Electrochemical etching using surface carboxylated graphite electrodes in ultrapure water

Electrochemical etching enables processing with an atomic-level accuracy, without deteriorating the physical properties of the workpiece; however, contamination of its surface with electrolytes is unavoidable. If it is possible to carry out electrochemical etching without using electrolytes, such a process will be applicable to electronic device manufacturing and precision nanoscale processing of semiconductor materials. In addition, this process does not require the use of chemicals, cleaning after processing or disposal of waste fluid, which results in a low-cost and environmentally friendly process. To develop an electrochemical etching process that does not require the use of electrolytes, we proposed a method in which a functional-group-modified electrode is used as the cathode. A carboxylated graphite electrode was prepared by treating a graphite electrode with sulfuric acid. Electrolysis of ultrapure water was carried out using the obtained electrode as a cathode. The results indicate that the electrolysis current obtained using the modified electrode is approximately six-fold that obtained using an unmodified electrode. Furthermore, we can etch a Cu surface conically in ultrapure water. The current efficiency increases by 70% at maximum, and the minimum current required for electrochemical etching decreases compared with that in the case of using an unmodified electrode.     

Numerical simulation of the electrodeionization (EDI) process for producing ultrapure water

A steady-state model was established to simulate EDI process for producing ultrapure water (MixEDI), the dilute compartment of which is filled with mixed cation and anion-exchange resins. By calculating the mathematical model which includes water dissociation mechanism, ionic status of ion-exchange resin, concentration polarization status and the concentration distribution of water dissociation products are obtained. The influence of water dissociation on the current efficiency, removal rate and pH value of EDI effluent is investigated. The existence of water dissociation catalyst at anion-exchange membrane (AM) makes the water dissociation current of the AM much larger than that of CM. The result is that the amount of electro-regenerated cation-exchange resins is much larger than that of anion resins. This is the reason why the removal rate of salt cation much larger than that of salt anion in EDI for producing ultrapure water. Thus, at the target percentage removal, water dissociation at AM surface is excessive and the one at CM surface is insufficient. We assume that there is also some water dissociation catalyst at CM surface. It is found that the improved water dissociation at CM could increase the percentage removal of salt anions and the current efficiency.     

Fabrication of patterned porous silicon using high-energy ion irradiation

P-type silicon has been patterned using high-energy protons beam prior to electrochemical etching in hydrofluoric acid. The ion beam selectively damages the silicon lattice, resulting in an increase in the local resistivity of the irradiated regions. It is found that the photoluminescence intensity of the irradiated regions increases with proton irradiation into a 0.02 Ω.cm resistivity p-type silicon. By immersing the etched sample into potassium hydroxide, the porous silicon is removed to reveal the underlying three-dimensional structure of the patterned area.     

Novel water treatment process — combined cationic ion-exchange bed and degasifier in a three-phase fluidized bed

A novel water treatment process, combining cationic ion exchange and bicarbonate removal in a countercurrent three-phase fluidized bed, was explored. The study was based around a laboratory scale bed. The different operating conditions and effluent quality were investigated. The results showed that concentrations of sodium and carbon dioxide in effluent decreased with increasing height of resin static layer and greater airflow velocity. The concentration of sodium and carbon dioxide in the effluent was lower than 0.1 mg/l and 5 mg/l respectively. Instantaneous conductivity that illustrated effluent quality was measured in different sections of the bed. A mathematical modeling which can simulate the changing of conductivity was built, the validity and applicability of the model for future prediction of effluent properties have been verified by the good agreement between the experimental and predicted values.     

Deposition of micron-sized particles on flat surfaces: effects of hydrodynamic and physicochemical conditions on particle attachment efficiency

An experimental study of micron-sized particle deposition on flat surfaces is presented, aimed at delineating the effects of hydrodynamic and physicochemical interactions on particle transport and attachment efficiency, and at obtaining a better understanding of the particle sticking probability, a concept employed in modelling particulate fouling of industrial heat exchangers. Dilute particle suspensions are employed in a parallel-plate-laminar-flow channel, and hydrodynamic and physicochemical conditions are systematically varied. Deposition rates are determined by optical microscopy and image analysis techniques. It is observed that if gravity forces are present (in a horizontal channel) they control deposition at low wall shear stresses. As the hydrodynamic wall shear stress increases particle deposition rates are significantly reduced due to the effect of hydrodynamic lift or drag forces inhibiting transport or attachment. In general, for hydrodynamic conditions similar to those encountered in industrial heat exchangers, it appears that the particle sticking probability is significantly lower than unity.     

氮掺杂二氧化钛光催化降解超纯净水中有机化合物

UV氧化单元是生产超纯水过程中的一个重要组成部分。然而,常规UV氧化能耗大,寻求高效节能的UV氧化方式已成为当今超纯净水净化研究热点之一。文中采用溶胶凝胶法,以钛酸四丁酯为钛前驱体,乙醇为溶剂,成功制备了TiO2薄膜。TiO2薄膜在加温条件下氨化制得了含氮TiO2。实验通过光催化降解超纯净水中乙二醇、异丙醇及尿素,考查了合成催化剂的性能。实验表明:在相同紫外光源条件下,掺氮TiO2的催化效果明显优于TiO2的催化效果。将掺氮TiO2与254 nm UV灯结合使用能达到与仅使用185 nm UV灯的同样的氧化效果,将此技术应用于超纯净水处理将会大大降低清洁水净化能量消耗及生产成本。     

Determination of the adhesion force between particles and a flat surface, using the centrifuge technique

By using a centrifuge technique, the influence of powdery material particle size on the adhesion force particle-surface was determined. In order to achieve this, the adhesion of phosphatic rock (ρ_p = 3.090 kg m^− 3) and of manioc starch particles (ρ_p = 1.480 kg m^− 3) on a steel surface were studied. A microcentrifuge that reached a maximum speed rotation of 14000 rpm and which contained specially designed centrifuge tubes was used. There tubes contained the flat surface where the test particles were deposited. The powder particles were dispersed on these disks and the particles detachment were performed using diverse centrifugal speeds. The graphics of particle percentages still adhering on the surface of the disks as a function of the applied detachment force showed that the profile of adhesion force followed a log-normal distribution. The adhesion force increased with particle size. The manioc starch particles presented adhesion forces greater than those for the phosphatic rock particles for all particle sizes studied. The results obtained were compared with the theory proposed by Derjaguin, Muller and Toporov whose theoretical adhesion presented values close to the experimental data for the phosphatic rock particles adhesion on the stainless steel surface. On the contrary, the theoretical values were lower than the experimental ones for the manioc starch particles maybe due to the small roughness of these particles, their physical properties (softer and deformable material) and/or specific chemical interactions since the organic composition of the manioc starch particles that can dominate the adhesion force. Finally, the separation distance among the surfaces in contact (Z₀) was estimated in approximately 1.0 × 10^− 9 m for the phosphatic rock and 5.0 × 10^− 10 m for the manioc starch. These results were weakly dependent on the particle size range.     

超纯水处理输送过程用的洁净型PVC管道

利用特定PVC树脂的配方和特殊制造工艺,获得了内壁光滑如镜,摩擦力和析出物均极低的洁净PVC产品毛坯,再将产品毛坯进行表面去污、消痕和杀菌等特殊工艺处理后制造出洁净型PVC产品,该产品的性价比较高.另外,对洁净型PVC管道的应用前景、适用领域及与同类产品性能比较作了介绍.     

Fabrication of porous silicon by metal-assisted etching using highly ordered gold nanoparticle arrays

ABSTRACT: A simple method for the fabrication of porous silicon (Si) by metal-assisted etching was developed using gold nanoparticles as catalytic sites. Etching masks were prepared by spin-coating of colloidal gold nanoparticles onto Si. Appropriate functionalization of the gold nanoparticle surface prior to the deposition step enabled the formation of quasi-hexagonally ordered arrays by self-assembly which were translated into an array of pores by subsequent etching in a HF solution containing H2O2. The quality of the pattern transfer depended on the chosen preparation conditions for the gold nanoparticle etching mask. The influence of the Si surface properties were investigated by using either hydrophilic or hydrophobic Si substrates resulting from piranha solution or HF treatment, respectively. The polymer coated gold nanoparticles had to be thermally treated in order to provide direct contact at the metal/Si interface which is required for the following metal-assisted etching. Plasma-treatment as well as flame annealing were successfully applied. Best results were obtained for Si substrates which were treated with HF prior to spin-coating and flame annealed in order to remove the polymer matrix. The presented method opens up new resources for the fabrication of porous silicon by metal-assisted etching. Here, the vast variety of metal nanoparticles accessible by well-established wet-chemical synthesis can be employed for the fabrication of the etching masks.     

Electrochemical reduction of silicon chloride in a non-aqueous solvent

The electrodeposition of silicon was engaged in propylene carbonate containing SiCl₄ and tetrabutylammonium chloride. Cyclic voltammograms showed the possibility of electrodeposition of Si at −3.6 V versus Pt quasi-R.E. Potentiostatic electrolysis yielded a porous and white deposit with the thickness of 50 μm at −3.6 V for 1 h. Raman spectroscopic analysis of the deposit immersed in pure propylene carbonate soon after the electrolysis confirmed that the electrodeposit was amorphous silicon. Moreover, EDX and XPS results indicated that the electrodeposited Si was so active that it was oxidized immediately in the air. Finally, the electrodeposition process of Si film is discussed based on chronopotentiometry and chronoamperometry.     

离子交换纤维在水处理中的应用研究

在研究当前相关文献资料的基础上,结合离子交换纤维表面吸附和分离功能的特点,分别对其在水处理中应用、材料制备和应用现状进行了论述。     

Fabrication of superhydrophobic surfaces with tunable water droplet adhesion force by a two-step method

In this paper, we present a convenient approach to prepare hierarchical structured superhydrophobic coatings with tunable adhesion force, composed of micro-size glass beads, nano-size SiO₂ particles and epoxy resin. Surfaces of two types with different roughness were fabricated, one type is only with single-scale roughness demonstrating lotus effect with low sliding angle, the other type is hierarchically micro-nano-structured roughness exhibiting petal effect with high adhesion force. The surface roughness is pivotal for controlling the wetting behavior and regulating the contact angle including the contact angle hysteresis. Varying the density of micro-size glass beads could adjust the roughness of the surface, which means the adhesion force of the prepared surface could be easily controlled based on the proposed method. Through variation of glass beads’ amount, the surface could be designed to pin the water droplet with different adhesion force when the surface turned upside down. The surface wettability, surface morphology, adhesion force of the prepared samples are investigated and mechanism of the Cassie-to-Wenzel state transition are discussed in detail. Furthermore, the convenient method provides a possibility for controlling surface morphology, composition and corresponding surface adhesion which could be applied to various substrates such as tile, wood, steel and fabric.     

Dynamic wetting behavior of silicon wafers in alkaline solutions of interest to semiconductor processing

Alkaline solutions based on ammonium hydroxide and quaternary ammonium hydroxides are used widely in the wet processing of silicon wafers for control of ionic and particulate impurities following etching in acidic or buffered fluoride solutions. Etched silicon is hydrophobic in nature and alkaline solutions, because of their capacity to etch silicon, will probably alter its wettability. In this paper, the wettability of silicon in choline (2-hydroxyethyl trimethyl ammonium hydroxide) and ammonium hydroxide solutions as investigated by a dynamic contact angle analysis technique is discussed. Specifically, it has been found that silicon exhibits a profound hysteresis in wettability during the first immersion/emersion cycle in dilute choline as well as in ammonia solutions Ellipsometric and XPS (X-ray photoelectron spectroscopy) analyses have shown that exposure of choline-treated surfaces to air results in the oxidation of Si to SiO₂.     

Detachment of rough particles with electrostatic attraction from surfaces in turbulent flows

The detachment of particles with coarse and fine roughnesses from surfaces in a turbulent boundary layer flow including electrostatic effects is studied. It is assumed that the real area of contact is determined by elastic deformation of asperities, and the effect of topographic properties of surfaces is included. The Johnson-Kendall-Roberts (JKR) adhesion model is used for analyzing the behavior of individual asperities. For an average Boltzmann charge distribution, the saturation charge condition as well as a fixed charge per unit mass, the Coulomb, the image, the dielectrophoretic, and the polarization forces acting on the particle in the presence of an imposed electric field are evaluated. The theories of rolling and sliding detachment are used to study the onset of removal of bumpy particles and those with fine roughness from plane surfaces. The hydrodynamic forces and torques acting on the particle attached to a wall, along with the adhesion force for the particle, are used in the model development. The minimum critical shear velocities needed to detach particles of different sizes from plane surfaces in the presence of an applied electric field are evaluated and discussed. The electric detachment of the particles is also studied and the field strength needed for particle removal is determined. It is shown that the surface charge distribution significantly affects the removal of particles from surfaces.     

Adhesion interaction in water/n-alcohol mixtures between silanized silica and polymer particles

The adhesion of polyethylene and nylon particles to silanized silica plates was investigated in water/n-alcohol (methanol, ethanol, 1-propanol, and 1-butanol) mixtures. Silica plates were treated with γ-aminopropyltriethoxysilane, methyltriethoxysilane, and perfluoroethyltrimethoxysilane. The number of particles adhering to the plate at 60 min as an apparent equilibrium adhesion value increased as a result of the silanization of silica and decreased with increasing volume ratio of n-alcohol in the water/n-alcohol mixtures. The acid-base components of the surface free energies of the substrates and liquids were decreased by the silanization of silica and by the addition of cthanol to water. The apparent equilibrium particle adhesion is discussed in terms of the total potential energies of interaction which were calculated as the sum of the electrical double layer, Lifshitz-van der Waals, and acid-base interactions, using the electrokinetic potentials and the surface free energy components. In addition, the relationship between the extent of particle adhesion and the work of adhesion was investigated. The particle adhesion in the present systems was found to be dominated by the acid-base interaction between the particle and the substrate.     

磷铵污水的综合治理

对磷铵污水状况进行解析 ,阐述磷铵污水内部循环使用和外部收集处理循环利用的具体工艺以及污水处理、治理的效果。     

Fabrication of Si heterojunction solar cells using P-doped Si nanocrystals embedded in SiNx films as emitters

Si heterojunction solar cells were fabricated on p-type single-crystal Si (sc-Si) substrates using phosphorus-doped Si nanocrystals (Si-NCs) embedded in SiN_x (Si-NCs/SiN_x) films as emitters. The Si-NCs were formed by post-annealing of silicon-rich silicon nitride films deposited by electron cyclotron resonance chemical vapor deposition. We investigate the influence of the N/Si ratio in the Si-NCs/SiN_x films on their electrical and optical properties, as well as the photovoltaic properties of the fabricated heterojunction devices. Increasing the nitrogen content enhances the optical gap E₀₄ while deteriorating the electrical conductivity of the Si-NCs/SiN_x film, leading to an increased short-circuit current density and a decreased fill factor of the heterojunction device. These trends could be interpreted by a bi-phase model which describes the Si-NCs/SiN_x film as a mixture of a high-transparency SiN_x phase and a low-resistivity Si-NC phase. A preliminary efficiency of 8.6% is achieved for the Si-NCs/sc-Si heterojunction solar cell.     

膜分离技术在氢氧化钾生产废水处理中的应用

详细介绍了膜分离技术在氢氧化钾生产废水处理中的应用情况。     

水中二氧化硅分析方法的改进

分析了传统的二氧化硅分析方法--目视比色法存在的缺陷,提出了准确测定水中二氧化硅的新方法--钼蓝比色法.结果表明,该法准确可靠,方便快捷.     

The preparation of flat H–Si(111) surfaces in 40% NH4F revisited

The reasons why ideally flat H–Si(111) surface can be prepared by NH₄F etching are investigated from correlation between AFM observations and experimental conditions used for etching. It is shown that pitting may be completely suppressed if a one side polished wafer is immersed in an oxygen free solution. An analytical electrochemical study of the (111) and rough face of the same n-Si wafer is presented to yield insight into observations.