Thermal behavior of the Cu-10 mass%Al AND Cu-10 mass%Al-4 mass%Ag alloys

The thermal behavior of the Cu-10 mass%Al and Cu-10 mass%Al-4 mass%Ag alloys was studied using classical differential thermal analysis (DTA), optical microscopy (OM) and X-ray diffractometry (XRD). The DTA curves were obtained for annealed and quenched samples. The results indicated that the presence of silver introduces new thermal events, associated to the formation of a silver-rich phase, to the shift of the equilibrium concentration to higher Al contents and to the decomposition of the silver-rich phase in the same temperature range of the b₁ phase decomposition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of Ag addition on the thermal behavior of the Cu-11 mass% Al alloy

In this work the influence of Ag additions on the thermal behavior of the Cu-11 mass% Al alloy was studied using differential scanning calorimetry, in situ X-ray diffractometry and scanning electron microscopy. The results indicated that changes in the heating rate shift the peak attributed to α phase formation to higher temperatures, evidencing the diffusive character of this reaction. The activation energy value for the α phase formation reaction, obtained from a non-isotherm kinetic model, is close to that corresponding to Cu atoms self diffusion, thus confirming that this reaction is dominated by Cu atoms diffusion through the martensite matrix.     

Effect of Ag concentration on the thermal behavior of the Cu-10 mass% Al and Cu-11 mass% Al alloys

In this work the effect of Ag concentration on the thermal behavior of the Cu-10 mass% Al and Cu-11 mass% Al alloys with additions of 4, 6, 8 and 10 mass% Ag was studied using differential scanning calorimetry (DSC), in situ X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that for the Cu-10 mass% Al alloy Ag addition induce the β′₁ phase formation and for the Cu-11 mass% Al alloy these additions increase the amount of martensite formed on quenching and decrease the stability range of this phase on heating.     

DSC study of glycerol-extracted muscle fibers in intermediate states of ATP hydrolysis

Summary The heat capacity of contractile proteins actin and myosin was studied in psoas muscle of rabbit in strongly and weakly binding state of myosin to actin as a function of temperature by DSC. Deconvolution of the unfolding scans makes possible to characterize the structural domains of the macromolecules. We tried to approach the unfolding process in different intermediate state of ATP hydrolysis. The thermal transitions were calorimetrically irreversible, therefore the two-state irreversible model that describes fairly well the denaturation of different proteins was used for evaluation of the denaturation processes in muscle fibers in strongly (rigor, ADP) and weakly binding states (ATP·V_i, ADP·AlF₄) of myosin to actin. Deconvolution resulted in four transitions, the first three transition temperatures were almost independent of the intermediate states of muscle, the last transition temperature was shifted to higher temperature, when the buffer solution was manipulated. The mean values in strongly binding states were T_m1=52.9±0.7°C, T_m2=57.9±0.7°C, T_m3=63.7±1.0°C and T_m4=67.8±0.7°C, but the last transition increased to higher temperature depending on the P_i analogue.     

Ag-rich phase precipitation in the Cu-9 mass% Al alloy with Ag additions

The Ag-rich phase precipitation in the Cu-9 mass% Al was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicated that Ag additions did not interfere on the metastable transitions sequence of the Cu-mass% Al alloy but Ag precipitation disturbs the β phase formation reaction and the martensitic phase decomposition reaction.     

Effect of Ag additions on the reverse martensitic transformation in the Cu-10 mass% al alloy

The effect of Ag additions on the reverse martensitic transformation in the Cu-10 mass% Al alloy was studied using differential thermal analysis (DTA), optical (OM) and scanning electron microscopies (SEM) and X-ray diffractometry. The results indicated that Ag additions to the Cu-10 mass% Al alloy shift the equilibrium concentration to higher Al contents, allow to obtain both β'₁ and β' martensitic phases in equilibrium and that Ag precipitation is a process associated with the perlitic phase formation.     

Thermal behavior of α-(Cu–Al–Ag) alloys

Thermal behavior of α-(Cu–Al–Ag) alloys, i.e. alloys with composition less than about 8.5 mass% Al, was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). The results indicated that the presence of silver introduces new thermal events ascribed to the formation of a silver-rich phase and, after addition higher amounts than 8 mass% Ag to the Cu–8 mass% Al alloy it is possible to observe the formation of the γ₁ phase (Al₄Cu₉), which is only observed in alloys containing minimum of 9 mass% Al. These results may be attributed to some Ag characteristics and its interaction with Cu and Al.     

Influence of Silver Additions on the Thermal Behavior of the Cu–8 Mass% Al Alloy

The influence of additions of 2, 4, 6, 8, 10 and 12 mass% Ag on the thermal behavior of the Cu–8 mass% Al alloy was studied using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). The results indicate that the presence of silver introduces new thermal events, due to the formation of a silver-rich phase and, for additions of 10 and 12 mass% Ag, it is possible to verify the formation of the γ₁ phase (Cu₉Al₄) and the metastable transitions which are only observed in alloys with a minimum of 9 mass% Al. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal analysis of Al-Cu-Mg-Si alloy with Ag/Zr additions

Heat-treatable aluminium alloys are widely used for structural applications. Their strength is obtained through age hardening phenomena, that are sensitive to microalloying. In the present paper the results of thermal analyses on the ageing behaviour of an Al-Cu-Mg-Si alloy with silver and zirconium additions are presented. Specimens were water quenched after solution heat treatment, then aged at 453 K and a hardness-versus-time plot was drawn. Samples representative of different ageing conditions were subjected to DSC scans. Peaks were identified taking into account θ and Q phases precipitation sequences. Solution treated samples showed GP/θ″/θ′/Q sequence, while in peak aged condition GP and θ″ precipitation peaks disappeared and a reduction of θ′ peak area was observed, witnessing the concurrent presence of θ″ and θ′ phases at peak hardness condition. Experimental data were compared with results from analogous investigations performed on a conventional commercial Al-Cu-Mg-Si alloy.     

The use of DSC in describing the structure evolution of an AlZnMg alloy

Summary The potential of DSC in suggesting modifications of thermal treatments of Al alloys to increase mechanical properties is described. Significant results can be obtained from calorimetric evolution after a series of annealings, even without a direct observation of the microstructure. The role of a reference baseline is discussed. The Guinier-Preston (GP) zones formation, dissolution or transformation is followed, and their relevance for the microhardness increase is shown, for an AlZnMg alloy of technical interest. Multi-stage thermal treatments have been confirmed to be beneficial. A secondary precipitation occurs at room temperature after annealing at temperatures at which primary precipitation is almost complete.     

Effect of chemical demineralization on thermal behavior of bituminous coals

Growing environmental concerns and the need for alternatives for oil and natural gas resulted in intensive researches on ultra clean coal (UCC). Therefore, the researches related to practice and application of various methods to produce UCC become more important. Thermal characterization of chemically demineralized coals by thermogravimetric analysis method is presented in this study. The aim of the study is to provide thermal data for HF–HNO₃ leaching system used for the production of UCC. Coal samples were first physically enriched by density separation. Then the enriched portion was chemically demineralized by using HF and HNO3, respectively. Ash content of coal samples were reduced to a range of 0.12–0.41% by chemical demineralization process. The petrographic, ultimate and proximate analyses were carried out to determine main features of samples. Physically and chemically enriched coal samples were then analyzed in a TG by two different techniques separately. The first technique covered thermal characterization of samples under non-isothermal conditions. Characteristic temperatures for each sample were obtained from the TG and DTG data. The second technique involved the determination of reactivity of in situ produced chars of each sample.     

Al2O3负载Ag催化剂的杀菌作用

 考察了空气中Al2O3负载的Ag催化剂(Ag/Al2O3和AgCl/Al2O3)对大肠杆菌(E.coli)的杀灭作用. 结果表明,负载Ag的催化剂的杀菌效果明显好于Al2O3. 在空气中,催化剂上溶出的Ag+对细菌的重金属毒性可以忽略. Ag/Al2O3, AgCl/Al2O3和Al2O3在有氧和无氧条件下的杀菌效果表明, Ag促进了催化剂表面分子态氧向活性氧转化,活性氧通过氧化作用破坏E.coli 的细胞膜,从而提高了催化剂的杀菌能力. 扫描电镜结果证实在催化剂表面E.coli细胞的破坏是从细胞膜开始的.     

Heteroctanuclear Au4Ag4 Cluster Complexes of 4,5-Diethynylacridin-9-One with Luminescent Mechanochromism

Two heteroctanuclear Au₄Ag₄ cluster complexes of 4,5-diethynylacridin-9-one (H₂L) were prepared through the self-assembly reactions of [Au(tht)₂](CF₃SO₃), Ag(tht)(CF₃SO₃), H₂L and PPh₃ or PPh₂Py (2-(diphenylphosphino)pyridine). The Au₄Ag₄ cluster consists of a [Au₄L₄]⁴⁻ and four [Ag(PPh₃)]⁺ or [Ag(PPh₂Py)]⁺ units with Au₄L₄ framework exhibiting a twisted paper clip structure. In CH₂Cl₂ solutions at ambient temperature, both compounds show ligand fluorescence at ca. 463 nm as well as phosphorescence at 650 nm for 1 and 630 nm for 2 resulting from admixture of ³IL (intraligand) of L ligand, ³LMCT (from L ligand to Au₄Ag₄) and ³MC (metal-cluster) triplet states. Crystals or crystalline powders manifest bright yellow-green phosphorescence with vibronic-structured emission bands at 530 (568sh) nm for complex 1 and 536 (576sh) nm for complex 2. Upon mechanical grinding, yellow-green emission in the crystalline state is dramatically converted to red luminescence centered at ca. 610 nm with a drastic redshift of the emission after crystal packing is destroyed.     

Ag/Au Mixed Sites Promote Oxidative Coupling of Methanol on the Alloy Surface

Nanoporous gold, a dilute alloy of Ag in Au, activates molecular oxygen and promotes the oxygen‐assisted catalytic coupling of methanol. Because this trace amount of Ag inherent to nanoporous gold has been proposed as the source of oxygen activation, a thin film Ag/Au alloy surface was studied as a model system for probing the origin of this reactivity. Thin alloy layers of Ag_xAu_1?x, with 0.15≤x≤0.40, were examined for dioxygen activation and methanol self‐coupling. These alloy surfaces recombine atomic oxygen at different temperatures depending on the alloy composition. Total conversion of methanol to selective oxidation products, that is, formaldehyde and methyl formate, was achieved at low initial oxygen coverage and at low temperature. Reaction channels for methyl formate formation occurred on both Au and Au/Ag mixed sites with a ratio, as was predicted from the local 2‐dimensional composition.     

The thermal decomposition behavior of RDX-base propellants

In this paper, the thermal decomposition of cyclotrimethylenetri-nitramine (RDX)-base propellants involving many components has been investigated by differential scanning calorimeter (DSC). The decomposition characters at different heating rates and the activation energies are determined by DSC measurement. The results show that the decomposition of RDX is accelerated obviously during the decomposition of nitroglycerin (NG). Though the content of dibutyl-benzene-dicarbonate (DBP) ingredient in the propellants is less, it has a remarkable effect on the initial decomposition temperature of the propellants. The azido-nitromine compound (DIANP) brings about the shift of the peak of decomposition of RDX and nitrocellulose (NC) to lower temperature due to its liquefying or dissolving.     

Influence of inorganic fullerene‐like WS2 nanoparticles on the thermal behavior of isotactic polypropylene

A new family of thermoplastic nanocomposites based on isotactic polypropylene (iPP) and inorganic fullerene‐like tungsten disulfide (IF‐WS₂) has been successfully prepared. A very efficient dispersion of IF‐WS₂ material was obtained by mixing in the melted polymer without using modifiers or surfactants. The addition of IF‐WS₂ nanoparticles induces a remarkable enhancement of the thermal stability of iPP, as well as an increase in the crystallization rate of the matrix when compared with pure iPP. The nucleating efficiency of IF‐WS₂ solid lubricant nanoparticles on the α‐phase of iPP reaches very high values (60–70%), the highest values observed hitherto for polypropylene nanocomposites. The incorporation of IF‐WS₂ has also been observed to increase the size and stability of the crystals formed. The melting behavior of the nanocomposites indicates the formation of more perfect crystals as determined by differential scanning calorimetry and time‐resolved synchrotron X‐ray scattering experiments. The new nanocomposites show an increase in the storage modulus with respect to pure iPP measured by dynamic mechanical analysis. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2309–2321, 2007     

Nature and philosophy of thermal processes in minerals and inorganic materials

Solid-state thermal processes have their own specificity, distinguishing them from the processes in gases and liquids. This specificity includes, among others, their limited reversibility and the limited or modified role of chemical affinity as the main driving force indicating the direction of real solid-state processes. The consequency is the formation of metastable compounds or phases during heating, as intermediate steps towards the state of thermodynamic equilibrium. They are a results of the particular properties of the rigid internal structure of minerals and materials as the thermal reaction medium. The peculiarities of thermal reactions of solids are presented on the example of those of oxides (silicates and borates) with polymeric structures. The significance of crystal-chemical factors for the prediction or explanation of the course of high-temperature processes, as complementing the thermodynamic factors, is discussed.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthdayThis work was supported by grant P040703406 from the National Committee of Scientific Research of Poland.     

Influence of Al on the structure of liquid Cu0.70Si0.30 eutectic alloy

Short-range order of liquid Cu_0.7Si_0.3 eutectic alloy doped with 5, 10, 15 and 20?at.% of Al has been studied by means of X-ray diffraction method. Total structure factors and pair correlation functions are analyzed. It is shown that aluminum atoms form the self-associated structural units which are stable within some temperature range.     

Phase equilibria in the Ag4SSe-SnTe system

The phase diagram of the system Ag₄SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag₄SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag₄SSe·SnTe (phase A) and -Ag₄SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, =101.32°, =85.90°, =111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm, =90.74°, =108.94°, =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T _- =110°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

Structure and thermal behavior of metastable sillenites prepared by mechanochemical synthesis

The structure and thermal behavior of metastable solid solutions with nominal compositions Bi₂PbO₄, Bi₄HgO₇, Bi₁₂TlO_19.5, and Bi₁₂Cd_0.7O_18.7 with the sillenite structure obtained by mechanochemical treatment in a planetary mill (thermal decomposition of the metastable Bi₄CdO₇ phase with a bcc structure above 700 K) have been studied. The large Pb²⁺ atoms occupy up to ~30% positions in the sillenite structure (Hg²⁺ and Hg(1) occupy up to ~15% of (24f) positions). The (2a) sites are partially occupied by bismuth with a minor shift along the [111] axis and are transformed into the (8c) site, forming an umbrella structure with c.n. 3. The relatively small Cd²⁺and Tl³⁺ cations partially occupy the (2a) sites. During annealing, the metastable Pb-sillenites are partially stabilized with a loss of oxygen and increasing content of bismuth. Sillenite with a high content of lead retains its structure until it melts at 923 K. Cadmium sillenite reacts with CdO, passing into a rhombohedral structure at 900 K (30 K below the melting point). Mercury sillenite Bi₄HgO₇ decomposes with isolation of metallic mercury at ~600 K.Original Russian Text Copyright © 2004 by V. V. ZyryanovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 480–490, May–June 2004.