The aging behavior of softening composite solid propellant was investigated by measuring its mechanical and ballistic prosperities during prolonged storage at elevated and room temperatures. Accelerated aging was cond...The aging behavior of softening composite solid propellant was investigated by measuring its mechanical and ballistic prosperities during prolonged storage at elevated and room temperatures. Accelerated aging was conducted at 65 °C for 231 days while the normal aging was performed at 25 ± 3 °C and relative humidity less than 50% for 8 years. The mechanical properties were obtained from uniaxial tensile tests for the aged propellant specimens while the ballistic properties were determined from static firing tests of subscale motors aged for 112 days at 65 °C. The mechanical results show that the maximum tensile strength and Young's modulus initially increase and subsequently decrease with increasing aging time, while the maximum tensile strain generally increases with increasing aging time. The ballistic properties like burning rate show a small change which cannot affect the ballistic performance. The experimental results show that the changes in the mechanical properties are significant during the aging period, but the burning rate does not undergo significant changes. From this study, it is observed that the propellant ages through a combination of reactions like post-cure, oxidative cross-linking, chain scission, and hydrolysis. The chain scission and the hydrolysis effect are the most significant process, which makes the propellant soft and extendible. The observed aging mechanism has been modeled using an exponential function with two terms which can describe the complex behavior of the aging. By applying Arrhenius equation,the activation energy values were obtained based on the propellant mechanical properties. The shelf life of this propellant formulation at 25 °C is predicted to be 13 years using the modulus as failure criteria and control parameter.展开更多
Fluoride processing of natural ilmenite with the use of ammonium hydrogen difluoride (NH4HF2) as an effective fluorinating agent is suggested. Chemistry, composition, structure, thermal and hydrolytic properties of fl...Fluoride processing of natural ilmenite with the use of ammonium hydrogen difluoride (NH4HF2) as an effective fluorinating agent is suggested. Chemistry, composition, structure, thermal and hydrolytic properties of fluorination products were investigated. Ammonium fluoro- and oxofluorotitanates are suitable for preparing of titanium dioxide as pigmentary product or as doped by nitrogen and fluorine.展开更多
Considering the serious barriers/issues induced by the accumulated starch generated in white water system of old corrugated cardboard(OCC)pulping process,large amounts of accumulated starch in white water would be dec...Considering the serious barriers/issues induced by the accumulated starch generated in white water system of old corrugated cardboard(OCC)pulping process,large amounts of accumulated starch in white water would be decomposed by microorganisms and could not be utilized,thereby resulting in severe resource wastage and environmental pollution.This study mainly explored the effects of biodegradation/hydrolysis conditions of the two types of starch substrates(native starch and enzymatically(α-amylase)hydrolyzed starch),which were treated via microorganism degradation within the simulated white water from OCC pulping system and their biodegradation products on the key properties were characterized via X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),and gel permeation chromatography(GPC)technologies.The effects of system temperature,pH value,starch concentration,and biodegradation time on starch biodegradation ratio and the characteristics of obtained biodegradated products from the two types of starches were studied.In addition,the effect ofα-amylase dosage on the biodegradation ratio of enzymatically hydrolyzed starch and its properties was investigated.It was found that the native starch presented a maximal degradation ratio at a system temperature of 55℃and pH value range of 5-7,respectively,the corresponding starch concentration within simulated white water system was 200 mg/L.Whereas the enzymatically hydrolyzed starch exhibited a highest degradation ratio at a system temperature of 50℃and pH value of 5.5,respectively,and the corresponding starch concentration within simulated white water system was 100 mg/L.It was verified that native starch is more readily bio-hydrolyzed and biodegradation-susceptive by microorganisms in simulated white water system of OCC pulping process,while the enzymatically hydrolyzed starch exhibits better biodegradation/hydrolysis resistance to the microbial degradation than that of native starch.This study provides a practical and interesting approach to inves展开更多
Owing to its excellent high-temperature resistance and high conductivity,zirconium diboride(ZrB_(2)) has been applied as an infrared suppression coating.However,ZrB_(2)is susceptible to hydrolysis under high-moisture ...Owing to its excellent high-temperature resistance and high conductivity,zirconium diboride(ZrB_(2)) has been applied as an infrared suppression coating.However,ZrB_(2)is susceptible to hydrolysis under high-moisture conditions and even under mild working temperatures.The improvement in the hydrophobicity of the ZrB_(2)surface effectively reduces wetting by water and suppresses hydrolysis reaction,particularly under high-temperature and high-moisture conditions.Herein,we report a novel,easy,and highly reproducible method for producing a fully coated ZrB_(2)surface by developing a nanoscale hydrophobic layer of glassy LaF_(3)on the surface of ZrB_(2)powder particles in situ(i.e.,during the carbothermal synthesis of ZrB_(2)).Through the tests carried out at 200 ℃for 100-300 h in a hydrothermal reactor,the produced powders displayed remarkably high long-term hydrolysis resistance and pronounced chemical stability.Compared with treated ZrB_(2),ZrB_(2)@LaF_(3)remained lower infrared emissivity when continuously intensifying hydrolyzation process.The results suggest that a nanoscale surface modification strategy can be applied to stabilize the infrared emissivity of ZrB_(2)in a water-oxygen coupling environment.展开更多
(Mg-10wt%Ni)-10wt%Ce(Mg10Ni10Ce)was ball-milled with SnO_(2)nanotubes and Mg10Ni10Ce-xSnO_(2)(x¼0,5,10 and 15 wt%)composites have been prepared.The phase compositions,microstructures,morphologies and hydrolysis H...(Mg-10wt%Ni)-10wt%Ce(Mg10Ni10Ce)was ball-milled with SnO_(2)nanotubes and Mg10Ni10Ce-xSnO_(2)(x¼0,5,10 and 15 wt%)composites have been prepared.The phase compositions,microstructures,morphologies and hydrolysis H2 generation performance in different aqueous systems(distilled water,tap water and simulated seawater)have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10CeeSnO_(2)has been proposed.Adding a small amount of SnO_(2)nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce,especially the initial hydrolysis kinetics and the final H_(2) generation yield.Unfortunately,the Mg10Ni10Ce-xSnO_(2)hardly reacts with distilled water at room temperature.The hydrolysis reaction rate of Mg10Ni10Cee5SnO_(2)composite in tap water is still very slow with only 17.3%generation yield after 1 h at 303 K.Fortunately,in simulated seawater(3.5 wt%NaCl solution),the hydrolytic H2 generation behavior of the Mg10Ni10Cee5SnO_(2)composite has been greatly improved,which can release as high as 468.6 mL g^(-1 )H_(2) with about 60.9%generation yield within 30 s at 303 K.The Cl destroys the passivation layer on MgeNieCe alloy surface and the added SnO_(2)nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield.The Mg10Ni10Cee5SnO_(2)composite can rapidly generate a large amount of H2 in simulated seawater in a short time,which is expected to be applied on portable H2 generators in the future.展开更多
The effects of sulfuric acid-associated mechanical pretreatment on the hydrolysis behavior of pine sawdust were investigated in this study.Sulfuric acid could act as an acidic catalyst to depolymerize holocellulose th...The effects of sulfuric acid-associated mechanical pretreatment on the hydrolysis behavior of pine sawdust were investigated in this study.Sulfuric acid could act as an acidic catalyst to depolymerize holocellulose through cleavage of the glycosidic bonds,the dissociation energies of which were supplied by the impact of a ball on pine sawdust,during milling.The destruction of glycosidic and hydrogen bonds in pine sawdust resulted in a decrease of crystallinity and an increase of water solubility.The sulfuric acid could promote the hydrolysis of holocellulose and its hydrolysis products.It also destroyed the chemical linkages between holocellulose and lignin during ball milling.The cleavage of chemical linkages with holocellulose made lignin more difficult to hydrolyze in subcritical water,and higher activation energy was needed to hydrolyze pretreated pine sawdust at higher reaction temperatures.It also led to the formation of glucose char and aromatic-linked polymer char from the hydrolysis products of holocellulose.展开更多
文摘The aging behavior of softening composite solid propellant was investigated by measuring its mechanical and ballistic prosperities during prolonged storage at elevated and room temperatures. Accelerated aging was conducted at 65 °C for 231 days while the normal aging was performed at 25 ± 3 °C and relative humidity less than 50% for 8 years. The mechanical properties were obtained from uniaxial tensile tests for the aged propellant specimens while the ballistic properties were determined from static firing tests of subscale motors aged for 112 days at 65 °C. The mechanical results show that the maximum tensile strength and Young's modulus initially increase and subsequently decrease with increasing aging time, while the maximum tensile strain generally increases with increasing aging time. The ballistic properties like burning rate show a small change which cannot affect the ballistic performance. The experimental results show that the changes in the mechanical properties are significant during the aging period, but the burning rate does not undergo significant changes. From this study, it is observed that the propellant ages through a combination of reactions like post-cure, oxidative cross-linking, chain scission, and hydrolysis. The chain scission and the hydrolysis effect are the most significant process, which makes the propellant soft and extendible. The observed aging mechanism has been modeled using an exponential function with two terms which can describe the complex behavior of the aging. By applying Arrhenius equation,the activation energy values were obtained based on the propellant mechanical properties. The shelf life of this propellant formulation at 25 °C is predicted to be 13 years using the modulus as failure criteria and control parameter.
文摘Fluoride processing of natural ilmenite with the use of ammonium hydrogen difluoride (NH4HF2) as an effective fluorinating agent is suggested. Chemistry, composition, structure, thermal and hydrolytic properties of fluorination products were investigated. Ammonium fluoro- and oxofluorotitanates are suitable for preparing of titanium dioxide as pigmentary product or as doped by nitrogen and fluorine.
基金financial support from the China Postdoctoral Science Foundation (No. 2022M712379, No. 2021M692401)National Natural Science Foundation of China (No. 32101470)+3 种基金Foundation (No. 2021KF37) of Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control,College of Light Industry and Food Engineering, Guangxi UniversityFoundation of Tianjin Key Laboratory of Pulp & Paper of Tianjin University of Science & Technology (No. 202003, No. 202106)Research Foundation from the University of New BrunswickPost-Doctoral Fellow Programs from Zhejiang Jingxing Paper Co., Ltd
文摘Considering the serious barriers/issues induced by the accumulated starch generated in white water system of old corrugated cardboard(OCC)pulping process,large amounts of accumulated starch in white water would be decomposed by microorganisms and could not be utilized,thereby resulting in severe resource wastage and environmental pollution.This study mainly explored the effects of biodegradation/hydrolysis conditions of the two types of starch substrates(native starch and enzymatically(α-amylase)hydrolyzed starch),which were treated via microorganism degradation within the simulated white water from OCC pulping system and their biodegradation products on the key properties were characterized via X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),and gel permeation chromatography(GPC)technologies.The effects of system temperature,pH value,starch concentration,and biodegradation time on starch biodegradation ratio and the characteristics of obtained biodegradated products from the two types of starches were studied.In addition,the effect ofα-amylase dosage on the biodegradation ratio of enzymatically hydrolyzed starch and its properties was investigated.It was found that the native starch presented a maximal degradation ratio at a system temperature of 55℃and pH value range of 5-7,respectively,the corresponding starch concentration within simulated white water system was 200 mg/L.Whereas the enzymatically hydrolyzed starch exhibited a highest degradation ratio at a system temperature of 50℃and pH value of 5.5,respectively,and the corresponding starch concentration within simulated white water system was 100 mg/L.It was verified that native starch is more readily bio-hydrolyzed and biodegradation-susceptive by microorganisms in simulated white water system of OCC pulping process,while the enzymatically hydrolyzed starch exhibits better biodegradation/hydrolysis resistance to the microbial degradation than that of native starch.This study provides a practical and interesting approach to inves
基金financially supported by the National Natural Science Foundation of China(Nos.51802037 and 51972046)Sichuan Science and Technology Program(No.2020JDRC0045)
文摘Owing to its excellent high-temperature resistance and high conductivity,zirconium diboride(ZrB_(2)) has been applied as an infrared suppression coating.However,ZrB_(2)is susceptible to hydrolysis under high-moisture conditions and even under mild working temperatures.The improvement in the hydrophobicity of the ZrB_(2)surface effectively reduces wetting by water and suppresses hydrolysis reaction,particularly under high-temperature and high-moisture conditions.Herein,we report a novel,easy,and highly reproducible method for producing a fully coated ZrB_(2)surface by developing a nanoscale hydrophobic layer of glassy LaF_(3)on the surface of ZrB_(2)powder particles in situ(i.e.,during the carbothermal synthesis of ZrB_(2)).Through the tests carried out at 200 ℃for 100-300 h in a hydrothermal reactor,the produced powders displayed remarkably high long-term hydrolysis resistance and pronounced chemical stability.Compared with treated ZrB_(2),ZrB_(2)@LaF_(3)remained lower infrared emissivity when continuously intensifying hydrolyzation process.The results suggest that a nanoscale surface modification strategy can be applied to stabilize the infrared emissivity of ZrB_(2)in a water-oxygen coupling environment.
基金the National Natural Science Foundation of China(Grant Nos.51704188,51702199,61705125 and 51802181)the State Key Laboratory of Solidification Processing in NWPU(Grant No.SKLSP201809)+1 种基金Shaanxi Natural Science Foundation(Grant No.2019JQ-099)Research Starting Foundation from Shaanxi University of Science and Technology(Grant No.2016GBJ-04).
文摘(Mg-10wt%Ni)-10wt%Ce(Mg10Ni10Ce)was ball-milled with SnO_(2)nanotubes and Mg10Ni10Ce-xSnO_(2)(x¼0,5,10 and 15 wt%)composites have been prepared.The phase compositions,microstructures,morphologies and hydrolysis H2 generation performance in different aqueous systems(distilled water,tap water and simulated seawater)have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10CeeSnO_(2)has been proposed.Adding a small amount of SnO_(2)nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce,especially the initial hydrolysis kinetics and the final H_(2) generation yield.Unfortunately,the Mg10Ni10Ce-xSnO_(2)hardly reacts with distilled water at room temperature.The hydrolysis reaction rate of Mg10Ni10Cee5SnO_(2)composite in tap water is still very slow with only 17.3%generation yield after 1 h at 303 K.Fortunately,in simulated seawater(3.5 wt%NaCl solution),the hydrolytic H2 generation behavior of the Mg10Ni10Cee5SnO_(2)composite has been greatly improved,which can release as high as 468.6 mL g^(-1 )H_(2) with about 60.9%generation yield within 30 s at 303 K.The Cl destroys the passivation layer on MgeNieCe alloy surface and the added SnO_(2)nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield.The Mg10Ni10Cee5SnO_(2)composite can rapidly generate a large amount of H2 in simulated seawater in a short time,which is expected to be applied on portable H2 generators in the future.
基金supported by the National Natural Science Foundation of China(22078225)the Natural Science Foundation of Zhejiang Province(LGF22E080025 and LHY22E080005)。
文摘The effects of sulfuric acid-associated mechanical pretreatment on the hydrolysis behavior of pine sawdust were investigated in this study.Sulfuric acid could act as an acidic catalyst to depolymerize holocellulose through cleavage of the glycosidic bonds,the dissociation energies of which were supplied by the impact of a ball on pine sawdust,during milling.The destruction of glycosidic and hydrogen bonds in pine sawdust resulted in a decrease of crystallinity and an increase of water solubility.The sulfuric acid could promote the hydrolysis of holocellulose and its hydrolysis products.It also destroyed the chemical linkages between holocellulose and lignin during ball milling.The cleavage of chemical linkages with holocellulose made lignin more difficult to hydrolyze in subcritical water,and higher activation energy was needed to hydrolyze pretreated pine sawdust at higher reaction temperatures.It also led to the formation of glucose char and aromatic-linked polymer char from the hydrolysis products of holocellulose.
