CONTENTS no. 2/2003                                     Romanian Journal of Materials

ADRIANA SOMACESCU, ECATERINA ANDRONESCU, CLAUDIU SOMACESCU Synthesis and characterization of some ceramic, used for obtaining ceramic censors  
PETRU BALTA, CAMELIA CAPATANA Factors influencing the reddox processes implicating Cu in oxide glasses
NICOLAE PROTOPOPESCU, ZAMFIRA PLAIASU, DOREL RADU Optical and morphological characteristics of the float glass exposed to abrasion trickling   
MARIUS EUSTAFIEVICI, MARCELA MUNTEAN New trends in the development of ecological binders  
JENICA PACEAGIU, CRISTINA DUMITRESCU Factors influencing properties of some silicophosphate cements  
ION TEOREANU, STEFANIA STOLERIU, ADRIAN VOLCEANOV Concrete with vegetable aggregates  
SILVIAN MARICA, NECULAI CIORNEI, VALENTINA CETEAN Romanian sized stone - tendencies, aspects, strategies, premises for a lasting development  

Synthesis and characterization of some ceramic, used for obtaining ceramic censors

The paper presents the results obtained in the synthesis of some ceramic masses within the binary system SnO2 – CuO, adopting the solution of doping with substituent oxides (ZnO2 and Sb2O3).

Sn –Cu – Sb - O and Sn – Cu – Zn – O systems contain ceramics with specific electric and magnetic properties, which are employed as sensors, electrodes and catalysts.

All the investigated masses have compositions selected in the range of atomic ratio Cu : Sb(Zn) > 1, the only region where suitable dense ceramic materials are obtained.

In the present paper the correlations between the composition – structure – properties of the dense ceramic materials in the  Sn – Cu – Sb(Zn) – O  system  are shown using specific methods.



Factors influencing the reddox processes implicating Cu in oxide glasses

The redox processes are parts of the technological process of glass melting because in the usual compositions are present elements with variable oxidation states brought by row materials as impurities or deliberately introduced to influence the useful properties. More frequent are present the transitional elements from the first period, among them copper which has many uses. The redox equilibrium, which establishes during the glass elaboration, is influenced by nume-rous factors, which may be grouped in two categories: a) factors from outside of glass and b) factors related to glass composition.

  These factors are examined with special referee to copper. The advantage of basicity use as a correlation tool of properties with glass composition and structure is evidenced, allowing considering these factors by means of a single figure. Due to the fundamental character of basicity it correlates with all properties and facilitate the understanding and explanation of many phenomena.


Optical and morphological characteristics of the float glass exposed to abrasion trickling

Our paper refers to some phenomenological details of surface damage located on the float glass exposed to abrading grains trickling during a superposed rotation, and representative morphological and structural characteristics. This complex kinetic configuration simulates the real abrasion of a car windscreen when the vehicle rolls on a curved portion of the road.

Experiments with an original multifunctional installation (continuum variable column height, continuum speed and inclination of the specimen turntable) were performed. Three representative abrasives of the same granulometry, but having different mechanical properties and shapes were used: stainless steel balls, ovoidal quartz sand, and sharp silicon carbide (SiC).

The rotation speed was modified in steps of 10 rot/s and the inclination in steps of ten degree in order to obtain as much as possible correlations related to all imposed conditions of superposition.

 Representative morphological  and structural  details on the  glass  surface are finally  presented  as  optical microscopy images.


New trends in the development of ecological binders

Environment protection concerns both scientists and cement manufacturers. In the last decade new binders have been investigated and developed. The efforts focused mainly on reducing the clinker sintering temperature, lowering the lime saturation factor (LSF), and utilising industrial wastes. Some mechanical pro-perties of the analyzed binder systems are briefly discussed and final conclusions concerning the new trends are pointed out.



Factors influencing properties of some silicophosphate cements

The paper brings information on the obtainment and performance at hardening of silicophosphate dental cements of silicate type. Factors, such as: the solid component with its chemistry and sintering conditions (curing temperature, time elapsed at the plateau temperature), the liquid component with the neutralisation degree of the orthophosphoric acid solution, and the powder/liquid ratio, respectively, all of which are able to influence the silicate cement properties, have been considered.


Concrete with vegetable aggregates

In present paper, there are studied light concretes obtained from vegetable aggregates (industrial wood wastes). The specificity of fabrication technology for these concretes is based on the chemical treatment of vegetable aggregates for stopping their degradation in time. The principle of this treatment called mineralization, is to block those compounds which may favour the degradation process. The mentioned blocking process is realised mainly through the impregnation of vegetable aggregates surface with mineral substances (calcium chloride, ferrous sulphate, sodium silicate, fluorosilicates), which interact forming stable organominerals combinations.

Resinous aggregates (especially shavings), are indicated for obtaining this category of concretes, due to a more lower pentozans content reported to other wood essence – industrial wastes.



Fast analysis of the XRD profiles

The target of the original XRAY3.0 program was the rapid determination of microstructure parameters, crystallite mean size <D>, lattice mean strain <S> and lattice constants for crystallized powders from the x-ray recorded diffraction spectra. The principles that led to the formulation of the mathematical procedures contained in the program, were detailed in another work. The diffraction peaks have been simulated by Pearson-VII analytic functions. In order to test the way program works, there were discussed two applications: one regarding the analytic simulation of the XRD profiles at a NiO (1h/500°C) powder, the other one regarding the profile analysis where there were estimated the microstructure factors <D> and <S> with the help of the shape parameters of the profiles obtained by Langford, Louer, Sonneveld and Visser [1] for ZnO powders treated thermally at 280°C, 370°C and 950°C. The results of the program were compared with those reported in the literature, taking advantage from the fact that the Langford et al data are the source of the input data in the program, at the same time.


Romanian sized stone - tendencies, aspects, strategies, premises for a lasting development

The paper represents a synthesis of the present situation of the mineral resources for sized stone, derived from over 50 research studies on most of the Romanian operating and potential deposits of this kind, and from synthesis  geological  studies carried out by administration units (regions and counties) by the Laboratory of Mineral Resources and Geodesy within PROCEMA S.A.

  Romania is one of the countries with rich mineral resources of various geological natures, that can be exploited as sized stone in all the construction fields. The studies carried out showed that in 2001 there were 62 operating perimeters with resources for sized stone and over 200 operators on the building material market. The total production has not exceeded 0.6 from the total Romanian production of useful rocks, but the production  potential mag reach, in the   near future, up to abt. 500-600 thousand tons a year, that is up to over 5% of total production of the extractive industry.

  The physico-mechanical characteristics of the Romanian rocks for stones are good  and very good and have favourable processing aptitudes, especially thin tiles for finishes in verious media.


Romanian Journal of Materials