Novel process for facile preparation of mesoporous silica-based materials with controllable pore structure from coal fly ash Author links open overlay panel

Extraction of silica from fly ash to produce mesoporous silica materials is one of the most important utilization approaches.Mesoporous silica could not be synthesized on a large-scale by conventional sol-gel method.In this paper,facile preparation of mesoporous silica with controllable pore structure from fly ash by the template-free process via two steps of mineral phase transformation and selective acid etching was proposed.The influence of crystalline structure and acid etching degree on structure of as-synthesized mesoporous silica materials was revealed,as well as mechanism of crystalline structure transformation and pore structure formation.The results show that mullite and quartz could be transformed into acid-soluble kaliophilite when fly ash reacted with K_(2)CO_(3)at temperature of 800-1100℃.The hexagonal kaliophilite would be transformed into orthorhombic KAlSiO_(4)-O1 phase when the temperature is controlled at 1100℃.Mesoporous silica with specific surface area of 475.93 m^(2)/g and 642.57 m^(2)/g could be synthesized from activated fly ash with kaliophilite and KAlSiO_(4)-O1 phase crystalline structure.By controlling the degree of acid etching,mesoporous silica materials with different pore structures can be obtained.This paper provides a cost-effective and large-scale process for the preparation of mesoporous silica materials with controllable pore structure from solid waste fly ash.

Dragging 3D printing technique controls pore sizes of tissue engineered blood vessels to induce spontaneous cellular assembly

To date,several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel(SDV)replacement.However,conventional artificial blood vessel grafts lack endothelium and,thus,are not ideal for SDV transplantation as they can cause thrombosis.In addition,a suc-cessful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external stresses.Here,we developed a spontaneous cellular assembly SDV(S-SDV)that develops without additional intervention.By improving the dragging 3D printing technique,SDV constructs with free-form,multilayers and controllable pore size can be fabricated at once.Then,The S-SDV filled in the natural poly-mer bioink containing human umbilical vein endothelial cells(HUVECs)and human aorta smooth muscle cells(HAoSMCs).The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV construct.The antiplatelet adhesion of the formed endothelium on the luminal surface was also confirmed.In addition,this S-SDV had sufficient mechanical properties(burst pressure,suture retention,leakage test)for transplantation.We believe that the S-SDV could address the challenges of conventional SDVs:notably,endothelial formation and mechanical properties.In particular,the S-SDV can be designed simply as a free-form structure with a desired pore size.Since endothelial formation through the pore is easy even in free-form con-structs,it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes,and in other tubular tissues such as the esophagus.

A high-volumetric-capacity bismuth nanosheet/graphene electrode for potassium ion batteries

Potassium ion batteries(PIBs)with high-volumetric energy densities are promising for next-generation low-cost energy storage devices.Metallic bismuth(Bi)with a structure similar to graphite,is a promising anode material for PIBs due to its high theoretical volumetric capacity(3763 mA h cm^−3)and relatively low working potential(−2.93 V vs.standard hydrogen electrode).However,it experiences severe capacity decay caused by a huge volume expansion of Bi when alloying with potassium.This study reports a flexible and free-standing Bi nanosheet(BiNS)/reduced graphene oxide composite membrane with designed porosity close to the expansion ratio of BiNS after charging.The controlled pore structure improves the electron and ion transport during cycling,and strengthens the structural stability of the electrode during potassiation and depotassiation,leading to excellent electrochemical performance for potassium-ion storage.In particular,it delivers a high reversible volumetric capacity of 451 mA h cm^−3 at the current density of 0.5 A g^−1,which is much higher than the previously reported commercial graphite material.