A modification to the derivatograph has been designed that allows thermoanalytical investigations of chemical compounds, including sulphides and acids, that evolve aggressive gases such as CO, SO2, S, etc. during warming. Application of this modification is exemplified by studies on the thermal dehydrogenation of titanium hydride (TiH1.85) and on the interaction of rhenium disulphide (ReS2) with concentrated sulphuric acid.
The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties
of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement).
The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control
samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength
determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding
heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of
spent catalyst and its influence on cement mortars being in contact with corrosive media.
Authors:J. Suñol, J. Saurina, F. Carrasco, X. Colom, and F. Carrillo
Lyocell, modal and
viscose fibers were subjected to mercerization or to solar degradation. The
ulterior thermal degradation was analyzed by means of differential scanning
calorimetry (DSC). Thermal analysis shows wide exothermic processes that began
between 250 and 300C corresponding to the main thermal degradation and
are associated to a depolymerization and decomposition of the regenerated
cellulose. Thermal degradation was analyzed as a function of concentration
and time. Lyocell fiber is the most stable under thermal degradation conditions.
Furthermore, mercerized samples are initially more degraded and present a
lower thermal stability.
Authors:I. Naumov, D. Lőrinczy, L. Vámhidy, P. Than, and N. Wiegand
body reaction that leads to increased osteoclast differentiation and maturation and decreased bone formation [ 1 ]. An aggressive granulomatous tissue, the interfacial membrane, develops at the bone/prostheses or bone/cement interface is shown in Fig
Authors:J. Wójcik, M. Makara, B. Janoszczyk, and K. Poturaj
An apparatus for thermogravimetric measurements is presented. This device gives the possibility of investigation reaction
as well as other processes taking place in aggressive atmosphere into the atmosphere composed of high purity gases. High flexibility
of the apparatus fitted into the MCVD line for optical fibres preparation provides a wide range of measurement possibilities.
Balances utilising the principle of free magnetic suspension can be very useful for thermogravimetric experiments, where aggressive atmospheres and high pressures are applied. Magnetic coupling systems with automatically controlled attraction can be used for direct conversion of weight into an electric signal or for the separation of object and beam balance. The magnetic suspension balance is described and a new versatile magnetic coupling system is presented. Due to its low weight, this coupling can be combined with a microbalance.
Authors:S.-H. Lee, J. La Rosa, J. Gastaud, and P. P. Povinec
New, quantitative methods for the determination of actinides have been developed for application to marine environmental samples (e.g., sediment and fish). The procedures include aggressive dissolution, separation by anion-exchange resin, separation and purification by extraction chromatography (e.g., TRU, TEVA and UTEVA resins) with measurement of the radionuclides by semiconductor alpha-spectrometry (SAS). Anion-exchange has proved to be a strong tool to treat large volume samples, and extraction chromatography shows an excellent selectivity and reduction of the amounts of acids. The results of the analysis of uranium, thorium, plutonium and americium isotopes by this method in marine samples (IAEA-384, -385 and -414) provided excellent agreement with the recommended values with good chemical recoveries.
Authors:I. Calliari, M. Dabalŕ, G. Brunoro, and G. Ingo
Patinae on Cu-base alloys have been characterized by means of GDOS, SEM, XRD and AFM. The effect of a protective coating was tested in aggressive artificial solutions. Patinae and the bulk of several metal Punic objects were also examined. The GDOS results combined with SEM capabilities allow exhaustive investigation of composition, element distribution and microstructure of modified surface in modern bronzes exposed to accelerated ageing tests as well as in ancient bronzes. The SEM data of the patina thickness agree with the GDOS data. The XRD and SEM investigations allow an exhaustive characterization of corrosion products. Corrosion growth in its early stages determines the effectiveness of the patina's protective role and the AFM is a promising technique for investigating this.
The chemical corrosion and the mechanical strength were studied in cement mortars containing an additive of FBCC under conditions
of long-term action of sodium sulphate solution or saturated brine. The observations have shown that saturated brine is a
more aggressive agent, since it leaches Ca(OH)2 and contributes to the decomposition of the C-S-H phase thus worsening the compressive strength as compared with that of
mortars kept in water. The addition of 20% FBCC inhibits the leaching process and counteracts the decrease of compressive
strength in mortars kept in brine. On the other hand, sodium sulphate solution changes favourably the mortar microstructure,
increases of the content of small pores and improves both the compressive and the flexural strengths, as compared with those
of a mortar kept in water.
This new study must be regarded to be a direct outcome of two previous studies published by these same authors, which were
conducted to respond to interesting questions brought out about the effect of silica fume, SF and metakaolins, M and MQ, on
the heat of hydration of portland cements, PC, with very different C3A and C3S contents. The answer to these so interesting questions has been the primary objective of the present research. For this
purpose, the same PC, PC1 (14% C3A) and PC2 (≈0% C3A), metakaolins, silica fume and blended cements were once again used more 60/40 for sulphate attack, and the same analytical
techniques (CC, pozzolanicity and XRD analysis) and parameters determined as well. In this new research, the sulphate attack
was determined by two accelerated methods: Le Chatelier-Ansttet and ASTM C 452-68.
The experimental results of sulphate attack mainly, have demonstrated definitively that the high, rapid and early pozzolanic
activity exhibited by SF also is, as in the case of the two metakaolins, more specific than generic, for it indirectly stimulated
greater C3A than C3S hydration, but only in the first 16 h monitored in this study. Thereafter it is the contrary, i.e., anti- or contra-specific
for the same purpose. And the longer the hydration time, the more anti- or contra-specific it became, since, when exposed
to sulphate attack, SF blended cements resisted or even prevented the aggressive attack against PC1 which, with a higher C3A content than PC2, was the more vulnerable of the two. By contrast, metakaolin MQ not only failed to hinder or prevent the
attack, but heightened its effects, rendering it more intense, aggressive and rapid, leading to what could be called a rapid