Forsterite was synthesized by the molten salt method at 1 100 ℃ for 3 h,using analytically pure MgO and SiO₂ as raw materials and analytically pure NaCl,Na₂CO₃,NaCl-Na₂CO₃ and Na₂SO₄ as the molten salt medium,respectively.The synthesized forsterite was analyzed by XRD,SEM,EDS and Jade.The results show that the purity of the forsterite synthesized with Na₂CO₃ or NaCl-Na₂CO₃ as the molten salt medium is very low,because Na₂CO₃ reacts with MgO and SiO₂ to produce a large amount of Na₂MgSiO₄.The purity of the forsterite synthesized with NaCl as the molten salt medium is very high while that synthesized with Na₂SO₄ is high and a small amount of MgSiO₃ is formed.The analysis shows that the mechanism of synthesizing forsterite in NaCl molten salt is “template growth”,and that in Na₂SO₄ molten salt is “dissolution-precipitation”.

β-SiAlON (z=3) bonded SiC composites were prepared by in-situ catalytic nitridation using SiC particles,Si powder,Al powder and active α-Al₂O₃ powder as starting materials,and Fe as the catalyst.The effects of the nitriding temperature (1 350,1 400 and 1 450 ℃) and the Fe addition (1%,2% and 3% of the mass of Si powder) on the phase composition,the microstructure,the apparent porosity,the bulk density and the hot modulus of rupture of the composites were studied.The results show that the optimal nitridation temperature is 1 400 ℃ and the optimal Fe content is 1 mass% of the mass of Si powder;the sample prepared at 1 400 ℃ for 3 h has uniform β-SiAlON whisker diameter,higher nitriding degree,density and hot modulus of rupture.

Ordinary MgO-C specimens MC (flake graphite addition of 9%,by mass) and MgO-Ti₃AlC₂-C specimens MC-3AC (flake graphite addition of 4% and Ti₃AlC₂ addition of 3%,by mass) were prepared using sintered magnesia,flake graphite,Si powder,and Ti₃AlC₂ powder as the main raw materials,and phenolic resin as the binder.After mixing,shaping,drying at 110 ℃ and curing at 220 ℃,the specimens were heat treated at 1 100,1 400 and 1 600 ℃ for 3 h in carbon embedded condition.The apparent porosity,the cold modulus of rupture,the elastic modulus and the oxidation resistance at 1 100,1 300 and 1 500 ℃ in air atmosphere were detected and XRD analysis was conducted.The results show that:(1) after curing at 220 ℃,specimens MC-3AC have lower apparent porosity and much higher cold modulus of rupture and elastic modulus than specimens MC;(2) after carbon embedded heat treatment at 1 100-1 600 ℃,specimens MC-3AC have lower apparent porosity and higher cold modulus of rupture and elastic modulus than specimens MC;(3) when oxidized at 1 100 and 1 300 ℃,specimens MC-3AC have worse oxidation resistance than specimens MC and specimens MC-3AC oxidized at 1 500 ℃;however,when oxidized at 1 500 ℃,specimens MC-3AC have better oxidation resistance than specimens MC.

Low carbon MgO-C refractories were prepared through in-situ catalytic pyrolysis of phenolic resin,using fused magnesia,flake graphite and silicon powders as raw materials,and phenolic resin added with iron nitrate,cobalt nitrate or nickel nitrate as the binder,firing in argon atmosphere at 800,1 100 and 1 400 ℃,respectively.The effects of the catalyst types on the cold properties of the low carbon MgO-C refractories were studied.The results show that iron nitrate is the best catalyst,which promotes the in-situ formation of CNTs and SiC_w and improves the mechanical properties of refractories.With the phenolic resin containing iron nitrate,the sample after heat treatment at 1 100 ℃ has the highest cold modulus of rupture and cold compressive strength.

The oxidation mechanism of graphite was calculated and analyzed based on the First Principle via the CASTEP module of Materials Studio.The results show that:(1)when structural loss happens in the form that layered graphite loses C atoms in the hexagonal or strip direction,the system has the lowest energy and the most stable structure;(2)when the C atoms on the graphite surface react with O atoms,the O atoms are easier to combine with the C atoms in the hexagonal or strip direction;(3)the actual oxidation behavior of graphite well verifies the calculation results.

Corundum castables were prepared using tabular corundum particles and fines,α-Al₂O₃ micro-powder,micro-sized calcium carbonate,calcium aluminate cement (CAC) and other raw materials.The effects of the micro-sized calcium carbonate on the hydration rate of CAC,the phase composition and the microstructure of the hydration products at 20 ℃ were studied.Meanwhile,the effect of the micro-sized calcium carbonate powder (0-1.5%,by mass) on the strength of CAC bonded corundum castables during curing was also explored.The results show that the slow hydration rate of CAC gives rise to the main hydration product of acicular CAH₁₀ after curing at 20 ℃ without adding micro-sized calcium carbonate;after adding micro-sized calcium carbonate,the hydration rate of CAC increases significantly,and the main hydration products change from acicular CAH₁₀ to lamellar C₄A$\bar{C}$H₁₁.The introduction of micro-sized calcium carbonate accelerates the hydration of CAC,increases the amount of hydration products,and significantly improves the curing strength of CAC bonded castables.

In order to further improve the properties of Al₂O₃-SiC-C castables,Al₂O₃-SiC-C castables were prepared using brown fused alumina,silicon carbide,asphalt,andalusite powder,α-Al₂O₃ micro-powder,SiO₂ micro-powder,Si powder,Al powder and Secar 71 cement as raw materials.The effects of low andalusite powder additions (≤0.055 mm;0,1%,2%,3%,and 5%,by mass) to substitute for the same proportion of brown fused alumina fine powder on the density,the strength,the thermal shock resistance and the oxidation resistance of the castables were studied.The results show that with the increase of the andalusite powder addition,the apparent porosity and the bulk density of the fired samples decrease,and the cold modulus of rupture,the hot modulus of rupture,the thermal shock resistance and the oxidation resistance of the fired samples all increase.

In order to obtain high sintered density,Si₃N₄ ceramics were prepared by oscillatory pressure sintering at 1 745 and 1 775 ℃,respectively.The effects of the Si₃N₄ powder particle size (average particle size of 0.4,2.0,and 2.3 μm) on the microstructure and the properties of Si₃N₄ ceramics were studied.The results show:(1)the relative density of the Si₃N₄ ceramics prepared by the Si₃N₄ powders with three different particle sizes sintered at both temperatures is large,which is 99.65%-99.86%,varying slightly;(2) the sample sintered at 1 745 ℃ with 0.2 μm Si₃N₄ powder has the most uniform microstructure,the largest average length-diameter ratio of β-Si₃N₄ grains,the highest flexural strength and Vickers hardness,which are 5.0,(1 364±65) MPa,(15.72±0.8) GPa,respectively;the sample sintered at 1 745 ℃ with 2.3 μm Si₃N₄ powder has the smallest average length-diameter ratio of β-Si₃N₄ grains,the lowest flexural strength and Vickers hardness,which are 3.30,(846±49) MPa and (13.82±0.8) GPa,respectively.

Adopting aluminum hydroxide as the raw material to prepare α-Al₂O₃,the phase transformation process and microstructure changes of aluminum hydroxide at different calcination temperatures (500,800,900,1 100,1 200,and 1 300 ℃) were studied.The results show that:(1) at 500 ℃,a part of gibbsite loses crystal water and transforms into boehmite;at 500-800 ℃,gibbsite and boehmite continue to lose crystal water and convert into alumina transition phases;(2) at 800-1 200 ℃,phase transformation occurs between alumina transition phases;at 1 300 ℃,all transition phases transform into α-Al₂O₃;(3) when the calcination temperature is 800 ℃,the specific surface area of γ-Al₂O₃ to η-Al₂O₃ is the largest and the activity is the highest,which provides a new way for the catalyst support and the improvement of the cycle life of the battery.

In order to study the effect of the density of sintered alumina aggregate on properties of corundum-spinel castables,sintered corundum with different densities was prepared using industrial Al₂O₃ powder as the raw material,which was further used as aggregates to prepare corundum-spinel castables.The density,the strength,the thermal shock resistance and the slag resistance of the corundum-spinel castables were researched.The results show that:(1)the density and the grain size of the sintered corundum gradually increase with the increase of the density of spheroidized body of industrial Al₂O₃ powder;(2)with the increase of the sintered alumina aggregate density,the water demand of the corundum-spinel castables decreases;the density and the cold strength of the castables increase after firing,and the thermal shock resistance worsens;for the slag corrosion resistance,the castables are similar except the one with bulk density of 3.45 g·cm^-3 is obviously poor;(3)overall,the optimal bulk density of the sintered alumina aggregate is 3.51-3.55 g·cm^-3.Therefore,it cannot be unilaterally considered that the higher the bulk density of the sintered corundum,the better the properties of the castables;over high bulk density will lead to poor thermal shock resistance of refractories and increase the unit weight of refractories.

In order to research the influence of various factors on the properties of forsterite lightweight spherical aggregates and optimize its production technique,forsterite lightweight speherical aggregates were prepared using magnesite fine powder (<0.045 mm),natural silica powder (<0.048 mm) and silica fume as the starting materials,and magnesium sulfate solution with 15 mass% concentration as the binder,pelletizing on a disc pelletizer and sintering at high temperatures.The silica fume addition (5%,10%,and 15%,by mass),the rotation speeds of jar mill (300,400,and 500 r·min^-1),the milling times (1,1.5,and 2 h) and the calcination temperature (1 400,1 420,and 1 450 ℃) were chosen as the research factors,three levels of each factor were chosen for orthogonal design to research the effect of every factor on properties of spherical aggregates.The results show that:the silica fume addition and the calcination temperature are major factors,while the rotation speed of jar mill and the milling time are secondary factors.By comprehensive consideration,when the silica fume addition,the rotation speed of jar mill,the milling time and the calcination temperature are 10%,300 r·min^-1,1 h and 1 420 ℃,respectively,the production technique is opitimal.The lightweight spherical aggregates produced have good properties,evenly distributed pores diameter,and increased micropores,which are expected to become excellent basic heat insulation raw materials.

In order to improve the porosity and the thermal insulation performance of porous mullite materials prepared by ignition loss method,the porous mullite materials were prepared using SiO₂ micropowder and α-Al₂O₃ micropowder as the main raw materials,walnut shell powder impregnated by SiO₂ sol with solid content of 3 mass%,ZrO₂ sol with solid content of 5 mass%,and Al₂O₃ sol with solid content of 7 mass%,respectively,as the pore-forming agent,and PVA as the binder,ball milling,pressing,natural drying and 3 h heat treatment at 1 500 ℃.The apparent porosity,the bulk density,the cold compressive strength,and the thermal conductivity of the materials were determined,and the phase composition and the microstructure of the materials were analyzed.The results show that:(1)compared with the porous mullite prepared with unimpregnated walnut shell powder,the developed materials have significantly decreased linear shrinkage,and thermal conductivity,but obviously increased apparent porosity.The cold crushing strengthes decreased significantly,but all exceed 30 MPa;(2)it is found that the porous mullite material prepared by impregnating walnut shell powder with SiO₂ sol as pore forming agent has good comprehensive properties,with 39% of apparent porosity and 55 MPa of cold crushing strength.

Al₂O₃-SiO₂ castables were prepared using three-grade bauxite (5-0.088 and ≤0.088 mm ),special-grade bauxite ( 1-0.088 and ≤0.088 mm ) and silicon carbide (≤0.074 mm ) as main raw materials,calcium aluminate cement as the binder,and adding an appropriate amount of α-Al₂O₃ micropowder,SiO₂ micropowder and water reducing agent.The linear change rate,the apparent porosity,the chemical composition,the phase composition and the microstructure of the samples fired at 1 400 ℃ for 24 h in air atmosphere were analyzed,and the influence of inert oxidation of SiC on the linear change rate of the samples was discussed when the SiC addition was 3%,6%,8% and 10%,by mass,respectively.The results show that:(1)the product SiO₂ of SiC inert oxidation can fill the pores and reduce the apparent porosity,but it does not react with Al₂O₃ to form mullite immediately after formation;(2)secondary mullitization is the main factor for the increase of the linear change rate of the samples;excessive SiC inhibits its own inert oxidation,leading to a relative reduction of the oxidation product SiO₂,which is not conducive to the sintering and the continuous secondary mullitization of the samples;(3)when the SiC addition is 6% in the full-component sample,the sample has the maximum linear change rate,while maintaining relatively uniform microstructures.

In order to explore the effect of different fused magnesia particles on their properties,four kinds of magnesia-carbon brick samples were prepared using 97 fused magnesia,97.5 fused magnesia,97.5 fused magnesia (with mole ratio of CaO∶SiO₂ >2) and 97.5 large crystalline fused magnesia as aggregates (all of them with the particle size of 6-3,3-1,1-0.074 and ≤0.074 mm),97.5 large crystalline fused magnesia powder (≤0.074 mm) as the matrix,phenolic resin as the binder and -196 graphite as the carbon source.The bulk density,the apparent porosity,the cold compressive strength,the hot modulus of rupture,the slag resistance,and the oxidation resistance of the samples as well as the phase composition and microstructure were tested according to the national standards.The results show that:(1)the periclase grain size,the hot liquid content and the high melting point phase are the three major factors affecting the properties of the magnesia-carbon brick samples;(2)the larger the grain size of periclase,the better the performance of the samples;(3)the hot liquid content is one of the main factors to reduce the hot performance of the samples;(4)the high melting point phase increases the apparent porosity of the samples,reduces the cold compressive strength and the hot modulus of rupture,and has obvious effects on the oxidation resistance and the slag resistance.

To improve the hydrophobicity of calcium aluminate cement products,calcium aluminate cement paste samples and corundum castable samples were prepared with calcium aluminate cement,polydimethylsiloxane,tetraethoxysilane,tabular corundum,etc.as starting materials.The entire hydrophobic modification was adopted,and the effects of the addition of hydrophobic modifier polydimethylsiloxane (0,1%,2% and 5% of the water addition,by mass) on the setting time of calcium aluminate cement paste and the hydrophobicity of the paste samples,as well as on the density,the cold strength and the hydrophobicity of corundum castable samples were studied.The results show that:with the increase of the polydimethylsiloxane addition,the initial setting time and the final setting time of the calcium aluminate cement paste are prolonged;the density of the castable samples decreases slowly,the cold compressive strength and the cold modulus of rupture decrease significantly;the water contact angle increases from 113° to 151°,gradually improving the hydrophobic performance,and the samples have high stability to acid,alkali and boiling water.

The slag resistance of two kinds of natural bauxite clinker blocks and three kinds of homogenized bauxite clinker blocks was studied by cutting and static crucible inlaying at 1 500 ℃ for 6 h.The results show that the iron slag resistance of the natural bauxite clinkers is significantly better than that of the homogenization bauxite clinkers,which has no positive correlation with the Al₂O₃ content and the water absorption rate;for natural bauxite clinker with Al₂O₃ content more than 88 mass%,the water absorption rate determines the slag resistance;for homogenized bauxite clinker,the iron slag resistance increases with the increase of the Al₂O₃ content,has no correlation with the water absorption.According to SEM,it can be found that the difference of glass phase distribution is the main reason for the huge difference of the iron slag resistance between natural bauxite clinkers and homogeneous bauxite clinkers.Therefore,no matter the alumina content,homogenization bauxite clinkers are not suitable for the parts contacting with molten slag,such as iron runners.

Mullite samples were prepared using various crystalline alumina micropowders (α-Al₂O₃,ρ-Al₂O₃ and γ-Al₂O₃) as the aluminum source,mixing with kyanite,adding polyvinyl alcohol,pressing,and heat treating at different temperatures (1 300,1 400,1 500 and 1 600 ℃).Their properties were studied.The results show that the solid phase reaction of the sample with α-Al₂O₃ as the aluminum source is the most complete after sintering at 1 600 ℃,and the main phases are mullite and zirconia.When the aluminum source is α-Al₂O₃,the obtained samples have higher bulk density,lower apparent porosity and higher compressive strength.

Corundum spinel castables were prepared with tabular corundum particles (6-3,3-1,and ≤1 mm) and fine powder (≤0.045 mm),fused spinel particles (≤1 mm) and fine powder (≤0.045 mm),sintered spinel particles (≤1 mm) and fine powder (≤0.045 mm),active spinel micropowder (d₅₀=1.82 μm),active α-Al₂O₃ micropowder (d₅₀=1.68 μm),Secar 71 cement as raw materials.The effects of different spinels (fused spinel,sintered spinel,sintered spinel+active spinel) on the properties of castables were studied.The results show that:(1)the introduction of different spinels into corundum-spinel castables has little effect on the modulus of rupture and compressive strength of the sample after drying at 110 ℃ for 24 h,but fused spinel can reduce the amount of water,improve the fluidity and obtain excellent construction performance;(2)fused spinel improves the slag corrosion resistance of the material,and sintered spinel is favorable for the slag penetration resistance and the thermal shock resistance;(3)adding an appropriate amount of active spinel powder offsets the shortage of sintered spinel and improves the workability,but has a certain negative impact on the thermal shock resistance.

In order to further reduce the consumption of coal,electricity and refractories for per ton of cement clinker,the energy-saving linings for transition zone of cement rotary kilns were developed through integrated modularity and lightweight technology of materials,and the thermal insulation effect of the linings with different integrated modularity structures was explored,which was applied in a 5 000 t·d^-1 new dry cement production line.The technology could effectively reduce the mass of kiln lining,reduce the load and the surface temperature of the cylinder.

Due to the intermittent operation of shuttle kilns,the flue gas volume and temperature,the pollutant content and other indicators are changing at any time,bringing a series of problems for flue gas environmental treatment to meet the emission standards.After years of practice,the pollutant content of shuttle kilns after flue gas treatment meets the fourth period standard of “Shandong Province Regional Air Pollutant Comprehensive Emission Standard”,and the emission index is stable,which realizes the coordinated and efficient operation of three shuttle kilns.

The research progress of refractories for inclined channel area of CDQ ovens and their damage mechanism in recent years was reviewed.The advantages and disadvantages of the research were summarized.The research direction and development trend of the inclined channel area of CDQ ovens were prospected.

Al₂O₃ aerogel has great application potential in the field of high temperature insulation due to its light weight,high temperature resistance and good stability.The preparation process and the mechanism of Al₂O₃ aerogel by sol-gel method in recent years were expounded;a variety of drying methods were introduced;the modification processes in hydrophobicity,enhancement and high temperature resistance were summarized;and the future development direction was prospected.