Key Engineering Materials Vol. 871

Abstract: These years, electronic devices and integrated circuits have a trend of miniaturization and integration with the rapid development of the information industry, higher requirements have been placed on the size, purity, and defect density of silicon wafers. More urgent demands have been placed on the mass production of electronic grade polysilicon. However, the research of electronic grade polysilicon in China is still in its infancy, it is far from meeting the requirements of mass production. This paper studies the influence of the single factor of reaction temperature on the yield of silicon, the surface morphology and power consumption of polysilicon under the certain conditions, which has some reference value for the production of electronic grade polysilicon.

Abstract: The paper provided a simple method for preparing the β-carotene reference standard from a β-carotene food additive (96%) based on high speed countercurrent chromatography (HSCCC). The obtained material was qualitatively detected by IR, NMR, MS, the results showed the material was purified β-carotene, the purity of obtained β-carotene reference standard can be as high as 99%. The prepared reference standard can be used for quality control of related health food. The provided method is simple, universal, cheap, and the sample preparation can be enlarged to g grade.

Abstract: Based on SEM, FT-IR and XRD characterization, the catalyst Pd-Fe-Co-Ce/FSC (ratio 1:1:1:3) was calcined at a temperature of 550°C and a calcination time of 3 h. The catalyst is applied to the catalytic wet oxidation treatment of difficult-to-biodegradable organic waste-water. By the characterization of the catalyst before and after the reuse, it is verified that the SEM morphologis of the catalyst changed little, and the groups contained in the catalyst characterized by FT-IR hardly changed, and the XRD characteristic peaks did not change. From the SEM photos of the catalyst before and after use, the morphology of the catalyst does not change much, and the agglomerated support on the catalyst surface is slightly reduced; the absorption peaks of the FI-IR spectrum of the catalyst before and after use are not significantly different, indicating that the functional groups contained in the catalyst have not changed significantly; After using the catalyst, compared with before use, the characteristic peak shape of each characteristic diffraction did not change significantly. The results show that the catalyst Pd-Fe-Co-Ce/FSC (ratio 1:1:1:3) revealed a stable catalyst performance in the process of CWAO for the treatment of difficult-to-biodegradable organic waste-water.

Abstract: Transition metal oxide doped two-dimensional materials, which combine the advantages of multiphase and homogeneous electrocatalysts, have attracted extensive attention in recent years. However, the electrocatalysts with single metal component can not further meet the requirements of catalytic performance. In this paper, a bimetallic organic complex, CuCo-MOF, was prepared from L-aspartic acid and copper ions and cobalt ions. The effects of temperature and metal ratio on the oxygen evolution properties of the prepared materials were investigated, and CN@CuO/Co₂O₃ nanosheets with excellent oxygen evolution electrochemical activity were optimized. The catalyst is a compound of CuO and Co₂O₃ nanoparticles doped into the carbon nitrogen matrix. A large number of homogeneous CuO and Co₂O₃ nanoparticles cooperate on the ultra-thin carbon nitrogen substrate with high conductivity, showing low initial oxygen evolution over potential and high catalytic current density. A current density of 10 mA cm^-2 can be only achieved at 1.54 V vs. RHE.

Abstract: Amine compounds are widely found in natural products, pharmaceuticals and fine chemical products. Therefore, it is of great significance to develop methods for synthesizing amine compounds. Therefore, in recent years, a new method of synthesizing amines has been developed, namely "hydrogen borrowing reaction". This article reviews the alkylation of primary alcohols and amines, the cyclization of amino alcohols to form N-heterocyclic compounds, the reaction of diols and amines to form N-heterocyclic compounds, the reaction of alcohols and sulfonamides, and the reaction of alcohols and amines containing N heteroatoms , Alcohol and ammonia gas and ammonia to produce amine by hydrogen reaction research progress.

Abstract: Pre-tensing the CFRP strip strengthening RC column can improve the strain lag of the confined concrete and avoid unloading of column in advance. The pre-stress of strip has an important influence of strengthen. Stress loss of the strip pre-tensed by using the device proposed were investigated by using an experimental test. Firstly, the reasons for the stress loss of strip were analyzed according to the working principle of the device and the strengthening procedure. Then the primary causes of the stress loss, such as friction, relaxation and removing device, were experimentally tested. The influence of the pretension, detail and sectional geometric dimension on the stress loss of the strip were studied. The results show that all three types of pre-stress losses increase significantly with the initial stress. Increasing the cross-sectional size would reduce the relaxation and unwinding losses, but it has little effect on friction losses. The influence of fillet radius on the pre-stress loss was negligible, but in order to avoid premature tearing of local CFRP caused by stress concentration, the chamfer should be made as large as possible within the thickness of concrete protective cover. The test also found that friction was the main cause of stress loss, and friction loss accounts for more than 90% of the total loss.

Abstract: Self-compacting steel fiber concrete must meet the strength standard after steel fiber is added and must have good fluidity. The test results show that the addition of steel fiber to concrete will affect the fluidity of concrete. Compared with ordinary concrete, the addition of steel fiber will improve the compressive strength and flexural tensile strength of concrete to varying degrees. The mix proportion test can be carried out in stages, i.e. the mix proportion meeting all performance indexes used is determined first, then steel fiber is added and adjusted to determine the best mix proportion.

Abstract: In order to understand the mechanical properties and force transfer law of steel-concrete composite beam deck under negative bending moment, and further guide the design. Based on a steel-concrete composite girder cable-stayed bridge, the model test of the mechanical behavior of the steel-concrete composite girder deck under the action of negative moment was carried out. The characteristics of mechanical failure and mechanical properties were analyzed.

Abstract: Calcareous sand is widely used as backfill material for land reclamation, but due to its special mechanical characteristics such as easily broken particles, calcareous sand foundation is facing more complex engineering problems. In this study, drained and undrained shear tests were carried out on calcareous sand samples from the South China Sea using K0 consolidation and isotropic consolidation conditions. It was found that the particle breakage of calcareous sand has obvious dependence on the initial consolidation stress path and drainage condition, thus showing different shear strength behavior. The particle breakage under drained shear is greater than that under undrained shear, and the particle breakage under isotropic consolidated shear is greater than that under K0 consolidated shear. The larger the particle breakage, the smaller the dilatancy and internal friction angle of calcareous sand. The dilatancy and internal friction angle of K0 consolidated specimen are larger than those of isotropic consolidated specimen. It is suggested that the actual stress path of calcareous sand should be considered in the engineering.

Abstract: Gemini surfactant acetylene glycol polyethers and polyhydrosilicone oil were used as raw materials to generate the acetylene glycol surfactants with defoaming, antifoaming properties, and polyether modification through a hydrolyzation reaction. A novel silicone surfactant based on acetylene glycol-modified polyoxysilane, which has the advantages of low surface tension and good water solubility. Its structure characterized by infrared. Finally, the new silicone surfactant prepared was emulsified with a composite emulsifier, and a new concrete defoamer was prepared by a mechanical method. The defoaming performance, foam suppression performance and surface tension were tested. The results showed that the new silicone surfactants contained functional groups of acetylene glycol and siloxane. The composite emulsifiers were Span40 and Tween60, which the HLB value was 10, the amount was 5% and the emulsification time was 30 minutes. The prepared new concrete defoamer has good defoaming and antifoaming properties with a low surface tension.