Microstructure evolution and enhanced permeation of SiC membranes derived from allylhydridopolycarbosilane

Hydrogen Selective SiCH Inorganic–Organic Hybrid/γ-Al2O3 Composite Membranes

“…The temperatures for thermal conversion of AHPCS to highly cross-linked SiCH hybrid in this study was selected as 300, 400 and 500 °C based on the results obtained by the TG-MS analyses ( Figures S3 and S4 in ESI ) as well as FT-IR and Raman spectroscopic analyses for the heat-treated AHPCSs ( Figures S5 and S6 in ESI ). The thermal behavior of AHPCS has been already studied by several research groups [ 42 , 54 , 55 , 56 , 57 , 58 ], and the results obtained in this study were well consistent with those previously reported: As shown in Figure S2 , as-received AHPCS had a considerable amount of low molecular weight fraction below 1000. TG-MS analyses revealed the thermal decomposition of the low molecular weight fraction proceeded during the first weight loss at 100–300 °C and a second one from 350 to 500 °C by detecting gaseous species assigned to the fragments of carbosilane species ( Figures S3 and S4 ).…”

“…On the other hand, thermal cross-linking was observed up to 300 °C for the formation of ≡Si-CH 2 -CH 2 -CH 2 -Si≡ and/or ≡Si-CH(CH 3 )-CH 2 -Si≡ via hydrosilylation between ≡Si-H and ≡Si-CH 2 -CH=CH 2 groups in AHPCS, which was identified by the disappearance of the FT-IR absorption band at 1629 cm −1 attributed to the C=C bond of the allyl group [ 55 , 56 ] associated with the decrease in the relative FT-IR band intensities assigned to ν(Si-H) at 2123 cm −1 and δ(Si-H) at 947 cm −1 [ 55 , 56 ] ( Figure S5 ). At 400–700 °C, formation of ≡Si-Si≡ between Si-H and Si-CH 3 groups [ 42 ] was suggested by detecting gaseous species at the m/z ratio of 15 assigned to methane (CH 4 ; Figure S4b ). Since the thermal decomposition and cross-linking contentiously proceeded at 300–500 °C, the quantity of organic groups and microporosity of the SiCH hybrid differed depending on the specific heat treatment temperature in this temperature range.…”

“…Their synthesis by the Kumada rearrangement of polydimethylsilane (PDS) has been reported by Yajima et al [ 26 ]. Since polymer-derived amorphous silicon (oxy)carbide (SiC and SiCO) show excellent thermal and chemical stabilities [ 28 , 29 ], PDS [ 30 ], PCSs [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ] and PCS derivatives such as allyl-hydro-polycarbosilane (AHPCS) [ 38 , 39 , 40 , 41 , 42 ] have been applied as precursors of microporous amorphous SiOC [ 30 , 31 , 32 , 33 , 34 ] and SiC [ 29 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ] membranes to investigate their gas permeation properties mainly at high temperatures, T ≥ 200 °C. PCSs are also appropriate as functional Class II hybrids: The silicon-carbon (Si-C) backbone endows several attractive properties of PCSs such as high flexibility and excellent thermal, chemical and electrical stabilities [ 43 , 44 , 45 ].…”

“…(a) TG curve and total ion current chromatogram (TICC) under flowing He, and typical mass spectra recorded during (b) the first weight loss from100 to 250 °C and (c) the second weight loss from 350 to 500 °C, Figure S4: Continuous in-situ monitoring of gaseous species by mass spectrometry: (a) Fragments derived from low molecular weight fraction of as-received AHPCS during the first weight loss from 100 to 300 °C and the second one from 350 to 500 °C and (b) methane (CH 4 ) at 400 to 700 °C. (c) Fragments suggested for gaseous spices derived from low molecular weight fraction of as-received AHPCS (Equation (1)), m/z = 42 ((CH 2 ) 3 ) from AHPCS after cross-linking via hydrosilylation between ≡Si-H and CH 2 =CH-CH 2 -Si≡ (Equations (2) and (3)) and m/z = 15 (CH 4 ) due to the thermal crosslinking between ≡Si-H and ≡Si-CH 3 groups to afford ≡Si-Si≡ above 350 °C (Equation (4)) [ 42 ], Figure S5: FT-IR spectra for as-received AHPCS and those after heat treatment at 300 to 700 °C in Ar, Figure S6: Raman spectra for as-received and those AHPCS after heat treatment at 300 to 500 °C in Ar. Spectra indicated the heat-treated samples were free from graphite-like carbon typically detected at 1347.5 and 1596.5 cm −1 attributed to the D-band (for disordered graphite) and G-band (for the sp2 graphite network), respectively [ 59 , 60 ].…”

Pervaporation via silicon‐based membranes: Correlation and prediction of performance in pervaporation and gas permeation

“…Allylhydridopolycarbosilane (AHPCS, SMP‐10, Starfire Systems Incorporation, New York) and polytitanocarbosilane (TiPCS, Tyranno Coat, TYR‐VN100 type, Okitsumo Co., Ltd.) were used as pre‐ceramic precursors for silicon carbide‐based membranes, respectively. SMP‐10 was pre‐heated at 150°C under a N 2 flow for 2 h, and diluted to 0.125 wt% by toluene prior to use in the fabrication of AHPCS‐derived membranes 28 . On the other hand, xylene was used to dilute the Tyranno Coat by 3 wt% before its use in fabricating the TiPCS‐derived membranes 29 …”