Decrease In Open Porosity Research Articles

Effects of long-term high temperature annealing on Li2TiO3 and advanced core-shell Li2TiO3-Li4SiO4 tritium breeders

The present work investigates the evolution of mechanical performance and provides a comprehensive study of the changes in microstructure, phase, and compositional elements of Li2TiO3 and core-shell Li2TiO3-Li4SiO4 pebbles resulting from annealing at 900 °C in He incl. 0.1 vol % H2 flow atmosphere for specific durations. Compression tests show that long-term annealing improves the mechanical performance of Li2TiO3 instead of degrading it. The mean crush load of Li2TiO3 increases from 41 N to 45 N after 1000 h of annealing. Li2TiO3 pebbles can maintain their microstructure stability, with only limited grain growth and a decrease in open porosity identified. These changes are believed to be responsible for the improvement in mechanical performance after 1000 h. The mechanical performance of core-shell Li2TiO3-Li4SiO4 pebbles primarily degrades during the initial 100 h, with a decrease in mean crush load from 118 N to 91 N. Subsequently, it gradually stabilizes with a mean crush load of 91 N over the remaining annealing period. An increase in open pores and slight Li4SiO4 grain growth was observed after 1000 h of annealing, which is the primary cause of the mechanical performance degradation in core-shell Li2TiO3-Li4SiO4 pebbles. The loss of lithium in core-shell Li2TiO3-Li4SiO4 pebbles is a combined effect of the Li2TiO3 phase and Li4SiO4 phase, with a stronger association to the Li4SiO4 phase.

Development of a loose powder sintering method for the preparation of porous ceramic from municipal solid waste incineration fly ash

Loose powder sintering was used to prepare porous ceramic from municipal solid waste incineration fly ash (MSWI FA) and waste glass (WG). Sintering experiments at various temperatures, holding times, Al2O3 and SiC were conducted to investigate their effect on the ceramic properties and volatile heavy metal removal efficiency. The results show that increasing temperature from 1100 °C to 1250 °C promoted the transition of the mixtures from loose powder to a densified sintered matrix, with a bulk density increase of 31.10% and an open porosity decrease of 70.41%. The bulk density of the ceramic increased to 2.44 g/cm3 with 3% Al2O3 addition. The removal rates of Pb, Zn, Cu and Cd were higher than 90% at 1200 °C for 90 min, and promoted by the increasing temperature and holding time. Notably, 3% Al2O3 addition inhibited the volatilisation of Zn, Cu and Cd, particularly for Zn, the removal rate of which reduced to 61.66% at 1200 °C. The bulk density of the ceramic decreased to a minimum value of 1.48 g/cm3 with 4% SiC. The ratio of MSWI FA:WG:Al2O3:borax of 28.3:56.7:10:5 was proposed to obtain ceramic with a bulk density of 1.54 g/cm3 and a water absorption rate of 8.59% at 1150 °C. The leaching concentration of the porous ceramic met the Chinese regulatory standard (GB 8978-1996). Preparation of MSWI FA-based porous ceramics using the powder sintering method is a promising route for the harmless utilisation of MSWI FA. The porous ceramic is potentially applicable as a thermal-insulation building material.

Consolidating Efficiency of Nanolime Product CaLoSiL on Porous Limestone

The effects of the double and the multiple application (2 to 6) of Calosil® (IBZ-Salzchemie GmbH, Halsbruecke, Germany) E25, IP 25 and E50 products were studied on Maastricht limestone, which is characterized by high porosity and large pores. Both destructive and non-destructive laboratory tests we performed in order to assess the consolidating efficiency of the nanolimes—the bending and compressive strengths, ultrasound velocity measurement, porosity determination and SEM examination. Except for the compressive strength, the other characteristics were investigated in the depth profile of stone specimens to find the distribution of the treatment product within the substrate. The performed tests showed good penetration of CaLoSiL nanolime products into the studied limestone. The bending strengths of limestone samples after double treatment using nanolime E 25, IP25 and E 50 were found to be increased by 50%, 44% and 89%, respectively, whereas the compressive strength increased by 50%, 23% and 73%. The porosity of the stone was reduced by the treatment, but only slightly, to an acceptable extent. The higher sum of performed nanolime applications resulted in a higher strengthening effect but at the same time at the uneven distribution of the product in the stone specimen, which was followed by an increase in the strength and decrease of open porosity in the surface part. SEM examination showed a modification of the stone microstructure by the added binder.

Pore structure and surface property design of silicon carbide membrane for water-in-oil emulsification

In recent years, ceramic membranes have been applied as emulsification media in preparing emulsified heavy oils for residue fluid catalytic cracking units. In this case, silicon carbide (SiC) material is used for harsh environments due to its excellent chemical and thermal stabilities. Herein, a superhydrophobic SiC emulsified functional membrane was prepared by using an in-situ sintering method and subsequent grafting modification. The open porosity of these prepared membranes can be controlled from 26% to 48%, and the water contact angle of the membranes under oil was approximately 170°. The decrease of open porosity improved the bending strength of the membranes and also affected the emulsification performance. The size of water droplets decreased from 1.16 μm to 0.98 μm as the open porosity decreased from 48% to 26%. Moreover, the SiC membranes exhibited high flux and stability during the preparation of water-in-oil (W/O) emulsions, and the fouled membranes can be conveniently and effectively regenerated by ultrasonic cleaning with ethanol. Hence, the SiC membranes produced W/O emulsions with small droplets in harsh environments, such as the emulsification of heavy oil and high-viscosity oil at high temperature. • Pore structure and surface property of SiC membranes were successfully tailored. • High bending strength and excellent underwater superhydrophobicity were achieved. • Open porosity was revealed to dominate the membrane emulsification performance. • SiC membranes showed high flux and stability in preparing water-in-oil emulsions. • SiC membranes can be effectively regenerated by ultrasonically cleaning in ethanol.

Experimental Investigation on the Influencing Factors of Compressive Strength of Foamed Lightweight Material Utilizing Completely Decomposed Granite.

The utilization of construction waste soil to produce foamed concrete together with cement and a foaming agent is a promising method for waste recycling. Completely decomposed granite (CDG), which is widely available in southern China, was selected as a typical construction waste soil in foamed material production. The Taguchi method was applied to study the influence of various parameters on compressive strength, including cement dosage, CDG dosage, water to solid materials ratio (W/M), fine particles content, and gravel particles content. Analysis of variance (ANOVA) on a CDG-based sample showed that all factors have significant effects on compressive strength and the most effective parameter was cement dosage, followed in sequence by CDG dosage, W/M, gravel particles content, and fine particles content. However, only cement dosage and W/M influence the internal structure significantly during water/vacuum-immersion tests. The relationship between micro-pore structure and compressive strength suggested that with the decrease of open porosity, the compressive strength showed an increasing trend. This study reveals the possibility of CDG as a raw material for foamed lightweight soil and provides a technical reference of production procedure.

Effect of surface hydrophobisation on the properties of a microporous phenylene-bridged organosilicate film

This study aims hydrophobisation of a microporous phenylene-bridged organosilicate film via its surface modification with hexamethyldisilazane (HMDS) vapour to adapt it for use as a low dielectric constant material for advanced microelectronics technology. The microporous organosilicate film was spin-coated with 1,4-bis (triethoxysilyl) benzene, followed by soft baking at 120–200 °C and annealing at 390 °C in N2. Subtractive porosity was added using a sacrificial template — Brij® L4. This 1,4-phenylene-bridged film possessed a large Young's modulus and small pore size. However, due to steric effects during the film formation, a large amount of unreacted silanol remained on the surface. The HMDS-induced hydrophobisation reduced the number of residual silanols and adsorbed water molecules, despite the small pore size. A decrease in the hydrophilicity of the film surface led to an increase in the WCA value as well as a decrease in the dielectric constant and dielectric loss tangent. Ellipsometric porosimetry showed that the open porosity decreased without changes in the pore size distribution as a result of silylation by the HMDS vapour. However, the Fourier transform infrared spectra showed limited time-dependant temperature stability of the –CH3 groups introduced by the HMDS vapour treatment. The decrease in open porosity during the heat treatment of the hydrophobised film was significantly reduced because of the strengthening of the pore walls. Consequently, this film demonstrated lower shrinkage and larger Young's modulus.

Influence of Firing Temperature on Phase Composition and Color Properties of Ceramic Tile Bodies.

This study is focused on the behavior of the cream-firing clays from Opoczno region (Poland). The ceramic masses on which tests were carried out consisted of cream-firingBorkowice clay and dolomite in two different grain sizes as an additive that changes the color of ceramic materials. Test samples were prepared by plastic method and fired at range of 1100–1240 °C. Phase composition of theinvestigated materials was characterized by XRD method with quantitive analysis of the amorphous phase determined by the Retvield technique. Color properties of the surface of the obtained ceramic materials were determined in CIE-Lab color space. The phase composition of the obtained ceramics depends on the firing temperature. The color of the surface of the ceramic materials also depends on the firing temperature. There was a tendency to decrease the brightness, decrease the blue shade, and increase the yellow shade of the surface of materials with increasing the temperature. The conducted tests allowed to conclude that the color of ceramic materials depends on their phase composition. The most important role in the formation of color correspond to the amorphous phase, formed during the process. The lower content of the amorphous phase in the material allows to obtain brighter products with a lower proportion of yellow, and therefore closer to white. Moreover, following tests were carried out: total water absorption, total open porosity, linear shrinkage, and flexural strength. With increasing the temperature, total water absorption and total open porosity decrease, and total linear shrinkage increases due to the progressive sintering process. Flexural strength increases with the increase of the firing temperature for materials consisting of Borkowice clay. The addition of dolomite introduced new pores into the material, which resulted in an increase in flexural strength at lower firing temperatures and a decrease in flexural strength at higher firing temperatures.

Microstructure and Porosity Evolution During the Reduction, Softening and Melting of Iron-Bearing Materials

The performance of the blast furnace is strongly affected by the position and thickness of the cohesive zone, which is largely influenced by the high-temperature properties of the iron-bearing materials. During its reduction, softening and melting, ferrous materials undergo major microstructure changes and its understanding is essential to develop new raw-materials, technologies, and models. In this study, the behavior of reduction, softening and melting of a lump ore, an acid pellet, and a sinter was characterized by softening and melting (S&M) experiments. After that, to access the samples’ structural transformations, interrupted S&M tests were carried out up to four different conditions based on contraction and pressure loss levels. The obtained products were characterized according to its density (true and apparent), porosity (open, closed and total), phase composition by X-ray diffraction and microstructure (reflected light microscopy and electron scanning microscopy). From the S&M test results, three main regions of reduction were characterized, namely: solid/gas reduction, reduction retardation, and melting reduction. In the solid/gas reduction, samples open porosity increased, with reduction following the shrinking core model. On the region of reduction retardation, a sharp decrease in open porosity was identified together with the diminishing of the reduction rate, which occurred due to the iron shell porosity being clogged due to the slag transfer from the particles’ cores to its periphery. At the melting exudation region, reduction retardation ceased and exudation of the ferrous slag lead to a peak of reduction. The lower the reduction degree of the samples at this stage, the higher the consumption of carbon. Furthermore, at 10 pct contraction, a pseudo-globular wustite structure interspersed with slag was observed for the pellet and sinter cores. At 50 pct contraction, the previous structure coalesced to form a globular shape wustite in a well-connected slag matrix.

Geohistorical analysis of the northern part of the Pai-Khoi carbonate parautochthone in Late Devonian–Carboniferous

Research subject. This article focuses on the geological structure of the northern part of the Pai-Khoi carbonate parautochthone.Materials and methods. The study was based on the data obtained on the key sections of the North-Western Pai-Khoi. Research methods included lithological and facies analysis, subsidence curves, reconstruction of the thermal maturity of deposits based on conodont alteration indexes, X-ray microtomography for determining porosity values.Results. The Upper Devonian–Carboniferous succession (ca. 900 m thick) is composed of the terrigenous and carbonate Pyrkov Fm. (Frasnian), carbonate Lymbadyakha Fm. (Famennian-Tournaisian), Bolvanskii Fm. (Visean-Bashkirian), and Hoiponganase Fm. and Reef Chaika (Moskovian-Kasimovian). The early Frasnian part of the succession was deposited in a shallow-water environment. In the Middle–Late Frasnian, the Korotaikha paleodepression and an isolated carbonate platform was formed on the shelf edge. Filling of the paleodepression was completed at the end of the Early Visean. In the Late Visean–Late Carboniferous, a carbonate platform (ramp) formed. A Middle Paleozoic paleogeothermal gradient reconstructed on the basis of conodont alteration indexes is much higher in the Pai-Khoi carbonate parautochthone than in the most of Pechora Plate regions. This is likely to have been caused by the tectonic activity of the plate border in the Late Carboniferous–Mesozoic. A downward decrease in open porosity (from 6% to 0.1%) is likely to have been associated with increased compaction and recrystallization of the carbonates.Conclusions. Famennian-Tournaisian carbonate formations of the Pai-Khoi carbonate parautochthone were deposited under the conditions of isolated platform environment; however, the Visean–Late Carboniferous deposits were formed in the outer ramp environment. The Late Devonian–Middle Carboniferous carbonate deposits of the Pai-Khoi parautochthone demonstrate an extremely low open porosity and a high thermal maturity. These properties, along with the pronounced faulting and folding of the rocks, significantly decrease petroleum-bearing prospects of these deposits.

Compostable, fully biobased foams using PLA and micro cellulose for zero energy buildings

Ecological, health and environmental concerns are driving the need for bio-resourced foams for the building industry. In this paper, we examine foams made from polylactic acid (PLA) and micro cellulose fibrils (MCF). To ensure no volatile organic compounds in the foam, supercritical CO2 (sc-CO2) physical foaming of melt mixed systems was conducted. Mechanical and thermal conductivity properties were determined and applied to a net zero energy model house. The results showed that MCF had a concentration dependent impact on the foams. First structurally, the presence of MCF led to an initial increase followed by a decrease of open porosity, higher bulk density, lower expansion ratios and cell size. Differential Scanning Calorimetry and Scanning Electron Microscopy revealed that MCF decreased the glass transition of PLA allowing for a decrease in cell wall thickness when MCF was added. The mechanical performance initially increased with MCF and then decreased. This trend was mimicked by thermal insulation which initially improved. Biodegradation tests showed that the presence of cellulose in PLA improved the compostability of the foams. A maximum comparative mineralization of 95% was obtained for the PLA foam with 3 wt.% MCF when expressed as a fractional percentage of the pure cellulose reference. Energy simulations run on a model house showed that relative to an insulation of polyurethane, the bio-resourced foams led to no more than a 12% increase in heating and cooling. The energy efficiency of the foams was best at low MCF fractions.

Sewage sludge ash as resource for phosphorous and material for clay brick manufacturing

Sewage sludge ash (SSA) contains the critical raw material phosphorous. International research shows that SSA may be utilized as a secondary resource in concrete, bricks or lightweight aggregates, but the high phosphorous content calls on recovery before such use. In the present investigation, phosphorous was recovered from SSA by electrodialytic separation (EDS), and the treated ash (SSA-EDS) was tested as partial clay substitute in brick manufacturing. The experimental work was made with fired brick discs of 2 cm in diameter. For comparison, similar tests were conducted with SSA-EDS and untreated SSA. During EDS, 84–91% phosphorous was recovered. The pH of the SSA was reduced from 10.2 to 3.7 during EDS, while the content of iron oxides increased. The brickwork clay contained about 17% carbonates, a major cause for firing mass loss. The reference brick discs were yellow. As the carbonate content decreased with increasing clay substitution (0–50% per weight), the firing mass loss decreased accordingly. The SSA was reddish due to a high iron oxide content, and the colour of the brick discs turned increasingly reddish with an increasing percentage of SSA and especially SSA-EDS. Thereby it may act as a colouring agent, to obtain desired red bricks, for which natural clays are becoming scarce. When fired at 1000 °C, all brick discs had apparent densities and open porosities within the accepted range of bricks used in the building industry. SEM micrographs showed that mixes with SSA-EDS fired at 1050 °C contained a glassy phase with isolated spherical pores, which may be related to the high hematite content of SSA-EDS. The formation of the glassy phase resulted in a decrease in open porosity with increasing substitution with SSA-EDS for the discs fired at 1050 °C, which was the reversed order compared to firing at 1000 °C.

Effect of B2O3 Concentration on the Properties of Transparent Magnesium Aluminate Spinel Ceramics

We consider the potential of using boron oxide as a sintering aid for the fabrication of transparent magnesium aluminate spinel (MAS) ceramics and analyze the general tendency in the effect of B2O3 concentration on the average density, open porosity, and optical transmission of MAS ceramics. Boron oxide is shown to have an advantageous effect on the sintering behavior of MAS ceramics: raising its concentration leads to a decrease in open porosity and an increase in the average density of the material.

Moroccan clay deposits: Physico-chemical properties in view of provenance studies on ancient ceramics

Features of clayey raw materials from most important traditional pottery centers in the vicinity of the main medieval sites in Morocco, and their fired products were investigated. Besides clay from the North of Morocco, the used raw material was illitic clays (10–100%) and smectite-rich clays (0–67%) with variable amount of kaolinite, quartz and feldspars. Chlorite was also present in a small amount. The main major oxides were Si2O, Al2O3 and CaO. The fired tests (800–1100 °C) displayed a decrease in open porosity of the sintered clay by raising the temperature, mainly from 1000 °C due to the inception of melting. This change was coupled with the change in mineralogical composition. New crystalline phases as Ca-silicates (diopside and gehlenite), hematite, spinel and mullite occurred during firing process, attesting to the inception of melting and were responsible for porosity reduction.Reference clays for pottery were established based on the clay mineralogy and chemical composition. The present study would help to answer some archeological questions concerning possible sourcing areas for archeological ceramics, to determine techniques for the production of artefacts, and then to interpret cultural influences. Furthermore, the obtained results will support the inception of development of a compositional database for Moroccan pottery.

Effect of high titanium blast furnace slag on preparing foam glass–ceramics for sound absorption

Foam glass–ceramics for sound absorption were fabricated via a single-sintering method with high titanium blast furnace slag (HTBFS) and waste glass as the main materials. This study investigated the effects of HTBFS content on the microstructure and properties of foam glass–ceramics. The results show that the main phases of the sintered samples are diopside, perovskite and augite. With increasing HTBFS content from 38 to 48 wt%, the shape of crystals changes gradually and the crystallinity of the sintered samples decreases firstly and then increases, the bulk density and compressive strength increase, the porosity and open porosity decrease. All sintered samples have good sound absorption and corrosion resistant characteristics. The optimal properties, including the highest noise reduction coefficient (0.41) and a relatively high compressive strength (10.5 MPa) of the sintered samples, are prepared with 46 wt% HTBFS content. This research finds a new purpose of waste slag and expands the application range of foam glass–ceramics for sound absorption, especially sound barrier using in the traffic network because of a relative high impressive strength.

Zonation of deposits of hard coals of different porosity in the Upper Silesian Coal Basin

Abstract The article presents the results of tests of porosity of the Upper-Silesian Coal Basin (USCB) hard coals. The porosity was determined for various lithotypes of hard coal, collected in different areas of the Upper-Silesian Coal Basin. Samples of hard coal were collected in 60 seams of 16 coal mines, from the depth of approximately between 350 and 1200 m. There are also presented differences in values of open porosity of coal depending on the depth of occurrence, as well as chronostratigraphic and tectonic correlation of a seam. Uniaxial compression strength of the tested coals falls in the strength class from very low to very high (from 8.1 to 51.5 MPa), open porosity is 0.68–12.5% and total porosity is 3.29–17.45%. With an increase in depth, in general, open porosity of coals decreases. There is an apparent decrease in open porosity correlated with the age of hard coals. It was observed that the lower and upper limits of open porosity ranges of variability shift towards lower values the older the coals are, from the Łaziskie Beds to the Jaklowieckie Beds. The older the coals the greater the average drop in the share of open porosity in total porosity from 60% for the youngest coals to merely several per cent for the oldest ones. The highest values of total porosity (over 10%) were observed in the youngest coals (Cracow sandstone series and siltstone series). Older coals reached more diversified values of total porosity (3.29–17.45%). Based on the conducted tests, zones correlated with tectonics of the basin and with deposition of lithostratigraphic beds of specific age, where values of porosity of hard coals differ, were determined in the area of the USCB. However, in spite of their correlation to a structural unit, the coals demonstrated a decrease in open porosity with an increase in their geologic age. Thus, there is an apparent influence of the deposition depth of coal within a given structural unit on open porosity following the age of coal, i.e. correlation to an older and older chronostratigraphic unit. Porosity tests of hard coal are published in scientific journals yet, most often, there is no information on the type of porosity. Such detailed characteristics of open porosity for coal of the Upper Silesian Coal Basin, as in the article, have not been prepared yet, making our research novel. Such broad tests of porosity of hard coals, correlated with their strength and referring to the deposition depth of seams as well as a correlation to lithostratigraphic units within individual structural units in the USCB, had not been conducted yet. We believe it is a sufficient argument to start detailed research into the open porosity of hard coals. The results of the tests are important from both the research and practical points of view. Knowledge of coal porosity is indispensable in solving many engineering problems of geological engineering, mining geomechanics and mining e.g.: assessing behaviour of coal when it is mined and processed, assessing the possibility of capturing methane, which makes up over 90% of natural gas, from coal in the areas of methane-rich deposits; the possibility of storing various substances in abandoned hard coal mining areas (e.g. CO2 storage within the structure of coal), assessing risk of occurrence of certain natural hazards resulting from mining deposits (e.g. coal and rocks outburst hazard), as well as assessing the possibility of applying unconventional methods of mining hard coal deposits (e.g. underground coal gasification).

Fiber-reinforced lime-based mortars: Effect of zeolite addition

In a previous paper the authors demonstrated that adding glass fibers to hydraulic lime-based mortars leads to clear improvement in the post-cracking behavior. In order to enhance physical and mechanical performances of the above fiber reinforced mortars, the use of zeolitic addition was proposed. A phillipsite-rich tuff and a zeolite A [LTA] were selected and added in the mixtures. A significant decrease in open porosity and increase in mechanical behavior was achieved with each addition. In particular 20% of LTA produces an improvement of flexural and compressive strength up to 150% compared with fiber reinforced mortars without addition.

Development and Characterization of Continuous SiC Fiber‐Reinforced HfB2‐Based UHTC Matrix Composites Using Polymer Impregnation and Slurry Infiltration Techniques

This paper discusses the development of continuous SiC fiber‐reinforced HfB2‐SiC composite laminates. A range of techniques, based on resin‐based precursors and slurries, for infiltrating porous SiC preforms with HfB2 powder were developed. While resin‐based precursors proved to be ineffective due to low HfB2 yield and poor adhesion, the slurry infiltration techniques were effective to varying degrees. The greatest pore filling and composite densities were achieved using pressure and vibration‐assisted pressure infiltration techniques. SiCf/HfB2‐SiC laminates were subsequently developed via lamination, cure and pyrolysis of fabrics using a HfB2‐loaded polymeric SiC precursor, followed by HfB2 slurry infiltration and preceramic polymer infiltration and pyrolysis (PIP). Repeated PIP processing, for 6–10 cycles, resulted in density increases, from the 3.03–3.22 g/cm3 range after HfB2 slurry infiltration, to 3.97–4.03 g/cm3 after PIP processing. Correspondingly, there was a decrease in open porosity from approximately 52% to less than 11%. The matrix consisted of discreet, lightly sintered HfB2 particles dispersed in SiC. The PIP SiC matrix was primarily nanocrystalline after 1300°C pyrolysis, but experienced grain growth with further heat treatment at 1600°C.

Alkali silicate binders: effect of SiO2/Na2O ratio and alkali metal ion type on the structure and mechanical properties

The influence of SiO2:Na2O molar ratio and the nature of an alkali metal (Na vs. K) in commercial aqueous alkali silicate on the microstructure, textural properties, phase composition, and hydrolytic stability of an alkali silicate binder have been investigated using scanning electron microscopy, nitrogen adsorption/desorption technique, X-ray diffractometry, thermal analysis, and dissolution tests. It has been found that microstructure and textural properties of the alkali silicate binder depend both on silica to alkali molar ratio and type of alkali metal (Na vs. K). Sodium silicate binder obtained from commercial silicate solution with lower SiO2:Na2O molar ratio (2.2) exhibits a globular microstructure of silica xerogel with high content of micropores, whereas the binder formulated with SiO2:Na2O molar ratio 3.2 is characterized by more open cluster structure with lower content of micropores. It is observed that surface specific area estimated by Brunauer, Emmett, and Teller method and mesopore volume obtained by the Barrett–Joyner–Halenda method for sodium silicate binder are substantially higher than those for potassium silicate binder. The ultimate hydrolytic stability of the sodium silicate binder increases slightly with increase in the silica to alkali molar ratio within the studied range. Decreasing in SiO2:Na2O molar ratio and replacement of sodium silicate solution by potassium silicate solution in the corresponding filled composition lead to the improvement of mechanical properties and decrease in open porosity.

Effect of Austempering Conditions on the Microstructure and Tensile Properties of Low Alloyed Sintered Steel

Because of the combination of strength and toughness, much interest has been focused on austempered sintered low-alloyed steels. Implementation of this treatment for powder metal components has been limited by interaction between the open porosity of the material and the cooling fluid. This work discusses the influence of different austempering environments and parameters on the microstructure and, as a consequence, on the final properties. The sintered steels selected are based on two different prealloyed powders, Fe-1.5Cr-0.2Mo and Fe-1.5Mo, with the addition of 0.6 wt pct graphite. Green samples with medium density (7.3 g/cm3) were sintered at 1393 and 1523 K (1120 and 1250 °C) to ensure a decrease in open porosity. The austempering treatment process requires austenitizing at 1133 K (860 °C) for 2 hours followed by quenching in different baths at 563 K (290 °C). The final strength and ductility are dependent upon the relative amounts of ferrite, pearlite, and bainite phases present in the austempered steel. Discussion of the experimental results compares the as-sintered and the austempered observations as well as the relationship between mechanical properties and the phases present in the final microstructures.

Structure and basic properties of woodceramics made from phenolic resin–basswood powder composite

Abstract A new woodceramics was developed by carbonizing phenolic resin–basswood powder composite under vacuum. Structural characterization of woodceramics was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. The pyrolytic behaviors of basswood powder and phenolic resin were studied by thermogravimetric analysis (TGA). The effects of carbonization temperature and weight ratio of phenolic resin to basswood powder on the volume electrical resistivity, open porosity and bending strength of woodceramics were also investigated. Experimental results show that woodceramics has a topologically uniform interconnected porous network microstructure, and is typical non-graphitizable carbon containing CC bonds, COC bonds and CH structure. With increasing carbonization temperature, the (0 0 2) peak becomes stronger, the (0 0 2) interplanar spacing and volume electrical resistivity decrease, and the dimensions of carbonized wood powder decrease, while the space between carbonized basswood powders and the open porosity and bending strength of woodceramics increase. The increasing weight ratio of phenolic resin to basswood powder improves the forming ability of phenolic resin impregnated wood powders, and results in a more uniform microstructure, but there is a slight effect on the XRD pattern of woodceramics. The volume electrical resistivity and open porosity decrease, and the bending strength increases as the weight ratio of phenolic resin to wood powder increases.