The sulfate groups in agar structure played a good role in the formation of fiber.However,commercially available agar is usually extracted from red algae by alkali treatment to decrease the content of sulfate group fo...The sulfate groups in agar structure played a good role in the formation of fiber.However,commercially available agar is usually extracted from red algae by alkali treatment to decrease the content of sulfate group for the purpose of high gel strength.In this paper,an alkali-free method of agar extraction from Gracilaria lemaneiformis was proposed for the wet-spinning purpose.This method is environmentally friendly,reduces the extraction steps,saves energy,and reduces the production cost of agar fiber.The improved agar preparation process not only has higher agar yield,but also has higher molecular weight and sulfate group content,which is beneficial to the preparation and forming of fiber and makes the fiber have higher mechanical strength and elongation.Therefore,this extraction technology has broad application prospect in the textile field.展开更多
Based on aluminum sulfate,a fluorine-free and alkali-free liquid accelerator(FF-AF-A)was prepared in this study.The setting time and compressive strength of three cement types with different FF-AF-A dosages were fully...Based on aluminum sulfate,a fluorine-free and alkali-free liquid accelerator(FF-AF-A)was prepared in this study.The setting time and compressive strength of three cement types with different FF-AF-A dosages were fully investigated.The compatibility of the FF-AF-A with the superplasticizers were also investigated,and the early hydration behavior and morphology of the hydration products of reference cement paste with the FF-AF-A were explored by hydration heat,X-ray diffractometry(XRD),and scanning electron microscopy(SEM).Test results indicated that adding the FF-AF-A at 8 wt%of the cement weight resulted in 2 min 35 s initial setting time and 6 min 30 s final setting time.The 1-day compressive strength of the cement mortar with 8 wt%of FF-AF-A reached 13.5 MPa,which represents an increase of 35%as compared to the strength of cement mortar without the FF-AF-A,and the 28-day compressive strength ratio was 119%.In addition,the FF-AF-A also showed good compatibility with different superplasticizer dosages.The results show that,when the FF-AF-A was added to the cement paste,it promoted the formation of ettringite crystals due to the aluminum ions(Al^(3+))and sulfate ions(SO_(4)^(2-))reacted with gypsum in the cement,as well as promoted the hydration of tricalcium aluminate(C_(3)A)and tricalcium silicate(C3S)leading to the overall structure becomes more compact.As a consequence,the hydration heat rate of the cement sharply increased,the cement paste setting time is shortened,and the compressive strength of cement mortar is improved.展开更多
基金supported by the Program of National Natural Science Foundation of China(52173037)Natural Science Foundation of Shandong Province(ZR2020ME061)+2 种基金Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(IRT14R30)State Key Laboratory of Bio-Fibers and Eco-Textiles of Qingdao University(ZFT201810,ZKT17)Yunnan Expert Workstation Project(202105AF150061).
文摘The sulfate groups in agar structure played a good role in the formation of fiber.However,commercially available agar is usually extracted from red algae by alkali treatment to decrease the content of sulfate group for the purpose of high gel strength.In this paper,an alkali-free method of agar extraction from Gracilaria lemaneiformis was proposed for the wet-spinning purpose.This method is environmentally friendly,reduces the extraction steps,saves energy,and reduces the production cost of agar fiber.The improved agar preparation process not only has higher agar yield,but also has higher molecular weight and sulfate group content,which is beneficial to the preparation and forming of fiber and makes the fiber have higher mechanical strength and elongation.Therefore,this extraction technology has broad application prospect in the textile field.
基金grateful funding provided by National Key Research and Development Program of China(Project 2019YFC1906202)Guangxi Key Research and Development Plan(Guike AB19259008)Major Science and Technology Special Project of Guangxi Province(Guike AA18242007-3).
文摘Based on aluminum sulfate,a fluorine-free and alkali-free liquid accelerator(FF-AF-A)was prepared in this study.The setting time and compressive strength of three cement types with different FF-AF-A dosages were fully investigated.The compatibility of the FF-AF-A with the superplasticizers were also investigated,and the early hydration behavior and morphology of the hydration products of reference cement paste with the FF-AF-A were explored by hydration heat,X-ray diffractometry(XRD),and scanning electron microscopy(SEM).Test results indicated that adding the FF-AF-A at 8 wt%of the cement weight resulted in 2 min 35 s initial setting time and 6 min 30 s final setting time.The 1-day compressive strength of the cement mortar with 8 wt%of FF-AF-A reached 13.5 MPa,which represents an increase of 35%as compared to the strength of cement mortar without the FF-AF-A,and the 28-day compressive strength ratio was 119%.In addition,the FF-AF-A also showed good compatibility with different superplasticizer dosages.The results show that,when the FF-AF-A was added to the cement paste,it promoted the formation of ettringite crystals due to the aluminum ions(Al^(3+))and sulfate ions(SO_(4)^(2-))reacted with gypsum in the cement,as well as promoted the hydration of tricalcium aluminate(C_(3)A)and tricalcium silicate(C3S)leading to the overall structure becomes more compact.As a consequence,the hydration heat rate of the cement sharply increased,the cement paste setting time is shortened,and the compressive strength of cement mortar is improved.
