添加剂对Al2O3／BN可加工陶瓷性能的影响

采用Si3N4和SiC作为Al2O3／BN可加工陶瓷的添加剂，考察了添加剂种类和含量对材料力学性能及可加工性能的影响。研究表明，2种添加剂均对调节体系中由于热膨胀失配所引起的人的内应力起到积极的作用。材料的抗弯曲强度随添加剂含量的增加而提高，同时可加工性能略有降低。尤其是Si3N4的加入使体系在热压烧结过程中原位反应生成液相x-Sialon，显著降低了烧结温度，促进材料的致密化。     

硼铸铁缸套激光表面熔凝组织和性能的研究

为了提高硼铸铁缸套的耐磨性能，对硼铸铁气缸套进行激光熔凝处理。利用扫描电子显微镜观察了激光熔凝处理后的显微组织。利用显微硬度计检测了激光熔凝组织的显微硬度，同时进行了以GCr15钢标准环为配副的环块磨损试验。研究结果表明，硼铸铁经激光熔凝处理后得到了共晶莱氏体 马氏体组织，而且激光熔覆层厚度可控，组织和性能稳定，熔凝强化表层显微硬度达到800-1200HV0.2。磨损试验结果显示，激光熔凝处理后，磨损截面积比未处理的试样减小了44.4%，从而表明激光熔凝处理是提高硼铸铁缸套耐磨性能的有效手段。     

硼铸铁等离子相变强化层的组织与性能

采用等离子束对硼铸铁进行了表面强化,对等离子强化层的显微组织、显微硬度和耐磨性进行了研究。结果表明:硼铸铁经等离子束淬火处理后,其强化层的组织为隐针马氏体+残余奥氏体+片状石墨+硼化物,硬度为未处理的2￣3倍,强化层的显微硬度随深度呈非线性关系,最高硬度达1 000 HV0.1。且随工作电流的增加,强化层的深度增加,表面硬度下降,次表层硬度增大且硬化层的耐磨性大幅度提高。     

An Investigation of Grinding with Electroplated CBN Wheels

Grinding of hardened bearing steel with electroplated CBN wheels was Investigated with particular attention to how the wear of the abrasive grains affects the wheel topography and grinding performance during the wheel ire. Power, surface roughness, and wheel topography data were obtained throughout the wheel life for internal cylindrical grinding. Dulling of CBN gratis by attrition was found to cause an increase in the grinding power, but the degree of dulling was restricted mainly by grain fracture and also by grain pullout. Grain fracture and pullout had a much smaller effect on the progressive increase in active grain density, which caused the surface roughness to progressively decrease. Wheel failure tended to occur by stripping of the abrasive layer when the radial wear reached about 70% - 60% of the grain dimension     

Surface Growth of Boron Nitride Nanotubes through Boron Source Design

Boron nitride nanotubes (BNNTs) are promising materials due to their unique physical and chemical properties. Fabrication technologies based on gas-phase reactions reduce the control and collection efficiency of BNNTs due to reactant and product dispersion within the reaction vessel. A surface growth method that allows for controllable growth of BNNTs in certain regions using a preburied boron source is introduced. This work leverages the high solubility of boron in metals to create a boronized layer on the surface which serves as the boron source to confine the growth of BNNTs. Dense and uniform BNNTs are obtained after loading catalysts onto the boronized substrate and annealing under ammonia. Confirmatory experiments demonstrate that the boride layer provides boron for BNNTs growth. Furthermore, the patterned growth of BNNTs is realized by patterning the boronizing region, demonstrating the controllability of this method. In addition, the Ni substrate with BNNTs growth exhibits better performance in corrosion resistance and thermal conductivity than pure Ni. This study introduces an alternative strategy for the surface growth of BNNTs based on boron source design, which offers new possibilities for the controllable preparation of BNNTs for various applications.     

硼掺杂球磨SiGe合金的热电性能

SiGe合金热电材料作为一种传统的高温热电材料一直以来受到广泛关注。本研究通过B在球磨SiGe合金中的P型掺杂,有效增加了材料的载流子浓度,优化材料的电学性能。通过球磨降低材料的晶粒尺寸,增强晶界对声子的散射,降低材料的晶格热导率。另外,B掺杂使点缺陷散射和载流子-声子散射得到增强,材料的晶格热导率进一步降低。在室温时,Si_(0.8)Ge_(0.2)B_(0.04)的晶格热导率为~4Wm~(-1) K~(-1)。由于掺杂后电导率提高,热导率降低,因此热电优值zT得到了提高。在850K时,Si_(0.8)Ge_(0.2)B_(0.04)的最大热电优值为0.42,与Si_(0.8)Ge_(0.2)B_(0.002)的样品相比,其优值提高了2.5倍左右。     

化学气相沉积法制备氮化硼纳米管的研究进展:反应装置、气源材料、催化剂

氮化硼纳米管(BNNTs)具有优良的耐高温、抗氧化、防辐射、绝缘和导热性能,因此,在航空航天、辐射屏蔽、热界面材料以及深紫外发射等领域具有潜在的应用前景。然而,高品质BNNTs的可控制备和批量生产仍然是学术和工业界的重大挑战。在BNNTs的众多制备方法中,化学气相沉积法(CVD)是最有潜力实现其可控制备的方法之一。但是,科学家们对于CVD法制备BNNTs的催化机理和影响因素尚未形成共识。鉴于此,文章从反应装置、氮源、硼源和催化剂4个方面对CVD法制备BNNTs进行了综述,并系统总结了相应的规律。在此基础上,分析了目前BNNTs可控制备中存在的问题,并对CVD法在BNNTs可控制备中的作用进行了展望,以期对今后BNNTs的制备起到借鉴作用。     

Investigation on the cutting quality characteristics of abrasive water jet machining of AA6061-B4C-hBN hybrid metal matrix composites

Aluminum metal matrix composites (AMMCs) explicitly show better physical and mechanical properties as compared to aluminum alloys and results in a more preferred material for a wide range of applications. The addition of reinforcements embargo AMMCs employment to industry requirements by increasing order of machining complexity. However, it can be machined with a high order of surface integrity by nonconventional approaches like abrasive water jet machining. Hybrid aluminum alloy composites were reinforced by B₄C (5–15?vol%) and solid lubricant hBN (15?vol%) particles and fabricated using a liquid metallurgy route. This research article deals with the experimental investigation on the effect of process parameters such as mesh size, abrasive flow rate, water pressure and work traverse speed of abrasive water jet machining on hybrid AA6061-B₄C-hBN composites. Water jet pressure and traverse speed have been proved to be the most significant parameters which influenced the responses like kerf taper angle and surface roughness. Increase in reinforcement particles affects both the kerf taper angle and surface roughness. SEM images of the machined surface show that cutting wear mechanism was largely operating in material removal.     

Recent Advances on 3D Printing Technique for Thermal‐Related Applications

Advances in ink formulation and printing techniques make producing material systems with new and versatile characteristics and functionalities possible. Additive manufacturing or 3D printing enables fabricating complex structures at a faster production rate using different types of materials for various applications. Recently, 3D printing methods are being studied for thermal‐related applications. In this paper, the authors review recent progress of materials and printing techniques for thermal application devices using composite materials.