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采用TG-DTG、DTA和XRD对铬酸铵钠复盐结晶(NaNH4CrO48226;2H2O)的热分解过程进行研究,结果表明NaNH4CrO48226;2H2O的热分解过程分为三步进行,第一步是在50~95 ℃温度范围结晶水的脱除,第二步是在100~180 ℃的温度范围铵的初步热分解,产物为铬酸钠和重铬酸铵,第三步是215~385 ℃进行的铵的完全分解.存在生成重铬酸钠与生成三氧化二铬的竞争反应.在氨不易扩散的条件下,最终分解产物为三氧化二铬、重铬酸钠和铬酸钠的混合物;在流动气氛中,400~790 ℃温度范围,NaNH4CrO48226;2H2O热分解产物为重铬酸钠.与传统的铬酸钠硫酸酸化生产重铬酸钠工艺相比,该方法无副产物产生,是一清洁工艺. 相似文献
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热分析法观测Na2CrO4熔点 总被引:2,自引:0,他引:2
在现有文献中收录的Na2CrO4熔点数据各不相同,有792℃、392℃,两者相差400℃左右。利用热分析法观测Na2CrO4熔点,确定其熔点应为792℃。并且在419.6℃存在着一个可逆的固-固相变,转变焓为148.6J.g^-1。 相似文献
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《化学通报》1976,(6)
铬盐是国防、冶金、电镀、医药、颜料和制革工业的重要原料,也是常用的化学试剂。它的生产直接影响到有关各个行业的生产。近年来,铬盐还广泛应用在催化剂的制造上。因此,铬盐生产在国民经济上占有十分重要的地位。随着我国工农业生产的飞跃发展,对铬盐的需要量也愈来愈多。但铬盐生产中排出大量含铬废矿渣、所含的六价铬是一种有毒物质,如不妥善处理,势必愈积愈多,污染水源与农田,影响人民身体健康,影响铬盐的扩大再生产。因此,铬矿渣的治理和综合利用问题是关系到发展工农业生产、巩固工农联盟、巩固无产阶级专政和保护人民身体健康、造福子孙后代的一件大事。解放后,特别是经过无产阶级文化大革命,我国各 相似文献
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铬酸镧(LaCrO3)材料具有良好的高温化学稳定性与物理稳定性,被认为是理想的高温电解制氢的连接体隔板材料,然而其高温下电导性能的主要影响因素仍有待研究。采用固相法合成掺杂CaCO3和B4C铬酸镧粉体,并研究了掺杂量对铬酸镧陶瓷的烧结性能、电阻率的影响。应用X射线衍射(XRD)、扫描电子显微镜(SEM)、四探针法和排水法分析了铬酸镧连接体的结构、微观形貌、晶相组成、电阻率以及密度。研究表明:加入CaCO3,B4C能够促进晶粒细化,但B4C的加入不利于铬酸镧陶瓷致密化烧结。加入CaCO3能降低材料电阻率,B4C的加入可能改变晶界电阻,从而对陶瓷的电阻率形成影响。CaCO3=20%,B4C=0.1%(摩尔分数)配比的铬酸镧作为连接体材料,高温下具有较低且稳定的电阻率。 相似文献
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本文特别延长了pH范围(2-10),详细研究pH、温度、外加正负离子对CrO4^2^-吸附量的影响,说明这种吸附主要是以离子交换方式进行的,并认为表面活性点是产生这类吸附的重要原因. 相似文献
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用X光衍射(XRD)方法研究了CrO_3/SiO_2和CrO_3/γ-Al_2O_3体系。用相定量外推法测定活性组份在载体表面的最大分散量。在干燥气氛中将CrO_3与载体混合, 并在低于CrO_3熔点的温度下烘烤制备样品, 实验得到CrO_3在SiO_2或者γ-Al_2O_3表面的最大分散量都随温度的升高而增大。CrO_3在SiO_2表面的最大分散量由101 ℃的0.27gCrO_3/g SiO_2到170 ℃的0.38g CrO_3/g SiO_2; CrO_3在γ-Al_2O_3表面的最大分散量由120 ℃的0.22g CrO_3/g γ-Al_2O_3到171 ℃的0.42g CrO_3/g γ-Al_2O_3。CrO_3在SiO_2或γ-Al_2O_3表面的最大分散量超过密置单层量, 可由易聚合形成同多酸根来解释。 相似文献
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利用物质在恒温相变过程中吸收或释放能量的特性,将暂时不用的能量储存起来,待需要时再加以利用,这类材料统称为相变储能材料,被广泛应用于空调节能、建筑节能、甚至空间技术等方面[1-5]. 相似文献
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In the present paper, Na_2SO_4-Al_2(SO_4)_3-H_2O system has been studied by ~(23)Na and ~(27)Al NMR quantitative method. It has been shown that the existence of double salt can be easily identified by this method. 相似文献
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Solid-stateSynthesisatLow-heatingTemperatureandCrystalStructureofaDinuclearMolybdenumComplexwithOxalateLigand[Bu_4N]_2[Mo_2O_2(... 相似文献
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Density functional theory was used at the B3LYP/6-311++G(d,p) level of theory to study the hydrates of 2NH3:H2SO4:nH2O for n = 0~4. Neutrals of the most stable clusters, when n = 0 and 1, spontaneously formed and were determined to be hydrogen-bonded molecular complexes of monomeric species. Double ions (clusters containing a NH4+ cation and a HSO4- anion) or even ternary ions (clusters with two NH4+ cations and one SO42- anion) spontaneously formed in the most stable clusters of 2NH3:H2SO4:nH2O (n = 2, 3, 4). The energetics of binding and incremental association was also calculated. Double ions are not energetically favorable until 2NH3:H2SO4:2H2O because of the about equal free energies for forming the neutral (the most stable) and double ion (the second stable) isomers. The free energy of incremental association from free H2O and 2NH3:H2SO4:nH2O has a maximum at n = 2 at room temperature with ΔG ≈ -2 kcal/mol. The comparison of incremental association energies between 2NH3:H2SO4:nH2O, NH3:H2SO4:nH2O and H2SO4:nH2O clusters revealed that NH3 plays an important role in the atmospheric particle nucleation. 相似文献
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本文用X射线衍射及差热分析等方法, 研究了BaO-B_2O_3-GeO_2(BaO≤50 mol%)三元系的室温截面相图。发现了一个新的三元化合物Ba_3B_6Ge_2O_(16)(3BaO·3B_2O_3·2GeO_2)。并且研究了BaB_2O_4-Ba_3B_6Ge_2O_(16), BaGeO_3-Ba_3B_6Ge_2O_(16), BaB_2O_4-BaGeO_3三个二元系相图。它们都是共晶体系, 共晶温度分别为937±3 ℃、879±3 ℃875±3 ℃; 共晶组分分别为(BaO)_(0.42)(B_2O_3)_(0.42)(GeO_2)_(0.16), (BaO)_(0.42)(B_2O_3)_(0.24)(GeO_2)_(0.34), (BaO)_(0.50)(B_2O_3)_(0.27)(GeO_2)_(0.23)。这三个二元系组成一个三元共晶体系, 其三元共晶温度为870±3 ℃, 共晶组分为(BaO)_(0.46)(B_2O_3)_(0.27)(GeO_2)_(0.27)。 相似文献
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Cis-dioxo-metal complex ( NH3CH2CH2NH2 ) 2.5 [ Mo0.5^(V)W0.5^(VI)O2 ( OC6H4O ) 2] 1 was obtained by the reaction of tetra-butyl ammonium hexamolybdotungstate with 1, 2-dihydroxybenzene in the mixed solvent of CH3OH, CH3CN and ethylenediamine,and characterized by X-ray diffraction, UV-vis and EPR analysis. Compared with its analogous complexes (NH3CH2CH2NH2)3[Mo^(V)O2(OC6H40)2] 2 and (NH3CH2CH2NH2)2[W^(VI)O2(OC6H4O)2] 3, the results show that tungsten(VI) is less active in redox than molybdenum (VI) and that the change of the valence induced by substitution of W(VI) for Mo(V) in EMO2(OC6H40)2]n- does not influence the coordination geometry of the complex anion in which the metal center exhibits distorted octahedral coordination with cis-dioxo catechol. The responses to EPR of complexes 1 and 2 are active but complex 3 is silent,and the UV-vis spectra exhibited by the three complexes are obvious different because of the different electronic configuration between the central Mo(V) and W(VI) ions in the complexes.It is noteworthy that complexes 1 and 2 have the similar EPR signal to flavoenzyme, suggesting that the three complexes have the same coordination geometry feature with the co-factor of flavoenzyme. 相似文献