Search Results

You are looking at 1 - 10 of 140 items for :

  • Refine by Access: All Content x
Clear All

Abstract  

Identification and monitoring of gaseous species released during thermal decomposition of pure thiourea, (NH2)2C=S in argon, helium and air atmosphere have been carried out by both online coupled TG-FTIR and simultaneous TG/DTA-MS apparatuses manufactured by TA Instruments (USA). In both inert atmospheres and air between 182 and 240°C the main gaseous products of thiourea are ammonia (NH3) and carbon disulfide (CS2), whilst in flowing air sulphur dioxide (SO2) and carbonyl sulphide (COS) as gas phase oxidation products of CS2, and in addition hydrogen cyanide (HCN) also occur, which are detected by both FTIR spectroscopic and mass spectrometric EGA methods. Some evolution of isothiocyanic acid (HNCS) and cyanamide (NH2CN) vapours have also observed mainly by EGA-FTIR, and largely depending on the experimental conditions. HNCS is hardly identified by mass spectrometry. Any evolution of H2S has not been detected at any stage of thiourea degradation by either of the two methods. The exothermic heat effect of gas phase oxidation process of CS2 partially compensates the endothermicity of the corresponding degradation step producing CS2.

Restricted access

Abstract  

Identification and monitoring of gaseous species released during thermal decomposition of the title compound 1, Zn(tu)2Cl2, (tu=thiourea, (NH2)2C=S) have been carried out in flowing air atmosphere up to 800°C by both online coupled TG-EGA-FTIR and simultaneous TG/DTA-EGA-MS. The first gaseous products of 1, between 200 and 240°C, are carbon disulfide (CS2) and ammonia (NH3). At 240°C, an exothermic oxidation of CS2 vapors occurs resulting in a sudden release of sulphur dioxide (SO2) and carbonyl sulphide (COS). An intense evolution of hydrogen cyanide (HCN) and beginning of the evolution of cyanamide (H2NCN) and isothiocyanic acid (HNCS) are also observed just above 240°C. Probably because of condensation and/or polymerization of cyanamide vapors on the windows and mirrors of the FTIR gas cell optics, some strange baseline shape changes are also occurring above 330°C. Above 500°C the oxidation process of organic residues appears to accelerate which is indicated by the increasing concentration of CO2, while above 600°C zinc sulfide starts to oxidize resulting in the evolution of SO2. All species identified by FTIR gas cell were also confirmed by mass spectrometry, except for HNCS.

Restricted access

Introduction Chromium tris thiourea sulphate (TTCS) is a metal organic nonlinear optical crystal which can be grown fairly and easily in large sizes from aqueous solution. Its growth and characterization have been reported in a

Restricted access

nitrate and bismuth acetate of thiourea crystal complexes were reported with formula Bi 2 (CH 3 COO) 6 · 3SC(NH 2 ) 2 · H 2 O, Bi(CH 3 COO) 3 · 3SC(NH 2 ) 2 , [Bi(NO 3 ){SC(NH 2 ) 2 } 5 ](NO 3 ) 2 · H 2 O and [Bi(NO 3 ) 3 {SC(NH 2 ) 2 } 3 ] [ 9 , 10

Restricted access

Introduction In recent years, the non-linear optical (NLO) properties of some products of thiourea [ 1 – 15 ] have attracted great interest because semiorganic materials have the potential for combining high optical non

Restricted access

, the fact is that inorganic materials have lower probability for centric structures and consequently researchers focused their attention on organic materials. Thiourea is an interesting inorganic matrix modifier because of its large dipole moment [ 5

Restricted access

]. Recently metal complexes of thiourea have been explored. Thiourea is an interesting inorganic modifier due to its large dipole moment and its ability to form an extensive network of hydrogen bonds. It belongs to orthorhombic crystal system. Only few of

Restricted access

their attention on semi organic crystals. Recently thiourea–urea complexes have been explored. Some of the complexes are urea–thiourea [ 9 ], Bis thiourea–urea [ 10 ], thiourea urea zinc chloride [ 11 ], urea thiourea magnesium sulphide [ 8 ], urea

Restricted access

Abstract  

The isotopic exchange rate of thiourea in hexa(thiourea) plumbous nitrate was determined at two different concentrations. The results showed that the complex is unstable in the kinetic sense. The rate of exchange increases with increase of concentration of the free ligand and also of the complex. Furthermore, the results indicated that an increase in temperature by 15°C does not influence the rate to any significant degree.

Restricted access

-prolinium picrate [ 9 ] have been reported. Crystal structure analysis of l -proline thiourea monohydrate (LPTU) grown by slow evaporation technique at room temperature is reported in this article. Second harmonic generation (SHG) test and the thermal

Restricted access