KOH活化法高比表面积竹质活性炭的制备与表征

以竹屑为原料,研究了KOH活化法高比表面积活性炭的制备工艺.分别考察了浸渍比、活化温度、活化时间等工艺参数对产品吸附性能的影响,并提出了可能的活化机理.在所研究的实验条件下,最佳的制备工艺是浸渍比1.0,活化温度800℃,活化时间2h.所得到的活性炭产品的比表面积和孔容可达2996m2/g和1.64cm3/g.该产品附加值高,在吸附领域特别是在双电层电容器的电极材料领域有广阔的应用前景.     

山茶油脂肪酸甲酯化条件研究

油脂甲酯法是应用气相色谱法测定油脂脂肪酸组成一个必不可少预处理工序。该文报道对比研究KOH―甲醇溶液法、H2SO4―甲醇溶液法对山茶油进行甲酯化效果,着重探讨振荡温度、振荡时间、催化剂用量等因素对山茶油甲酯化效果影响规律,通过气相色谱法测定油酸峰面积及油酸甲酯转化率为考核指标,优化KOH―甲醇溶液法和H2SO4―甲醇溶液法甲酯化条件,并提出酸碱结合甲酯化新方法,研究结果表明,采用酸碱结合法对山茶油进行甲酯化效果优于KOH―甲醇溶液法和H2SO4―甲醇溶液法,对应用气相色谱法测定油脂脂肪酸组成具有实际指导意义。     

KOH与NaOH浸渍麦草化学机械法制浆性能比较

探究了KOH与NaOH在用碱量3%～7%(以KOH计)与浸渍时间10～80 min的不同条件对麦草化学机械浆及所抄纸张物理化学性能的影响。结果表明,在常压、浸渍温度95℃的温和条件下,KOH浸渍的麦草化机浆与NaOH浸渍的麦草化机浆相比,具有更高的紧度和强度。在浸渍过程中,由于KOH具有较强的脱木素能力,纸浆得率下降较多;KOH碱性较强,导致残液的pH值较高。KOH比NaOH破坏麦草纤维素结晶区的能力更强,因此其浸渍后的麦草浆中纤维形态较NaOH浸渍后的纤维形态更优。     

低品位铌钽矿高浓碱性介质浸出过程动力学研究

The leaching kinetics of niobium from a low-gr~te niobium-tantalum ore by concentrated KOH solution under atmospheric pressure has been studied. Significant effects of reaction temperature, KOH concentration,stirring speed, particle size and mass ratio of alkali-to-ore on the dissolution rate of niobium were examined. The experimental data of the leaching rates and the observed effects of the relevant operating variables were well interpreted with a shrinking core model under diffusion control. By using the Arrhenius expression, the apparent activation energy for the dissolution of niobium was evaluated. Finally, on the base of the shrinking core model, the rate equation was established.     

KOH活化处理碳纳米管对其负载非晶态NiP催化性能的影响

经KOH活化处理和未经活化处理的碳纳米管分别用于负载非晶态NiP合金.以苯加氢为探针反应,研究了KOH活化处理温度和时间对碳纳米管的性质及其负载非晶态NiP催化剂活性的影响.研究结果表明:碳纳米管经KOH处理可以提高其负载非晶态NiP催化剂的催化活性,催化剂活性随活化温度升高和活化时间延长而增加.由于KOH处理改变了碳纳米管的微观结构,增加了其比表面积,所以非晶态NiP在碳纳米管上更易沉积分散,其负载的非晶态NiP合金催化剂的催化活性较高.     

Evaluation of activated carbon adsorbent for fuel cell cathode air filtration

The effectiveness of a commercial activated carbon modified by KOH (KMAC) was evaluated as adsorbent for purifying NO_x and SO₂, which are the major contaminants in fuel cell cathode air stream. The N₂ adsorption–desorption isotherms of KMAC samples showed that the surface structure of the activated carbon was changed significantly by KOH impregnation. The sample of KMAC with a loading of 10.1% KOH by weight presented the highest adsorption capacities for both NO_x and SO₂, which were 96 mg g⁻¹ and 255 mg g⁻¹, respectively. A pre-exposure of KMAC to CO₂ caused neither effect on the adsorption of NO_x nor on the adsorption of SO₂. KMAC could fully protect a 250 W proton exchange membrane fuel cell (PEMFC) stack from 1100 ppb of NO_x and 250 ppb of SO₂ for about 130 h.     

Preparation of activated biomass carbon from pine sawdust for supercapacitor and CO2 capture

Biomass based carbon has captured more and more attention because it is environmentally friendly and has properties of low cost and ideal sustainability. In this study, three kinds of activated biomass carbons (ie, ABC-700, ABC-800 and ABC-900) were first carbonized through pine sawdust pyrolysis and then activated using KOH under three different activation temperatures (ie, 700°C, 800°C and 900°C). The structure properties of the prepared activated biomass carbons were characterized by N₂-adsorption/desorption, SEM, TEM, XRD, Raman, XPS, TG and ultimate analysis. To clarify the activation mechanism, the gas products produced during KOH activation process were measured online with an ETG gas analyzer. The performance of the activated biomass carbons derived from pine sawdust for supercapacitor and CO₂ capture was then evaluated. The predominant gas products during the activation process are H₂ and CO. It indicates that the porous structure was created by using an enhanced etching reaction between carbon atoms and KOH. An increment of the activation temperature from 700 to 900°C results in the increase of surface area (from 1728.66 to 2330.89 m²/g) and total pore volume (from 0.671 to 1.914 cm³/g). Among the three samples, ABC-900 exhibits the maximal specific capacitance of 175.6 F·g⁻¹ and high energy density of 24.39 Wh·kg⁻¹ at the 0.5 A·g⁻¹. And the ABC-700 shows the maximal CO₂ capture capacity of 4.21 mmol/g and high selectivity of CO₂ over N₂ at 298 K and 1 bar. In addition, ABC-700 also has excellent stability and reproducibility after 15 times adsorption-desorption cycles. The unexceptionable electrochemical performance and adsorption capacity of the biomass-carbons show its broad application prospects in the field of supercapacitors and CO₂ capture.     

Role of KOH and NaNO2 on the structural and corrosion properties of anodic spark electrolysis coatings produced on aluminium

Doping light elements into ceramic coatings on different metal substrates by anodic-spark electrolysis (ASE) to improve their properties, such as wear and corrosion resistance, has recently attracted a lot of attention. In this study, nitrogen-doped Al₂O₃ composite ceramic coatings had been fabricated in eco-friendly KOH–NaNO₂ electrolytes using the anodic-spark electrolysis (ASE) method after 9 min at a fixed applied ASE voltage (75 V higher than the breakdown voltages). To deposit a nitrogen-doped coating with high amounts of oxynitride phases possible, we thoroughly studied the ASE coatings deposited in different total variable salts concentrations (KOH+NaNO₂) and NaNO₂/KOH ratios of ASE electrolytes. The coating properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), and the electrochemical impedance spectroscopy (EIS) tests. The results indicated that the coating produced in the KOH–NaNO₂ electrolyte with a low total variable salts concentration (2 gr.L⁻¹) and a high NaNO₂/KOH ratio value (3) is optimum in the investigated conditions. It has the highest percentage of nitrogen-doped phases, such as N-doped γ-Al₂O₃ and γ-AlON (γ-Al_2.78O_3.65N_0.35), and a homogeneous morphology of surface with the smallest average size of pores (<14 μm²). This coating showed the significantly higher corrosion resistance with a 4.101104 × 10⁶ Ω cm² value compared to the uncoated aluminium substrate with a corrosion resistance value of 0.094195 × 10⁶ Ω cm² after 48 h of immersion in the 3.5 wt% NaCl solution. The approach presented herein provides an attractive way to modify the surface of aluminium alloys to improve corrosion behaviour.     

Doped biochar from an invasive plant “Eichhornia crassipes” for the oxygen reduction reaction

N-doped carbon derived from Eichhornia crassipes biomass is appealing since it transforms a weed into a sustainable resource for Fuel Cell applications. Activated carbons were prepared using KOH at 700 °C with N_2; before being doped with hydrazine. As a result of the activation process, the samples EC-SAP (not doped) and EC-SAPD got a surface area (S_BET) of 1577 and 1222 m² g^?1, respectively. Besides, both samples showed the carbonaceous D and G bands indicative. The presence of carbon in EC-SAP and 3.56% of N in EC-SAPD was corroborated by elemental analysis CHNS. The testing system for the Oxygen Reduction Reaction activity consisted of a three-electrode cell with 0.5 M KOH. The EC-SAPD sample showed promising performance for ORR with a high cathodic reaction potential of 0.82 V and a transfer of 3.6 electrons. Its surface area and nitrogen concentration improve its performance compared to EC-SAP.     

硅各向异性浅槽腐蚀实验研究

通过实验分析,对比了异丙醇(IPA)和超声波对Si(100)面在KOH溶液和四甲基氢氧化氨(TMAH)溶液中的浅槽腐蚀速率及其表面形态的影响。实验结果表明,IPA能降低TMAH溶液的腐蚀速率,但IPA在KOH溶液中腐蚀速率降低不明显;IPA加入到较高浓度的KOH溶液中,会在Si表面产生较大小丘,恶化了Si腐蚀表面的质量,但在TMAH溶液中加入一定量的IPA会改善腐蚀表面的质量;超声波能加快腐蚀速率并能改善Si腐蚀表面质量,但对于加入IPA的较高浓度KOH溶液,超声波未能消除Si腐蚀表面的小丘,另外,超声波还能减弱腐蚀过程中微尺寸沟槽的尺寸效应;在腐蚀条件和配比一定情况下,TMAH溶液的腐蚀质量比KOH溶液好。