Use of Boron Phosphate in the Solid-State Preparation of Crystalline Iron(III) Phosphate and Manganese(II) Diphosphate

The possibility of using BPO₄ for the solid-state preparation of crystalline phosphates of trivalent iron, manganese, and chromium has been investigated. If BPO₄ and Fe₂O₃ are heated at 900°C, a complete conversion of BPO₄ to the quartz form of FePO₄ results after 9 h. If FeCl₃.6H₂O is used instead of Fe₂O₃, a multiphase crystalline product is obtained in which the dominant phase is the quartz form of FePO₄. The reaction of BPO₄ with Mn₂O₃ or MnO₂ at 830°C yields Mn₂P₂O₇; the amount of conversion of BPO₄, to Mn₂P₂O₇ after 4 h is 80% (if Mn₂O₃ is used) and 75% (if MnO₂ is used). However, the method is not successful in the preparation of phosphates of chromium: the reaction of BPO₄ and some chromium compounds yields α-Cr₂O₃ as the only chromium-containing product.     

一种新型磷酸硼的制备方法

用常温常压的方法制备了磷酸硼 ,用红外光谱与 X-射线粉末衍射确认了所制备的化合物 ,同时用差热热重分析研究了此化合物的热稳定性。     

Preparation of Boron Nitride Flakes by a Simple Powder Reaction

Boron nitride (BN) with flake-like morphology has been synthesized by reacting powder H₃BO₃, Mg, and NH₄Cl. X-ray diffraction patterns show that the sample has hexagonal phase with lattice parameters a =2.506 and c =6.692 Å. Transmission electron microscopy and field emission scanning electron microscopy indicate that the as-synthesized product is pure flake with a mean size of about 100 nm width and 600 nm length. X-ray photoelectron spectra give an average B/N atomic ratio of 0.98:1. Fourier transformation infrared spectroscopy has a strong B–N absorption at 1376 and 814 cm⁻¹.     

磷酸盐基碳化硼陶瓷多层涂层的制备

实验以磷酸盐粘结剂作为基料、碳化硼粉末作为主要骨料制备出磷酸盐基碳化硼核辐射屏蔽涂层,对实验结果进行了XRD和SEM检测,并作分析.通过改变涂料成分配比,确定最合适的骨料配方为：Al2O3∶SiO2∶B4C=2∶1∶6,最合适的烧结温度约在500℃左右,并用新方法配置了磷酸盐粘结剂,实现了H3PO4∶Al（OH）3=3∶1的最佳配比,大大缩短了配置粘结剂所用的时间,制备了磷酸盐基碳化硼核辐射屏蔽多层涂层.     

Reaction Synthesis of Aluminum Nitride–Boron Nitride Composites Based on the Nitridation of Aluminum Boride

Aluminum nitride–boron nitride (AlN–BN) composites were prepared based on the nitridation of aluminum boride (AlB₂). AlN powder was added to change the BN volume fraction in the obtained composites. Thermogravimetry–differential thermal analysis (TG-DTA), X-ray diffractometry, and the nitridation ratio were used to investigate the nitridation process of AlB₂. At ∼1000°C, a sharp exothermic peak occurred in the DTA curve, corresponding to the rapid nitridation of aluminum in AlB₂. On the other hand, the nitridation of the transient phase, Al_1.67B₂₂, was very slow when the temperature was <1400°C. However, the nitridation speed obviously accelerated at temperatures >1600°C. The pressure of the nitrogen atmosphere was also an important factor; high nitrogen pressure remarkably promoted nitridation. Treatment at 2000°C was disadvantageous for nitridation, because of the rapid formation of a dense surface layer that inhibited nitrogen diffusion into the specimen interior. Three specimens, with 5 wt% Y₂O₃ additive and different BN contents, were prepared by pressureless reactive sintering, according to the determined sintering schedule. Electron microscopy (scanning and transmission) observations revealed that the in-situ -formed BN flakes were homogeneously and isotropically distributed in the AlN matrix. A schematic mechanism for microstructural formation was developed, based on the results of nitridation and the microstructural features of the obtained composites. The obtained composites, with a low BN content, exhibited a high bending strength, comparable to that of reported hot-pressed AlN–BN composites.     

Reaction Sintering of Cubic Boron Nitride Using Volatile Catalysts

Reaction sintering behavior of cBN, which is accompanied by the transformation from hBN to cBN in the presence of 30 wt% diamond seed grains, was investigated under high pressure conditions (6.0–7.5 GPa, 1400–1700°C, 0–30 min) using volatile catalysts such as NH₄NO₃, NH₄Cl, and NH₂NH₂. Fully dense sintered compacts having a Vickers microhardness of more than 5000 kg/mm² were prepared with no residual catalytic solid components. The activation energy for the conversion from hBN to cBN was 200–230 kJ/mol. Adsorbed N₂, H₂, and/or NH _x components which were formed by decomposition of these catalysts during high pressure and temperature treatments, would have a favorable kinetic effect on cBN formation from hBN and its simultaneous sintering.     

Wettability of Pyrolytic Boron Nitride by Aluminum

The wetting of pyrolytic boron nitride by molten 99.9999% pure aluminum was investigated by using the sessile drop method in a vacuum operating at approximately 660 μPa at temperatures ranging from 700° to 1000°C. The equilibrium contact angle decreased with an increase in temperture. For temperatures at 900°C or less the equilibrium contact angle was greater than 90°. At 1000°C a nonwetting-to-wetting transition occurred and the contact angle stabilized at 49°.     

共聚法制备聚硅硼酸铝铁絮凝剂及其絮凝性能研究

以硅酸钠为主要原料共聚法合成了絮凝剂聚硅硼酸铝铁,研究了絮凝剂的最佳制备条件及其对CODCr的去除效果。实验结果表明：絮凝剂中Al3＋/Si、Fe3＋/Si和B/Si物质的量比分别为1︰2、1︰1和1︰10时聚硅硼酸铝铁的絮凝效果最好。在最佳制备工艺下制备的絮凝剂的用量为130 mg/L,废水pH为6~8的条件下,对印染废水中CODCr的去除率高于60%。     

质量法测定铝基碳化硼材料中碳化硼的含量

采用HCl溶解质量法测定铝基碳化硼材料中碳化硼的含量。对称样量、水浴温度等实验条件进行了优化,并验证了方法的精密度和准确度。结果表明,质量法测定铝基碳化硼材料中碳化硼的含量,简单、快速,精密度高,结果准确可靠,可用于批量样品测试。     

Boron Phosphate: Preparation in Aqueous Medium; Physical and Chemical Characterization

Heating equimolar amounts of pure phosphoric and boric acids in aqueous solution yields, at 130°, a solid boron phosphate of the composition R = P₂O₅/B₂O₃ = 1:1.71. Increasing the calcination temperature to 575° increases R to 1:1.29 due to evaporation of boron-values. Further heating to 850° causes no additional weight losses. The specific surface decreases monotonically with the calcination temperature, from 7.4 to 0.5 m²/g. X-ray diffraction data indicate that up to 10 min heating at 800°, increased calcination temperature causes a monotonic decrease in the unit cell dimensions, while prolonged heating (48 h) at this temperature reverses this trend.     

氧化铜为助熔剂制备硼酸铝晶须

利用H3BO3和Al(OH)3为原材料,CuO为助熔剂制备硼酸铝9Al2O3·2B2O3晶须。经研究发现,试样在1350℃煅烧6h,试样的物相为硼酸铝相。以CuO为助熔剂制备的硼酸铝晶须,其直径较均匀为1～5μm,长度为10μm。     

Preparation of Dispersed Phase Ceramic Boron Nitride and Aluminum Nitride Composite Coatings by Chemical Vapor Deposition

Dispersed phase ceramic composite coatings containing BN and AIN were prepared by chemical vapor deposition. The BN + AIN coatings were deposited on Al₂O₃ from the BCI₃–AICI₃-NH₃ reagent system in the temperature range of 700° to 1200°C. Also, single-phase BN and AIN coatings were prepared for comparison purposes. The composite coatings consisted of very small BN and AIN regions which were either crystalline or amorphous, depending on deposition temperature and reagent concentrations. For example, a composite containing AlN whiskers of less than 100-nm diameter in a matrix of turbostratic BN of 2-nm grain size was deposited at 1100°C and 20 kPa.     

氧化铜为助熔剂制备硼酸铝晶须

利用H3BO3和Al（OH）3为原材料,CuO为助熔剂制备硼酸铝9Al2O3·2B2O3晶须。经研究发现,试样在1350℃煅烧6h,试样的物相为硼酸铝相。以CuO为助熔剂制备的硼酸铝晶须,其直径较均匀为1～5μm,长度为10μm。     

熔盐电解法制备元素硼粉

介绍了熔盐电解法制备元素硼粉的方法,讨论并比较了各体系的长处与不足.     

Rapid Hydrogen Generation from the Reaction of Aluminum Powders and Water Using Synthesized Aluminum Hydroxide Catalysts

A synthesized and nano-sized Al(OH)₃ powder that promotes the generation of hydrogen from a Al/water reaction is demonstrated. In this study, aluminum hydroxides are synthesized using sodium aluminate NaAlO₂, distilled water and ethanol. The mole ratio of ethanol/water and the concentration of sodium aluminate in solution affect the crystal structure, morphology and sizes of the Al(OH)₃ powders significantly. These Al(OH)₃ powders contain both gibbsite and bayerite phases and exhibit excellent catalytic power on the hydrogen generation of Al/water system. It is proposed that two major characteristics of Al(OH)₃ powders dominate the catalytic power. That is, the surface area and the high-energy sites of Al(OH)₃. When mole ratio of ethanol/water is between 0.3–0.6 and the concentration of NaAlO₂ is higher than 0.0167 g/ml, the synthesized Al(OH)₃ powders are in a more gibbsite-oriented and plate-like structure. Other than above conditions result in a more bayerite-oriented and particulate-like structure. The plate-like structure exhibits strong catalytic power due to the existence of high-energy sites on the edge of plates even its surface area is not so high. The particulate-like structure may also have strong catalytic power when it has a high surface area. By taking advantage of the exothermic reaction, ~?100% yield of hydrogen can be produced from 1 g Al/10 g water system within 30 s using 3 g synthesized Al(OH)₃. A aluminum waste scrap can also react with water using these effective catalysts and generate?~?95% yield of hydrogen within 8 min.     

Augmentation of Aluminum and Boron Ignition

Combustion, Explosion, and Shock Waves - Effect of K2CO3 and KCl additives on the process of high-temperature oxidation and ignition of conglomerates of powdered boron and aluminum particles and on...     

含铝磷酸盐耐高温防腐蚀涂料制备及施工工艺的研究

探讨了含铝磷酸盐涂料配方中部分原材料的用量对施工工艺和涂料性能的影响。主要讨论了水的用量、助剂的选择和用量以及施工环境对涂层表干速率和施工工艺的影响,在此基础上简单总结了该涂料的制备方案以及相应的施工工艺。     

微波法由富锰渣制备4A分子筛

研究了以富锰渣为原料制备分子筛的工艺.作者以浓硫酸为浸取介质,在90～100 ℃下反应3 h,将富锰渣中锰、铁、钙、镁等可溶性物质溶出,液相中的锰用来制备硫酸锰.过滤所得固相酸浸渣在微波反应器中与碱反应将硅铝溶出,以分析纯Al(OH)3为铝源,补铝调整比例到4 A分子筛合适的硅/铝比,使溶液中各物质摩尔比为SiO2/Al2O3≈2,H2O/Na2O≈28,Na2O/SiO2≈0.9.浓缩溶液至过饱和状态,为结晶做准备.将过饱和状态的溶液放在空气中冷却到30 ℃,稍等片刻,再升温至90 ℃左右,恒温5 h左右,加入NaCl少许,放冷使之结晶.过滤并洗涤晶体至pH值至9～10,于马弗炉中500 ℃左右煅烧1 h脱水,即得4A分子筛产品.4A分子筛的质量指标符合GB1768-93,XRD分析与文献数据基本吻合.     

Amorphous α-Tricalcium Phosphate: Preparation and Aqueous Setting Reaction

The mechanical and setting properties of calcium phosphate cements are considerably determined by the pretreatment of the constituents. In this report we show for the first time that prolonged high-energy ball milling of α-tricalcium phosphate (α-TCP) led to mechanically induced phase transformation from the crystalline to the amorphous state. The amorphous material demonstrated a high reactivity such that the time for substantially complete conversion of α-TCP to calcium-deficient hydroxyapatite in 2.5% Na₂HPO₄ solution decreased from about 20 h (1 h of grinding in ethanol, 85% relative crystallinity) to 4–6 h for a material with a crystallinity of 8% (24 h of grinding). This reactivity could be attributed to an increased thermodynamic and kinetic solubility of the ground materials. Mechanically activated α-TCP cements were produced with compressive strengths of up to 80 MPa and setting times of 5–16 min. The effect of reactant preparation and cement mixing parameters on the physical and chemical properties of mechanically activated α-TCP cement was investigated. By comparing cements of similar porosity and degree of conversion it was demonstrated that apatite specific surface area has a strong influence on cement mechanical performance, which highlights the importance of this previously overlooked parameter in improving strength.