discussed.In such structures the arbitrary shaping of the core refractive index profile could significantly improve the engineering flexibility of dispersion and effective mode area characteristics, and would be an interesting platform to further study the intermodal interaction mechanisms and their impact on supercontinuum coherence for subpicosecond laser pumped setups.展开更多
The effect of electropulsing treatment(EPT)on the microstructure of a Ti-based bulk metallic glass(BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microst...The effect of electropulsing treatment(EPT)on the microstructure of a Ti-based bulk metallic glass(BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG.When the maximum current density is no more than 2 720A/mm^2,the samples retains amorphous nature,whereas,beyond that,crystalline phases precipitate from the glassy matrix.During EPT,the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720A/mm^2 is higher than the crystallization temperature of the BMG,leading to the crystallization event.展开更多
Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an imp...Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an improved inhomogeneity or to measure the flow of these melts.In the last years also the use of magnetic gradient forces has become an object of research mainly in electrochemistry.On the basis of preliminary investigations the influence of these forces on paramagnetic ions such as Fe;in oxide melts is investigated to examine the potential of magnetic gradient forces as a tool to create defined gradient materials.展开更多
The structural evolution of Cu_(45)Zr_(45)Ag_(10) metallic glass was investigated by in situ transmission electron microscopy heating experiments. The relationship between phase separation and crystallization wa...The structural evolution of Cu_(45)Zr_(45)Ag_(10) metallic glass was investigated by in situ transmission electron microscopy heating experiments. The relationship between phase separation and crystallization was elucidated. Nucleation and growth-controlled nanoscale phase separation at early stage were seen to impede nanocrystallization, while a coarser phase separation via aggregation of Ag-rich nanospheres was found to promote the precipitation of Cu-rich nanocrystals.Coupling of composition and dynamics heterogeneities was supposed to play a key role during phase separation preceding crystallization.展开更多
There are limited studies in the literature about machinability of bulk metallic glass (BMG). As a novel and promising structural material, BMG material machining characteristics need to be verified before its utili...There are limited studies in the literature about machinability of bulk metallic glass (BMG). As a novel and promising structural material, BMG material machining characteristics need to be verified before its utilization. In this paper, the effects of cutting speed, feed rate, depth of cut, abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated. The experimental evaluations were carried out using cubic boron nitride (CBN) and A1203 cup wheel grinding tools. The parameters were evaluated along with the results of cutting force, temperature and surface roughness measurements, X-ray, scanning electron microscope (SEM) and surface roughness analyse. The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased. The effect of feed rate was opposite to the cutting speed effect, and increasing feed rate caused higher grinding forces and substantially lower specific energy. Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks. The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks. The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the rangeof 0.34-0.58 lam. This study also demonstrates that con- ventional A1203 wheel is not suitable for grinding of the BMG in dry conditions.展开更多
Ce doped Lu_(3)Al_(5)O_(12)(Ce:LuAG)transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency,high thermal quenching temperature,and good...Ce doped Lu_(3)Al_(5)O_(12)(Ce:LuAG)transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency,high thermal quenching temperature,and good thermal stability.However,Ce:LuAG ceramics mainly emit green light.The shortage of red light as well as the expensive price of Lu compounds are hindering their application for white lighting.In this work,transparent(Lu,Gd)_(3)Al_(5)O_(12)–Al_(2)O_(3)(LuGAG–Al_(2)O_(3))nanoceramics with different replacing contents of Gd^(3+)(10%–50%)were successfully elaborated via a glass-crystallization method.The obtained ceramics with full nanoscale grains are composed of the main LuGAG crystalline phase and secondary Al_(2)O_(3) phase,exhibiting eminent transparency of 81.0%@780 nm.After doping by Ce^(3+),the Ce:LuGAG–Al_(2)O_(3) nanoceramics show a significant red shift(510 nm→550 nm)and make up for the deficiency of red light component in the emission spectrum.The Ce:LuAG–Al_(2)O_(3) nanoceramics with 20%Gd^(3+)show high internal quantum efficiency(81.5%in internal quantum efficiency(IQE),96.7%of Ce:LuAG–Al_(2)O_(3) nanoceramics)and good thermal stability(only 9%loss in IQE at 150℃).When combined with blue LED chips(10 W),0.3%Ce:LuGAG–Al_(2)O_(3) nanoceramics with 20%Gd^(3+)successfully realize the high-quality warm white LED lighting with a color coordinate of(0.3566,0.435),a color temperature of 4347 K,CRI of 67.7,and a luminous efficiency of 175.8 lm·W^(−1).When the transparent 0.3%Ce:LuGAG–Al_(2)O_(3) nanoceramics are excited by blue laser(5 W·mm^(−2)),the emission peak position redshifts from 517 to 570 nm,the emitted light exhibits a continuous change from green light to yellow light,and then to orange-yellow light,and the maximum luminous efficiency is up to 234.49 lm·W^(−1)(20%Gd^(3+)).Taking into account the high quantum efficiency,good thermal stability,and excellent and adjustable luminous properties,the transparent Ce:LuGAG–Al_(2)O_(3) nanoceramics with different Gd^(3+)substitution contents in this paper are believed to be promising candidates for high-power white LED/LD lighting.展开更多
文摘The silica sand deposit located at km 55 Jalan Pantai Kuala Terengganu-Kuala Besut in the District of Setiu, North Terengganu consists of loose sand of fine to coarse grain size which is developed over the raised beaches of marine origin. The underlying bedrock is believed to be either metasediment of Late Paleozoic age or intrusive granitic rocks. The average content of SiO2 is 99.3% while for the Fe2O3, Al2O3 and TiO2, their average content are 0.1%, 0.3% and 0.2% respectively. The screen analyses show that more than 90 percent of the silica sand is within 150 to 1,180 micron size range. The total area underlain by potential silica sand is about 1.9 million sq. metres with total measured reserve about 2.6 million tonnes. According to Malaysian Standard, MS 701:1981 and British Standard BS 2975:1988, silica sand for making crystal glass should meet the grade B specification in which the purity of silica sand is not less than 99.5% with only a small amount of iron oxide (0.015%), alumina (0.05%), chromium oxide (maximum 2 ppm) and other mineral oxides. In the production of crystal glass, a front loading furnace was used and maximum melting temperature was 1400 ℃. After melting process, physical evaluation on the crystal glass products were performed pertaining to complete accomplishment of melting such as existing of bubbles inside crystal glasses. In order to ensure that crystal glass quality meets the international standard, specification for crystal glass published by British standard BS 3828:1973 was taken as a guideline. Some of the parameters are density, surface hardness and refractive index. In general, silica sand from Gong Belibis, Setiu Terengganu is suitable as a raw material for making crystal glass product.
基金Funded by the National Natural Science Foundation of China(51025416,51202104 and 51362019)the Natural Science Foundation of the Inner Mongolia Autonomous Region(2012MS0807)+1 种基金the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region,the Talent Incubation Funding of School of Materials and Metallurgy(2014CY012)the Talent Incubation Funding of School of Materials and Metallurgy(2014CY012)
文摘Sm2O3 containing zinc-borosilicate glass and glass ceramics were prepared by melt quenching method, and the effect of Sm2O3 and micro-crystallization on the chemical stability of borosilicate glass was explored. DTA analysis showed that the endothermic peak and exothermic peak of basic glass changed from 635 ℃ and 834 ℃ to 630 ℃ and 828 ℃ respectively as a result of the doping of Sm2O3. XRD analysis showed the promoting effect of Sm2O3 on crystallization ability of this glass. The cumulative mass loss of base glass, Sm2O3 containing glass, glass ceramic and Sm2O3 containing glass ceramic was 0.289, 0.253, 0.329, 0.269 mg/mm2 respectively after 26 days corrosion in alkali solution, and 1.293, 1.290, 0.999, 1.040 mg/mm2 respectively in acidic erosion medium. Micro-crystallization decreased and improved the alkali and acid resistance of borosilicate glass respectively, the addition of Sm2O3 increased the alkali resistance of base glass and glass ceramics, and the slight effect of Sm2O3 on the acid resistance of borosilicate glass was also observed.
基金Supported by the Youth Foundation of Beijing Graduate School of Wuhan University of Technology(No.97-QW)
文摘BaO is the most common consideration in the preparation of newcrystal glass for getting rid of lead content in the glass andceramic wares to protect hu- man health and environment. But forkeeping the glass products' properties to meet the requirements ofthe tradi- tional crystal glass, B_2O_3, Al_2O_3, TiO_2, SrO and ZnOetc (at a special ratio) had been researched with BaO to con- stitutea mixture to replace the lead content in the glass compositions.
文摘The effect of Cr2O3 on the nucleation and crystallization of Na2O-CaO-Al2O3-SiO2-F- glass has been investigated by means of ESR(Electron Spin Resonance), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Specrometer) and so on. Computer pattern recognition is applied to optimize the heat-treatment schedules. The experimental results show that the base glass containing more than 1 .5 % (mass fraction) Cr2O3 can be nucleated internally and converted to spheroidal crystal glass materials. The spheroidal crystal consisted of fibrous wollastonite crystals radiating from a center. The residual glass phase filled in the interstices between the fibers and between the spherulites. During heat treatment process, the valence states ofchromium changed from Cr6- to Cr3-, and the Cr-spinel solidsolution [CaCr2O4] precipitated followed this valence change. At the primary stage of crystallization, the Cr-spinel could act as a nucleating center on which the principal or}stalline phase β-CaSiO3 grew epitaxially.
文摘In this paper the experimental results associated until the phase separation and nucleation and crystallization of chalcogenidc glasses are described. Experi-ments demonstrate that the phas separation may be affected by small amount of additives. It has been found that some chalcogenide glasses could be converted into glass-ceramics without phase separation. The different mechanisms of nucleated crystallization of chalcogenide glasses are discussed and propossed.
文摘A micromechanism in an atomic level of crystallization of transition metal-metalloid TM(80)M(20) metallic glass is thermodynamically proposed by taking Bernal polyhedra as the starting structure of metallic glass. It is composed of two competitively processes: (i) densification process of atom cluster leads to the formation of the precursor in amorphous matrix; (ii) the growth of atom cluster leads to the decreasing packing density. The preferential precipitation sequence of metastable phase is bcc, bet, cpc (close-packed crystal, hcp or fee structure). A metastable phase decomposition (Fe,Mo)(23)B-6 (fcc)-Fe2B highly strained bet phase was observed during crystallization of (Fe(0.99)M(0.01))(78)Si9B13 metallic glass, which is related to the occurrence of nanocrystalline.
基金Funded by the Jiangxi Provincial Department of Education(KJLD13008)the National Natural Science Foundation of China(number 51362020)the Research Fund for the Doctoral Program of Higher Education(20123601110006)
文摘B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells. The effects of Al_2O_3 content on the structures, thermal properties, and sintering behaviors of the B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass were investigated in detail. The Al_2O_3 content largely influenced the structures and thermal properties of the glass. When the Al_2O_3 content 5mol%, the transition temperature of the glass decreased with the Al_2O_3 content, while the crystallization temperature increased with the Al_2O_3 content. However, higher Al_2O_3 content degraded the stability of the glass. The B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with 5 mol% Al_2O_3 content exhibits the optimal sintering densification characteristics and can be used as glass sealants for solid oxide fuel cells.
基金Project supported by the National Natural Science Fundation of China(Grant No.11404286)the Natural Science Fundation of Zhejiang Province,China(Grant No.LY15F050010)the Scientific Research Foundation of Zhejiang University of Technology,China(Grant No.1401109012408)
文摘Based on the designed As2Se3 and As2S3 chalcogenide glass photonic crystal fiber(PCF) and the scalar nonlinear Schrdinger equation,the effects of pump power and wavelength on modulation instability(MI) gain are comprehensively studied in the abnormal dispersion regime of chalcogenide glass PCF.Owing to high Raman effect and high nonlinearity,ultra-broadband MI gain is obtained in chalcogenide glass PCF.By choosing the appropriate pump parameter,the MI gain bandwidth reaches 2738 nm for the As2Se3 glass PCF in the abnormal-dispersion region,while it is 1961 nm for the As2S3 glass PCF.
文摘The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(100 ﹣ x)SiO<sub>2</sub> (where x = 23.4, 26.0, 29.1, and 33.5 mol% Li<sub>2</sub>O) has been studied. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which make it possible to provide a maximum dehydration and removal of bubbles from the glass melt. The parameters of nucleation and growth of phase separated in homogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I<sub>st</sub> of lithium disilicate crystals in the 23.4Li<sub>2</sub>O·76.6SiO<sub>2</sub>, 26Li<sub>2</sub>O·74SiO<sub>2</sub> and 29.1Li<sub>2</sub>O·70.9SiO<sub>2</sub> glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I<sub>st</sub> for the glass of the stoichiometric lithium disilicate composition 33.51Li<sub>2</sub>O·66.5SiO<sub>2</sub>. It has been found that the crystal growth rate has a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li<sub>2</sub>O-SiO<sub>2</sub> system is compared with that in the glass of the stoichiometric lithium disilicate composition. The conclusion has been made that the phase separation weakly affects the nucleation parameters of the lithium disilicate and has a strong effect on the crystal growth.
基金supported by the National Natural Science Foundation of China (No.51972304)Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park (No.Z221100006722022)+1 种基金the Project of Scientific Experiment on Chinese Manned Space Station,Chinese Academy of Sciences President’s International Fellowship Initiative for 2021 (No.2021VEA0012)the Fundamental Research Funds for the Central Universities.
文摘Transparent Ce:lutetium aluminum garnet(Ce:Lu_(3)A_(l5)O_(12),Ce:LuAG)ceramics have been regarded as potential scintillator materials due to their relatively high density and atomic number(Zeff).However,the current Ce:LuAG ceramics exhibit a light yield much lower than the expected theoretical value due to the inevitable presence of LuAl antisite defects at high sintering temperatures.This work demonstrates a low-temperature(1100℃)synthetic strategy for elaborating transparent LuAG–Al_(2)O_(3) nanoceramics through the crystallization of 72 mol%Al_(2)O_(3)–28 mol%Lu_(2)O_(3)(ALu28)bulk glass.The biphasic nanostructure composed of LuAG and Al_(2)O_(3) nanocrystals makes up the whole ceramic materials.Most of Al_(2)O_(3) is distributed among LuAG grains,and the rest is present inside the LuAG grains.Fully dense biphasic LuAG–Al_(2)O_(3) nanoceramics are highly transparent from the visible region to mid-infrared(MIR)region,and particularly the transmittance reaches 82%at 780 nm.Moreover,LuAl antisite defect-related centers are completely undetectable in X-ray excited luminescence(XEL)spectra of Ce:LuAG–Al_(2)O_(3) nanoceramics with 0.3–1.0 at%Ce.The light yield of 0.3 at%Ce:LuAG–Al_(2)O_(3) nanoceramics is estimated to be 20,000 ph/MeV with short 1μs shaping time,which is far superior to that of commercial Bi_(4)Ge_(3)O_(12)(BGO)single crystals.These results show that a low-temperature glass crystallization route provides an alternative approach for eliminating the antisite defects in LuAG-based ceramics,and is promising to produce garnet-based ceramic materials with excellent properties,thereby meeting the demands of advanced scintillation applications.
基金financially supported by the National Science Fund for Distinguished Young Scholars(No.62125502)the National Natural Science Foundation of China(No.51972113)+4 种基金the Key Program of Guangzhou Scientific Research Special Project(No.201904020013)the Key R&D Program of Guangzhou(No.202007020003)the Science and Technology Project of Guangdong Province(No.2021A0505030004)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01×137)the Fundamental Research Funds for the Central University。
文摘The construction of scintillating ceramics is of great technological importance for various fundamental applications, including medical diagnostic, security inspection, resource exploration and particle physics. The chief challenge is the facile and scalable synthesis of scintillating ceramics with the desirable combination of pore-free, reliable mechanical properties and excellent scintillating performance. Here we present a pressureless glass crystallization strategy for the construction of scintillating composite with high crystallinity. The fabricated scintillating composites are featured by small optical turbidity, excellent mechanical properties, and efficient scintillating luminescence with the scintillating light yield of 15,000 pH/MeV and about 2.46 times higher than that of the commercial BGO single crystal. Moreover, the scintillating composite derived radiation detector device is successfully elaborated. The practical application for monitoring gamma ray is demonstrated and the precision of the device is less than that of the tolerable deviation of 30%. Our results suggest an innovative approach for expanding the category of scintillating material candidates, pointing to practical application in the field of radiation detection.
基金Funding.Fundacja na rzecz Nauki Polskiej(FNP)(First TEAM/2016-1/1)
文摘An overview of the progress on pulse-preserving, coherent, nonlinear fiber-based supercontinuum generation is presented. The context encompasses various wavelength ranges and pump sources, starting with silica photonic crystal fibers pumped with 1.0 μm femtosecond lasers up to chalcogenide step-index and microstructured fibers pumped from optical parametric amplifiers tuned to mid-infrared wavelengths. In particular, silica and silicatebased all-normal dispersion(ANDi) photonic crystal fibers have been demonstrated for pumping with femtosecond lasers operating at 1.56 μm with the recorded spectra covering 0.9–2.3 μm. This matches amplification bands of robust fiber amplifiers and femtosecond lasers. The review therefore focuses specifically on this wavelength range, discussing glass and nonlinear fiber designs, experimental results on supercontinuum generation up to the fundamental limit of oxide glass fiber transmission around 2.8 μm, and various limitations of supercontinuum bandwidth and coherence. Specifically, the role of nonlinear response against the role of dispersion profile shape is analyzed for two different soft glass ANDi fibers pumped at more than 2.0 μm. A spatio-temporal interaction of the fundamental fiber mode with modes propagating in the photonic lattice of the discussed ANDi fibers is shown to have positive effects on the coherence of the supercontinuum at pump pulse durations of 400 fs. Finally, the design and development of graded-index, nanostructured core optical fibers are discussed.In such structures the arbitrary shaping of the core refractive index profile could significantly improve the engineering flexibility of dispersion and effective mode area characteristics, and would be an interesting platform to further study the intermodal interaction mechanisms and their impact on supercontinuum coherence for subpicosecond laser pumped setups.
基金Item Sponsored by National Natural Science Foundation of China(51371065)Postdoctoral Science-Research Developmental Foundation of Heilongjiang Province of China(LBH-Q12073)
文摘The effect of electropulsing treatment(EPT)on the microstructure of a Ti-based bulk metallic glass(BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG.When the maximum current density is no more than 2 720A/mm^2,the samples retains amorphous nature,whereas,beyond that,crystalline phases precipitate from the glassy matrix.During EPT,the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720A/mm^2 is higher than the crystallization temperature of the BMG,leading to the crystallization event.
基金Item Sponsored by Deutsche Forschungsgemeinschaft(HA 2338/4-1)
文摘Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an improved inhomogeneity or to measure the flow of these melts.In the last years also the use of magnetic gradient forces has become an object of research mainly in electrochemistry.On the basis of preliminary investigations the influence of these forces on paramagnetic ions such as Fe;in oxide melts is investigated to examine the potential of magnetic gradient forces as a tool to create defined gradient materials.
基金supported by the National Natural Science Foundation of China (Grant No. 51101004)the financial support of China Scholarship Council. Z.Q. Liu is gratefulsupport by the IMR SYNL-T.S. Kê Research Fellowship
文摘The structural evolution of Cu_(45)Zr_(45)Ag_(10) metallic glass was investigated by in situ transmission electron microscopy heating experiments. The relationship between phase separation and crystallization was elucidated. Nucleation and growth-controlled nanoscale phase separation at early stage were seen to impede nanocrystallization, while a coarser phase separation via aggregation of Ag-rich nanospheres was found to promote the precipitation of Cu-rich nanocrystals.Coupling of composition and dynamics heterogeneities was supposed to play a key role during phase separation preceding crystallization.
文摘There are limited studies in the literature about machinability of bulk metallic glass (BMG). As a novel and promising structural material, BMG material machining characteristics need to be verified before its utilization. In this paper, the effects of cutting speed, feed rate, depth of cut, abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated. The experimental evaluations were carried out using cubic boron nitride (CBN) and A1203 cup wheel grinding tools. The parameters were evaluated along with the results of cutting force, temperature and surface roughness measurements, X-ray, scanning electron microscope (SEM) and surface roughness analyse. The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased. The effect of feed rate was opposite to the cutting speed effect, and increasing feed rate caused higher grinding forces and substantially lower specific energy. Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks. The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks. The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the rangeof 0.34-0.58 lam. This study also demonstrates that con- ventional A1203 wheel is not suitable for grinding of the BMG in dry conditions.
基金This work is financially supported by the National Natural Science Foundation of China(No.51972304)Beijing Municipal Science&Technology Commission,Administrative Commission of Zhongguancun Science Park(No.Z221100006722022)+1 种基金the Project of Scientific Experiment on Chinese Manned Space Station,Chinese Academy of Sciences President’s International Fellowship Initiative for 2021(No.2021VEA0012)the Fundamental Research Funds for the Central Universities.The project benefitted from the microscopy facilities of the Platform MACLE-CVL which was co-funded by the European Union and Centre-Val de Loire Region(FEDER).Declaration of competing interest。
文摘Ce doped Lu_(3)Al_(5)O_(12)(Ce:LuAG)transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency,high thermal quenching temperature,and good thermal stability.However,Ce:LuAG ceramics mainly emit green light.The shortage of red light as well as the expensive price of Lu compounds are hindering their application for white lighting.In this work,transparent(Lu,Gd)_(3)Al_(5)O_(12)–Al_(2)O_(3)(LuGAG–Al_(2)O_(3))nanoceramics with different replacing contents of Gd^(3+)(10%–50%)were successfully elaborated via a glass-crystallization method.The obtained ceramics with full nanoscale grains are composed of the main LuGAG crystalline phase and secondary Al_(2)O_(3) phase,exhibiting eminent transparency of 81.0%@780 nm.After doping by Ce^(3+),the Ce:LuGAG–Al_(2)O_(3) nanoceramics show a significant red shift(510 nm→550 nm)and make up for the deficiency of red light component in the emission spectrum.The Ce:LuAG–Al_(2)O_(3) nanoceramics with 20%Gd^(3+)show high internal quantum efficiency(81.5%in internal quantum efficiency(IQE),96.7%of Ce:LuAG–Al_(2)O_(3) nanoceramics)and good thermal stability(only 9%loss in IQE at 150℃).When combined with blue LED chips(10 W),0.3%Ce:LuGAG–Al_(2)O_(3) nanoceramics with 20%Gd^(3+)successfully realize the high-quality warm white LED lighting with a color coordinate of(0.3566,0.435),a color temperature of 4347 K,CRI of 67.7,and a luminous efficiency of 175.8 lm·W^(−1).When the transparent 0.3%Ce:LuGAG–Al_(2)O_(3) nanoceramics are excited by blue laser(5 W·mm^(−2)),the emission peak position redshifts from 517 to 570 nm,the emitted light exhibits a continuous change from green light to yellow light,and then to orange-yellow light,and the maximum luminous efficiency is up to 234.49 lm·W^(−1)(20%Gd^(3+)).Taking into account the high quantum efficiency,good thermal stability,and excellent and adjustable luminous properties,the transparent Ce:LuGAG–Al_(2)O_(3) nanoceramics with different Gd^(3+)substitution contents in this paper are believed to be promising candidates for high-power white LED/LD lighting.