In order to efficiently explore and use woody biomass,six lignin fractions were isolated from dewaxed Caragana sinica via successive extraction with organic solvents and alkaline solutions.The lignin structures were c...In order to efficiently explore and use woody biomass,six lignin fractions were isolated from dewaxed Caragana sinica via successive extraction with organic solvents and alkaline solutions.The lignin structures were characterized by Fourier transform infrared spectroscopy(FT-IR) and 1D and 2D Nuclear Magnetic Resonance(NMR).FT-IR spectra revealed that the "core" of the lignin structure did not significantly change during the treatment under the conditions given.The results of 1H and 13C NMR demonstrated that the lignin fraction L2,isolated with 70% ethanol containing 1% NaOH,was mainly composed of β-O-4 ether bonds together with G and S units and trace p-hydroxyphenyl unit.Based on the 2D HSQC NMR spectrum,the ethanol organosolv lignin fraction L1,extracted with 70% ethanol,presents a predominance of β-O-4′ aryl ether linkages(61% of total side chains),and a low abundance of condensed carbon-carbon linked structures(such as ββ′,β-1′,and β-5′) and a lower S/G ratio.Furthermore,a small percentage(ca.9%) of the linkage side chain was found to be acylated at the γ-carbon.展开更多
The catalytic pyrolysis of lignites is a technical process whose development is complex and time-consuming with the goal to maximize the yield of the desired low-volatile hydrocarbons of choice and to minimize the yie...The catalytic pyrolysis of lignites is a technical process whose development is complex and time-consuming with the goal to maximize the yield of the desired low-volatile hydrocarbons of choice and to minimize the yield of solid residual products. Not every type of lignite is suitable for this process due to its particular chemical composition. In order to be able to predict which lignite specimen will be an especially promising raw material for the pyrolytic liberation of target products, the chemical classification by IR spectroscopic methods was investigated. MIR spectroscopy has been demonstrated to be a valuable tool to characterize the the molecular composition of lignites and to determine the concentrations of aliphatic and aromatic functional groups in lignite as well as alcoholic OH and other forms of bound oxygen. These data provide a comprehensive chemical characterization of the material and help to predict the composition of the chemical components liberated by catalytic decomposition. With a complementary NIR spectroscopic approach, a chemometric method has been developed with which the elemental com-position of the lignites can be determined in a fast and pragmatic way leading to a prediction of the product range of a theoretical pyrolytic product range. Thus, this spectroscopic investigation is a toolbox that can answer the question if the commercial exploitation of catalytic pyrolysis of a lignite sample in question will make sense without preliminary conduction of long and time-consuming testing.展开更多
The products of refractory materials are used for lining furnace, incinerators and kilns among other uses and they have the potential of withstanding high temperature without deformation. The objective of the research...The products of refractory materials are used for lining furnace, incinerators and kilns among other uses and they have the potential of withstanding high temperature without deformation. The objective of the research was to charac-terize the clay soil sample collected from Tshwane University of Technology in Pretoria. The sample, collected from a location Latitude 25.0969°S and Longi-tude 28.1624°E, was oven-dried, pulverized and sieved in the laboratory. Min-eralogical and elemental compositions of the sample were determined by using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) analytical methods. The XRF analysis revealed Fe2O3, Al2O3 and SiO2 as the major constituents, while the other elements occur in minor quantities. Mineralogically, the three samples contain Montmorillonite, Kaolinite and Bentonite, while Samples A contained Quartz in addition to ear-lier mentioned minerals, samples B and C contained Albite.展开更多
Kaolin is one of the most important industrial minerals whose application is dependent on its structure and chemical composition. This study makes an attempt to explore and determine the origin of kaolin deposits with...Kaolin is one of the most important industrial minerals whose application is dependent on its structure and chemical composition. This study makes an attempt to explore and determine the origin of kaolin deposits within and around Okpella, as well as to investigate the mineralogical and chemical compositions using the X-ray diffraction (XRD) and X-ray fluorescence (XRF) method. These were carried out with the intention of determining the most suitable applications for the clay mineral. It was observed that major phases in the clay samples from the three different deposits are kaolinite, microcline, illite/mica, plagioclase/albite and quartz. These phases were observed in varied percentages. Samples from Ajego 2 show a marked absence of kaolinite but contain high concentration of plagioclase feldspar and quartz which permit its usage in the production of glass and iron industries. Further, the samples from Ajego 1 contain by far the highest concentration of kaolinite, while the samples from Anegha consist of kaolinite, a mixed layer of illite/mica, plagioclase, alkali feldspars, and albite which is necessary for producing mullite fibers in ceramic matrix at a temperature of around 1400°C and it is suitable in pigment production. The XRF result for Ajego2 and Anegha samples has Silica composition of 51.847 wt%, 32.540 wt% and 37.295 wt% respectively and an alumina content of 14.962 wt%, 29.834 wt% and 20.227 wt% respectively. The trace amount of some of the oxides such as K2O, TiO2, Fe2O3 and SnO2 can help in the beneficiation process.展开更多
Studies on ultrafine particle catalyst have attracted many researchers' attention by its large surface area,higher activity and selectivity.Based on the mechanism of α-Fe and Fe_xC_y as the catalytical active spe...Studies on ultrafine particle catalyst have attracted many researchers' attention by its large surface area,higher activity and selectivity.Based on the mechanism of α-Fe and Fe_xC_y as the catalytical active species this paper reports for the first time the preparation method of Fe_3C ultrafine parti- cle catalyst,from highly dispersed amorphous Fe powder and free carbon.The Fe powder and free car- bon,prepared by laser pyrolysis technique,was then treated by washing and heating at high tempera- ture protected with N_2.The catalyst prepared under different experimental conditions was characterazed by means of XRD,electronic diffraction and TEM.It shows that the crystlline grain size is in a range of 1-4nm and composed of Fe_3C and α-Fe.It has been found that the ultrafine particle iron-carbonide catalyst exhibited much higher activity and selectivity to light olefins.At the standard atmosphere and 380℃ reaction temperature,the conversion of CO reached a maximum of 80%.展开更多
Six coordination compounds of Pt(Ⅱ)L_2 and Ir(Ⅲ)L_3 type(where L is PT^-, 3Me-PT^-or 4Me-PT^-)are reported here.Four coordination compounds of the latter two ligands have never been reported before,while PT^-'s ...Six coordination compounds of Pt(Ⅱ)L_2 and Ir(Ⅲ)L_3 type(where L is PT^-, 3Me-PT^-or 4Me-PT^-)are reported here.Four coordination compounds of the latter two ligands have never been reported before,while PT^-'s were synthesized with H_2PtCl_6 and(NH_4)_3IrCl_6 respectively,which were different from the methods of Davidson et al.~1 and Sterinbrech^2.They were characterized by elemental analysis, UV,IR,~1HNMR and molar conductance.Their structural formulas have been determined,and the mechanism of synthetic reaction has been discussed.展开更多
Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other ...Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.展开更多
It has been made certain that thio-and oxy-diacetic acid hydrazides are potential anticancer compounds.However,their ability to form complexes with transition metals and the properties of the complexes thus formed hav...It has been made certain that thio-and oxy-diacetic acid hydrazides are potential anticancer compounds.However,their ability to form complexes with transition metals and the properties of the complexes thus formed have not been studied.Employing a new potential anticancer ligand 1,2-bis(thioacetic acid hydrazide)ethane prepared in our lab,along with ligands oxydiacetic hydrazide and 1,2-bis(oxyacetic acid hydrazide) ethane,a series of 11 new first-row transition metal(M=Zn^(2+),Cu^(2+),Co^(2+), Ni^(2+))complexes with each of the above three ligands have been synthesized and characterized by means of elemental analyses,IR,TG and X-ray powder diffraction.展开更多
A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% ...A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% samples′ crystallinity almost linearly decreases with increasing the amount of MoO\-3 loaded. The IR spectra and XRD patterns suggest that the progressive destabilization of the H\%β\% zeolite structure is caused by increasing Mo loading in (MoO\-3+H\%β\% zeolite). During the calcination, Al\-2(MoO\-4)\-3 formed from the dealumination of H\%β\% zeolite, causes the substantially partial breakdown of the zeolite framework when the Mo loading in MoO\-3+H\%β\% is relatively high.展开更多
This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphol...This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.展开更多
Chromium iron phosphate glass was investigated for use as waste form because of its improved chemical durability. The introduction of chromium in sodium-iron-phosphate glass is used to compare its effect with iron in ...Chromium iron phosphate glass was investigated for use as waste form because of its improved chemical durability. The introduction of chromium in sodium-iron-phosphate glass is used to compare its effect with iron in inhibition of corrosion. The sodium-chromium-iron phosphate glass of composition 10Na2O-30Fe2O3-5Cr2O3-55P2O5 (mol%) was produced by melting batches of (99, 98% pure) Cr2O3, Fe2O3, Na2CO3, and (NH4)2HPO4 at 1080°C for one hour and pouring the liquid into steel mold. The sample was annealed at 680°C for 48 h. We have performed the measurement of X-Ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), Infra-Red spectroscopy (IR), and the chemical durability. The IR of the glass studied, contains two dominant bands, which were characteristic of pyrophosphate groups, (P-O) stretching mode of P-O non bridging oxygen at 1055 cm-1 and sym stretching mode of bridging oxygen at444 cm-1 respectively. There is also a band at603 cm-1 attributed to isolated tetrahedral units (PO4)3-. The chemical durability of the glass was investigated by measuring the weight loss in distilled water at 90°C for 22 days.展开更多
Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtaine...Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtained samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. The result of the magnetization of the obtained VN product as a function of temperature indicates that the onset superconducting transition temperature is about 8.4K. Furthermore, the possible reaction mechanism is also discussed.展开更多
Glasses in the ternary system Cr2O3-PbO-P2O5 were prepared by direct melting of the mixture with stoichiometric proportions of the reagents Cr2O3, PbO and (NH4)2HPO4 at 1080℃. The glasses obtained are transparent in ...Glasses in the ternary system Cr2O3-PbO-P2O5 were prepared by direct melting of the mixture with stoichiometric proportions of the reagents Cr2O3, PbO and (NH4)2HPO4 at 1080℃. The glasses obtained are transparent in colour and have a non-hygroscopic appearance. The study of the dissolution rate was carried out on ternary glasses xCr2O3-(45-x)PbO-55P2O5 with (1 ≤ x ≤ 4;mol%), immersed in distilled water at 90℃ for 24 days, indicating a maximum of chemical durability when the level of chromium oxide passed through 2 mol%. Both, IR spectra and X-ray diffraction have indicated the predominance of metaphosphate or cyclic metaphosphate groups with some traces of isolated orthophosphate groups when the Cr2O3 content is equal to x = 2. Analysis of the density values also, has showed a maximum density for x = 2 mol%. The covalent radius values of oxygen have indicated that the minimum value rcal (O2–) is observed for x = 2 mol% and therefore a relatively high reinforcement of the metal-oxygen-phosphorus (Cr-O-P) bonds. SEM Micrographs have exhibited two phases, a vitreous phase and a crystalline phase. The radical change in the structure from ultraphosphate Q3 groups to ring metaphosphate Q2 and orthophosphate groups Q0 seems to be the cause of the formation of crystallites. Beyond 2 mol% of Cr2O3, the structure of the glass changed relatively and the orthophosphate phases increased to the detriment of the metaphosphate phases. We observed a decrease in chemical durability. However, it was confirmed that the dissolution rate (DR) of the S2 analysed compound is comparable to the values of borosilicate glasses which are used as alternative materials for the immobilisation of nuclear waste substances.展开更多
Use of the regular melting-quench method allowed the isolation of a small glass domain within the ternary system Li2O-P2O5-Cr2O3 at 1000°C. Electrical conductivity and dielectric permittivity measures on sample g...Use of the regular melting-quench method allowed the isolation of a small glass domain within the ternary system Li2O-P2O5-Cr2O3 at 1000°C. Electrical conductivity and dielectric permittivity measures on sample glasses and ceramic glasses of this domain were performed at a frequency of 10 kHz and at temperatures between 25°C and 300°C. The values of dielectric permittivity and electrical conductivity increase with increasing Li2O content. However, increases of Cr2O3 content, even at low concentrations, induce a change in electrical conductivity behaviour from that of a glass to that of a ceramic glass. The introduction of an increasing amount of Li2O content in vitreous phosphorus pentoxide changes its three-dimensional network;rupture of the P-O-P bond then occurs and there is formation of easily polarisable entities with quite high values of . The vibrational spectroscopy technique I.R has allowed an efficient investigation of the structural change versus composition within the above indicated ternary diagram. The maximal dielectric permittivity obtained at 300°C, both for the glasses and for the ceramic glasses varied in the order 104 to 3 × 105, while the maximum electrical conductivity obtained at 300°C for the ceramic glasses was in the order of 10-3 Ωcm-1.展开更多
基金Major State Basic Research Projects of China(973-2010CB732204)Specific Programs in Graduate Science and Technology Innovation of Beijing Forestry University(BLYJ201110)
文摘In order to efficiently explore and use woody biomass,six lignin fractions were isolated from dewaxed Caragana sinica via successive extraction with organic solvents and alkaline solutions.The lignin structures were characterized by Fourier transform infrared spectroscopy(FT-IR) and 1D and 2D Nuclear Magnetic Resonance(NMR).FT-IR spectra revealed that the "core" of the lignin structure did not significantly change during the treatment under the conditions given.The results of 1H and 13C NMR demonstrated that the lignin fraction L2,isolated with 70% ethanol containing 1% NaOH,was mainly composed of β-O-4 ether bonds together with G and S units and trace p-hydroxyphenyl unit.Based on the 2D HSQC NMR spectrum,the ethanol organosolv lignin fraction L1,extracted with 70% ethanol,presents a predominance of β-O-4′ aryl ether linkages(61% of total side chains),and a low abundance of condensed carbon-carbon linked structures(such as ββ′,β-1′,and β-5′) and a lower S/G ratio.Furthermore,a small percentage(ca.9%) of the linkage side chain was found to be acylated at the γ-carbon.
文摘The catalytic pyrolysis of lignites is a technical process whose development is complex and time-consuming with the goal to maximize the yield of the desired low-volatile hydrocarbons of choice and to minimize the yield of solid residual products. Not every type of lignite is suitable for this process due to its particular chemical composition. In order to be able to predict which lignite specimen will be an especially promising raw material for the pyrolytic liberation of target products, the chemical classification by IR spectroscopic methods was investigated. MIR spectroscopy has been demonstrated to be a valuable tool to characterize the the molecular composition of lignites and to determine the concentrations of aliphatic and aromatic functional groups in lignite as well as alcoholic OH and other forms of bound oxygen. These data provide a comprehensive chemical characterization of the material and help to predict the composition of the chemical components liberated by catalytic decomposition. With a complementary NIR spectroscopic approach, a chemometric method has been developed with which the elemental com-position of the lignites can be determined in a fast and pragmatic way leading to a prediction of the product range of a theoretical pyrolytic product range. Thus, this spectroscopic investigation is a toolbox that can answer the question if the commercial exploitation of catalytic pyrolysis of a lignite sample in question will make sense without preliminary conduction of long and time-consuming testing.
文摘The products of refractory materials are used for lining furnace, incinerators and kilns among other uses and they have the potential of withstanding high temperature without deformation. The objective of the research was to charac-terize the clay soil sample collected from Tshwane University of Technology in Pretoria. The sample, collected from a location Latitude 25.0969°S and Longi-tude 28.1624°E, was oven-dried, pulverized and sieved in the laboratory. Min-eralogical and elemental compositions of the sample were determined by using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) analytical methods. The XRF analysis revealed Fe2O3, Al2O3 and SiO2 as the major constituents, while the other elements occur in minor quantities. Mineralogically, the three samples contain Montmorillonite, Kaolinite and Bentonite, while Samples A contained Quartz in addition to ear-lier mentioned minerals, samples B and C contained Albite.
文摘Kaolin is one of the most important industrial minerals whose application is dependent on its structure and chemical composition. This study makes an attempt to explore and determine the origin of kaolin deposits within and around Okpella, as well as to investigate the mineralogical and chemical compositions using the X-ray diffraction (XRD) and X-ray fluorescence (XRF) method. These were carried out with the intention of determining the most suitable applications for the clay mineral. It was observed that major phases in the clay samples from the three different deposits are kaolinite, microcline, illite/mica, plagioclase/albite and quartz. These phases were observed in varied percentages. Samples from Ajego 2 show a marked absence of kaolinite but contain high concentration of plagioclase feldspar and quartz which permit its usage in the production of glass and iron industries. Further, the samples from Ajego 1 contain by far the highest concentration of kaolinite, while the samples from Anegha consist of kaolinite, a mixed layer of illite/mica, plagioclase, alkali feldspars, and albite which is necessary for producing mullite fibers in ceramic matrix at a temperature of around 1400°C and it is suitable in pigment production. The XRF result for Ajego2 and Anegha samples has Silica composition of 51.847 wt%, 32.540 wt% and 37.295 wt% respectively and an alumina content of 14.962 wt%, 29.834 wt% and 20.227 wt% respectively. The trace amount of some of the oxides such as K2O, TiO2, Fe2O3 and SnO2 can help in the beneficiation process.
基金The project was supported by the National Natural Science Foundation of China.
文摘Studies on ultrafine particle catalyst have attracted many researchers' attention by its large surface area,higher activity and selectivity.Based on the mechanism of α-Fe and Fe_xC_y as the catalytical active species this paper reports for the first time the preparation method of Fe_3C ultrafine parti- cle catalyst,from highly dispersed amorphous Fe powder and free carbon.The Fe powder and free car- bon,prepared by laser pyrolysis technique,was then treated by washing and heating at high tempera- ture protected with N_2.The catalyst prepared under different experimental conditions was characterazed by means of XRD,electronic diffraction and TEM.It shows that the crystlline grain size is in a range of 1-4nm and composed of Fe_3C and α-Fe.It has been found that the ultrafine particle iron-carbonide catalyst exhibited much higher activity and selectivity to light olefins.At the standard atmosphere and 380℃ reaction temperature,the conversion of CO reached a maximum of 80%.
文摘Six coordination compounds of Pt(Ⅱ)L_2 and Ir(Ⅲ)L_3 type(where L is PT^-, 3Me-PT^-or 4Me-PT^-)are reported here.Four coordination compounds of the latter two ligands have never been reported before,while PT^-'s were synthesized with H_2PtCl_6 and(NH_4)_3IrCl_6 respectively,which were different from the methods of Davidson et al.~1 and Sterinbrech^2.They were characterized by elemental analysis, UV,IR,~1HNMR and molar conductance.Their structural formulas have been determined,and the mechanism of synthetic reaction has been discussed.
文摘Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.
文摘It has been made certain that thio-and oxy-diacetic acid hydrazides are potential anticancer compounds.However,their ability to form complexes with transition metals and the properties of the complexes thus formed have not been studied.Employing a new potential anticancer ligand 1,2-bis(thioacetic acid hydrazide)ethane prepared in our lab,along with ligands oxydiacetic hydrazide and 1,2-bis(oxyacetic acid hydrazide) ethane,a series of 11 new first-row transition metal(M=Zn^(2+),Cu^(2+),Co^(2+), Ni^(2+))complexes with each of the above three ligands have been synthesized and characterized by means of elemental analyses,IR,TG and X-ray powder diffraction.
基金Supported by the National Natural Science Foundation of China(No.2 0 30 30 19) and the National"973"Project of China(No.2 0 0 3CB6 15 80 2 )
文摘A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% samples′ crystallinity almost linearly decreases with increasing the amount of MoO\-3 loaded. The IR spectra and XRD patterns suggest that the progressive destabilization of the H\%β\% zeolite structure is caused by increasing Mo loading in (MoO\-3+H\%β\% zeolite). During the calcination, Al\-2(MoO\-4)\-3 formed from the dealumination of H\%β\% zeolite, causes the substantially partial breakdown of the zeolite framework when the Mo loading in MoO\-3+H\%β\% is relatively high.
基金This work was financially supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193,KGFZD-135-19-02)the National Natural Science Foundation of China(No.51801219).Special appreciation to the CAS-TWAS Presidential Fellowship for sponsorship.
文摘This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.
文摘Chromium iron phosphate glass was investigated for use as waste form because of its improved chemical durability. The introduction of chromium in sodium-iron-phosphate glass is used to compare its effect with iron in inhibition of corrosion. The sodium-chromium-iron phosphate glass of composition 10Na2O-30Fe2O3-5Cr2O3-55P2O5 (mol%) was produced by melting batches of (99, 98% pure) Cr2O3, Fe2O3, Na2CO3, and (NH4)2HPO4 at 1080°C for one hour and pouring the liquid into steel mold. The sample was annealed at 680°C for 48 h. We have performed the measurement of X-Ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), Infra-Red spectroscopy (IR), and the chemical durability. The IR of the glass studied, contains two dominant bands, which were characteristic of pyrophosphate groups, (P-O) stretching mode of P-O non bridging oxygen at 1055 cm-1 and sym stretching mode of bridging oxygen at444 cm-1 respectively. There is also a band at603 cm-1 attributed to isolated tetrahedral units (PO4)3-. The chemical durability of the glass was investigated by measuring the weight loss in distilled water at 90°C for 22 days.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK20160292the Natural Science Foundation of the Higher Educations Institutions of Jiangsu Province under Grant No 16KJB150013+1 种基金the National Natural Science Foundation of China under Grant No U1404505the Program for Innovative Talent in University of Henan Province under Grant No16HASTIT010
文摘Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtained samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. The result of the magnetization of the obtained VN product as a function of temperature indicates that the onset superconducting transition temperature is about 8.4K. Furthermore, the possible reaction mechanism is also discussed.
文摘Glasses in the ternary system Cr2O3-PbO-P2O5 were prepared by direct melting of the mixture with stoichiometric proportions of the reagents Cr2O3, PbO and (NH4)2HPO4 at 1080℃. The glasses obtained are transparent in colour and have a non-hygroscopic appearance. The study of the dissolution rate was carried out on ternary glasses xCr2O3-(45-x)PbO-55P2O5 with (1 ≤ x ≤ 4;mol%), immersed in distilled water at 90℃ for 24 days, indicating a maximum of chemical durability when the level of chromium oxide passed through 2 mol%. Both, IR spectra and X-ray diffraction have indicated the predominance of metaphosphate or cyclic metaphosphate groups with some traces of isolated orthophosphate groups when the Cr2O3 content is equal to x = 2. Analysis of the density values also, has showed a maximum density for x = 2 mol%. The covalent radius values of oxygen have indicated that the minimum value rcal (O2–) is observed for x = 2 mol% and therefore a relatively high reinforcement of the metal-oxygen-phosphorus (Cr-O-P) bonds. SEM Micrographs have exhibited two phases, a vitreous phase and a crystalline phase. The radical change in the structure from ultraphosphate Q3 groups to ring metaphosphate Q2 and orthophosphate groups Q0 seems to be the cause of the formation of crystallites. Beyond 2 mol% of Cr2O3, the structure of the glass changed relatively and the orthophosphate phases increased to the detriment of the metaphosphate phases. We observed a decrease in chemical durability. However, it was confirmed that the dissolution rate (DR) of the S2 analysed compound is comparable to the values of borosilicate glasses which are used as alternative materials for the immobilisation of nuclear waste substances.
文摘Use of the regular melting-quench method allowed the isolation of a small glass domain within the ternary system Li2O-P2O5-Cr2O3 at 1000°C. Electrical conductivity and dielectric permittivity measures on sample glasses and ceramic glasses of this domain were performed at a frequency of 10 kHz and at temperatures between 25°C and 300°C. The values of dielectric permittivity and electrical conductivity increase with increasing Li2O content. However, increases of Cr2O3 content, even at low concentrations, induce a change in electrical conductivity behaviour from that of a glass to that of a ceramic glass. The introduction of an increasing amount of Li2O content in vitreous phosphorus pentoxide changes its three-dimensional network;rupture of the P-O-P bond then occurs and there is formation of easily polarisable entities with quite high values of . The vibrational spectroscopy technique I.R has allowed an efficient investigation of the structural change versus composition within the above indicated ternary diagram. The maximal dielectric permittivity obtained at 300°C, both for the glasses and for the ceramic glasses varied in the order 104 to 3 × 105, while the maximum electrical conductivity obtained at 300°C for the ceramic glasses was in the order of 10-3 Ωcm-1.
