Search

In this paper, the dry cutting performance of Al2O3/TiC-based ceramic composites with nanoCaF2 was studied. Compared with the Al2O3/TiC ceramic tool, the Al2O3/TiC/CaF2 ceramic tool has lower cutting force, cutting temperature and surface roughness when milling 40Cr hardened steel. Three cutting parameters of cutting speed, feed per tooth, and cutting depth were used to conduct orthogonal experiments to study its changing trend. Through testing of cutting force, cutting temperature and surface roughness, and by comparison with ceramic tools without nanosolid lubricant added, the order of influence of three cutting parameters on cutting force, cutting temperature and surface roughness was obtained. The experimental results showed that the cutting force, cutting temperature and surface roughness of Al2O3/TiC/CaF2 ceramic tools containing nanoCaF2 werebetter than those of Al2O3/TiC ceramic tools. The cutting force, the cutting temperature, and the surface roughness were respectively reduced by 16.5%, 25.8% and 43% compared to when no solid lubricant was added. In addition, after adding solid lubricant, the effect of cutting depth on cutting force was significantly reduced. The average friction coefficient of the tool rake surface was 31.1% lower than that of ceramic tools without solid lubricant. In order to explain this phenomenon, through scanning electron microscopy (SEM) scanning and energy spectroscopy (EDS) elemental analysis, the wear reduction mechanism of solid lubricants was analyzed, that is, during the cutting process, nanosolid lubricants precipitated and formed lubricating film on the rake surface of the tool to reduce the friction coefficient. This was also the main reason for reducing the cutting temperature.

First-principle calculation is carried out on Al2O3(012)/SiC(310) interface model. It can be concluded from the electronic density and population analysis that Al-C and O-Si located at grain boundary primarily contribute to the interface bonding strength and creep resistance property. The electronic charges in grain boundaries and grains are compared with each other. And the valence electrons are found to be redistributed. The relationship of all kinds of chemical bonds in grains and grain boundary of the interface model is analyzed. Also the toughening mechanism of Al2O3/SiC multi-phase ceramic tool materials is explained in nano-scale.

Aiming at the low mechanical property of existing self-lubricating ceramic cutting tool material, a new Al2O3 based nanomicro composite gradient self-lubricating ceramic tool material was developed by applying the design concept of nanomicro composite. The self-lubricating ceramics was composed of ceramic matrix and self-lubricating component, and was prepared by hot pressing technology at a hot-pressing temperature of 1650°C, pressure of 30MPa, and duration of 15min. The model of gradient ceramic tool material is symmetrical composition distribution, and the compositional distribution n and layer number are 1.8 and 7, respectively. The result shows that the interfaces between layers are bonded well and no cracks or defects can be observed. Compare with the homogeneous material, the flexural strength, hardness and fracture toughness of Al2O3 based graded material increase by 74%, 5.2% and 3.9%, respectively.

A new nanomicro composite self-lubricating ceramic tool material was prepared with vacuum hot pressing technique. The effect of nanoAl2O3 powders on the microstructure and mechanical properties of nanomicro composite self-lubricating ceramic tool material was investigated. With the increase of nanoAl2O3 content, the hardness and fracture toughness first up then down. When the nanoAl2O3 content is 4 vol.%, the flexural strength, hardness and fracture toughness reaches 562 MPa, 8.46 MPa·m1/2 and 18.95 GPa, respectively. The microstructure and mechanical property of nanomicro composite self-lubricating ceramic tool material can be improved by the grain refinement strengthening of nanoAl2O3.

TiB2/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool material was prepared by vacuum hot-pressing technique. The mechanical properties were tested and compared. The best flexural strength, fracture toughness and Vickers hardness of the tool material were 678MPa, 4.75MPa·m1/2 and 15.1GPa, respectively. The microstructure was analyzed by thermal field emission scanning electron microscope (SEM). TiB2 nanoparticles were obviously observed in the ceramic matrix. It suggested that the developed TiB2/WC/h-BN micro-nano composite gradient self-lubricating ceramic tool materials will have potential application in dry machining.

Ti (C,N)/ZrO2/WC nanocomposite cermet die materials were fabricated by vacuum hot pressing process, the materials have better comprehensive mechanical properties. The friction and wear properties of Ti (C,N)-based nanocomposite cermet die materials were studied, and the worn surfaces microstructure were observed and analysed by SEM and XRD. The experimental results showed that when the rotate speed was higher, the coefficient of friction of the developed cermet die material, which is 0.3-0.4, was lower than that without the addition of nanoZrO2 and micrometer WC. The main wear mechanisms were abrasive wear, oxidation wear and adhesive wear.

The development status of self-lubricating tool materials was reviewed in the present study, as well as the five basic types of self-lubricating tool and the current situation of nanometer materials in ceramic cutting tool. Based on these, the design idea of the functional gradient materials and nano-micro composite materials was introduced into the self-lubricating ceramic cutting tool materials, in order to develop new self-lubricating ceramic cutting tool materials with both good mechanical and frictional properties.

The design concept of functionally graded materials was first introduced into the development of self-lubricating ceramic cutting tool materials. An Al2O3/TiC/CaF2graded self-lubricating ceramic cutting tool material was designed and fabricated. Mechanical properties were evaluated by comparing with those of Al2O3/TiC/CaF2homogeneous self-lubricating ceramic cutting tool material. The results showed that the Al2O3/TiC/CaF2graded self-lubricating ceramic cutting tool material had superior performance to the counterpart. Graded self-lubricating ceramic cutting tool materials are bound to have promising prospect in the field of high speed dry machining.

A new ZrO2 nano-composite ceramic tool and die material was prepared with vacuum hot pressing technology. The friction and wear behaviors of ZrO2 nano-composite ceramic tool and die materials in sliding against 45 chilled steel rings under dry friction were investigated by using an MMW-1A abrasion wear tester. The mechanical properties and the friction and wear properties of the composites with various compositions and contents were studied. It is indicated that the changing trends of the wear rate and the mechanical properties of the composites with the change of TiB2 and Al2O3 contents are roughly the same, but the friction coefficient is not obviously. The friction and wear properties and the mechanical properties are finer when the TiB2 and Al2O3 content is both 10%.

In this paper, the effects of addition of solid lubricants on mechanical properties, tribological properties and cutting performance of ceramic cutting tool materials were analyzed. The problem that existing homogeneous self-lubricating ceramic cutting tool materials were not available to possess rational combination of antifriction and antiwear properties was pointed out. The main methods to acquire graded self-lubricating materials were discussed. The design concept and research prospect of graded self-lubricating ceramic cutting tool materials were proposed, which would have promising applications in the field of high speed cutting.

Recent research progresses of design technologies for functionally gradient ceramic materials (FGCMs) at home and abroad are reviewed. The determination and application of component distribution model, micromechanical model, materials properties, distribution exponent, layer number and thickness, and thermal stress simulation, etc. have been analyzed and investigated emphatically. Problems existed are discussed and future design perspective of functionally gradient ceramic materials are pointed out.

Polyfluorenes containing Ir(III) complexes in the main chain are demonstrated to have promising application in a polymer memory device. A flash-memory device is shown whereby a polymer solution is spin-coated as the active layer and is sandwiched between an aluminum electrode and an indium tin oxide electrode. This device exhibits very good memory performance, such as low reading, writing, and erasing voltages and a high ON/OFF current ratio of more than 105. Both ON and OFF states are stable under a constant voltage stress of −1.0 V and survive up to 108 read cycles at a read voltage of −1.0 V. Charge transfer and traps in polymers are probably responsible for the conductance-switching behavior and the memory effect. The fluorene moieties act as an electron donor and Ir(III) complex units as the electron acceptor. Furthermore, through the modification of ligand structures of Ir(III) complex units, the resulting polymers also exhibit excellent memory behavior. Alteration of ligands can change the threshold voltage of the device. Hence, conjugated polymers containing Ir(III) complexes, which have been successfully applied in light-emitting devices, show very promising application in polymer memory devices.

In this paper, back propagation neural network was used in the optimum design of the hot pressing parameters of an advanced ZrO2/TiB2/Al2O3 nanocomposite ceramic tool and die material. The BP algorithm could set up the relationship well between the hot pressing parameters and mechanical property of nanocomposite ceramic tool and die materials. After analyzed the predicted results, the best predicted results were the sintering temperature was 1420°C and the holding time was 60min. Under these hot pressing parameters, the best flexural strength and the best fracture toughness of the material could be obtained.

A new ZrO2 nano-composite ceramic tool and die material was prepared with vacuum hot pressing technique. The effects of sintering parameters on the nano-composite ceramic tool and die materials were studied. The results indicated that the mechanical properties of ZrO2 nano-composite ceramic tool and die material with the additions of TiB2 and Al2O3 are higher than that of the pure ZrO2 ceramic material. Sintering at 1100 for 120min could improve the density and mechanical properties of ZrO2 nano-composite ceramic material. The flexural strength, fracture toughness and hardness with the optimum sintering parameters can reach 878MPa, 9.54MPa•m1/2 and 13.48GPa, respectively, obviously higher than that with non-optimum sintering parameters.

In this paper, the two hybrid algorithms of back propagation artificial neural network and genetic algorithm were used in the optimum design of the hot pressing parameters of an advanced ZrO2/TiB2/Al2O3 nanocomposite ceramic tool and die material. Compared with the BP algorithm, the predicted results of hybrid algorithm indicated that the combination algorithm can offer a robust and efficient way for the fabrication process design of ceramic tool and die materials.

In recent, the development of new die materials is one of the important topics in the field of die research. In this paper, effects of nano-ZrO2 addition on the microstructure and mechanical properties of Ti(C,N)-based cermets were studied. The newly developed Ti(C,N)-based cermet die materials with different contents of nano-ZrO2 of 0~25wt% were prepared by hot pressing technique under vacuum atmosphere at 1450°C for 30min. Moreover, the microstructure of this Ti(C,N)-based cermet die materials was observed by environmental scanning electron microscope. It indicates that the comprehensive mechanical properties can reach the optimum when the weight percent of the nano-ZrO2 is 10%. The corresponding flexural strength and fracture toughness is 967 MPa and 13.62 MPa•m1/2, respectively which is approximately 65% and 110% higher than that of the cermet without nano-ZrO2 addition. It suggests that the addition of nano-ZrO2 can improve the mechanical properties especially the fracture toughness and flexural strength of Ti(C,N)-based cermet die materials.

We investigate the memory properties of the ITO/graphene oxide/Al diodes. It is found that the devices show different memory behaviors with the diverse geometry and thickness of Al. When the thickness of the Al electrode is relatively thick, the device of the cross-point Al electrode shows a three-level memory effect, and the counterpart device of the cross-bar Al electrode exhibits a volatile static random access memory effect. When the thickness of the Al electrode is thinner, the above devices demonstrate a flash memory effect. The different memory behaviors of ITO/GO/Al diodes are ascribed to the mode and degree of reduction and oxidation of GO.

We demonstrated write-once-read-many-times (WORM) memory devices based on graphene oxide (GO) film sandwiched between ITO and LiF/Al electrode. The devices showed irreversible electrical transition from the low conductivity (OFF) state to the high conductivity (ON) state and the ON/OFF current ratio between the conductivities of two states was over 5.7 × 104. The results of I-V data, AFM and SEM images indicated that the WORM memory characteristics of GO diodes were mainly attributed to charge trapping at GO layers and interfacial properties between GO and LiF/Al electrode.

We have fabricated ZnO-based thin-film transistors (TFTs) by low-cost ultrasonic spray pyrolysis. The devices exhibit high saturation mobility of about 0.6 cm2/Vs and on-off current ratio of 105. The electrical characteristics of ZnO-based TFTs show that ultrasonic spray pyrolysis technique can be used as a promising approach to attain high-performance electronic devices. Furthermore, the deposition techniques make the operating process attractive for flexible electronics.