“…The combustible gas products, such as CH 4 and H 2 , give rise to the high heat release during the combustion of PCS. Ceramization process of PCS as precursor of silicon carbide occurs at higher temperature than 700 °C 35 . Figure 3 TG and DTG curves of ( a ) PCS, MNH and MNH/PCS; ( b ) PE and PE/PCS; ( c ) PE/MNH and PE/MNH/PCS in air.…”
Polycarbosilane (PCS) was used for surface modification of magnesium hydroxide (MNH) to enhance the flame retardant effectiveness by forming cohesive binding between MgO particles with ceramic adhesive. Chemical interaction and ceramic reaction were revealed between PCS and MNH, which made for a compact, thermal stable and ceramic-like barrier during the combustion of polyethylene (PE). The flame retardancy of PE/MNH/PCS composites was greatly enhanced and a limiting oxygen index (LOI) of 35.0 was achieved at the PCS/MNH ratio of 4/26 in the composite with 30 wt.% PCS modified MNH. Such results were superior in terms of high LOI value at low global content of MNH. Thanks to the better shielding effect of the integrated and self-supporting ceramic char, the peak heat release rate (p-HRR) and the total heat release (THR) of PE/MNH/PCS composites with 50 wt.% PCS modified MNH were remarkably decreased by 36% and 25% in comparison with PE/MNH with 50 wt.% MNH, respectively. The ceramic reaction between PCS and MNH, the superior thermal stability due to crosslinked PCS and the good barrier function of cohesive ceramic layer play important roles in the effective flame retardant mechanism.
“…The combustible gas products, such as CH 4 and H 2 , give rise to the high heat release during the combustion of PCS. Ceramization process of PCS as precursor of silicon carbide occurs at higher temperature than 700 °C 35 . Figure 3 TG and DTG curves of ( a ) PCS, MNH and MNH/PCS; ( b ) PE and PE/PCS; ( c ) PE/MNH and PE/MNH/PCS in air.…”
Polycarbosilane (PCS) was used for surface modification of magnesium hydroxide (MNH) to enhance the flame retardant effectiveness by forming cohesive binding between MgO particles with ceramic adhesive. Chemical interaction and ceramic reaction were revealed between PCS and MNH, which made for a compact, thermal stable and ceramic-like barrier during the combustion of polyethylene (PE). The flame retardancy of PE/MNH/PCS composites was greatly enhanced and a limiting oxygen index (LOI) of 35.0 was achieved at the PCS/MNH ratio of 4/26 in the composite with 30 wt.% PCS modified MNH. Such results were superior in terms of high LOI value at low global content of MNH. Thanks to the better shielding effect of the integrated and self-supporting ceramic char, the peak heat release rate (p-HRR) and the total heat release (THR) of PE/MNH/PCS composites with 50 wt.% PCS modified MNH were remarkably decreased by 36% and 25% in comparison with PE/MNH with 50 wt.% MNH, respectively. The ceramic reaction between PCS and MNH, the superior thermal stability due to crosslinked PCS and the good barrier function of cohesive ceramic layer play important roles in the effective flame retardant mechanism.
“…To date, polycarbosilane has also been widely used for electric or photo conductor, photoresist, and nonlinear optical materials, as well as preceramic precursors for fabricating SiC fiber, powder, whiskers, composites, and nanomaterials [35][36][37][38]. To investigate its relationships and differences with polysilane for fabricating SiC ceramics, a comparative study on the thermal behavior of some polysilanes and polycarbosilanes was carried out by Shukla et al [39].…”
Section: Polycarbosilanementioning
confidence: 99%
“…Importantly, organosilicon polymer-derived SiC and Si 3 N 4 ceramics show remarkable properties such as mechanical strength, chemical stability, etc. Polycarbosilanes, which can be directly converted to SiC after the pyrolysis, have been widely used for fabricating SiC powders, foams, fibers, monoliths, coating, and composites [37,[95][96][97][98]. For example, Wang et al [37] prepared carbon-rich SiC powders via the pyrolysis of polycarbosilanes (Fig.…”
Section: Binary Silicon-based Ceramicsmentioning
confidence: 99%
“…SiC ceramics show high mechanical strength, high thermal shock resistance, low thermal expansion coefficient, good chemical stability at high temperature, and semi-conducting, which is recognized as a promising material for semiconductor and applied in extreme environments [37,95,114]. In biomedical applications, SiC has been proposed as a candidate for bone implants or coating due to the high mechanical strength and ability for loading and releasing antibiotics [115][116][117][118].…”
Polymer-derived ceramics (PDCs) strategy shows a great deal of advantages for the fabrication of advanced ceramics. Organosilicon polymers facilitate the shaping process and different silicon-based ceramics with controllable components can be fabricated by modifying organosilicon polymers or adding fillers. It is worth noting that silicate ceramics can also be fabricated from organosilicon polymers by the introduction of active fillers, which could react with the produced silica during pyrolysis. The organosilicon polymer-derived ceramics show many unique properties, which have attracted many attentions in various fields. This review summarizes the typical organosilicon polymers and the processing of organosilicon polymers to fabricate silicon-based ceramics, especially highlights the three-dimensional (3D) printing technique for shaping the organosilicon polymerderived ceramics, which makes the possibility to fabricate silicon-based ceramics with complex structure. More importantly, the recent studies on fabricating typical non-oxide and silicate ceramics derived from organosilicon polymers and their biomedical applications are highlighted.
“…Another group 10 increased the conductivity by 5 orders of magnitude, which was attained by the formation of a C free related percolation path in pristine amorphous PDC SiC system. 23 When it forms a percolative network, carbon is the main conductive phase in PDC. 24 Dalcanale et al 14 even without increasing pyrolysis temperature, by adjusting the amount of thermal initiator used divinylenzene (DVB) to enrich the amorphous pristine PDC with C free , thus increasing the DC conductivity (RT) maximum up to 1 S/cm.…”
This paper studies the effect of pyrolysis temperature on the semiconductor-conductor transition of pristine polymer-derived ceramic silicon carbide (PDC SiC). A comprehensive study of microstructural evolution and conduction mechanism of PDC SiC pyrolyzed at the temperature range of 1200°C-1800°C is presented. At relatively lower pyrolysis temperatures (1200°C-1600°C), the carbon phase goes through a microstructural evolution from amorphous carbon to nanocrystalline carbon. The PDC SiC samples behave as a semiconductor and the electron transport is governed by the band tail hopping (BTH) mechanism in low pyrolysis temperature (1300°C); by a mixed mechanism driven by band tail hopping and tunneling at intermediate temperature (1500°C). At higher pyrolysis temperatures (1700°C-1800°C), a percolative network of continuous turbostratic carbon is formed up along the grain boundary of the crystallized SiC. The samples demonstrate metal-like conductive response and their resistivity increases monotonically with the increasing measuring temperature.
K E Y W O R D Smetal-like conduction mechanism, pristine polymer derived ceramics, semiconductor-conductor transition, turbostratic carbon
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