Kapton seal

H2S in H2 at 675 K, the cells were sealed off prior to the measurements. EXAFS studies of the model compounds and the passivated catalysts were carried out by placing appropriate amounts of the sample in thin aluminum frames equipped with Kapton windows. 

In another report, instead of direct x-ray ablation, an x-ray mask, which was 10-pm-thick Au on a Kapton film, was employed to ablate a PMMA wafer. Then the ablated PMMA wafer was developed. For sealing, a PMMA cover was first spin-coated with a 2-pm layer of poly(butyl methacrylate-co-methyl methacrylate) and then thermally bonded to the PMMA plate (120°C for 1 h) [200]. 

Zhang et al. (1991) published a relatively simple transmission XAFS cell in 1991. Their design incorporated a cylindrical body with sealed Kapton windows at each end through which the reaction gas flowed. A heating coil was wrapped around the cylinder, and a liquid nitrogen vessel provided cooling of the sample. The sample was mounted on an insert and sealed on the holder with Kapton tape. This insert was placed inside the cylindrical cavity. It is not clear from the description provided how the gas in the cylindrical cavity made contact with the catalyst in the sample holder. 

I, inset M, main body with Kapton windows (W) and seals (R) and outlet for vacuum pump (V) PI and P2, plates for assembly of cell SI and S2, seals for cell T1 and T2, thermocouples. A Teflon O-ring (TR) may be optionally used. Reprinted with permission from (Hannemann et al., 2007). Copyright 2007 Wiley-Blackwell. 

What are the maximum and minimum operating temperatures and pressures A cell that is to be operated at atmospheric pressure at 473 K can be far simpler in design than one operated at 50 bar and 1000 K. These parameters place constraints on the window materials (e.g., Kapton vs. beryllium), the sealing mechanism of the cell (e.g., can O-rings be tolerated, will water cooling of the seals be necessary ), and the thicknesses of the reactor walls and windows. 

Starting materials and solvents were purchased from Aldrich Chemical Co. acetonitrile (ACN), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) were obtained anhydrous in Sure/Seal bottles and used as received. The polyamic acid of PMDA-ODA (2545 Pyralin) was supplied by DuPont. The soluble polyimide XU-218, derived from 3,3, 4,4 -benzophenone tetracarboxylic dianhydride (BTDA) and diamino-1,1,3-trimethyl-3-phenylindan isomers (DAPI) was purchased from Ciba-Geigy Corp. The acetylene terminated imide oligomer powder (Thermid MC-600) derived from BTDA, aminophenylacetylene, and 1,3-bis (2-aminophenoxy) benzene (APB) was obtained from National Starch and Chemical Company. Kapton Type II (PMDA-ODA) films were obtained from DuPont Co., Apical polyimide films were obtained from Allied Corp., and Upilex Type-S and Type-R polyimide films derived from 3,3, 4,4 -biphenyl tetracarboxylic dianhydride (BPDA) plus p-phenylenediamine (PDA) and ODA, respectively were obtained from ICI Americas Inc. 

The positron source, 120 kBq of Na, was deposited onto a Kapton foil covered with identical foil and sealed. The foil 8 pm thick absorbed 10% of positrons in polyimides Ps does not form and annihilation in the source envelope gave one component only = 374 ps, which must be taken into account. The source was sandwiched between two samples of the material studied and placed into a container in a vacuum chamber. The source-sample sandwich was viewed by two Pilot U scintillators coupled to XP2020Q photomultipliers. The resolution of our spectrometer with a stop window broadened to 80% (in order to register the greatest number of three-quantum decays) was 300 ps FWHM. The finite resolution had no influence on the results of our experiment as FWHM was still comparable to the channel definition At = 260 ps.The positron lifetime spectra were stored in 8000 channels of the Tennelec Multiport E analyser. 

Sorption samples were prepared for XAS using the same procedures described above for generating the pH edges and isotherm data. All samples were equilibrated for a minimum of 24 h prior to pH measurement and centrifugation. An aliquot of supernatant was then removed and stored in acid prior to subsequent analysis for metal ion content. Most of the remaining supernatant solution was then removed and the remaining wet pastes were placed into aluminum sample holders, sealed with mylar or Kapton tape windows for XAS analysis. 

Kapton . [DuPont] Polyimide film, unreinforced or Teflon, carbon-filled heat seal ai lics. low dielec, film for military applies. 

Kapton . [DuPont] Polyimidefilm,un-reinfcnced or Tefltm, cvbon-filled heat seal applies. low d ec. film fm military applies. 

Samples for SAXS were prepared in sealed vials as reported elsewhere (2). Two Kapton (polyimide) films (7.5 pm thick) were buffed in the y-direction with an ethanol-wetted tissue paper. About 100 mg of sample were molten at 55°C to a liquid crystal and transferred to a tense, fixed Kapton film. Before cooling to below 35 °C, another Kapton film was put over the sample and both tense films were gently rubbed against each other at -0.5 mm/s in the y-direction for -10 s. Within three minutes the sandwiched sample was mounted in a hot copper block with a hole for the beam, and annealed at 58 1 °C for 30 min prior to the start of a 22-h exposure, during which annealing was continued. 

Fi re 1. Rietveld refinement of the diffraction pattern of SrNCN Eir. The rather unusual background in the 10—35° range is an artifact going back to the setup of the evacuated flatsample holder because its windows had to be sealed with a Kapton foil. 

Usually, the positron source NaCl is sealed between very thin metal (Ni, Ti) or polymer (kapton, Mylar) foils. The thickness (i.e., surface density) of these foils is around 1-2 mg/cm, but several percents of positrons annihilate in this wrapping even in the case of the thinnest foil. During spectrum evaluation, positrons annihilated in the source foil should be taken into account. 

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