盐湖副产硫酸钙转化法制备高纯氧化钙

利用盐湖副产硫酸钙和碳酸氢铵溶液进行转化反应得到氧化钙的前驱体碳酸钙;然后,将其直接热解制备高纯氧化钙,分别考察物料配比、反应时间、反应温度等因素对硫酸钙转化率的影响,采用XRD和化学分析方法对产物进行分析,并对转化反应过程进行动力学分析。研究结果表明,在物料配比为1.3:1.0,反应时间为2.5 h,反应温度为50℃时,硫酸钙的转化率可达到99.6%,将固相产物在1 000℃热解1 h后所制备的氧化钙纯度为99.7%。转化反应过程符合收缩核模型,其的数学表达式为kt=1-(1-X)1/3,反应的表观活化能为43.4 kJ/mol,该模型表明转化反应过程受界面化学反应控制。     

室温固相化学法制备ZnO压敏电阻用纳米粉体及其压敏特性的研究

采用室温固相化学法,并通过对反应物摩尔配比、球磨时间、前驱物洗涤方式等因素的控制,合成了掺杂ZnO纳米粉体.借助XRD,TEM,粒度分布测试等手段,对粉体的组成、形貌和粒度进行了表征,探讨了反应条件对粉体性能的影响.结果表明,在反应物配比为1.10,球磨时间为30min,采用含量为3%的PEG-2000作为表面改性剂的条件下,制备了粒径为20nm左右、形状为球状的掺杂ZnO粉体.将制备的粉体通过成型,在1080℃制备了电位梯度为791.64V/mm、非线性系数为24.36、漏电流为43μA的压敏电阻.借助XRD,SEM,电性能测试等手段,对ZnO压敏陶瓷的组成、结构及压敏电阻的性能进行了表征,探讨了工艺参数对压敏电阻性能的影响及其机理.     

钾长石-硫酸钙-碳酸钙体系的热力学分析

为了利用焙烧法生产可溶性钾肥,对钾长石-硫酸钙-碳酸钙体系的热分解反应进行了热力学计算和实验研究.计算结果表明:在富氧化钙区域内,CaO-SiO2、CaO-Al2O3和SiO2-Al2O33个二元体系及CaO-SiO2-Al2O3三元体系的热分解固相反应将优先生成2CaO·SiO2、2CaO·Al2O3·SiO2,并且随着氧化钙组分的增加,反应产物最终向2CaO·SiO2和3CaO·Al2O3转化.根据这种趋势得出钾长石-硫酸钙-碳酸钙热分解体系最佳的物料(钾长石/硫酸钙/碳酸钙)摩尔配比为1∶1∶14,并对此进行了实验验证.     

采用液相球磨法由氧化铋制备次硝酸铋的工艺

针对传统次硝酸铋制备过程中产生污染环境的有毒气体二氧化氮及大量氨氮废水等问题,提出采用液相球磨转化法制备次硝酸铋新工艺,运用正交试验和单因素试验方法对氧化铋球磨转化制备次硝酸铋工艺进行研究。研究结果表明:各因素对转化率影响性由大至小的顺序为液固比、球料比、硝酸浓度、反应时间;氧化铋球磨转化制备次硝酸铋的最佳工艺条件如下:硝酸浓度为0.5 mol/L,液固比为15:1 m L/g,球料比为10:1(质量比),反应时间为1 h,在此最佳工艺条件下,氧化铋的平均转化率为90.71%。制备的次硝酸铋主要呈棒状形态分布。     

神经酸钙的合成及理化性质研究

以神经酸(顺-15-二十四碳烯酸)为原料,以乙醇和水的混合物为介质,在常压下直接与氧化钙反应合成神经酸钙,对产物的光谱性质和理化性质进行了表征.并对反应温度、反应时间、反应物料液/固比以及反应物料配比等因素对反应的影响及对产物中游离酸含量的影响进行了研究,优化了反应条件.在优化条件下,可得到产率和纯度均达90%以上的产物.     

固相法制备高纯超细氢氧化镁的工艺

以自制的六氨氯化镁为原料,采用常温固相法制备了高纯超细氢氧化镁。对固相法制备高纯超细氢氧化镁的工艺条件进行了研究,得到优化的制备工艺条件为:M gC l2.6NH3和M gC l2.6H2O摩尔比1∶1,球磨速度350 r/m in,球磨时间15 m in,球料比5∶1、充填率52%,磨介1份10 mm大球和2份6 mm小球。对制得的超细氢氧化镁进行化学组成分析,结果表明:氢氧化镁含量在99.7%左右,杂质含量低于0.3%。粒度分析表明产品平均粒径为158 nm,变异系数(CV)为0.194。     

机械化学方法降解活性翠兰KN-G

以活性翠兰KN-G探针反应,用自制的NiO为磨料,考察了球磨时间、物料比、球料比和球磨速率对机械化学效应降解染料的影响,结果表明,最佳球磨条件为:转速500 r/min,物料比15,球料比18,球磨15 h,其CODcr去除率可达95%左右.对样品脱色率、CODcr去除率、XRD、红外光谱等的分析表明机械化学方法可以使活性翠兰KN-G有效降解.     

固液反应球磨制备Al-Cu-Co三元金属间化合物

利用固液反应球磨技术制备了Al-Cu-Co三元合金．分别采用Co球球磨Al-33．2％Cu(此文中的百分比为质量分数),Al-54％Cu(A12Cu)和Al-70％Cu(A1QJ)二元合金熔体,在923K和973K球磨Al-33．2％Cu熔体12h后生成Al65Co15Cu20粉末;在923K和1023K球磨24h后生成Al69Co25Cu6粉末,在893K和993K分别球磨Al-54％Cu(A12Cu)合金熔体12h和24h后均生成Al65Co15Cu2n粉末;在1123K球磨Al-70％Cu合金熔体24h后生成Al65Co15Cu20粉末．采用Al-Cu-Co固液反应球磨得到的金属间化合物粉末为纳米粒子．同时,对Al-Cu-Co三元合金相形成的规律进行了研究,对固液反应球磨机理进行了探讨．在固液反应球磨过程中,三元合金产物的元素摩尔比接近于二元母合金中的元素摩尔比;三元合金产物成分中固相第三组元的成分含量与二元母合金熔体成分有很大关系;提高反应球磨温度、延长球磨时间有利于三元合金产物的形成;延长球磨时间,形成的三元合金产物中磨球的成分增加;反应球磨温度超出二元母合金熔点越高,球磨反应越容易进行．     

机械球磨固相化学反应制备AlH_3

以LiAlH4和AlCl3为原料,采用机械球磨固相化学反应方法合成铝氢化合物,通过XRD、TG-DSC和MS等方法对反应产物进行分析和表征,研究不同球磨时间对球磨反应体系合成产物的转变规律和对产物热力学性能的影响.结果表明,随着球磨时间的增加,合成反应按3LiAlH4 AlCl3→4AlH3 3LiCl方向进行并形成了非晶态铝氢化合物(AlH3),球磨20 h时反应基本完全.球磨产物的放氢失重温度主要集中在100～200 ℃,对应的DSC曲线在135 ℃和165 ℃出现2个放热峰,随球磨时间的增加,失重量减少,最大失重质量分数达到3.5%～6.1%.球磨过程中形成的反应产物LiCl*H2O及少量AlH3发生分解是影响球磨反应产物最大失重量的主要因素.     

一步室温固相化学反应法合成CuO纳米粉体

研究了以CuSO4·5H2 O ,CuCl2 ·2H2 O ,Cu(NO3) 2 ·3H2 O ,Cu(gly) 2 ·H2 O与NaOH为反应物 ,用一步室温固相化学反应合成CuO纳米粉体的 4个反应体系 ,用透射电镜 (TEM)和X射线衍射 (XRD)对产物进行表征 .表明产物CuO(Ⅱ )化合物与NaOH经室温固相化学反应得到单斜晶纳米CuO .另还从研磨方式、反应配比及反应体系等方面对影响产物粒径大小及分散性的因素进行了探讨     

The structural basis of calcium transport by the calcium pump

The sarcoplasmic reticulum Ca2+-ATPase, a P-type ATPase, has a critical role in muscle function and metabolism. Here we present functional studies and three new crystal structures of the rabbit skeletal muscle Ca2+-ATPase, representing the phosphoenzyme intermediates associated with Ca2+ binding, Ca2+ translocation and dephosphorylation, that are based on complexes with a functional ATP analogue, beryllium fluoride and aluminium fluoride, respectively. The structures complete the cycle of nucleotide binding and cation transport of Ca2+-ATPase. Phosphorylation of the enzyme triggers the onset of a conformational change that leads to the opening of a luminal exit pathway defined by the transmembrane segments M1 through M6, which represent the canonical membrane domain of P-type pumps. Ca2+ release is promoted by translocation of the M4 helix, exposing Glu 309, Glu 771 and Asn 796 to the lumen. The mechanism explains how P-type ATPases are able to form the steep electrochemical gradients required for key functions in eukaryotic cells.     

Three types of neuronal calcium channel with different calcium agonist sensitivity

How many types of calcium channels exist in neurones? This question is fundamental to understanding how calcium entry contributes to diverse neuronal functions such as transmitter release, neurite extension, spike initiation and rhythmic firing. There is considerable evidence for the presence of more than one type of Ca conductance in neurones and other cells. However, little is known about single-channel properties of diverse neuronal Ca channels, or their responsiveness to dihydropyridines, compounds widely used as labels in Ca channel purification. Here we report evidence for the coexistence of three types of Ca channel in sensory neurones of the chick dorsal root ganglion. In addition to a large conductance channel that contributes long-lasting current at strong depolarizations (L), and a relatively tiny conductance that underlies a transient current activated at weak depolarizations (T), we find a third type of unitary activity (N) that is neither T nor L. N-type Ca channels require strongly negative potentials for complete removal of inactivation (unlike L) and strong depolarizations for activation (unlike T). The dihydropyridine Ca agonist Bay K 8644 strongly increases the opening probability of L-, but not T- or N-type channels.     

Structural changes in the calcium pump accompanying the dissociation of calcium

In skeletal muscle, calcium ions are transported (pumped) against a concentration gradient from the cytoplasm into the sarcoplasmic reticulum, an intracellular organelle. This causes muscle cells to relax after cytosolic calcium increases during excitation. The Ca(2+) ATPase that carries out this pumping is a representative P-type ion-transporting ATPase. Here we describe the structure of this ion pump at 3.1 A resolution in a Ca(2+)-free (E2) state, and compare it with that determined previously for the Ca(2+)-bound (E1Ca(2+)) state. The structure of the enzyme stabilized by thapsigargin, a potent inhibitor, shows large conformation differences from that in E1Ca(2+). Three cytoplasmic domains gather to form a single headpiece, and six of the ten transmembrane helices exhibit large-scale rearrangements. These rearrangements ensure the release of calcium ions into the lumen of sarcoplasmic reticulum and, on the cytoplasmic side, create a pathway for entry of new calcium ions.     

氢氧化钙和碳酸钙混合物的分析方法

在甲醇存在下,用EDTA四钠盐能准确而精密地络合滴定Ca(OH)2和CaCO3混合物.当甲醇与水的体积比在0.2～0.6之间时,CaCO3 对Ca(OH)2的滴定不干扰,且能准确滴定Ca(OH)2.本法可用来监测石灰乳碳化的全过程.     

Depletion of intracellular calcium stores activates a calcium current in mast cells.

In many cell types, receptor-mediated Ca2+ release from internal stores is followed by Ca2+ influx across the plasma membrane. The sustained entry of Ca2+ is thought to result partly from the depletion of intracellular Ca2+ pools. Most investigations have characterized Ca2+ influx indirectly by measuring Ca(2+)-activated currents or using Fura-2 quenching by Mn2+, which in some cells enters the cells by the same influx pathway. But only a few studies have investigated this Ca2+ entry pathway more directly. We have combined patch-clamp and Fura-2 measurements to monitor membrane currents in mast cells under conditions where intracellular Ca2+ stores were emptied by either inositol 1,4,5-trisphosphate, ionomycin, or excess of the Ca2+ chelator EGTA. The depletion of Ca2+ pools by these independent mechanisms commonly induced activation of a sustained calcium inward current that was highly selective for Ca2+ ions over Ba2+, Sr2+ and Mn2+. This Ca2+ current, which we term ICRAC (calcium release-activated calcium), is not voltage-activated and shows a characteristic inward rectification. It may be the mechanism by which electrically nonexcitable cells maintain raised intracellular Ca2+ concentrations and replenish their empty Ca2+ stores after receptor stimulation.     

电石渣制备纳米晶碳酸钙的液相法工艺研究

文章研究了以氯化铵为提取液,利用液相法从电石渣中提取钙的工艺条件,并利用提取的钙与碳酸铵反应,成功制备出了纳米碳酸钙;从降低生产成本与提高产品质量出发,设计了一个二级循环浸取工艺,从而成功实现了氯化铵在整个制备过程中的循环利用,并达到环保的目的;该工艺中钙的提取率可达91.43%,产品碳酸钙的纯度与白度分别为99.93%与98,符合国家标准;X射线粉末衍射(XRD)结果表明,产物为纯净的方解石型碳酸钙;透射电子显微镜(TEM)显示产物的粒径为30 nm左右。     

天门冬氨酸钙和葡萄糖酸钙兔体内吸收度的研究

用原子吸收分光光度法测定兔血清钙浓度,结果表明,天门冬氨酸钙和葡萄糖酸钙的吸收度无显著性差异。     

过氧化钙合成工艺的研究

研究了在氢氧化钙-氯化铵-双氧水法常温下制备过氧化钙的工艺条件中，反应温度、反应时间、稳定剂用量、氢氧化钙过量数、双氧水的浓度及氯化铵用量对过氧化氢利用率的影响．     

稀土尾矿中钙的提取及硫酸钙晶须的制备

本研究采用稀硫酸溶解稀土尾矿,稀土尾矿中难溶的稀土矿物和钙的溶解产物硫酸钙存在于硫酸不溶物中,固液分离后用稀盐酸进一步溶解硫酸不溶物,使固态的硫酸钙溶解在稀盐酸中.尾矿中的稀土富集于盐酸不溶物中,盐酸不溶物中稀土氧化物质量分数为43.60％.采用乙醇结晶的方法制备硫酸钙晶须,确定结晶制备的最佳条件为:室温下,硫酸钙的初始浓度为0.009 mol/L左右,pH为1.0～1.5,溶液与乙醇的体积比为1:2,静置时间为2h.在此最佳条件下,稀土尾矿中钙的回收率大于85％,产品硫酸钙晶须纯度达98％以上,晶须平均直径为1 μm,平均长径比达80.