Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hyd...Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate. The hydration characteristics, the resistance to hydrodynamic water, and the mineralogical studies were investigated. The experimental results suggest that activated by K2SO4 and hemihydrate, anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives. The binder has proper setting time, good strength development, and relatively better resistance to water. The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.展开更多
Phosphogypsum（PG） calcined at 500 ℃ was activated by K2SO4 and salt lime with loose structure as seed crystal. To determine the effect of activation, hydration of the anhydrate PG activated was investigated by exam...Phosphogypsum（PG） calcined at 500 ℃ was activated by K2SO4 and salt lime with loose structure as seed crystal. To determine the effect of activation, hydration of the anhydrate PG activated was investigated by examination of the setting time, the proportion of hydrated anhydrate PG, the microstructure of the hardenite and the resistance to water. Results show that activated anhydrate PG hydrates much more rapidly than that in the absence of activators. The activated anhydrate PG has proper setting time and hydrated proportion. The resistance to water was greatly improved. SEM photos show that the set activated PG has hydrated products of rod-like and closely connected crystals. The different addition of activator leads to different compact structure.展开更多
In this work,phosphogypsum(PG) with a small amount of lime was thermally pretreated at 450 ℃ to produce anhydrate gypsum for the purpose of searching new ways for utilization of waste PG. Additives,K2SO4 and one sele...In this work,phosphogypsum(PG) with a small amount of lime was thermally pretreated at 450 ℃ to produce anhydrate gypsum for the purpose of searching new ways for utilization of waste PG. Additives,K2SO4 and one selected seed crystal(SC),were used as activator for anhydrate PG. The hydration characteristics of the anhydrate PG binders were investigated by determination of the setting time,the ratio of hydrated anhydrate PG,the compressive strength development,and the microstructure of the hardenite. The resistance to water was studied by measuring mass loss of binders exposed to hydrodynamic water. Results suggest that activated by K2SO4 and SC,anhydrate PG hydrates much more rapidly than that without additives. The anhydrate PG binder with K2SO4 and SC has proper setting time and good strength developments. SEM photos show that the set binders have hydrated products of rodlike and regularly shaped crystals. Those crystals connected closely,and the hardenite has a compact structure,which is beneficial to the obtainment of good properties.展开更多
In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous...In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous MgCl_(2) prepared by the dehydration of bischofite is a high-quality raw material for the production of Mg.However,direct calcination of MgCl_(2)·6H_(2)O in industrial dehydration processes leads to a large amount of hydrolysis.The by-products are harmful to the electrolysis process of Mg,causing problems such as sludge formation,low current efficiency,and corrosion in the electrodes.To obtain high-purity anhydrous MgCl_(2),different advanced dehydration processes have been proposed.In this review,we focus on the recent progress of the dehydration process.Firstly,we discuss the molecular structure of MgCl_(2)·6H_(2)O and explain the reason why much hydrolysis occurs in dehydration.Secondly,we introduce the specific dehydration processes,mainly divided into direct dehydration processes and indirect dehydration processes.The direct dehydration processes are classified into gas protection heating and molecular sieve dehydration process.Indirect dehydration processes are classified into thermal dehydration of ammonium carnallite(NH_(4)Cl·MgCl_(2)·6H_(2)O),thermal dehydration of potassium carnallite(KCl·MgCl_(2)·6H_(2)O),thermal decomposition of the[HAE]Cl·MgCl_(2)·6H_(2)O,organic solvent distillation,ionic liquid dehydration process and ammonia complexation process.In the meanwhile,purity of anhydrous MgCl_(2) of each dehydration process,as well as the advantages and disadvantages,is discussed.The characteristics of different processes with a simple economic budget are also given in this paper.Finally,the main challenges are evaluated with suggested directions in the future,aiming to guide the synthesis of high-purity anhydrous MgCl_(2).展开更多
High-purity AlF3 was prepared by the combined process of leaching the raw material of waste aluminum electrolytes with aluminum chloride,electrolyzing the leaching solution,and then mixing with ammonium hydrogen fluor...High-purity AlF3 was prepared by the combined process of leaching the raw material of waste aluminum electrolytes with aluminum chloride,electrolyzing the leaching solution,and then mixing with ammonium hydrogen fluoride for roasting.Under the optimal leaching conditions of a fluorine to aluminum molar ratio of 2.0,a liquid-to-solid ratio of 12,a temperature of 90℃,and time of 4 h,the fluorine leaching rate can reach 99.15%.Under the action of electrolysis,the H+is reduced to H2 in the cathode,while the remaining OH−combines with AlF^(2+)and AlF^(2+)to precipitate aluminium hydroxyfluoride hydrate.The results show that electrolysis is beneficial to reduce the impurity content of aluminium hydroxyfluoride hydrate.When the current density is 0.2 A/cm^(2),the temperature is 90℃,the stirring speed is 200 r/min,and the electrolysis endpoint pH is 3.0,the total content of Na,K and Ca impurities in the precipitation is only 0.64 wt.%.Moreover,the hydrolysis can be inhibited effectively by adding ammonium hydrogen fluoride in the mixed-roasting process.When the mass ratio of aluminium hydroxyfluoride hydrate to ammonium hydrogen fluoride is 2꞉1,the purity of the AlF3 product is even 99.51 wt.%.Conducively,the high-purity AlF_(3)can be returned to the aluminum electrolysis industry or used as a reagent.展开更多
Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The e...Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The extended information of the mechanical properties of shale formation is crucial for designing a successful hydraulic fracturing operation.On the other hand,the mechanical properties of such organic-rich formations are greatly affected by the mechanical characteristics of the present kerogen(organic matter),which dramatically changes during the maturation process.In this study,a Qingshankou shale sample containing kerogen type I is mechanically investigated at different maturity levels using the grid nanoindentation approach.To this end,the original immature sample is artificially matured during hydrous(HP)and anhydrous(AHP)pyrolysis.More than 930 nanoindentation tests were performed on grids of 9×8 on the surface of 13 samples with different maturities.The test results showed that the presence of water during pyrolysis can significantly affect the shale sample's mechanical characteristics.In higher temperatures and higher levels of maturity,the role of water becomes more pronounced.During hydrous pyrolysis,kerogen produces larger amounts of oil and bitumen,which become progressively porous.While the original sample showed a Young's modulus value of more than 48 GPa,and it fluctuated between approximately 19 and 32 GPa during the HP scenario and between 17 and 34 GPa during the AHP process.In terms of hardness,the original sample exhibited an initial value of about 1.1 GPa and more mature samples reflected hardness values in the range of approximately 0.3 and 0.97 GPa in both scenarios.According to the trends of mechanical properties during maturation,mechanical properties decreased at the initial stage of maturation and remained relatively constant during the oil window.Then,another decline was detected at the wet-gas window's closure.In the dry-gas window,HP and AHP scenarios exhibited different behaviors mainly due to the chemical structure of the kerogen residue.展开更多
The absence of humic vitrinite complicates the determination of thermal maturity in pre-Devonian sediments.Lower Paleozoic shales contain structured zooclasts,solid bitumen,and vitrinite-like materials,and their refle...The absence of humic vitrinite complicates the determination of thermal maturity in pre-Devonian sediments.Lower Paleozoic shales contain structured zooclasts,solid bitumen,and vitrinite-like materials,and their reflectances have been found to be valid maturity proxies.Yet there remains much controversy as to the degree of evolution of reflectances.The current work aims to investigate the reflectance of dispersed organic matter(DOM),as well as their transformation degree and organic pore development.To this end,this study evaluated an Upper Ordovician zooclasts-bearing shale and a Middle Jurassic coal sample via anhydrous-pyrolysis to compare differences in the maturation pathways between marine-derived DOM and terrigenous vitrinite.These two original samples were cut into small blocks and placed in an identical vacuum stainless vessel simultaneously.The pyrolysis was carried out at isothermal temperatures ranging from 250 to 550℃ for 48 h.The morphologic and reflectance changes of DOM in pyrolysis residues were studied and compared with previous pyrolysis results.Adopting the combined use of optical reflectance and scanning electron microscope(SEM)techniques,the study shows that DOM in the shale components consists of solid bitumen(SB),bituminite,chitinozoans,a few graptolites,vitrinite-like particles(VLP),alginate and liptodetrinite.The reflectance sequence,from high to low,is zooclasts,VLP and SB.Their reflectances gradually increases as the pyrolysis temperature rises,although the rate of growth is slower than that of co-heating coal vitrinite.Notably,zooclasts yield significantly higher reflectance values than those of VLP and SB at each pyrolysis temperature.However,the VLP undergoes two distinct phases in reflectance development,despite gradual morphology changes similar to vitrinite.Based on evidence of the optical texture and organic pore evolution,we argue that a fair amount of VLP in studied Upper Ordovician shale does not consist of graptolite-type fragments.Consequently,the VLPRo serves as a reliable indicator for assessing organic matter maturity in Ordovician shales with a reflectance value of less than 2.0%.This investigation enhances scholarly understandings of marine-derived DOM evolution issues,providing clearer correlations among reflectances of different DOM and reducing uncertainties in thermal maturity determination.展开更多
BACKGROUND Current disinfection methods for gastrointestinal endoscopes consume a significant amount of water resources and produce a large volume of waste.AIM To achieve the objectives of efficiency,speed,and cost-ef...BACKGROUND Current disinfection methods for gastrointestinal endoscopes consume a significant amount of water resources and produce a large volume of waste.AIM To achieve the objectives of efficiency,speed,and cost-effectiveness,this study utilized vaporized hydrogen peroxide(VHP)generated from sodium percarbonate granules to conduct an anhydrous disinfection test on gastrointestinal endoscopes.METHODS The experimental device rapidly converts sodium percarbonate granules into VHP,and performs disinfection experiments on gastrointestinal endoscope models,disposable endoscopes,and various types of reusable gastrointestinal endoscopes.Variables such as the intraluminal flow rate(FR),relative humidity(RH),exposure dosage,and organic burden are used to explore the factors influencing the disinfection of long and narrow lumens with VHP.RESULTS The device generates a certain concentration of VHP that can achieve high-level disinfection of endoscope models within 30 minutes.RH,exposure dosage,and organic burden significantly affect the disinfection efficacy of VHP,whereas the intraluminal FR does not significantly impact disinfection efficacy.All ten artificially contaminated disposable endoscopes achieved satisfactory disinfection results.Furthermore,when this device was used to treat various types of reusable endoscopes,the disinfection and sterilization effects were not significantly different from those of automatic endoscope disinfection machines(using peracetic acid disinfectant solution)(P>0.05),and the economic cost of disinfectant required per endoscope was lower(1.5 China Yuan),with a shorter disinfection time(30 minutes).CONCLUSION The methods and results of this study provide a basis for further research on the use of VHP for the disinfection of gastrointestinal endoscopes,as well as for the development of anhydrous disinfection technology for gastrointestinal endoscopes.展开更多
The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impeda...The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impedance techniques.The results revealed that no active-passive transition is presented in the cyclic voltammogram,and the anodic current density increases with the increase of solution temperature,TBAHS concentration,potential scan rate and water content.The apparent activation energy is about 43.389 kJ/mol and the dissolution process is diffusion-controlled.Potentiostatic measurements showed that the current density gradually decays to a steady value when the potential is low;however,when the potential is higher than a certain value,the current density initially declines to a minimum value and then increases gradually.The resistance of passive film decreases with increasing potential,and inductive loops are presented when the potential is higher than 2.0 V.展开更多
NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY cata‐lysts by a high temperature anhydrous interaction between the support and copper （II） acety‐lacetonate Cu（acac）2. The...NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY cata‐lysts by a high temperature anhydrous interaction between the support and copper （II） acety‐lacetonate Cu（acac）2. The catalysts were used for the oxidative carbonylation of methanol to dime‐thyl carbonate （DMC） at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X‐ray diffraction, scanning electron microscopy, N2 ad‐sorption‐desorption, temperature programmed reduction of H2, X‐ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4＋exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4＋exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4＋exchange degree of NaNH4Y, the content of surface bound Cu＋active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu＋content reached its maximum when the NH4＋ex‐change degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/（g·h） space time yield of DMC, 6.9%conversion of methanol, 68.5%selectivity of DMC.展开更多
Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for de...Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone （2-PAP）, was investigated over several ce-sium-exchanged polyoxometalate （Cs-POM） catalysts. Decomposition of 2-PAP can follow two dif-ferent mechanisms： an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox proper-ties of the catalysts. The catalysts of POMs perform the following functions： promoting active hy-drogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen libera-tion and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP （〉99%） with excellent selectivities to the desired products （98.6% for phenol and 91.1% for acetophenone） can be achieved.展开更多
The corrosion behavior of tantalum in tetraethyl ammonium chloride （TEA） ethanol solutions was investigated using potentiodynamic polarization, cyclic voltammetry, and impedance techniques along with scanning electr...The corrosion behavior of tantalum in tetraethyl ammonium chloride （TEA） ethanol solutions was investigated using potentiodynamic polarization, cyclic voltammetry, and impedance techniques along with scanning electron microscopy （SEM）. At the early stage of scanning, the current density in the cyclic voltammetry curves very slowly increased because of the presence of a thin oxide film on the electrode surface. Pitting corrosion then occurred as a result of the passivity breakdown caused by the aggressive attack of the Cl^- anions. SEM images showed the growth process of the pits on the electrode surface. The pitting potential decreased with the increase in TEA concentration but increased with the increase in water concentration. The apparent activation energy of the electrochemical reaction was 36 kJ/mol. The impedance spectra exhibited two time constants for all the potentials. Both the passive layer resistance and the charge transfer resistance decreased with the increase in the potential.展开更多
High-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride.The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pi...High-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride.The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pinpointed.The effect of sample dimension on the above critical stages was investigated respectively.The purity guarantee mechanism of anhydrous magnesium chloride was proposed.After that,magnesium metal was obtained via electrolyzing the anhydrous magnesium chloride-containing molten salt.The new process for the continuous production of magnesium metal from magnesia was proposed and discussed.The incomplete chlorination reaction and the hydrolysis of anhydrous magnesium chloride are the two critical stages affecting the purity of the anhydrous magnesium chloride.The dimension of the sample can influence reaction process and reaction mechanism,and thus the problems of incomplete chlorination reaction and hydrolysis can be solved together.The magnesia content in anhydrous magnesium chloride was below 0.1 wt.%when the ratio of height to diameter of the sample was over 2.43.The content of impurities in the magnesium metal obtained met the specifications of the product Mg9980.The current efficiency was(94.7±1.8)%and the electricity consumption was(9107±97)kW h/t.展开更多
Carbide slag was used as an activator to improve the activity of anhydrous phosphogypsum.Carbide slag could greatly improve the mechanical strength of anhydrous phosphogypsum than K_(2)SO_(4).The compressive strength ...Carbide slag was used as an activator to improve the activity of anhydrous phosphogypsum.Carbide slag could greatly improve the mechanical strength of anhydrous phosphogypsum than K_(2)SO_(4).The compressive strength of 11 wt%carbide slag and 1 wt%K_(2)SO_(4)activated anhydrous phosphogypsum increased greatly to 8.6 MPa at 3 d,and 11.9 MPa at 7 d,and 16.0 MPa at 28 d,respectively.The rate of hydration heat was accelerated and the total hydration heat was increased,and more calcium sulfate dihydrate was formed and cross-linked with other parts which improved the compressive strength of anhydrous phosphogypsum under the effects of different activators.It was indicated that carbide slag was a highly effective and cost-efficient activator.The result provides a highly effective and low-cost method which results in a novel and high value-added method for the utilization of phosphogypsum in the future.展开更多
A series of coesite,coexisting with or without a liquid phase,was synthesized in the nominal system SiO2-H2O at800-1450℃and 5 GPa.Micro-Raman spectroscopy was used to identity the crystalline phase,electron microprob...A series of coesite,coexisting with or without a liquid phase,was synthesized in the nominal system SiO2-H2O at800-1450℃and 5 GPa.Micro-Raman spectroscopy was used to identity the crystalline phase,electron microprobe and LA-ICP-MS were employed to quantity some major and trace elements,and unpolarized FTIR spectroscopy was applied to probe the different types of hydrogen defects,explore water-incorporation mechanisms and quantify water contents.Trace amounts of A1 and B were detected in the coesite.Combining our results with the results in the literatures,we have found no positive correlation between the Al contents and the"Al"-based hydrogen concentrations,suggesting that previously proposed hydrogen-incorporation mechanism H^++Al^3+■Si^4+does not function in coesite.In contrast,we have confirmed the positive correlation between the B contents and the B-based hydrogen concentrations.The hydrogen-incorporation mechanism H^++B3^+■Si^4+readily takes place in coesite at different P-T conditions,and significantly increases the water content at both liquid-saturated and liquid-undersaturated conditions.For the SiO2-H2O system,we have found that type-Ⅰhydrogarnet substitution plays a dictating role in incorporating water into coesite at liquid-saturated condition,type-II hydrogarnet substitution contributes significantly at nearly dry condition,and both operate at conditions in between.The water solubility of coesite,as dictated by the type-Ⅰhydrogarnet substitution,positively correlates with both P and T,cH2O=-105(30)+5.2(32)×P+0.112(26)×T,with cH2O in wt ppm,P in GPa and T in℃.Due to its low water solubility and small fraction in subducted slabs,coesite may contribute insignificantly to the vertical water transport in subduction zones.Furthermore,the water solubility of any coesite in exhuming ultra-high pressure metamorphic rocks should be virtually zero as coesite becomes metastable.With an adequately fast waterdiffusion rate,this metastable coesite should be completely dry,which may have been the key factor to the partial preservation of most natural Coe.As a byproduct,a new IR experimental protocol for accurate water determination in optically anisotropic nominally anhydrous minerals has been found.Aided with the empirical method of Paterson(1982)it employs multiple unpolarized IR spectra,collected from randomly-orientated mineral grains,to approximate both total integrated absorbance and total integrated molar absorption coefficient.Its success relies on a high-level orientation randomness in the IR analyses.展开更多
Given the increased circulation time after fishing,a series of changes take place in live clams,leading to a deterioration in quality even after death.Thus,in this study,we aimed to explore the optimal mode of transpo...Given the increased circulation time after fishing,a series of changes take place in live clams,leading to a deterioration in quality even after death.Thus,in this study,we aimed to explore the optimal mode of transportation of clams.The container for holding clams was reformed,and a water circulation temperature control system was established.The physiological responses of clams during anhydrous and watery transportation at two temperatures(4 and 15℃)were investigated based on the aforementioned system.When comparing the transportation patterns after 3 d of transport,a higher survival rate was observed at 4℃(97%)than at 15℃(63%)in the anhydrous transportation groups and a lower survival rate was observed at 4℃(93%)than at 15℃(99%)in the watery transportation groups.In addition,the glycogen content,condition index(CI),and adenylate energy charge(A.E.C)value were higher at4℃((40.87±0.99)mg g^(-1),13.71%±0.50%and 57.45%±1.60%)than at 15℃((30.54±0.81)mg g^(-1),9.09%±0.30%and 43.12%±1.65%)in the anhydrous transportation groups.In the watery transportation groups,a lower glycogen content,CI,and A.E.C.value were observed at 4℃((33.78±0.84)mg g^(-1),9.78%±0.50%and 64.65%±1.25%)than at 15℃((41.53±0.93)mg g^(-1),12.72%±0.83%and 71.58%±1.27%).Results from this study show that anhydrous transportation(4℃)is the optimal transport condition for clams to maintain a high quality and good physiological conditions.Thus,this study will be particularly useful for establishing shellfish transportation systems.展开更多
Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a ...Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.展开更多
This paper reported an efficient and economical method for preparation of anhydrous LaBr3 for scintillation crystal growth. High purity anhydrous LaBr3 powders in large quantities were successfully obtained by stepped...This paper reported an efficient and economical method for preparation of anhydrous LaBr3 for scintillation crystal growth. High purity anhydrous LaBr3 powders in large quantities were successfully obtained by stepped dehydration of LaBr3-7H2O using NH4Br as additive. Experiments revealed that adding proper amount of NHaBr could effectively restrain the hydrolysis of LaBr3 during dehydration and thus decreased the yield of deleterious impurity of LaOBr. Optimum preparation conditions, including the amount of NH4Br in use, the dehydration temperature and atmosphere, were investigated by DTA/TG and water/oxygen analysis. The Raman characterization of the as-prepared anhydrous LaBr3 was also presented.展开更多
Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1∶1 of MgCl2 to NH4Cl, ammonium carnallite was synth...Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1∶1 of MgCl2 to NH4Cl, ammonium carnallite was synthesized. And then the ammonium carnallite was dehydrated to some extent at 160℃ for 4 h. Ammonium carnallite reacted with ammonia at 240℃ for 150 min and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750℃ into anhydrous magnesium chloride containing only 0.1%（mass fraction） of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1∶4 at high temperature and with the differential pressure of NH3 above 30.5kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410℃, and then calcined at 700℃ into anhydrous magnesium chloride with only 0.087%（mass fraction） of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn’t mixed phases, the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.展开更多
基金Funded by the National Natural Science Foundation of China (No. 50802019)
文摘Lime pretreated phosphogypsum（PG） was calcined at 500 ℃ to produce anhydrate gypsum cement. Due to the slow hydration of anhydrate gypsum, additives, K2SO4 and hemihydrate gypsum were selected to accelerate the hydration of anhydrate. The hydration characteristics, the resistance to hydrodynamic water, and the mineralogical studies were investigated. The experimental results suggest that activated by K2SO4 and hemihydrate, anhydrate PG hydrates much more rapidly than that in the presence of only K2SO4 or in the absence of additives. The binder has proper setting time, good strength development, and relatively better resistance to water. The hardened binder has hydrated products of rod or stick like shaped dihydrate gypsum crystals.
基金Funded by the National Natural Science Foundation of China(No.50802019)
文摘Phosphogypsum（PG） calcined at 500 ℃ was activated by K2SO4 and salt lime with loose structure as seed crystal. To determine the effect of activation, hydration of the anhydrate PG activated was investigated by examination of the setting time, the proportion of hydrated anhydrate PG, the microstructure of the hardenite and the resistance to water. Results show that activated anhydrate PG hydrates much more rapidly than that in the absence of activators. The activated anhydrate PG has proper setting time and hydrated proportion. The resistance to water was greatly improved. SEM photos show that the set activated PG has hydrated products of rod-like and closely connected crystals. The different addition of activator leads to different compact structure.
基金support provided by the National Natural Science Foundation of China (Project NO.50802019)the Introduction of Research Personnel Foundation of Guizhou University(Project No.2008019)
文摘In this work,phosphogypsum(PG) with a small amount of lime was thermally pretreated at 450 ℃ to produce anhydrate gypsum for the purpose of searching new ways for utilization of waste PG. Additives,K2SO4 and one selected seed crystal(SC),were used as activator for anhydrate PG. The hydration characteristics of the anhydrate PG binders were investigated by determination of the setting time,the ratio of hydrated anhydrate PG,the compressive strength development,and the microstructure of the hardenite. The resistance to water was studied by measuring mass loss of binders exposed to hydrodynamic water. Results suggest that activated by K2SO4 and SC,anhydrate PG hydrates much more rapidly than that without additives. The anhydrate PG binder with K2SO4 and SC has proper setting time and good strength developments. SEM photos show that the set binders have hydrated products of rodlike and regularly shaped crystals. Those crystals connected closely,and the hardenite has a compact structure,which is beneficial to the obtainment of good properties.
基金funded by Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01F60)Tianshan Talents Plan of Xinjiang Uygur Autonomous Region(2022TSYCJC0001)+2 种基金National Natural Science Foundation of China(22368051)Science and Technology Plan Project of Karamay(20232023hjcxrc0038 and 2024hjcxrc0118)Projects of Talents Recruitment of GDUPT(2023rcyj2005)。
文摘In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous MgCl_(2) prepared by the dehydration of bischofite is a high-quality raw material for the production of Mg.However,direct calcination of MgCl_(2)·6H_(2)O in industrial dehydration processes leads to a large amount of hydrolysis.The by-products are harmful to the electrolysis process of Mg,causing problems such as sludge formation,low current efficiency,and corrosion in the electrodes.To obtain high-purity anhydrous MgCl_(2),different advanced dehydration processes have been proposed.In this review,we focus on the recent progress of the dehydration process.Firstly,we discuss the molecular structure of MgCl_(2)·6H_(2)O and explain the reason why much hydrolysis occurs in dehydration.Secondly,we introduce the specific dehydration processes,mainly divided into direct dehydration processes and indirect dehydration processes.The direct dehydration processes are classified into gas protection heating and molecular sieve dehydration process.Indirect dehydration processes are classified into thermal dehydration of ammonium carnallite(NH_(4)Cl·MgCl_(2)·6H_(2)O),thermal dehydration of potassium carnallite(KCl·MgCl_(2)·6H_(2)O),thermal decomposition of the[HAE]Cl·MgCl_(2)·6H_(2)O,organic solvent distillation,ionic liquid dehydration process and ammonia complexation process.In the meanwhile,purity of anhydrous MgCl_(2) of each dehydration process,as well as the advantages and disadvantages,is discussed.The characteristics of different processes with a simple economic budget are also given in this paper.Finally,the main challenges are evaluated with suggested directions in the future,aiming to guide the synthesis of high-purity anhydrous MgCl_(2).
文摘High-purity AlF3 was prepared by the combined process of leaching the raw material of waste aluminum electrolytes with aluminum chloride,electrolyzing the leaching solution,and then mixing with ammonium hydrogen fluoride for roasting.Under the optimal leaching conditions of a fluorine to aluminum molar ratio of 2.0,a liquid-to-solid ratio of 12,a temperature of 90℃,and time of 4 h,the fluorine leaching rate can reach 99.15%.Under the action of electrolysis,the H+is reduced to H2 in the cathode,while the remaining OH−combines with AlF^(2+)and AlF^(2+)to precipitate aluminium hydroxyfluoride hydrate.The results show that electrolysis is beneficial to reduce the impurity content of aluminium hydroxyfluoride hydrate.When the current density is 0.2 A/cm^(2),the temperature is 90℃,the stirring speed is 200 r/min,and the electrolysis endpoint pH is 3.0,the total content of Na,K and Ca impurities in the precipitation is only 0.64 wt.%.Moreover,the hydrolysis can be inhibited effectively by adding ammonium hydrogen fluoride in the mixed-roasting process.When the mass ratio of aluminium hydroxyfluoride hydrate to ammonium hydrogen fluoride is 2꞉1,the purity of the AlF3 product is even 99.51 wt.%.Conducively,the high-purity AlF_(3)can be returned to the aluminum electrolysis industry or used as a reagent.
基金supported by the National Natural Science Foundation of China(Grant No.U22A20574)the Hainan Province Science and Technology Special Fund(Grant No.ZDYF2023GXJS009).
文摘Shale formations have recently gained plenty of attention owing to their large amounts of reserves.Horizontal drilling and hydraulic fracturing are the proposed approaches for the development of shale formations.The extended information of the mechanical properties of shale formation is crucial for designing a successful hydraulic fracturing operation.On the other hand,the mechanical properties of such organic-rich formations are greatly affected by the mechanical characteristics of the present kerogen(organic matter),which dramatically changes during the maturation process.In this study,a Qingshankou shale sample containing kerogen type I is mechanically investigated at different maturity levels using the grid nanoindentation approach.To this end,the original immature sample is artificially matured during hydrous(HP)and anhydrous(AHP)pyrolysis.More than 930 nanoindentation tests were performed on grids of 9×8 on the surface of 13 samples with different maturities.The test results showed that the presence of water during pyrolysis can significantly affect the shale sample's mechanical characteristics.In higher temperatures and higher levels of maturity,the role of water becomes more pronounced.During hydrous pyrolysis,kerogen produces larger amounts of oil and bitumen,which become progressively porous.While the original sample showed a Young's modulus value of more than 48 GPa,and it fluctuated between approximately 19 and 32 GPa during the HP scenario and between 17 and 34 GPa during the AHP process.In terms of hardness,the original sample exhibited an initial value of about 1.1 GPa and more mature samples reflected hardness values in the range of approximately 0.3 and 0.97 GPa in both scenarios.According to the trends of mechanical properties during maturation,mechanical properties decreased at the initial stage of maturation and remained relatively constant during the oil window.Then,another decline was detected at the wet-gas window's closure.In the dry-gas window,HP and AHP scenarios exhibited different behaviors mainly due to the chemical structure of the kerogen residue.
基金supported by National Natural Science Foundation of China(Nos.42202172,U24B6001,41830424)the Fundamental Research Funds for the Central Universities,CHD(300102274202).
文摘The absence of humic vitrinite complicates the determination of thermal maturity in pre-Devonian sediments.Lower Paleozoic shales contain structured zooclasts,solid bitumen,and vitrinite-like materials,and their reflectances have been found to be valid maturity proxies.Yet there remains much controversy as to the degree of evolution of reflectances.The current work aims to investigate the reflectance of dispersed organic matter(DOM),as well as their transformation degree and organic pore development.To this end,this study evaluated an Upper Ordovician zooclasts-bearing shale and a Middle Jurassic coal sample via anhydrous-pyrolysis to compare differences in the maturation pathways between marine-derived DOM and terrigenous vitrinite.These two original samples were cut into small blocks and placed in an identical vacuum stainless vessel simultaneously.The pyrolysis was carried out at isothermal temperatures ranging from 250 to 550℃ for 48 h.The morphologic and reflectance changes of DOM in pyrolysis residues were studied and compared with previous pyrolysis results.Adopting the combined use of optical reflectance and scanning electron microscope(SEM)techniques,the study shows that DOM in the shale components consists of solid bitumen(SB),bituminite,chitinozoans,a few graptolites,vitrinite-like particles(VLP),alginate and liptodetrinite.The reflectance sequence,from high to low,is zooclasts,VLP and SB.Their reflectances gradually increases as the pyrolysis temperature rises,although the rate of growth is slower than that of co-heating coal vitrinite.Notably,zooclasts yield significantly higher reflectance values than those of VLP and SB at each pyrolysis temperature.However,the VLP undergoes two distinct phases in reflectance development,despite gradual morphology changes similar to vitrinite.Based on evidence of the optical texture and organic pore evolution,we argue that a fair amount of VLP in studied Upper Ordovician shale does not consist of graptolite-type fragments.Consequently,the VLPRo serves as a reliable indicator for assessing organic matter maturity in Ordovician shales with a reflectance value of less than 2.0%.This investigation enhances scholarly understandings of marine-derived DOM evolution issues,providing clearer correlations among reflectances of different DOM and reducing uncertainties in thermal maturity determination.
基金Supported by the Joint Logistics Support Force Comprehensive Equipment Research Project,No.LB2023B010100-09.
文摘BACKGROUND Current disinfection methods for gastrointestinal endoscopes consume a significant amount of water resources and produce a large volume of waste.AIM To achieve the objectives of efficiency,speed,and cost-effectiveness,this study utilized vaporized hydrogen peroxide(VHP)generated from sodium percarbonate granules to conduct an anhydrous disinfection test on gastrointestinal endoscopes.METHODS The experimental device rapidly converts sodium percarbonate granules into VHP,and performs disinfection experiments on gastrointestinal endoscope models,disposable endoscopes,and various types of reusable gastrointestinal endoscopes.Variables such as the intraluminal flow rate(FR),relative humidity(RH),exposure dosage,and organic burden are used to explore the factors influencing the disinfection of long and narrow lumens with VHP.RESULTS The device generates a certain concentration of VHP that can achieve high-level disinfection of endoscope models within 30 minutes.RH,exposure dosage,and organic burden significantly affect the disinfection efficacy of VHP,whereas the intraluminal FR does not significantly impact disinfection efficacy.All ten artificially contaminated disposable endoscopes achieved satisfactory disinfection results.Furthermore,when this device was used to treat various types of reusable endoscopes,the disinfection and sterilization effects were not significantly different from those of automatic endoscope disinfection machines(using peracetic acid disinfectant solution)(P>0.05),and the economic cost of disinfectant required per endoscope was lower(1.5 China Yuan),with a shorter disinfection time(30 minutes).CONCLUSION The methods and results of this study provide a basis for further research on the use of VHP for the disinfection of gastrointestinal endoscopes,as well as for the development of anhydrous disinfection technology for gastrointestinal endoscopes.
基金Project(2007AA03Z425)supported by the Hi-tech Research and Development Program of ChinaProject(50404011)supported by the National Natural Science Foundation of China
文摘The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impedance techniques.The results revealed that no active-passive transition is presented in the cyclic voltammogram,and the anodic current density increases with the increase of solution temperature,TBAHS concentration,potential scan rate and water content.The apparent activation energy is about 43.389 kJ/mol and the dissolution process is diffusion-controlled.Potentiostatic measurements showed that the current density gradually decays to a steady value when the potential is low;however,when the potential is higher than a certain value,the current density initially declines to a minimum value and then increases gradually.The resistance of passive film decreases with increasing potential,and inductive loops are presented when the potential is higher than 2.0 V.
基金supported by the National Natural Science Foundation of China (21276169)~~
文摘NaY and ion exchanged NaNH4Y zeolite with NH4NO3 were used as the support to prepare CuY cata‐lysts by a high temperature anhydrous interaction between the support and copper （II） acety‐lacetonate Cu（acac）2. The catalysts were used for the oxidative carbonylation of methanol to dime‐thyl carbonate （DMC） at atmospheric pressure. The textural and acidic properties of NaNH4Y zeolite and the CuY catalysts were investigated by X‐ray diffraction, scanning electron microscopy, N2 ad‐sorption‐desorption, temperature programmed reduction of H2, X‐ray photoelectron spectroscopy and temperature programmed desorption of NH3. With increasing NH4NO3 concentration, the NH4＋exchange degree increased while the crystallinity of the zeolite remained intact. Crystalline CuO was formed when the NH4＋exchange degree of NaNH4Y was low, and the corresponding CuY catalyst showed low catalytic activity. With increasing of the NH4＋exchange degree of NaNH4Y, the content of surface bound Cu＋active centers increased and the catalytic activity of the corresponding CuY catalyst also increased. The surface bound Cu＋content reached its maximum when the NH4＋ex‐change degree of NaNH4Y reached towards saturation. The CuY exhibited optimal catalytic activity with 267.3 mg/（g·h） space time yield of DMC, 6.9%conversion of methanol, 68.5%selectivity of DMC.
基金supported by the National Key Basic Research Program of China(973 program,2013CB934101)National Natural Science Foundation of China(21433002,21573046)+1 种基金China Postdoctoral Science Foundation(2016M601492)International Science and Technology Cooperation Projects of Guangxi(15104001-5)~~
文摘Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone （2-PAP）, was investigated over several ce-sium-exchanged polyoxometalate （Cs-POM） catalysts. Decomposition of 2-PAP can follow two dif-ferent mechanisms： an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox proper-ties of the catalysts. The catalysts of POMs perform the following functions： promoting active hy-drogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen libera-tion and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP （〉99%） with excellent selectivities to the desired products （98.6% for phenol and 91.1% for acetophenone） can be achieved.
文摘The corrosion behavior of tantalum in tetraethyl ammonium chloride （TEA） ethanol solutions was investigated using potentiodynamic polarization, cyclic voltammetry, and impedance techniques along with scanning electron microscopy （SEM）. At the early stage of scanning, the current density in the cyclic voltammetry curves very slowly increased because of the presence of a thin oxide film on the electrode surface. Pitting corrosion then occurred as a result of the passivity breakdown caused by the aggressive attack of the Cl^- anions. SEM images showed the growth process of the pits on the electrode surface. The pitting potential decreased with the increase in TEA concentration but increased with the increase in water concentration. The apparent activation energy of the electrochemical reaction was 36 kJ/mol. The impedance spectra exhibited two time constants for all the potentials. Both the passive layer resistance and the charge transfer resistance decreased with the increase in the potential.
基金supported by the National Natural Science Foundation of China(51501178)Autonomous Research Fund of State Key Laboratory of Multiphase Complex Systems(MPCS-2019-A-10)。
文摘High-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride.The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pinpointed.The effect of sample dimension on the above critical stages was investigated respectively.The purity guarantee mechanism of anhydrous magnesium chloride was proposed.After that,magnesium metal was obtained via electrolyzing the anhydrous magnesium chloride-containing molten salt.The new process for the continuous production of magnesium metal from magnesia was proposed and discussed.The incomplete chlorination reaction and the hydrolysis of anhydrous magnesium chloride are the two critical stages affecting the purity of the anhydrous magnesium chloride.The dimension of the sample can influence reaction process and reaction mechanism,and thus the problems of incomplete chlorination reaction and hydrolysis can be solved together.The magnesia content in anhydrous magnesium chloride was below 0.1 wt.%when the ratio of height to diameter of the sample was over 2.43.The content of impurities in the magnesium metal obtained met the specifications of the product Mg9980.The current efficiency was(94.7±1.8)%and the electricity consumption was(9107±97)kW h/t.
基金Funded by Innovation Group Fund Project of Hubei Province(No.2020CFA039)the Key Research and Development Program of Hubei Province(No.2020BCA077)。
文摘Carbide slag was used as an activator to improve the activity of anhydrous phosphogypsum.Carbide slag could greatly improve the mechanical strength of anhydrous phosphogypsum than K_(2)SO_(4).The compressive strength of 11 wt%carbide slag and 1 wt%K_(2)SO_(4)activated anhydrous phosphogypsum increased greatly to 8.6 MPa at 3 d,and 11.9 MPa at 7 d,and 16.0 MPa at 28 d,respectively.The rate of hydration heat was accelerated and the total hydration heat was increased,and more calcium sulfate dihydrate was formed and cross-linked with other parts which improved the compressive strength of anhydrous phosphogypsum under the effects of different activators.It was indicated that carbide slag was a highly effective and cost-efficient activator.The result provides a highly effective and low-cost method which results in a novel and high value-added method for the utilization of phosphogypsum in the future.
基金financially supported by the DREAM project of MOST,China(Grant No.2016YFC0600408)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB18000000)the Program of the National Mineral Rock and Fossil Specimens Resource Center from MOST,China。
文摘A series of coesite,coexisting with or without a liquid phase,was synthesized in the nominal system SiO2-H2O at800-1450℃and 5 GPa.Micro-Raman spectroscopy was used to identity the crystalline phase,electron microprobe and LA-ICP-MS were employed to quantity some major and trace elements,and unpolarized FTIR spectroscopy was applied to probe the different types of hydrogen defects,explore water-incorporation mechanisms and quantify water contents.Trace amounts of A1 and B were detected in the coesite.Combining our results with the results in the literatures,we have found no positive correlation between the Al contents and the"Al"-based hydrogen concentrations,suggesting that previously proposed hydrogen-incorporation mechanism H^++Al^3+■Si^4+does not function in coesite.In contrast,we have confirmed the positive correlation between the B contents and the B-based hydrogen concentrations.The hydrogen-incorporation mechanism H^++B3^+■Si^4+readily takes place in coesite at different P-T conditions,and significantly increases the water content at both liquid-saturated and liquid-undersaturated conditions.For the SiO2-H2O system,we have found that type-Ⅰhydrogarnet substitution plays a dictating role in incorporating water into coesite at liquid-saturated condition,type-II hydrogarnet substitution contributes significantly at nearly dry condition,and both operate at conditions in between.The water solubility of coesite,as dictated by the type-Ⅰhydrogarnet substitution,positively correlates with both P and T,cH2O=-105(30)+5.2(32)×P+0.112(26)×T,with cH2O in wt ppm,P in GPa and T in℃.Due to its low water solubility and small fraction in subducted slabs,coesite may contribute insignificantly to the vertical water transport in subduction zones.Furthermore,the water solubility of any coesite in exhuming ultra-high pressure metamorphic rocks should be virtually zero as coesite becomes metastable.With an adequately fast waterdiffusion rate,this metastable coesite should be completely dry,which may have been the key factor to the partial preservation of most natural Coe.As a byproduct,a new IR experimental protocol for accurate water determination in optically anisotropic nominally anhydrous minerals has been found.Aided with the empirical method of Paterson(1982)it employs multiple unpolarized IR spectra,collected from randomly-orientated mineral grains,to approximate both total integrated absorbance and total integrated molar absorption coefficient.Its success relies on a high-level orientation randomness in the IR analyses.
基金This study is supported by the National Key R&D Program of China(No.2018YFD0901004)the Innovation Team Project of Hebei Province Modern Agricultural Industry Technology System(No.HBCT2018170207)+1 种基金the Innovation Center of Hebei Agricultural Products Processing Technology(No.199676183H)the Modern Agricultural Industry Technology System(No.CARS-49).
文摘Given the increased circulation time after fishing,a series of changes take place in live clams,leading to a deterioration in quality even after death.Thus,in this study,we aimed to explore the optimal mode of transportation of clams.The container for holding clams was reformed,and a water circulation temperature control system was established.The physiological responses of clams during anhydrous and watery transportation at two temperatures(4 and 15℃)were investigated based on the aforementioned system.When comparing the transportation patterns after 3 d of transport,a higher survival rate was observed at 4℃(97%)than at 15℃(63%)in the anhydrous transportation groups and a lower survival rate was observed at 4℃(93%)than at 15℃(99%)in the watery transportation groups.In addition,the glycogen content,condition index(CI),and adenylate energy charge(A.E.C)value were higher at4℃((40.87±0.99)mg g^(-1),13.71%±0.50%and 57.45%±1.60%)than at 15℃((30.54±0.81)mg g^(-1),9.09%±0.30%and 43.12%±1.65%)in the anhydrous transportation groups.In the watery transportation groups,a lower glycogen content,CI,and A.E.C.value were observed at 4℃((33.78±0.84)mg g^(-1),9.78%±0.50%and 64.65%±1.25%)than at 15℃((41.53±0.93)mg g^(-1),12.72%±0.83%and 71.58%±1.27%).Results from this study show that anhydrous transportation(4℃)is the optimal transport condition for clams to maintain a high quality and good physiological conditions.Thus,this study will be particularly useful for establishing shellfish transportation systems.
基金supported through the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical, Biological, and Geosciences Division under DE-SC0010379the support from an ECS Toyota Young Investigator Fellowship
文摘Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles.
基金Project supported by National Basic Research Program of China (2012CBA01207)
文摘This paper reported an efficient and economical method for preparation of anhydrous LaBr3 for scintillation crystal growth. High purity anhydrous LaBr3 powders in large quantities were successfully obtained by stepped dehydration of LaBr3-7H2O using NH4Br as additive. Experiments revealed that adding proper amount of NHaBr could effectively restrain the hydrolysis of LaBr3 during dehydration and thus decreased the yield of deleterious impurity of LaOBr. Optimum preparation conditions, including the amount of NH4Br in use, the dehydration temperature and atmosphere, were investigated by DTA/TG and water/oxygen analysis. The Raman characterization of the as-prepared anhydrous LaBr3 was also presented.
基金Project(2000 G 101) supported by the Key Science and Technology Research Project of Qinghai Province
文摘Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1∶1 of MgCl2 to NH4Cl, ammonium carnallite was synthesized. And then the ammonium carnallite was dehydrated to some extent at 160℃ for 4 h. Ammonium carnallite reacted with ammonia at 240℃ for 150 min and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750℃ into anhydrous magnesium chloride containing only 0.1%（mass fraction） of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1∶4 at high temperature and with the differential pressure of NH3 above 30.5kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410℃, and then calcined at 700℃ into anhydrous magnesium chloride with only 0.087%（mass fraction） of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn’t mixed phases, the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.
