Effect of aggregates and fine powder contents on the explosive resistance of hydratable alumina bonded corundum castables was investigated with fused white alumina particles and fine (5-3 mm,3-1 mm,≤1 mm and ≤0.074 mm),hydratable alumina (d₅₀=2.4 μm),reactive α-Al₂O₃ micropowder (d₅₀=1.198 μm) and microsilica (d₅₀=0.268 μm) as main raw materials.The mass ratio of aggregates to fine powder was changed from 60:30 to 70:20.The castables were heat treated at 1 400 ℃ for 3 h in air atmosphere.The cold mechanical properties,the air permeability,the pore size distribution and the explosive resistance were tested according to the relevant national standards.The results show that with the aggregate content increasing,the mechanical properties of the specimens after demoulding and drying at 110 ℃ gradually increase,while the cold mechanical properties of the specimens heat treated at 1 400 ℃ gradually decrease,the bulk density increases slightly,and the apparent porosity decreases;the air permeability after demoulding and drying at 110 ℃ increases at first and then decreases,the air permeability and the average pore size of the specimens after heat-treatment at 1 400 ℃ increase gradually; the explosive resistance of specimens increases at first and then decreases after curing at room temperature for 12 h.When the mass ratio of aggregates to fine powder is 68:22,the explosive resistance reaches the best values.

To improve the properties of corundum based dispersive purging plugs,fused white corundum particles and fine powder,α-Al₂O₃ micropowder and Cr₂O₃ micropowder were used as raw materials,the mass ratio of aggregates to matrix was 85:15,and the fused white corundum fine powder was substituted with MgCO₃ by different amounts (0,1%,2% and 3%,by mass).The effect of the MgCO₃ micropowder addition on the properties of the purging plugs was studied.The results show that with 1% MgCO₃ powder,the cold crushing strength,the cold modulus of rupture,and the hot modulus of rupture of the samples increase,while as the addition keeps increasing,the cold and hot strengths decrease,the bulk density decreases,the apparent porosity increases,and the air permeability slightly changes.MgO from the decomposition of MgCO₃ at high temperatures reacts with Al₂O₃ in the matrix to form spinel creating strengthening effect. With excessive MgCO₃,the expansion rate and hot strength of the samples decrease,which is related to the formation of low melting point phases in the system.

In order to improve the comprehensive properties of zirconia products,specimens prepared with aggregates of different density were designed:65 mass% fused dense zirconia particle,45 mass% fused dense zirconia particles plus 20 mass% fused zirconia bubble,and 65 mass% fused zirconia bubble.After mixing,hydraulic pressing,drying,and firing at different temperatures (1 650,1 720 and 1 800 ℃) for 6 h,the cold crushing strength,the cold modulus of rupture,the thermal conductivity,the linear expansion rate and the hot creep resistance of the prepared specimens with the total amount of ZrO₂+HfO₂+Y₂O₃≥99.0% were tested,and the phase composition and the microstructure were analyzed.The results show that:1)the composite properties of the specimen using 45 mass% fused dense zirconia particles plus 20 mass% fused zirconia bubble as aggregates are the best;the cold crushing strength,the cold modulus of rupture and the creep resistance do not decrease significantly while the apparent porosity increases and the thermal conductivity decreases,and the linear expansion change rate is also small;the cold crushing strength,the cold modulus of rupture and the creep resistance of the specimen with 65 mass% fused zirconia bubble as aggregates decrease significantly,although the apparent porosity increases further and the thermal conductivity decreases further;2) the optimum firing condition is at 1 720 ℃ for 6 h.

Citric acid complex precursor was prepared by the sol-gel method with citric acid as the complexing agent and tetrabutyl titanate as the titanium source.Then TiN powder was prepared after the heat treatment of the precursor in nitrogen atmosphere.The effects of the reaction temperature (800-1 300 ℃) and the molar ratio of tetrabutyl titanate to citric acid (3:1,2:1,1.7:1) on the proportion of TiN by carbothermal nitridation reduction were studied.The results show that ammonium titanium citrate complex can be prepared by the precursor xerogel;higher citric acid addition is beneficial to the carbothermal reduction reaction;higher heat treatment temperature accelerates the nucleation of TiN;when the molar ratio of tetrabutyl titanate to citric acid is 2:1,equiaxed TiN powder with an average particle size of ~60 nm was prepared after the precursor xerogel was heat treated at 1 200 ℃ in flowing N₂ atmosphere.

Porous ceramics were prepared using fly ash as the main raw material,adding different kinds and different amounts of pore-forming agents (carbon powder:5%-50%;wood fiber 5%-30%;and carbide slag:0-50%,by mass),pressing under 100 MPa,and sintering at 1 100 ℃ for 2 h.The results show that (1)the apparent porosity,the average pore size,the gas permeability,and the nitrogen flux of the porous ceramics increase while their density decreases with the rising carbon powder addition;(2)with the increasing carbide slag addition,the apparent porosity,the gas permeability,and the nitrogen flux of the porous ceramics increase,the density decreases,while the average pore size remains almost unchanged;(3)as the wood fiber addition increases from 5% to 15%,the apparent porosity and the average pore size of the porous ceramics increase while the density decreases;as the wood fiber addition reaches 30%,the apparent porosity and the density of the porous ceramics remain unchanged,while the average pore size decreases gradually;the change of the gas permeability and the nitrogen flux shows no obvious trend;(4)the main phases of the porous ceramics prepared with carbon powder are quartz,anorthite and calcium silicate;while those with carbide slag are quartz,anorthite,gehlenite,and calcium silicate.Using carbon powder and carbide slag as pore forming agents,the properties and pore parameters of porous ceramics could be adjusted linearly by changing the addition of pore forming agents.

In order to study the degradation mechanism of high chrome bricks in phosphorus containing high sodium coal slag,a residual brick in the junction of the upper cylindrical part and the dome part of a multi-component slurry gasifier of a plant was analyzed.The microstructure and micro zone phase composition of the residual brick were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).Post-mortem analysis of the residual brick shows three layers: a reaction layer,a zirconia depletion penetration layer and a zirconia containing penetration layer.Since phosphorus containing high sodium coal slag has strong dissolution to high chrome brick during service,(Al-Cr)_ss solid solution in the matrix and some fused Cr₂O₃ recrystallized particles form (Mg-Al-Cr-Fe)_ss spinel solid solution,introducing structural differences and cracking,which causes spalling.Phosphate in the coal slag can promote precipitation of phosphorus containing liquid/crystal phases,increase the slag viscosity and slow down the slag penetration.

CaZrO₃ specimens were prepared by the high-temperature solid state method using analytically pure ZrO₂ and Ca(OH)₂ as raw materials,adding different amounts of Co₂O₃ (0,0.5%,1.0%,1.5% and 2% by mass),batching,molding,drying and firing at different temperatures (1 500,1 550 and 1 600 ℃ for 3 h).The results show that as the Co₂O₃ addition increases,the bulk density,the linear shrinkage and the average grain size of the prepared CaZrO₃ first increase and then decrease,while the apparent porosity changes in the opposite trend.CoO from the decomposition of Co₂O₃ has infinite displacement reaction with CaO,which reduces the activation energy of the reaction between CaO and ZrO₂,thus promoting the densification of the specimens.However,when the Co₂O₃ addition exceeds 1.5 mass%,more O₂ is produced during the decomposition of Co₂O₃,and the generated CoO cannot solid-dissolve with CaO crystals in a short time,which hinders the direct contact of reactants in the grain boundaries thus reducing the sintering performance.Therefore,the optimal addition of Co₂O₃ is 1.5 mass%,and in that case,the specimen has 4.25 g·cm^-3 of bulk density,3.3% of apparent porosity,and 6.13 μm of CaZrO₃ average grain size.

Nozzle plate samples for aluminum strip continuous casting and rolling were prepared using aluminum silicate ceramic fiber,kaolin and aluminum tripolyphosphate as main raw materials,silica sol or silica sol-epoxy resin as the bonding system,pulping,casting,curing at different temperatures (25,30,35,40,45,50 and 60 ℃) for different durations (40,60,90 and 120 min),drying at 120 ℃ and heat-treating at 800 ℃.The migration thickness of silica sol and the cold modulus of rupture were measured,and the microstructure was analyzed.The results show that:1)with the same curing temperature,the thickness of the silica sol migration layer of the samples with the different combination systems decreases with the increase of the curing time;with the same curing duration,it basically decreases first and then increases with the increase of the curing temperature;the optimal curing condition is at 40 ℃ for 120 min;2)the silica sol-epoxy composited bonded samples have thinner silica sol migration layers and lower cold modulus of rupture than the silica sol self-curing bonded samples;3)the silica sol-epoxy resin complicated bonded system has better machinability but slightly lower mechanical strength than the silica sol self-gel system.

Corundum-mullite materials were fabricated using electro-fused dense corundum,tabular alumina,electro-fused mullite and composite powder of silicon and aluminum sources as raw materials. Effects of electro-fused dense corundum and tabular alumina on structure and properties of corundum-mullite materials fired at 1 600 ℃ and 1 700 ℃ were studied.The results show that: (1) electro-fused dense corundum has low reactivity,and in-situ mullite generates slowly and continuously,with fewer grains and larger sizes;while tabular alumina has high reactivity,and in-situ mullite has more grains,smaller sizes and uniform distribution;(2) with the same firing temperature,compared with electro-fused dense corundum mullite material,tabular alumina mullite material has relatively higher apparent porosity,smaller linear expansion rate,lower elastic modulus,cold modulus of rupture and cold compressive strength,but better thermal shock resistance;(3) when the firing temperature is increased from 1 600 ℃ to 1 700 ℃,the sintering degree,pore coalescence,in-situ mullite grain growth and hot modulus of rupture of the two materials are improved,but the thermal expansion coefficient mismatch degree also increases,resulting in lower cold modulus of rupture compared with the hot modulus of rupture.The in-situ mullite growth is more obvious in the electro-fused dense corundum mullite material,decreasing the cold compressive strength and cold modulus of rupture.

The thermal conductivity,the water resistance,the acid and alkali resistance of carbonaceous castables for blast furnace are the key factors to affect the cooling effect of carbonaceous lining.By analyzing the properties of SiC-containing carbonaceous castables and carbon-based carbonaceous castables,it can be found that the SiC containing carbonaceous castable has higher compressive strength;the carbon-based carbonaceous castable has high drying strength but greatly reduced compressive strength after fired at high temperatures.SiC-containing carbonaceous castable has better water resistance but completely loosened after soaking in 2 mass% sodium hydroxide solution.Therefore,when alkali vapor penetration and water cooling pipe leakage may exist at the bottom of the blast furnace,the SiC-containing carbonaceous castables bonded by sol shall be carefully used.The gap between the actual thermal conductivity of carbonaceous castables and the literature report is large,so the quality shall be controlled and accurately analyzed to avoid affecting the cooling effect due to poor heat transfer in the application.

In order to develop new type basic insulation refractory raw materials,column specimens (?36 mm) were prepared using natural forsterite fine powder and magnesite fine powder as raw materials,anthracite coal as the pore forming agent,mixing according to the chemical composition of forsterite (2MgO·SiO₂) and wet milling,then dry molding and calcining at different temperatures.Effects of the rotation speed,calcination temperature and anthracitic coal extra addition on the properties of the specimens were researched.The developed raw materials were applied on forsterite castables.The results show that:when the calcination temperature reaches 1 300 ℃,all mineral phases convert to beneficial phases.With the increase of the rotation speed and the rising calcination temperature,the bulk density of the specimen increases,the apparent porosity decreases and the strength increases.By comprehensive consideration,400 r/min and 1 450 ℃ are taken as the most suitable scheme.The addition of anthracitic coal lightens the specimens,the light-weight raw material with uniformly distributed micropores can be gained,and performs well in forsterite castables.

For the 300 MW high temperature insulation cyclone of Baima Company after long time running,the expansion joints and gaps between bricks enlarged,the high temperature flue gas and materials entered the wall,causing a large area of refractory brick spalling off,over-temperature of the cyclone shell,shell redness and other problems.Improvement measures were put forward:weld heat-resistant anchor parts on the outer cylinder wall,then lay 250 mm thick lightweight insulation plastic materials in the insulation layer and 150 mm thick SiC abrasion-resistant plastic materials on the working layer;optimize construction,design expansion joints at the areas such as direct part and top of the cyclone,the inlet flue pipe,and bake the oven strictly according to the heating curve.The improved high temperature insulation cyclone was used for 5 years,with no shell redness,showing obvious improvement effect.

In view of the iron ladle leakage accident in a steel company under the operation mode of “one ladle to the end”,the slag iron in each part of ladle,the new bricks at the ladle bottom,and the residual bricks of the accident ladle were sampled.The analysis shows that the main reasons for the abnormal damage of ladle brick were the chemical erosion to the brick caused by a large amount of iron oxides in the slag;oxides such as CaO and MnO penetrated into the interior of the brick and formed low melting point phases with the components in the brick.According to the damage mechanism of molten iron ladle,the control and countermeasures of online safe operation were ruled.

TiN nanomaterials are regarded as a new generation of thermoplasmonic materials due to their high melting point,good chemical stability,excellent oxidation resistance,high electrical conductivity,and localized surface plasmon resonance (LSPR) characteristics.The LSPR and photothermal conversion properties of TiN nanomaterials depend on the composition,the structure,the particle size and the specific surface area.Therefore,the effective preparation of TiN nanomaterials is the key to realize the industrial application in the field of photothermal conversion.The preparation methods and latest research progress of TiN nanomaterials were reviewed,Technical processes and synthesis mechanisms were described.The differences and application scopes of the different methods were summarized.Meanwhile,the application state of TiN nanomaterials in photothermal conversion was generalized.Finally,the future investigation and development direction of TiN namomaterials were proposed.

The application progress of modified and optimized traditional carbon materials (mainly flake graphite) by surfactant,granulation and surface coating into refractory castables in China and overseas was summarized.The process characteristics and current problems were also introduced.The research state of micro/nano-carbon materials applied in carbon containing refractory castables was reviewed,and the preventing reasons were analyzed.

The rare-earth zirconates were proposed as one of the most promising high-temperature thermal barrier materials as a result of a combination of many excellent properties,such as high temperature resistance,anti-sintering,low thermal conductivity,stable high-temperature phase structure and good corrosion resistance.The research progress of the crystal structure,physical properties,mechanical properties,thermal shock resistance and thermal corrosion resistance of the thermal barrier coating system was reviewed,and the development direction of these materials in the future was further prospected.

The research progress of Al₂O₃-ZrO₂-C slide plate material was summarized from the effects of oxides,carbon,antioxidant and other raw materials on properties,and the future research direction of slide plate for calcium-treated steel was predicted in order to provide reference for improving the service life.

In view of the increasing shortage of high quality alumina raw materials in China,the global distribution of kaolin resources and the resource characteristics of China were summarized.The application of coal series kaolin in refractories was mainly stated,such as preparation of Al₂O₃-SiO₂ refractories,light/semi-light weight insulation refractory products and monolithic refractories.The development direction of coal series kaolin was indicated in order to provide reference for the research and comprehensive utilization of coal series kaolin in refractory industry.