Influence of thermal treatment on the porosity and surface characteristics of basic zirconium sulphate

Nitrogen adsorption and mercury intrusion methods have been employed to study the influence of thermal treatment over the temperature range 25–800°C on the development of porosity in basic zirconium sulphate. Such treatment leads to the progressive development of mesoporosity in the solid associated with the elimination of bidentate ligands. All the basic sulphates outgassed at temperatures within the above range exhibit low-pressure hysteresis in their nitrogen adsorption isotherms as well as a diminution in crystallinity. It is suggested that this indicates a reorganisation at the molecular level brought about by thermal treatment. Not only does this cause the breakdown of the sheet-like structure of the original solid with the consequent loss of its long-range crystalline order, but it also leads to the development of mesoporosity in the interstices between the small crystallites generated by such molecular disintegration.     

Porosity changes in soot resulting from oxygen atom adsorption at 298 K

Previously reported experiments from our laboratory showed that soot oxidation by oxygen atoms at 298 K was dominated by large net oxygen atom adsorption on this soot. The adsorbed oxygen was stable at 298 K; at elevated temperatures, this oxygen desorbed entirely as carbon monoxide and carbon dioxide. Here, we describe experiments using electron microscopy and nitrogen adsorption measurements to characterize the as-collected soot, soot loaded with varying amounts of adsorbed oxygen, and this oxygen-loaded soot that has been thermally degassed. The electron micrographs show small changes in the soot except at very long oxygen-atom exposure times, for which significant carbon gasification has occurred. The nitrogen adsorption measurements show large increases in the micropore structure of soot on thermal desorption of the adsorbed oxygen. These results confirm our earlier conclusion that oxygen atom adsorption occurs throughout the soot particles, not just on the surface. These data further show that thermal desorption (of CO and CO₂) occurs from within the soot particles and does not result from migration of the chemisorbed oxygen to the soot surface.     

基于不同测试方法的密封养护水泥砂浆孔隙率和饱水度变化规律

孔隙率和饱水度是影响混凝土耐久性的两个重要因素。为研究密封绝湿养护混凝土孔隙率和饱水度的变化规律,制备了不同龄期、不同水胶比的水泥砂浆试件,采用传统称重法、压汞法和核磁共振法测试孔隙率和饱水度。试验表明:3种方法测试结果的变化规律一致,但测值存在一定差异;对于孔隙率,称重法检测值最大,核磁共振法次之,压汞法检测值最小;对于饱水度,核磁共振法检测值大于称重法。在密封养护状态下,水泥砂浆孔隙率以14 d龄期为界随龄期增加表现为先增大后减小,且水胶比为0.41的试件孔隙率最大,最大孔隙率为39%;饱水度以14 d龄期为界随龄期增加表现为先减小后增大,且随水胶比增大而增大,最小饱水度为32%。压汞法检测结果具有一定随机性,传统称重法和核磁共振法检测结果更接近试件真实孔隙率。     

Characterization of Sintered Copper Wicks Used in Heat Pipes

Rectangular porous wicks for use in flat plate heat pipes were fabricated using copper powder (63 µm) sintered at 800°C and 1000°C. These wicks were characterized in terms of their porosity and pore size distribution using the techniques of mercury intrusion porosimetry and scanning electron microscopy (SEM). A uni-modal pore size distribution was obtained with most pores having sizes in the 30–40 µm range. Comparison was also made with cylindrical wicks fabricated by injection molding technique with the same binder and sintered at the same temperatures. Calculated permeability values of the rectangular wicks are comparable with commercially produced cylindrical wicks. When compared with conventional heat pipe wicks such as those using wire mesh, the advantage of these sintered wicks appears to be the existence of smaller pores and the controllability of porosity and pore size to optimize heat pipe performance.     

Textural study of a coal from villanueva de rio y minas (sevilla,spain) and of samples prepared from it by acid and heat treatments

A coal with high inorganic matter content from the mine of Villanueva de Rio y Minas (Sevilla, Spain) (VRMO) was classified by following the ASTM norms as a high volatile matter A bituminous coal. The starting coal was treated either with HCl (VRMH) or thermally at 1000°C for 2 h (VRMOC), the resultant yield values (referred to as VRMO, dry) being, respectively, 97 and 79%; also VRMH was either treated with HNO₃ (VRMN) or HF (VRMF), and the yield values (referred to as VRMH, dry) of the process were then 95 and 59%. The textural characterization of samples was effected by adsorption of CO₂ at 273 K and of N₂ at 77 K, as well as by mercury porosimetry. VRMN presents the highest value of the apparent surface area (S_D-R=219 m² g^?1) (CO₂, 273 K) and of the specific surface area of mesopores and macropores (S_me+ma=5.2 m² g^?1) (N₂, 77 K), while the greatest value of the cumulative specific surface area of macropores (S_ma=1.2 m² g^?1) (mercury porosimetry) corresponds to VRMOC; S values are expressed on a per gram of original sample basis. The micropore volume accessible to CO₂ at 273 K increases in both the HCl and the HNO₃ treatment and decreases in the HF and heat treatments. The HCl and HNO₃ treatments produce an increase of the mesoporosity; the HF treatment seems to affect in a special way the mesoporous texture. Furthermore, the heat treatment gives rise to a notable development of the macroporosity.     

基于场发射扫描电镜和Image J的锂电池隔膜孔隙率研究

通过对场发射扫描电镜(FESEM)条件的优化得到超高分子量聚乙烯(UHMWPE)锂电池隔膜表面清晰电镜图,然后用Image J软件处理得到孔隙分布图,运用膜孔隙率计算公式,成功获取锂电池隔膜表面膜孔的孔隙率。结果表明:通过FESEM和Image J软件相结合的方法可以形象地对锂电池隔膜的孔隙率进行表征,得到的孔隙率变异系数为6.36%,平均孔隙率为41.07%。     

氢氧化锆及其焙烧产物对磷酸根的吸附特性研究

以氢氧化锆作为吸附水溶液中磷酸根的吸附剂,考察了氢氧化锆在不同焙烧温度下的分子式及其对磷酸根吸附效果的影响。通过正交试验确定了最佳实验条件,此条件下氢氧化锆的吸附量为210.9 mg/g。经100、200、300、400、500、600 ℃焙烧后的氢氧化锆对磷酸根的吸附量随温度升高逐渐减小;氢氧化锆经700 ℃焙烧后,焙烧产物氧化锆不具有吸附性。TG、XRD分析表明,随着焙烧温度的升高,氢氧化锆的表面活性基团（-OH）数量逐渐减少。结果表明,吸附剂表面羟基的数量直接影响吸附剂的吸附性。     

肥料中硝态氮、铵态氮、总氮的研究

研究仅含硝态氮、铵态氮的肥料,结果表明,用GB/T8572-2010《复混肥料中总氮含量的测定蒸馏后滴定法》检测含有硝态氮、铵态氮的肥料中铵态氮含量、硝态氮含量(差减法总氮含量-铵态氮含量=硝态氮含量)(标准GB/T8572-2010《复混肥料中总氮含量的测定蒸馏后滴定法》中没有体现总氮含量-铵态氮含量=硝态氮含量,这是根据铵态氮与硝态氮性质总结研究出来的)与标准NY/T1116-2014《肥料硝态氮、铵态氮、酰胺态氮含量的测定》单独检测铵态氮含量、硝态氮含量结果无显著性差异。GB/T8572-2010检测总氮含量与SN/T0736.5-2010《进出口化肥检验方法第5部分:氮含量的测定》检测总氮含量无显著性差异。     

中国硝酸钾发展概况与市场前景

硝酸钾既是重要的工业原料,又是优质无氯钾、氮复合肥料,植物营养素钾、氮的总质量分数可达60%左右,是发展现代高效农业不可缺少的化肥品种。由于生产、市场、价格等方面的原因,目前硝酸钾在中国施用较少,而这种称为世界紧缺的"绿色钾肥"在欧洲国家较为盛行。伴随着高科技农业的不断发展,以及人们对食品安全要求的不断提高,中国市场对硝酸钾的需求将不断增加,不过目前这一市场仍表现出过于狭窄。简要介绍了硝酸钾的生产技术、中国硝酸钾生产发展现状、硝酸钾应用领域及市场前景,并对硝酸钾的发展提出了一些建议。     

Physicochemical characterization of maize tassel as an adsorbent. I. Surface texture,microstructure, and thermal stability

In this study, various physicochemical parameters were evaluated for maize tassel, a novel adsorbent. The Brunauer–Emmett–Teller (BET) isotherm was used to experimentally model N₂‐adsorption data (up to a relative pressure of 0.30); the results indicated that the powdered material was mesoporous with a BET specific surface area, total pore volume (up to a relative pressure of 0.98), and average pore width (4V/A by BET) of 2.52 m²/g, 0.0045 cm³/g, and 7.2 nm, respectively, for the 150–300‐μm fraction. Laser diffraction pattern analysis yielded particle size distributions for the 45–50‐, 50–150‐, and 150–300‐μm fractions. High‐resolution scanning electron microscopy revealed a microstructure showing predominantly flattish, rodlike particles. The material exhibited stability to thermal decomposition up to about 230°C, as evidenced by the results obtained from simultaneous thermogravimetry/differential thermal analysis and differential scanning calorimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Pea (Pisum sativum L.) peel waste carbon loaded with zirconium: study of kinetics,thermodynamics and mechanism of fluoride adsorption

ABSTRACT

Pea peel waste carbon loaded with zirconium is used as an engineered biochar material for adsorption of fluoride from aqueous solution. The prepared adsorbent was characterized and the material degradation kinetics were studied using thermogravimetric analysis. Adsorption kinetics follow both pseudo-second order and intra-particle diffusion model. Optimization of algorithm yielded Freundlich isotherm as the best fitting equation. Increment in solution temperature thermodynamically favors fluoride adsorption. Fluoride adsorption remains unaffected in presence of specific co-ions. Adsorbed fluoride could be successfully leached using 0.001 N NaOH and reusability of the material was tested up to tenth cycle of continuous operation.     

Porous Silica Matrix Obtained from Pyrex Glass by Hydrothermal Treatment: Characterization and Nature of the Porosity

A novel porous silica matrix has been prepared from Pyrex glass, using hydrothermal treatment under saturated-steam condition. This process makes it possible to obtain, in one step, a silica support formed of a homogeneously distributed and interconnected macropore microstructure. The new matrix contains silanol groups that can be used in reactions of surface modification to provide a hybrid material and a selective macrofiltration membrane, and also it can improve chemical inertness. The porous matrix is noncrystalline as obtained and, after thermal treatment at temperatures higher than 950°C, exhibits an X-ray pattern characteristic of α-cristobalite and low volume contraction. The present samples were characterized by scanning electron microscopy, mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, infrared spectroscopy, X-ray powder diffractometry, atomic absorption, and high-resolution solid-state nuclear magnetic resonance. The results present a new way of producing a macroporous silica matrix.     

Performance,characterization, and surface acidity of zirconium modified hydroprocessing catalysts

Gas-oil hydrodesulfurization activity of Ni-Mo/Al₂O₃ catalysts was significantly improved when prepared with zirconium alkoxide, but lowered when prepared with Zr nitrate. IR of CO adsorption on reduced catalysts, and LRS and XPS of calcined catalysts show that the addition or zirconium does not effect the metal oxide structure. IR of pyridine adsorption and²⁷Al NMR both show greatly enhanced Lewis and Brønsted acidities of the Zr alkoxide modified materials as compared to unmodified samples. These results point to the strong influence of surface acidity on activity in hydroprocessing catalysts.     

Effect of Chloride‐Based Accelerator in the Presence of Water‐Reducing and Retarding Admixture on Autogenous Shrinkage

Rapid repair concrete mixtures commonly used for full‐depth concrete pavement repair sections can use large dosages of accelerating admixtures to increase strength gain rates and decrease the time to traffic opening. Most often, these mixtures also contain water‐reducing and retarding admixtures (WRRAs) to allow for the use of a low water–cementitious material ratio in order to meet strength requirements. The use of large dosages of accelerating admixtures in combination with retarding admixtures could have significant side effects on concrete. Autogenous shrinkage of low water–cementitious concrete can contribute to high tensile stresses and cracking problems. The effect of calcium chloride‐based accelerating admixture dosage, when used with WRRAs, on autogenous shrinkage was measured. It was found that the inclusion of calcium chloride‐containing accelerating admixtures has a nonlinear effect on the pore size distribution and consequently a nonlinear increase on the autogenous shrinkage.     

Field study of the fate of labelled fertilizer nitrate applied to barley and maize in sandy soils

The recovery in crop and soil of labelled fertilizer nitrate applied to barley and maize growing on a sandy soil was measured. The experimental plots, each measuring 4m × 4m, were situated on fields growing with barley and with maize. The barley received 50 kg N/ha as KNO₃ enriched with 5.99 At.%¹⁵N excess while the maize received 113 kg N/ha as KNO₃ labelled with 5.014 At.%¹⁵N excess. Otherwise, the plots were treated the same as the rest of the field. At harvesting, the barley and the maize plots were subdivided into nine and six sub-plots respectively. Plant samples, including the roots and soil samples up to 1 m depth were collected in each sub-plot. Fertilizer N recovery in the samples was measured. In the plants, the N derived from the fertilizer (Ndff) was 24.0% and 16.7% in barley and maize, respectively. The percentage of the applied fertilizer recovered by barley was 57%; for maize, only 18%. The movement of fertilizer N was restricted to the top 50 cm in the barley plot, whereas in the maize plot, the fertilizer N could be detected down to 90 cm. The amount of fertilizer N remaining in the soil at harvest was 32% for the barley and 68% for the maize plot. The loss of fertilizer N under barley was 10% and 14% under maize. The loss was attributed mainly to denitrification. The means and the variances of total N uptake by plants inside the¹⁵N plot and outside the¹⁵N plot were compared. They did not differ significantly, indicating that the results obtained from the¹⁵N plot can be extrapolated to the rest of the field.     

Effect of annealing on grain growth and Y segregation behavior in tetragonal ZrO2 thin film

In order to fabricate tetragonal yttria stabilized zirconia samples with large grain size, 3 mol% Y₂O₃ doped zirconia thin films were grown on (0001) α-Al₂O₃ substrate by pulsed laser deposition (PLD) followed by subsequent high temperature annealing. The thin film samples were annealed at 1200°C, 1250°C, 1300°C, and 1350°C in order to obtain larger grain size without Y segregation. The microstructure and chemical composition of these annealed films were analyzed using atomic force microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The as-grown thin film was found to be composed of [111]-oriented grains of ∼100 nm connected with small-angle tilt boundaries. Based on analysis of annealed thin films, it was revealed that grain growth of tetragonal zirconia occurred anisotropically. Cross section scanning transmission electron microscopy observations revealed that such grain growth behavior is affected by the step-terrace structures of the sapphire substrate. Energy-dispersive X-ray spectroscopy showed that Y was found to distribute almost uniformly below 1300°C but to segregate at the grain boundaries at 1350°C. As a conclusion, the 1300°C-annealed sample shows the largest grain size with homogeneous Y distributions.     

氨氮和硝酸盐氮对再生水管网腐蚀状况的影响研究

在模拟真实管网水力条件下,从腐蚀速率、铁释放、腐蚀产物形貌及成分等方面,研究了氨氮和硝酸盐氮对碳钢腐蚀的影响。研究发现,加氨氮和硝酸盐氮的工况1与未加两种物质的工况2相比,工况1有更低的铁释放速率和腐蚀速率。两种工况腐蚀产物类型差别不大,腐蚀产物主要包括γ-FeOOH、α-FeOOH、Fe_2O_3、Fe_3O_4、β-FeOOH,未检测出碳酸钙但出现一种新的晶型———钙磷石,整体来说工况1腐蚀产物密实、稳定性更好。     

Surface properties and flexural strength of a monolithic zirconia submitted to grinding and regenerative heat treatment

The present study evaluated the average (Ra) and total (Rz) roughness, crystallography (XRD), flexural strength (FS), and Weibull modulus (m) of a monolithic zirconia subjected to grinding (G) and heat treatments (HT). Specimens were submitted or not to grinding with a diamond stone in low rotation. HT was conduced in two protocols, one at 900°C for 60 minutes and the other at 1000°C for 30 minutes. Roughness was evaluated in a profilometer, crystallography in X-ray diffractometer, and FS by four-point flexural strength in a mechanical testing machine. Grinding increased Ra, Rz, and FS. HT had no influence on roughness and for the FS, just decreased in the group that was ground and heat treated with 1000°C for 30 minutes. Neither G nor HT changed the m of the groups. In addition, the HT was able to reverse all monoclinic phases. By the properties evaluated, both HTs could be done without damaging the material.     

田间土壤硝态氮快速测定方法的研究与应用前景

对田间土壤硝态氮(NO3N)快速测定方法的研究,包括土壤水分快速测定方法、快速提取技术(经济、易于获得的提取剂和简易、快捷的提取方法)、温度校正系数以及合理使用试纸反射仪的研究。大量的试验结果表明,田间土壤硝态氮快速测定方法所得的土壤硝态氮含量与实验室标准方法所得结果有着良好的线性相关关系。本研究所提出的田间土壤硝态氮快速测定方法具有经济、操作简单、便于农民掌握等特点。目前中国存在着施肥不合理的现象,亟须简易可靠的田间测土技术,因此,田间土壤硝态氮快速测定方法在中国将有着广阔的应用前景。     

多孔粒状陶瓷负载水合氧化锆吸磷材料的制备及其性能研究

以工业粉状废物为主要原料制备出粒径为2～4 mm,孔隙率为45.93%,表观密度为1.37 g/cm3,单颗抗压强度为47.73 N的粒状陶瓷滤料,并在其上负载水合氧化锆以制备吸磷材料,考察其吸磷性能和影响因素。通过SEM、XRD和FT-IR对材料进行分析,以研究其吸磷机制。结果表明:滤料负载水合氧化锆后,质量增加了20.48%,比表面积由7.15 m2/g增大到19.35 m2/g,大孔结构为主的孔隙结构变为以介孔结构为主。吸磷主要通过其表面的羟基和磷酸根之间的离子交换实现。在30℃、pH为7时,其对磷酸根有较好的吸附能力,饱和吸附量为10.79 mg/g。其吸附等温线符合Langmiur吸附模型,吸附动力学符合二级吸附动力学模型。吸附后的滤料可在NaOH中再生,经多次"吸附-解吸"后,其吸附容量一直稳定在0.5 mg/g左右。