Study On Fabrication, Structure And Properties Of Bamboo Charcoal And Bamboo Based SiC Ceramic

Bamboo charcoal and Bamboo based SiC as a new kind of environmentally conscious materials can be use as all kind of applications such as high-temperature exhaust gas filters, catalyst carriers, advanced microreactor systems, heat insulation, microbes or enzymes, and wastewater treatment, as well as mechanically loaded light-weight structures, etc. Phyllostachys pubescens, Dendrocalamus latifloeus, Dendrocalamopsis oldhami, Bambusa arundinacea bamboo was selected to produce charcoal with rational processing. The pyrolysis process, microstructure, phases, elements contents and physico-chemichal structure changes during bamboo –to-charcoal conversion were investigated by TGA, SEM, EDXA, XRD and so on. The electric conductivity properties and carbonization shrinkage of bamboo charcoal are also researched. The structure and properties of bamboo charcoals prepared by four kinds of bamboos are compared. Four kinds of bamboo charcoal were infiltrated as templates using liquid Si at high temperature to produce bamboo based SiC ceramic. The microstructure, phases, elements contents and physico-chemichal structure changes of 4 kinds of bamboo based SiC ceramic during charcoal –to-ceramic conversion were also investigated. The infiltration and reaction mechanism of bamboo charcoal-to-ceramic are also discussed . The compressive mechanical behavior of bamboo, bamboo charcoal and bamboo based SiC ceramic was tested and the relationship between structure and compressive mechanical behavior was analyzed. Digital Image Correlation Method(DSCM) are used to analyze the dynamic damage process of bamboo charcoal and bamboo based SiC ceramic. The research is very significative for the basic theory research of bamboo charcoal and bamboo based SiC ceramic . Based on sound date and experiment , the research content and conclusion are as followed: (1) Four species of bamboos are selected for preparing bamboo charcoal and bamboo based SiC ceramic, and the basic physical and chemistry properties are analyzed such as bamboo wall thickness ,water content , density and chemical compositions and tissue measurement. The result show that the wall thickness of four kinds of bamboos is 12.03-14.96mm.The largest density of bamboo is Phyllostachys pubescens with 0.75 g/cm3,and the smallest is Bambusa arundinacea with 0.53 g/cm3.The fiber caps area of Bambusa arundinacea is the largest among the four kinds bamboo with 36.37%-43.31%,at the same time with the smallest of vessel at 2.59%-2.77%. Fundamental tissues area of Phyllostachys pubescens is the largest with 66.87%-73.74%。(2) A unique process for conversion of monolithic bamboo structures to carbons that retain the cellular structure of the wood without the formation of cracks and other defects associated with charcoal materials is described. biological carbon performs were derived from bamboo by pyrolysis at different temperature(500℃,750℃,1000℃)under N2 atmosphere. (3) The bamboo pyrolysis process was studied by TGA, and the weight loss rate in different pyrolysis period of four kinds of bamboo with one and five year old are compared. The reason about the weight loss is large in TGA than in electric furnace is analyzed . The carbonization shrinkage in different species, age and direction are research. The result show that bamboo pyrolysis process include water absorberd, weight steady, rapid weight loss and slow weight , the weight loss rate of 1 year old bamboo is more high than 5 year old. The carbonization shrinkage rate is bottom >under> middle>top; the shrinkage of axial with the scope of 15-21%is more smaller than tangential and radial with the scope of 27%-48%; with the increasing of carbonization temperature , the carbonization shrinkage rate increases. After 500℃,750℃and 1000℃carbonization temperature ,the diameter of traverse section shrinkage is18-21%,25-38%and 28-40%. (4) The micro-structure of four kinds bamboo and bamboo charcoal are characterized and compared by SEM. Bamboo charcoal basically inhabit the honeycomb character and anisotropy microstructure of bamboo, but some change can be observed. The fundamental system and vascular system of bamboo and bamboo charcoal are compared. (5) The elements in carbon out surface ,middle and inner surface are tested by EDAX and the relationship between carbonization temperature and element content are analyzed. The elements in carbon surface is C,O,Si,Al,K and the most element content is Al,Si and the At% is 9.75%一54.79% and 32.78%一83.23%.Carbon ash content is mainly come from carbon surface.With the increasing of carbon temperature, thecarbonization degree increases and the rate of C/O decrease.The micro-crystal structure of bamboo and bamboo charcoal in different carbonization temperature are tested. The micro-crystal structure are analyzed during the conservation processing of bamboo-bamboo charcoal. The element related to electric conductivity of bamboo charcoal such as fracture, element content, micro-crystal structure and carbonization temperature are analyzed. The result show that micro-crystal structure of bamboo charcoal incline to transitional state of ordered graphite with the increasing of carbonization temperature. The electric conductivity increase directly related to the carbonization temperature increasing and there is a change point in 750 ℃carbonization temperature because the increasing of carbonization temperature led to the change of fracture , structure and chemical composite of bamboo charcoal. (6) Bamboo based SiC ceramic are fabricated from four kinds bamboo charcoal templates by liquid Silicon infiltration at 1450℃. The structure and properties of bamboo based SiC ceramic prepared by four kinds of bamboo charcoal are compared. Genic material theory was use to analyzed Bamboo based SiC ceramic. (7) The materials composite and element distribution of four species bamboo based SiC ceramic are test by XRD and EDAX. The microstructure changes of four species during charcoal –to-ceramic conversion were also investigated and compared including fundamental system and vascular system. The SiC ceramic prepared by this technique was multi-phase solid, composed of 6H-SiC,3C-SiC SiC and free-Silicon and C. (8) The compressive mechanics behavior of bamboo, bamboo charcoal and bamboo based SiC ceramic are test. The compressive strength of bamboo is 23.57-75.72Mpa,and 1.2-34.48Mpa for bamboo charcoal, 32-970 Mpa for based SiC ceramic.The strain-stress,compressive strength, dynamic damage process and damage fracture are analyzed and compared in parallel and perpendicular to fiber direction. Deformation Field Evolution of bamboo charcoal and bamboo based SiC ceramic including the strain field evolution and crack propagation are inspected using DSCM technique. (9) Pore distribution of bamboo charcoal are observed and tested using SEM and Penetrometer (AutoPore IV 9500),Pore theory are use to analyzed the liquid Si infiltration trace and the infiltration and reaction theory of Si and C are discussed.