Papers by Keyword: Intermediate

Abstract: CVD SiC material with many excellent physical and chemical properties was used widely in the field of aerospace as reflector materials. In addition, CVD SiC thin film materials because of its compact structure, high purity can also be used as precision optical components of semiconductor industry. But the CVD process is a complex chemical process and the reaction process is very time consuming. Research of chemical vapor deposition for preparing silicon carbide process mechanism is important significance for the expansion of the application of silicon carbide. In this paper, CVD SiC coatings were fabricated by the pyrolysis of methyltrichlorosilane (MTS) in hydrogen at a low pressure. XRD and EDS were used to characterize the component of intermediate. SEM was used to observe the surface morphology and microstructure of coatings. The results indicated that key problem to be solved is to control the growth rate of SiC for high quality deposition coating, while the growth rate is also affected by process parameters. To obtain the materials to meet the use requirements, the need for control of each parameter in the reaction process.

Abstract: A concise route to total synthesis of (+)-(6S, 2'R)-cryptocaryalactone (1) was designed and the key intermediate (3) was synthesized via an Evans Aldol reaction to construct the chiral hydroxyl group.

Abstract: A concise route to total synthesis of (+) - (6S, 2'R)-cryptocaryalactone (1) was designed and the key intermediate (7) was synthesized. The route included an Evans Aldol reaction, TBS protection and DIBAL-H reduction.

Abstract: The key intermediate of strictifolione was synthesized via an Evans aldol reaction to construct its chiral hydroxyl.

Abstract: The copper extraction yield from chemical leaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as on the different genetic type of the chalcopyrite used. The chemical leaching characteristics of chalcopyrite from marine volcanic type and porphyry type were studied. It was found that the intermediates of marine volcanic chalcopyrite and porphyry chalcopyrite elucidated from the MLA were elemental sulphur and non-stoichiometric minerals, such as Cu_3.5Fe₄S_2.5, Cu₅Fe₄S and Cu_3.5Fe_1.5S₅. The results suggested that the main difference between marine volcanic chalcopyrite and porphyry chalcopyrite is the rates of copper and iron ions dissolution from chalcopyrite crystal lattice.

Abstract: An novel intermediate of (4-Iodo-phenyl)-(4-trifluoromethyl-phenyl)-diazene for azobenzene liquid crystal was synthesized. 4-Trifluoromethyl-phenylamine as raw material was oxidized by Oxone (Potassium peroxymonosulfate) in CH₂Cl₂/H₂O solvent to synthesize 1-Nitro-4-trifluoromethyl-benzene (m1). The effect of Oxone amount on the conversion degree of raw material was discussed in ditail. Then m1 was coupled with 4-Iodo-phenylamine to obtain the important intermediate, yellow solid, the yield was 52%. The chemical structures of synthetic intermediate was confirmed by FT-IR and 1H-NMR.

Abstract: Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.

Abstract: Based on fusion bonding of liquid TiC-TiB₂ ceramic film to stainless steel substrate of 1Cr18Ni9Ti, the ceramic coating on stainless steel substrate was achieved in graded composition by combusion synthesis in high-gravity field. XRD, FESEM and EDS results showed the ceramic coating was composed of a number of fine TiB₂ platelets, irregular TiC grains and a few of Cr metallic binder and the inclusions of Al₂O₃ partilces, and physical and mechanical properties showed density, relative density, microhardness and fracture toughness of the ceramic coating were 4.25 g • cm-3, 98.2%, 24.6 GPa and 14.5 ± 3.5 MPa • m^0.5, respectively. The joint of TiC-TiB₂ ceramic coating on stainless steel substrate consisted of 3-layer structures, i.e. the ceramic coating, the intermediate and stainless steel substrate, and within the intermediate of Fe-Cr-Ni-Ti metallic matrix Ti-Fe enriched carbides decreased gradually both in volume fraction and particle size from the ceramic coating to stainless steel substrate in the presence of atomic unidirectional diffusion of Ti and C, while some isolated α-Al₂O₃ fine particles were also observed in the intermediate besides the presence of both some coarsened α-Al₂O₃ inclusions nearby the ceramic coating and the barrier layers of Al₂O₃ between the ceramic and the intermediate, so it is considered that the ceramic coating on stainless steel substrate is achieved partially by fusion bonding due to the poor incompatibilities between Al₂O₃ inclusions and the intermediate, resulting in the moderate shear strength of 125 ± 35 MPa between the ceramic coating and stainless steel substrate.

Abstract: 1,1-Bis(hydroxymethyl)cyclopropane was synthesized by reaction dibromoneopentyl glycol with zinc powder at mole ratio of nDG:nzinc=1:1.05 and 80oC (slightly reflux) for 7 hours. Under optimal conditions, yield and purity of the title compound were 87.3% and 98.67%, respectively. Dibromoneopentyl glycol was also prepared in 91.7% yield with pentaerythritol and hydrobromic acid as material and diethyl sulfate as catalyst under reflux for 10 hours. Structural characterization of 1,1-bis(hydroxymethyl)cyclopropane was conducted by IR and H-NMR.

Abstract: Ammonium polyphosphate (APP) is a long chain polyphosphate salt, it has six crystalline forms. In preparation of APP, temperature is significant to controllably obtain a certain crystalline forms. In this paper, the effect of temperature is investigated during the preparation process of APP. Some intermediates are detected, the XRD spectra of these intermediates are discussed. The results show that temperature at 2800C is suitable for preparation of form II. With temperature increasing, water insolubility increases. The results are informative for controllable preparation of APP in industrial production.