THERMAL CHANGES OF AMORPHOUS SiO2 AS A CONSEQUENCE OF A PRECIPITATION TEMPERATURE

Amorphous precipitate SiO2 as a subject of this research is obtained by reaction between Na-silicate, water solution (water glass) and sulphuric acid. The influence of precipitation temperature, upon the characteristics of obtained samples is analysed. The temperature is choosen as a parameter, which has a strong influence upon the structure and characteristics of a product, but it has a very narrow interval at the same time, where the precipitation process under an atmospheric pressure is possible. Some more important characteristics of the samples, obtained at 80-95 °C (values close to the limits of temperature interval where the precipitation reaction is possible), were analysed to show the essential differences, caused by the temperature. The analysis referred to determination of the dimensions of primary and secondary particles, density, specific surface area, and level of amorphous state (all this in green state). Then, the morphological and structural changes during heating at the characteristic temperature are followed. The changes are determined by the above characteristics and also by measuring the energetic values of some of them. Significant differences are noticed between samples where the higher precipitation temperature points to obtaining of amorphous precipitate with bigger primary particles, less specific surface area, higher density and higher molecular order which is manifested through faster and easier crystallization (when heating at 1100 °C)

Characterization of the particle size fractions of bentonite clay from Ginovci, Republic of North Macedonia

The examined bentonite clay contains montmorillonite as a basic mass. As an admixtures itcontaines quartz, illite and other minerals. The admixtures are inhomogeneously distributed in various particle sizefractions. The subject of this research is concentration and separation of existing admixtures from bentonite clay(–0.063 mm), a commercial product of Bentomak. Wet sieve analysis and elutriation were applied as separationmethods. In order to define the efficiency of the methods, a complex examination for characterization of the fractionswas realized. Simultaneous review of the results of XRD, microscopic examinations and chemical analysis indicatesthat in the finest fraction (–0.032 mm) the concentration of the admixures is smaller for 80% than in the other fractions

Characterization of diatomaceous earth from the Slavishko pole locality in the Republic of Macedonia

With the complex examination of raw material from a new deposit in Slavishko Pole in the region of Kratovo–Zletovo volcanic area, Republic of Macedonia, its physical, chemical and mineralogical-petrographical properties have been defined. It has been found that it is a dominantly amorphous material, sedimentary rock of the type silicite-diatomite, with biogenic or phytogenic origin. The raw material consists of approximately 72% SiO2 and it can be classified as diatomite of the type 1 (for 70–80% SiO2) according to British Standard Specification (BS 1795:1976) [1]. Of the physical properties, more significant is porosity, which is higher than 60%. The raw material has a wide spectrum of possibilities for practical application: intensive absorbent for several types of liquids, regulator of physical and chemical properties of the soil, ionic substitution of heavy metals in soil, natural insecticide, clarifier in food industry etc. For determination of the chemical contents, properties and origin of the raw material the following methods have been used: silicate chemical analysis, XRD analysis, transmission optical microscopy and other methods.Key words diatomaceous earth; characterization; chemical analysis; XRD analysis; optical microscopy

High temperature crystallization process into opalized tuff

White opalized tuff from the locality “Strmoš”– Probištip, is dominantly consisted of amor­phous SiO2 (over 90% mass), and a minor quantity of crystalline tridymite and quartz. Disordered structure of this material is consequence of its genesis. Fast transition from liquid to solid state enables existence of dominant amor­phous state. This is confirmed by X-ray analysis and optical transmission microscopy. Thermal treatment of the mate­rial at 1200oC causes higher degree of structure stabilization – crystallization of tridymite. The basic mass remains in the same disordered amorphous state, while the process of crystallization extends only in the zones with higher order degree. At the same time minimal changes occurs in the porosity, resulting in insignificant decreasing of specific sur­face area

Concentration of carbonate admixture from opalized tuff into one separate fraction

White opalized tuff (from the Strmoš locality, Probištip), as a raw silicate amorphous material,contains some quantity of admixtures. The total quantity of admixtures amounts is about 8% mass. Мine powdery ingredientsare homogeneously distributed into the basic silicate mass. Carbonate material is a significant part of presentadmixtures, and it is possible to be separated with controlled milling. Milling parameters (type and time of milling)enables to concentrate the present CaCO3 in granulometric fraction <0.032 m, after 30 min. milling. Reliableevidence about aforementioned separation is shown with simultaneous view of the results of silicate chemical analysis,DT/TG analysis (750–850oC), and sieve-analysis. From the X-ray analysis it is evident that the present carbonatematerial exists in crypto crystal to amorphous state. The space where CaCO3 is hidden, presents the place betweenbasic silicate particles inside the groups, generally with dimensions about 40 to 60 m. The concentration of CaCO3appears when this particle group goes to the process of disintegration

Phase transformations of amorphous SiO2 in diatomite at temperature range of 1000–1200°C

The phase transformations of the amorphous SiO2 have a very important role in the applicationof diatomite in the production of ceramic products. Therefore the phase transformations of diatomite are observedwith the use of DTA and TGA at temperatures up to 1100°C, and diatomite in powder state heated at temperature1000–1200°C for a period of 1 and 2 hours. DTA and TGA analyzis show that during thermal treatment up to 1100°Cthe diatomite remains in its amorphous phase. Roentgen-structural examinations of probes heated at 1000–1200°C fora period of 1–2 hours show no presence of crystalline phases at 1100°C. XRD examinations of probes heated at1200°C show presence of the crystalline phases cristobalite and quartz. The samples was heated at 1200°C for a periodof 2 hours, and was observed with an increase of the cristobalite content compared with quartz. SEM and TEMexaminations results of diatomite heated at 1200°C for a period of 2 hours show that the probes undergoes sinteringfollowed by reduced porosity

Physical-chemical and mineralogical-petrographic examinations of diatomite from deposit near village of Rožden, Republic of Macedonia

For the characterization of the natural amorphous SiO2 found in a new deposit in Republic ofMacedonia, the following examinations were performed: physical-mechanical, chemical, mineralogical, SEM, IR andthermal examinations. Physical-mechanical analyses show that it is a white to grey colored rock, of low hardness,with a low volumetric mass and high porosity. Chemical analyses show that the material dominantly contains SiO2.Mineralogical and XRD analyses show high percentage of isotropic amorphous mass content, with minimal contentsof submicroscopic cryptocrystalline mass. Thermal analyses show high thermal stability. Based on the conducted researchof the raw material from the new deposit, it can be concluded that it represents SiO2-diatomite of high quality,useful for various purposes

Diatomite – evaluation of physico-mechanical, chemical, mineralogical and thermal properties

Diatomite is one of the most intensively examined raw materials in the materials industry with a broad range of various applications. The diatomite sample, collected from Vitačevo plateau in the vicinity of Kavadarci, was fully characterized by means of physical-mechanical, chemical, XRPD, SEM, TEM, DTA/TGA and IR techniques. The physical-mechanical features pointed out to soft, light, white to gray rock with shell-like structure exhibiting compressive strength from 4.65–4.88 MPa in dry form, whereas the total porosity ranges 70–72% and the density is 2.06–2.09 g/cm3. The chemical analysis of the diatomite revealed that SiO2 content exceeds 91%. The results from the X-ray powder diffraction indicate predominant amorphous SiO2 phase associated with minor presence of crystalline quartz, muscovite, chlorites and plagioclase. The IR spectrum of the diatomite manifested characteristic bands for amorphous silica at 799 cm–1 and 1101 cm–1. DTA/TGA results display great thermal stability of the sample remaining amorphous up to 1050ºC whereas the SEM analysis determined the morphology, surface characteristics and the nanometric pores in the raw material. Thus, the studied diatomite is classified as a natural nanomaterial that is suitable for broad application in various construction materials, refractory ceramics, special oxide ceramics, and also finds potential use in filtering, adsorbent, catalysts, food and pharmaceutical industries

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality