Single-crystal alpha alumina （α-Al2O3） platelets were synthesized by calcining a powder mixture of bayerite （α-AI（OH）3） and potassium sulfate （K2SO4） at 900℃. The crystalline phase evolutions and morphologi...Single-crystal alpha alumina （α-Al2O3） platelets were synthesized by calcining a powder mixture of bayerite （α-AI（OH）3） and potassium sulfate （K2SO4） at 900℃. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The synthesized samples mainly consisted of single-crystal α-Al2O3 platelets with a diameter of 0.5-1.5 μm and a thickness of 50-150 nm. Moreover, with 3, 5, and 8 wt% （referred to the obtained alumina） α-Al2O3 seeds adding into the powder mixture of bayerite and potassium sulfate, the average diameter of α-Al2O3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the bayerite （α-Al（OH）3） → boehmite （γ-AIOOH） →γ-Al2O3 → α-Al2O3. Further analysis indicated that K2SO4 can promote the phase transformation from α-Al2O3 to α-Al2O3 and the formation of single-crystal α-Al2O3 platelets might be attributed to the liquid phase K3AI（SO4）3.展开更多
Most of water based drilling fluids easily penetrate into shale formations and cause serious problems such as well instability,destruction of the formation,wall pipe folding and pipe adhesion.The present research aims...Most of water based drilling fluids easily penetrate into shale formations and cause serious problems such as well instability,destruction of the formation,wall pipe folding and pipe adhesion.The present research aims to assess the effects of alumina nano-particles(alpha and gamma)on shale/clay stability due to the unique specifications of alumina(alpha and gamma)nano particles.The SEM,XRD,EDAX and AFM analyses of recovered shale samples indicate that the average size of alpha alumina nano-particles coating the shale surface and the pores existing in the shale is between 25 and 35 nm,whereas the average size of gamma alumina nano-particles coating the shale surface and the pores present in the shale is between 20 and 30 nm.In addition,samples recovered by nano-alpha reveal more porosity remained in the shale sample in comparison with the nano-gamma nano-sample.Furthermore,the results obtained from EDAX illustrate a suitable nano-gamma alumina over the recovered shale.The experiment with five types of drilling fluid without the presence of potassium chloride as an inhibitor salt designed.Thus,the water based drilling fluid containing nano-gamma alumina with less than 1%wt was chosen as the best sample.Generally,the presence of alumina nano-particles optimizes the stability of formations containing ions like shale.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 51102022 and 50872046)the China Postdoctoral Science Foundation (Grant No. 2011M501413)+1 种基金the Special Fund for Basic Scientific Research of Central Colleges, Changan University (Grant No. CHD2012ZD015)the Special Fund for Basic Research support programs of Chang an Univer sity
文摘Single-crystal alpha alumina （α-Al2O3） platelets were synthesized by calcining a powder mixture of bayerite （α-AI（OH）3） and potassium sulfate （K2SO4） at 900℃. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The synthesized samples mainly consisted of single-crystal α-Al2O3 platelets with a diameter of 0.5-1.5 μm and a thickness of 50-150 nm. Moreover, with 3, 5, and 8 wt% （referred to the obtained alumina） α-Al2O3 seeds adding into the powder mixture of bayerite and potassium sulfate, the average diameter of α-Al2O3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the bayerite （α-Al（OH）3） → boehmite （γ-AIOOH） →γ-Al2O3 → α-Al2O3. Further analysis indicated that K2SO4 can promote the phase transformation from α-Al2O3 to α-Al2O3 and the formation of single-crystal α-Al2O3 platelets might be attributed to the liquid phase K3AI（SO4）3.
文摘Most of water based drilling fluids easily penetrate into shale formations and cause serious problems such as well instability,destruction of the formation,wall pipe folding and pipe adhesion.The present research aims to assess the effects of alumina nano-particles(alpha and gamma)on shale/clay stability due to the unique specifications of alumina(alpha and gamma)nano particles.The SEM,XRD,EDAX and AFM analyses of recovered shale samples indicate that the average size of alpha alumina nano-particles coating the shale surface and the pores existing in the shale is between 25 and 35 nm,whereas the average size of gamma alumina nano-particles coating the shale surface and the pores present in the shale is between 20 and 30 nm.In addition,samples recovered by nano-alpha reveal more porosity remained in the shale sample in comparison with the nano-gamma nano-sample.Furthermore,the results obtained from EDAX illustrate a suitable nano-gamma alumina over the recovered shale.The experiment with five types of drilling fluid without the presence of potassium chloride as an inhibitor salt designed.Thus,the water based drilling fluid containing nano-gamma alumina with less than 1%wt was chosen as the best sample.Generally,the presence of alumina nano-particles optimizes the stability of formations containing ions like shale.
