Mixture Of Talc Research Articles

Low temperature preparation and machinability of porous ceramics from talc and foamed glass particles

Porous ceramics were prepared by firing mixtures of talc (Mg 3Si 4O 10(OH) 2) and foamed glass particles (ceramic balloons, CB) with and without LiCl as a sintering acid. The mixing ratios of the starting materials were talc:CB = 7:3, 8:2, 9:1 and 10:0, with additions of LiCl of 0, 2 and 5 mass%. The mixtures were formed into pellets and fired at 600–1000 °C. The pellets without LiCl showed very poor strength even when fired at 1000 °C but those containing LiCl were much stronger, even when fired at only 600 °C. The crystalline phases in these samples changed to enstatite (MgSiO 3) at ≥ 700 °C by decomposition of the talc under the fluxing action of the LiCl. The resulting samples were machinable and easily cut and drilled. The cutting rate decreased with increasing bending strength, for example, from 105 mm 2/s and 6.3 MPa to 50 mm 2/s and 16.3 MPa, respectively. The drilling rate of the present sample was found to be only slightly less than Teflon (polytetrafluoroethylene, PTFE) but much faster than graphite, glass ceramics, etc.

Use of unconventional methods of obtaining cordierite ceramic pigments

The possibility of obtaining cordierite ceramic pigments from mixtures of talc, kaolin, and alumina by boiling and autoclaving is investigated. It is found that autoclave treatment and boiling for the preparation of a charge to be used in obtaining ceramic pigments is desirable and promising, because this method makes it possible to neutralize, to the extent possible, and homogenize the components of the charge. Autoclaving is a more difficult method than boiling and requires a special airtight apparatus - an autoclave, but it yields pigments with more stable and saturated color.

펠렛 피복물질의 물리, 화학적 특성이 당근 펠렛종자의 발아력에 미치는 영향

펠렛의 목적은 기계화 정밀파종하여 파종과 솎음노력을 절감하는데 있다. 펠렛 피복물질의 용적밀도는 dialite, kaolin 및 talc 등이 낮았고 기공성은 높았다 보수력이 우수한 피복물질은 bentonite와 dialite 이었으며, 184% 및 173%의 수분을 보유할 수 있었다. 반면 calcium carbonate, calcium oxide, fly ash등은 보수력이 낮은 펠렛 피복물질이었다. 펠렛 피복물질의 pH는 kaolin과 dialite에서 각각 6.8 및 7.4로 중성이었으나, limestone, calcium oxide, bentonite 등은 pH가 12.8, 13및 10으로 강알카리였다. 전기전도도는 강알카리인 limestone, calcium oxide에서 높았다. 이와 같이 높은 pH와 전기전도도를 보인 피복물질들은 당근종자의 펠렛에 적합하지 않았다. 펠렛 피복물질를 EDS로 분석한 결과, Talc는 주성분이 Si (71%)이었고, Mg도 29% 함유하였다. 반면 calcium carbonate의 주요성분은 Ca (66.6%)이었으며, 이외에 Si (22.9%)와 Mg (10.5%)를 함유하였다. 펠렛 형성정도는 kaoline, talc 및 talc + calcium carbonate 혼합재료에서 우수하였다. 펠렛종자의 경도는 bentonite로 펠렛된 종자에서 가장 높았다. 수분흡수 후 펠렛층의 분해형태는 talc, limestone, zeolite, 및 fly ash는 열개형이었고, 용해형은 calcium carbonate와 calcium oxide등이었다. 반면 bentonite와 vermiculite는 팽창형이었다. 수분흡수 후 펠렛층의 분해는 calcium carbonate 및 kaolin으로 펠렛된 종자에서 분해가 가장 빨랐다. 펠렛배율이 높아지면 발아속도<TEX>$(T_{50})$</TEX>는 지연되었다. 당근종자에서 적정 펠렛배율은 19배가 좋았다. Seed pelleting is generally conducted in order to save the labor for sowing and thinning by enabling the precision mechanical planting. In the present study, the influence of physical and chemical properties of pelleting solid materials was investigated on carrot seed germination. Among the pelleting solid materials evaluated, dialite, kaolin, and talc showed low bulk density and high porosity. Bentonite and dialite carried high water holding capacities of 184% and 173%, respectively, while calcium carbonate, calcium oxide, and fly ash showed relatively low water holding capacity. The pH of kaolin (6.8) and dialite (7.4) were close to neutral, while limestone (12.8), calcium oxide (13.0), and bentonite (10.0) were highly basic. High electro-conductivity was shown in limestone and calcium oxide. EDS analysis revealed that the main elemental compositions of talc were Si (71.0%) and Mg (29.0%), and those of calcium carbonate were Ca (66.6%), Si (22.9%), and Mg (10.5%). High granulation capacity was observed from talc and the mixture of talc and calcium carbonate. Seeds pelleted with bentonite showed the highest hardness. The dissolving type of the pellet layer after imbibition was split type in talc, limestone, zeolite, and fly ash, melt type in calcium carbonate and calcium oxide, and swell type in bentonite and vermiculite. The shortest dissolving time of pellet layer was observed from calcium carbonate and kaolin. The germination speed <TEX>$(T_{50})$</TEX> was delayed as the size of pelleted seeds increased. The optimum size of pelleting was 19 ratio in carrot.

Extrusion Forming of Cordierite Honeycomb with Hexagonal Open Cells

Cordierite honeycomb with hexagonal shaped open channels was formed by extrusion forming technique using specially designed mould for the raw oxide mixture of talc, kaolin, alumina and aluminum hydroxide. The honeycomb showed extremely thin wall thickness of 0.15 mm and low coefficient of thermal expansion (CTE) for the high number of cells per square inch (cpsi) approaching to 600. The extruded honeycomb was sintered at various conditions and characterized by XRF, TGA-DTA, XRD, TMA and SEM techniques. The indialite crystalline showing the coefficient of thermal expansion of 1.9 × 10-6/°C was formed while sintering at 1,450°C for 5 h. The influence of Fe2O3 additive and heating condition on the CTE of cordierite was analyzed in details. This particular cordierite honeycomb with high numbers of hexagonal shaped open cells showed a distinct advantage of saving the amount of precious metal catalyst materials to be coated on the substrate in comparison with the honeycomb with rectangular cells while improving the degree of catalyst efficiency when applying the substrate of automotive catalytic converter.

Effect of water and stress on the lattice-preferred orientation of olivine

The influence of water and stress on the lattice-preferred orientation (LPO) of olivine aggregates was investigated through large strain, shear deformation experiments at high pressures and temperatures ( P = 0.5–2.1 GPa, T = 1470–1570 K) under both water-poor and water-rich conditions. The specimens are hot-pressed synthetic olivine aggregates or single crystals of olivine. Water was supplied to the sample by decomposition of a mixture of talc and brucite. Deformation experiments were conducted up to γ (shear strain) ∼ 6 using the Griggs apparatus where water fugacity was up to ∼ 13 GPa at the pressure of 2 GPa. The water content in olivine saturated with water increases with increasing pressure and the solubility of water in olivine at P = 0.5–2 GPa was ∼ 400–1200 ppm H/Si. Several new types of LPO in olivine are found depending on water content and stress. Samples deformed in water-poor conditions show a conventional LPO of olivine where the olivine [100] axis is subparallel to the shear direction, the (010) plane subparallel to the shear plane (type-A). However, we identified three new types (type-B, C, and E) of LPO of olivine depending on the water content and stress. The type-B LPO of olivine which was found at relatively high stress and/or under moderate to high water content conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (010) plane subparallel to the shear plane. The type-C LPO which was found at low stress and under water-rich conditions is characterized by the olivine [001] axis subparallel to the shear direction, the (100) plane subparallel to the shear plane. The type-E LPO which was found under low stress and moderate water content is characterized by the olivine [100] axis subparallel to the shear direction, the (001) plane subparallel to the shear plane. Observations by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) show that the dislocations in water-poor samples (type-A) are curved and both b = [100] and b = [001] dislocations have a similar population. Numerous subgrains are seen in water-poor samples in backscattered electron images. In contrast, water-rich samples (both type-B and type-C) contain mostly b = [001] dislocations and dislocations are straight and sub-grain boundaries are rare compared to those in water-poor samples. These observations suggest that (1) dominant slip systems in olivine change with water fugacity (and stress) and (2) grain boundary migration is enhanced in the presence of water. Seismic anisotropy corresponding to the fabrics under water-rich condition is significantly different from that under water-poor condition. Consequently, the relationship between seismic anisotropy and flow geometry in water-rich regions is expected to be different from that in water-poor regions in which type-A fabric dominates (i.e., the lithosphere). A few cases are discussed including anisotropy in the subduction zone and in the deep upper mantle.

Numerical investigation of a developmental pneumatically fed impact pulveriser

The current work has been carried out on a pneumatically fed impact pulveriser. A recent build of the proposed device, and early experiments have shown promising size reduction ratios and energy savings in comparison with conventional milling techniques. A number of experiments have shown the points of greatest wear to be on the blades of the rotor and on the walls of the outlet duct. Experimental work was carried out on a single-phase airflow, and a two-phase air–talc mixture. Numerical simulations were performed using the proprietary CFD code FLUENT. Flow predictions of the single and two-phase systems indicated highly turbulent flows and simulations followed the trends indicated by flow visualisation. The authors propose a breakage model for particles.

Non‐Isothermal Crystallization Behavior of Poly(L‐lactic acid) in the Presence of Various Additives

AbstractSummary: The effects of various additives: poly(D‐lactic acid) (PDLA), talc, fullerene C60, montmorillonite, and various polysaccharides, on the non‐isothermal crystallization behavior of poly(L‐lactic acid) (PLLA), during both the heating of melt‐quenched films from room temperature, and the cooling of as‐cast films from the melt, was investigated. When the melt‐quenched PLLA films were heated from room temperature, the overall PLLA crystallization was accelerated upon addition of PDLA or the stereocomplex crystallites formed between PDLA and PLLA, the mixtures containing PDLA, and the mixture of talc and montmorillonite. No significant effects on the overall PLLA crystallization were observed for talc, C60, montmorillonite, and the mixtures containing C60. Such rapid completion of the overall PLLA crystallization upon addition of the aforementioned additives can be ascribed to the increased density (number per unit volume or area) of PLLA spherulites. When the as‐cast PLLA films were cooled from the melt, the overall PLLA crystallization completed rapidly, upon addition of PDLA, talc, C60, montmorillonite, and their mixtures. Such rapid overall PLLA crystallization is attributable to the increased density of the PLLA spherulites and the higher nucleation temperature for PLLA crystallization. In contrast, the addition of various polysaccharides has no significant effect, or only a very small effect, on the overall PLLA crystallization during heating from room temperature or during cooling from the melt. This finding means that the polysaccharides can be utilized as low‐cost fillers for PLLA‐based materials, without disturbing the crystallization of the PLLA. The effect of additives in accelerating the overall PLLA crystallization during cooling from the melt, decreased in the following order: PDLA &gt; talc &gt; C60 &gt; montmorillonite &gt; polysaccharides.Polarization optical photomicrographs of pure PLLA, and the PLLA‐F film, with the fullerene additive, during cooling from the melt (Process IIB). Both of the photomicrographs were taken at 120 °C.magnified imagePolarization optical photomicrographs of pure PLLA, and the PLLA‐F film, with the fullerene additive, during cooling from the melt (Process IIB). Both of the photomicrographs were taken at 120 °C.

Effects of filler treatments on the mechanical, flow, thermal, and morphological properties of talc and calcium carbonate filled polypropylene hybrid composites

AbstractCommercially available neoalkoxy titanate (Lica 12) and organosilane (3‐aminopropyltriethoxysilane) coupling agents were used to treat talc and calcium carbonate (CaCO3) to compare their effects with those of untreated fillers upon their incorporation into polypropylene (PP). Commercial stearic acid treated CaCO3 was also used to widen the scope of the study. Single‐filler PP composites (containing either talc or CaCO3) and hybrid‐filler composites (containing a mixture of talc and CaCO3) were compounded on a twin‐screw extruder and subsequently injection‐molded into dumbbells. The silane and titanate treatments dramatically increased the elongation at break for both the single‐filler and hybrid‐filler composites, whereas stearic acid did not. There was also a moderate improvement in the impact strength of the composites, particularly those treated with Lica 12. The hybrid composites, through the synergistic coalescence of positive characteristics from talc and CaCO3, had exceptionally good impact properties, more so with the aid of the coupling agents. For example, the impact strength value of a Lica 12 treated hybrid composite was the greatest for all the composites studied, overshadowing the superiority of the CaCO3‐filled PP composites, which predominantly had the highest impact properties. Further investigations of the thermal and morphological properties were also conducted to facilitate the determination of the coupling mechanisms and their interesting effects on the hybrid composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 413–426, 2005

Flotation and entrainment behavior of minerals in talc‐calcite separation

The main aim of a flotation process is to recover the valuable part of the ore with minimum gangue contamination by different mechanisms, such as entrainment. In this study, the flotation rate and recovery of talc and entrainment of fine calcite particles were investigated using individual minerals and a mixture of talc and calcite. The effects of various frothers were tested. The results indicated that the type of frother had significant effects on the recovery, flotation rate and fine gangue entrainment. The addition of kerosene as a collector enhanced selectivity between talc and calcite without any reduction in talc recovery. This was attributed to increasing the rate constant of talc upon kerosene addition without any increase in the calcite fines recovery.

Effect of addition of talc on the sintering characteristics of fly ash based ceramic tiles

The sintering characteristics of fly ash–talc mixtures having 0–100% talc (w/w) in the presence of 10% (w/w) sodium hexa meta phosphate (SHMP) have been studied. In the fly ash rich mixtures, the presence of needle shaped mullite and rhombohedral aluminum phosphate phases is responsible for providing impact strength to sintered tile bodies. On gradual addition of talc, the decrease in the concentration of sillimanite and increase in the concentration of sodium magnesium phosphate crystals is responsible for the observed improvement in the impact strength of tiles. With increase in talc content, initially the % water absorption decreases to reach a minimum for a fly ash–talc mix containing 60% (w/w talc) where after it again starts increasing. The apparent density of the tile samples increases with increasing talc content in the raw mix due to densification as well as higher density of talc as compared to fly ash.

Characterization of talc/calcium carbonate filled polypropylene hybrid composites weathered in a natural environment

Two kinds of composites, namely single-filler polypropylene (PP) composites (containing either talc or calcium carbonate) and hybrid-filler PP composites (consist of a mixture of talc and calcium carbonate) were injection moulded into dumbbells. These specimens were subjected to natural weathering i.e. tropical climate in Penang, Malaysia for 6 months. After 6 months of exposure, the mechanical properties of single-filler PP composites deteriorated due to severe physical and chemical degradation. However, the hybrid-filler PP composites were found to show better retention in mechanical properties albeit having undergone some degree of surface-degradation as well. It is believed that the ‘hybridization’ effect has successfully increased the resistance of the hybrid composite to severe environmental degradation to the extent that it protects the internal structure of the composite from environmental damage, even though the surface of the composite gets severely degraded. Surface treatment of fillers was also found to be able to aid in the retention of the composites’ mechanical properties.

Synthesis of Na-2-mica from talc and kaolinite: characterization and Sr2+ uptake

Na-2-mica, a highly charged sodium fluorophlogopite mica of ideal composition, Na2Mg6Si6Al2O20F4·xH2O was synthesized from a mixture of talc, kaolinite, ultrafine magnesium oxide or magnesium nitrate, and sodium fluoride at a temperature of 825 °C for 12 h. The resulting powders were characterized by X-ray diffraction (XRD), 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR), and scanning electron microscopy (SEM). Both magnesium sources resulted in the formation of highly charged expandable mica; however, the sample prepared with magnesium nitrate also contained forsterite as an impurity. The presence of forsterite in the sample was confirmed by a strong resonance at −62 ppm relative to the tetramethylsilane reference. Each mica had four distinctly non-equivalent Si environments. The 27Al MAS-NMR spectra indicated that all Al in the samples was tetrahedrally coordinated. Use of magnesium nitrate as a magnesium source rather than magnesium oxide resulted in slightly smaller particles; however, both sources resulted in mica flakes less than 2 µm. The cation exchange capacity (CEC) of the mica prepared from MgO was close to the theoretical value for Na-2-mica (247 meq 100 g−1); however, the CEC of the sample prepared from magnesium nitrate was much larger than expected. Part of the layer charge for these samples was the result of cation vacancies in the octahedral sheet of the mica as indicated by a Li-migration technique. Ion exchange studies indicated that both micas were highly selective for strontium, whose radioisotope Sr-90 is commonly present in nuclear waste.

Synthesis of Mg-α SiAlON powders from talc and halloysite clay minerals

Carbothermal reduction and nitridation (CRN) of SiO2 is an attractive method to manufacture Si3N4 powders with controlled grain morphology. Some inexpensive raw materials were previously used to synthesize β-sialon powder, resulting in cheaper products to be useful for some engineering applications. In this work, Mg-α sialon (MgxSi12−m−nAlm+nOnN16−n) powders were achieved by CRN of mixtures of talc (Mg3(Si2O5)2(OH)2) and NZ halloysite clay (Al2Si2O5(OH)4) minerals. The final products consisted mainly of α-sialon and β-sialon phases. Small amounts of 15R AlN-polytypoid and SiC were also identified in the synthesized powder. By adding a small amount of α-Si3N4 powder as seeds to the starting composition, the conversion rate of α-sialon phase was significantly enhanced and powders with up to 90 wt% of α-sialon were produced.

フォルステライトの生成に及ぼす粉砕雰囲気の影響

Grinding a powder mixture of talc and MgCO3 was conducted under dry (in air) and wet (with water) conditions to investigate the effects of these conditions on the formation of forsterite in sintered bodies from the ground products.Dry grinding caused size reduction in the initial stage, followed by the aggregation of fine particles due to mechanical activation. This operation produced homogeneous mixture with structural change into amorphous state. The homogeneous mixture leads to acceleration of solid state reaction on its firing. On the contrary, wet grinding reduced the particle size in the mixture, but the crystal structure was maintained even in a prolonged grinding period. This is the main reason that different phases of forsterite are formed in the sintered bodies. Consequently, dry grinding is more advantageous than wet grinding in terms of forsterite formation in a body sintered at relative low temperatures.

Pigment dispersion degree and its evolution in storage

The current size of individual particles in most pigments is usually below 1μm; this ensures powerful forces of attraction causing the particles to cling to one another forming aggregates. If pigment dispersion stability is not appropriate, particles join again and form flocculates. It is important to know the initial degree of dispersion, its evolution during coating storage and the influence on its dry film anticorrosive properties. Several anticorrosive coatings were formulated starting from an epoxy resin as binder, tin tannates as inhibitor and a red iron oxide‐micronised talc mixture as inert pigment. Variables studied were pigment dispersion time and coating ageing time in storage. The degree of dispersion was determined by optical photomicroscopy to establish the shape and size of associated particles present in the system. The flow properties of anticorrosive coatings due to the different dispersion degree were evaluated through rheological tests. Coating film behaviour was also assessed for several dispersion times and ageing periods in laboratory, employing a salt spray (fog) cabinet and a 100 per cent relative humidity chamber.

Formation of Expandable Mica from Talc Using the Intercalation Procedure

To investigate the transformation process from talc to expandable micas, mixtures of talc and Na2SiF6 were heated from 600° to 900°C and air‐quenched at 50°C intervals. The air‐quenched product at 800°C mainly consisted of expandable micas with a basal spacing of 1.25 nm, nonexpandable materials with a basal spacing of 0.96 nm, and a small amount of talc used as the starting material. A lattice fringe image by HRTEM of the product shows that the layer spacing at the edges surfaces is about 1.2 nm, but the layer spacing inside of the particles is close to that of talc. Such a nanostructure indicates a topotactic reaction from talc to expandable micas and confirms that Na+ ions intercalate into the structure from the edge to the core.

Improving settling dynamics of activated sludge by adding fine talc powder

The effect of adding varying mixtures of talc and chlorite powder to activated sludge in order to improve the settling characteristic has been studied. The powder is found to improve the settling velocity of the sludge, strictly by increasing the average density of the sludge floc aggregate. The settling velocity was measured with a recirculated settling column under different concentrations and turbulence levels. Numerical simulation of a secondary settling tank indicates that adding fine powder will improve the overall performance considerably.

Improving settling dynamics of activated sludge by adding fine talc powder

The effect of adding varying mixtures of talc and chlorite powder to activated sludge in order to improve the settling characteristic has been studied. The powder is found to improve the settling velocity of the sludge, strictly by increasing the average density of the sludge floc aggregate. The settling velocity was measured with a recirculated settling column under different concentrations and turbulence levels.Numerical simulation of a secondary settling tank indicates that adding fine powder will improve the overall performance considerably.

Novel Approach to Estimate Quality of Binary Random Powder Mixtures: Samples of Constant Volume. I: Derivation of Equation

AbstractAn equation of the quality of binary random mixtures that applies to powder samples of constant bulk volume was derived from the binomial distribution. In contrast to the Stange–Poole equation for samples of constant mass, this approach can also be used for constituents with large differences in particle size and in bulk density. The validity of this equation was verified with tablets directly compressed from mixtures composed of equal mass proportions of sucrose [volume‐weighted/volume‐number mean diameter (d v), 504 μm] as the coarse ingredient (A) and of a microcrystalline cellulose (Avicel PH 101)‐talc mixture (d v, 60 μm) as the fine constituent (B). Because of the difference in the bulk densities of A and B, the equation estimated a coefficient of the random content variation, which for A was double that for B. The content variations found with the tablets were in excellent agreement with the calculated values and reflected the differences predicted from theory. The Stange–Poole equation yielded identical values of the content variations of A and B, which is in contrast to the experimental results.

PROPAGATING ROSEMARY (ROSEMARINUS OFFICINALIS) BY CUTTINGS

`Arp' rosemary cuttings were treated with indole butyric acid (IBA) using three different application procedures to determine speed and quality of rooted cuttings produced at three weeks under mist. Five concentrations of IBA, 0%, 0.8%, 1.6%, 3.0%, and 4.5%, and three methods of application were compared. Methods of application were 1) cuttings treated with solutions containing IBA, captan, benomyl, and streptomycin applied as a one minute soak or 2) as a post plant drench or 3) cuttings soaked for one minute in a solution of captan, benomyl and streptomycin and then dipped into IBA + talc mixture. After the treatments were applied, the cuttings were placed on a mist bench for three weeks. Visual shoot ratings were made weekly and visual root ratings were made at three and four weeks after treatments were applied. Root dry weights were determined. Results indicated the one minute soak in a captan, benomyl, and streptomycin solution then dipped in 0.8% IBA + talc consistently resulted in a higher quality rooted cutting.