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Inorganic fibers and opacifiers are indispensable for improving the strength and high temperature insulation performance of the fumed silica-based thermal insulation material. However, zirconia fiber enhances the strength of the fumed silica-based thermal insulation material and reduces the radiative heat transfer to replace the opacifier. The sample of fumed SiO2/Al2O3 doped with 7% zirconia fiber (FZ7) has a lower density of 0.70 g/cm3 and a high porosity of 75.0%. In addition, the thermal conductivity of FZ7 at 800 °C is 0.077 W/(m·K), which is lower than the sample of fumed SiO2/Al2O3 doped with 7% glass fiber (FG7) and 0.089 W/(m·K) at 800 °C. The effective extinction coefficient of the thermal insulation material containing zirconia fiber is larger than that of the glass fiber by Fourier transform infrared spectroscopy analysis and calculation, indicating that the zirconia fiber has a distinct absorption and scattering effect on infrared radiation to reduce the radiative heat transfer. Therefore, zirconia fiber enhances the strength and decreases the high temperature thermal conductivity of the composites with the dual effect on the insulation and mechanical performance of the fumed silica-based thermal insulation material.

PURPOSE: To evaluate the color stability and mechanical properties of two commonly used maxillofacial silicone elastomers after addition of pigments and opacifiers and before and after artificial aging. MATERIALS AND METHODS: This study evaluated two maxillofacial silicone elastomers: A-2000 and M511. Two different pigment and opacifier systems (e-Skin and Reality Series) were used with the elastomers. Control groups (no pigment or opacifier) and experimental groups (each with subgroups containing additional pigments and/ or opacifiers) were fabricated for each of the silicone elastomers. A total of 51 specimens were evaluated for color stability, and 100 for mechanical properties. A spectrophotometer was used to assess CIE L*a*b* values before and after aging. CIELAB 50:50% perceptibility threshold (ΔE* = 1.1) and acceptability threshold (ΔE* = 3.0) were used to interpret color changes. A durometer and universal testing machine were used to evaluate the mechanical properties. ANOVA and Fisher least significant difference (LSD) test were performed to determine the statistical significance of the results (P < .05). RESULTS: Significant differences in color measurements (ΔE*) were found for all silicone groups following artificial aging (P < .05). ΔE* values for the mixed pigment/opacifier subgroups of both elastomers were below the perceptibility threshold. Additionally, after aging, the hardness, tear strength, and tensile strength significantly increased for all silicone groups (P < .05), while percent elongation significantly decreased (P < .05). CONCLUSION: Artificial aging affected the color stability and mechanical properties of the pigmented silicone elastomers with added opacifier. Overall, A-2000 with e-Skin group displayed the most color stability, with its mechanical properties being the least affected by artificial aging.

As compared with silica aerogels, alumina aerogels have excellent high-temperature stability, and hence, are regarded as a promising candidate for high-temperature thermal insulation materials. However, heat transfer mechanisms for such materials remain insufficiently explored. In this study, based on real material microstructures, an analytical thermal conductivity model for alumina aerogel-fiber-opacifier composites is developed via a modified parallel-series equivalent electrical circuit approach. The model takes into account solid, gaseous, and solid-gas coupling heat conduction in aerogels, solid heat conduction in both fibers and opacifier particles, and radiation in aerogels, fibers, and opacifier particles. The model is validated by comparing its predictions with measured thermal conductivity data. The model predictions reveal that there are two kinds of solid-gas coupling heat transfer mechanisms, which occur in the corner regions between interconnected secondary particles and in the slit regions between adjacent chains, respectively. Because of this coupling, the contribution of gaseous heat conduction is comparable to that of solid heat conduction and radiation of aerogels, fibers, and opacifier particles, which is well supported by experimentally measured data of thermal conductivity. The model is also used to analyze effects of various parameters on the thermal insulation performance of the composites, such as diameters and volume fractious of both fibers and opacifier particles.

TiO2 is a potential alternative opacifier to ZrSiO4, but it is restricted because it easily causes glaze yellowing due to the formation of rutile. Herein, the CaCO3-TiO2 composite with close interface combination was added into the raw glaze for sanitary ceramics to prepare white glaze with negligible radioactivity. The glaze added CaCO3-TiO2 exhibits the surface properties similar to the glaze added ZrSiO4 and its excellent opacifying effect with L* value of 89–94 is achieved by the crystallization of titanite. Moreover, the optimal glaze added CaCO3-TiO2 shows a white surface with b* value of 2.73, while the glaze added pure TiO2 shows a yellowish surface with b* value of 7−10. Mechanism analysis indicates that the tight interface combination between CaCO3 (CaO) and TiO2 can promote their combination reaction to form perovskite and further promote the formation of titanite. Therefore, the formation of rutile is inhibited, resulting in the white glaze surface.

The Hetian Bizili site in Lop County, located on the southern route of the Silk Road in Xinjiang, China, was a trade and cultural hub between the East and the West in ancient times. In 2016, a large number of glass beads were unearthed from the 40 tombs excavated on this site. In this study we determined the chemical compositions and manufacturing technology of bodies and decorations of twelve glass beads from the M5 tomb of Bizili by using LA-ICP-AES, EDXRF, Raman Spectrometry, and SR-μCT. The chemical compositions of the beads were all Na2O–CaO–SiO2, with plant ash mainly used as a flux. Lead antimonate and lead stannate were used as the opacifying agents. We detected elevated levels of boron and high levels of phosphorus in some beads: this is discussed in the context of the type of flux used and the possible use of a P-rich opacifier. Some of the beads with high contents of aluminum may potentially come from Pakistan. In terms of manufacturing technology, the craftsmen made ‘eye’ beads in different ways and also trail decorated beads.

Ternary mullite fibrous felt/opacifier/aerogel composites (MYTC) were prepared by impregnating the TiO2 opacifier/Y2SiO5 aerogels into mullite felts. The effect of the TiO2 opacifiers on the thermal insulation property of aerogel composite was investigated by adjusting the TiO2 opacifier contents from 0 to 15 wt%. The as-prepared MYTC exhibited low density of 0.195 g/cm3 and low thermal conductivity of 0.042 W/m/K. The high-temperature resistance of MYTC was tested using a self-designed thermal insulation test system. It was found that the addition of Y2SiO5 aerogels and TiO2 opacifiers significantly improved the thermal insulation performance of aerogel composites. The results demonstrated that MYTC showed more efficient heat insulation property as the back surface temperature of the MYTC was 157 °C lower than that of the mullite fiber felts as the front surface temperature of both was about 1200 °C. The as-prepared MYTC exhibited excellent high-temperature thermal insulation performance, making the materials potential application to high-temperature thermal insulation.

An experimental investigation is carried out to study the effect of operating parameters such as filling ratio, input heat, number of wick layers and thin coated wick on the thermal performance of a heat pipe .A film coating is a thin polymer- based coat applied to wick .the thickness of such a coating is usually between 20-100 micro meter .film coating formulations usually contain the following components: polymer, plasticizer, colourant, opacifier, and solvent. Coated material is a covering that is applied to the surface of an object ,the purpose of applying the coating may be decorative ,functional, or both ,The coating itself may be an allover coating, completely covering the substance, Functional coatings may be applied to change the surface properties of the wick, demineralized water used as working fluid. The total thermal resistance decreases with increasing filling ratio until filling ratio around between 0.5 and 0.6 then increases with increasing filling ratio, The total thermal resistance decreasing with increasing the number of coated layers of wick ,The total thermal resistance decreases with increasing heat input .

The reduction of radiation heat transfer in VIPs is an important issue. In VIPs, the radiation heat transfer is reduced by the use of opacifier. However, the amount of opacifier also significantly affects the cost of VIP. In this study, the effect of different types and sizes of opacifiers on VIP thermal conductivity was investigated. For this purpose, 6 VIP samples containing different opacifiers (SiC, graphite and calcium aluminate in 3 different grain sizes) were produced. Fumed silica, glass fiber and opacifier were used as fillers in VIP cores at 65%, 20% and 15% (by mass), respectively. VIP samples were vacuumed up to 0.1 Pa, and their thermal conductivity coefficients were measured according to TS EN 12667 standard. In addition, transmittance ratios (%T) of fumed silica, glass fiber, opacifiers and core samples were measured by FTIR spectrophotometer and the mass extinction coefficients of each sample were calculated. The silicon carbide (F1000) as the opacifier (e: 399 m(2) kg(-1)) and the graphite-containing core among the VIP core samples (e: 149 m(2) kg(-1)) exhibited the highest mass absorption coefficient. In addition, the thermal conductivity of the core samples without barrier was measured under 1 Pa vacuum and then the radiation conductivities were calculated from the obtained data. F800 type SiC significantly reduced radiation heat transfer, while the solid conduction of the core was increased due to its relatively coarse grain size. VIP sample with SiC (F1200) provided the lowest thermal conductivity at 0.1 Pa (3.94 mW mK(-1)). As a result, F1200 type SiC was found to be the most efficient type of opacifier among the investigated opacifiers.

High performance thermal insulation material was prepared by fumed silica as thermal insulation matrix, white cement as binder. SiC powder was incorporated as an opacifier. Short glass fibers were added to increase stiffness and minimize contraction. The samples were produced within 4 days under ambient pressure with no complicated equipment. The influences caused by white cement amount on the properties were investigated to achieve the optimal performance. A low thermal conductivity 0.033 W·m−1·K−1 at 25 °C and a low thermal conductivity 0.038 W·m−1·K−1 at 800 °C were achieved based on the experimental results. The linear shrinkage of the insulation up to 800 °C in air for 30 min was 7.54%. In addition, the insulation exhibited a compression stress above 0.15 MPa (3% strain). The relation between structure and performances was revealed. That we here publicly reported thermal insulation materials synthetized by nano-powder and inorganic binder might reveal a new method for synthesis high performance thermal insulation materials. Based on the simplicity of the manufacturing process, the optimized material properties and cheap cost of raw materials, we believe this technology can act as an effective thermal insulation material for buildings and myriad applications requiring improved thermal efficiency.

Non-invasive methods including micro-Raman spectroscopy (μ-Raman), micro X-ray fluorescence (μ-XRF), fibre optics reflectance spectroscopy (FORS) and environmental scanning electron microscopy (ESEM) were used to study thirty-five ceramic shards from Afrasiyab and forty-seven potshards from Nishapur. These shards are dated from the ninth to the tenth century AD and include various types of underglaze and inglaze decoration. Non-invasive scientific studies indicated that tin oxide was employed as a white opacifier in both sites while silicates including quartz, olivine, diopside and feldspar served as opacifier in Afrasiyab shards thus demonstrating a technological connection with the pre-Islamic tradition of glaze opacification. The white slip of most of the wares excavated at Nishapur contained dehydrated pyrophyllite which may be indicative of local production. Furthermore, while a dense distribution of chromite was found in the black underglaze decoration of the so-called yellow staining black ware from Nishapur, a diluted chromite probably obtained from a different source was used in the imitated lustre wares from Afrasiyab. Mixtures with different proportions of manganese oxide and black haematite were utilised as the black colouring agents. Taking all of these findings into account, it is proposed that a consistent ceramic technology and production is represented by the entire set of the shards from Afrasiyab while different materials and technologies are evinced in the Nishapur ceramics.

Poly(methyl methacrylate) (PMMA) bone cement is used to anchor the majority of total joint replacements (TJRs). Many brands of cement are used, both with and without the addition of antibiotics to reduce the risk of infection. The present study involved determination of various parameters in tensile fatigue loading: (1) energy absorbed (U) vs number of loading cycles (N) and creep strain (e) vs N, during fatigue tests on specimens of an antibiotic-containing cement (SmartSet GHV) and a plain cement (CMW1) and (2) crack length (a) vs fatigue loading cycles (N) and crack growth rate (da/dN) vs Mode I stress intensity factor range (ΔKI), during Fatigue Crack Propagation (FCP) tests. In the fatigue tests, four different sample types (round, machined; round, directly moulded; rectangular, machined, and rectangular, directly moulded) and tension-tension loading were used. In the FCP tests, compact tension specimens under tension-tension loading were used. It was found that there were limited effects of sample type, except at the highest stress levels, but that these two cements had different rates of crack propagation. These differences were reflected in the fracture surfaces with SmartSet GHV showing accumulation of opacifier around the particles and crack progression around the initial beads, while for CMW1 the opacifier was evenly distributed and the cracks went through the initial beads.

A novel method was developed to uniformly disperse sub-micron TiO2 opacifier into fiber reinforcements using agar and silica as binders via freeze drying. TiO2 opacifier/ fiber/ alumina-based aerogel ternary (TFA) composites with high strength and excellent high-temperature thermal insulation were successfully prepared by sol-gel route, impregnation process and supercritical fluid drying. The microstructure, mechanical and thermal insulation properties of TFA composites were investigated comprehensively. The results show that the mechanical property of TFA composites can be significantly enhanced by mullite fiber felt and the incorporation of SiO2 binder. The effect of TiO2 opacifier on the high-temperature thermal conductivity was studied by adjusting the content of TiO2 from 0 to 15 wt%. The obtained TFA composites exhibit high Young's modulus of up to 3.58 MPa and low high-temperature thermal conductivities of 0.129 W/m·K at 800 °C and 0.168 W/m·K at 1000 °C, respectively. The mechanism of heat transfer in TFA composites at high-temperature was also analyzed.

During a restoration and diagnostic campaigns carried out on Paestum funerary slabs belonging to the Lucanian funerary art, calcium antimonate (CaSb2O6) was detected for the first time in the pictorial layers. This artificial pigment, widely employed as opacifier both in ancient glass and glaze covering clay objects, was found in the wall paintings, regardless of the colour, supporting the hypothesis of an intentional addition of calcium antimonate to the pigments and the involvement of ceramic painters. A multi-analytical approach was performed on 32 funerary slabs (6th – 3rd century BCE), currently located at the National Archaeological Museum of Paestum (Italy) using both polarized light microscopy and environmental scanning electron microscopy equipped with energy dispersive X-ray spectrometer, micro X-ray fluorescence, micro Raman spectroscopy, Fourier Transform Infrared spectroscopy and powder X-ray diffraction. The results confirmed the use of a limited number of pigments, usually applied with fresco technique, although in many cases the stratigraphy of the painted layer showed morphology of mezzo fresco technique, but no organic binders were found. The hues of vegetal decorations were obtained using green earth, sometimes Egyptian blue mixed with yellow ochre, carbon and bone blacks, and orpiment. The alteration of green earth and other iron-containing pigments are likely responsible for the discolouration of the original hues. In red paints, hematite and red ochre are frequently associated with ilmenite, a typical volcanic mineral. Egyptian blue was used in blue paints while in black paints it was mixed with carbon and bone black pigments.

Lead-barium glass appeared during the late Warring States period in China (457 - 221 BCE) and was considered as a Chinese invention due to the unique presence of high barium. There is no indication as to how it was made. A set of twenty-four different combinations of possible raw materials were melted to test and systematically evaluate the possible recipes for lead-barium glass. Specifically, the function and source of sodium in lead-barium glass were explored. The results show that sodium source is crucial for lead-barium glass forming in this particular system. This paper explores an alternative formulation since sodium flux is not reported in historical Chinese sources, in which the Na2O is provided by including soda-lime glass in the mixture. This particular formulation provides a potential explanation for the source of the sodium in lead-barium glass.

Calcium antimonate (in the hexagonal or cubic form) dispersed in the glass matrix is an artificially synthesized phase commonly documented as opacifier for white glasses during the Roman period. Glasses of this type occasionally contain variable amounts of lead oxide. There is no consensus about the origin and role of the lead component in white glasses, whether it was functional to modify the workability of the glass and/or to help the precipitation of the particles, or whether it was an unintentional pollutant introduced with the raw materials. A group of lead and lead-free white mosaic tesserae from the fourth-century CE villa of Noheda in Spain were analyzed by differential scanning calorimetry (DSC) and high temperature X-ray diffraction (HTXRD) to evaluate the impact of variable amounts of lead oxide in the precipitation of calcium antimonate on the viscosity of the glass. The analyzed glasses show thermal events that have been related to the composition of the glass via multicomponent linear regression model. CaSb2O6 and Ca2Sb2O7 formed in the glass during the cooling phase and the glass was not reheated. Lead oxide influences the thermal behavior of the glass, lowering the onset temperatures of all the events, implying a more cost-effective production process. We propose that lead was added intentionally or that lead-bearing raw materials were selected specifically by the ancient glass artisans.

Titanium dioxide is considered the most efficient white pigment for opacification of thermoplastics. However, its high cost, combined with strong price oscillations due to production bottlenecks, has been driving the industry towards alternatives that might allow reducing the titanium dioxide content, while maintaining the product’s opacity. A strategy commonly used in waterborne paints consists in adding hollow polymer particles to the formulation, therefore achieving opacification due to light refraction at the air/polymer interface. In the current work, we show preliminary results that indicate that a similar strategy can be followed for thermoplastics opacification, as long as thermoset particles are used, in order to ensure preservation of the hollow geometry during melt-processing. Multi-vesiculated crosslinked styrene–polyester particles, produced by a single-step double emulsion process, are used. Evidence of synergic interaction between the multi-hollow particles and titanium dioxide has been found.

This study investigated the effects of inorganic silicone coatings on the load resistance of heat treated glass beams. The authors performed destructive load tests on 192 heat treated glas...

A selection of 10 Chinese enamelled metal wares dating from the 17th&ndash, 18th centuries (Qing Dynasty) was analysed on-site by mobile Raman microspectroscopy. These wares display cloisonn&eacute, and/or painted enamels and belong to the collections of Mus&eacute, e du Louvre in Paris and Mus&eacute, e Chinois at the Fontainebleau Castle in France. Pigments (Naples yellow lead pyrochlore, hematite, manganese oxide etc.), opacifiers (fluorite, lead arsenates) and corresponding lead-based glassy matrices were identified. One artefact was also analysed by portable X-ray fluorescence spectrometry (pXRF) in order to confirm the Raman data. In some of these metal wares, it is suggested that cassiterite was unpredictably used as an opacifier in some parts of the decor. The results are compared to previous data obtained on Chinese cloisonn&eacute, and Limoges enamels as well as recent data recorded on painted enamelled porcelains of the Qing Dynasty. Lead arsenate apatite detected in some of the 17th&ndash, 18th century blue enamelled decors is related to the use of arsenic-rich European cobalt ores, as also characterized in French soft-paste porcelain and glass decors and high-quality Limoges enamels for the same period. However, lead arsenate could then also have been deliberately used for white opacification. The specific Raman signature displaying the shape of the Raman scattering background indicates the presence of colloidal gold (Au&deg, nanoparticles) in red to violet enamelled and cloisonn&eacute, areas. At least three types of Naples yellow lead pyrochlore pigments identified with Sb-rich, Sn-rich and mixed Sb&ndash, Sn&ndash, (Zn, Fe?) compositions prove the use of European pigments/recipes.

The processing and validation of the zircon sand concentrate process into the zircon opacifier have been carried out. The purpose of this research was to determine the optimal processing conditions and the process validation parameters, namely the production repeatability, and product consistency. The optimum conditions were zircon sand concentrate 100 g was roasted with 15% NaOH at 400 °C for 3 hours, zircon opacifier leaching with 0.1 N HCl for 2 hours, drying at 105 °C, and milling until particle size escapes 200 mesh. The dominant mineral in the zircon opacifier by the XRD method was zirconium silicate (ZrSiO4). The processing zircon sand concentrate with seven replications, an average weight of zircon opacifier was obtained: (92.754 ± 1.707)%, and the production repeatability was 98.293%. So, the production repeatability was quite satisfying. The zircon opacifier composition from the seven replication processing, was obtained 10 oxides, including ZrO2: (85.220 ± 0.124)%, SiO2: (8.760 ± 0.206)%, HfO2: (2.475 ± 0.013)%, Al2O3: (1.183 ± 0.024)%, TiO2: (0.364 ± 0.018)%, Fe2O3: (0.131 ± 0.003)%, etc, the standard deviation of composition test results was 0.146% - 4.839% (lower than 5%), meaning that the consistency of the product was satisfactory.

The present study focuses on manganese-containing inclusions identified in late-Antique glass tesserae, light brown/amber and purple in colour, from Padova (Italy), in order to clarify the nature of these inclusions, never identified in glass mosaics until now, and provide new insights on the production technologies of such kinds of tesserae. Multi-methodological investigations on manganese-containing inclusions were carried out in this work by means of optical microscopy (OM), scanning electron microscopy (SEM), micro-X-ray diffraction (micro-XRD), electron backscattered diffraction (EBSD), electron microprobe (EMPA), and micro-Raman spectroscopy. The combination of analytical results shows that inclusions are crystalline, new-formed phases, mainly composed of manganese, silica and calcium, and are mineralogically ascribed as a member of the braunite-neltnerite series, with unit-cell parameters closer to those of neltnerite. However, the low Ca content makes such crystalline compounds more similar to braunite, in more detail, they could be described as Ca-rich braunite. The occurrence of such crystalline phase allows us to constrain melting temperatures between 1000 and 1150 &deg, C, and to hypothesize pyrolusite, MnO2, as the source of manganese. In addition, it is worth underlining that the same phase is identified in tesserae characterised by different colours (light brown/amber vs purple due to different manganese/iron ratios), glassy matrices (soda-lime-lead vs soda-lime) and opacifiers (cassiterite vs no opacifier). This suggests that its occurrence is not influenced by the &ldquo, chemical environment&rdquo, revealing these manganese-containing inclusions as a new potential technological marker.

The purpose of this work is to produce more excellent opaque wall tile glazes by using sapphirine instead of zirconium silicate as an opacifier. In order to achieve it, the chemical compositions were precisely adjusted in the system of SiO2-Al2O3-MgO-K2O-Na2O-B2O3. The morphological characteristics of the glaze were determined by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). And the optical properties of the glaze were characterized by a spectrophotometer and a gloss meter. The results reveal that well-shaped crystals of sapphirine (Mg2Al4SiO10) with needle-like morphology were formed as only crystal phase. The glaze is provided with better opacity whiteness and gloss compared with commercial zircon-based glass-ceramic glazes, and it is mainly composed of cheap mineral raw materials. Those features make it as an alternative one for improving the properties of conventional opaque ceramic glazes.

Opacifiers are usually doped in the silica aerogels to reduce the radiative heat transfer at high temperature. However, the doped opacifiers will enhance the heat conduction in the solid phase and increase the density of silica aerogels dramatically. For developing lightweight and efficient opacifiers, in this paper, different types of core/shell opacifiers are designed, and their extinction performance is investigated, theoretically. Then the optimal temperature-dependent particle size and doping amount of these opacifiers are obtained by maximizing the Rosseland mean extinction coefficient and minimizing the total thermal conductivity of silica aerogel composite. The results show that the hollow carbon black opacifiers might greatly reduce the densities of the opacifier-doped silica aerogels without deteriorating appreciably their insulating capability, and the carbon/SiC, carbon/TiO2 and carbon/Al2O3 core/shell opacifiers exhibit excellent extinction performance and would be strong candidates for high temperature due to their high extinction performance, low density and high-temperature stability. Finally, a core/shell opacifier-gradient-doped silica aerogel based on the optimal opacifier types and doping amount is designed, which significantly improves the insulating performance and reduces the density of silica aerogel composite. The results of this paper present important references for the process design and improvement of comprehensive performance of opacifier-doped silica aerogels.

This paper investigated the effects of laboratory synthesised rocket composite propellants’ formulations on propellant performance parameters using response surface methodology (RSM). For the sake of a safe environment, the propellant is made of chemical constituents that have less severe effects on air quality. Experimental measurements of propellant performance parameters were carried out using the ballistic evaluation method. The thrust generated during combustion, the burn time and the propellant combustion temperature were measured using a data acquisition facility equipped with a button load cell and a thermocouple. Specific impulse, density, temperature, characteristic velocity, molecular weight and heat ratio were computed from the measured parameters. The resulting optimum rocket composite propellant formulations were 65.1%, 18.1%, 9.1%, 3.6%, 2.2% and 1.9% for the oxidiser, binder, fuel, opacifier, burning rate enhancer and catalysts, respectively. The corresponding performance indices i...

This study focuses on a group of decorated glass beads (twelfth–tenth century BC), belonging to a larger assemblage that was excavated from the prehistoric burial tumulus at Lofkend, Albania. The bulk glass, opaque glass decorations, and corroded areas were examined and analyzed using variable pressure-scanning electron microscopy with energy-dispersive spectroscopy (VP-SEM-EDS) and X-ray diffraction (XRD). The four glass beads analyzed were made using a plant ash-based alkali and colored with an iron containing chromophore which gave the glass its dark green color. Calcium antimonate was the predominant white opacifier used. Sodium antimonate was found as the opacifier in one sample. Its occurrence is likely accidental and formed due to a low concentration of calcium in the glass. Lead antimonate was identified in one sample and, along with calcium antimonate which was also present, would have acted as an opacifier for the white glass.

The paper presents aerogel SiO2–TiO2 composites used for thermal insulation of hydrothermal reactor for biomass-to-hydrogen conversion and the method of their production. The technology of aerogel composites production includes the following stages: ion exchange of liquid Na-glass resulting in production of silica hydrosol; hydrosol concentration; hydrogel production and its maturing; SiO2–TiO2 alcogel production; modification of its surface; subcritical drying of alcogel resulting in production of SiO2–TiO2 ambigel; its thermal treatment, granulating and classification. The influences of infrared opacifier (titanium dioxide) and thermal treatment temperature of SiO2–TiO2 composite on its structural and thermal characteristics have been investigated. Possibilities of hydrogen yield increase by reduction of power waste by means of vacuumized thermal insulation for reactor walls have been examined.

A facile and effective polymer-derived ceramics (PDCs) emulsification-crosslinking-pyrolysis method was developed to fabricate SiCN@TiO2 core-shell ceramic microspheres with polyvinylsilazane (PVSZ) and tetrabutyl titanate (TBT) as precursors. The TBT: PVSZ mass ratios, emulsifier concentrations and the pyrolysis temperature were examined as control parameters to tune the size and morphology of microspheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the synthesized SiCN@TiO2 microspheres to be comprised of SiCN core coated with TiO2 crystals, with an average size of 0.88 μm when pyrolyzed at 1400 °C. The analysis of Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) ensured that SiCN@TiO2 core-shell ceramic microspheres composed of rutile TiO2, β-SiC and Si3N4 crystalline phases, The thermal properties were characterized by thermogravimetric analysis (TGA). The obtained SiCN@TiO2 core-shell ceramic microspheres were the promising candidate of the infrared opacifier in silica aerogels and this technique can be extended to other preceramic polymers.

Radiative properties such as spectral extinction coefficient, Rosseland mean extinction coefficient and radiative thermal conductivity are the key features of porous insulation materials. For silica aerogel composites with fiber and opacifier, it is difficult to determine the spectral extinction coefficient and radiative thermal conductivity via experiment accurately. The spectral extinction coefficient of such composites is usually determined by a transmittance test using KBr as a diluent. The traditional model has several assumptions on determining the extinction coefficient from the transmittance measurement: the diluents are assumed as a pure transparent medium, the pressed pellet has no reflection, and the composite powder is in series with the KBr when calculating the effective thickness of the composite. Thus, the extinction coefficient determined from the traditional model with these assumptions will result in some uncertainty on predicting the radiative thermal conductivity. To overcome the drawbacks, improved models are proposed by considering the absorption of KBr diluents, sample reflection and random distribution of sample powder in the diluents. KBr diluted silica aerogel composite pellets with the same constituents and concentrations but different thicknesses are prepared using the pressed pellets method. The transmittances of the pressed pellets are measured by Fourier transform infrared spectroscopy (FTIR). The spectral extinction coefficients are calculated from the measured transmittances with proposed models. The radiative thermal conductivity of silica aerogel composite is calculated with the measured Rosseland mean extinction coefficient determined from different models. This study found that the developed models could eliminate the assumptions of the traditional model.

The thermal insulation material composed of fiber-reinforced fumed silica (in the raw and opacified with silicon carbide, zirconia or titania powders) was produced and analyzed. Optical properties (scattering and absorption coefficients) were experimentally examined in the spectral range of 0.9 – 4.7 µm by the solution of the inverse problem of radiative transfer. The inverse problem was based on the invariant embedding equation and the measured spectral directional-hemispherical reflectance. The effect of silicon carbide opacifier addition on the optical properties, effective and radiative thermal conductivity was estimated. The calculated radiative thermal conductivity of thermal insulations with various volume fractions of SiC opacifier was compared to the one deduced from the effective thermal conductivity using the calorimetric technique of conductive and radiative components separation. The effective thermal conductivity was measured by the quasi-stationary technique in the temperature range of 373 – 1173 K. The results of the inverse problem solution were compared to the calculations based on the Mie theory and the measured size distribution of silicon carbide particles. The experimental scattering coefficient was shown to be smaller than the calculated one. At the same time, absorption coefficients demonstrated mutual consent. Possible uncertainties in SiC powder size and the complex refractive index of the basic material were considered as a probable explanation of the obtained results. The size distribution of SiC opacifier was numerically optimized to obtain as low Rosseland mean radiative thermal conductivity as possible. The influence of the opacifier chemical composition was analyzed by collating radiative thermal conductivity deduced from the measured effective thermal conductivity to ones calculated using Mie theory. Finally, the effect of Fe2O3, Si3N4, TiO2, graphite, ZrO2, TiN, TiC, AlN opacifiers was numerically analyzed using Mie theory. Compounds based on titanium and an iron sesquioxide were shown to be promising opacifiers for high temperature applications.

Eighteen glazed objects from Nimrud, Hasanlu and Borsippa dated to a period from the ninth to sixth century BCE were analysed by micro X-ray fluorescence (μ-XRF), X-ray diffractometry (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and micro-Raman spectroscopy (μ-Raman). While calcium antimonate (CaSb 2 O 6 ) and lead pyroantimonate (Pb 2 Sb 2 O 7 ) were the main white and yellow opacifiers of the glazes, respectively, white sodium antimonate (NaSbO 3 ) was also sporadically observed in the Nimrud glazes. Copper sulphide associated with cassiterite (SnO 2 ) was used as colouring agent – or probably as opacifier – in a green glaze from Hasanlu. Cassiterite associated with the slag of Cu-Sn copper alloys was also observed in a green glaze from Nimrud suggesting a close tie between metallurgy and glaze-making. Pyromorphite (Pb 5 (PO 4 ) 3 Cl) and arsenian pyromorphite were observed in spherical forms embedded in the yellow glazes of Nimrud and Borsippa.

Due to pure silica aerogel is fragile and nearly transparent to 3–8 μm infrared beam, reinforced fiber and opacifier are composited with silica aerogel to optimize its performance. The suppression of radiative heat transfer is related to opacifier type, size and content. However, the addition of opacifier will enhance solid conduction inevitably. In addition, the influence of doping opacifier will also be affected by temperature since thermal radiation is temperature and wavelength dependent. Therefore thermal conductivities of 10 fiber and opacifier doped silica aerogel composites are studied experimentally and theoretically. Transmittances of silica aerogel doped with opacifier of different type, size and content are measured within 1.4–25 μm by FTIR. The spectral extinction coefficient of fiber/opacifier loaded silica aerogel composite is obtained by considering the practical absorption of KBr diluents. The thermal conductivity of silica aerogel composite is measured by transient plane source method at different temperature and gas pressure. Effective model with considering heat conduction via gaseous molecules, matrix skeleton, fiber, opacifier and thermal radiation via skeleton, fiber and opacifier is developed for fast predicting the thermal conductivity of fiber/opacifier doped silica aerogel composite. It is found that the silica aerogels doped with SiC or TiO 2 particles has lower radiative thermal conductivity than that doped with ZrO 2 particles with volume fraction of 3.75% and diameter of 3.5 μm. Silica aerogel doped with 3.75%, 3.5 μm SiC particles has the lowest thermal conductivity at temperature less than 1000 K.

Nano-porous silica aerogel material exhibits extensive application prospects in aerospace, industry and buildings for excellent thermal insulation and energy efficiency owing to its ultra-low thermal conductivity. To further improve the high-temperature thermal insulation and mechanical property of aerogels, infrared opacifiers and reinforcing fibers are added into the aerogel matrix to form ternary opacifier/fiber/aerogel composites. In this study a theoretical model of predicting thermal conductivity of the ternary opacifier/fiber/aerogel composite is presented and validated with experimental results. Based on the model the effects of ternary opacifier/fiber/aerogel contents on the thermal conductivity are investigated by using a seven-batch ternary factorial design. A super-thermal insulation of 0.0185 W·m−1·K−1 is achieved when the ternary opacifier/fiber/aerogel contents are 10 wt%, 5 wt% and 85 wt% respectively. The coupling effect of the ternary opacifier/fiber/aerogel contents on the thermal conductivity of the composites is then explored to decrease the coupling thermal conductivity and improve the thermal insulating performance of the ternary aerogel composites. The results indicate that the coupling thermal conductivity can be decreased by enlarging the difference between the fiber and opacifier contents. This study could be used in the design of ternary opacifier/fiber/aerogel composites for improving their super-thermal insulation. Keywords: Silica aerogel, Ternary composite, Thermal conductivity, Thermal insulation, Factorial design

A novel sol-gel chemistry approach was developed to enable the simple integration of a cast-in-place, ambiently-dried insulation into high temperature applications. The insulation was silica-based and synthesized using methyltrimethoxysilane (MTMS) as the precursor. MTMS created a unique silica microstructure that was mechanically robust, macroporous, and superhydrophobic. To allow for casting into and around small, orthogonal features, zirconia fibers were added to increase stiffness and minimize contraction that could otherwise cause cracking during drying. Nano-sized titania powder was incorporated as an opacifier to reduce radiative heat transport. To assess relevance to high temperature thermoelectric generator technology, a comprehensive set of materials characterization experiments were conducted. The silica gel was thermally stable, retained superhydrophobicity with a water contact angle >150°, and showed a high electrical resistance >1 GΩ, regardless of heating temperature (up to 600 °C in Ar for 4 h). In addition, The silica-based thermal insulation exhibited a Young's modulus ∼3.7 MPa and a low thermal conductivity

Silica aerogel as a super-insulating material is widely used in thermal protection system of spacecraft and aircraft. However, the significant radiative heat transfer causes obvious deterioration in the insulation capability of silica aerogel at high temperature because the pure silica aerogel is almost transparent to infrared radiation in such a spectrum range. Doping fibers or opacifiers could greatly improve the thermal insulation properties at high temperature. In this paper, we determine the optimal temperature-dependent size for typical opacifiers and silica fibers by calculating radiative properties. Suppose that the opacifier particles are spherical and the fiber is an infinite cylinder. According to the Mie scattering theory, the extinction efficiency factor of single opacifier particle and single fiber could be obtained. Then, the extinction coefficient could be calculated which characterizes thermal insulation performance of aerogel composites. The results show that the radiative thermal conductivity increases with increasing temperature, thus smaller particles and thinner fibers are more suitable for doping at high temperature. In addition, the carbon black has the best extinction characteristic in the four types of studied opacifiers (carbon black, SiC, ZrO2 and TiO2), but it will be oxidized at high temperature. Compared with TiO2 and ZrO2, the insulating performance of the SiC opacifier is more effective at high temperature. Although doping opacifier or fiber in silica aerogel provides a better extinction function, it might increase the heat conduction. Therefore, we could achieve an optimal doping amount at the minimum effective thermal conductivity, in other words, the highest insulating capability. The effective thermal conductivity in doped silica aerogel is equal to the sum of the conductive thermal conductivity and the radiative thermal conductivity. The optimal temperature-dependent doping amount is obtained by minimizing the effective thermal conductivity. The results show that the optimal doping of both opacifier and fiber amount in silica aerogel increases with the temperature. In addition, the carbon black behaves the strongest ability to inhibit heat transfer when the temperature is below 600K, while the SiC doped silica aerogel has the most effective performance in suppressing heat transfer when the temperature is higher than 600K. Optimized results were applied to design multi-layer doping with a temperature gradient. Each layer is doped with the corresponding optimal size and amount of opacifiers and fibers according to the temperature. Assuming that the temperature changes linearly in the direction of heat transfer, we studied four multi-layer solutions as follows. Solution 1 is the only SiC opacifier multi-layer doping. Solution 2 is SiC and carbon black opacifier multi-layer doping. Carbon black opacifier only exists in the temperature below 600K, otherwise the SiC is doped, which could ensure that only a single type of opacifier was doped for each layer. Solution 3 is the only silica fiber multi-layer doping. Solution 4 is the optimal co-doping of opacifier and silica fiber, which is similar to Solution 2 but mingled with silica fiber in each layer. The results show that the silica fiber only doping has the smallest effective thermal conductivity, and the co-doped silica aerogel with carbon black, SiC opacifier and silica fiber has the smallest radiative thermal conductivity. To verify the above results, the back temperature curve of doped silica aerogel was measured. Silica aerogel doped with various types of opacifiers and SiC in different particle sizes and doping amounts were considered. In addition, the back temperature of SiC-multi-layer doped silica aerogel was investigated. The predictions agree with experimental results qualitatively.

In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD), Positron Annihilation Lifetime Spectroscopy (PALS), and Perturbed Angular Correlations (PAC)) in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and themodifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line. Additionally, HPGe gamma-ray spectroscopy confirms the occurrence of significant levels of natural radioactivity responsible for metamictization in the investigated zircon samples. Results from XRD, PALS, and PAC analysis confirm that the metamict state of zircon is a dispersion of submicron disordered domains in a crystalline matrix of zircon., Facultad de Ciencias Exactas

Sb was frequently used as a raw material, both in ancient glass-making (as an opacifier and decolouriser) and metallurgy (either as an alloying element or as a pure metal). Despite this ubiquity, antimony production has only occasionally been studied and questions concerning its provenance are still not satisfactorily answered. This study evaluates the suitability of Sb isotope analysis for provenance determination purposes, as experiments under lab conditions have revealed fractionation occurring during redox processes in oxidising stibnites and in making opacified glasses. The results of this paper help to evaluate the possible influence of the pyrotechnological processes on the antimony isotope composition of glass artefacts. This paper focuses on the Caucasus as case study by applying mineralogical, geochemical and isotopic analysis to Georgian ores (mainly from the Racha-Lechkumi district) and Late Bronze Age (LBA; 15th-10th century BCE) metallic Sb objects found at the sites of Brili and Chalpiragorebi.[GRAPHICS].

In large parts of the Mediterranean recipes for the earliest man-made glass changed from melting mixtures of crushed quartz pebbles and halophytic plant ashes in the Late Bronze Age to the use of quartz sands and mineral soda during the Early Iron Age. Not much is known about this transition and the experimental materials which would inevitably have been connected to such technological change. In this paper we present a unique snapshot of developments in glass technology in Anatolia during the Middle Iron Age, when glass is still a relatively rare commodity. The present work focusses on black glass beads decorated with yellow trails from eighth to seventh century BCE Sardis, glass beads that are very rare for this period, and on this site. A full elemental analysis of the beads was made, and Sr, Pb and B isotope ratios were determined. This study reveals the use of a combination of a previously unknown source of silica and of mineral soda, giving rise to elevated (granite-like) Sr isotope signatures, as well as high alumina and B concentrations. The yellow trails of glass on the beads consist of lead-tin yellow type II, lead stannate, showing the earliest occurrence of this type of opacifier/colourant so far, predating any other findings by at least four centuries. The production of these glass beads may be local to Sardis and experimental in nature. It is therefore suggested that Sardis may have played its role in the technological development of the glass craft during the Iron Age.

Ceramics are the most ancient material used by humankind, in the form of earthenware. Whiteware encompasses many subcategories, such as sanitary ware, porcelain ware, earthenware, and stoneware. Clays used in the whiteware body are classified into two types: plastic clay and non-plastic clay. The clay–quartz–feldspar phase diagram represents the composition of all types of whiteware bodies, such as porcelain stoneware, white stoneware, soft porcelain, hard porcelain, laboratory porcelain, stoneware, earthenware, and dental porcelain. Transparent glazes are prepared without the addition of any opacifier. A translucent glaze is applied purposefully for decoration as a glossy surface. The glaze on a ceramic body is a thin coating of glaze or glass-ceramics. The presence of glaze defects after firing may render the final products rejected or discarded as scrap. Peeling or shivering is a glaze defect in which the glaze breaks away from the body/ceramic ware mainly due to a mismatch in the thermal expansion coefficient between the glaze and the body.

Statement of problem A significant challenge of craniofacial prostheses is their limited service life because of degradation and color instability. In spite of improvements in the materials and techniques used for the fabrication of silicone maxillofacial prostheses, undesirable color change over time remains a challenge. Zn and Ti nano-oxides (nano-TiO2) have been reported to impart an ultraviolet- (UV) shielding property to silicone elastomers. However, studies examining the effects of nanopigments on the color stability of craniofacial prostheses are sparse. Purpose The purpose of this in vitro study was to evaluate the color stability of a room-temperature vulcanizing (RTV) silicone elastomer with the addition of iron oxide and titanium dioxide nanopigments under accelerated artificial aging. Material and methods Sixty disks (O15×2 mm) were fabricated from RTV silicone 4408 Q. The specimens were divided into 5 groups containing iron oxide nanopigment, iron oxide nanopigment and rutile nano-TiO2 (as an opacifier), burnt sienna pigment, burnt sienna and nano-TiO2, and silicone without pigment or opacifier. The specimens were subjected to accelerated aging in a Xenotest chamber for 1000 hours. CIELab color coordinates and the total color difference (ΔE∗) values were determined before and after aging. ΔE∗ values were compared between the groups by using 1-way ANOVA and Tamhane multiple comparisons (α=.05), and a standard deviation of 1.09 was considered. Results ANOVA showed that the values of ΔE∗ differed among all groups (P Conclusions Nano-TiO2 with burnt sienna groups had a lower color change than the other groups. The color change in all groups was within a clinically acceptable range.

Five scarabs and one scaraboid found in Vinha das Caliças 4 (Beja, Portugal) were analyzed using a micro-analytical methodology in order to determine their mineralogical and chemical composition. Microstructural characterization and chemical analysis revealed that all were composed of a white body of crushed feldspathic sand covered by a lead-rich, alkaline-depleted silicate blue-green glaze showing evident signs of glass deterioration. Variable pressure scanning electron microscopy with X-ray energy dispersive spectrometry, handheld X-ray fluorescence spectroscopy, and micro X-ray diffraction results show that blue-green color of the glaze was produced by using copper ions (Cu2+) in conjunction with the lead antimonate bindheimite, a yellow-colored opacifier. The introduction of small amounts of tin in the structure of bindheimite enabled the production of a ternary Pb–Sb–Sn oxide. Tin, which was most likely added with the copper source (bronze scrapings), is known to facilitate the crystallization of bindheimite. The results are consistent with the five scarabs and one scaraboid being manufactured in Egypt. This study, the first archeometric study of scarabs found in the Iberian peninsula, has greatly contributed to the understanding of the influence of the Eastern and Central Mediterranean world in the Southwestern Iberia during the first millennium B.C.

In ceramic tile manufacturing, ?-Al2O3 is the main type of alumina used in ceramic body and glaze formulations. It acts as an opacifier in porcelain tile bodies and as a matting agent in glazes. White fused alumina (WFA) is produced by fusing calcined alumina in an electric arc furnace under carefully controlled conditions. It is generally preferred in ceramic floor tile glazes in order to increase abrasion resistance. The aim of this study was to establish a better understanding of how alumina and WFA addition affects the thermal behavior, microstructural evolution and aesthetic properties of transparent floor tile glazes. The results showed that both alumina and WFA increased the sintering and melting temperatures of the standard commercial glaze. Corund was detected in the main phase with WFA addition in tile glazes. There were no other crystalline phases formed since WFA did not react with glassy phase. This behavior can be attributed to higher refractoriness of fused alumina. Smoother surface and homogenous structure were observed in the glazes with WFA addition. However, anorthite and corund phases were detected in the glazes with alumina addition. High crystallization glazes with rough surfaces were observed in these glazes. Alumina was found to be more effective to increase opacity and reducing glossiness compared WFA addition. © 2019, Akadémiai Kiadó, Budapest, Hungary.

A vacuum super insulation for temperatures up to 1073 K has been developed using an opacified powder mixture with high-density ( ρ = 180 kg m−3) expanded perlite as base material. To analyze radiative transfer, the mass-specific extinction coefficient e of expanded perlite and various opacifiers (SiC, B4C, FeTiO3, TiO2) has been determined by FTIR spectrometry. For reduction of radiative transfer, a SiC powder with mean grain diameter of 2 μm–4 μm and bulk density of 870 kg m−3 has been identified as most suitable opacifier, also under economic aspects. Subsequently, six homogeneous powder mixtures with weight fraction w of SiC between 0% and 60% have been prepared. In order to determine the optimum w , guarded hot plate (GHP) measurements under high vacuum conditions ( p λ e = 13∙10−3 W m−1 K−1 for w = 40% and ρ = 263 kg m−3. This mean temperature corresponds to an insulation application with 950 K hot-side and ambient temperature cold-side. For the optimum mixture with w = 40%, e has likewise been determined with FTIR spectrometry. Furthermore, λ e has been measured with the GHP method also at mean temperatures between 373 K and 873 K, where excellent values between 4∙10−3 W m−1 K−1 and 20∙10−3 W m−1 K−1 have been obtained. For the evaluation of these measurements, two different methods have been applied in order to separate radiative thermal conductivity λ r and solid thermal conductivity λ s : first the common plot of λ e versus T 3 , and second an improved method, which includes the temperature dependencies of e and λ s . Expanded perlite, opacified with SiC, has proven as a highly efficient and economic vacuum super insulation material for industrial applications up to 1073 K.

For polymer foams with low-density, the thermal radiation propagating through the foam still contributes significant to the total thermal transfer. It is very promising to enhance the absorption or reflection of IR radiation by the foam matrix. However, it is still a question which of the reflected infrared or absorbed infrared is more effective in reducing radiative thermal conductivity. In this work, we studied theoretically and experimentally the effectiveness to reduce the radiative thermal conductivity of polymer foams by reflection mode and absorption mode. The relationship between the optical parameters of foam and the heat radiation transmission in the foams was quantitatively investigated. It was found that, taking into account the re-emission, the radiative thermal conductivity was further reduced merely by increasing the absorption coefficient, but in theory it could continue to drop to zero by increasing the reflection fraction. Both the flake aluminum powder (FAP) that mainly reflects infrared and the flake graphite powder (FGP) that mainly absorbs infrared were added to the rigid cross-linked PVC (c-PVC) foam. The results demonstrated that the reduction of radiative thermal conductivity of the c-PVC foam with FAP was more significant than of the c-PVC foam with FGP. The experimental results were in good agreement with the theoretical prediction.

Rigid poly (vinyl chloride) [PVC] composites with 0 to 4 wt% of either conventional or nanoscale rutile titanium dioxide filler were injection molded. Rutile titania absorbs solar UVR efficiently and is typically used in rigid PVC formulations as an opacifier and protects the polymer from light-induced degradation. A comparison of the stabilization effectiveness of the two types of fillers were assessed by monitoring the change in tensile properties and development of light-induced surface yellowing of the composites on exposure outdoors as well as under laboratory accelerated conditions. A comparison of the conventional and nanoscale uncoated rutile tiania as a light-stabilizer in rigid PVC is reported. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

Radiative heat transfer at high temperature deteriorates the insulating capability of silica aerogel due to its poor extinction characteristics for wavelength below 8 μm. Both the infrared opacifier doping and fiber doping can reduce the heat transfer and improve insulating capability of silica aerogel efficiently at high temperature. We determine the optimal temperature-dependent size for typical opacifiers and silica fibers by combining the spectral extinction coefficient with blackbody radiation. The optimal temperature-dependent doping amount is obtained by minimizing the effective thermal conductivity. Based on the obtained temperature-dependent optimal parameters and the graded temperature distribution in silica aerogel, four solutions of multi-layer graded doping are presented and the insulating capability is improved effectively. The measured back temperature curves of doped silica aerogel in the experiment qualitatively verify the optimization predictions.

The efficacy of titanium dioxide as an opacifier for glass ceramic, wear-resistant, semi-fritted, glaze coatings with the required physical, chemical, and operating characteristics for floor tiles is determined. Infrared spectroscopy, x-ray phase analysis, and electron microscopy are used to perform a comprehensive study of the formation of composition-optimized glaze coatings.

In tile manufacturing alumina acts as an opacifier in porcelain tile bodies and as a matting agent in glazes. Calcined alumina is a versatile and a new material for glaze industry due to it’s the densest and more stable crystalline form of alumina. The study was accented on examining of the effect of alumina characteristics and concentration on thermal behavior, phase evolution and optical properties of wall tile glazes. For this purpose several wall tile glazes which contain different phases of alumina and a different concentration were prepared and fired in industrial firing cycle. In the study it was showed that softening and melting temperatures of the wall tile glazes were increased with the increment of the alumina concentration. The crystal phases were detected as anorthite, corundum and gahnite. Depending on the forming of new crystalline phases, glazes with different aesthetic properties were obtained in the study.

This paper presents aerogel SiO2–TiO2composites used for thermal protection of biomass-to-hydrogen hydrothermal reactor and the method of their production. The technology of aerogel composites production includes the following stages: ion exchange of liquid Na-glass leading to formation of hydrosol silica; hydrosol concentration; formation and maturing of hydrogel; production of SiO2-TiO2alcogel; modification of its surface; subcritical drying of alcogel leading to formation ofSiO2-TiO2 ambigel; its heat treatment, granulating and classification. The influence of the infrared opacifier (titania) and the heat treatment temperature of SiO2-TiO2composite on its structural and thermal characteristics is investigated. Possibilities of increasing the hydrogen yield by reduction of energy losses using vacuum thermal insulation for reactor walls are examined.

The paper presents a historical evolution of compositions and applications of glazes on various ceramics (majolica, facing tile, glazed pottery, porcelain). The origin and development of artistic and industrial enameling processes for metals are described. The effect of additions in glazes and enamels on the color and transparency of decorative, artistic, and technical vitreous coatings on metallic and nonmetallic materials is exemplified by objects created in different historical epochs.