A novel wet-chemical method for the preparation of silver flakes was studied. The well-defined particles were prepared by directly adding FeSO4 solution into AgNO3 solution containing citric acid at an agitation speed...A novel wet-chemical method for the preparation of silver flakes was studied. The well-defined particles were prepared by directly adding FeSO4 solution into AgNO3 solution containing citric acid at an agitation speed of 150 r/min at room temperature. The products were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that particles are irregular thin silver flakes. And the sizes of them range from 2 to 10 μm. It is found that citric acid plays an important role in the formation of sliver flakes. There is an optimum amount of citric acid for the preparation of silver flakes by this method. It is also found that high reduction rate is favorable for the formation of silver flakes.展开更多
Europium orthophosphate monohydrate （EuPO4·H2O） nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diet...Europium orthophosphate monohydrate （EuPO4·H2O） nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diethylene glycol （DEG） and polyethylene glycol （PEG） polymers as well as the pH values on the size, crystalline structure and morphology of EuPO4·H2O nanorods were investigated. Field emission scanning electron microscopy （FESEM） and X-ray diffraction （XRD） data of the prepared samples were elucidated. The nanorods were highly uniform and their mean length was reduced by using DEG and PEG as soft template agents. For all prepared samples, the rhabdophanetype hexagonal EuPO4·H2O was the dominated phase. The photoluminescence （PL） spectroscopy measurements of EuPO4·H2O nanorods revealed that, under UV excitation, EuPO4·H2O nanorods exhibited strong luminescence with narrow bands corresponding to the intra-4f transitions of ^5D0→^7Fj （j=1, 2, 3, 4） of Eu^3＋ ions. The peaks were found at 594 nm （^5D0→^7F1）, 619 nm （^5D0→^7F2）, 652 nm （^5D0→^7F3）, and 697 nm （^5D0→^7F4）, with the strongest emission at 594 nm.展开更多
Disodium hydrogen phosphate dodecahydrate （Na2HPO4·12H2O） is an attractive candidate for phase change materials. The main problem for its practical use comes from incongruent melting character during thermal cy...Disodium hydrogen phosphate dodecahydrate （Na2HPO4·12H2O） is an attractive candidate for phase change materials. The main problem for its practical use comes from incongruent melting character during thermal cycling. Experimentally, heat of fusion of the pure salt decreased from 200 to 25 jog 1 in a four-run freeze-thaw cycling. Additives such as thickening agent or in-situ synthesized polyacrylate sodium in the molten salt can prevent its phase separation to some extent. In the test, sodium alginate 3.0%-5.0% （w/w） thickened mixture containing Na2HPOn·12H2O and some water showed constant heat storage capacities. Polyacrylate sodium gelled salt was synthesized through polymerizing sodium acrylate in the melt of Na2HPOn·12H2O and some extra water at 50 ℃. Optimum conditions composed of sodium acrylate 3.0%-5.0% （w/w）, cross-linking agent N,N-methylenebis-acrylamide 0.10%-0.20% （w/w）, K2S208 and Na2SO3 （mass ratio 1 ; 1） 0.06%-0.12% （w/w）. As opposed to normal large crystals of pure Na2HPOn·12H2O in solid state, the gelled salt existed in a large number of tiny particles dispersed in the gel network at room temperature, commonly less than 2 mm. But only those sample particles with sizes less than 0.2 mm may have relatively stable thermal storage property. A problem encountered was the poor reproducibility of the synthesis method： heat storage capacity of the product was often very different even though the synthesis was carried out in the same conditions. An alternative gelling method by sodium alginate grafted sodium acrylate was tried and it showed a fairly good effect. Heat capacities and heat of fusion of Na2HPO4·12H2O were measured by an adiabatic calorimeter.展开更多
基金Project(B20121806)supported by the Science and Technology Research Program of Education Department of Hubei Province,China
文摘A novel wet-chemical method for the preparation of silver flakes was studied. The well-defined particles were prepared by directly adding FeSO4 solution into AgNO3 solution containing citric acid at an agitation speed of 150 r/min at room temperature. The products were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that particles are irregular thin silver flakes. And the sizes of them range from 2 to 10 μm. It is found that citric acid plays an important role in the formation of sliver flakes. There is an optimum amount of citric acid for the preparation of silver flakes by this method. It is also found that high reduction rate is favorable for the formation of silver flakes.
基金Project supported by Vietnam's National Foundation for Science and Technology Development (103.06.46.09)
文摘Europium orthophosphate monohydrate （EuPO4·H2O） nanorods with typical dimensions of about 10-30 nm in diameter and 300-500 nm in length were prepared by using the soft template method. The effects of using diethylene glycol （DEG） and polyethylene glycol （PEG） polymers as well as the pH values on the size, crystalline structure and morphology of EuPO4·H2O nanorods were investigated. Field emission scanning electron microscopy （FESEM） and X-ray diffraction （XRD） data of the prepared samples were elucidated. The nanorods were highly uniform and their mean length was reduced by using DEG and PEG as soft template agents. For all prepared samples, the rhabdophanetype hexagonal EuPO4·H2O was the dominated phase. The photoluminescence （PL） spectroscopy measurements of EuPO4·H2O nanorods revealed that, under UV excitation, EuPO4·H2O nanorods exhibited strong luminescence with narrow bands corresponding to the intra-4f transitions of ^5D0→^7Fj （j=1, 2, 3, 4） of Eu^3＋ ions. The peaks were found at 594 nm （^5D0→^7F1）, 619 nm （^5D0→^7F2）, 652 nm （^5D0→^7F3）, and 697 nm （^5D0→^7F4）, with the strongest emission at 594 nm.
基金Project supported by the National Natural Science Foundation of China （No. 20373072）.
文摘Disodium hydrogen phosphate dodecahydrate （Na2HPO4·12H2O） is an attractive candidate for phase change materials. The main problem for its practical use comes from incongruent melting character during thermal cycling. Experimentally, heat of fusion of the pure salt decreased from 200 to 25 jog 1 in a four-run freeze-thaw cycling. Additives such as thickening agent or in-situ synthesized polyacrylate sodium in the molten salt can prevent its phase separation to some extent. In the test, sodium alginate 3.0%-5.0% （w/w） thickened mixture containing Na2HPOn·12H2O and some water showed constant heat storage capacities. Polyacrylate sodium gelled salt was synthesized through polymerizing sodium acrylate in the melt of Na2HPOn·12H2O and some extra water at 50 ℃. Optimum conditions composed of sodium acrylate 3.0%-5.0% （w/w）, cross-linking agent N,N-methylenebis-acrylamide 0.10%-0.20% （w/w）, K2S208 and Na2SO3 （mass ratio 1 ; 1） 0.06%-0.12% （w/w）. As opposed to normal large crystals of pure Na2HPOn·12H2O in solid state, the gelled salt existed in a large number of tiny particles dispersed in the gel network at room temperature, commonly less than 2 mm. But only those sample particles with sizes less than 0.2 mm may have relatively stable thermal storage property. A problem encountered was the poor reproducibility of the synthesis method： heat storage capacity of the product was often very different even though the synthesis was carried out in the same conditions. An alternative gelling method by sodium alginate grafted sodium acrylate was tried and it showed a fairly good effect. Heat capacities and heat of fusion of Na2HPO4·12H2O were measured by an adiabatic calorimeter.
