Preparation of Periclase-forsterite Lightweight Heat-insulating Refractories by Molten Salt Method

Low grade magnesite is one of the main research directions in the future as the raw material for the preparation of magnesia based insulating refractories.Periclase-forsterite(MgO-Mg_(2)SiO_(4)) lightweight insulating refractories were prepared by the molten salt method with high silica magnesite and tertiary talc ore as raw materials by pretreating them to get light burnt magnesia and talc,and NaCl molten salt as the reaction medium.The effects of the NaCl addition,the sintering temperature,the holding time and the raw material ratio on the sample preparation were studied.The results show that when the NaCl addition is 20% of the mass of light burnt magnesia and talc mixture,the sintering temperature is 1 200 ℃,the holding time is 6 h,and m(light burnt magnesia):m(talc)=5:5,the sample has the optimal comprehensive properties:the bulk density of 1.46 g·cm^(-3) and the apparent porosity of 55.0%.In addition,it is found that self-decomposition of talc and the formation of forsterite can form pores inside the sample.

自锁模飞秒Cr^(4+) :forsterite激光器(英文)

飞秒Cr4+ :forsterite激光器可工作在 1 1 8～ 1 30 6 μm区域 ,广泛应用于光通信、生物医学和激光光谱学等领域 .本文介绍了四镜折叠腔的设计、像散补偿以及自锁模的实现 ,报道了自锁模飞秒Cr4+ :forsterite激光器的运转特性 .在吸收泵浦功率 8 0 4W时 ,获得了 36fs、 2 80mW的功率输出 ,中心波长 1 2 46nm .

First-principles investigation of the concentration effect on equilibrium fractionation of Ca isotopes in forsterite

Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64<Ca/(Ca+Mg)<2/16.As a consequence,the 10^3lna between forsterite and other minerals also strongly depend on the Ca content in forsterite.Combining previous studies with our results,the heavier Ca isotopes enrichment sequence in minerals is:forsterite[orthopyroxene[clinopyroxene[calcite & diopside[dolomite[aragonite.Olivineand pyroxenes are enriched in heavier Ca isotope compared to carbonates.The 10^3lna between forsterite with a Ca/(Ca+Mg)of 1/64 and clinopyroxene(Ca/Mg=1/1,i.e.,diopside)is up to^0.64%at 1200 K.The large 103lnaFodiopsiderelative to the current analytical precision for Ca isotope measurements suggests that the dependence of10^3 lnaFo-diopsideon temperature can be used as a thermometer,similar to the one based on the 103lna of 44 Ca/40 Ca between orthopyroxene and diopside.These two Ca isotope thermometers both have a precision approximate to that of elemental thermometers and provide independent constraints on temperature.

Preparation and Application of Light-weight Raw Materials Using Natural Forsterite

In order to develop new basic light-weight refractory raw materials,natural forsterite(<0.045 mm)and magnesite(<0.045 mm)were batched according to the chemical composition of forsterite(2MgO·SiO_(2)),wet milled,semi-dry molded and calcined at different temperatures.Then cylinder samples with diameter of 36 mm were prepared.The effects of the wet milling jar rotation speed,the calcination temperature and the anthracite addition on the properties of the samples were researched.The results show that:when the calcination temperature exceeds 1300℃,all the mineral phases have converted to the desired phases;with the increase of the rotation speed and the calcination temperature,the bulk density of the samples increases,the apparent porosity decreases and the compressive strength improves.By comprehensive consideration,400 r·min^(-1) and 1450℃ are taken as the optimal scheme.High addition of anthracite makes the samples light,so series of light-weight raw materials with uniformly distributed micro-pores can be gained.The light-weight raw materials achieved were used for insulation refractory castables,obtaining good application.

Synthesis of Lightweight Spherical Forsterite Aggregates and Research on Their Application in Mgo Based Castables

Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightweight spherical forsterite aggregates. The mixture was granulated on a disc pelletizer and then calcined at 1 400 ℃ for 3h. The synthesized spherical forsterite aggregates were added in Mg O based castables with MgO-SiO2-H2O binding system to replace equaldensity high purity common forsterite aggregates. Effect of spherical forsterite aggregates addition on properties of MgO based castables was investigated. The results show that: compared with common aggregates,lightweight spherical forsterite aggregates can improve castables ’flow ability and decrease water addition; addition of spherical aggregates has little effect on cold strength of castables; with the increase of spherical aggregate addition,shrinkage of specimens after drying and heating at intermediate temperatures decreases,but the expansion of specimens after heating at high temperatures increases,bulk density decreases and apparent porosity increases,and thermal conductivity declines.

Effects of Lizardite Addition on Technological Properties of Forsterite- monticellite Rich Ceramics Prepared from Natural Magnesite and Dolomite

Lizardite rich peridotite has never been used to prepare ceramic specimens,especially in Morocco.For this raison,potential use of naturally abundant lizarditic material from the Rif domain,as a supply for ceramic industry,has been evaluated.The effects of lizardite addition to magnesite and dolomite mixtures on the thermomechanical properties of the calcined ceramics were also detailed.To achieve this target,natural lizardite,magnesite and dolomite samples were collected in ultrabasic Beni Bousra massif.Those raw samples were used for the synthesis of a forsterite-monticellite rich ceramics.Both raw and sintered samples were characterized by x-ray diffraction,scanning electron microscope and fourier transform infrared.The obtained results showed that both magnesite and dolomite were mainly composed of MgCO_(3) and CaCO_(3).In contrast,lizardite sample showed high amounts of SiO_(2),MgO and Fe2O_(3).An increased amount of lizardite in the initial mixtures enhanced mechanical and dimensional properties of the prepared ceramic specimens,and subsequently,the production of ceramics with the required technological properties.Thus,the preparation of Moroccan lizardite-based ceramics is technically feasible,economically justifiable and socially desirable due to the contribution to the economic growth of the raw materials sector,especially ceramic industry.

Pure forsterite in Nyiragongo lavas: evidence for subsolidus oxidation of volcanic rocks

Some volcanic rocks from Nyiragongo volcano in the Democratic Republic of Congo contain highly oxidized olivine crystals.These olivines crystals are made of two phases,dark olivine on backscattered electron images of pure forsterite composition and grey Mg-poor areas made of olivine and iron-rich oxides.Calculation of the initial composition confirms that they are primary olivine with late separation of two different olivine compositions.Pure forsterite is enriched in SiO_(2) but contains lower amounts of CaO than Fe-rich areas,in agreement with expected partitioning of these elements related to the composition of the olivine.Iron-rich oxides formed around or inside the olivine crystals during the separation process and confirm a highly oxidized environment during their evolution.We propose that this separation occurred during subsolidus recrystallization under high fO_(2) conditions of the olivine crystals after cooling of the volcanic rocks.It provides evidences for circulation of iron-rich fluids or gas inducing deuteritic processes occurring in the large volcanic cone of the Nyiragongo,in relation with the presence of a shallow magma chamber connected to a large and permanent lava lake.

Effect of Synthesized Forsterite Addition on Properties of MgO Based Castables

High purity forsterite with a mass ratio 60：40 of MgO over SiO2 was synthesized using magnesite, caustic magnesia and natural silica as starting materials. The synthesized forsterite aggregates were added in magnesia based custable with MgO -SiO2 -H2 0 binding system to replace dead burned magnesia up to 60 mass% at an in- terval of 15 mass%. Effect of the forsterite addition on properties ~f MgO based castables was investigated. Micro- structure analysis of related specimens was carried out by means of SEM. Special grade bauxite powders were also in- corporated to form spinel by reaction with magnesia, ac- companying volumetric expansion to compensate high tem- perature shrinkage. Bulk density of the castable decreases with increased forsterite addition. Properties in terms of cold crushing strength and cold modulus of rupture, hot modulus of rupture at 1 400 ℃ and thermal shock resist- ance can be improved by adding an appropriate amount of the forsterite aggregate, preferably around 30 mass%.

Research on Synthetic Forsterite with Magnesite Tailings

High purity forsterite was prepared with magnesite tailings and quartz pounder as starting materials. The influence of the preparution process on the physical properties of the synthetic forsterite was studied. The ph,se composition and the microstructure of the synthetic forsterite were analyzed by means of XRD and SEM. The results ,show thal the composites with 63% MgO fired at 1 670℃ exhibit the highest compact structure.

Experimental Studies on Elasticities of Forsterite-Enstatite Composites:Towards an Understanding of the Rules of Mixture

Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young’s moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul’s calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular,

Efficient synthesis of forsterite via high-temperature thermochemical reactions from boron mud waste without briquetting

Forsterite is a highly demanded material in high-temperature industries due to its superior performance in elevated temperatures.This study proposes synthesizing high-quality forsterite via high-temperature thermochemical reactions using abundant boron mud waste.The new synthesis method capitalizes on the high reactivity of fine raw powder materials,enabling the reaction to reach completion at low temperatures rapidly.The chemical characteristics,microscopic morphology,and structure of synthe-sized samples are systematically studied using XRD and SEM.The results confirm that boron mud can be efficiently transformed into forsterite after 10 min of reactions at 1500℃.The synthesized products attain over 98.7%densification and contain more than 85.0%forsterite with well-developed grains.The activation energy of forsterite grain growth in the 1100-1500℃temperature range is 165.5 kJ/mol.This study provides a low-cost method for producing forsterite and an efficient and environmentally friendly solution for treating solid waste.

Morphologies and Influential Factors of Forsterite Film in Grain-Oriented Silicon Steel

The product quality of graiworiented silicon steel may be affected by each process because of its complicat- ed production technology. Morphologies, compositions and structures of forsterite film formed in different conditions on the samples subjected to high temperature annealing were measured by using a scanning electron microscope, an energy disperse spectroscope, an X ray diffractometer and Fourier transform infrared technique respectively. The morphologies and influential factors of forsterite film were investigated. The results showed that the major compo- nent of forsterite film composed of light-gray spherical particles was Mg2 SiO4, and the minor was MgAl2O4. If the amount of MgO coated on the surface of the steel was less, bare holes or even large-scale bare grains for forsterite film appeared. The higher temperature of water bath during decarburization annealing led to gaps of strips in forster ite film. Moreover, MgO coating method had great influence on forsterite film. Roller coating method was beneficial to increase compactness and smoothness of forsterite film, but was disadvantageous to its thickness.

Structural characterization and strengthening mechanism of forsterite nanostructured scaffolds synthesized by multistep sintering method

In this study, highly porous forsterite scaffolds with interconnected porosities were synthesized using multi-step sintering(MSS) method. The starting powder was nanosized forsterite, which was synthesized from talc and magnesium carbonate powders. The phase composition, average particle size and morphology of the produced forsterite powder were characterized by X-ray diffraction technique(XRD) and transition electron microscopy(TEM). Forsterite scaffolds were produced by foamy method using polymeric sponges. MSS process including three steps was used to efficiently sinter the forsterite nanopowders without destroying the initial porous structure of polymeric sponges. The results showed that MSS technique is an efficient and appropriate procedure to produce highly porous forsterite scaffolds with pore size in the range of 100-300 μm. The compressive strength, compressive modulus and porosity of C12 specimen(sintered at 1650℃ for 1 h with subsequent annealing at 1000℃ for 1000 min) was 1.88 MPa, 29.2 MPa, and 72.4%, respectively, which is very close to that of cancellous bone. The approach studied in this research can be developed for other nanostructure ceramics to produce highly porous scaffolds with interconnected porosities for load bearing applications.

Forsterite Nanopowder:Structural Characterization and Biocompatibility Evaluation

Forsterite, a new biocompatible material was synthesized from Mg（NO3）2.6H20 and TEOS by using the sol-gel method. The material was then heated at 800, 900 and 1000 ℃. The forsterite was noticed as the main crystalline phase in the material fired at 900 and 1000 ℃, while periclase （MgO） was present in all the samples. The tests confirm that in the first two samples forsterite is present as crystallites 〈60 nm, while in the sample synthesized at 1000 ℃ it forms aggregates of micrometre-sized grains. In vitro test was performed by immersing the forsterite powder in the simulating body fluids （SBF） and hydroxyapatite formation on the surface was investigated. We could evidence the formation of hydroxyapatite on the forsterite surface after 7 days of immersion. The MTT test confirmed that forsterite powders dissolution promote osteoblast proliferation of the human-type osteoblasts with no significant cytotoxicity effects.

Forsterite-hydroxyapatite composite scaffolds with photothermal antibacterial activity for bone repair

Bone engineering scaffolds with antibacterial activity satisfy the repair of bacterial infected bone defects,which is an expected issue in clinical.In this work,3D-printed polymer-derived forsterite scaffolds were proposed to be deposited with hydroxyapatite(HA)coating via a hydrothermal treatment,achieving the functions of photothermal-induced antibacterial ability and bioactivity.The results showed that polymer-derived forsterite scaffolds possessed the photothermal antibacterial ability to inhibit Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli)in vitro,owing to the photothermal effect of free carbon embedded in the scaffolds.The morphology of HA coating on forsterite scaffolds could be controlled through changing the hydrothermal temperature and the pH value of the reaction solution during hydrothermal treatment.Furthermore,HA coating did not influence the mechanical strength and photothermal effect of the scaffolds,but facilitated the proliferation and osteogenic differentiation of rat bone mesenchymal stem cells(rBMSCs)on scaffolds.Hence,the HA-deposited forsterite scaffolds would be greatly promising for repairing bacterial infected bone defects.

Mineral Reaction and Oxygen Isotope Equilibrium——An Experimental Study on the Calcite-Forsterite System

There are few mineral reaction experiments dealing with the stable isotope fractionation factors between the reaction products. The only known example is to determine oxygen isotope fractionations between quartz and magnetite at 600 and 800℃ by oxidizing fayalite to form quartz and magnetite. This experimental result has been confirmed by the experiments of isotope exchange reaction. In this note, we report the results of an investigation of oxygen isotope fractionation between calcite

Thermodynamic properties of wadsleyite with anharmonic effect

The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation. Based on the method developed recently by Wu and Wentzcovitch （Phys Rev B 79：104304, 2009） and Wu （Phys Rev B 81：172301, 2010）, we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle, volume and temperature fixed （NVT） molecular dynamic simulations. Our study indicates that phonon-phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature. This is consistent with the Raman experimental observation. The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong-Petit limit at high temperature. The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature con- ditions correspond to the transition zone.

Raman and X-Ray Investigation of Pyrope Garnet （Mg0.76Fe0.14Ca0.10）3Al2Si3O12 under High Pressure

The compressional behavlour of natural pyrope garnet is investigated by using angle-dlspersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressureinduced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KTO is 199 GPa, with its first pressure derivative K′TO fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm^-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes （650-1000 cm^-1） is larger than that of the low frequency （smaller than 650 cm^-1）. Based on these data, the mode Grǖneisen parameters for pyrope are obtained.

Poly (ethylene terephthalate) synthesis with catalysts derived from chrysotile asbestos

The chrysotile asbestos was converted to the forsterite-type compounds by calcination at 740 and 800oC (F7-740 and F7-800), which were used as a catalyst for the polycondensation of bis(hydroxyethyl) terephthalate affording poly (ethylene terephthalate). The obtained forsterite-type compounds did not show any catalytic activity. However, the products obtained by simply treating them with acetic acid significantly promoted the polymerization that produced a THFinsoluble polymer. It was found that the polymer prepared with the acetic acid-treated F7-740 at 160oC for 2 h showed a 93% yield and the number average molecular weight of 6.4 × 103. The observed catalytic activity was higher than that for the acetic acid-treated magnesium oxide, as well as the typical polycondensation catalysts, such as magnesium acetate and antimony oxide.

Synthesis and application of biocompatible nontoxic nanoparticles for reclamation of Ce^3＋ from synthetic wastewater： Toxicity assessment, kinetic, isotherm and thermodynamic study

The aim of present study is to synthesize forsterite nanoparticles（FRST） for the reclamation of cerium ions（Ce3＋） from synthetic wastewater.The aim to synthesize FRST nanoparticles is due to its biocompatible and nontoxic nature.The formation of nanoparticles with average diameter of 58 nm was confirmed by TEM analysis.SEM images of bare FRST nanoparticles show a heterogeneous surface with porous nature.BET surface area of FRST nanoparticles is calculated to be 33.69 m2/g.The significant uptake of Ce3＋ ions can be obtained for all the selected concentrations（25-150 mg/L） within 2 h of adsorbent—adsorbate interaction.The pH study shows that by increasing pH from acidic to alkaline range,higher removal can be achieved.Temperature study demonstrates the endothermic nature of Ce3＋adsorption.The value of sticking probability suggests very high sticking probability of Ce3＋ ion for FRST nanoparticles.Ce3＋ uptake is favored by higher temperature and with the increase in temperature from298 to 328 K,Langmuir adsorption capacity increases from 36.45 to 42.99 m2/g.Applicability of FRST nanoparticles was also investigated for other light and heavy rare earth elements in single solute and multisolute systems,FRST nanoparticles show the significant removal of divalent metallic pollutants as well.The assessment of chemical toxicity of treated wastewater was carried out with the bioluminescent photobacterium（Vibrio fischeri） and decreased toxicity was observed in treated water samples.The outcome of present study suggests that the FRST nanoparticles can be efficiently utilized for the removal of Ce3＋ ions and a wide range of other pollutant species as well.