An Alternative Chemical Route for the Synthesis and Thermal Stability of Chemically Enriched Hydroxyapatite

Hydroxyapatite (HAp: Ca₁₀(PO₄)₆(OH)₂) was synthesized by aqueous precipitation using CaCl₂ and Na₃PO₄ with NaOH added to ensure completion of the reaction at room temperature. The HAp powder prepared using stoichiometric amounts of NaOH was stable even at 1200°C, but the HAp prepared with sub-stoichiometric amounts of NaOH resulted in its transformation into β-tricalcium phosphate at 600°C. The reaction pH, X-ray diffraction, thermal analysis, scanning electron microscopy, Fourier transform infrared analyses and inductively coupled plasma-optical emission spectroscopy were used to characterize the phase purity, thermal stability, morphology, and chemical composition of the synthesized HAp powder.     

化学沉淀法制备纳米SiO2颗粒

二氧化硅以其优越的耐热隔热性能引起各个行业的广泛关注。以硅酸钠为硅源、氯化铵为沉淀剂、十六烷基三甲基溴化铵（CTAB）为分散剂,采用化学沉淀法合成二氧化硅纳米颗粒。采用TG-DSC测试分散剂CTAB的分解温度,并用傅里叶红外光谱、X射线以及扫描电镜对制备的二氧化硅粉末进行表征。结果表明,此方法制备的二氧化硅颗粒为无定形态纳米颗粒,平均粒径为80 nm。     

以硫酸镁为原料制备氧化镁晶须的工艺研究

以硫酸镁为原料、碳酸铵为沉淀剂,首先通过沉淀结晶反应制得三水碳酸镁等前驱体,再经过滤、干燥和煅烧工序制得氧化镁晶须。研究反应温度、反应物物质的量比、碳酸铵的滴加速率以及硫酸镁初始浓度对前驱体晶须生长及晶形的影响,采用XRD和SEM对前驱体和最终所得晶体进行表征。结果表明：反应温度、反应物物质的量比、碳酸铵的滴加速率以及硫酸镁初始浓度对三水碳酸镁的生长、形态及颗粒大小都有显著的影响,通过实验优化了最佳工艺条件。由此推测晶须的产生和生长机制是各个晶面按螺旋位错规律生长的液-液-固（L-L-S）机理。     

牛磺酸合成工艺的改进

乙醇胺酯化-磺化法制备牛磺酸工艺分为酯化反应和磺化反应两部分, 用亚硫酸铵代替亚硫酸钠作为磺化反应的原料, 在含氨气体存在下与2-氨基乙醇硫酸酯进行磺化反应, 得到的优化条件为:反应温度为98℃, 反应时间为12 h, 物料配比(n_亚硫酸铵:n_酯)为1.65, 分4批加料, 2-氨基乙醇硫酸酯的转化率可以达到76.43%。对磺化反应后的混合溶液的分离提纯进行研究。首先用化学沉淀法除去其中的无机盐(NH₄)₂SO₄, 滤出沉淀物硫酸盐后稍微加热母液, 生成的NH₃·H₂O分解放出的氨气用于磺化反应过程, 此过程的除盐率达到98%以上。采用溶剂结晶法对含有牛磺酸、未反应完的2-氨基乙醇硫酸酯和不到2%的滤液物系进行分离。用均匀实验设计法考察了结晶温度、结晶时间、降温速率和搅拌速率对牛磺酸结晶过程的影响, 并用软件对实验结果进行回归分析, 得到溶剂结晶较优的工艺条件为:结晶温度为13.9℃, 结晶时间为1 h, 搅拌速率为低速搅拌(350～450 r·min^-1), 降温速率为0.5℃·min^-1 。在此条件下, 牛磺酸的一次结晶率可达到67.94%, 纯度接近100%。     

前驱体结构对多环芳烃选择性开环Pt/Beta催化剂的影响

以海绵铂为原料合成出［Pt（NH₃）₆］Cl₄络合物,采用热重分析（TG）、扫描电镜-能谱（SEM-EDS）、紫外-可见分光光度计（UV-Vis）、质谱（MS）、X射线光电子能谱（XPS）等手段确定了［Pt（NH₃）₆］Cl₄的结构组成;以H₂PtCl₆、Pt（NH₃）₄Cl₂和［Pt（NH₃）₆］Cl₄为前驱体,采用等体积浸渍法制得Pt/Beta催化剂,采用X射线衍射（XRD）、X射线荧光光谱（XRF）、氨程序升温脱附（NH₃-TPD）、氢氧滴定（H₂-O₂）、透射电镜（TEM）、氢气程序升温脱附（H₂-TPD）等表征了Pt/Beta催化剂的物化性质,并考察了Pt/Beta催化剂的多环芳烃选择性开环性能。结果表明,［Pt（NH₃）₆］Cl₄络合物具有更高的“抗自还原”能力,可从前驱体结构上降低铂氨前驱体受热分解时的自还原现象。前驱体结构对铂纳米颗粒的几何尺寸及分布有较大影响,一方面络合物的价态显著影响前驱体与分子筛间的静电作用,进而影响铂纳米颗粒的落位与尺寸;另一方面络合物的空间结构影响前驱体在分子筛微孔中的分布,影响铂纳米颗粒的Ostwald熟化速率。前驱体结构可调变Pt/Beta催化剂的双功能匹配关系,显著影响Pt/Beta催化剂转化甲基萘的活性、稳定性,采用［Pt（NH₃）₆］Cl₄前驱体制备的Pt/Beta催化剂具有更优的活性及长周期稳定性。     

Influence of Synthesis Conditions on the Characteristics of Biphasic Calcium Phosphate Powders

Mixtures of hydroxyapatite (HAp) and tricalcium phosphate (TCP) powders with different Ca/P ratios were prepared by a wet chemical precipitation synthesis of calcium-deficient hydroxy apatite (CDHA) and subsequent calcination. The influence of precipitation method and calcination temperature on the chemical and physical properties of the resulting powders were evaluated. Different ratios between HAp and TCP were obtained by variation of the velocity of orthophosphoric acid addition into calcium hydroxide suspension. Slow addition (1 mL/min, S-powder) of H₃PO₄ into Ca(OH)₂ suspension lead to a higher amount of CO₃ groups substituting PO₄ in the apatite lattice compared to powders synthesized by fast addition (200 mL/min, F-powder). Consequently, the Ca/P molar ratio of S-powder (1.55) was higher than that of F-powder (1.52), leading to a higher amount of HAp in the resulting calcinated powders. Both powders show significant differences in their calcinations behavior. Whereas for F-powders a temperature of 750°C was adequate for a complete transformation of CDHA to TCP and HAp, 950°C were required for S-powders.     

Formation and Properties of Hydroxyapatite–Calcium Poly(vinyl phosphonate) Composites

Ceramic–polymer composites composed of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) and calcium poly(vinyl phosphonate) salt were prepared by warm-pressing powder mixtures of tetracalcium phosphate (Ca₄(PO₄)₂O, TetCP) and poly(vinyl phosphonic acid) (PVPA) at a weight ratio of 3.5:1. The effects of temperature (to 300°C), pressure (to 690 kpsi), or compaction time (to 1 h) on the extent of conversion were studied using X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy coupled with energy dispersive spectroscopy. The conversion of TetCP to HAp and formation of the calcium poly(vinyl phosphonate) salt was enhanced at higher temperature, pressure, and/or longer compaction time. Mechanical property determinations showed both the tensile strengths and elastic moduli continuously increase with increasing temperature, pressure, and compaction time. However, the glass transition temperature values of the composites were only minimally higher than that of the unreacted polymer.     

有机胺法分解氯化铵的工艺

采用有机胺法在无水条件下分解氯化铵制取氨气和氯化氢,对有机胺的筛选和氯化铵分解工艺进行系统研究,分别考察了释放氨气过程和释放氯化氢过程中各反应条件对反应的影响,通过对多种有机胺[三己胺、三(2-乙基已基)胺、三辛胺和三月桂胺]分解氯化铵的反应进行比较,筛选出最优有机胺用于实现对氨气和氯化氢的高效分离。实验表明:与其他有机胺相比,三己胺具有反应时间更短、氨气和氯化氢收率更高的优势。释氨过程中当三己胺与氯化铵以及异戊醇与氯化铵的摩尔比分别为1.4和6.84,氮气流量140mL/min时,在132℃下反应3.5h,氨气收率可达到97.5%;释氯化氢过程中当非极性有机溶剂十四烷与三己胺盐酸盐的摩尔比为11:1,氮气流量260mL/min时,在223℃下反应4.5h,氯化氢收率可达94.65%。     

低温选择性催化还原催化剂二氧化硫中毒及再生特性

采用液相共沉淀法制备Mn-Ce/TiO₂低温选择性催化还原催化剂,催化剂在120 ℃无二氧化硫条件下低温SCR活性高,NO转化率为92%。利用BET、SEM、TEM、XRD和XPS等技术对催化剂的二氧化硫中毒特性进行分析,结果表明,催化剂中毒是由于(NH₄)₂SO₃和(NH₄)₂SO₄在催化剂表面发生沉积,采用水洗、加热和还原气体保护加热等方式对催化剂进行再生实验,发现水洗对催化剂活性再生非常有效,特别是在水洗浸泡过程中采用超声波震荡。用离子色谱技术对水洗副产物进行分析,发现水洗液中主要离子为NO₃^-、SO₄^2--和NH₄^+。     

The characteristics of X1 type Y2SiO5:Tb phosphor particles prepared by high temperature spray pyrolysis

The X1 type Y₂SiO₅:Tb phosphor particles with high brightness were prepared by spray pyrolysis from spray solution with NH₄F flux material. The phosphor particles prepared by spray pyrolysis at high preparation temperature had spherical shape, fine size and dense morphology. The mean sizes of the phosphor particles prepared at 900 and 1650 °C were 1.3 and 0.9 μm. The emission spectrum of the phosphor particles prepared by spray pyrolysis at 1650^oC had the characteristics of X1 type Y₂SiO₅:Tb phosphor. The photoluminescence intensity of the phosphor particles directly prepared by spray pyrolysis from spray solution with 20 wt.% NH₄F flux of the product at temperature of 1650 °C was 127 and 184% of the X1 and X2 type Y₂SiO₅:Tb phosphor particles post-treated at 1100 and 1300 °C, respectively. The Y₂SiO₅:Tb phosphor particles prepared by spray pyrolysis at 1650 °C had X1 type crystal structure because of short residence time of particles inside hot wall reactor of 0.4 s.     

Obtaining CeO2–ZrO2 mixed oxides by coprecipitation: role of preparation conditions

The preparation of CeO₂–ZrO₂ mixed oxides preparation was studied by evaluating the influence of several conditions. Coprecipitation was taken as the standard method and the effects brought about by the cerium salt precursor ((NH₄)₂Ce(NO₃)₆ or Ce(NO₃)₃), the introduction of drying and aging steps as well as pH controlling upon precipitation were analyzed. The samples were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, infrared spectroscopy, oxygen storage capacity and surface area. The use of Ce(NO₃)₃ leads to the formation of c-CeO₂ and t-ZrO₂ mixed oxide whereas a solid solution is achieved by using (NH₄)₂Ce(NO₃)₆. It was observed that the cerium precursor is the most significant parameter of preparation procedure since it defines the crystalline phases and consequently the reducibility behavior of the CeO₂–ZrO₂ system.     

Kinetic Model for α–Tricalcium Phosphate Hydrolysis

A mechanistic model for the kinetics of hydrolysis of α-tricalcium phosphate (α–Ca₃(PO₄)₂ or α-TCP) to hydroxyapatite (Ca_{10− x} (HPO₄) _x (PO₄)_{6− x} (OH)_{2− x} or HAp) has been developed. The model is based on experimental hydrolysis rate data obtained using isothermal calorimetry. Analysis of the kinetic data according to the general kinetics models in terms of the fractional degree of reaction and time suggests the hydrolysis to be controlled by different rate-limiting mechanisms as reaction proceeds. Initially, the hydrolysis kinetics depend on the surface area of the anhydrous α-TCP. Subsequently, they change to a dependence on the rate of HAp product formation controlled by a nucleation and growth mechanism. The model predicts that HAp nuclei form at essentially one time and growth occurs in two dimensions, leading to a platelike morphology. The change in the reaction mechanism occurs at a fractional degree of hydrolysis, which does not change significantly with temperature in the range of 37°–56°C.     

两种制备方法下锌铈复合纳米材料的性能比较

以四水硫酸高铈和七水硫酸锌为原料,碳酸铵为沉淀剂,分别采用直接沉淀法和异相沉淀法合成纳米氧化锌/二氧化铈复合材料。采用XRD,FT-IR和UV-Vis对产物进行表征分析。XRD分析表明,在相同的原料配比下,异相沉淀法合成的复合纳米材料中,铈的含量大于直接沉淀法合成的材料;FT-IR分析表明,异相沉淀法中,由于氧化锌对二氧化铈的表面包覆,样品分散性增加;UV-Vis分析表明,两种方法合成的样品都具有优异的紫外吸收性能,只是波段不同：异相沉淀法合成的产品的紫外吸收侧重于UVA波段,而直接沉淀法合成的产品的紫外吸收侧重于UVC波段。另外水中分散性实验还表明,采用异相沉淀法合成的纳米材料分散性优于前者。     

硫酸锰室温固相球磨制备四氧化三锰

利用软锰矿吸收硫酸镁热解尾气二氧化硫制得硫酸锰,再与碳酸氢铵室温下固相球磨反应,制备出前躯体碳酸锰,经热分解获得四氧化三锰。分别考察了物料比、球磨时间、球料比等因素对硫酸锰转化率的影响,采用XRD对产物进行了分析。结果表明,在n（碳酸氢铵）∶n（硫酸锰）=3.5∶1、球磨时间为40 min、球料质量比为5∶1时,硫酸锰的转化率可达99.8%,将固相产物在1 000 ℃热解1 h后所制备的四氧化三锰纯度为99.9%。该工艺操作简单,产品纯度高,成本低,为硫酸锰制备四氧化三锰提供了新的途径。     

增稠剂对NH4Al(SO4)2·12H2O蓄放热性能的影响

利用电热恒温水槽、高低温交变试验箱搭建蓄放热实验平台,研究了9种增稠剂对NH₄Al(SO₄)₂·12H₂O蓄放热性能的影响,测试分析了NH₄Al(SO₄)₂·12H₂O改性后的循环稳定性能。结果表明,质量分数为2%的黄原胶、1%的瓜尔豆胶或1%的羟乙基纤维素均能较好改善NH₄Al(SO₄)₂·12H₂O的放热性能且对相变潜热的削弱程度不大,对应改性NH₄Al(SO₄)₂·12H₂O的主要参数变化为：熔点分别降低1.0℃、1.3℃、1.3℃,蓄热时长分别增加94%、35%、9%,蓄热相变平台分别增加125%、63%、5%,过冷度分别减小43%、45%、34%,结晶过程温度变化分别减小84%、87%、73%,放热时长分别增加27%、11%、50%,相变潜热分别减小5.8%、8.3%、4.1%。增稠剂对NH₄Al(SO₄)₂·12H₂O放热性能的改性效果会受到降解反应影响,而2%黄原胶的改性效果相对其他两种增稠剂较好,循环过程中改性材料的结晶过程温度始终保持在60℃以上。60次循环后,改性材料主要参数相比纯材料的变化为：熔点下降0.2℃,蓄热相变平台减小15%,蓄热时长增加13%,结晶过程温度变化减小87%,过冷度减小42%,放热时长增加36%,相变潜热减小1.6%。     

SCR脱硝中催化剂表面NH4HSO4生成及分解的原位红外研究

采用工业用V₂O₅-WO₃/TiO₂催化剂,基于傅里叶原位红外光谱(in situ FT-IR)技术考察了SCR脱硝过程中催化剂表面NH₄HSO₄的生成与分解特性。结果表明:在V₂O₅-WO₃/TiO₂催化剂表面ABS的生成可由催化剂V═O基团上Lewis酸上配位吸附活化态的NH₃在O₂环境中与SO₂反应生成,也可由SO₂与催化剂表面反应生成的吸附态金属硫酸盐中间物VOSO₄与气态NH₃直接反应生成;NO能通过与NH₄HSO₄中的NH₄⁺直接反应来降低NH₄HSO₄降解的温度窗口,促进其在催化剂表面的分解行为,NO的脱除与NH₄HSO₄的生成是相互抑制关系;NH₄HSO₄本身的负载量影响其分解与挥发行为。     

沉淀温度对Pd-Cu/凹凸棒土结构及其CO常温催化氧化性能的影响

以凹凸棒土(APT)为载体,NH3·H2O为沉淀剂,采用沉积-沉淀法制备Pd-Cu/APT催化剂。在连续流动微反装置上,考察不同沉淀温度对Pd-Cu/APT催化剂CO常温催化氧化性能的影响。利用N2物理吸附-脱附、XRD、FT-IR和H2-TPR等对Pd-Cu/APT催化剂进行表征。结果表明,不同沉淀温度制备的催化剂均含有Cu2Cl(OH)3和CuO两种形式的Cu物种,但与沉淀温度25℃和90℃制备的催化剂相比,沉淀温度70℃制备的催化剂具有更多的活性Cu2Cl(OH)3物种,这有利于Pd2+物种的再生,显著提高其CO常温催化氧化活性。     

长程TiO2纳米管阵列表面的超声清洗及其光催化性能

通过阳极氧化法在NH4F/乙二醇/H₂O的电解液中制备了长程TiO₂纳米管阵列。借助超声手段分别采用蒸馏水、丙酮和异丙醇作为超声介质清除了TiO₂纳米管阵列表面的集束,探讨其对TiO₂纳米管阵列光催化活性的影响。采用SEM、TG和XRD等对TiO₂纳米管阵列进行表征。结果表明,超声处理明显清除了纳米管阵列表面集束,超声介质对清洗过程有重要影响,丙酮相对于蒸馏水和异丙醇更适合作为超声介质,且超声超过30 min,纳米管阵列的光催化活性得到明显提高。     

硫酸盐熔融反应法从钛铁矿中提取钛的研究

以海南万宁的钛铁矿和硫酸铵为主要原料,通过熔融反应法使钛铁矿中的钛转化为易溶于稀酸的硫酸氧钛,用稀硫酸浸取,达到提高钛浸取率的目的。考察了硫酸铵加入量、焦硫酸钾加入量、反应温度、稀硫酸浸取浓度对钛浸取率的影响。实验结果表明：硫酸铵和焦硫酸钾的加入量、反应温度对钛浸取率的影响较大。提高钛浸取率的最佳条件为：m（钛铁矿）∶m（硫酸铵）∶m（焦硫酸钾）=1∶6∶0.5,反应温度为450 ℃,保温时间为30 min,稀硫酸浸取浓度为2.32 mol/L,在此条件下钛的浸取率达到96.82%。     

硫酸铵法硝酸磷肥生产高品质硫酸钙工艺研究

研究了昆阳磷矿的硝酸酸解液与硫酸铵反应制备硫酸钙的工艺条件,分别研究了硫酸铵用量、硫酸铵质量分数、温度、加料时间、反应时间对晶体大小和共晶磷含量的影响。确定了结晶过程适宜的工艺条件：硫酸铵用量为理论用量的110%、硫酸铵质量分数为30%、反应温度为90 ℃、加料时间为20 min、反应时间为2 h。在此工艺条件下得到磷质量分数为0.179%、氟质量分数为0.06%的半水和二水混合晶型的硫酸钙结晶,该硫酸钙具有晶体粗大整齐、过滤强度高的优点。