金刚石颗粒表面形成氧化铝晶须的研究

采用Ti/Al/Graphite/Diamond粉体为原料,使用自蔓延高温烧结(SHS)技术,处于空气气氛下,在金刚石颗粒的表面形成了大量Al_2O_3晶须。采用XRD、SEM并结合EDS技术分析和研究试样。研究结果表明,原料经SHS反应后,生成了Ti_2AlC、TiC、TiN、TiO和Al_2O_3。此外,在金刚石表面可形成了大量Al_2O_3晶须。提出一种金刚石表面形成了Al_2O_3晶须的反应机制,即发生SHS反应后,首先在金刚石表面形成致密的Al-Ti层,然后Al与O_2反应,形成了大量Al_2O_3晶须。     

铝对3Ti/SiC/C体系自蔓延高温合成Ti_3SiC_2的影响

采用3Ti/SiC/C粉体为原料,通过自蔓延高温合成技术制备了Ti3SiC2材料。探讨Al助剂对制备Ti3SiC2的作用。研究结果发现C-SiC-3Ti粉体能够产生SHS反应,产品由TiC、Ti5Si3和Ti3SiC2三相组成,Ti3SiC2含量约46%。添适当Al可显著促成Ti3SiC2相合成。选用3Ti/SiC/C/0.3Al粉体作原材料,产物中Ti3SiC2含量高达92.5wt%。     

自蔓延燃烧法制备AlN陶瓷粉体的研究进展

概述了自蔓延燃烧法(Self-propagating high-temperature synthesis,简称SHS)制备氮化铝(A1N)粉体的原理及方法.重点综述了纳米A1N陶瓷粉体的最新制备工艺研究进展,并对SHS法制备A1N粉体的发展进行了展望.     

自蔓延高温合成技术研究与应用的新进展

自蔓延高温合成（SHS）技术是一门新兴的学科，因其独特的优越性而吸引着各国学者进行研究。本文从研究和应用两个方面介绍了SHS的具体特点，重点分析了SHS技术在制备粉体、烧结、催化剂、强化致密化、焊接、颜料和涂层等典型的工业化实践应用的新进展，并进行了综合比较和系统归纳总结，通过分析，认为目前SHS应用存在的主要问题是如何获得高致密度的产品和怎样严格控制燃烧过程。     

自蔓延高温技术制备ZrC粉体(英文)

采用自蔓延高温合成(self-propagating high-temperature synthesis,SHS)技术,以 Zr+C 为反应体系合成了 ZrC 粉末。研究了实验参数对 SHS过程中点火电流、燃烧温度的影响。采用了 3 种碳源,研究了其对最终产物形貌及化学组成的影响。通过添加不同含量的 NaCl 作为 SHS 稀释剂,控制产物粒径及形貌。结果表明:炭黑是高温自蔓延法制备 ZrC 粉体的最佳碳源。由该体系制备的 ZrC 粉末粒径在 0.5～1 μm之间,氧含量为 0.38%。随稀释剂 NaCl 含量增加,体系燃烧温度降低,产物粒径减小。当 NaCl 含量为 30% (质量分数)时,体系燃烧温度下降至 1 810 K,产物 ZrC 粉末的粒径减小至 50 nm。     

陶瓷材料的SHS超快速致密化技术

自蔓延高温合成(self-propagating high-temperature synthesis,SHS)是一种在数秒～几十秒内即可完成的合成技术,但是直接产物是多孔状的.在SHS产物还处于高温软化状态时立即快速加压(quick pressing,QP),可以一步实现合成和致密化获得致密材料,这一技术被称为SHS/QP技术.传统的高温烧结的致密化过程主要靠原子扩散实现,SHS/QP过程如此之快,其致密化机理尚不明确.为此,探讨了SHS/OP技术制备金属陶瓷和复相陶瓷的致密化机理.研究了SHS/OP技术制备金属陶瓷、复相陶瓷和叠层复合材料的结构和工艺过程,并制备了密实材料.结果表明:基于塑性变形机理,SHS/QP技术能制备出密实、晶粒基本不长大的纳米陶瓷.     

工艺参数对自蔓燃制备氮化硅粉体的影响

采用自蔓燃高温合成方法(self-propagating high-temperature synthesis,简称SHS)合成氮化硅粉体,分析了自蔓燃高温合成氮化硅过程中氮气、温度、稀释剂与孔隙率等方面的影响。采用XRD研究相的组成,用SEM观察粉末的显微结构。研究结果表明:只要控制反应中的工艺参数,就可以采用自蔓燃得到不同相含量的Si3N4粉体;考虑到燃烧温度(Tcom),在氮化硅粉体的合成过程中,涉及到3个反应机制:低温机制,中温机制,高温机制;氮气压力下硅粉的自蔓燃合成反应,必须要引入Si3N4稀释剂,来控制反应温度和反应速度,获得不同相含量的粉体;NH4Cl在反应中分解,为反应提供了NH3,并与硅粉反应;压坯气孔率控制在30%~70%,否则反应不能进行。SHS法可以制备纯度很高的氮化硅粉体。此法较传统方法合成的氮化硅设备简单,成本低廉,纯度高,填充性好,烧结活性好。     

自蔓延高温合成La0.67Sr0.33MnO3粉体的烧结性能及巨磁效应的研究

利用自蔓延高温合成技术(self-propagating high temperature syntheris,SHS)合成La0.67Sr0.33MnO3粉体,探讨了自蔓延合成工艺对粉体结构及放电等离子体(spark plasma sintering,SPS)和普通烧结对La0.67Sr0.33MnO3粉体烧结性能和陶瓷显微结构的影响.经XRD,SEM,密度测试等结果表明:在自蔓延法合成出的物相为单一的钙钛矿型结构.SPS烧结与传统的固相烧结法相比:SPS快速烧结大大降低了传统固相法烧结温度,烧结后的晶粒大小基本均匀,烧结体致密度高.经过巨磁电子效应(colossal magnetoresistance,CMR)的测量得出,采用SPS放电等离子烧结的样品相对于普通烧结的样品,低温CMR效应有所增大.     

超细TiC粉体的制备方法及应用研究进展

结合近年TiC材料的研究进展,对超细TiC粉体的制备方法进行了综述,介绍了还原法、自蔓延高温合成法（SHS）、机械合金化法、微波法、气相反应合成法及等离子体法,简述了TiC在增强颗粒、航空航天材料及涂层材料方面的应用。     

SHS结合密实化技术制备材料进展

SHS结合密实化技术可以一步完成材料的合成与致密化过程,这是该领域研究的最新方向.本文介绍了国内外正在研究的几种典型的SHS结合密实化技术,对它们的优劣进行了分析,认为SHS/QP方法是一种有希望的材料制备技术.     

Effect of batch pelletizing on a course of SHS reactions: An overview

Such a simple technological trick as pelletizing (granulating) green powder mixtures (popular in conventional powder technology) has seldom been used in SHS technology. We have demonstrated that pelletizing green powder mixtures can markedly affect the parameters of various SHS reactions (SHS in a mode of infiltration-mediated combustion, SHS with a reduction stage, combustion of thermit mixtures, SHS in aluminum melt) and properties of their products.     

Comparative Studies on Sintering Behavior of Self-Propagating High-Temperature Synthesized Ultra-Fine Titanium Diboride Powder

Sintering behavior of nano-sized titanium diboride (TiB₂) powder prepared by a self-propagating high-temperature synthesis (SHS) technique was compared with that of the commercially available powder. The SHS-made powder showed excellent sinterability at low temperatures and a maximum of 97% densification was achieved at 2223 K, whereas the identically sintered commercial powder could only be densified to ∼86% at 2223 K. The estimated activation energies for sintering of 35±0.07 kJ/mole and 46±0.7 kJ/mole for the SHS and commercial powder, respectively, indicated the possibility of a different mechanism during sintering.     

自蔓延高温合成技术的发展与应用

自蔓延高温合成技术是20世纪后期诞生的一门新兴的前沿科学，在粉体合成及陶瓷涂层内衬的制备等方面充分显示其优越性。本文对自蔓延高温合成技术的概念、国内外基本情况进行了阐述，同时简要介绍了自蔓延高温合成的燃烧理论．对利用自蔓延合成技术进行粉体合成及陶瓷内衬钢管的应用研究等作了较为详尽的说明。     

Effect of Heating Rates on the Synthesis of Al2O3–SiC Composites by the Self-Propagating High-Temperature Synthesis (SHS) Technique

Various aspects of in situ formation of Al₂O₃–SiC composites by the self-propagating high-temperature synthesis (SHS) technique have been investigated using thermal analyses (TG/DTA) of a powder mixture (4Al, 3SiO₂, 3C) and pellets in an argon atmosphere at different heating rates. Both the reaction initiation and peak temperatures are found to increase with the heating rates. At lower heating rates, the powder samples do not reveal any exothermic peak possibly because of poor reactivity and sluggish exothermic reaction. The appearance of exothermic peaks in the DTA plots after melting of aluminum indicates reduction of silica by liquid aluminum. Conversion of aluminum is found to decrease marginally with an increase in heating rates. The apparent activation energy of the process compares well with the interdiffusion activation energy of silicon and oxygen, indicating that oxygen diffusion in Si formed at the reaction front may be the rate-controlling factor for this SHS process. From SEM studies it appears that the formation of SiC whiskers is through liquid-phase mass transfer.     

MECHANISM OF STRUCTURE FORMATION IN SELF-PROPAGATING THERMITE REACTIONS: THE CASE OF ALUMINA AS DILUENT

The mechanism of structure formation of the global reaction Fe₂O₃ + 2Al → 2Fe + Al₂O₃ under self-propagating high-temperature synthesis (SHS) conditions in the presence of alumina as diluent is investigated. The reactants in powder form are converted into products by passing through four transformation zones with different structure and composition. Some of the early stages of this reaction are explained on the basis of the mechanism proposed by Korchagin and Podergin (1979). Final products seem to be then formed as a consequence of a crystallization process from a melt. These findings may contribute to improve the manufacturing of wear and corrosion resistant SHS coatings.     

Self-Propagating High-Temperature Synthesis of Aluminum Nitride under Lower Nitrogen Pressures

The synthesis of aluminum nitride (AlN) via self-propagating high-temperature synthesis (SHS) was attempted, using aluminum powder that was mixed with AlN powder as a diluent. The AlN content in the reactant was varied over a range of 30%–70%, and the nitrogen pressure was varied over a range of 0.1–1.0 MPa. The SHS reaction that was performed using a reactant that contained 50% AlN diluent, under a nitrogen-gas pressure of 0.8 MPa, yielded the highest conversion ratio of aluminum powder to AlN powder. A mechanism for the reaction of aluminum with nitrogen gas during the SHS process was discussed, based on observations of the microstructures of the reaction zone and products.     

自蔓延高温合成技术制备TiC／Ni3Al复合材料的研究

采用ＳＨＳ工艺，从Ｔｉ，Ｃ，Ｎｉ，Ａｌ四种元素态粉末原料对ＴｉＣ／Ｎｉ３Ａｌ复合材料进行了探索研究，测定了燃烧温度变化曲线，结果表明，燃烧反应温度较高，温度变化复杂，且与ＴｉＣ的含量有关，对不同相组成的产品进行了ＸＲＤ及ＳＥＭ分析，表明在这四种元素态粉末存在的系统中，经过ＳＨＳ过程，设计的ＴｉＣ和Ｎｉ３Ａｌ相是稳定存在的两个相，合成产品呈多孔洞，疏松的开装状，ＴｉＣ晶粒细小且呈圆球状。     

Synthesis of Al3BC in air from mechanically activated Al/B/C powder mixtures

A ternary aluminum borocarbide, Al₃BC was prepared for the first time by self-propagating high-temperature synthesis (SHS) induced by mechanical activation of Al/B/C powder mixtures in air. The effect of mixing molar ratio of Al/B/C and grinding time on the formation of Al₃BC was investigated. On the other hand, Al₃BC was also formed by mechanical activation and subsequent annealing of Al/B/C=3/1/1 powder mixture. The lattice constants of Al₃BC obtained in two methods were compared.     

Advanced methods for SHS of powders developed in Krakow

History of the involvement of our laboratory in SHS research and characterization of the main ideas of this research focused on developing advanced methods of powder synthesis for macro-and nanotechnologies with the use of SHS are overviewed. By the low cost of installations and simplicity of the process, SHS over-shadows most advanced methods of synthesis and has the potential to be developed into large scale production. The mechanism of SHS reactions often differs from that of reactions at lower temperatures and due to this the particulate SHS products may have properties valuable for some specific applications. A more detailed illustration of these problems is presented for SHS-derived powders of compounds, such as SiC and Ti₃SiC₂, which have unique properties and applications. Presented at the International Conference on Historical Aspects of SHS in Different Countries, October 22–27, 2007, Chernogolovka, Moscow, Russia.     

Nitride formation during combustion of Ti-TiO2 and Ti-Al powder mixtures in air under SHS conditions

Nitride formation during SHS combustion of a micron-size titanium powder and its mixtures with additives in air was studied. It was shown that the yield of TiN Ti powder was higher for SHS combustion in air than for SHS combustion of powders of the same degree of dispersion in nitrogen. The mechanism of formation of TiN is probably determined by the reaction of the intermediate product TiO with atmospheric nitrogen. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 131–135, September–October, 2008.