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In this paper, the reaction sintering process was used to prepare and conduct experiments on ceramic materials. And the electrical properties and friction properties were analyzed. Density is an important factor affecting the strength of ceramic materials. Generally speaking, the room temperature performance of ceramic materials has the greatest relationship with the relative density, because pores are the location of stress concentration, which often leads to the reduction of mechanical properties. In this paper, it is found in the preparation experiment that the pore-forming agent addition amount of about 2% has the best effect. The research results of the friction and wear behavior of ceramic materials show that the load, lubrication conditions and friction pairs greatly affect the friction and wear properties of the materials. The stable friction coefficient and wear rate of the material both increase with the increase of the load. The water lubrication condition can significantly reduce the wear rate of the material, and the reduction range is two orders of magnitude, which greatly improves the wear resistance of the material. Compared with pure ceramic materials, reactive sintered composite ceramic materials have more excellent mechanical properties and tribological properties. They are a kind of potential structural ceramic materials and have broader application prospects, which are expected to replace the currently widely used ceramic materials.

In this work, we study the interfacial boundary conditions at the interface between two immiscible liquids under a laminar flow. We measure the hydrodynamic drainage forces acting on a colloid probe as it approaches a flat and smooth Teflon film coated with silicone oil films, submerged in a sucrose solution using atomic force microscopy. On Teflon substrates, silicone oil films of thickness several hundred nanometers could be stabilized, and we found the effective slip length over these to be of the order of several hundred nanometers which increases with increasing silicone oil film thickness, as expected. The fitted slip length values weakly increased with increasing shear rates. The high values of effective slip length indicate that lubricant-infused surfaces are likely to reduce drag on length scales that approach the macroscopic scales.

Molybdenum disulfide (MoS2) is widely used in practice due to its excellent lubricating properties. However, research on the tribological properties of magnetron sputtering for depositing MoS2 films remains limited. Herein, the tribological properties of MoS2 films were investigated in detail through a series of characterization and friction coefficient tests. MoS2 films were deposited onto silicon substrates by magnetron sputtering under different radio-frequency powers (Prf). With increased Prf, the crystallinity of the films gradually increases, whereas the friction coefficient initially decreases and then increases. Prf also affects the chemical composition, surface morphology, and grain size of MoS2 films. At Prf = 300 W, the film surface is dense and smooth, the grain distribution is uniform. Moreover, the films have superior tribological properties and low friction coefficient, which can be attributed to the weak van der Waals force among MoS2 layers and the microscopic morphology of the films. All these results indicate that by reasonably controlling the preparation parameters, MoS2 films with excellent tribological properties can be prepared by magnetron sputtering.

Cu3N/MoS2 heterojunction was prepared through magnetron sputtering, and its optical band gap was investigated. Results showed that the prepared Cu3N/MoS2 heterojunction had a clear surface heterojunction structure, uniform surface grains, and no evident cracks. The optical band gap (1.98 eV) of Cu3N/MoS2 heterojunction was obtained by analyzing the ultraviolet-visible transmission spectrum. The valence and conduction band offsets of Cu3N/MoS2 heterojunction were 1.42 and 0.82 eV, respectively. The Cu3N film and multilayer MoS2 formed a type-II heterojunction. After the two materials adhered to form the heterojunction, the interface electrons flowed from MoS2 to Cu3N because the latter had higher Fermi level than the former. This behavior caused the formation of additional electrons in the Cu3N and MoS2 layers and the change in optical band gap, which was conducive to the charge separation of electrons in MoS2 or MoS2 holes. The prepared Cu3N/MoS2 heterojunction has potential application in various high-performance photoelectric devices, such as photocatalysts and photodetectors.

Lubricant-infused surfaces have attracted great attention recently and are described as slippery liquid-infused porous surfaces (SLIPS). Here, we measured the hydrodynamic drainage forces on SLIPS by colloid probe atomic force microscopy (AFM) and quantified the effective slip length over a nanothin silicone oil layer on hydrophobized [octadecyltrichlorosilane (OTS)-coated] silicon wafers. The thickness of a stable silicone oil film on OTS-Si under sucrose solution was determined to be 1.8 ± 1.3 nm and was found to induce an average effective slip length of 29 ± 3 nm, very close to that of an uninfused OTS substrate. These relatively low values of effective slip are confirmed by the relatively large macroscopic roll-off angle values of water droplets on the same substrates. Both nano- and macroscale results reflect the immobilized nature of a silicone oil layer of thickness around 2 nm within an underlying monolayer. These results have important implications in the design of drag-reducing coatings using lubricant infusion.

In this work, TiO2/Cu3N composite films were prepared by using magnetron sputtering. Results show that the optical band gap of the composite films can be effectively controlled by changing the preparation parameters, and the optical band gap of the composite films is lower than that of the TiO2 films (approximately 3.0 eV). The TiO2 in the composite films mainly appears as anatase phase, and the nano-Cu3N films prepared under the condition of r=1/4 promoted the formation of TiO2 effective electron trap on the surface of the composite films. In terms of degradation of methyl orange solution, the degradation rate of TiO2/Cu3N composite film is higher than that of pure TiO2 film, which can reach 99.2 % (using mercury lamp for 30 min). The nano-Cu3N grain inserted to TiO2 is beneficial to the conversion of Ti4+ to Ti3+, which significantly improves the photocatalytic reduction activity of the films. The TiO2/Cu3N composite films has an excellent catalytic activity and potential application prospects in wastewater treatment.

TiO2 possesses a wide forbidden band of about 3.2 eV, which severely limits its visible light absorption efficiency. In this work, copper nitride (Cu3N) films were prepared by magnetron sputtering at different gas flow ratios. The structure of the films was tested by scanning electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscope. Optical properties were investigated by UV-vis spectrophotometer and fluorescence spectrometer. Results show that the Cu3N crystal possesses a typical anti-ReO3 crystal structure, and the ratio of nitrogen and Cu atoms of the Cu3N films was adjusted by changing the gas flow ratio. The Cu3N films possess an optical band gap of about 2.0 eV and energy gap of about 2.5 eV and exhibit excellent photocatalytic activity for degrading methyl orange (degradation ratio of 99.5% in 30 min). The photocatalytic activity of Cu3N mainly originates from vacancies in the crystal and Cu self-doping. This work provides a route to broaden the forbidden band width of photocatalytic materials and increase their photoresponse range.

The purpose of the vibration test of spacecrafts is to assess their adaptability to low-frequency vibration environment during lift-off. This paper gives the simulation of the satellite ground vibration test (GVT) and the state of the satellite along with rocket during lift-off. The simulation results of these two states are compared on condition that the lateral vibration of satellite/launching vehicle (S/LV) interface is the same. It is shown that the dynamic responses of satellite vertex are totally different. This is because there is angular motion of S/LV interface during lift-off, but in the GVT, the angular motion is restrained. By means of numerical simulation of the lift-off state, the angular motion related to the translation motion of S/LV interface can be determined. Then, using this angular motion as supplementary condition to simulate the vibration test, the calculated dynamic responses of satellite vertex are identical with the lift-off state. It demonstrates that supplementing angular motion condition is an effective method to improve spacecraft ground vibration test more identically with the real lift-off environment. Furthermore, it is useful for the application of the multi-degree-of-freedom shaking table, and provides the basis for test condition requirement.

We developed a stable spread-sheet algorithm for the calculation of the hydrodynamic forces measured by colloid probe atomic force microscopy to be used in investigations of interfacial slip. The algorithm quantifies the effect on the slip hydrodynamic force for factors commonly encountered in experimental measurements such as nanoparticle contamination, nonconstant drag force due to cantilever bending that varies with different cantilevers, flattening of the microsphere, and calibration at large separations. We found that all of these experimental factors significantly affect the fitted slip length, approximately in the order listed. Our modeling is applied to fit new experimental data reproducibly. Using this new algorithm, it is shown that the fitting of hydrodynamic theories to experimental data is reliable and the fitted slip length is accurate. A "blind test" protocol was developed that produces a reliable estimate of the fitting error in the determination of both the slip length and spring constant. By this blind test, we estimate that our modeling determines the fitted slip length with an average systematic error of 2 nm and the fitted spring constant with a 3% error. Our exact calculation of the drag force may explain previous reports that the fitted slip length depends upon the shape and spring constant of the cantilever used to perform the measurements.

The coupling effects among lateral mode, longitudinal mode and torsional mode of a launch vehicle cannot be taken into account in traditional dynamic analysis using lateral beam model and longitudinal spring-mass model individually. To deal with the problem, propellant analogy methods based on beam model are proposed and coupled mass-matrix of liquid propellant is constructed through additional mass in the present study. Then an integrated model of launch vehicle for free vibration analysis is established, by which research on the interactions between longitudinal and lateral modes, longitudinal and torsional modes of the launch vehicle can be implemented. Numerical examples for tandem tanks validate the present method and its necessity.

In the past decade, the slip of simple liquids on solid surfaces has been demonstrated by many groups. However, the slip of liquids on wettable surfaces is heavily debated. Using colloid probe atomic force microscopy (AFM), we found the slip length of di-n-octylphthalate in a symmetric wettable system (silica) to be around 11 nm, which raises the question of what the measured slip length in an asymmetric hydrophilic-hydrophobic system would be. To answer this question, we investigated liquid slip in one symmetric nonwettable system (hydrophobic DCDMS or OTS) and in one asymmetric hydrophilic (silica)-hydrophobic (DCDMS) system by the same method at driving velocities of between 10 and 80 μm/s. The slip results obtained from the three systems are in agreement with each other, and this comparison provides a means to self-assess the accuracy and reproducibility of the measured force curves and the fitted slip length in our systems. Furthermore, this method provides access to reliable values of the actual slip length on any investigated flat surface in an asymmetric system, avoiding the difficulty of preparing a symmetric probe/flat surface system in a colloid probe AFM force measurement.

We present experimental evidence and theoretical models that demonstrate that the slip length, which is the departure from the hydrodynamic no-slip boundary condition, cannot be constant as commonly assumed, but must decrease with increasing shear rate to avoid an unphysical divergence in the velocity of the fluid adjacent to the surface at small separations. The molecular origin of the shear rate dependence of the slip length is discussed. A new theoretical model for slip (the saturation model) is obtained, and it is shown to describe accurately colloid probe atomic force microscopy force measurements for all separations down to a few nanometers in two partially wetting situations (di-n-octyl phthalate on silanized silicon and bare silicon). Previous observations of slip length increasing with shear rate are explained as due to an imprecise calculation of the drag force on the cantilever. A new way of plotting experimental data is also presented, which provides a useful way to illustrate the slip length dependence on the shear rate.

Here we report a new study on the boundary conditions for the flow of a simple liquid in a confined geometry obtained by measuring hydrodynamic drainage forces with colloid probe atomic force microscopy (AFM). In this work, we provide experimental data obtained using a best practice experimental protocol and fitted with a new theoretical calculation (Zhu, L.; Attard, P.; Neto, C. Langmuir 2010, submitted for publication, preceding paper). We investigated the hydrodynamic forces acting on a silica colloid probe approaching a hydrophobized silicon surface in a single-component viscous Newtonian liquid (di-n-octylphthalate), a partially wetting system. The measured average slip lengths were in the range of 24-31 nm at approach velocities of between 10 and 80 μm/s. Using our experimental approach, the presence of nanoparticle contaminants in the system can be indentified, which is important because it has been shown that nanoparticles lead to a large apparent slip length. Under our stringent control of experimental conditions, the measurement of the slip length is reproducible and independent of the spring constant of the cantilever.