氢氟酸腐蚀硅酸盐矿物的实验研究

采用锂辉石为原料实验研究了氢氟酸腐蚀反应硅酸盐矿物的工艺条件,并初步探讨了腐蚀反应机理,结果表明在反应温度为100℃,反应时间为1h的条件下,完全腐蚀破坏每克锂辉石晶体结构约需要40%的氢氟酸2.5ml,腐蚀反应主要生成Li_3AlF_6、Al(OH)_3等物质。     

浮法玻璃组成对化学稳定性的影响

Merey(1954年)Bacon(1968年)和Eitel(1954、1965、1976)等人的许多实验都观察到玻璃组成对化学稳定性的影响,这些实验大都在稳定的溶液中进行.在PH值约为1到9的溶液中,PH值的高低随玻璃和水反应的程度而改变.在二元碱硅酸盐玻璃中,当钠的含量增加时,其扩散系数亦增大(Terai和Hayami,1975年),从而也就增加了和水反应的速率.甚至在古代人们就知道二元碱硅酸盐易受水侵蚀;而增加钙、镁氧化物会改善化学     

酸沥泸纳硅酸盐玻璃制造高硅氧玻璃纤维性能的研究

以纯碱和石英砂为主要原料制备钠硅酸盐原始玻璃纤维,经酸沥滤、水洗、烘干、烧结等工艺处理后,得到SiO2含量达96%以上的高硅氧玻璃纤维.本文研究了钠硅酸盐原始玻璃纤维的玻璃组分、不同浓度的酸沥滤玻璃纤维的离子交换反应进程,酸沥滤、水洗和烧结等工艺条件对纤维性能的影响.研究结果表明,原始玻璃组分中,随着钠含量的增加,原始玻璃纤维化学稳定性迅速降低,制造的高硅氧纤维强度下降,原始组分中引入少量氧化铝有利于提高高硅氧玻璃纤维的强度.提高酸溶液温度,能够加快酸沥滤反应速度,缩短反应时间.酸沥滤及水洗烘干后,高硅氧纤维呈封闭的多孔结构,在高温下开始收缩,高温收缩量较低,纤维的强度随着热处理温度的提高而提高,但1100℃高温强度低于无碱和硼硅酸盐玻璃制造的高硅氧玻璃纤维.     

水杨酸溶液萃取转炉钢渣中硅酸盐相的研究

研究了水杨酸-甲醇(SAM)溶液萃取钢渣中硅酸盐相的可行性,分析了钢渣比表面积、溶解时间和水杨酸浓度对萃取硅酸盐相量的影响,利用XRF和XRD分别测定了萃取后残渣的化学组成和矿物成分,以判别SAM溶液萃取硅酸盐相的效果.结果表明:常温下,5g比表面积为600m/kg的钢渣,经300mL SAM溶液(水杨酸浓度为0.2g/mL)萃取3h,钢渣中的硅酸盐相可完全溶解,其他矿物不溶或溶解甚微.分析指出,硅酸盐相溶解于SAM溶液的原因是由于水杨酸电离出的配体(HO-C6H4-COO-)与矿物表面阳离子(Ca2 )生成的络合物,通过键极化作用削弱Si-O键的稳定性,从而降低了硅酸盐溶解活化能.     

氢氟酸生产废酸制氟硼酸钾工艺研究

为充分利用氢氟酸生产过程中副产废酸中12％（质量分数）的有效氢氟酸，对其代替工业氢氟酸（质量分数30％）生产氟硼酸钾的可行性进行了分析、研究、探讨。经过试验证明先用化学计量的硼酸与30％（质量分数）氢氧化钾反应制成偏硼酸钾溶液，偏硼酸钾溶液再与废酸反应制得氟硼酸钾的工艺是完全可行的，实施后每年可回收氢氟酸120t（以100％计），具有很大的经济效益。     

浅谈硼硅酸盐玻璃的应用现状和发展趋势

硼硅酸盐玻璃具有良好的热稳定性和化学稳定性,已在仪器玻璃、器皿玻璃等领域得到了广泛应用;随着玻璃熔制工艺和耐火材料的发展,硼硅酸盐玻璃将在更多的领域得到应用.本文结合实际生产和应用情况,概括和总结了硼硅酸盐玻璃的应用现状和发展趋势.     

酸沥滤钠硅酸盐玻璃制造高硅氧玻璃纤维性能的研究

以纯碱和石英砂为主要原料制备钠硅酸盐原始玻璃纤维，经酸沥滤、水洗、烘干、烧结等工艺处理后，得到SiO2含量达96％以上的高硅氧玻璃纤维。本文研究了钠硅酸盐原始玻璃纤维的玻璃组分、不同浓度的酸沥滤玻璃纤维的离子交换反应进程，酸沥滤、水洗和烧结等工艺条件对纤维性能的影响。研究结果表明，原始玻璃组分中，随着钠含量的增加，原始玻璃纤维化学稳定性迅速降低，制造的高硅氧纤维强度下降，原始组分中引入少量氧化铝有利于提高高硅氧玻璃纤维的强度。提高酸溶液温度，能够加快酸沥滤反应速度，缩短反应时间。酸沥滤及水洗烘干后，高硅氧纤维呈封闭的多孔结构，在高温下开始收缩，高温收缩量较低，纤维的强度随着热处理温度的提高而提高，但1100℃高温强度低于无碱和硼硅酸盐玻璃制造的高硅氧玻璃纤维。     

玻璃和涂层的液相反应工艺

由溶液(无论是点溶液或胶体溶液)无机合成破璃——特别是某些硅酸盐玻璃及其类似制品的新工艺,能够大幅度地降低反应温度。本来玻璃是采用熔化或烧结的方法制造,如今人们正在研究高纯玻璃的液相合成工艺。 从溶液中制备玻璃的方法有:(1)溶液蒸发、135℃干燥并热处理;(2)从饱和的溶液中析出的粉状物料,在热的隋性基板上形成玻璃薄膜;(3)快速     

玻璃的表面侵蚀

研究玻璃的侵蚀,常使用溶液分析和失重等传统方法.但欲获悉受蚀后从玻璃表面剥蚀下来的反应层特性方面的资料,如上一些技术处理是难以胜任的.现今,研究玻璃表面和玻璃特性,已采用一些常规的表面处理方法.当人们兼用溶液分析和表面分析时,透彻地掌握玻璃侵蚀机理和动力学就得以实现.     

酸处理及有机涂层对玻璃力学性能的影响

采用氢氟酸基溶液对玻璃进行腐蚀,研究酸腐蚀对玻璃强度的影响。对新鲜玻璃表面施加有机涂层,研究了玻璃表面的微观结构及力学性能。结果表明,酸腐蚀可以提高玻璃的强度,处理10 min后强度达到最大,但是强度稳定性差,表面易受损伤,在酸处理后的表面施加有机涂层可以极大提高玻璃的强度。其增强机制是,涂层填充了玻璃裂纹空隙,起到治愈损伤的效果,同时泊松抑制效应也对玻璃强度的增加起了作用。与物理钢化及化学钢化相比,这种综合增强方法明显提高了玻璃的力学性能,同时降低了成本。     

Effect of HF and NaOH etching on the composition and structure of SiOC ceramics

Porous SiOC ceramics were prepared with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) as sol?gel precursors, and followed by etching with HF and NaOH solution. The microstructure evolution and chemical etching as a function of pyrolysis temperature were investigated. The amorphous carbon increases as rising the temperature from 800 ^oC to 1200 ^oC, and the graphitic carbon increases with further etching by HF and NaOH. However, the effect of pyrolysis temperature on the structure of C is more significant. The hydroxylation reaction and phase separation of SiOC ceramics results in the increase of SiO₄ unit, which reacts with HF and NaOH to form micro- and mesopores. The existence of mesopore after HF etching provides more specific surface area and pore volume. However, NaOH etching produces more micropores, and the contribution of micropores to specific surface area and pore volume is higher than that of mesopores. Although HF and NaOH etching increase the specific surface area of SiOC ceramics, the etching effect of NaOH is superior to that of HF etching, and the carbon-enriched SiOC ceramics are obtained after NaOH etching.     

Non-damage deep etching of SiC by hybrid laser-high temperature chemical processing

SiC is considered as preferred material for micro-electro-mechanical system in the future. The excellent mechanical property and chemical stability make it difficult to perform deep etching. The hybrid laser-high temperature chemical etching is investigated to realize non-damage deep etching of SiC. The influences of defocus, laser pulse interval, laser intensity, and pulse number on etching depth are researched. The optimized laser parameter for SiC non-damage deep etching is laser intensity of 10 × 10⁹ W/cm² with a pulse interval of 10 ms. In order to analyze the interaction mechanism, the temperature field and laser-induced liquid jet in the liquid environment are calculated numerically. It is concluded that the material removal mechanism consists of laser heating vaporization during laser pulse, mechanical effect of laser-induced liquid jet impact between two adjacent laser pulses and chemical etching in laser-induced local high-temperature environment. The chemical reaction between SiC and mixture of HF, and HNO₃ solution produces gases and fluosilicic acid and effectively reduces the roughness of the modified layer making the surface smoother, and also removes the microcracks on the side wall of the etched region.     

Weakening of Soda-Lime Glass by Particle Impact During Hydrofluoric Acid Etching

During etching of soda-lime glass in hydrofluoric acid solutions, insoluble reaction products can collect in the acid solution or deposit on the glass surface. In this study it is shown that impact of these insoluble reaction products on the etching surfaces can cause strength degradation. The insoluble reaction products are characterized by scanning electron microscopy, wet chemical, X-ray diffraction, and surface area analyses.     

Mechanism of silicon etching in HF-KMnO4-H2O solution

The etching reaction of silicon in HF-KMnO₄-H₂O mixed solution has been studied under various experimental conditions. The etch rates were measured as a function of agitation speed, HF and KMnO4 concentrations, and etching temperature and time. A comprehensive mechanism for the silicon etching and insoluble solid-phase film (K₂SiF₆) formation has been proposed. The holes formed at silicon surface accelerated not only the etch rate of silicon but also the formation rate of K₂SiF₆. With the increase of hole concentration at lower HF concentrations the etch rates decreased because of the deposition of K₂SiF₆ on etched silicon surface. Under the condition of sufficiently high HF concentration, the rate increased with the increase of hole formation and the formation of holes at silicon surface was the rate limiting step of the silicon etching reaction in HF-KMnO₄-H₂O solution. High HF concentration enough for dissolving K₂SiF₆ was apparently essential to obtain high etch rate in the silicon etching reaction.     

Structure,morphology, and photoluminescence of porous Si nanowires: effect of different chemical treatments

The structure and light-emitting properties of Si nanowires (SiNWs) fabricated by a single-step metal-assisted chemical etching (MACE) process on highly boron-doped Si were investigated after different chemical treatments. The Si nanowires that result from the etching of a highly doped p-type Si wafer by MACE are fully porous, and as a result, they show intense photoluminescence (PL) at room temperature, the characteristics of which depend on the surface passivation of the Si nanocrystals composing the nanowires. SiNWs with a hydrogen-terminated nanostructured surface resulting from a chemical treatment with a hydrofluoric acid (HF) solution show red PL, the maximum of which is blueshifted when the samples are further chemically oxidized in a piranha solution. This blueshift of PL is attributed to localized states at the Si/SiO₂ interface at the shell of Si nanocrystals composing the porous SiNWs, which induce an important pinning of the electronic bandgap of the Si material and are involved in the recombination mechanism. After a sequence of HF/piranha/HF treatment, the SiNWs are almost fully dissolved in the chemical solution, which is indicative of their fully porous structure, verified also by transmission electron microscopy investigations. It was also found that a continuous porous Si layer is formed underneath the SiNWs during the MACE process, the thickness of which increases with the increase of etching time. This supports the idea that porous Si formation precedes nanowire formation. The origin of this effect is the increased etching rate at sites with high dopant concentration in the highly doped Si material.     

The role of silanol groups on the reaction of SiO2 and anhydrous hydrogen fluoride gas

It is essential to etch SiO₂ for producing silica glass components, semiconductor devices, and so on. Although wet-etching with hydrogen fluoride (HF) solutions is usually employed for this purpose, it faces a drawback that microstructures stick during the drying of the solution. To overcome this problem, we have developed a dry-etching technique with gaseous HF at high temperatures. In the present study, an interesting phenomenon was found that silicon thermal oxides were much less etched than vitreous silica by gaseous HF. Such difference had not been found in wet- or humid HF gas etching. Because their bulk chemical formulae are the same (SiO₂), it was suggested that the surface species affected the reaction rate. In fact, preprocessing with water vapor plasma remarkably increased the etching rate on the thermal oxides layer, and vacuum heating almost completely suppressed the reaction on the vitreous silica and the plasma-treated thermal oxides. These results indicate that the surface silanol groups enhance the reaction between SiO₂ and gaseous HF. Based on the results, a model of chain reaction for SiO₂ and gaseous HF was proposed, where the surface silanol groups act as the reaction center.     

Triangle pore arrays fabricated on Si (111) substrate by sphere lithography combined with metal-assisted chemical etching and anisotropic chemical etching

ABSTRACT: The morphological change of silicon macropore arrays formed by metal-assisted chemical etching using shape-controlled Au thin film arrays was investigated during anisotropic chemical etching in tetramethylammonium hydroxide (TMAH) aqueous solution. After the deposition of Au as the etching catalyst on (111) silicon through a honeycomb mask prepared by sphere lithography, the specimens were etched in a mixed solution of HF and H2O2 at room temperature, resulting in the formation of ordered macropores in silicon along the [111] direction, which is not achievable by conventional chemical etching without a catalyst. In the anisotropic etching in TMAH, the macropores changed from being circular to being hexagonal and finally to being triangular owing to the difference in etching rate between the crystal planes.     

Fabrication and photocatalytic properties of silicon nanowires by metal-assisted chemical etching: effect of H2O2 concentration

In the current study, monocrystalline silicon nanowire arrays (SiNWs) were prepared through a metal-assisted chemical etching method of silicon wafers in an etching solution composed of HF and H₂O₂. Photoelectric properties of the monocrystalline SiNWs are improved greatly with the formation of the nanostructure on the silicon wafers. By controlling the hydrogen peroxide concentration in the etching solution, SiNWs with different morphologies and surface characteristics are obtained. A reasonable mechanism of the etching process was proposed. Photocatalytic experiment shows that SiNWs prepared by 20% H₂O₂ etching solution exhibit the best activity in the decomposition of the target organic pollutant, Rhodamine B (RhB), under Xe arc lamp irradiation for its appropriate Si nanowire density with the effect of Si content and contact area of photocatalyst and RhB optimized.     

Nanopatterning of silicon with use of self-organized porous alumina and colloidal crystals as mask

Nanopatterning processes based on a localized anodization of Si and the subsequent chemical etching of SiO₂ were developed to fabricate a dot array and a hole array on an Si surface using self-organized anodic porous alumina as a mask. Through the porous alumina mask, regularly arranged metal nanopatterns on the Si surface were fabricated by the electroless deposition of Cu nanodots in a CuSO₄/hydrofluoric acid (HF) solution. The periodicity of the Cu dot arrays was determined using the pore interval of the upper anodic alumina. Using self-assembled nanospheres as a mask for an electroless plating of metals such as Cu and Ag on the Si substrate, the patterning of an ordered honeycomb structure and a hexagonally arranged convex array of metals on Si was also developed by the combination of colloidal crystal patterning and wet chemical etching. The proposed patterning processes of the Si surface have potential technological applications in fields that need textured surfaces of controlled nanoscale periodicity and morphology owing to their relative simplicity and low cost.     

HF刻蚀工艺对AZ91D镁合金疏水膜性能的影响

为了改善AZ91D镁合金表面疏水膜的疏水性,对以HF和N^MoOq为主要成分的刻蚀液进行了研究。通过改变刻蚀温度、刻蚀时间、HF的浓度及Na2MoO4的质量浓度,确定了最佳的刻蚀工艺条件为:HF 0.10 mol/L,Na2MoO41.00 g/L,1525°C,90 so实验结果表明:使用HF刻蚀液可以在镁合金表面形成理想的微纳结构。通过刻蚀构建的微纳结构可以明显提高疏水膜的疏水性。