The crystal growth theory of periclase,corundum,spinel and mullite in different conditions was studied by means of high-resolution instruments,and the special-morphology crystals were characterized.Periclase of cubic system and euhedral spinel are typical cube and octahedron,and can also form any other shapes,such as joined crystallization and step growth,which are limited by the crystallization environment.Mullite belongs to orthorhombic system and has the long columnar crystallization habit.However,the euhedral development is often restricted by the environment.Mullite crystallizes (or peritectic reaction happens between corundum and liquid phase) into columnar shapes when there is a certain amount of liquid phase.The combination of mullite and corundum can exist in the form of simple symbiosis or peritectic reaction.

Cr³⁺-Fe³⁺ co-doped lanthanum aluminate was prepared using La₂O₃ powder,Al₂O₃ powder,Cr₂O₃ powder,and Fe₂O₃ powder as raw materials.The ingredients were blended stoichiometrically according to LaAl_1-x-yCr_xFe_yO₃(x=y=0,0.1,0.2,0.25),ball milled,dried,prefired at 1 200 ℃,ball milled again,molded and sintered at 1 600 ℃ for 2 h.The doped LaAlO₃ was characterized by XRD,XPS and IR.The results show that all the doped products are perovskite structural compounds.The near-infrared radiation performance of the Cr³⁺-Fe³⁺ co-doped samples is greatly improved compared with the undoped ones.The infrared emissivity of the sample LaAl_0.5Cr_0.25Fe_0.25O₃ in the 0.76-2.5 μm waveband increases from 0.236 to 0.83.The increasing mechanism of the infrared emissivity is considered as follows.After co-doping,Cr ³⁺-Fe³⁺ forms Fe³⁺$\leftrightarrow$Fe⁴⁺ small polaron with a transition activation energy of only 0.1 eV,introducing the impurity energy levels corresponding to Cr⁵⁺ and Cr⁶⁺.Thus the impurity absorption and free carriers absorption are enhanced,improving the emissivity in the near-infrared waveband of the material.

When preparing ternary cathode material LiNi_xCo_yMn_zO₂(LNCM),the calcining saggers are vulnerable to the penetration and corrosion of Li₂O in the cathode material. Magnesium aluminate spinel has good hot performance and alkali resistance.The reaction between magnesium aluminate spinel and the precursor of LNCM cathode material at 800-1 100 ℃ was studied by the lab mixing reaction method.The phase composition and the microstructure of the mixed samples calcined at different temperatures were analyzed.The possibility of using magnesium aluminate spinel as the sagger matrix was explored.The effects of magnesium aluminate spinel powder addition (3%,6% and 9%,by mass) on the strength and the thermal shock resistance of the sagger materials were studied.The results show that the sagger containing magnesium aluminate spinel powder is suitable for the preparation of LNCM cathode material with a calcination temperature lower than 1 000 ℃;the addition of 6% can improve the thermal shock resistance of the mullite sagger material.

Al-MgO-Al₂O₃ refractory specimens were prepared using Al powder,fused magnesia and fused brown alumina as raw materials,and thermosetting phenolic resin as binder.Two heating schedules were used for heat treatment in air:1)direct heating to 1 500 ℃ and holding for 2 h;2)heating to 580 ℃ and holding for 2 h and then heating to 1 500 ℃ and holding for 2 h.The influence of the heating schedule on the phase composition and microstructure of the specimens was studied by XRD and SEM.The results show that:1)after heating directly to 1 500 ℃,the non-oxide formed in the specimen is mainly Al₄O₄C;2)first holding at 580 ℃ for 2 h is beneficial to transforming Al into Al₂O(g) at high temperatures to produce (Al₂OC)_x(AlN)_1-x whiskers in the specimen;3)after the heat treatment at 1 500 ℃ following the 580 ℃ treatment,a dense layer with magnesium aluminate spinel and (Al₂OC)_x(AlN)_1-x whiskers as the main phases is formed in the material.

Fracturing proppant was prepared using second grade bauxite powder as the main starting material,ceramic proppant waste powder as the auxiliary raw material,adding 1 mass%-4 mass% of calcium aluminate cement (CA50) as additive,granulating into balls,drying,and firing.The influences of the CA50 addition on properties of the proppant samples such as the bulk density,the breakage ratio and the acid solubility were determined;meanwhile,XRD,and SEM and EDS analyses were conducted.The results show that (1)no mullite is detected,the samples mainly contain corundum,iron-aluminium titanate (FeAlTiO₅),anorthite,and glass;as the CA50 addition increases,corundum and FeAlTiO₅ decrease,anorthite and glass increase;(2)with the increasing CA50 addition,the bulk density and the crushing resistance of the sintered samples first increase and then decrease,and the maximum value appears with 3 mass% CA50;3)with the increasing CA50 addition,the acid solubility of the sintered samples increases gradually,indicating that the resistance to acid solution erosion keeps declining.

Fiber reinforced SiO₂ aerogel was studying object.The hot surface of a sample was heated by a quartz lamp with infrared radiation at 650 ℃ for 4 h.The influence of the reuse times (10,20,and 30) on the thermal insulation performance of the material was studied and the mechanism was analyzed.The results show that the thermal insulation properties of the fiber reinforced SiO₂ aerogel attenuate with the increasing reuse times.The temperature of the cold surface reaches 106 ℃ and even 124 ℃,respectively,when the hot surface of the specimen is reused for 10 times and 30 times.By analyzing the microstructure,composition,pore structure and specific surface area of the sample,it is found that during the reuse in hot and cold alternant conditions,silica aerogel nano particles grow up due to the sintering,and the specific surface area and total pore volume of the material are significantly reduced,which is why the thermal insulation performance attenuates with the increasing reuse times.

The slag corrosion resistance at 1 100 ℃ and 1 300 ℃ of several typical refractories for rotary kilns of the hazardous waste disposal industry,chrome-zirconia corundum 50 brick,chrome-zirconia corundum 30 brick,chrome-corundum brick,high alumina brick,corundum-mullite brick,and alumina-chrome silicon carbide brick,was compared.The results show that:1)after the corrosion test at 1 100 ℃,the six groups of samples all show good resistance to slag corrosion and penetration,and a large amount of slag remains in the crucible;2)after the corrosion test at 1 300 ℃,the slag corrosion and penetration of the six groups of samples are significantly increased;the chrome-zirconia corundum 50 brick shows excellent corrosion resistance but molten slag penetration is observed;the chrome-zirconia corundum 30 brick and the chrome-corundum brick are slightly corroded,and their penetration degree increases;due to the extremely low solubility of chromium oxide in the slag,the chrome-containing samples have excellent resistance to slag corrosion but common resistance to slag penetration;the high alumina brick is corroded the most seriously:the interface structure between the sample and the slag is no longer visible;corundum-mullite brick has anorthite formed after the working layer is corroded by the slag,which promotes the densification of the matrix and hinders the further penetration of the slag;alumina-chrome silicon carbide bricks have poor resistance to corrosion and penetration due to the high apparent porosity.

In order to improve the graphitization degree and oxidation resistance of expanded graphite,the modified expanded graphite was prepared by vacuum impregnation of zirconium oxychloride solution and high-temperature carbon embedded heat treatment.Effects of the carbon embedded temperature (1 550,1 600,and 1 650 ℃) and vacuum impregnation duration (30,60,and 90 min) on the graphitization degree and oxidation resistance of the expanded graphite were researched.The results show that:(1)after modification,the graphitization degree and oxidation resistance of the expanded graphite are improved;(2)the graphitization degree and oxidation resistance of the modified expanded graphite improve with the temperature rising from 1 550 ℃ to 1 600 ℃,but decrease from 1 600 ℃ to 1 650 ℃;(3)the graphitization degree and oxidation resistance of the modified expanded graphite improve with the vacuum impregnation duration prolonging from 30 min to 60 min,but decrease from 60 min to 90 min;(4)the graphitization degree and oxidation resistance of the modified expanded graphite prepared by impregnation at -0.08 MPa vacuum for 60 min and then carbon embedded heat treated at 1 600 ℃ for 3 h are the best.

SiC-diamond ceramics were prepared using SiC and diamond as raw materials,alumina and yttrium oxide as sintering agents,and pressureless firing at 1 850 ℃ for 1 h.Effect of diamond addition (0,0.25%,0.5%,1.0%,2.5%,and 5%,by mass) on properties of the SiC-diamond ceramics was researched.The results show that with the diamond addition increasing from 0.25% to 5%,the density of SiC-diamond ceramics decreases gradually,while the grain size increases first and then decreases.With 0.25% diamond,the ceramics perform the best properties,the density of 90.3%,the thermal conductivity of 83.2 W·m^-1·K^-1,and the specific heat capacity of 0.71 J·g^-1·K^-1.

In order to explore the corrosion mechanism of alkali metal compounds to refractories used in waste incinerators,the corrosion tests of mullite,corundum and chromium corundum castables were carried out at 800,1 000,1 200 and 1 350 ℃ for 30 h by alkali steam method.The physical properties and alkali resistance of three castables before and after corrosion at different temperatures were compared.The results show that:(1)at 800 ℃,the strength of mullite,corundum and chromium corundum castables after alkali corrosion is higher than before,while the strength of corundum castables after corrosion is the highest,the alkali corrosion resistance of mullite and corundum castables is better than that of chromium corundum castables;(2)when the temperature is 1 000,1 200 and 1 350 ℃,the compressive strength of mullite,corundum and chromium corundum castables decreases after K₂CO₃ corrosion;the compressive strength of chromium corundum castables before and after alkali corrosion is higher than that of mullite and corundum castables;and the alkali corrosion resistance of chromium corundum castables is the best.

Alumina-mullite porous ceramics were prepared by foaming method using α-Al₂O₃ micropowder and SiO₂ micropowder as the raw materials,boehmite (γ-AlOOH) sol as the binder,and sodium dodecyl sulfate (SDS) as the foaming agent.Effects of boehmite sol addition (1%,2%,4%,5%,6% 8%,by mass) and SDS addition (1%,1.5%,2%,2.5%,3%,5%,by mass) on the apparent porosity and the crushing strength,and effects of the firing temperature (1 300,1 350,1 400,1 450,1 500,and 1 600 ℃) on the properties and the microstructure of the ceramics were researched.The results show that the apparent porosity of the ceramics decreases with boehmite sol addition increasing,but the crushing strength increases gradually.The apparent porosity increases first and then decreases with the increase of SDS addition,while the crushing strength show the opposite trend.The crushing strength increases first and then decreases with the firing temperature rising,but the apparent porosity decreases all the time.5% boehmite,2.5% SDS and 1 450 ℃ of the firing temperature are the optimal preparation condition,thus the crushing strength of 6.7 MPa,apparent porosity of 79.5%,and thermal conductivity of 0.087 W·(m·K)^-1 are obtained.

The basic structure of annular sleeve lime shaft kilns and their refractories application were summarized.The damage mechanism of the periclase-spinel bricks for the core arch bridge of sleeve lime shaft kiln was analyzed.Suggestions on how to improve the service life of arch bridge in sleeve lime shaft kilns were put forward.

Effect of blast furnace slag and desulfurized slag on the corrosion of silica sol bonded Al₂O₃-SiC-C castables was studied by means of static crucible slag corrosion method.Tthe microstructure,the element distribution and the mineral phase of crucible samples after slag corrosion experiment were analyzed by means of SEM,EDS and XRD.The results show that the desulfurized slag with relatively high contents of CaO,SiO₂ and FeO has stronger corrosion to the sample.The reason is that CaO,SiO₂ and FeO react with Al₂O₃ in the matrix of the sample forming low melting point compounds,which aggravate the corrosion of Al₂O₃-SiC-C castables.

The present situation,disposal technology and characteristics of rotary kiln incineration system of China’s industrial hazardous waste treatment industry were summarized.The refractory requirements,lining design and damage forms of rotary kiln incineration system in China were analyzed,and the optimization countermeasures of refractory materials for a typical rotary kiln hazardous waste incineration process were proposed.

According to the refractory brick types of various grate incinerators in China,the refractory bricks were classified into square brick,pulled anchor brick,mosaic air-cooled brick,drop wall top brick,starting brick,air outlet brick,anchor brick,etc.By categorizing summary and design optimization,the refractory brick type design and dimensional characteristics of the grate incinerator walls were standardized.In combination with the expansion design needs and the furnace wall structural features,the furnace walls were divided into several modular design units,each unit is an independent and interconnected whole.Practice proved that the brick type standardization and the modular design of the furnace wall were suitable for the design of various grate furnace walls,which significantly improved production and construction efficiency,reduced costs,and shortened the stocking and maintenance cycle.Meanwhile,the multi-layer anchoring flexible design and independently air-cooled design of the local high-temperature furnace wall further improved the stability of the furnace wall and reduced the frequency of furnace shutdown for ash removal,significantly extending the operating rate of the incinerator.

The main preparation processes of high-purity SiC micropowder were reviewed,and the new progress of purification process of high-purity SiC micropowder in recent years was introduced.The upgrading of the preparation process,and the industrial technical process and equipment of high purity SiC micro-powder was prospected.

Dense magnesia materials and porous magnesia materials are important branches of magnesia materials,and have played important roles in many important fields.The novel dense or porous magnesia materials are current research hotspots.The preparation progresses of dense magnesia materials and porous magnesia materials,the influence of different catalysts on dense magnesia materials were reviewed.Finally,some suggestions on the development of magnesia materials were put forward.

The research progress of thermal shock resistance of low-carbon magnesia carbon materials was summarized from the aspects of carbon source,magnesia raw material and additives.Some suggestions for the improvement of thermal shock resistance of low-carbon magnesia carbon refractories were put forward.

Thermal shock resistance is one of the most important performances of refractories.There are many test methods for measuring thermal shock resistance in China and overseas,but there is no a universal international standard.Approved by the ISO in August 2016,China established the international standard for test method of thermal shock resistance for refractories by actively exchanging with members of working groups in China and overseas,and carrying out a good deal of test verification work.The technical problems during the establishment process were well solved and the international standard was officially issued in October 2020.

Firstly,the determination method of metallic iron content in hercynite by ferric trichloride solution-potassium dichromate titration was confirmed by the particle size test and the sample weighing test.Secondly,the determination methods of the total content of metallic iron and ferrous oxide (expressed with the corresponding FeO content) by HCl/H₂SO₄ mixed acid decomposition-potassium dichromate titration were confirmed by the particle size test,sample weighting test,HCl and H₂SO₄ addition test,and sodium bicarbonate addition test.Finally,ferrous oxide content in the sample was calculated by the subtraction method,and the mass-change rate of the sample after high-temperature oxidation was used for verification.The method is proved to be accurate and feasible.