Characteristics of Ti–Nb,Ti–Zr and Ti–Al containing hydrogenated carbon nitride films

Nanocomposite Me–C–N:H coatings (Me is TiNb, TiZr or TiAl), with relatively high non-metal/metal ratios, were prepared by cathodic arc method using TiNb, TiZr and TiAl alloy cathodes in a CH₄ + N₂ atmosphere. For comparison purposes, a-C–N:H films were also produced through evaporating a graphite cathode in a similar atmosphere. The films were characterized in terms of elemental and phase compositions, chemical bonds, texture, hardness, adhesion and friction behavior by GDOES, XPS, Raman spectroscopy and XRD techniques, surface profilometry, hardness and scratch adhesion measurements, and tribological tests. The nanocomposite films consisted of a mixture of crystalline metal carbonitride and amorphous carbon nitride. The non-metal/metal ratio in the films composition was found to range between 1.8 and 1.9. For the metal containing nanocomposites, grain size in the range 7–23 nm, depending on the metal nature, were determined. As compared with the a-C–N:H, the Me–C–N:H films exhibited a much higher hardness (up to about 39 GPa for Ti–Zr–C–N:H) and a better adhesion strength, while the coefficients of friction were somewhat higher (0.2–0.3 for Me–C–N:H and 0.1 for a-C–N:H).     

Up-scaling the production of modified a-C:H coatings in the framework of plasma polymerization processes

Hydrogenated amorphous carbon (a-C:H) films with silicon and oxygen additions, which exhibit mechanical, tribological and wetting properties adequate for protective coating performance, have been synthesized at room temperature in a small- (0.1 m³) and a large-scale (1 m³) coaters by low-pressure Plasma-Activated Chemical Vapour Deposition (PACVD). Hence, a-C:H:Si and a-C:H:Si:O coatings were produced in atmospheres of tetramethylsilane (TMS) and hexamethyldisiloxane (HMDSO), respectively, excited either by radiofrequency (RF – small scale) or by pulsed-DC power (large scale). Argon was employed as a carrier gas to stabilize the glow discharge. Several series of 2–5 μm thick coatings have been prepared at different mass deposition rates, R_m, by varying total gas flow, F, and input power, W. Arrhenius-type plots of R_m/F vs. (W/F)^?1 show linear behaviours for both plasma reactors, as expected for plasma polymerization processes at moderated energies. The calculation of apparent activation energy, E_a, in each series permitted us to define the regimes of energy-deficient and monomer-deficient PACVD processes as a function of the key parameter W/F. Moreover, surface properties of the modified a-C:H coatings, such as contact angle, abrasive wear rate and hardness, appear also correlated to this parameter. This work shows an efficient methodology to scale up PACVD processes from small, lab-scale plasma machines to industrial plants by the unique evaluation of macroscopic parameters of deposition.     

Effect of methane on magnetron sputtering graphite target deposited films and tribological properties of a-C:H:Ti/a-C:H friction pairs

In this study, we prepared a-C:H films with different nanostructures at different methane flow rates. The effect of the methane flow rate on the tribological properties of 440 steel/a-C:H friction pairs and a-C:H:Ti/a-C:H friction pairs in an atmospheric environment was studied by a reciprocating friction machine. The results show that there is no relationship between the tribological properties of 440 steel/a-C:H friction pair and methane flow rate. The tribological performance of the a-C:H:Ti/a-C:H friction pair was greatly improved. In particular, in the friction pair of a-C:H:Ti/a-C:H with a methane flow rate of 20 sccm, superlubricity is shown, and the wear rate is only 4.04 × 10⁻⁹ mm³/Nm. After tribological experiments, Raman spectroscopy, XPS, and other characterization methods were used to study the relationship between the nanostructure and tribological properties of a-C:H:Ti films and a-C:H prepared with different methane flow rates. This study is great significance to the application of a-C:H:Ti/a-C:H friction pair in mechanical parts under atmospheric environment.     

How can H content influence the tribological behaviour of W-containing DLC coatings

In this paper, the influence of the addition of W and H to pure DLC coatings on the structural, mechanical and tribological properties will be presented. The coatings were deposited by r.f. magnetron sputtering from a C target embedded with different numbers of W pellets. Working in non-reactive or reactive atmosphere allowed to deposit H-free or H-containing coatings, respectively, on steel and Si substrates. A Cr adhesion interlayer was interposed between the films and the substrate. Films with W content from 0 to 12 at.% and H incorporated up to a maximum value close to 40 at.% were deposited. All coatings had an amorphous structure, although vestiges of crystallinity could be detected in W-containing films. The addition of W led to a significant hardening of the DLC coating (from ～10 to 18 GPa); inversely, with H incorporation the hardness drop down to values even lower than that of pure DLC films. It was possible to establish a good correlation between the hardness and the residual stresses. In spite of decreasing friction and wear coefficients when alloying DLC with W, almost no difference was found among the W–DLC films whatever the W content was. A similar trend was achieved with the H addition. However, in this case a decrease in the friction coefficient was registered whereas the wear rate increased. The best performance concerning the friction was obtained for an H-containing coating (0.05) whereas, for the wear resistance, H-free W–DLC films were better performing (0.3 × 10^?16 m³ N^?1 m^?1).     

Hydrogen-bond transition from the vibration mode of ordinary water to the (H,Na)I hydration states: Molecular interactions and solution viscosity

With the aid of differential phonon spectrometrics (DPS) and surface stress detection, we show that HI and NaI solvation transforms different fractions of the HO stretching phonons from the mode of ordinary water centred at ∼3200 to the mode of hydration shell at ∼3500 cm⁻¹. Observations suggest that an addition of the H ↔ H anti-hydrogen-bond to the Zundel notion, [H(H₂O)₂]⁺, would be necessary as the HO bond due H₃O⁺ has a 4.0 eV energy, and the H ↔ H fragilization disrupts the solution network and the surface stress. The I⁻ and Na⁺ ions form each a charge centre that aligns, stretches, and polarize the O:HO bond, resulting in shortening the HO bond and its phonon blue shift in the hydration shell or at the solute-solvent interface. The solute capabilities of bond-number-fraction transition follow: f_H = 0, f_Na ∝ C, and f_I ∝ 1 − exp(−C/C₀) toward saturation, with C being the solute molar concentration and C₀ the decay constant. The f_H = 0 evidences the non-polarizability of the H⁺ because of the H ↔ H formation. The linear f_Na(C) suggests the invariance of the Na⁺ hydration shell size because of the fully-screened cationic potential by the H₂O dipoles in the hydration shell but the nonlinear f_I(C) fingerprints the I⁻ ↔ I⁻ interactions at higher concentrations. Concentration trend consistency between Jones–Dole’s viscosity and the f_NaI(C) coefficient may evidence the same polarization origin of the solution viscosity and surface stress.     

(Liquid + liquid) equilibria of ternary and quaternary systems containing n-hexane,toluene, m-xylene,propanol, sulfolane,and water at T = 303.15 K

(Liquid + liquid) equilibrium data for ternary and quaternary systems containing n-hexane (C₆H₁₄), toluene (C₇H₈), m-xylene (C₈H₁₀), propanol (C₃H₈O), sulfolane (C₄H₈SO₂), and water (H₂O) were measured at T = 303.15 K. Phase diagrams of {w₁C₄H₈SO₂ + w₂C₇H₈ + (1 − w₁ − w₂)C₆H₁₄}, {w₁C₄H₈SO₂ + w₂C₈H₁₀ + (1 − w₁ − w₂)C₆H₁₄}, {w₁C₄H₈SO₂ + w₂C₃H₈O + w₃C₇H₈ + (1 − w₁ − w₂ − w₃)C₆H₁₄} and also systems containing water: {w₁C₄H₈SO₂ + w₂H₂O + w₃C₇H₈ + (1 − w₁ − w₂ − w₃)C₆H₁₄} and {w₁C₄H₈SO₂ + w₂H₂O + w₃C₈H₁₀ + (1 − w₁ − w₂ − w₃)C₆H₁₄} (w = mass fraction) were obtained at T = 303.15 K. The (liquid + liquid) equilibrium data of the systems were used to obtain interaction parameters in non-random two-liquid (NRTL) and universal quasi-chemical theory (UNIQUAC) activity coefficient models. These parameters can be used to predict equilibrium data of ternary and quaternary systems. The root mean square deviations (RMSDs) using these models were calculated and reported. The partition coefficients and the selectivity factors of solvents for extraction of toluene or m-xylene from n-hexane at T = 303.15 K are calculated and presented. The experimental selectivity factors of sulfolane for the system {w₁C₄H₈SO₂ + w₂C₇H₈ + (1 − w₁ − w₂)C₆H₁₄} at T = 298.15 K and T = 323.15 K were taken from the literature and the influence of temperature on the extraction of toluene was also investigated. The phase diagrams for the ternary and quaternary systems including both the experimental and correlated tie lines are presented. The tie-line data of the studied systems were also correlated using the Hand equation and the correlation parameters are calculated and reported.     

Spatial determination of diffusible hydrogen concentrations proximate to pits in a Fe–Cr–Ni–Mo steel using the Scanning Kelvin Probe

The diffusible hydrogen concentration (C_H,diff) was mapped spatially, proximate to acidic corrosion pits formed in MgCl₂ droplets, on an ultra-high strength stainless steel using a Scanning Kelvin Probe (SKP). A secondary hardened martensitic stainless steel (Fe–11Ni–12Cr–1Mo–0.005C–0.02Mn wt%) was evaluated. Predetermined, uniform C_H,diff levels quantified by electrochemical extraction after homogeneous cathodic charging, were calibrated versus the SKP potential at 57% RH (0.16 kPa H₂O, 20.26 kPa O₂, 79.03 kPa N_2, and 0.55 kPa residual gas species) [1]. Calibration enabled estimation of C_H,diff near pitted surfaces. Cross-sections of corrosion damage sites after pitting were also examined to determine the distribution of the C_H,diff perpendicular to the exposure surface.     

The dimeric unit [La(H2O)4(m-PO3C6H4COOH)(m-PO2(OH)C6H4COOH)(m-PO(OH)2C6H4COOH)]2 as building block of layered hybrid material

A new hybrid organic–inorganic material with the structural formula unit [La(H₂O)₄(m-PO₃C₆H₄COOH)(m-PO₂(OH)C₆H₄COOH)(m-PO(OH)₂C₆H₄COOH)]₂ (or [La(H₂O)₄C₂₁H₁₈O₁₅P₃]₂) has been synthesized under hydrothermal condition from La(NO₃)₃·6H₂O and 3-phosphonobenzoic acid (m-PO(OH)₂–C₆H₄–COOH) which is a rigid organic precursor possessing two types of functional groups: phosphonic acid and carboxylic acid. The two units of the produced hybrid are linked together by hydrogen bonds leading to a layered framework composing of by a repetition of inorganic and organic slices. The organic layers consist of dimeric units made of two meta-phosphono-benzoic acid linked together by hydrogen bonds involving their COOH groups. Two kinds of dimeric units are observed: PO₃C₆H₄COOH?HOOCC₆H₄PO(OH)₂, present 2 times in the structure, and PO₂(OH)C6H4COOH?HOOCC₆H₄PO₂(OH). The material crystallises in a monoclinic cell (C2/c (15) space group) with the following parameters: a = 42.515(4) Å, b = 7.4378(6) Å, c = 20.307(2) Å, β = 118.031(6)°, V = 5668.2(9) Å³, Z = 4, density = 1.908 g/cm³.     

Synthesis of new substituted benzaldazine derivatives,hydrogen bonding-induced supramolecular structures and luminescent properties

Syntheses of three benzaldazine compounds 1–3 with the general formula Ar₁(CH = N–N = HC)Ar₂ (Ar₁ = Ar₂ = 2-OH-3,5-^tBu₂C₆H₂ (1), Ar₁ = Ar₂ = 2-BrC₆H₄ (2), Ar₁ = ortho-C₆H₄(NHC₆H₃-Me₂-2,6), Ar₂ = C₆H₄F-2 (3)) are described. All compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, IR spectroscopy and single-crystal X-ray crystallography. The different supramolecular structures were obtained through different weak interactions (C ? H···O, O ? H···N and π···π interactions for 1; C ? H···Br and Br···Br interactions for 2; C ? H···F and C ? H···N interactions for 3). Compound 1 shows solvent-dependent fluorescent properties with blue to green emission on the increasing of the solvent polarity. Compounds 2, 3 show blue photoluminescence in different solvents.     

Vesicle stability in aqueous mixtures of zwitterionic/anionic surfactants

It was studied that the influences of the aging, temperature, addition of the polymer and cosolvent on the stability of the vesicles spontaneously formed in the mixtures of zwitterionic surfactant (dodecyl carboxyl betaine, C₁₂BE) and double-tailed anionic surfactant (sodium bis(2-ethylhexyl) sulfosuccinate, AOT) under the inducement of salt by means of freeze-fracture and negative-staining transmission electron microscopy (TEM), dynamic light scattering (DLS) and turbidity measurements. It is found that the vesicles can exist over a long period of aging (about 300 days) at room temperature, show good stability after a heating–cooling cycle of 90–25 °C and a freeze–thaw cycle of −10 to 25 °C, respectively, and may be transformed from spherical vesicles to tubelike structures induced by high temperature 90 °C. Under the effect of (PEO)₁₃(PPO)₃₀(PEO)₁₃ (L64), the transition from unilameller vesicles to large multivesicular vesicles. The presence of ethanol may decrease the stability of vesicles, resulting in the fusion among vesicles to form large vesicles. The excessive amount of ethanol may destroy the vesicles, and the order of ability of destroying vesicles was obtained to be C₅H₁₁OH > C₄H₉OH > C₃H₇OH > C₂H₅OH > CH₃OH.     

Zirconia-based amperometric sensor using ZnO sensing-electrode for selective detection of propene

The sensing characteristics to propene (C₃H₆) were examined at 600 °C under wet condition for the amperometric sensor using a yttria-stabilized zirconia (YSZ) tube and ZnO (+8.5 wt%Pt) sensing-electrode (SE). In order to improve the sensitivity to C₃H₆, the “pulsed-potential method” was adopted here. It was found that the current response varied almost linearly with C₃H₆ concentration in the range of 0–200 ppm when SE was polarized at +1.0 V (vs. Pt/air reference electrode) for a period of 0.3 s. By using the present “pulsed-potential method”, the sensitivity to 100 ppm C₃H₆ was increased about 1000 times, compared with the normal “constant-potential method”. The excellent selectivity to C₃H₆ was also obtained for the present sensor without influence of other hydrocarbons, NO_x, CO, H₂, etc.     

Synthesis and characterization of novel intramolecularly O,C,O-coordinated heteroleptic organostannylenes and their tungstenpentacarbonyl complexes

The syntheses are reported of the novel heteroleptic organostannylenes [2,6-(ROCH₂)₂C₆H₃]SnCl (1, R = Me; 2, R = t-Bu) and of their tungstenpentacarbonyl complexes [2,6-(ROCH₂)₂C₆H₃](X)SnW(CO)₅ (3, X = Cl, R = Me; 4, X = Cl, R = t-Bu; 5, X = H, R = Me). The compounds were characterized by means of elemental analyses, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopies, electrospray mass spectrometry and in case of 3 and 4 also by single crystal X-ray diffraction analysis. For the two latter compounds the substituents bound at the ether oxygen atom control the strength of intramolecular O → Sn coordination. Thus, the O–Sn distances amount to 2.391(5)/2.389(5) (3) and 2.464(3)/2.513(3) Å (4).     

Piperazinium dihydrogen phosphate,C4H12N2(H2PO4)2: Synthesis, 31P CP/MAS NMR,structural and thermal investigations

A new piperazinium dihydrogen orthophosphate, C₄H₁₂N₂(H₂PO₄)₂ was discovered and characterized by combining information from X-ray diffraction, ³¹P CP/MAS NMR and thermal analysis (TG/DTA). The compound C₄H₁₂N₂(HPO₄)·H₂O, was also studied in order to compare these two similar materials. The hydrothermal stability is investigated for the system: 1.0 C₄H₁₀N₂: n H₃PO₄: 55–60 H₂O, 0.5 < n < 3. The reaction mixtures with pH in the range 1.6–8.4 were placed at a fixed temperature in the range 20–180 °C for ca. 5 days. C₄H₁₂N₂(H₂PO₄)₂ was obtained when n > ca. 2. A crystal of piperazinium dihydrogen phosphate, C₄H₁₂N₂(H₂PO₄)₂ was structurally investigated using X-ray diffraction: triclinic, space group $P\overline{1}$, a = 7.023(2), b = 7.750(3), c = 12.203(4) Å, α = 84.668(7), β = 81.532(7) and γ = 63.174(6)°, V = 586.0(4) Å³ and Z = 2. The reactivity of C₄H₁₂N₂(H₂PO₄)₂ was investigated by systematic solvothermal syntheses.     

Versatile Ru-based metathesis catalysts designed for both homogeneous and heterogeneous processes

The synthesis of new ruthenium-based catalysts applicable for both homogeneous and heterogeneous metathesis is described. Starting from the Hoveyda-Grubbs first generation (1) and the Hoveyda-Grubbs second generation (2) catalysts the homogeneous catalysts [RuCl((RO)₃Si–C₃H₆–N(R′)–CO–C₃F₆–COO)(CH–o-O–iPr–C₆H₄)(SIMes)] (4: R = Et, R′ = H; 5: R = R′ = Me) (SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) were prepared by substitution of one chloride ligand with trialkoxysilyl functionalized silver carboxylates (RO)₃Si–C₃H₆–N(R′)–CO–C₃F₆–COOAg (3a: R = Et, R′ = H; 3b: R = R′ = Me). These homogeneous ruthenium-species are among a few known examples with mixed anionic ligands. Exchange of both chloride ligands afforded the catalysts [Ru((RO)₃Si–C₃H₆–N(R′)–CO–C₃F₆–COO)(CH–o-O–iPr–C₆H₄)(SIMes)] (9: R = Et, R′ = H; 11: R = R′ = Me) and [Ru((RO)₃Si–C₃H₆–N(R′)–CO–C₃F₆–COO)(CH–o-O–iPr–C₆H₄)(PCy₃)] (8: R = Et, R′ = H; 10: R = R′ = Me). The reactivity of the new complexes was tested in homogeneous ring-closing metathesis (RCM) of N,N-diallyl-p-toluenesulfonamide and TONs of up to 5000 were achieved. Heterogeneous catalysts were obtained by reaction of 4, 5 and 8–11 with silica gel (SG-60). The resultant supported catalysts 4a, 5a, 8a–11a showed reduced activity compared to their homogenous analogues, but rival the activity of similar heterogeneous systems.     

Optimization of the chemoenzymatic mono-epoxidation of linoleic acid using D-optimal design

Mono-epoxied linoleic acid 9(12)-10(13)-monoepoxy 12(9)-octadecanoic acid (MEOA) was synthesized and optimized by immobilized Candida antarctica lipase (Novozym 435®) using D-optimal design. For optimizing the reaction, response surface methodology (RSM) was employed with four reaction variables such as the effect of amount of hydrogen peroxide (μL), amount of enzyme (w) and reaction time (h). At optimum conditions the experiment to obtain a higher yield% with a medium OOC% of MEOA was predicted at an amount of H₂O₂ μL of 15, Novozym 435® of 0.12 g and 7 h of reaction time. At this condition, the yield of MEOA was 82.14%, 4.91% of OOC and 66.65 mg/g of iodine value (IV). The observed value was reasonably close to the predicted value. Hydrogen peroxide was found to have the most significant effect on the degree of epoxidation OOC% and yield%. The epoxy ring opening (–C–O–C–) has been observed by Fourier Transform Infrared Spectroscopy (FTIR) at 820 cm⁻¹ and the double band (–CC–) at 3009 cm⁻¹. ¹H NMR analyses confirmed that the oxirane ring (–CH–O–CH–) of MEOA at 2.92–3.12 ppm and four signals of methane (–CHCH–) was at 5.38–5.49 ppm while the ¹³C NMR showed the oxirane ring (–C–O–C–) at 54.59–57.29 ppm and the olefinic carbons at 124.02–132.89 ppm.     

Synthesis,structure and thermochemical study of a cobalt energetic coordination compound incorporating 3,5-diamino-1,2,4-triazole and pyridine-2,6-dicarboxylic acid

An energetic coordination compound [Co₂(C₂H₅N₅)₂(C₇H₃NO₄)₂(H₂O)₂]·2H₂O (Hdatrz(C₂H₅N₅) = 3,5-diamino-1,2,4-triazole, H₂pda(C₇H₅NO₄) = pyridine-2,6-dicarboxylic acid) has been synthesized and characterized by elemental analysis, chemical analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analysis confirmed that the compound possessed a di-nuclear unit and featured a 3D super-molecular structure. Furthermore, a reasonable thermochemical cycle was designed based on the preparation reaction of the compound and the standard molar enthalpy of dissolution of reactants and products was measured by the RD496-2000 calorimeter. Finally, the standard molar enthalpy of formation of the compound was determined to be −(2475.0 ± 3.1) kJ · mol⁻¹ in accordance with Hess’s law. In addition, the specific heat capacity of the compound at T = 298.15 K was determined to be (1.13 ± 0.02) J · K⁻¹ · g⁻¹ by RD496-2000 calorimeter.     

Density functional theory investigation of the photodissociation channels of acetophenone

The photodissociations of acetophenone (C₆H₅COCH₃) have been investigated by density functional theory (DFT) approach. The experimentally observed three photodissociation channels were clarified from the theoretical calculations on the related reactants, transition states (TSs), and products. Two of the three channels, C₆H₅COCH₃ → C₆H₅CO + CH₃ and C₆H₅COCH₃ → C₆H₅ + CH₃CO, were assigned to Norrish I reactions on the potential energy surfaces (PESs) of the lowest triplet state (T₁). And, the first one is more favorable for lower barrier. The subsequent decompositions, C₆H₅CO → C₆H₅ + CO and CH₃CO → CH₃ + CO, were also studied by the similar calculations as above. The third photodissociation channel, C₆H₅COCH₃ → C₆H₅CH₃ + CO, has been documented on the PESs of the ground state (S₀). The third one played a minor role in the photodissociations of C₆H₅COCH₃ for much higher barrier than the first two.     

(Liquid + liquid) equilibrium of (imidazolium ionic liquids + organic salts) aqueous two-phase systems at T = 298.15 K and the influence of salts and ionic liquids on the phase separation

(Liquid + liquid) equilibrium for the {1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim]BF₄)/1-propyl-3-methylimidazolium tetrafluoroborate ([C₃mim]BF₄) + organic salt + H₂O} aqueous two-phase systems (ATPSs) have been experimentally ascertained at T = 298.15 K. Three empirical equations were used to correlate the binodal data. On the basis of the empirical equation of the binodal curve with the highest accuracy and lever rule, the (liquid + liquid) equilibrium data were calculated by MATLAB. The reliability of the tie line compositions was proved by the empirical correlation equations given by the Othmer–Tobias and Bancroft equations. The effective excluded volume (EEV) values obtained from the binodal model for these systems were determined. The EEV and the binodal curves plotted in molality both indicate that the salting-out abilities of the four salts follow the order: Na₃C₆H₅O₇ > (NH₄)₃C₆H₅O₇ > Na₂C₄H₄O₄ ≈ Na₂C₄H₄O₆, while the phase-separation abilities of the investigated ILs are in the order of [C₃mim]BF₄ > [C₂mim]BF₄. In the systems investigated, the effect of salts on the phase-forming capability was also evaluated in the shape of the salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation. The phase-forming ability increases with the increase of salting-out coefficient.     

Fused ring systems derived from reactions of half-open titanocenes with diynes: Syntheses,characterization, cage rearrangements,and structural studies

The reactions of several α,ω-diynes with half-open titanocene complexes [M(C₅H₅)(2,4-C₇H₁₁)(PR₃)] (C₇H₁₁ = dimethylpentadienyl) lead to 5 + 2 + 2 ring constructions, yielding nine-membered rings fused to four-membered and larger rings. These reactions tolerate significant functionalization, even allowing for the presence of heteroatoms such as oxygen and nitrogen. The nine-membered rings provide both allyl and diene coordination to the Ti(C₅H₅) fragments, resulting in 16 electron configurations. On standing, these species undergo cage rearrangements, via CC bond activation reactions. Structural data have been obtained for a number of the fused ring species, as well as one of the rearrangement products.     

Thermal behaviour of malonic acid,sodium malonate and its compounds with some bivalent transition metal ions

Characterization, thermal stability and thermal decomposition of transition metal malonates, MCH₂C₂O₄·nH₂O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as, the thermal behaviour of malonic acid (C₃H₄O₄) and its sodium salt (Na₂CH₂C₂O₄·H₂O) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration, as well as, the thermal decomposition of the anhydrous compounds occurs in a single step. For the sodium malonate the final residue up to 700 °C is sodium carbonate, while the transition metal malonates the final residue up to 335 °C (Mn), 400 °C (Fe), 340 °C (Co), 350 °C (Ni), 520 °C (Cu) and 450 °C (Zn) is Mn₃O₄, Fe₂O₃, Co₃O₄, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds.