Effect of B4 C on Oxidation Resistance of Low-Carbon MgO-C Materials

B4C was added into the low-carbon MgO-C materials in order to improve the oxidation resistance. The results show adding 0. 3wt% B4C can get the best oxidation resistance and adding 0. 2 wt% B4C can get the highest hot modulus of rupture. Altogether, adding 0. 2wt% B,C into the low-carbon MgO-C materials can get better oxidation resistance and hot strength.     

Investigation on corrosion and wear resistance of MgO-Al2O3 composite coating prepared by plasma electrolytic oxidation

Ceramic coatings were prepared on 6061 Al alloy in a mixed electrolyte with/without MgO powders at different treatment durations. The results of energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) showed that MgO powder was incorporated into the coatings, and Mg species gradually aggregated into coating inside as prolonging the oxidation time. Scanning electron microscopy (SEM) showed that MgO additive had a certain effect on the microstructures and coating thickness. The corrosion behavior tests evaluated by potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution suggested that at the same treatment time, the addition of MgO powders can improve the corrosion resistance of the coating, and the Mg-rich layer can affect the corrosion resistance of the coating. The tests of mechanical properties showed that the addition of MgO powders improved the stability and hardness of the coating.     

纳米Nb粉对等离子弧喷焊铁基合金组织与耐磨性的影响

采用等离子弧喷焊技术在Q235表面制备未添加与分别添加1wt%, 3wt%和5wt%纳米Nb粉的铁基合金喷焊层。通过X射线衍射仪(XRD)、金相显微镜(OM)、扫描电镜(SEM)和能谱仪(EDS)对喷焊层的相组成、显微组织、微区成分及磨损形貌进行分析;利用维氏硬度仪和销盘磨损仪检测喷焊层截面硬度和表面耐磨性。结果表明,铁基喷焊层主要由α-Fe, γ-Fe和Cr7C3组成,添加纳米Nb粉后原位生成NbC相,且随Nb含量增至5wt%,出现了Cr23C6相。纳米Nb粉的加入使喷焊层组织中未转变的奥氏体增多,组织形貌由近等轴晶转变为树枝晶,并且添加5wt%纳米Nb粉的喷焊层组织发生明显细化。添加纳米Nb粉使喷焊层的硬度明显提高,其中添加1wt%和3wt%纳米Nb粉的喷焊层硬度均可达约766 HV0.3。纳米Nb粉的加入同时提高了喷焊层的耐磨性,磨损机制由黏着磨损变为磨粒磨损。     

低碳镁炭砖及其研究进展

分别就导热性、抗热剥落性能、抗氧化性、抗渣侵蚀性能等几个方面综述了低碳镁炭砖的研究进展 ,并讨论了影响这些性能的一些因素。指出了低碳镁炭砖亟待解决的问题是提高其抗热剥落性 ,抑制碳的氧化 ,提高材料的抗渣侵蚀性。最后指出 ,镁炭砖今后的发展方向是低碳化及如何在降低碳含量的同时保持良好的抗热剥落性能     

复合抗氧化剂对Al2O3-SiC-C砖性能的影响

以均化矾土、板状刚玉、碳化硅、石墨为主要原料,利用酚醛树脂作为结合剂,研究了复合抗氧化剂(硅粉、铝粉、碳化硼)的引入形式及加入量对Al2O3-SiC-C砖的性能影响.结果表明:添加复合抗氧化剂可提高Al2O3-SiC-C砖的高温抗折强度,随铝含量的增加,对提高高温抗折强度的提高越明显;抗氧化效果从强到弱依次为:添加碳化硼的复合抗氧化剂>复合铝硅抗氧化剂>金属铝>金属硅;在复合抗氧化剂中引入碳化硼能够有效的提高Al2O3-SiC-C砖的抗渣侵蚀性能及热震稳定性.     

Al2O3-ZrN-Sialon-C复相耐火材料抗渣侵性能研究

以板状刚玉、石墨、α-Al2O3、金属铝粉、单质硅粉为主要原料,ZrN-Sialon复相粉体为添加剂,采用酚醛树脂结合制备了Al2O3-ZrN-Sialon-C复相耐火材料.采用静态坩埚法研究了ZrN-Sialon复相粉体加入量对材料抗渣侵蚀性能的影响,借助SEM与EDS面扫描对渣蚀后材料的结构和成份进行分析,并探讨了Al2O3-ZrN-Sialon-C复相耐火材料的抗渣侵蚀机理.结果表明:ZrN-Sialon复相粉体加入量为9wt％时,材料表现突出的抗钢渣侵蚀性能.研究表明材料中Sialon氧化后生成的SiO2能形成致密的氧化保护层,同时ZrN氧化后形成的ZrO2有利于提高抗钢渣的浸润,阻止钢渣的渗透与侵蚀.分析认为Al2O3-ZrN-Sialon-C复相耐火材料的钢渣侵蚀机理为氧化-熔蚀-渗透.     

石墨烯对水性环氧富锌涂料中锌粉的取代能力研究

针对水性重防腐涂层体系中水性环氧富锌底漆高锌粉含量所带来的生产成本高、不易贮存、环境污染大等问题,采用在涂料中添加少量石墨烯以取代部分锌粉的改进方法。通过动电位极化曲线、电化学阻抗谱等方法研究了锌粉含量以及石墨烯添加量对环氧富锌涂料性能的影响,结果表明:涂层的耐腐蚀性随着锌粉含量增加而提高,锌粉占锌粉与硫酸钡总质量的80%时,腐蚀速率为0. 002 03毫米/年(mm/y),当涂层中锌粉占锌粉与硫酸钡的总质量的20%时,随着石墨烯添加量从占锌粉、硫酸钡与石墨烯总质量的0增加至0. 8%,腐蚀速率先上升后下降,当石墨烯含量达到0. 6%时,腐蚀速率为0. 0 038 mm/y,涂层的耐腐蚀性达到最大值。     

固液混合铸造Al-Cr合金的耐蚀性能研究

采用固液混合铸造新技术制备了Al-10Cr合金,通过对固液混合铸造Al-10Cr合金的阳极极化曲线测定,考察了其腐蚀性能。结果表明,当加粉量为40%、粉末粒度为74～175μm时可获得均匀的细晶组织,且耐腐蚀性能优于不加粉半固态铸造Al-10Cr合金。     

片状玻璃对水性复合锌铝合金涂层耐蚀性的影响

为了改善水性锌铝合金涂层的耐蚀性能,在硅烷钝化液中加入玻璃粉制备了玻璃/水性锌铝涂层,采用中性盐雾试验、电化学阻抗谱、极化曲线等方法研究了玻璃粉用量对 Q235 钢表面该涂层耐蚀性能的影响,利用扫描电镜、能谱、X 射线衍射等技术分析了涂层的形貌、组成以及元素分布状况。结果表明,添加片状玻璃粉可以提高涂层的耐蚀性能。玻璃粉与金属粉以平行叠加的方式排列在锌铝合金涂层中,部分玻璃粉包覆在涂层的外围形成致密的网状结构。当玻璃粉的添加量为 20 g/L时,涂层的耐蚀性能最好,耐中性盐雾试验时间为 3 100 h,是不添加玻璃粉涂层的 5 倍。     

Effect of Al addition on creep resistance of MgO-Al2O3 composite for sliding plate at 1400 °C

MgO-Al₂O₃ composites were prepared using fused magnesia, α-Al₂O₃ micropowder, tubular alumina, metal aluminum and sintered magnesia as raw materials, magnesium aluminate sol as the binder. The creep resistance test was conducted at 1400 °C under 0.2 MPa with insulation for 50 h. The specimens after creep resistance test were characterized and analyzed by XRD, SEM, and EDS to investigate the effect of adding metal aluminum powder on the creep resistance of magnesia based composites as well as its mechanism. The results show that Al-MgO-Al₂O₃ composite has better creep resistance than MgO-Al₂O₃ composite. Power Al is more reactive than AlN, adding Al function is to accelerate both spinel solid solution(containing MgAlON) and AlN-polytype, both are reinforcement phase for MgO-Al₂O₃ composite. The mechanism that metal Al powder improves the creep resistance of the specimen M₂ can be expressed as follows：An oxygen concentration gradient exists in the specimen M₂ from the external areas to the internal areas. The Al in external areas is oxidized into Al₂O₃ and further solid-solves with MgO forming MgAl₂O₄. The oxidation of Al leaves shell structures which can bear some compressive stress, restraining the volume shrinkage. When the oxygen concentration is low, Al is nitrided forming reinforcing phases such as AlN polytype and lamellar-structure MgAlON with reticular distribution, restraining the volume shrinkage of specimen M₂.     

Effect of Ti （C,N） on Properties of Low-carbon MgO- C Bricks

The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.     

Cr7C3: A potential antioxidant for low carbon MgO–C refractories

Magnesia carbon (MgO–C) refractory, one of the most commonly used refractories in the steelmaking system, relies on graphite to improve the thermal shock resistance and slag corrosion resistance. The oxidation of graphite carbon in a MgO–C brick usually leads to the destruction of the carbon network in the brick, which causes the structure of the brick to become loose and easily eroded. At present, metal powders, carbides, and borides are used as antioxidants to prevent the oxidation of carbon in MgO–C bricks. The metal carbide Cr₇C₃ can be prepared from aluminum chromium slag through a simple synthetic process and at a low cost. In this work, we investigated the oxidation resistance of low carbon MgO–C refractories with different amounts of Cr₇C₃ powder (1, 2, 3, and 4 wt%). The refractories with 3 wt% Cr₇C₃ powder showed optimal resistance to oxidation. The microstructure indicated that oxygen reacts with Cr₇C₃ preferentially over carbon to form chromium oxide and magnesium chromium spinel, blocking the pores and hindering oxygen diffusion. Carbon arising from the reduction of carbon monoxide by Cr₇C₃ can act as a supplementary carbon source. The better oxidation resistance also contributed to the improvements in slag corrosion and thermal shock resistance of the refractories.     

SiAlCN型PDC陶瓷的研究进展

综述了SiAlCN型PDC（Polymer Derived Ceramics）陶瓷的制备、性能和应用。SiAlCN陶瓷有四类制备方法：粉末混合型：聚硅氮烷陶瓷前驱体与氧化铝粉末直接混合;粉末溶解型：含铝化合物粉末溶解于聚硅氮烷前驱体溶液中;单源前驱体型：铝原子通过适当的含铝化合物接枝在聚硅氮烷主链上,生成一种单源陶瓷前驱体聚铝硅氮烷;聚合物混合型：两种聚合物即聚硅氮烷与含铝聚合物共混;然后交联裂解制备陶瓷。与无Al的Si/C和Si/C/N体系相比,SiAlCN陶瓷具有优异的抗蠕变性、更好的抗氧化性和耐腐蚀性以及更好的导热性。因此,聚合物衍生的硅铝碳氮化物(SiAlCN)陶瓷是在高温和恶劣环境中应用很有潜力的材料。     

Investigating the microstructures and properties of Mg-Al LDH film-coated Mg-Li alloy: Effect of hydrothermal temperature

Magnesia-alumina layered double hydroxide (Mg-Al LDH) films grown in situ on LA43M magnesium-lithium (Mg-Li) alloy were synthesized utilizing the hydrothermal method. Scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD) were used to characterize the surface morphologies, composition, and phase of the Mg-Al films. The corrosion resistance of the Mg-Al films was estimated via immersion experiment and hydrogen evolution test, and the tribological properties were investigated using tribological wear tests. The results showed that the thickness of the Mg-Al LDH film enhanced, and the size of the LDH sheets increased as the hydrothermal temperature raised, resulting in the improvement of the corrosion and wear resistance. When the hydrothermal temperature reached 110°C, interlayer anions were loaded the most, and the film achieved the optimal thickness. The Mg-Al LDH film had the optimum corrosion resistance and tribological properties. At this point, the weight loss of the film was 1.3560 mg·cm^–2, and the average friction coefficient was .149. It demonstrated that synthesizing Mg-Al LDH at a hydrothermal temperature of 110°C was an effective approach to improve the corrosion resistance of LA43M.     

相变介质组成对粉煤灰基高温定形复合相变材料蓄热性能的影响

分别以Al粉、Al-12Si、Al-20Si合金粉为相变介质,粉煤灰为基体材料,采用混合烧结法在空气、真空两种烧结氛围下制备金属/陶瓷基高温定形复合相变材料,探讨相变介质中硅铝相对含量及烧结氛围对材料蓄热性能的影响。结果表明:分别用三种金属粉制备复合相变材料时,Al的氧化难以避免,致使Si的相对含量均超过共晶点组成,凝固时其状态点始终处于共晶相+Si相的两相区,未被氧化的Al都转变成为Al-Si共晶相。空气中烧结有利于Al形成致密氧化膜从而阻止其进一步反应,材料的密度、相变潜热都比真空中烧结高。三种复合相变材料中,由Al粉制备的热稳定性最差,由Al-12Si合金粉制备的相变潜热、保留率最高,热稳定性及蓄热性能突出。     

Effect of different metal powder anti-oxidants on N220 nano carbon containing low carbon MgO-C refractory: An in-depth investigation

Effect of three different metal powder antioxidants, namely, Al, Si, and Mg was studied on the development of N220 nano carbon containing low carbon MgO-C refractory. The study was also extended to conventional MgO-C refractory compositions with 16% graphite content. All the refractory compositions were processed as per conventional MgO-C refractory manufacturing techniques and were evaluated for physical, mechanical, thermo-mechanical properties, oxidation resistance and static corrosion resistance against steel converter slag. Microstructural developments and in-situ ceramic phase formation in the compositions were also studied. The results show that nano carbon containing low carbon MgO-C refractory compositions have better properties than conventional composition and among the three anti-oxidants, the aluminum metal powder has shown the improved properties.     

不同铝基原料对MgO-Al-C材料性能和显微结构的影响

以烧结镁砂骨料、电熔镁砂细粉、Al粉、N220炭黑为原料,酚醛树脂为结合剂,制备MgO-Al-C材料,研究了三种铝基原料(造粒氧化铝微粉、氧化铝空心微珠、六铝酸钙)对其常温抗折强度、高温抗折强度、抗热震性及抗氧化性的影响,并借助XRD和SEM对其物相组成及显微结构进行分析。结果表明,造粒氧化铝微粉是多孔结构,可吸收热应力,加入量为1%(质量分数,下同)时,可提高材料的常温抗折强度和抗热震性,明显改善材料的抗氧化性。氧化铝空心微珠是中空结构,可缓冲热应力,加入量为3%时,可明显提高材料的常温抗折强度,并具有较高的抗热震性和抗氧化性。六铝酸钙的热膨胀系数较低,可赋予材料较好的韧性,加入量不超过5%时,样品具有较好的抗热震性。     

双重封闭对建筑用6463铝合金酒石酸氧化膜耐蚀性能的影响

为提高建筑用6463铝合金的耐蚀性能,在6463铝合金表面制备酒石酸氧化膜,然后进行热水-镍盐双重封闭.研究了双重封闭对酒石酸氧化膜的形貌、厚度及耐蚀性能的影响,并与单一热水封闭、镍盐封闭作比较.结果表明:单一封闭和双重封闭对酒石酸氧化膜的厚度基本没有影响,但封闭前后酒石酸氧化膜的形貌、成分及耐蚀性能存在差异.双重封闭...     

Improved thermal shock stability and oxidation resistance of low-carbon MgO–C refractories with introduction of SiC whiskers

This research focuses on the utilization of SiC whiskers synthesized from rice husk powders in low-carbon magnesia–carbon (MgO–C) refractories, and attempts to reduce the flake graphite content in refractories by adding synthesized SiC whiskers. The effect of the addition amount of SiC whiskers on the microstructure, mechanical properties, thermal shock stability and oxidation resistance of MgO–C refractories with different graphite content was studied. The results indicated that the introduction of SiC whiskers facilitated the generation and growth of ceramic phases in MgO–C refractories. By adding 1 wt% SiC whiskers, the graphite content could be reasonably reduced (from 5 wt% to 4 wt%), and the strength, thermal shock stability and oxidation resistance of refractories were enhanced by the synergistic effect of the introduced SiC whiskers and the generated ceramic phases, the CMOR, CCS, residual CCS, and oxidation resistance were increased by 44, 6, 12 and 27% respectively.     

AlN对Al2O3-C材料性能的影响

采用碳热还原法制备的AlN复合粉(主成分是AlN和Al2O3)部分取代Al2O3-C材料中的Al2O3微粉,研究了AlN复合粉加入量(分别为0、15%和25%)对Al2O3-C材料性能的影响。结果表明:(1)试样的显气孔率随AlN复合粉取代量的增加而增大,体积密度、常温抗折强度随AlN复合粉取代量的增加而减小;(2)AlN复合粉的引入能显著提高Al2O3-C材料的高温抗折强度;(3)添加AlN复合粉的试样经熔钢侵蚀后,在材料表面形成较连续的致密层,有利于提高材料的抗熔钢侵蚀性和冲刷性。